BIOLOGY O LEVEL(FORM TWO) NOTES – NUTRITION -2

When a ruminant first chews and swallows a mouthful of plant matter, the food enters the rumen. Bacteria in the rumen immediately start digesting the cellulose present in the material. Chewing cud softens and helps down plant fibres, making them more access to digestion by the bacteria. When the food in the rumen, it is coarse and very green. The food then regurgitated and chewed again. It passes the reticulum. The reticulum has a ‘honeycomb” appearance. In the reticulum, the food is mixed thoroughly with water. The food coarse, more watery, less green and very small compared to the food in the rumen.

The food is regurgitated, chewed again and passed to the omasum. The abomasum has longitudinal folds like the leaves of a book. The folds help to remove water from the food. The food in the omasum is in form of fine particle and has very little water.

The abomasum is the ruminant’s stomach. The abomasum has gastric acid facilitates the digestion of proteins. It also has microorganisms that may have spilled over the rumen.

OUTER SIDE OF RUMINANT STOMACH

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Differences between the ruminant System and the human digestive system are:

Ruminant digestive system has four chambers. Human beings have one stomach chamber.
Ruminants have no upper incisors. Instead, they have a horny pad. This helps in the chewing of food. They also have a gap on the lower jaw called diastema. –humans have upper incisors and no diastema. Ruminants chew cud. They regurgitate what they had swallowed and chew it again. Human beings do not chew cud.
Ruminant’s digestive system has organisms(bacteria) that help to digest fibre and synthesize vitamin B. Human beings cannot digest fibre.

Diseases and disorders of the digestive system

This includes diseases and disorders that affect; the oesphagus, the stomach and the

large intestines. Examples include dental caries heartburn, stomach ulcers, constipation flatulence and cancer.

1. ULCERS

These occur as a result of the action of enzymes and acid on the epithelial membrane lining of the stomach and duodenum walls. The mucus coating can be broken by bacteria called Hericobacter pylori

Cause

Ulcers can be caused by stress which stimulates acid production
Ulcers can also be inherited.
Certain medication like aspirin
Smoking and taking alcohol
Caffeine

Sign and symptoms of ulcers

Burning pain in stomach or the middle of thorax
Nausea and vomiting
Tiredness and weakness
Blood in vomiting or stool (a symptom of breeding ulcer)

CONTROL OF ULCERS

Ulcers can be controlled as follows

1) Have stress reduction programs

2) Eliminate smoking and drinking alcohol

3) Changing diet and taking meals on time

– The ulcers can be corrected or reduced by the following treatment

1. Drinking milk

2. Taking magnesium trisilicate tablet

3. Surgery which include

– Cutting the vestigial part

– Gastrectomy removal of the duodenum and the stomach.

2. CONSTIPATION

– This is the frequent passage of hard faeces

Constipation is caused by the following:

(i) Abnormally slow movement of faeces matter through colon. As a result maximum absorption of water takes place leaving very dry hard faeces.

(ii) A diet low in fibre such as roughages

(iii) Failure of the sensory cells to signal the presence of faecial matter in rectum.

CONTROL

Constipation can be controlled by

(i) Eating high fibre rich food.

(ii) Drinking a lot of water.

3. HEART BURNS

This is the burning sensation along the alimentary canal or in the chest cavity as a result of accumulation of too much acid in the stomach.

An individual with this problem feels uncomfortable all the time
Prolonged heart burn can lead to oesophagus ulcers

CONTROL

Heart burn can be reduced by drinking milk or taking tablets which neutralize the acid of the chyme.

4. FLATULENCE

This is a condition caused by excessive gas in the digestive track it causes pain and embarrassment to many individuals.

The intestinal gas such as oxygen and nitrogen are gulped in while breathing and at the same time eating
Other gases such as methane, carbon dioxide and hydrogen are produced from fermented undigested food
The gases in the intestine can be minimized by

(i) Eating slowly

(ii) Avoid milk if you are lactose intolerant

(iii) Not eating gas – inducing food such as beans, cabbage, onions

(iv) Using antacids

DENTAL CARIES

This is commonly referred to as tooth decay. It occurs when bacteria destroy the outer part of the tooth.

Development of dental caries

There are always bacteria present in the mouth. The bacteria combine with acid, saliva and remains of food to form plaque. Plaque is the sticky substance often found between teeth. Plaque begins to form within 20 minutes after we eat. 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.

This disease is caused by a number of factors including:

(i) Lack of hard food

(ii) Too much sweet food

Sweet food tends to encourage growth of bacteria

(iii)Lack of calcium in the diet

(iv)Lack of vitamin D

(v) General ill health

CANCER

Cancer is a disease which affects the digestive tract include

Cancer of oesophagus
Cancer of the colon

There are various causative agents of cancer, Their common ones include

i) Mutation of genes

ii) Cancer inducing foods we eat. They affect the colon when they come in contact over a long direction of time

TREATMENT

It has not been up to date easy to treat or prevent cancer. The following methods are applied in treating it.

1) Chemotherapy – During treatment to supplement surgery

2) Radiation – Bombardment using radioactive particles to eliminate the cancerous cells

3) Surgery – Removal of all cancerous cells

NOTE: The outlined treatment are not 100% perfects, they will affect other cells or induce other cells to become cancerous

CONTROL

Taking the fibre food in the food to come into contact with the cells leaving the colon wall

NUTRITION IN PLANTS

AUTOTROPHISM

This is the mode of nutrition used by green plants to manufacture their own food.

The process is used by green plants to manufacture their food is known as photosynthesis.

Definition – photosynthesis is the process in which green plants manufacture complex food substances from simple inorganic substances such as carbon dioxide and water in the process of sunlight and chlorophyll

This process of photosynthesis occurs in the green parts of the plants mostly in leaves

STRUCTURE OF THE LEAF

A) EXTERNAL PARTS OF THE LEAF

1) Petiole – attaches the leaf to stem or branch.

2) Veins – Transport materials within the leaf

3) Midrib – gives rise to veins. Transport materials to the leaf

4) Lamina- photosynthesis takes place in it.

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B) INTERNAL PARTS OF THE LEAF

The internal parts of the leaf consist of

1) Cuticle

2) Epidermis

3) Guard cell

4) Palisade layer

5) Spongy mesophyll layer

6) Leaf veins

7) Chloroplast

Diagram showing the internal parts of a leaf

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FUNCTION OF THE INTERNAL PARTS OF LEAF

a) CUTILE – This is a thin wax transparent and water proof

– It is found on both sides of the leaf

Functions

(i) Reduce excessive water loss

(ii) Protects inner tissue from damage

(iii) Prevents entry of pathogens

b) EPIDERMIS – This is a thin layer found on both sides

Functions

i) secretes (makes) the cuticle

ii) Protects inner tissue from damage

c) GUARD CELLS

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

Functions

i) Control opening and closing of stomata

ii) Control water loss

iii) Allow gaseous exchange

iv) Contain chloroplasts with chlorophyll used to trap sunlight for the process of photosynthesis.

d) PALISADE LAYER

This is the layer between the upper epidermis and the spongy mesophyll layer

It is made up of palisade cells

Functions – trap sunlight by using chlorophyll
for the process of photosynthesis

e) SPONGY MESOPHYLL LAYER

This is found between the palisade layer and the lower epidermis

Function

i) Used for gaseous exchange

ii) Photosynthesis takes place in it

f) LEAF VEINS

Consist of both xylem and phloem

Functions:

Xylem transport water and mineral salts from the root to the rest parts of the plants.
ii) Phloem transport manufactured food from the leaves to the rest parts of the plant.

g) CHLOROPLAST

These are disc shaped organelles that contain chlorophyll

Functions:

Chlorophyll absorbs (traps) sunlight for photosynthesis

REQUIREMENTS AND CONDITIONS NECESSARY FOR PHOTOSYNTHESIS

The raw materials of photosynthesis are:

a) Carbon dioxide

b) Water

Carbon dioxide is obtained from the atmosphere and water is absorbed by the roots from the soil.
The conditions necessary for photosynthesis to take place are

(i) Chlorophyll

(ii) Sunlight

Chlorophyll is used to absorb light energy needed during photosynthesis and sunlight (solar energy) is converted to chemical energy (ATP) needed by all living organisms

PROCESS OF PHOTOSYNTHESIS

The process of photosynthesis occurs in two stages which are:

(i) The light stage.

(ii) The dark stage.

THE LIGHT STAGE

It occurs in the chloroplasts
The chlorophyll absorbs light energy from the sun
The light energy is used to split the water molecules to oxygen and hydrogen

The process is known as photosynthesis

Oxygen is released to the atmosphere while some is used in respiration

Hydrogen enters the dark reactions
Some of the solar energy absorbed by the chlorophyll molecules is used in the formation of energy rich compound known as Adenosine triphosphate (ATP) which later is used in the dark stage of photosynthesis

THE DARK STAGE

It occurs in the stomata and it doesn’t need a light
Carbon – dioxide combines with hydrogen to form sugar such as glucose
This process is called carbon dioxide fixation
This process requires energy (ATP) and enzymes i.e.

END PRODUCTS OF PHOTOSYNTHESIS

The end products of photosynthesis are:

i) Glucose

ii) Oxygen

iii) Water

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

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

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

The overall chemical equation representing the process of photosynthesis

ADAPTATION OF THE LEAF IN THE PROCESS OF PHOTOSYNTHESIS

(i) Cuticle and epidermis are transparent to allow easy penetration of light

(ii) Presence of stomata on the leaf allows easy diffusion of carbon dioxide

(iii)The network of veins allows movement of materials in and out of the leaf

(iv)The air spaces in the spongy mesophyll layer allow gases to circulate easily.

(v) Presence of large numbers of chloroplasts in the palisade layer enables maximum sunlight absorption.

(vi) The leaves are well arranged to avoid overlapping and overshadowing

(vii) Broad and flat lamina allows maximum absorption of sunlight and carbon dioxide.

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. CARBON – DIOXIDE 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: Photosynthesis is controlled by enzymes. Enzymes are affected by changes in temperature.

– High temperature destroys the enzymes, very low temperature inactivate them.

– 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

IMPORTANCE OF PHOTOSYNTHESIS

(i) Food substance like glucose is formed. Plants and animals use these food substances.

(ii) Release oxygen in the atmosphere for respiration of organisms

(iii) Purify the atmosphere by removing carbon dioxide.

(iv) Light energy is converted into a form that can be used by all other organisms. This energy is known as ATP.

STORAGE ORGANS

Plants store food for future use

Foods in plants can be stored in:

(a) Leaves e.g. Onions, cabbage

(b) Fruits e.g. Mango, pineapple, pawpaw

(d) Stems e.g. Irish potato, ginger, sugar cane

(e) Roots e.g. Sweet potato, cassava, carrots