• Nutrients- these are molecules which are required for growth,maintainance and repair

  • Macro-nutrients- are nutrients that are required in very large quantities

  • Micro-nutrients- these are nutrients which are needed in very small amounts

  • Auto-trophic nutrition- this is the process by which organisms manufacture their own food from simple inorganic substances like carbon and hydrogen.

  • Heterotrophic nutrition- this is a process by which living organisms get nutrients by eating other organisms.

  • Holozoic nutrition- this is taking complex food substances, digesting them, assimilating them in their bodies.

  • Saprophytism- is a relationship in which organisms obtain nutrients from dead decaying matter.

  • Symbiosis- this is a feeding relationship between two organism

  • Commensalism- this is a feeding relationship in which one organism benefits and the other is unaffected.

  • Mutualism- this is type of symbiosis in which both organisms benefits from the relationship

  • Parasitism- is a feeding relationship in which one organism benefits while the other one is harmed.

  • Balanced diet- this is a food substance that contains all nutrients in correct proportions

  • Obesity- is a nutritional disorder in which an individual has excess weight.

  • Anorexia nervosa- this is a disease in which an adolescent girl starves oneself by refusing to take enough food.

  • Monosaccharide’s- are simple sugars made up of simple sugars and sweet tasting.

  • Polysaccharides- are formed by condensation involving combination of two monosaccharides

  • Condensation- this is the process by which two or more monosaccharides combines to form disaccharides.

  • Polysaccharides- are formed by condensation involving several monosaccharides

  • Essential amino acids-these are amino acids which need to be provided in diet because the body cannot synthesize.

  • Non-essentially amino-acids- these are amino-acids which the body is capable of synthesizing and need not be provided in diet.


  • Nutrition is the process by which living things obtain nutrients assimilated and use them in their bodies.

  • Organism can obtain nutrients by two ways, making their own food or obtaining from other organisms.

  • Therefore we have two types of nutrition, heterotrophic and autotrophic nutrition.

  • Organisms need nutrients in order to grow and survive. These nutrients are obtained from food.

  • Food substance includes carbohydrates, Lipids, proteins, vitamins and mineral salts.

  • The building blocks of our bodies are called nutrients.

  • Nutrients can be macronutrients which are required in large scale or micronutrients, which the body does not require in large amount.

  • Nutrition is therefore one of the most important characteristics of living things.

Significance of nutrition

  • Organisms can obtain nutrients for growth.

  • Nutrients are required to replace, repair damaged tissues.

  • New impulse transmission is possible through the process of nutrition where energy is obtained.

  • Homeostasis and regulation is made possible because of nutrition which provides required energy.

  • Some organism such as glowing worms and fireflies need nutrients to produce light.

Forms of nutrition

Basically we have two main forms of nutrition

  1. Autotrophic this is main form of nutrition in which organisms synthesizes food from simple organic compounds.

  • This is carried out by plants and some bacteria. Plants use photosynthesis, while bacteria use chemosynthesis.

  • Photosynthesis is the process by which green plants make food using carbondioxide, water and sunlight.

  • Photosynthesis mostly occurs in leaves.

  1. Heterotrophic nutrition is a mode of nutrition where by living organism take in already manufactured food substances such as carbohydrate, proteins and fats.

  • Organism which obtain food this way are called heterotrophs.

  • Heterotrophs mainly consists of animals.

Forms of heterotrophic nutrition

  1. Holozoic nutrition this involves taking of complex food substances, digesting them and assimilating nutrients. This form of nutrition is divided into three groups.

  1. Carnivorous feeding: is mode of feeding whereby organisms feed on meat only. Organisms which feed on meet are called carnivores

  2. Herbivorous mode of feeding : is a mode of feeding where organisms feed on plants only. These organisms are called herbivores

  3. Omni onus made of feeding: is a made of feeding where organisms feed on both plant and animals.

  1. Saprophytism is a relationship in which an organism absorb nutrients from dead organic matter. Most fungi are saprophytes.

  2. Symbiosis is a close feeding relation between two species.

Forms of symbiosis

  1. Mutualism feeding relationships relationship where by both organisms benefits from the relationships. Examples are bacteria on part of ruminants and bacteria on root noddles of leguminous plants.

  2. Commensalism is a type of symbiosis where one organism benefit while the other By re s unaffected by relationship. Examples, small plants growing on large tree.

  3. Parasitism: one species benefits from the relationship, while the other on is harmed examples ticks on cows.

Human nutrition

Types and functions of food substances that help the body in growth. These are outlined or below.



The food substance includes beef. Chicken, fish, termiles, milk, eggs, lenticels, mushrooms e.t.c.


Protein is made up of smaller molecules called amino acid which are linked together by peptide bond. Many amino acid join together to form protein

Classes of protein

Protein are two types, first class protein, which are obtained from animals and second class protein, which is obtained from plants. First class protein contain all essential amino acids, second class protein lacks one or more amino acids, which are essentials. Amino acids can be essential or non essential. Essential amino acids cannot be synthesized by the body and has to be supplied on diet.

Non essential amino acids can be synthesized by the body and need not be supplied in diet.

Functions of proteins

  • Proteins helps in growth and repair of the body. Most cells are made protein.

  • Defense and protection

Antigens and antibodies are made of made of protein. Antibodies help the body destroy diseases causing micro organisms.

  • Sources of energy in times of starvation, proteins can be broken down to release energy.

  • Structural components

Many body organisms and tissues are made of protein. These structures include muscles fibre, hooves, nail hair, feather among other.

  • Structural functions

Many components in our body are made of protein. These includes anzymes, haemoglobin, hormones, and fibrinogen.

Properties of protein

  • Dissolve in water forming colloid a suspension. In this type of solution, sold particles remain separated in solution.

  • Protein are affected by high temperature when heated above a certain temperature, they become denatured.

  • Protein are amphotenic in nature. They can react with both acids and bases.



Maize, wheat, cassava, rice and chapatti, sugar, sucrose, bread.


Made up of carbon, hydrogen and oxygen in ratio of 1: 2: 1. They are called energy giving food.

Groups of carbohydrates


Are simple sugars, with chemical formula C6H2O

Example include glucose, fructose and galactose.

Properties of Monosaccharides

  • Are sweet tasting

  • Are soluble in water

  • They are crystallized

  • Are reducing sugar that is they can reduce copper II sulphate into copper I oxide

  • Monosaccharide can be combined to form disaccharides by a process called condensation where water molecule is lost, glucose + glucose? Maltose + Water

b) Disaccharides

Formed by linking two monosaccharides by the process of condensation. They can be broken into their constituent monosaccharides by a process known as hydrolysis.

Water is used in this process

Maltose +  Glucose + Glucose

Examples includes sucrose, maltose and lactose

Sucrose glucose + fruclose

Lactose  glucose + galactose

Properties of disaccharides.

  • Are soluble in water

  • They are crystalline in nature

  • Are non- reducing sugars.

c) Polysaccharides.

Formed when many monosaccharide’s combine together. They are then said to be complex in nature. Examples of polysaccharides include starch, cellulose and glycogen.


  • Are not sweet tasting

  • Are insoluble in water

  • Are uncrystallined


These are composed of fats and oils. They contain carbon, hydrogen and oxygen. They are insoluble in water.

Fats are sold at room temperature. Oils are liquids at room temperature. Fats acids can be essential or non essential fats acids. The body is not able to produce essential fats acids.


  • Oily fish

  • Nuts

  • Oil seeds

  • Avocado

  • Olives

Functions of Lipids

  • They are sources of energy. They produce more energy than carbohydrates. They however need a lot of oxygen to be broken down.

  • They are important components of cell membrane.

  • They are source of metabolic water. When broken down, fats are able to release a lot of water.

  • Lipids protect sensitive organs of the body such are kidney and heart where they act as shock absorber.

  • They provide insulation to the body against cold weather.

  • They are sources of vitamin A, D, E, and K are soluble in fats.


Are complex organic micro nutrients that are essential for growth and survival. Vitamins can be, fat- soluble can be stored in body and need not be consumed daily. Examples are vitamin A, D, K and E.

Water soluble: vitamins are not stored in the body. They are thus consumed daily. Vitamins B and C are water soluble.

The table below shows types of Vitamins, use sources and deficiency disease.




Deficiency disorder


Night vision

Protects skin

Vegetable, kale, spinach.

Milk, liver, Eggs, carrots

Night blindness

Poor vision


Cells metabolism and energy release.

Liver, meat, unpolished grains.

Cracks and sores in mouth, visual problems.


Proper growth

Cell respiration

Egg York, kidney

Beans unpolished cereals

Beri- beri


Need for enzyme action

Nuts, fish, meat, yeast extracts, unpolished rice


B6 (Pyridoxine)

Need in protein metabolism

Meat, vegetables yeast, extracts, whole grains

New irritability sore in mouth anemia.


Form red blood cells build genetic material

Fish, meat, egg, milk liver.

Anemia, new damage.

Vit C (ascorbic Acid)

Antioxidant. Improves absorption of energy, college synthesis

Cirtirus fruits refresh green, vegetables liver.

Muscles weakness early bruising, bleeding gun infections.

Vit D Calciferol

Egg yolk, milk, oil fish and liver

Build and maintain teeth and bone.

Rickets in children. osteoporosis in adult.

Vit. E. Tocopheral

Antioxidant prevent cell damage and membranes damage

Corn or sunflowerter, butter, brown rice peanuts.

Nave abnormalities infertility in rats.

Vit. K.

Needed for Normal blood clothing

Green vegetables and liver

Defective blood coagulation resulting in excessive bleeding.

Table 1.1

Mineral Elements.

Plants obtain elements from soil through absorption. Human’s and Mammals obtained obtain elements from food they eat.

Minerals elements are need for body growth, repair and protection against diseases. They take part in various chemical reactions in the boy. The table below summaries sources and function of minerals.




Potassium (K)

Most foods

Muscular contraction

New transmission.

Calcium (Ca)

Milk and its products green vegetables

Strong bones and teeth, muscle contraction nerve impulse, clothing.

Phosphorus (P)

Milk, meat, fish, eggs nuts.

Bone and teeth building

Muscles and nerve impulse.

Sodium (Na)

Table salt, green vegetable

Muscular contraction, tissue fluid balance, nerve transmission.

Sulphur (S)

Amino acid and methionine in animals protein.

Synthesis of proteins.

Chlorine (Cl)

Table salt, sea foods

Maintenance of tissue fluids blood and lymph.

Iodine I

Ground water, sea food, table salt.

Synthesis of thyroids hormone

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