2.0: Nutrition

NUTRITION

Nutrition is the process by which an organism takes in and uses nutrients

FOOD NUTRIENTS

Are substances which organisms use for the body processes

CATEGORIES OF FOOD NUTRIENTS

There are two main types of food nutrients, namely:

1. Macronutrients

2. Micronutrients

1. MACRONUTRIENTS

Are nutrients needed in large amounts.

Example of macronutrients

i. Proteins

ii. Carbohydrates

iii. Lipids

2. MICRONUTRIENTS

Are nutrients needed only in small amounts.

Example of micronutrients

i. Vitamins

ii. Minerals

IMPORTANCE OF NUTRITION IN LIVING THINGS

1. Nutrients are required for growth and development of cells, tissue and organs.

2. Nutrients are required by the body to replace, repair worn out and damaged tissues.

3. Nutrients are required to protect the body against infections and diseases.

4. Nutrients are required for contraction and relaxation of muscles.

5. Nutrients are needed in electrical transmission of nerve impulses

6. Nutrients are requiredfor reproduction.

7. Nutrients are needed for the maintenance of relatively constant body temperature.

TYPES OF NUTRITION

There are two types of nutrition, namely:

1. Autotrophic nutrition

2. Heterotrophic nutrition

1. AUTOTROPHIC NUTRITION

Is a type of nutrition whereby organisms manufacture their own food from simple inorganic substance such as caarbondioxide and water.

AUTOTROPHS

Are organisms that able to manufacture their own foods.

Autotrophs manufacture food by using either light energy (photosynthesis) or chemical energy (chemosynthesis).

Examples of autotrophs are:  green plants

2. HETEROTROPHIC NUTRITION (heterotrophism)

Is the mode of nutrition whereby organisms feed on already manufactured food.

HETEROTROPHS
Are organisms that feed on already manufactured food. E.g. animals

TYPES OF HETEROTROPHIC NUTRITION

There are three types of heterotrophic nutrition

i. Saprophytic nutrition

ii. Holozoic nutrition

iii. Symbiosis (symbiotic nutrition)

I. SAPROPHYTIC NUTRITION

Is the mode of nutrition whereby organisms feed on dead or decaying organic matters.

Organisms feeding by this way are known as SAPROPHYTE

Example of saprophytes includes: fungi and bacteria.

II. HOLOZOIC NUTRITION

Is mode of nutrition which involves taking in of complex food substances, digesting the food and assimilating the nutrients.

III. MODE/FORMS OF HOLOZOIC NUTRITION

Holozoic nutrition is divided into three modes/forms namely:

a. Herbivorous mode of feeding

b. Carnivorous mode of feeding

c. Omnivorous mode of feeding

A. HERBIVOROUS

Is a mode of feeding whereby an animal feeds on  plants.

Animals that feed on plants are called herbivores.

Examples are cow, goat, rabbit, antelope and zebra

B. CARNIVOROUS

Is a mode of feeding whereby an animal feeds on flesh other animals.

Animals that undergo this type of feeding are called carnivores.

Examples are lion, tiger, hawk, leopards etc

C. OMNIVOROUS

Is a mode of feeding whereby an organism feeds on both plants and animals.

Animals that feed on both plants and animals are called Omnivores

Examples are man, monkey, pig.

D. SYMBIOSIS

Is a close relationship between two species.

Forms of symbiosis

1. Mutualism

2. Commensalism

3. Parasitism.

1. MUTUALISM

Is a relationship which occurs when both species benefit from the relationship.

2. COMMENSALISM

Is a relationship in which one species benefits while the other is unaffected by the relationship.

3. PARASITISM

Is a relationship where one species benefits while the other is harmed.

NUTRITION IN MAMMALS

FOOD

Is a substance that provides the body with energy, materials for growth, repair and factors for good health.

Types and functions of food substances

The following are types of food substances that are needed by the human body for its proper functioning.

1. Proteins

2. Carbohydrates

3. Lipids

4. Vitamins

5. Minerals

6. Roughage

7. Water

1. PROTEINS

Are compounds of the elements carbon, hydrogen, oxygen, nitrogen and sometimes sulphur and phosphorus. OR are large complex organic compound made of amino acids.

AMINO ACIDS

Are small building units of protein

SOURCE OF PROTEINS

Foods such as

• Meat

• Liver

• Eggs

• Beans

• Soya beans

• Chicken

• Fish

• Milk

• Cheese

• Peas

• Groundnuts

• Mushrooms

PROPERTIES OF PROTEIN

1. Proteins dissolve in water but do not form true solutions.

2. Proteins are denatured by high temperature

3. Proteins are affected by pH

4. Proteins are amphoteric meaning they react with both acid and bases.

FUNCTION OF PROTEINS

The following are the function of protein (i) Proteins are used as a source of energy.

1. Proteins are used in body building.

2. Proteins are used for tissue growth and repair.

3. Some proteins form antibodies which provide defense against diseases.

4. Some proteins form haemoglobin that enables red blood cells to transport oxygen in the body.

5. Some proteins are used as metabolic regulators. E.g. enzymes and hormones.

6. Proteins are used to form part of the cell structures such as the plasma membrane.

2. CARBOHYDRATES

Are compounds which contain elements carbon, hydrogen and oxygen.

NB: Carbohydrates are referred to as the energy- giving food.

SOURCESES OF CARBOHYADRATES

The following are some of the food that contains nutrients of carbohydrates:

•     Maize

•     Rice

•     Wheat (Bread and cake)

•     Cassava

•     Yams

•     Potatoes

•     Bananas etc

FUNCTIONS OF CARBOHYDRATES

1. Used as a source of energy in the body.

2. Some carbohydrates provide dietary fibre e.g. Cellulose.

3. They form important component of cell membrane.

4. Some, such as glycogen and starch , form the energy stored in organisms

Types of carbohydrates

Carbohydrates divided into three groups namely:

a) Monosaccharides

b) Disaccharides

c) Polysaccharides

A) MONOSACCHARIDES

Are the simplest forms of carbohydrates with a chemical formula of C6 H12 O6

Examples of Monosaccharides

1. Glucose– Occurs freely in grapes, honey, tomato and germinating maize

2. Fructose– Occurs freely in all ripe sweet fruits E.g. banana, pineapple

3. Galactose– It is found in mammalian milk

Characteristics of monosaccharides
1. They are sweet.

2. They dissolve in water to form sweet solution.

3. They are crystalline.

4. They are all reducing  sugar.

B) DISACCHARIDES

Are carbohydrates formed when two monosaccharides linked by the process of condensation.

Condensation is the process

– Disaccharides are also known as non – reducing sugars.

– Their general formula is C11 H22 O11.

– Sources of Non- reducing sugar are: sugar cane, fresh milk, beet root.etc

Examples of disaccharides include:

Characteristics of disaccharides
(i) They are soluble in water.

(ii) They are sweet.

(iii) They are crystalline.

(iv) They dissolve in water to form sweet solution.

(v) Some are reducing sugars e.g. maltose and lactose

(vi) Some are non-reducing sugars e.g. sucrose).

C) POLYSACCHARIDES

These are formed when many monosaccharides combine.

Example of polysaccharides

Starch (stored form of carbohydrates in  plants)

Sources of Starch are: Cassava, potatoes, yams, cereals.etc

Glycogen (stored form of carbohydrates in animals.

Cellulose (component of the cell wall in plants).

Characteristics of polysaccharides

i) They are not sweet.

ii) They are insoluble in water.

iii) They are non-crystalline.

iv) They form suspensions with water

v) All are non-reducing sugars.

LIPIDS

Are compounds of carbon, hydrogen and oxygen.

i. They are insoluble in water.

ii. Lipids are made up of smaller units known as fatty acids and glycerol.

iii. Fatty acids can be essential or non- essential.

iv. Three molecules of fatty acids combine with one molecule of glycerol to form fats.

MAIN FORMS OF DIETARY LIPIDS

There are two main forms of dietary lipids, namely:

1. Fats: are obtained from animals and are solid at room temperature.

2. Oils: are obtained from plants and are liquid at room temperature.

NB: Oils are storage materials in some seed such as maize grain and coconut.

SOURCES OF LIPIDS

Foods such as

i. Fish

ii. Sunflower

iii. Nuts

iv. Coconuts

v. Seed oils

vi. Avocados and olives.

PROPERTIES OF LIPIDS

1. Lipids are insoluble in water.

2. They are inert meaning they are inactive hence stored in tissues of living organisms.

3. Lipids form suspensions and emulsions when mixed with alcohol

4. Fats melt at high temperature while oils solidify at low temperature

FUNCTIONS OF LIPIDS

1. Lipids are used as a source of energy

2. Lipids protect delicate organs such as heart and kidneys.

3. Lipids are used as heat insulators. E.g. adipose tissue deposited below the skin.

4. Lipids are used as source of metabolic water.

5. Lipids form part of structures such as the plasma membrane.

VITAMINS

Are complex organic micronutrients that are essential for growth and survival.

OR Are organic compounds that are required by organisms in small amounts to maintain normal health.

Lack of vitamins in the body leads to deficiency diseases.

CATEGORIES OF VITAMINS

Vitamins can be grouped into two categories, namely:-

1. Fat-soluble vitamins

2. Water-soluble vitamins

1. FAT-SOLUBLE VITAMINS

Are vitamins that can be stored in the body and need not be consumed daily.

Examples are: Vitamins A, O, E and K

2. WATER-SOLUBLE VITAMINS

Are  vitamins that are not stored in the body and should be consumed daily.

Examples are:

i. Vitamins B and C are water soluble.

ii. Vitamin B is of various forms, namely Vitamin B1, B2, B6 and B12.

The table below shows vitamins, their sources, functions and signs of deficiency.

MINERALS

Are inorganic compounds containing elements which are vital for the proper functioning of the body. Minerals are grouped into two namely, macro-minerals and micro-minerals.

Macro-minerals

Are minerals required in large quantities

Example includes nitrogen, oxygen, phosphorous, potassium, calcium, magnesium and carbon.

Micro-minerals

Are minerals that are required in small quantities.

Example includes copper, zinc, manganese and boron.

NB: Micro-minerals are also known as trace elements.

The following are example of minerals, their sources and their functions in the body.

a) Macro minerals

b) Micro minerals

ROUGHAGE

Is dietary fiber that is obtained from indigestive part of  plants.

Roughage does not have any nutritional value as it is not digested and absorbed in the body.

Mammals do not produce any enzyme which can digest cellulose instead they have microorganism which secrete the enzyme cellulose that digests cellulose.

In human beings there are no such microorganisms hence no digestion of cellulose.

SOURCE OF ROUGHAGE

1. Whole grown cereals

2. Spinach

3. Fruits

4. Cassava

5. Beans

6. Whole baked potatoes.

7. Cabbage

FUNCTION OF ROUGHAGE

1. Roughage promotes peristalsis

2. Roughage prevents constipation

3. Roughage helps in the passage of food and faces through the gut by aiding contraction of the gut muscles.

4. Roughage adds to the bulk of food.

WATER

Is a compound of hydrogen and oxygen and forms about 90% of the cell.

Water acts as a medium for many biochemical reactions in living cells.

FUNCTION OF WATER

1. It used in the digestion and absorption of food.

2. It is a medium of transport for food and hormones.

3. It helps to regulate body temperature.

4. It is a medium in which digestion takes place.

5. It acts as lubricants e.g. eyeball eyelids.

6. It helps in excretion of harmful by product of metabolic process e.g. urine, sweat.

7. It is used in the manufacture of different secretions e.g. tears, saliva.

FOOD TEST

Is a biochemical experiment carried out in order to identify the food substance present in a given food sample.

Or is a process used to determine which nutrients are present in a food specimen.

COMMON REAGENTS AND CHEMICALS USED TO DETERMINE FOOD PROPERTIES

The following are common reagents and chemicals used to determine food properties

1. Iodine solution –used to tests starch

2. Sudan III-used to test lipid

3. Benedict’s solution –used to test reducing and non-reducing sugars

4. Dilute hydrochloric acid-used to test non-reducing sugar

5. Sodium hydroxide-used to test protein and non-reducing sugar

6. Copper sulphate solution-used to test protein

7. Millon’s reagents-used to test protein

Common food to be determined or tested

i) Starch

ii) Lipid

iii) Protein

iv) Reducing sugar

v) Non-reducing sugar

The table below shows common food substances, their common reagents and colour to be observed

FUNCTION OF THE FOLLOWING REAGENTS DURING TESTING NON-REDUCING SUGAR

1. Dilute hydrochloric acid

— used to break down non-reducing sugars to reducing sugars

2. Sodium hydroxide

— used to neutralize the acid

EXAMPLE OF FOOD TEST PRACTICAL REPORT

EXPERIMENT NO.1 2A NECTA 2016

You have been provided with solution Z.

Perform experiments using the reagents provided identify the type of food substance(s) present in solution Z.

Tabulate your results as shown in table 1

Table 1

i) Name two sources of food from which food substances identified in

(a) could have been extracted.

ii) For each food substances identified in

(a), give the name of the end product of digestion in human being.

iii. Why is it important to use iodine solution in this experiment?

iv. What will happen in human body when the end products named in i (ii) are in excess

EXPERIMENT NO. 2

Materials:

Specimen A-glucose        

Specimen D- Cooking fat

Specimen B- Fruit juice      

Specimen E- starch powder

Specimen C- egg albumen

Carry out the following food test on each specimen

i. Test for reducing sugar, non-reducing sugar, starch ,  proteins and lipids

ii. Make your observations and conclusions and write them in your notebook

iii. Discuss your observations and conclusions with your group members.

DIET

Is the food an animal eats everyday

A BALANCE DIET

Is a diet that contains all types of nutrients in the correct proportions.

IMPORTANCE OF BALANCE DIET

i)     It prevents diseases and infections.

ii) It helps to control weight

iii) It promotes healthy body growth

iv) It helps to promote mental health

v) It helps the body to grow and maintain proper functioning

COMPONENTS OF BALANCE DIET

• Proteins

• Carbohydrates

• Vitamins

• Minerals

• Lipids

• Roughage

• Water

NB: Human beings are advised to eat a diet low in fats,  sugar and salt.

But also human beings are advised to eat a diet high in proteins, carbohydrates, vitamins, minerals, and roughage,

More importantly should take in large amounts of water

NUTRITIONAL REQUIREMENTS FOR DIFFERENT GROUPS OF PEOPLE

Different people have different nutritional requirements.

Nutritional requirements depend on factors such as

1. Body size

2. Age

3. Sex

4. State of health

5. Occupation

The followings are different groups of people with different nutritional requirements.

NB: Spina bifida is a spinal disorder characterized by a hole in the spine. ¬ It results from incomplete formation of the spinal cord and the bones of spine..

It is advisable to use food guide pyramid to know what to eat.

THE FOOD GUIDE PYRAMID

Is a chart showing the recommended amounts of different food types that dietician considered as healthy eating.

THE DIAGRAM OF FOOD GUIDE PRYMID

NUTRITIONAL DEFICIENCIES AND DISORDERS

Malnutrition

Is a condition which occurs when the body lacks proper nutrition.

OR is limited intake of one or more essential nutrients results from eating too little, too much or wrong foods.

Causes of malnutrition

1. Wrong amount of food: too little or too much

2. Incorrect proportion of main nutrients

3. Lacking in one or more key nutrients

Symptoms of malnutrition

• Lack of appetite

• Tiredness

• Inability to concentrate

• Always feeling unhappy

• Longer healing time for wounds

• Depression

• Dry skin and mouth.

Effects of malnutrition

• Mental health problem

• Low intake of food

• Social and mobility problem ∙     Digestive disorders ∙     Lack of breast feeding.

Types of nutritional deficiencies and disorders in human beings
These include:

i) Anorexia nervosa

ii) Bulimia nervosa.

iii) Kwashiorkor

iv) Obesity

v) Rickets

vi) Marasmus

NUTRITIONAL DEFICIENCIES

These deficiencies arise when the body does not have sufficient supply of a particular food or nutrient.

The following are common nutritional deficiencies:

1) KWASHIORKOR

Is a form of malnutrition disorder caused by a deficiency of  proteins.

Kwashiorkor mostly affects children between six months and five years age.

Signs and symptoms of kwashiorkor

i) The signs and symptoms of kwashiorkor include:

ii) Protruding stomach.

iii) Extremely thin arms and legs.

iv) Poor growth

v) Swollen abdomen due to enlargement of the liver

vi) Reddish or yellowish thin and weak hair.

vii) Weakened immunity

viii) Diarrhea

ix) Anaemia

x) Dry skin that cracks easily

xi) Loss appetite

Effects

1. Weaken body immunity that makes a child prone to diseases like malaria and diarrhea

2. Poor growth of child

3. The child becomes anaemic and weak.

Prevention and control of kwashiorkor

Providing a child with a diet that has adequate amounts of proteins.

MARASMUS

Is a form of malnutrition in children caused by lack of enough food in the body.

Sign and symptoms of marasmus

1. Loss of weight

2. Stunted growth

3. General body weakness.

4. Dry and wrinkled skin

5. The child feels hungry all the time

6. Diarrhoea

7. Weak muscles.

Treatment of Marasmus

Getting adequate amount of food that contains all the nutrients in the right proportions.

RICKETS

Is a condition where by the bones of a child softens, leading to fractures and deformity.

The cause of rickets is lack of  vitamin D, phosphorous and calcium.

Sign and symptoms of Rickets

• Skeletal deformities such as bow legs, knock knees, an odd – shaped skull and a deformed spine.

• A child feels bone pain

• A child experiences dental problems such as weak teeth, delayed formation of teeth and develops weak muscles.

• Bones are easily fractured.

• Slow growth

• A child experiences muscle spasms and muscle cramps.

Prevention of rickets

• Rickets is prevented by increasing the amount of vitamin D, phosphates and calcium in diet.

• Ensuring exposure to sufficient amounts of sunlight.

NUTRITIONAL DISORDERS

Are conditions of ill health in a person which arise as a result of life style (poor eating habits).

The following are nutritional disorders :

OBESITY

Obesity is where by a person has excess body fat.

Obesity is caused by too much intake of fats and lack of physical exercise.

Body Mass Index (BMI)

Is the value obtained when the body mass divided by the square of the body height.

BMI is calculated by using the following formula and expressed in units of kg/m2

BMI = Body mass (in kilograms) Person’s height (in meters)2

Example. What will be your BM your BMI , if your height is 1.65 meters and your body mass is 60 kilograms Given

Body weight= 60𝑘𝑔 ∙ Height = 1.65𝑚

BMI =?

From

BMI= 𝐵𝑜𝑑𝑦
𝑚𝑎𝑠𝑠
=     𝐻𝑒𝑖𝑔ℎ𝑡     1.

BMI = 𝟔𝟎    = 22.03𝑘𝑔/𝑚2

2.𝟕𝟐𝟑

∴
𝐁𝐌𝐈 = 𝟐𝟐. 𝟎𝟑𝐤𝐠/𝐦𝟐

• If an individual’s BMI range 20-25, an individual is considered to be healthy.

• If an individual’s BMI is over 30, an individual is at risk of diseases associated with obesity.

The following table shows a general guide of how different values of BMI are used to define the condition of the body.

Table BMI guide

Question: if Dina is 70kg and 150cm tall.

i) What is her BMI? ii) What dangers are facing Dina?

iii)     What advise will you give Dina and why?

Effects of obesity

1. Obesity increases the likehood of conditions such as

2. high blood pressure

3. diabetes

4. Certain types of cancer

5. stroke, and respiratory problems

Control measures of obesity
Obesity can be prevented by:

1. Avoid eating too much fatty foods such as butter, fat meat, chips etc.
2. Eating properly and engage in regular exercise.

3. The intake of calories should balance one’s physical activit

4. Avoid also unhealthy dieting.

ANOREXIA NERVOSA AND BULIMIA NERVOSA

Anorexia nervosa
is also called slimmer’s disease or self starvation syndrome.

It occurs when a person intentionally refuses to eat enough, leading to a severe loss of body mass.

Sign and symptoms of anorexia

• Muscle wasting (including weakening of heart muscle) ∙ Excessive loss of body mass ∙ Extreme fear of being fat.

• Anxiety over body mass and shape.

• Weak heartbeat

Bulimia nervosa

involves excessive eating followed by efforts to remove food from the body.

This effort could involve self- induced vomiting, fasting, excessive exercising or taking drugs that stimulate, emptying of the bowels or excessive urination.

Causes of Anorexia and Bulimia

Both Bulimia and Anorexia have underlined psychological causes, such as depression, low self esteem and bottled up emotions and the need to fit contemporary standard of beauty Bulimia and Anorexia mostly affect women.

Effects of Anorexia and Bulimia

1. Heart problems due to weak cardiac muscles or an imbalance of mineral salts.

2. Causes impaired mental function because the brain lacks adequate amount of glucose.

3. Dehydration.

4. Causes, serious damage to the gum and erosion of the teeth when the acidic present in the stomach come into contact with the teeth and gums during vomiting.

5. Anaemia

6. Stomach ulcers

7. Abdominal cramping and inflammation of the gut

8. Irregular or absent menstrual periods and dry skin.

Treatment for Anorexia and Bulimia

i. Anorexia and Bulimia can be treated by:

ii. Resolving the underlying psychological problems.

Seeing a medical practitioner who can prescribe a way of getting back one’s healthy and making the necessary lifestyle and dietary change.

DIGESTIVE SYSTEM IN HUMAN

COMMON TERMS

DIGESTION

Is the process by which food is broken down mechanically and chemically to smaller particles which are absorbed and assimilated in the body.

OR Is a process by which food is broken down into form that can be absorbed and used by the body.

Types of digestion

There are two types of digestion, namely:

1. Mechanical digestion

2. Chemical digestion

MECHANICAL DIGESTION

Is the breakdown of food into smaller pieces without chemical change to the food molecules.

1. It takes place in the mouth

2. It is performed by the teeth by the process called chewing

Role of mechanical digestion

1. To reduce large food pieces into small pieces that can be swallowed easily

2. To breakdown large food pieces into small pieces to increases the surface area of the food for the action of digestive juice called enzymes

CHEMICAL DIGESTION

Is the breakdown of large insoluble molecules into small soluble molecules.

Chemical digestions is achieved by  digestive enzymes

ABSORPTION

Is the process by which soluble end products of digestion diffuse into the blood stream.

ASSIMILATION

Is the process by which the body uses up the absorbed products of digestion.

INGESTION

Is the taking in of food through the mouth.

EGESTION

Is the removal of undigested food from the alimentary canal through anus.

It is also called defecation.

PERISTALSIS

Is the wavelike muscular contraction that pushes food along the oesophagus. Or is the movement of food in wave like motion along the alimentary canal.

QN: Why it is possible for a person to swallow food while standing upside down?

ANS: Because     

1. Swallowing cannot be affected by gravitational force.

2. Swallowing can be facilitated by peristalsis.

ENZYMES

Are biological catalysts that speed up the rate of chemical reaction but remains unchanged at the end of reaction.

Types of enzymes

i. Intercellular enzymes

ii. Extracellular enzymes

i)     INTECELLULAR ENZYMES

Are enzymes secreted and used within the cells which produce them.

Example: Respiratory enzymes.

ii)     EXTACELLULAR ENZYMES

Are enzymes secreted within the cells but used outside the cells that produce them.

Example:  Digestive enzymes

PROPERTIES OF ENZYMES

i) Enzymes are protein in nature.

ii) Enzymes are specific

iii) Enzymes remain unchanged at the end of the reaction

iv) Enzymes work rapidly

v) Enzymes become denatured at high temperature

vi) Enzymes are sensitive to change in pH

vii) Enzymes can catalyze reactions in both directions

IMPORTANCE OF ENZYMES

i)  To speed up cellular reactions.

THE HUMAN DIGESTIVE SYSTEM AND THEIR ADAPTIVE FEATURES

The human digestive system: Refers to the human alimentary canal (gut) and the organs and glands associated with it.

The digestive system is made up of alimentary canal (gut) and associated organs such as the pancreas andliver

Function of digestive system

The digestive system has two main functions:

i) Digestion

ii) Absorption

ALIMENTARY CANAL

Is a muscular tube running from mouth to the anus

OR is a long hollow tube that runs from the mouth to the anus    It is also known as digestive tract or gut.

THE MAIN PARTS OF ALIMENTARY CANAL

i) Mouth

ii) Pharynx

iii) Oesophagus

iv) Stomach

v)  Small intestine (duodenum and ileum)

vi)  Large intestine (colon)

vii) Rectum

THE DIAGRAM OF HUMAN DIGESTIVE SYSTEM

ADAPTATIONS OF STOMACH TO ITS MODE OF FUNCTION

i) Stomach has sphincter muscles to prevent food from flowing back into the oesophagus

ii) Stomach has gastric glands, which produce gastric juice for the digestive process.

iii) Also in the stomach of a young baby there is rennin which coagulates milk.

iv) Stomachs have mucus which protects it from corrosion by digestive enzymes.

v) There is hydrochloric acid for the emulsification of fats and killing of bacteria

THE DIGESTIVE SYSTEM AND DIGESTION PROCESS

The major regions where digestion occurs in the alimentary canal are:

• Mouth

• Duodenum

• Stomach

• Ileum

DIGESTION IN THE MOUTH

Food in the mouth is mechanically and chemically broken down.

MOUTH CONTAIN THE FOLLOWING

i) Teeth

iii) Tongue

ii) Saliva

i)     TEETH

These break down food mechanically during chewing and grinding.

Chewing reduces food into small pieces that can be swallowed easily

The small pieces have a large surface area to facilitate the action of digestive juice called enzymes

Chemical breakdown is achieved by  digestive enzymes.

There different types of teeth in human being

1. Incisors – Used for cutting

2. Cannes-used for tearing food

3. Premolar-grinding and cutting

4. Molar-for crushing and grinding food

These teeth follow the human dental formula of i𝟐 , c𝟏, pm𝟐, m𝟑=32

𝟐    𝟏    𝟐    𝟑

ii) SALIVA

Is a mixture of mucus, water, salts and salivary amylase enzyme or ptyalin.

The presence of food in the mouth stimulates the salivary gland to produce more saliva.

Saliva is alkaline in nature, so it makes the food alkaline when in the mouth.

Components of saliva

Saliva consists the following components:

i) Salivary amylase (ptyalin)– an enzyme that convert starch into maltose

ii) Water – to moisten the food and provide a medium for the action of enzymes.

iii) Sodium and calcium salts– to ensure an alkaline pH suitable for the functioning of amylase.

iv) Mucus– to lubricates the food and make it easier to chew and swallow

FUNCTION OF SALIVA

i)   Water acts as solvent for dissolving food substance

ii) Mucus lubricates the food for easy swallowing.

iii) Salivary amylase converts starch to maltose.

iv) Salts to ensure alkaline condition for the functioning of amylase.

iii) THE TONGUE

Roles of tongue

i) It helps to turn the food during chewing.

ii) It helps to rolls the food into a bolus after chewing

iii) It helps to push a bolus into the esophagus

THE PHARYNX

In this region there is no secretion of digestive enzymes

In the pharynx there are openings into both oesophagus and the trachea

Most of time the opening to the oesophagus is closed off by epiglottis.

Function of epiglottis

1. To prevents food and water from entering the trachea.

THE ESOPHAGUS (GULLET)

Is a muscular tube that conveys food boluses from the pharynx to the stomach.

The boluses move down the oesophagus by a process known as peristalsis

The walls of oesophugus have circular and longitudinal muscle.

During swallowing, circular muscles contract and longitudinal muscles relax to push the bolus downwards.

The boluses enter the stomach through a muscle valve known as cardiac sphincter

Cardiac sphincter:
is a valve between the eosophagus and the stomach.

In this region there is no secretion of digestive enzymes.

DIGESTION IN THE STOMACH

Stomach: is a highly elastic muscular organ that can stretch to accommodate about two liters of food and drinks.

The stomach has muscles which contract and relax producing movement that mixes the contents of the stomach.

CHURNING: Is the mixing of food substance with the gastric juice in the stomach as the result of contraction and relaxation of the stomach muscles.

CHYME: is a semi-solid mass produced when food in the stomach mix with hydrochloric acid and gastric juice.

Or is a semi-liquid substance produced as a result of mixing of food in the stomach. The stomach walls contain gastric glands which secrete gastric juice.

Components of gastric juice

The gastric juices contain the following components:

i. Hydrochloric acid

ii) Mucus

iii) Water

iv) Enzymes (pepsin and rennin).

i) HYDROCHLORIC ACID

Function of the hydrochloric acid

Provides suitable acidic medium for enzymes to work best. ii) Hydrolyses or breaks down complex sugars to simple sugars. iii) Used to activates pepsinogen to pepsin iv) Kills bacteria present in food

ii. MUCUS

Function of mucus

i) To protect the stomach walls against corrosion by the  digestive enzymes and hydrochloric acid.

iii) Enzymes

The gastric juice contain two enzymes, namely

a) Pepsin

b) Rennin

a) PEPSIN

Pepsin is an enzyme produced in an inactive form known as pepsinogen

Function of pepsin

i) Converts protein into peptides.

PEPSINOGEN

Is an inactive form of pepsin.

Qn: explain why pepsin is produced in its inactive form in the stomach?

Ans:

To prevents it from digesting the walls of alimentary canal.

To prevents it from digesting the cells that produce it in the gastric gland.

b) RENNIN: This enzyme is only produced in young mammals during sucking period.

Function of rennin

i) To coagulates milk

GENERAL FUNCTIONS OF THE STOMACH

1. It is a temporary storage of food

2. It is a first site of protein digestion in the digestive system.

3. The stomach wall absorbs vitamins, water and drugs such as alcohol.

4. Helps in mixing food during churning.

NB: Pyloric sphincter: is a muscle valve between the stomach and the duodenum.

Function of pyloric sphincter

To allows small quantities of chyme to enter the duodenum at a time
A DIAGRAM OF HUMAN STOMACH

DIGESTION IN THE DUODENUM

THE DUODENUM

Is the first part of the small intestine.

Duodenum is a site where digestions of fats begin.

When chyme enters the duodenum, it stimulates the pancrease to produce pancreatic juice.

Enzymes in the duodenum work most efficiently in alkaline medium.

Duodenum is associated with liver and pancreas.

THE ROLE PLAYED BY LIVER, GALL BLADDER, BILE DUCT AND PANCREASE IN DIGESTION

BILE

Is a yellow greenish which contains bile salts.

Components of bile

i. Sodium salts

ii. Potassium salts

FUNCTION OF THE BILE

i)  Bile salts neutralize the acidic chyme from the stomach.

ii) Bile provides alkaline medium for enzymes to work best in the duodenum

iii) Bile emulsifies (break down) fats into tiny fat droplets to reduce their surface tension.

Emulsification

is the process of breaking down of fat into droplets.

Biological significance of emulsification is to increase surface area for the action of digestive enzymes.

THE PANCREASE

The pancreas secretes digestive juices known as pancreatic juice.

COMPONENTS OF THE PANCREATIC JUICE

i. Pancreatic amylase – Breaks down the remaining starch into maltose.

ii. Pancreatic lipase – Digest the fat droplets into fatty acids and glycerol.

iii. Trypsin – Break down the remaining proteins into peptides.

iv. Sodium hydrogen carbonates (NaHCO3) -provides basic medium for pancreatic enzymes to work best

–     
-Neutralize the acidic chyme from the stomach.

DIGESTION IN THE ILEUM (SMALL INTESTINE)

THE ILEUM

Is the second part of the small intestine.

It is a longest section in the alimentary canal.

Digestion is completed in the ileum.

The intestinal walls contain secretory cells which secrete mucus and intestinal juice.

THE TWO MAIN FUNCTION OF ILEUM

1. Digestion of carbohydrates, proteins and lipids

2. Absorption of end products of digestion into the blood stream

ADAPTATION OF THE ILEUM FOR DIGESTION

i)     It has secretory glands, which produce digestive enzymes

ii) It is highly coiled to increase surface area for digestion

iii) The ileum has mucus secreting glands to ensure a constant supply of mucus.

ADAPTATIONS OF THE ILEUM FOR ABSORPTION

1. It has villi to increase the surface area for absorption of food.

2. The ileum is very long to increase the surface area for absorption.

3. The inner lining of the ileum is folded to increase the surface area for absorption.

4. It is highly coiled to increase the surface area for absorption.

5. It has villi with dense network of blood capillaries for easy diffusion of digested materials

VILLUS

Is a finger like projections found in the walls of the ileum, important for absorption process.

Function of villus

i)     To increase the surface are for absorption of food.

A STRUCTURE OF VILLI

Adaptations of the villus to its functions

i) Villus is very thin, to reduce the diffusion distance of food.

ii) Villus has numerous microvilli to increase the surface area for absorption of food.

iii) Villus is provided with a network of blood capillaries to transport away the absorbed food.

iv) Villus is provided with lacteals to absorb fatty acids and glycerol.

v) Villus has goblet cells for secretion of mucus

QUESTION

Explain how villus and alveolus are said to be similar and different

ANSWERS: Similarities between villus and alveolus

i) Both are used in absorption process

Differences between villus and alveolus

THE CAECUM AND THE APPENDIX

These have no function in man.

In herbivores the caecum and appendix contain bacteria that secrete an enzyme known as cellulase.

The cellulase digests cellulose to glucose.

THE LARGE INTESTINE (COLON)

There is no any digestive enzyme in this part of the alimentary canal.

Function of colon

i) Helps in absorption of water from the undigested materials

ii) It has bacteria that synthesizes vitamins B1 ,B2, B12 and K

iii) Helps to pass out undigested and indigestible materials into the rectum

RECTUM

Is the last chamber of the alimentary canal

Function of rectum

i) Used as a temporary storage of faeces

SUMMARY OF DIGESTION IN THE HUMAN DIGESTIVE SYSTEM

END PRODUCTS OF DIGESTION

i. Amino acids – the end product of proteins.

ii. Glucose – end product of carbohydrates

THE RUMINANT DIGESTIVE SYSTEM

A ruminant: is an animal that chews food, swallows it then returns it to the mouth later for further chewing.

Examples of ruminants are cows, goats, sheep, antelopes and giraffes.

Chewing cud: is the process whereby ruminants chews food, swallows it then returns it to the mouth later for further chewing

Chewing cud softens and helps break down plant fibres, making them more access to digestion by the bacteria.

Chewing cud is also known as rumination

NB: The digestive system of a ruminant is different from that of a human being.

Ruminants have a more elaborate system to enable cellulose digestion.

The stomach of a ruminant has four chambers namely

i) Rumen

ii) Reticulum

iii) Omasum

iv) Abomasums

RUMEN

Is the first chamber of the ruminant stomach

Function of rumen

1. Act as a site for temporary storage of food when a ruminant first chews and swallows a mouthful of plant matter.

2. It contains bacteria that secrete cellulase enzyme which digest cellulose to glucose.

RETICULUM

Is the second chamber of the ruminant stomach

Reticulum has a honeycomb appearance

Function of reticulum

i) To mix the food thoroughly with water.

OMASUM

Is the third chamber of the ruminant stomach which receives regurgitated and chewed again food from the reticulum.

The omasum has broad and longitudinal folds like the leaves of a book.

Function of omasum

i)  Have folds help to remove water from the food.

NB: The food in the omasum is in form of fine particles and has very little water.

ABOMASUM

Is the ruminant’s true stomach.

Function of abomasum

1. Has gastric acid that facilitates the digestion of proteins.

2. It kills microorganisms that may have spilled over the rumen.

DIFFERENCES BETWEEN THE RUMINANT DIGESTIVE SYSTEM AND THE HUMAN DIGESTIVE
SYSTEM

COMMON DISEASES AND DISORDERS OF THE HUMAN DIGESTIVE SYSTEM

These include diseases and disorders that affect teeth, the oesphagus, the stomach and the small and large intestines. Common diseases and disorders associated with the human digestive system include:

i) Dental caries

ii) Heartburn

iii) Stomach ulcers

iv) Constipation

v) Flatulence

vi) Cancer.

vii) Indigestion- refers to pain or discomfort which occurs after eating too much oily, spicy food

I. HEARTBURN

Is a burning or painful sensation in the oesopgaus caused by regurgitation of the stomach contents.

Causes of heartburn

Heartburn is caused by excess acid in the stomach.

Signs and symptoms of heartburn

1. A sour taste in the mouth

2. A burning feeling in the chest or throat

3. Excessive belching

4. Loss of voice or hoarseness

5. Difficulty swallowing.

Effects of heartburn

1. An individual with this problem feels uncomfortable all the time

2. Prolonged heart burn can lead to esophagus cancer and ulcers

Prevention and treatment of heartburn

1. Avoid food that cause heartburn

2. Avoid alcohol, caffeine, tobacco and recreational drugs.

3. Take measures to reduce stress

4. Antacids help to reduce acidity.

5. Obese people should lose weight

6. Drink water to dilute acid in the stomach.

II. ULCERS

These are sores or broken parts of the digestive system

OR is a wound in the stomach or small intestine which is caused by too much acid in the digestive tract.

Types of ulcers

1. Peptic ulcers: are ulcers found in the stomach.

2. Duodenal ulcers: are ulcers found in the duodenum

A STOMACH ULCER

Is a sore in the stomach lining caused by the erosion of the stomach’s mucus coating, exposing the stomach to the action of digestive enzymes and acid.

Cause of ulcers

1. Excessive secretion of acid and pepsin in the stomach

2. Ulcers can also be caused by stress which stimulates production of acid.

3. Keeping the stomach empty for longtime.

4. Drugs like aspirin

5. Smoking

Smoking increases production of HCl acid and pepsin which erodes the stomach walls

6. Alcohol

Alcohol cause ulcers, it breaks down stomach’s mucus coating and exposing the stomach walls to HCl acids.

Bacteria called Helicobacter pylori break down the mucus coating and expose the stomach wall to the action of digestive enzymes and acid

Excessive intake of acidic foods like beans because they irritate stomach ulcers

Sign and symptoms of ulcers

1. Burning pain in stomach or the middle of thorax

2. Nausea and vomiting

3. Tiredness and weakness

4. Blood in vomiting or stool (a symptom of breeding ulcer)

Prevention and treatment of stomach ulcers

1. Ulcers can be controlled as follows ∙     Avoid smoking

2. Avoid taking alcohol

3. Avoid acid producing food

4. Avoid emotional stress

5. To take flesh milk

6. Use antibiotics to kill infectious bacteria that cause ulcers.

III. CONSTIPATION

Is a decrease in the frequency of formation or passage of stool.

It occurs when the stool become dry and hard due to excessive absorption of water in the colon.

Causes of constipation

1. Inadequate amount of fibre in the diet.

2. Inadequate intake of water

3. Lack of exercise

4. Ignoring the urge to go for a long call

5. Life style changes such as pregnancy and old age

6. Abusive of laxatives

7. Excessive absorption of water in the colon

Sign and symptoms of constipation

1. Lack of bowel movements for three or more days.

2. Hard stools that is difficult or painful to pass.

3. The urges to go for a long call even after you have just gone.

Prevention and control of constipation
1. Eat enough fibre.

2. Drink a plenty of water every day.

3. Exercise regularly

4. Go for long call when you feel the urge to.

5. Seek medical help if constipation is persistent

IV. FLATULENCE

Is a condition caused by excessive gas in the digestive tract.

Causes of flatulence

• Swallowed air or eating food that produce gas such as beans, cabbage, onions

• Eating meals that have too much fat which leads to production of large amount of carbondioxide ∙     Poor absorption of carbohydrates in the gut

Signs and symptoms of flatulence

• Abdominal pain

• The constant urge to pass wind

• Excessive belching

• Bloating (an accumulating of gas in the stomach)

Prevention and control of flatulence

• Avoid foods that produce gas or eat them in moderation.

• Avoid lying down after eating because it easy for gas to pass from the stomach into the intestines

• Chew food carefully to assist in proper digestion of carbohydrates.

• Limit the amount of lipids in the diet.

V.     DENTAL CARIES

This is commonly referred to as tooth decay.

• It occurs when bacteria destroy the outer part of the tooth.

NB: Plaque is the sticky substance often found between teeth.

It is formed when bacteria in the mouth combine with acid, saliva and remains of food.

• The bacteria in plaque convert the remains of food (especially sugar and starch) into acids.

• The acid dissolves the enamel in the tooth, forming a cavity If this cavity is left untreated, it reaches the pulp cavity and nerve endings inside the tooth causing an infection.

Sign and symptoms of dental caries

• Toothache, especially after eating sweet, cold or hot foods

• Holes in the teeth

Prevention and control measures of dental caries

• Minimize intake of sugary foods

• Avoid eating very hot or very cold foods

• Brushing teeth and floss frequently in order to remove plaque

• Damaged teeth can be filled or covered with an artificial crown or pulled out

• Visit a dentist regularly for dental check-ups.

NUTRITION IN PLANTS

Plant are autotrophs, means they manufacture their own food.

Although plants can manufacture their own food but they need chemical elements for them to stay health.

MINERAL REQUIREMENTS IN PLANTS
MINERAL ELEMENTS

Are chemical elements that the plants obtain from the soil.

Mineral elements are found in the soil in form of ions dissolved in water.

TYPES OF MINERAL ELEMENTS REQUIRED BY PLANTS

The mineral elements required by plants are grouped into two types, namely;

i) Macro elements

ii) Microelements

I)  MACRO ELEMENTS

Are mineral elements that required by the plants in large quantities.

Example of macroelents

• Carbon

• Sulphur

• Magnesium

• Potassium

• Calcium

• Nitrogen.

• Phosphorus

II)     MICRO ELEMENTS

Are mineral elements required by the plants in small quantities.

• They are also called trace elements

Example of microelements

• Manganese

• Copper

• Zinc

• Cobalt

• Sodium

• Silicon

• Boron

• Molybdenum

• Chlorine

THE ROLE OF MINERAL ELEMENTS IN PLANTS

MACROELEMENTS

MICROELEMENTS

PHOTOSYNTHESIS: Is the process by which green plants manufacture their own food from water and carbondioxide in the presence of sunlight.

BALANCED CHEMICAL EQUATION OF PHOTOSYTHESIS

Sunlight

6CO2 + 6H2O

C6H1206 + 6O2
Carbon Water Chlorophyll Glucose Oxygen dioxide

REQUIREMENTS AND CONDITIONS NECESSARY FOR PHOTOSYNTHESIS

RAW MATERIALS NECESSARY FOR PHOTOSYNTHESIS

There are two raw materials necessary for photosynthesis:

i) Water

ii) Carbon dioxide

CONDITIONS NECESSARY FO PHOTOSYNTHESIS

There are two conditions necessary for photosynthesis:

i) Chlorophyll

ii) Sunlight

REQUIREMENTS NECESSARY FOR PHOTOSYNTHESIS

There are four requirements necessary for photosynthesis process to occur:

i) Water

ii) Carbon dioxide

iii) Chlorophyll

iv) Sunlight

Roles played by each Requirement necessary for photosynthesis

END PRODUCTS OF PHOTOSYNTHESIS

1. Glucose – is used in respiration to release energy. Some is stored as starch or oils during exchange.

2. Oxygen – Some oxygen is used during respiration while the rest is released into the atmosphere during exchange.

3. Water – some water is used in various chemical reactions within the cells, some water is released to the atmosphere during transpiration.

IMPORTANCE OF PHOTOSYNTHESIS

1. Food production. Through photosynthesis food such as glucose is manufactured by plants and used by both plants and animals.

2. Energy conversion. Through photosynthesis light energy is converted into chemical energy

3. Balance atmospheric gases such as carbondioxide and oxygen.

4. Photosynthesis is a source of fuels such as fossil fuels from the remains of dead plants

FACTORS AFFECTING THE RATE OF PHOTOSYNTHESIS PROCESS

1. LIGHT INTENSITY

A good quality of light enhances the rate of photosynthesis. Very bright light damages the plant due to strong sun rays. Plants under shade receive poor quality of light

2. CARBONDIOXIDE CONCENTRATION

An increase in carbon dioxide concentration results to an increase in the rate of photosynthesis up to a certain level. Any further increase in the carbon dioxide concentration after the maximum point induce the stomata to close and therefore cutoff the supply of carbon dioxide.

3. TEMPERATURE

The rate of photosynthesis increase as the temperature increase up to maximum point i.e. 400c.

4. WATER

Plants require water for the various chemical reactions of the cells.

Water is also a raw material for photosynthesis.

5. MINERAL SALTS

Some minerals such as magnesium and iron are responsible in the formation of chlorophyll.

The availability of these minerals results in the chlorophyll synthesis and the rate of photosynthesis increases.

6. LEAF AGE

As the leaf ages chlorophyll breaks down hence the rate of photosynthesis is reduced.

7. PRESENCE OF MANUFACTURED CARBOHYDRATES

This will reduce the rate of photosynthesis since carbohydrates are product of photosynthesis

THE PROCESS OF PHOTOSYNTHESIS

Photosynthesis takes place in two stages namely:

a) Light stage

b) Dark stage

a) THE LIGHT STAGE

It takes place in the grana of the chloroplast

It needs light to take place

Grana contain chlorophyll

Light energy causes photolysis

Photolysis

Is the process of splitting water molecules into oxygen and hydrogen ions using light energy.

Photolysis is represented by the following reaction

Light energy

H2O  2H+ +O2-

Hydrogen enters the dark reactions

b) THE DARK STAGE

• It takes place in the stroma

• It does not need light

• Hydrogen from the light stage combines with carbondioxide to form glucose

• This process is called carbon dioxide fixation

CARBONDIOXIDE FIXATION

Is the process in which hydrogen from the light stage combines with carbondioxide to form glucose.

THE STRUCTURE OF THE LEAF IN RELATION TO PHOTOSYNTHESIS

LEAF

Is the plant organ which acts as a site where photosynthesis process occurs.

The structure of the leaf contains;

i) Internal structure

ii) External structure

NB: The internal and external structures of a leaf make a leaf well adapted for photosynthesis.

EXTERNAL STRUCTURE OF A LEAF

Are the external features of the leaf that can be viewed by using a hand lens or unaided eyes. These include:

DIAGRAM SHOWING THE EXTERNAL STRUCTURE OF A LEAF

INTERNAL STRUCTURE OF THE LEAF

Are the internal features of the leaf that can be viewed by using a microscope The following are internal parts of the leaf:

i) Cuticle

ii) Spongy mesophyll layer

iii) Epidermis

iv) Leaf veins

v) Guard cell

vi) Chloroplast

vii) Palisade layer

DIAGRAM SHOWING THE INTERNAL PARTS OF A LEAF

FUNCTION OF THE INTERNAL STRUCTURE OF LEAF

1) CUTICLE

Is the outermost transparent layer of the leaf.

It is thin, waxy, and transparent and water proof.

Functions

Protects the leaf from injury, pests and excessive water loss ii) It allows light to penetrate to the photosynthetic cells.

2) EPIDERMIS

It is the outermost layer of cells found both on the lower and upper surfaces of a leaf.

It is transparent and only one cell thick layer

Functions

It allows sunlight to penetrate the leaf. ii) Secretes (makes) the cuticle iii) Protects inner tissue from damage

NB: Epidermis has pores called stomata

STOMATA (singular: stoma)

Are small pores which allow gaseous exchange into and out of the leaf.

Function

i) To allow oxygen and carbondioxide to diffuse into and out of the leaf

3) GUARD CELLS

Are bean shaped epidermal cells mostly found on the lower surface.

Contain chloroplasts with chlorophyll used to trap sunlight for photosynthesis.

Functions

Control opening and closing of stomata ii) Control water loss

PALISADE MESOPHYLL LAYER

Is the layer found between the upper epidermis and the spongy mesophyll layer

It is made up of palisade cells which contain chloroplasts

It is a part of a leaf which has abundant chlorophyll to maximize light absorption and photosynthesis.

Functions

i) To trap sunlight by using chlorophyll for the process of photosynthesis

SPONGY MESOPHYLL LAYER

Is the layer found between the palisade layer and the lower epidermis

This layer has very few chloroplasts as compared to palisade layer

Function

i)     It is a part of a leaf with cells loosely parked to maximize gaseous exchange.

ii) Photosynthesis takes place in it

5) LEAF VEINS OR VASCULAR BUNDLE

Consist of both xylem tissues in the upper part and phloem tissues on the lower surface

Functions of leaf veins

1. Xylem transport water and mineral salts from the root to the rest parts of the plants.

2. Phloem transport manufactured food from the leaves to the rest parts of the plant.

CHLOROPLAST

Is a disc- shaped organelle that contains chlorophyll

Chloroplasts is the main site where photosynthesis takes place which are mostly found in the leaf

Functions:

i)     It contains chlorophyll to trap sunlight for photosynthesis

THE STRUCTURE OF THE CHLOROPLAST

Chloroplast has the following structures:

1. Double membrane i.e. outer membrane and inner membrane

2. Chlorophyll (photosynthetic pigment) – to traps sunlight for the process of photosynthesis.

3. Stroma (aqueous matrix)-is a fluid medium which contains photosynthetic enzymes and it is a site where dark stage of photosynthesis takes place.

4. The grana-contain chlorophyll pigments which trap sunlight and it is a site where light stage of photosynthesis takes place.

Diagram of a chloroplast

ADAPTATION OF THE LEAF IN THE PROCESS OF PHOTOSYNTHESIS

1. The leaf has cuticle and epidermis which are transparent to allow easy penetration of light

2. Presence of stomata on the leaf allows easy diffusion of carbon dioxide

3. The leaf has network of veins which allows movement of materials in and out of the leaf

4. The leaf has air spaces in the spongy mesophyll layer allow gases to circulate easily.

5. Presence of large numbers of chloroplasts in the palisade layer enables maximum sunlight absorption.

6. The leaves are well arranged to avoid overlapping and overshadowing

7. The leaf has broad and flat lamina to allows maximum absorption of sunlight and carbondioxide

STORAGE ORGANS

Plants store food for future use. Foods in plants can be stored in:

1. Leaves e.g. Onions, cabbage

2. Fruits e.g. Mango, pineapple, pawpaw

3. Seeds e.g. Beans, peas, rice, maize

4. Stems e.g. Irish potato, ginger, sugar cane

5. Roots e.g. Sweet potato, cassava, carrots

ADVANTAGE OF FOOD STORAGE ORGANS

(i) Some organs give rise to new plants e.g. Seeds, stem, tubes

(ii) Permits the survival of plants over dry seasons.

(iii) Some are used as source of food by man and other animals e.g. Rice, wheat, potatoes etc.

(iv) The stored food is used during germination before the leaves form.

(v) Some are used for commercial purpose by man e.g. Sugar cane

FOOD PROCESSING, PRESERVING AND STORAGE

FOOD PROCESSING

Are ways in which food is treated in order to make it edible, appetizing and safe to eat or keep it fresh for a long time.

Some of the activities involved in food processing are:

1. Picking, sorting and washing fruits and vegetables

2. Converting raw materials into other products

Example making cheers from milk or sugar from sugar cane

FOOD PROCESSING TECHNIQUES

Common food processing techniques include

1. Removing unwanted outer layers e.g. peeling potato

2. Chopping or slicing e.g. Bananas, mangoes and cassava

3. Liquefaction e.g. producing juice by squeezing fruits

4. Fermentation e.g. making wine from banana and grapes and beer brewing

5. Cooking e.g. boiling, frying, steaming or grilling

6. Deep freezing

7. Baking

FOOD PRESERVING

Are methods that are used to prevent food from getting spoiled or going bad.

OR is the process of adding preservatives such as salts, sugars to the food to prevent deterioration.

PRESERVATIVES

Are chemicals that stop deterioration of food or prevent growth and development of microorganisms.

FOOD STORAGE

Is a method used to keep reserves of food for future use

IMPORTANCE OF FOOD PROCESSING, PRESERVING AND STORAGE

1. Prevents wastage of food

2. Saves money by preventing spoilage of food

3. Maintains the quality of food.

4. Prevents growth of microorganisms that can cause illness

5. Helps to improve the flavour of food.

6. Removes harmful toxins and microorganisms from food

7. Makes food available even when they are not in season

8. Enables transportation of delicate and perishable food such as milk and fruits over long distance

METHODS OF FOOD PROCESSING AND PRESERVING

Methods of processing and preserving food are grouped into two main categories, namely:

a. Traditional methods

b. Modern methods

(a) TRADITIONAL METHODS OF FOOD PROCESSING AND PRESERVING

1. CURING

This involves the addition of substances such as sugar, salt, spices and vinegar to animal foods to remove water making it unsuitable for the growth of microorganism ∙      It also improves the taste of food.

This method is used to preserve food such as meat and fish

2. DRYING IN THE SUN

This involves the removal of water from the food by using solar energy to discourage the growth of microorganism.

This method is used to preserve rice, maize, cloves, bananas, beans, meat, fish, cassava and green vegetables.

3. SMOKING

This involves drying food by using smoke to reduce the moisture content of food to prevent the growth of microorganisms.

This method is used to preserve cassava, grains, meat and fish

4. SALTING

This involves the addition of salt to remove water from the food and kills microorganisms that might spoil the food.

This method is used to preserve meat, sardines and fish

5. COOKING

This includes boiling, steaming, baking in hot ash, grilling and roasting.

– These processes help to soften food, improve flavor and preserve food.

Examples: potatoes, banana, and maize can be boiled before being dried. Meat can be grilled or deep fried.

6. FERMENTATION

Is the conversion of carbohydrates such as sugars into acids or alcohol

– Fermentation can occur naturally or can be induced.

– It is used to preserve milk in form of yoghurt

ADVANTAGE OF TRADITIONAL METHODS OF FOOD PROCESSING, PRESERVATION STORAGE

1. They are simple and can be done by most people

2. They use locally available materials and simple technology, the keeping costs low.

3. No harmful chemicals are added to the food.

4. Curing and smoking add a distinctive flavor to the food

5. Most methods do not destroy nutrients

DISADVANTAGES OF TRADITIONAL METHODS OF FOOD STORAGE, PROCESSING ANDPRESERVATION

1. Food can be preserved and stored for only limited periods of time

2. Traditional method is difficult to do on a large scale.

3. Traditional methods are highly limited in the variety of foods that can be processed, preserved and stored

(b) MODERN METHODS OF FOOD PRESERVATION AND PROCESSING

1. PASTEURIZATION

Is a method which involves heating food to very high temperature for a short time to kill enzymes and microorganisms that can cause food spoilage.

Pasteurizations maintain the nutrients content and flavor of food.

Example of food which can be pasteurized are milk and fruit juice

2. LIQUEFICATION

This method involves the making of liquids from solid food.

It is mostly applied to fruits where by juice is made out of them.

The juice is then pasteurized and post into cans or containers.

3. CANNING AND BOTTLING

In this method, food is preserved by heating it in airtight vacuum – sealed bottles or cans.

First the container is filled with food then the air is pumped out to form a vacuum.

The container is sealed and heated to kill micro – organisms and enzymes

Foods that can be canned and bottled include tomatoes, fruits and fruits juices, beef, fish and baked beans

4. USING ADDITIVES

This involves preservation of food by using chemicals such as sodium benzoate, sodium chloride and vinegar to slow down the growth of microorganisms.

Examples the food can be preserved by this process are fish and meat.

5. FREEZING

This involves keeping food in freezer at a temperature below -10℃ to stop the growth of microorganisms.

– This method preserves the appearance, flavor, texture and nutritive value of food.

6. REFREGIRATION

This involves keeping perishable food in a refrigerator to slow down the growth of microorganisms which cause food spoilage.

This method is used to preserve food such as milk, meet, chicken, vegetables, fresh fruits, fish etc.

7. IRRADIATION

This involves use of rays of energy to stop growth of microorganisms in stored foodstuffs.

This method is used to preserve food such as onions, beans or potatoes.

ADVANTAGES OF MODERN METHODS OF FOOD PROCESSING, PRESERVATION AND STORAGE

i) Food can last for many months or even years

ii) Modern methods can process, preserve and store a large variety of foods.

iii) The advanced technology used is fast and can handle large quantities of food

DISADVANTAGES OF MODERN METHOD OF FOOD PROCESSING, PRESERVATION AND STORAGE

i). The chemicals used can be harmful if eaten in excess.

ii). These methods can only be used in a certain area. Example – refrigeration and freezing require electricity.

iii) The process used for example radiation; canning and pasteurizing require special skills.

iv) Sometimes nutrients are lost thus lowering the nutritional value of food.

DIFFERENCE BETWEEN TRADITIONAL AND MODERN METHODS OF FOOD PRESERVATION