2.0     INTRODUCTION TO NUTRITION

Nutrition is a fundamental aspect of life, involving the process by which living organisms obtain and utilize food and nutrients to support growth, metabolism and the repair of tissues.

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TYPES OF NUTRITION

• Autotrophic Nutrition – Organisms that produce their own food (e.g., plants via photosynthesis).
• Heterotrophic Nutrition – Organisms that depend on other organisms for their own food (e.g, mammals).

          2.1     MODES OF NUTRITION

• Holozoic Nutrition – Found in animals; involves ingestion, digestion, absorption, and assimilation (e.g., humans).
• Saprophytic Nutrition – Involves feeding on dead organic matter (e.g., fungi, bacteria).
• Parasitic Nutrition – Organisms derive nutrients from a host organism, harming it in the process (e.g., tapeworms, plasmodium).
• Symbiotic Nutrition – Two organisms live together for mutual benefit (e.g., nitrogen-fixing bacteria and leguminous plants).
• Chemosynthetic Nutrition – It is the mode of nutrition in which certain organisms are able to synthesise organic compounds from simple Inorganic materials such as water, ammonia, nitrite to manufacture their food.
• Photosynthesis (Autotrophic Nutrition) – Process by which green plants use sunlight to convert carbon dioxide and water into glucose and oxygen. This process occurs in the chloroplasts of plant cells with chlorophyll as the main pigment.

MECHANISM OF PHOTOSYNTHESIS

Photosynthesis is an endothermic reaction and it consists of a series of complex reactions. These reactions are grouped into two stages;

• Light reaction stage
• Dark reaction stage

          2.2     MINERAL REQUIREMENTS OF PLANTS

Plants require mineral nutrients or elements obtained from the soil in the form of solution for good growth and healthy development. These elements or plant nutrients are grouped into two classes.

• Macronutrients – Carbohydrates, proteins, and fats, which provide energy and serve as building blocks for the body. They include potassium, magnesium, iron, calcium, oxygen, hydrogen, carbon, nitrogen e.t.c.
• Micronutrients – Vitamins and minerals needed in smaller amounts that are essential for numerous metabolic processes e.g, zinc, boron, copper, chlorine, manganese, cobalt e.t.c

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          2.3     CLASSIFICATION OF FOOD SUBSTANCES

• Carbohydrates – Provide energy.
• Proteins – Build and repair tissues; involved in enzyme and hormone production.
• Fats (Lipids) – Store energy, protect organs, and insulate the body.
• Vitamins – Organic compounds that support immune function, bone health, and vision (e.g. Vitamin A, B, C).
• Minerals – Inorganic elements important for body structure and function (e.g., calcium, iron, potassium).
• Water – Essential for chemical reactions, transportation of substances, and temperature regulation.

GROWTH – This can be defined as an irreversible increase in size and mass of an organism, resulting from cell division and enlargement.

        2.4     FUNCTIONS AND DEFICIENCY OF SOME VITAMIN

• Vitamin A – Night blindness and poor vision.
• Vitamin B – Beriberi.
• Vitamin C – Scurvy.
• Vitamin D – Rickets, osteomalacia.
• Vitamin E – Reproductive failure e.g, sterility.
• Vitamin K – Haemorrhage i.e inability of the blood to clot in time.
• • FOOD TEST

TEST FOR PROTEIN

• Biuret’s test – Mixture will turn purple or violet colour.
• Millions test – A red precipitate would appear.

TEST FOR STARCH

• Iodine solution – The colour of the starch will change to blue-black.

TEST FOR REDUCING SUGAR (e.g glucose, fructose)

• Benedict’s solution – A brick red or orange precipitate is seen.

TEST FOR NON-REDUCING SUGAR (e.g sucrose, maltose, lactose)

• Benedict or Fehling solution – A yellow precipitate is observed.

TEST FOR FAT AND OILS

• Sudan(iii) test – A red colouration appears before boiling while a black.

precipitate is formed after boiling.

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       2.6     DENTITION

It refers to the number, arrangement and confirmation of teeth in an organism. It plays a crucial role in the digestion process by enabling the mechanical breakdown of food, and it is also an important aspect of an organism’s overall anatomy and health.

TYPES OF DENTITION

• Homodont dentition – Organisms possess the same type of teeth ,they are found in fishes, amphibians and reptiles.
• Heterodont dentition – Organisms possess teeth of different shapes, sizes, and functions. They are found in mammals.

         2.7     TYPES AND FUNCTIONS OF TEETH

• Incisors – It is used for cutting and holding.
• Canines – It is used for tearing and catching the prey.
• Premolars – It is used for grinding and chewing.
• Polars – It is used for chewing and grinding.