Chemistry For HSC Part 2 - Chapter No.10 - Questions And Answers

Go To Index

Chapter No.10
CHEMISTRY OF LIFE
Questions And Answers

By Sir Asif Izhar (Anees Hussain)

CONTENT

1. Biochemistry
2. Food and Nutrition
3. Carbohydrates
4. Amino Acid
5. Proteins
6. Lipids
7. Enzymes
8. Vitamins
9. Digestion of Food
10. Absorption or Assimilation

Q.1: Define biochemistry?
Ans: BIOCHEMISTRY:
Chemistry of life, in short written as Biochemistry (Bio = Life + Chemistry). It is a branch of Chemistry which deals with the study of chemical and physical processes, by means of which the chemical compounds such as vitamins, lipids, carbohydrates proteins and nucleic acids are transformed into one another by the cell itself (occur in living things) in order to maintain its organized structure and activities.

OR 

"The branch of chemistry which deals with the study of chemicals and physical processes taking place in the body during food intake is called Biochemistry or the Chemistry of Life".

Q.2: What do you know about Food and Nutrition? Explain the balanced and unbalanced diet. Illustrate the effects of unbalanced diet.
Ans: FOOD AND NUTRITION:
Food and Nutrition is a field of biochemistry which deals with the Nutrient and caloric requirement of the living body. It deals with the effect on growth and metabolism of the living system arising from the imbalanced diet.

PURPOSE OF FOOD:
The food is required by the body to achieve three purposes:

1. Energy in the form of calories
2. Growth and maintenance of tissues
3. Regulation of body processes

CLASSIFICATION OF FOOD:
Food and nutrients are classified into six groups, as:

1. Carbohydrates
2. Lipids and fats
3. Proteins
4. Vitamins
5. Minerals
6. Water

BALANCED DIET:
For healthy performance, each day the diet must supply the body with:

1. Adequate calories
2. Vitamins
3. Mineral salts
4. Water

Such foodstuff in a diet can cover all the above needs of the living system and such diet is known as a balanced diet.

MALNUTRITION OR BAD NUTRITION OR UNBALANCED DIET:
A malnutrition or bad nutrition is a state in which body is poorly nourished due to long use of a diet which lacks in essential elements and becomes subject to deficiency diseases and other disorders. Such diet is also known as unbalanced diet.

EFFECT OF UNBALANCED DIET:
The statistical survey data of food and nutrition showed that 30% of population was suffering from the diseases of malnutrition (Faulty nutrition).

• Diseases like decayed and crocked teeth
• Bone deformation
• Lack of mental alertness and
• Under weight

were real outcome of the unbalanced food and diet.

Q.3: Illustrate of elements of nutrition.
Ans: ELEMENTS OF NUTRITION:
The essential elements of nutrition are:

• Adequate calories
• Vitamins
• Mineral salts
• Water

Our body needs these elements in our diet, daily for healthy performance. Such diet is known as a balanced diet.

(A) CALORIES:
The energy and the fuel value of foods is measured in calories and is define as:

"The amount of heat required to raise the temperature of 1 Kg of water by 1°C."

It is denoted by capital C or kilo calories (kcal).

Main Source Of Calories:
Almost all the physiological activities of the body are energy dependent and this comes from the break down of carbohydrates, fats and proteins, the three major nutrients. Carbohydrates and to lesser extent fats are the cheaper sources of the calories than the proteins.
The quantity of food needed to provide required calories for an individual could be calculated as follows:

Carbohydrates give 4 calories per gram

Fats give 9 calories per gram

Proteins give 4 calories per gram

(i) Carbohydrate intake:

• Carbohydrates are the cheap and an efficient source of energy for animals.
• Carbohydrates furnish 60-80% of the total calories intake.

Daily requirement:

• A minimum quantity of 5g of carbohydrate per 100 K cal of the total diet is necessary to prevent the development of ill-effects of fasting or of high fat and protein diet.

Main sources: of carbohydrates are:

• cereals or grains-wheat, maize, rice, oats, barley, sorghum and millet.
• roots and tubers-Potatoes, sweet potatoes.
• sugar, honey, beat roots, fruits and sugar-cane.

(ii) Fat Intake:

• Fats also provide energy double than that of proteins or carbohydrates and therefore they serve an effective source of energy store in both animals and plants (seeds).
• The available fat sources also provide the fat soluble vitamins.

Daily requirement:

• The minimum daily requirement of appropriate fats varies from 15-25 g per day depending upon the intake of calories from other sources of diet.
• The level of recommended fat can go up to 100 g/day, for calorific purposes.
• 35% of the total calories required per day, are acquired from fats containing 10% poly unsaturated fatty acids and 10% saturated fatty acids.

Main sources of Fats are:

• Animal sources -Tallow, butter
• vegetable source - Oils from seeds of all kinds of sunflower, cotton seed, coconuts, soybean and mustard.

(iii) Protein Intake:

• When the required calories per daily an energy supplying diet are not adequately met by the carbohydrates or fats, the proteins do furnish energy.
• Protein as nutrient,is important for the maintenance of body than to supply calories.
• Proteins can also supply some amino-acids which like glucose function as an energy donor, that fat can not do so. The energy deficiency is always accompanied by the symptoms of proteins deficiency and results in certain ailment.

Daily requirement:

• It varies from body to body

 Main sources of protein are:

• Meat
• Milk and eggs
• Pulses, beans, peas, lentil
• Edible seeds, nuts and oil containing fruits.

(B)VITAMIN INTAKE:

• Vitamins are necessary food factors which act as stimulant 
• Chemically vitamins are organic in nature and are classified according to their solubility as:
  (a) fat soluble vitamins such as A, D, E, K
  (b) water soluble vitamins such as B-Complex and C.

Daily requirement:

• They are required only in small amounts in the range of milligrams per day.
• Water soluble vitamins are more readily absorbed than the fat soluble and are not stored in the body thus taken in excessive amounts than the body requirements and are excreted.
• Fat soluble vitamins are stored in large amounts, mainly in the liver hence need not be taken daily.

Main Sources: of vitamins are:

• Milk, egg
• green vegetables
• cereal grains and wheat grains

Side Effects Of Excess Vitamin Intake:

• Repeated intake in excess amounts of fat soluble vitamins causes severe toxic effects.
  For instance vitamin A is required for normal growth, for vision in dim light and for keeping skin and the mucous linings of the body healthy. If it is taken as little as 7.5 mg per day over a period of 20-30 days.
  The excess of vitamin A will cause an increase in cerebral spinal fluid pressure, headaches and irritability.
• To prevent wasting of many vitamins, the rigorous treatment of washing or refinement of cereal grains or cooking should be avoided.

(C) MINERAL INTAKE:

• Inorganic elements present in diet do not supply any energy / calories. Their role in the diet is equally important for maintenance, building and rebuilding of tissues.
• Only 23 elements have been observed to be essential for life.
  Out of these, eleven are non metals (C,H, 0, N, S, P, Cl, F, 1, B, Si) and
  The rest are metals (Ca, Na, K, Mg, Fe, Cu, Zn, Co, Al, Ni, Mo, Se).

Daily requirement:

• Every element has own range.
• Requirement of the minerals varies from 100 mg or more, to a few micro grams per day. The elements required in microgram, are Cu²⁺, Co²⁺, Ni²⁺, Al³⁺ etc.

Main sources: of minerals are:

• Eggs, meat, and cereals are common acid forming foods.
•  Fruits, vegetables and milk are common base forming food.
•  Sugar and fats are among neutral foods.
• Many of these elements are usually found as ions, such as Fe²⁺, Na⁺, K⁺, Mg²⁺, SO₄^2-, Ca²⁺, CO₃^2-, N0_-3^-.

Side effect:
The concentration of these ions present in body are maintained within narrow limits and small variations result in many abnormal biological functions.

Uses:
Among all H, C, N, 0, Na, K, Mg, Ca, S, P are of universal importance, as:

• The minerals are useful to maintain pH, osmotic pressure and act as ion antagonists.
• Bones and teeth require calcium and phosphorus.
• Iron is picked up for the production of hemoglobin and cytochrome system of body.
• Iodine is needed in thyroxine, the hormone of thyroid gland.
• Mineral salts control acid-base balance of the body, and as co-factors of the many enzymes and thus activate the metabolic system. 

(D) WATER INTAKE:

• About 70% of the body weight is water, which remains constant. The total water lost per day from the body is being balanced by the water intake per day.

Daily requirement:

• The water requirement of the body per day is about 2.5 to 3 litres which is gained from three different sources mainly fluids, food, and the same amount is being lost through urine, skin (perspiration), lungs (expiration) and faeces.

Main sources: of water are

• Ground water
• rivers
• springs

Uses:

• The daily intake of water is the most important item of the diet. Because an individual without food may survive for a month, but without water one can not live more than 15 to 16 days.
• Transportation of different material inside body.
• Regulate body temperature.