Concepts of Nutrition and food Nutrients

Meaning of nutrition:

Nutrition is the process by which organisms take in and use nutrients.

Nutrients are any substances that nourish an organism.

Food is any material when taken in absorbed and utilized meet requirement of plant and animal body.

The Concepts of Nutrition and Food Nutrients


  1. Oxidized to release energy
  2. Used in growth of cells
  3. Used to repair lost cells and tissue



There are two main types of nutrition: autotrophic nutrition and heterotrophic nutrition.

Autotrophic Nutrition

Is the process by which organisms manufacture their own food from simple inorganic substances like carbon and hydrogen using either light energy(photosynthesis) or chemical energy (chemosynthesis)


Heterotrophic Nutrition

Is the process in which organisms get nutrients by eating other organisms

The Importance of Nutrition in Living Things

  1. Prevent diseases
  2. Helps growth and development of cells, tissue and organs
  3. It helps to repair damaged parts
  4. It helps to protect the body against infection and diseases


Nutrition in Mammals, Human Nutrition

Human Nutrition:

Human Nutrition is the provision to obtain the essential nutrients necessary to support life and health.


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

The basic food substances include proteins, carbohydrates, lipids, vitamins, minerals, roughage and water. Involves taking in food through mouth.  Extra material is removed through egestion.

Different Types of Food Substances and their Functions in Human Body

  1. Carbohydrates
  2. Proteins
  3. Lipids (oils & fats)
  4. Mineral salts
  5. Water
  6. Vitamins
  7. Roughage




These are substances, which contain elements oxygen and nitrogen. Simplest unit is amino acid.

Properties of protein:

  1. Insoluble in water
  2. Coagulates on heating
  3. Reacts with millon reagent to form a red colour. This is the basis for the millons reagent test for proteins.
  4. Reacts with sodium hydroxide and copper II sulphate to produce a purple colour which intensifies on heating. This is the basis for BIURET TEST for proteins.
  5. Very large molecules which diffuse very slowly across membranes.

Natural sources of proteins:

Milk and milk products, Fish, Eggs, Beef, Pork, Chicken, Beans, Peas

Examples of proteins:

  1. Myosin and Myoglobin in muscles
  2. Albumin in eggs
  3. Keratin in hair and nails
  4. Haemoglobin in blood (RBC)


  1. Materials for body building
  2. Used as strengthening and structural material
  3. Used as storage materials
  4. Provides energy during starvation
  5. Used for protection
  6. Used by body for tissue growth and repair such as healing of wounds and replacement of skin
  7. It enables red blood cells to transport oxygen in our bodies




Carbohydrates – are substances which contain carbon, hydrogen and oxygen. Hydrogen and oxygen are in the ration of 2:1. In plants they are stored as starch, In animals they are stored as glycogen

Composition of carbohydrate

  • Carbon, oxygen and hydrogen
  • Simplest sugar or saccharide

Classification of carbohydrates

There are 3 types of carbohydrates.

  1. Monosaccharide– it is made up of one saccharide e.g. Glucose, fructose and galactose.
  2. Disaccharide-made up of two saccharides chemically combined together e.g. Sucrose, glucose and fructose

(Milk, sugar) lactose → Glucose + galactose

Maltose →Glucose + glucose

  1. Polysaccharide– made up of more than 2 saccharides chemically combined. E.g. Starch, cellulose, glycogen.

Condensation– is a process of bringing two molecules together chemically with release of water.

Glucose + glucose → Maltose + water

Disaccharide and polysaccharides are chemically combined.  The chemical combination is called condensation.

Hydrolysis– is a process of breaking down complex carbohydrates chemically by addition of water.


Reducing sugars and non –reducing sugars

A reducing sugar is any carbohydrate that can convert copper II sulphate into copper I oxide.

The reducing sugar has free functional groups which reduce the copper II sulphate to copper I oxide.   The functional groups are either KETONES or ALDEHYDES.  All monosaccharides and disaccharides except sucrose are reducing sugars.


A non reducing sugar is a carbohydrate that can’t convert copper II sulphate into copper I oxide.  The non reducing sugar doesn’t have free functional groups which reduce the copper II sulphate to copper I oxide.  Sucrose is the only non reducing disaccharide known so far the polysaccharides do not react with the copper sulphate.

Properties of carbohydrates:


  1. Colourless
  2. Soluble in water
  3. Tastes sweet
  4. Diffuses through semi permeable membrane
  5. Converts copper sulphate to copper I oxide – basis for test of reducing sugars


  1. Colourless
  2. Very soluble in water
  3. Tastes very sweet
  4. Diffuses slowly through semi permeable membrane
  5. Except for sucrose they can convert copper II sulphate to copper I oxide


  1. Starch
  2. Insoluble in water
  3. Forms a gel when boiled with water and cooled
  4. Tasteless
  5. It gives you a blue –black colour with iodine solution


  • Insoluble in water
  • Completely hydrolysed or broken down to sulphur acid to simple sugar
  • Reacts with iodine solution and changes from white to light blue.


  • Soluble in water
  • Gives a reddish brown colour with iodine solution


  1. Root crops – yams, cassava, potatoes, beet, carrots.
  2. Fruits- oranges, mangoes, apples, bananas, pineapple.
  3. Cereals- maize, wheat, rice, millet, sorghum
  4. Pulses- beans, peas
  5. Stem- sugarcane
  6. Leaves- onions, spinach


Importance of carbohydrates:

  1. Provides energy
  2. Structural substances
  3. Storage substances



These are compounds of carbon, hydrogen and oxygen. They are insoluble in water. Lipids are made up of fatty acid and glycogen


Foods such as fish, nuts, seed oils, avocados and olives are good sources of lipids.


They are 2 types of lipids: a) Fats  b) oils

Fats:  are solid at room temperature, while oils are liquids. Fats are mainly of animal origin while oils are of plant origin. The smallest unit of both oils and fats is fatty acids and glycerol.

Properties of Lipids:

  1. Insoluble in water
  2. Dissolves in organic solvents e.g. Chloroform, ethanol.
  3. When oil is shaken in water the oils breaks down into droplets which disperse in water.
  4. When rubbed against paper, the paper becomes translucent.
  5. In a mixture of oils and water, oil takes up SUDAN II and becomes red leaving the clear confirmatory test for lipids.
  6. Reacts with osmic acid to form a black colour.

Examples of lipids:

  1. Animal fats from meat
  2. Olive oils from olives
  3. Ground nut oil from ground nuts
  4. Coconut oil from coconuts
  5. Cashew nut oil from cashew nuts
  6. Palm oil from palm fruits
  7. Corn oil from corn/maize
  8. Sunflower oil from sunflower seeds


  1. Lipids are used as a source of energy
  2. Protect the organs such as heart and kidneys



Vitamins are chemical substances in small amounts that are used to maintain the body.

Vitamins can be grouped into two categories: water-soluble and fat-soluble vitamins.

Fat-Soluble Vitamins can be stored in the body. Examples of fat-soluble vitamins are Vitamins A, O, E and K

Water-Soluble Vitamins are not stored in the body. Vitamins B and C are water soluble.Vitamin B is of various forms, namely Vitamin B1, B2, B6 and B12.



Vitamin A(Retinol) Liver, Milk Carrots,Orange and Yellow Vegetables Essential for the formation of membranes of the eyes and the respiratory tract – Night blindness- Increased risk of infections
Vitamin B1(Thiamine) Lean meat,liver, eggs,tomatoes,yeast extract sand brown rice Carbohydrates metabolism of all foods and release of energy to cells – Beriberi- Loss of Appetite – Muscle cramps- Heart failure
Vitamin B2(Riboflavin) Liver,meat,wholegrain,cereals,yeast extracts Needed for metabolism of all foods and release energy to cells – Cracks and sores around the mouth and nose- Visual problems
Vitamin B6(Pyridoxine) Meat,vegetables,yeast extracts,whole grain cereals Essential in protein metabolism – Nerve irritability- Sores in the mouth and eyes- Anaemia
Vitamin B12(Cyanocobalamin) Fish, meat,eggs, milk and liver Builds genetic materials, help to form red blood cells – Anaemia- Nerve damage- Weight Loss
Vitamin C(Ascorbic Acid) Pawpaw,Citrus fruits,Fresh Green,vegetables,tomatoesandpotatoes -Increase resistant to diseases.  
Vitamin D(Calciterol) Egg yolk,milk, oilfish andliver Helps to build and maintain teeth and bones – Rickets in children- Osteoporosis (soft bones) in adults
Vitamin E(Tocopherol) Sunflower oil, butter,brown rice and peanuts – Antioxidant- Preventsdamage of cellmembrane – Nerve abnormalities- Infertility in rats
Vitamin K Green vegetables and liver Needed for normalblood clotting Defective blood coagulation resulting in excessive bleeding.


Certain mineral elements are vital for the proper functioning of the body. Some are required in relatively large quantities and therefore called macro mineral sand others are required in very small quantities and are referred to as micro

Macro minerals include calcium, phosphates, potassium, iron, zinc, sodiumchlorine and magnesium.

Micro minerals include iodine, fluoride, manganese and copper.

Examples of minerals, their source and their function in the body

Calcium Milk,Cheese,eggs and green vegetables – Helps build strong bones and teeth- Important inclotting of blood – Weak bones- Bleeding easily
Phosphates Meat, Milk,Fish, Eggs and nuts – Builds bones and teeth- Helps in muscle and nerve activity – Poor bone and teeth formation
Potassium Peanuts,bananas,orange juice and green beans Needed for nerve and muscle function – Poor muscle contraction
Iron Liver,kidney,beans and green vegetables Essential for making hemoglobin – Anemia
Zinc Meat, yeast Helps to heal wounds – Skin problems
Sodium Table salt – For nerve and muscle activity – Muscle cramps
Chlorine Table salt Formation of hydrochloric acid in the stomach – Poor digestion of protein
Magnesium Spinach,pumpkin seeds, black beans – Relaxation of nerves and muscles- Strengthening of bones – Muscle weakness- Irregular heartbeat- Weak bones
Copper Meat, fish and liver Activation of enzyme – Anemia- Bone and joint problems
Manganese Kidneys,liver, tea,coffee, nuts and fruits Formation of bones – Nausea- Dizziness- Loss of hearing
Iodine Iodized table salt and sea food Production of thyroid hormones which regulate growth – Goitre (enlarged thyroid gland)


– This is dietary fiber that is obtained from the indigestible parts of plants.


Foods such as fruits, beans, cabbage, spinach, cassava, and whole baked potatoes are good sources of roughage.


It helps in the passage of food and feces through the gut by aiding contraction of the gut muscles



This is a compound containing element hydrogen and oxygen


Food, Metabolic water, Direct drinking


  1. Used in digestion of food
  2. Used in transport of material in the body
  3. Used as solvent in chemical reaction
  4. Maintains shape of cells and organ
  5. Formation of protoplasm


Symptoms of water deficiency

  1. Thirst
  2. Urine decreases
  3. Colour of urine changes
  4. Faeces become dry


The Concept of Balanced Diet in Terms of Food Quality and Quantity


Meaning of balanced diet:A balanced diet refers to food containing all types of food nutrients in the correct proportions. We should eat a diet low in fats, sugars and salts but high in protein, carbohydrates, vitamins, minerals and roughage. More importantly we should take in large amounts of water.


In order for the body to function properly, different food substances are required to do different works for example:

  1. Carbohydrates provide energy
  2. Vitamins needed to keep the body healthy
  3. Minerals are needed for protection against diseases
  4. Water is a universal solvent

Nutritional Requirement for Different Groups of People

  1. Expectants: There diet should contain more protein and minerals (Calcium (Ca) and Iron (Fe))
  2. Lactating Mothers: Their requirements are like those of expectants but in greater amount to feed the body
  3. Children: Require a lot of proteins for growth and development of body tissue.
  4. The elderly People: They require adequate amounts of vitamins and minerals to maintain their health
  5. Sedentary workers: These are individuals who stay in one place for along time while performing their daily occupational activities. Due to their lifestyle and occupation, obesity is increasingly common among them, they limit their intake of food rich in lipids.
  6. Sick people: They need special and plenty of nutrients to help recover their health, those who have incurable diseases such as HIV/AIDS should get food that will help them to manage their conditions. They need to take plenty of fruits and water.

Different Types of Nutritional Deficiencies and Disorders in Human Beings


This is the condition, which occurs when one fails to feed on a balanced diet. It may be too little or eating only one type. These deficiencies and disorders include obesity, rickets, kwashiorkor, marasmus and anorexia nervosa.

Nutritional Disorders

These are conditions of ill health in a person, which arise as a result of lifestyle.

The Causes, Symptoms, Effect and Control Measures of Nutritional Deficiencies and Disorders

Causes of Malnutrition

There three cause of mulnutrition

  1. Eating too little
  2. Eating too much
  3. Eating one type of food

Effects of Malnutrition

  1. Excessive feeding causes obesity
  2. Under nutrition causes deficiency diseases


Kwashiorkor Shortage of protein in diet – Poor growth- Diarrhea- Loss of appetite- Pale skin- Dry skin- Change colour and texture- Body becomes weak and stomach protrudes – Consumption of foods rich in protein
Marasmus – Lack of and equate amount of food- Ignorance of balanced diet preparation of food, food hygiene – Weight loss- Slowed growth-Decrease dactivity- Lac k of energy – Shrunk enbuttocks – Getting adequate amounts of food – Balanced diet
Rickets Lack of vitamin D,Phosphates and Calcium – Bow legs- Knock knees- An odd shaped skul- Deformed spine – Provide food rich with vitamin D,Phosphates and Calcium
Scurvy Lack of vitamin C – Pain in joints- Stunted growth- Bleed in gums – Provide diet which containsfruits- Avoid prolonged cooking
Goitre Lack of iodine – Swelling of the thyroid gland – Provide iodized salt and water(H2O)



The digestive system of human refers to the human alimentary canal and the organs and glands

Parts of the Human Digestive System and their Adaptive Features

The main parts are:- Mouth, Oesophagus, stomach, small intestine, (duodenum and ileum), large intestine (colon) and rectum.

The Digestion Process in Human Being


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

Digestion process involves two processes, which are mechanical break down of food and chemical break down of food. The mechanical break down of food takes place in the mouth where the food is chewed by teeth so as to reduce it into small pieces.

Digestive enzymes achieve chemical break down of food. The digested food is absorbed and assimilated in the body.

The digestion process starts in the mouth where food is mechanically broken down by teeth. The presence of food in the mouth stimulates the salivary gland to produce more saliva.

The digestive system of man consists of the following parts:

  • The alimentary canal
  • Accessory organs
  • Liver
  • Pancreas

Parts of alimentary canal

Mouth, Oesophagus, Stomach, Small intestine, Duodenum, Ileum, Large intestine, Colon, rectum, Appendix, Anus

Digestion is the process of breaking large food particles into small parts which are easy to swallow, absorbable and utilizable.

The process of digestion has the following phases:

  1. Ingestion
  2. Digestion
  3. Absorption
  4. Utilization
  5. Egestion

Digestion in the mouth

Food is first ingested, and then digestion starts.  Two types of digestion take place in the mouth.

  1. Mechanical digestion– the mechanical digestion in the mouth is by chewing or MASTICATION.

Importance of chewing

  • Reduces large food particles to smaller particles which are easy to swallow.
  • Mixes the food with SALIVA which contains the digestive enzymes and MUCIN (substance which makes food slippery).
  • Increases the surface area of the food for better enzyme activity.

Role / function of saliva in digestion

  1. Contains an enzyme called PTYALIN or SALIVARY AMYLASE which digests cooked starch.
  2. Have mucus to lubricate food for easy swallowing
  3. Contains MUCIN which makes the food slippery for easy swallowing.
  4. Dissolves the chemicals taken in the mouth. The chemicals to reach the taste buds of the tongue for tasting.
  5. Makes the food alkaline.
  6. Have salivary amylase enzyme that converts starch into maltose
  7. To moisten the food
  8. To provide medium for enzyme reactions

Role of the tongue in digestion.

  1. Tasting the food
  2. Mixes the food with saliva
  3. Rolls the food into small balls called BOLI for easy swallowing
  4. Pushes the food into the PHARYNX for swallowing. Pharynx is a cavity behind the mouth.
  5. Chemical digestionThe enzymes involved in digestion are SALIVARY AMYLASE.  Salivary amylase helps in the hydrolysis of cooked starch into maltose. It acts in alkaline conditions.

Only cooked starch starts its digestion in the mouth.


Digestion in the stomach.

A stomach is a muscular bag which performs the following functions:

  1. Temporarily stored food
  2. Churns and mixes the food – mechanical digestion
  3. Carries out chemical digestion of protein
  4. Produces gastric juice
  5. Absorbs water and alcohol
  6. Produces mucus


  1. Stomach has sphincter muscles to prevent food from flowing back into the oesophagus
  2. Stomach has gastric glands, which produce gastric juice for the digestive process.
  3. Also in the stomach of a young baby there is renin which coagulates milk
  4. Stomachs have mucus which protects it from corrosion by digestive enzymes
  5. There is hydrochloric acid for the emulsification of fats and killing of bacteria

Once food reaches the stomach

  • The digestion of cooked starch stops since the stomach contents are acidic.
  • Digestion of protein starts. The wall of stomach has gastric glands which produce GASTRIC JUICE.

Composition of GASTRIC JUICE.

  1. Hydrochloric acid
  2. Renin
  3. Pepsin
  4. Mucus


The components of the gastric juice perform the following roles:

  1. A) Roles of hydrochloric acid
  2. Kills the micro-organisms that come along with the food/water.
  3. Converts the inactive form of pepsin (i.e. the precursor) into the active form.
  4. Converts the inactive forms of the renin into the active form.
  5. Breaks down complex sugars into simple sugars.
  6. B) Roles of renin

Renin converts the insoluble forms of milk protein into soluble form of milk protein.

  1. C) Roles of pepsin

Pepsin speeds up the hydrolysis of proteins into peptides.

Protein + water  ————->  Peptides

  1. D) Roles of mucus

Mucus prevents:

  • Corrosion of the stomach by HCl.
  • Digestion of the stomach wall by pepsin.


The food is well mixed by churning into a semi solid acidic food mixture called CHYME. The chyme can be stored in the stomach for variable times depending on the nutrient type.

  • Water can be stored for just a few minutes.
  • Carbohydrates can be stored for up to 4 hours.
  • Proteins and lipids can be stored for 4 to 6 hours. The chime moves into the duodenum by the periodic opening and closing of the pyloric sphincter.

Digestion in the Duodenum

The duodenum is a 30 cm long portion of the small intestine.  It is connected to the stomach by the pyloric sphincter.  Two ducts open into the DUODENUM.

Duodenum and its accessory organs

The bile duct – Bile duct transports bile from the gall bladder into the duodenum.  Bile is produced in the liver and stored in the gall bladder.

Composition of bile

Bile is greenish yellow juice.  It consists of:

  • Water
  • Greenish yellow substance
  • Bile salts
  • Mucin
  • Bi carbonates

Bile is periodically released into the duodenum every time food enters in.

Role of bile

  1. Bile salts react with the fat soluble vitamins to make them water soluble.
  2. Bile salts carry out EMULSIFICATION. Emulsification increases the surface area upon which the enzymes act.
  • Bile salts convert the inactive form of enzymes form into active form.
  1. The sodium bicarbonate salts neutralize the HCL and changes the food mixture into Alkaline chyme which makes it suitable medium of enzyme activity in the DUODENUM.


The pancreatic duct

The pancreatic duct connects the pancreas to the duodenum.  It transports the pancreatic juice from the pancreas to the duodenum.  Pancreatic juice is made in the pancreas.

Composition of pancreatic juice

  1. Pancreatic amylase
  2. Pancreatic lipase
  3. Trypsin
  4. Bicarbonate salts

Role of pancreatic juice

  1. The bicarbonate makes the duodenum contents alkaline
  2. Pancreatic amylase speeds up the hydrolysis of starch into maltose
  • Pancreatic lipase hydrolyses lipids into fatty acids and glycerol.
  1. Trypsin speeds up the hydrolysis of proteins into peptides.

Trypsin has a precursor called trypsinogen which is converted into active form by an enzyme called ENTEROKINASE.

Digestion of protein continues in the duodenum.  Digestion of cooked starch starts in the duodenum.

Digestion of lipids starts and ends in the duodenum.  The food mixture in the duodenum becomes watery and alkaline mixture called CHYLE.

The chyle is moved into the ileum by peristalsis.


Role of mucin/mucus

  • Protects against self digestion
  • Makes food slippery
  • Prevents corrosion of alimentary canal


Digestion in the ileum

The ileum is a 3 meter long portion of the small intestine.  It connects the duodenum and the large intestine.  The intestinal wall produces an intestinal juice called succus/ entericus.  The ileum is a center for digestion and absorption.

Composition of succus/entericus

  • Erepsin
  • Maltase
  • Sucrose
  • Lactose
  • Water
  • Bicarbonate salts

Role of succus/entirecus

Intestinal juice – has the above enzymes which performs the following roles.

  1. Erepsin completes the hydrolysis of proteins into amino acids.
  2. Maltose completes digestion of starch into glucose
  • Sucrose hydrolyses sucrose into glucose and fructose.
  1. Lactose hydrolyses lactose into glucose and galactose.


End products of digestion

  • Fatty acids and glycerol
  • Glucose
  • Fructose
  • Galactose
  • Amino acids

Fate of the end products of digestion

  1. Fatty acid and glycerol.

The fatty acid and glycerol are combined to make fats and oils.  The fats and oils may be converted to carbohydrate for energy production.

  1. Glucose, fructose and galactose

Glucose is directly used for energy production.  Fructose and galactose are converted into glucose for energy production.  If in excess, glucose is converted to fats and stored under the skin.

  1. Amino acids

The amino acids are combined to form proteins.  Proteins are used for body building and repair.  If in excess the amino acids are deaminated by the liver.  The amino parts is converted into urea by the liver and removed as a metabolic waste product in urine through kidneys.  The carbonyl part is converted into fats and stored.


Adaptations of the ileum for its function

  1. It is long to ensure a complete digestion of the foods and a complete absorption of the end products of digestion.
  2. The internal surface has finger like projections called villi which increases the surface area for absorption.
  • The inner layer is made up of a single layer of cell to reduce the distance through the end products pass into the blood.
  1. Each villus is provided with a dense network of blood capillaries and lymphatic vessels called lacteal. The vessel increases the rate of absorption by immediately transporting the product away from the site of absorption.  The blood capillaries join to form the hepatic digestion to the liver.

Difference Between the Human Digestive System with that of Other Mammals


The ruminants’ digestive system differs from human digestive system in thefollowing ways:

  • Ruminants have more elaborate system to enable cellulose digestion
  • The stomach of ruminants have four chambers (rumen, reticulum,omasum, abomasum)
  • The food is regurgitated, chewed, and again then passed to omasum.


Common Disorders and Diseases of the Human Digestive System

These include diseases and disorders that affect teeth, oesophagus, stomach, small intestine and large intestines

Examples are:- dental caries, heart burn, ulcers, constipation and flatulence.

  1. Dental caries This is commonly referred to as tooth decay. It occurs when bacteria destroy the outer part of the tooth.
  2. Heart burn Refers to the burning or painful sensation in the oesophagus. It is caused by regurgitation of hydrochloric acid in the stomach which leads to the irritation of oesophagus.
  3. Stomach ulcers Refers to the sore in stomach lining. It is caused by erosion of stomach wall due to enzyme reactions.
  4. Constipation Refers to the decrease in frequency of formation of stool. It occurs when the stool becomes dry and hard due to excessive water absorption in the colon.
  5. FlatulenceThis is caused by excess gas in the digestive tract


Causes, Symptoms, Effects and Control Measures of Common Disorders and Diseases of the Human Digestive System


  1. Tooth ache
  2. Holes in the teeth


  1. Regular brushing of teeth
  2. Damaged teeth can be filled with artificial crown
  3. Minimization of intake of foods rich in sugar
  4. Avoid eating very hot or cold foods
  5. Have regular dental check ups


  1. Burning pain in the stomach
  2. Nausea and vomiting
  3. Tiredness and weakness
  4. Blood in vomit or stool


  1. Medication
  2. Avoid smoking
  3. Avoid taking alcohol
  4. Avoid eating acidic foods


  1. Lack of bowel movements for two or three days
  2. Hard stools
  3. The urge to go for long call even after you have just been to the toilet


  1. Eat enough fibre
  2. Drink enough water
  3. Exercise regularly
  4. Seek medical help


  1. Swallowed air
  2. Eating food that causes gas such as beans, cabbage, milk and onions
  3. Poor absorptions of carbohydrates


  1. Abdominal pain
  2. The constant urge to pass wind
  3. Excessive belching
  4. Accumulation of gas in the stomach


  1. Avoid foods that produce gas
  2. Chewing food properly
  3. Limit the amount of food which are


Essential Mineral Element in Plant Nutrition

The mineral requirement in plant growth are categorized into two groups:

  1. Micro nutrients or minerals
  2. Macro nutrients

Macro nutrients are minerals that are required in a large quantity for the plant growth.

They include

Nitrogen, phosphorus, potassium, sulphur, sodium, magnesium, carbon, hydrogen,and oxygen.

Micro nutrients; these are nutrients that are required in small amount for the plant growth.

They include; iron, cobalt, fluoride, silicon, iodine, copper and zink

The Roles of Essential Elements in Plant Nutrition

element role Deficiency
nitrogen Protein synthesis Manufacture of chlorophyll Promotes normal plant growth Leaves become pale green, yellow, small leaves, thin weak stem and stunted growth
phosphorus Promote root and branch growth Protein synthesis and energy release in respiration Poor growth of roots, leaves and branches Leaves become reddish purple
Potassium Used during photosynthesis and protein metabolism in younger leaves Yellow leaves with dead spots especially at margins and tips
Calcium Promotes normal plant growth and cell wall formation Poor root growth Death of growing regions
Magnesium Manufacture chlorophyll Yellowing of leaves
Sulphur Protein synthesis Stunted growth Yellow patchers on leaves



The Concept of Photosynthesis

Photosynthesis is the process where by green plants manufacture their own food by using light energy produced from the sun. photosynthesis takes place in plants especially in leaves so as to make their own food by the presence of different factors.

FACTORS FOR PHOTOSYNTHESIS/Conditions of photosynthesis

  • Light energy
  • Chlorophyll
  • Water
  • Temperature
  • CO2

CO2 +H2O ——> C6 H12 O6 + H2O +O2 Equation of photosynthesis

CO2 + H2O ——> C6H12O6 + H2O + O2

Carbon dioxide + water——-> glucose +water + oxygen


Photosynthesis is the process of converting solar energy to chemical energy.

6CO2+ 12H2O  —–>   C6H12O6 + 6H2O + 6O2


End products of photosynthesis

Primary products – glucose

By products – oxygen, water


Storage organs in plants

  • Bulbs of onions
  • Corns in yams
  • Rhizomes of ginger
  • Root tubers
  • Stem tubers

Advantages of storage organs

  1. Gives rise to new plants (some)
  2. Source of food (some)
  • Permit survival of plants over dry season
  1. Used for commercial purposes


Factors affecting photosynthesis (rate of)

  1. Light intensity– Light intensity varies from day to day and place good quality. Light enhances the rate of photosynthesis. Very bright light damages the plant due to the strong UV rays. Plants under a shade receive poor quality of light. The best wave lengths are red and blue.
  2. Carbondioxide concentration – the percentage of CO2in the atmosphere is 0.03% in controlled conditions example green house. An increase in CO2 concentration results to an increase in the rate of photosynthesis up to a certain level.
  3. Temperature– photosynthesis is controlledby enzymes.  Enzymes are affected by the changes in temperature.  High temperatures destroys enzymes and very low temperature inactive them.  A rise in temperature by 100C results in the double rate of photosynthesis up to 400  Any further increase in temperature decreases the rate of photosynthesis.
  4. Water– plants require water for various chemical reactions of the cells. It is also a raw material for photosynthesis.
  5. Mineral salts– some irons such as magnesium are constituents of chlorophyll. The availability of those ions will result chlorophyll.
  6. Leaf age– as the leaf ages, chlorophyll breaks down hence the rate of photosynthesis is reduced.


The Structure of the Leaf in Relation to Photosynthesis

The petiole or leaf stalk attaches the leaf to the branch or stem. It keeps the lamina in position that will enable it to get a maximum amount of sunlight. The lamina has a large surface area, thus maximizes the absorption of light energy and carbondioxide. The lamina is also thin so that carbondioxide and light energy diffuse over a shot distance to reach cells.

The mid rib and veins contain xylem and phloem. Xylem vessels transport water and mineral salt to the leaf. Phloem vessels transport manufactured food to other parts of the plant.

The Process of Photosynthesis

It takes place inside the cell organelles known as chloroplasts. Photosynthesis takes place in two stages the light stage and the dark stage.

The Importance of Photosynthesis in the Real Life Situation

  1. Energy
  2. Oxygen production
  • Production of food
  1. Balance CO2 and O2in the atmosphere
  2. All organisms which are heterotroph depend on autotrophas source of food.
  3. Living organisms depend on oxygen for their aerobic respiration produced during photosynthesis
  • Photosynthesis convert light energy into chemical energy which is used by other organisms
  • Humans depend on photosynthesis for the energy containing fossil fuel which have developed over a millions of year.

The Basic Food Substances

  • Carbohydrates
  • Protein
  • Lipids


Food Processing, Preservation and Storage

The Concept of Food Processing , Food Preservation and Food Storage

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

Some of activities involved in food processing are;

  1. Picking, sorting and washing fruits and vegetables
  2. Cooking by boiling steaming, roasting backing or frying
  3. Converting raw materials into other products for example making cheers from milk or sugar from sugar cane


Food preservation refers specifically to the methods of food processing that areused to prevent food from spoiling or going bad

Methods of food preservation

  1. Keeping out micro organisms for example by canning or bottling
  2. Using high temperature to kill microorganisms that cause spoilage eg.By pasturalization and boiling
  3. Using very low temperature to slow down the growth of microorganisms for example refrigeration.
  4. Irradiation which is by using radiations such as gamma rays to kill micro organisms
  5. Eliminating the moisture that is needed for growth of micro organism for instance by drying, salting, smoking etc
  6. Adding chemicals such as salt sugar, carbon monoxide to preventphysical changes in food


Refers to the methods used to keep or reserve of food for future use. Food storage can be done on a small scale at the family level for example in a family granary or food store. Or large scale for large populations e.g in government stores of grains.

The Importance of Food Processing, Preservation and Storage

  1. prevents wastage of food
  2. it saves money by preventing spoilage of food
  • maintains the quality of food
  1. prevents the growth of micro organisms that can cause illness
  2. improve the flavor of food
  3. removes armful toxins and micro organisms from food
  • makes food available even where they are not in season
  • enables transportation of delecate and perishable food such as milk andfruit over long distance

Traditional and Modern Methods of Processing, Preserving and Storing Food

Differentiate between traditional and modern methods of processing, preserving and storing food

They are two methods of food processing and preservation which are;

  1. traditional methods
  2. modern methods


These are methods used to process and preserve food which doesn’t require the use of technology.

These are methods used to process and preserve food which doesn’t require the use of technology. The following are the traditional ways.


It involves additional of substances such as salt, sugar, spaces and vinegar to animal foods, moist meat and fish. Curing removes water making it unavailable for the growth of microorganism it also improve the taste of food. Sausages, be con and curried beef are made by curing meat.


Thus method is used to preserve rice, maize, cloves, banana, beans, peas, meat, fish etc. Here food is left for long time on the sun in order to reduce its moisture content. Reducing the amount of water in food discourages the growth of microorganisms. Some food such as banana and cassava are cut into small pieces to fasten the process.


Smoking is the traditional method which is used to reduce moisture content of food to prevent growth of microorganisms. Grains, meat, fish can be dried slowly over the smoking wood fire


Traditional methods of cooking are simple and include boiling, steaming, backing, in hot hash and roasting.

These processes help to soften food, improve flavor and preserve food. Example potatoes, bananas, and maize can be boiled before being dried.


Dry grains are stored in granaries which are usually raised above the ground.The grains are sometimes mixed with neem leaf ash or groundnuts oil to further prevent attack by microorganisms.Granaries keep grains safe from insects rodents and birds. Example harvested yams, potatoes and cassava can be stored in large pits in the ground after drying.



  • They are simple and they can be done by most people
  • They use locally available materials and simple technology thus keeping cost slow
  • No harmful chemicals are added to the food
  • Curing and smoking add distinct flavor.
  • Most methods do not destroy nutrients


  1. Food can be preserved and stored for the limited period of time
  2. They are manual and thus difficult to apply on a large scale
  3. Traditional methods are highly limited in the variety of food that can beprocessed preserved and stored.




Is the temporary storage of food at low temperature of up to 4 centigrade in order to slow down the growth of microorganisms. Freezing involves storing food at very low temperatures in order to stop the growth of microorganisms frozen food can be kept for months. Food that can be refrigerated include milk, fresh fruits, vegetables, juice and butter. Freezing is mostly used for meat, fish, fruits and vegetables.


Thus method of preservation was named after its inventor Louis Pasteur.

It involved heating food to a very highest temperature for a short time in order to kill the micro organisms that can cause spoilage. Pasteurization maintains the nutrients content and flavor of food. Examples of food that can be pasteurized are milk and fruity juice.


In this method, food is preserved by heating it in airtight vacuum, sealed bottles or cans. The container is filled with food then the air is pumped out to form a vacuum. The container is sealed and heated to kill microorganisms and enzymes but not enough to overcook the food. Food that can be bottled or canned include tomatoes, fruits, juice, beef, fish and packed beans. Bottled or canned food can be kept for months or even years.


This method involved the use of chemicals such as sodium benzoate, sodium chloride, and vinegar are added to food to slow down the growth of microorganisms. This is commonly done to pressure fish and meat


Food is dried by using either hot blast of air from a vacuum drayer. After drying the food is then sealed in moisture –proof containers.


Is the modern method which involve the use of rays of energy to stop the growth of microorganisms in stored food. Example in onions, beans and potatoes. This makes food last longer. It also prevents sprouting in onions and potatoes.


  • Food can last for many months and even a year
  • Modern methods can process, preserve, and store large variety of food.
  • They are advanced technology bused in fast and can handle huge quantities offood.


  1. The chemicals used can be harmful if eaten in excess
  2. These advanced technology involve means where they are used only in certain areas for instance refrigeration requires electricity.
  3. The process used for example canning and pasteurizing require special skills.
  4. Sometimes nutrients are lost thus lowering the nutritional value of food



Less costiful High cost iful
It involves the use of low technology It involves the use of advanced technology
It processes and preserves food for alimited amount of time Preserves food for months and evenyears
It uses local materials to process and preserve food It is used by most people It uses chemicals to process and preserve foodIt is used by few people
It select type of food to be processed and preserved It is not selective


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