CHAPTER 6 NUTRITION

Learning objectives:

- State the types of nutrition

- Explain autotrophic and heterotrophic nutrition

- Classify organisms according to the types of nutrition

6.1 Types of Nutrition

1. Nutrition is the process in which organisms obtain energy and nutrients from food for

growth, maintenance and repair of damaged tissues.

2. Nutrients are used for energy and growth that includes proteins, carbohydrates, fats,

vitamins, minerals and water.

3. Nutrition includes the following processes:

a. Ingestion

i. Taking food into the body by mouth

b. Digestion

i. Breaking up ingested food mechanically and chemically into smaller

molecules to be absorbed

c. Absorption

i. Process which nutrients are absorbed via lining of intestinal tract into blood

capillaries and blood stream

d. Assimilation

i. Nutrients are absorbed into the cells for the use of metabolism

4. Nutrition is divided into two:

a. Heterotrophic nutrition: obtain nutrients by feeding on organic matter which

unable to produce own food

b. Autotrophic nutrition: synthesising nutrients from simple inorganic compounds.

Able to produce own food as such plants produce food from photosynthesis.

6.1.1 Autotrophic Nutrition

1. Autotroph are organisms that capable of synthesising their own organic substances from

inorganic compounds.

2. Types of autotroph:

a. Photoautotroph: organisms that carry out photosynthesis to produce organic

substances

b. Chemoautotroph: organisms carry out chemosynthesis which they use energy from

oxidation of inorganic substances

i. Sulphur bacteria use energy released from oxidation of hydrogen suphide to

form carbohydrates

ii. Nitrifying bacteria (Nitrosomonas sp, Nitrococcus sp.) obtain energy by

oxidising ammonia to nitrate

iii. Nitrobacter oxide nitrates into nitrites

6.1.2 Heterotrophic Nutrition

1. Holozoic nutrition

a. Animals feed by ingesting solid organic matter

b. Specialised digestive system

c. Herbivores, omnivores, carnivores, detritivores

2. Saprophytic nutrition

a. Saprophytes carry out saprophytism nutrition that feed on dead and decaying

matter

b. Extracellular digestion secrete enzymes onto food and digest externally before

absorbing the nutrients

c. Saprophytic fungi and saprophytic bacteria

d. Also called decomposers

3. Parasitism nutrition

a. Feed on other organisms hosts

b. Digest hosts cells before absorbing them

c. Harm hosts: tapeworms, ticks, lice, fleas

Saprophytes vs Parasites

Saprophytes Parasites

Simple methods of nutrition: use variety of food sources

Highly adapted to obtain nutrients from hosts

Feed and obtain energy on dead, decaying matter

Lives on or in the body of hosts and obtain energy from them

Bacteria and fungi Viruses, protozoans, fungi, bacteria,

Aerobic and anaerobic Aerobic

6.2 Concept of Balanced Diet

Learning objectives

- Explain necessity for balanced diet

- Explain factors affecting daily energy requirement of human body

- Determine energy value in food samples

- Determine nutrient content in different food samples

- Explain functions and sources of vitamins, roughage/dietary fibre and minerals in a diet to

maintain health

- Explain function of water in body

- Justify selection of appropriate balanced diet for specific target group

6.2.1 Classes of food

Carbohydrates Supply energy

Protein Provide materials for growth and repair

Lipids/fats Provide energy and stores excess food Dissolve fat soluble vitamins

Vitamins Organic compound required in small amount

Minerals Inorganic substances required for teeth, bones, muscles

Dietary fibre/roughage Stimulates peristalsis and prevent constipation

Water Medium for all chemical reactions in cell, transportation, excretion and body temperature control

6.2.2 Factors affecting daily energy requirement

1. Carbohydrates and fats provide energy required for the body.

2. Energy required by the body is generated by the oxidation of molecules obtained from food

during cellular respiration.

3. Energy in food is measured in kilojoules (J).

4. Energy required are for body heat, maintain Basal Metabolic Rate (BMR) and energy for

physical activities.

5. BMR Basal: minimum background energy that needed to maintain vital life processes such

as heartbeat, nerve impulses, breathing, opt temperature, chemical changes, physical

posture.

6. Metabolism is the sum of all chemical reactions in the body.

7. Factors affecting daily energy requirements:

Climate People live in cold countries need more energy to maintain body temperature

Age Children and young adults need more energy than old people

Size Bigger build person need more energy than smaller build

Health condition Pregnant woman need more energy Lactation energy requirement for breast-feeding mother increases

Gender Men have higher metabolism than women

Occupation People with heavy and active work need more energy

Lifestyle Active person need more energy

8. Dietary requirements

6.2.3 Energy content in food

1. Energy value amount of energy contained in unit weight of substance when it is

completely oxidised.

2. Energy value of food is measured in units of joule per gram (J/g) or kilojoules per gram

(kJ/g).

3. Cellular respiration releases energy.

4. Energy value of the main classes of food:

a. Carbohydrates: 16 kJ/g

b. Protein: 17 kJ/g

c. Fat: 38 kJ/g

5. Energy value of food is measured with bomb calorimeter.

a. A known mass of food is completely burnt in a bomb calorimeter

b. Heat released is transferred to a known volume of water

c. Temperature increase of water is measured by using thermometer

d. Amount of energy is calculated: Q = mct; where m is mass of water, c = 4.2 J/gC and

t is temperature

A cup of tea with milk 150kJ

A piece of bread with butter 600kJ

One fried egg 650kJ

One serving of salad 20kJ

One serving of curry chicken 300kJ

6.2.4 Vitamins

1. Play important role as organic compound in various enzymatic reactions and building and

maintaining body tissues.

2. Divided into two:

a. Fat-soluble vitamins (ADEK)

b. Water-soluble vitamins (BC)

3. The skin can synthesise vitamin D using sunlight.

6.2.5 Minerals

1. Minerals are essential inorganic elements needed in small quantities for chemical

reactions and building molecules in the body.

2. Minerals are grouped into:

a. Macro-minerals needed in bigger quantity which are calcium, magnesium,

potassium, phosphorus, sodium

b. Micro-minerals needed in small quantity are iodine, iron, copper, fluorine, zinc

6.2.6 Roughage

1. Dietary fibre reduce cholesterol level, reduce heart diseases and colon cancer.

2. Roughage is indigested plant matter that consist of cellulose.

3. Human alimentary canal has no cellulase enzyme to digest cellulose fibre.

4. Functions of roughage include:

a. Adds bulk to food and enables alimentary canal muscles to grip it and keep it moving

(peristalsis), especially in large intestine

b. Help retain water and absorb poisonous substances from gut

c. Softens faeces

5. Absence of roughage can cause constipation and increase risk of colon cancer.

6.2.7 Water

Functions of water:

6.3 Malnutrition

Learning Objectives

- Definition of malnutrition

- Effects of malnutrition by using examples

- Describe ways to reduce chance of contracting health problems due to ones diet

- Describe ways to reduce effects of certain health problems

1. A person suffers from malnutrition experience symptoms like:

a. Daily diet lacks such vitamins, mineral salts

b. Protein n diet is of poor quality

c. Body does not assimilate sufficient of digested food products due to intestinal

infection or worm infestations

Health problems Preventive steps

Cardiovascular disease - Atherosclerosis

Reduce intake of saturated fats and salt

Overweight, obesity Reduce intake of carbohydrates and calories

Diabetes mellitus Reduce intake of refined sugar

QUICK CHECKPOINT!

1. Name the diseases due to lack of vitamin D and iron. [2 marks]

2. Explain how an unbalanced diet may cause health problem to a person. [10 marks]