Chapter 15: Biochemistry

1. Encircle the correct answer.

(i) In small village children frequently suffered from different infectious diseases due to weak immune systems. Which major nutrients were lacking in their food?

(a) Amino acids

(b) Carbohydrates

(c) Proteins

(d) Lipids

Answer: (c) Proteins

Explanation: Proteins are essential for building and repairing tissues and for a strong immune system. Antibodies, which fight infections, are proteins. A deficiency of protein leads to a weakened immune system and increased susceptibility to infectious diseases.

(ii) Which of the following food components are rich in fats:

(a) Rice and maize

(b) Pulses and wheat

(c) Milk, egg, and beans

(d) Cheese, butter, and oil

Answer: (d) Cheese, butter, and oil

Explanation: Fats (lipids) are found in high concentrations in dairy products like cheese and butter, and in cooking oils. Rice, maize, pulses, and wheat are rich in carbohydrates.

(iii) Potatoes, cereals, beans, pulses, and oats are rich in:

(a) Proteins

(b) Carbohydrates

(c) Amino acids

(d) Fats

Answer: (b) Carbohydrates

Explanation: Potatoes, cereals, beans, pulses, and oats are staple foods rich in carbohydrates (starch). They are the primary source of energy in the diet.

(iv) What is a bond between amino acids called?

(a) Ionic bond

(b) Acidic bond

(c) Peptide bond

(d) Hydrogen bond

Answer: (c) Peptide bond

Explanation: A peptide bond is a covalent bond formed between the carboxyl group of one amino acid and the amino group of another amino acid, with the removal of a water molecule.

(v) The major function of carbohydrates includes:

(a) Storage

(b) Structural framework

(c) Defense system of body

(d) Messenger

Answer: (a) Storage

Explanation: Carbohydrates serve as a major source of energy and are stored in the form of glycogen (in animals) and starch (in plants). Structural framework is a function of proteins. Defense is a function of proteins (antibodies). Messenger is a function of hormones (often proteins or lipids).

(vi) Which of the following disorders is NOT caused by the deficiency of proteins?

(a) Weight loss

(b) Muscle fatigue

(c) Loss in muscle strength

(d) Constipation

Answer: (d) Constipation

Explanation: Constipation is primarily caused by a lack of dietary fiber (roughage) and water, not by protein deficiency. Protein deficiency causes weight loss, muscle fatigue, and loss of muscle strength.

(vii) Foods containing starch and carbohydrates are important because:

(a) They make your bones strong.

(b) They stop you from getting overweight.

(c) They are easy to cook.

(d) They give you energy.

Answer: (d) They give you energy.

Explanation: Carbohydrates are the body's primary and quickest source of energy. They are broken down into glucose, which is used by cells to produce ATP.

(viii) Meat, fish, and other alternatives provide the following important nutrients:

(a) Carbohydrates

(b) Protein

(c) Lipids

(d) Sugar

Answer: (b) Protein

Explanation: Meat, fish, eggs, and legumes are rich sources of protein, which is essential for growth, repair, and maintenance of body tissues.

(ix) Which nutrient builds, maintains and repairs body tissues and cells?

(a) Carbohydrates

(b) Protein

(c) Lipids

(d) Water

Answer: (b) Protein

Explanation: Proteins are the building blocks of the body. They are essential for the growth, repair, and maintenance of all body tissues and cells.

(x) Mariam's doctor told her that she is facing shortage of blood and have anemia. What nutrients are lacking in Mariam's diet?

(a) Carbohydrates

(b) Protein

(c) Lipids

(d) Water

Answer: (b) Protein (Note: Anemia is most commonly caused by iron deficiency. However, protein is also essential for hemoglobin synthesis. Since iron is not an option, protein is the best answer among the choices.)

2. Give short answer.

(i) Give three reasons why living organisms need food.

Answer: Living organisms need food for:

1. Energy: Food provides energy for all life processes like movement, growth, and reproduction.

2. Growth and Repair: Food provides raw materials (proteins, minerals) for building new cells and repairing damaged tissues.

3. Regulation: Food provides vitamins and minerals that regulate body processes and protect against diseases.

(ii) What is a balanced diet? What is the importance of balance diet?

Answer: A balanced diet is a diet that contains the proper proportions of carbohydrates, proteins, fats, vitamins, minerals, and water necessary for maintaining good health. Its importance includes:

Optimal Growth: Provides all nutrients needed for proper physical and mental development. Disease Prevention: Prevents deficiency diseases (e.g., scurvy, rickets). Energy: Ensures adequate energy for daily activities. Homeostasis: Maintains proper body functions and weight.

(iii) State four functions of proteins. Give one example to illustrate your answer.

Answer: Four functions of proteins:

1. Structural: Collagen and keratin provide structure to skin, hair, and bones.

2. Catalytic: Enzymes (e.g., amylase) speed up biochemical reactions.

3. Transport: Hemoglobin transports oxygen in the blood.

4. Defense: Antibodies fight infections. Example: Hemoglobin is a protein that carries oxygen from the lungs to tissues.

(iv) Suggest two major foods a mother could give to her growing child? And why.

Answer: Two major foods for a growing child:

1. Milk: Rich in protein, calcium, and vitamins, essential for bone growth and tissue development.

2. Eggs: Excellent source of high-quality protein, vitamins, and minerals for overall growth. These foods provide the necessary nutrients for rapid growth and development during childhood.

(v) Carbohydrates are a major source of energy. Define the statement.

Answer: The statement means that carbohydrates are the body's primary and most readily available fuel. When consumed, they are broken down into glucose, which is oxidized during cellular respiration to produce ATP (adenosine triphosphate), the energy currency of the cell. This ATP powers all cellular activities. Without carbohydrates, the body would have to rely on less efficient sources like fats and proteins for energy.

(vi) Fatima has fond of junk food like French fries, burgers, and pizza. What will happen if Fatima only eats junk food? What should she add to her routine food?

Answer: If Fatima only eats junk food, she will likely suffer from:

Obesity: Due to high calories, fats, and sugars. Malnutrition: Lack of essential vitamins, minerals, and fiber. Heart Disease: Due to high saturated fats and sodium. She should add fruits, vegetables, whole grains, and lean proteins to her routine food to ensure a balanced diet.

3. What are lipids? How lipids are important to our body?

Answer: Lipids are a group of hydrophobic biomolecules that include fats, oils, waxes, and steroids. They are composed of carbon, hydrogen, and oxygen. Importance:

Energy Storage: Provide a concentrated source of energy (9 kcal/g). Structural Components: Phospholipids form cell membranes. Insulation: Adipose tissue provides thermal insulation. Protection: Cushions vital organs.

Hormone Production: Steroid hormones regulate body processes. Vitamin Transport: Carry fat-soluble vitamins (A, D, E, K).

4. How do you maintain a balanced diet?

Answer: Maintaining a balanced diet involves:

Variety: Eating a wide range of foods from all food groups. Portion Control: Eating appropriate amounts to maintain a healthy weight. Limit Junk Food: Reducing intake of processed foods, sugars, and saturated fats. Hydration: Drinking plenty of water. Regular Meals: Eating at regular intervals. Reading Labels: Being aware of nutritional content. Consulting a Nutritionist: For personalized advice.

5. What percentage of fat is required in a balanced diet? Why is the percentage of fat being lowest in major food components? Justify.

Answer: The recommended percentage of fat in a balanced diet is about 20-35% of total daily calories. The percentage of fat is lowest among major food components because:

High Energy Density: Fats provide more than twice the energy per gram compared to carbohydrates and proteins. Health Risks: Excessive fat intake is linked to obesity, heart disease, and diabetes. Storage: The body can store excess fat, leading to weight gain. Therefore, only a small amount is needed for essential functions.

6. What are the sources and functions of nucleic acids?

Answer:

Sources: Nucleic acids are found in all living cells. Dietary sources include meat, fish, eggs, and legumes. However, the body synthesizes its own nucleic acids from simpler compounds. Functions:

DNA (Deoxyribonucleic Acid): Stores genetic information and transmits it from generation to generation. RNA (Ribonucleic Acid): Involved in protein synthesis (mRNA, tRNA, rRNA) and gene regulation.

7. Imagine you are a nutritionist task to design a meal plan for athletes participating in a marathon. Explain the role of carbohydrates can affect an athlete's performance during the marathon.

Answer: As a nutritionist, I would design a meal plan high in complex carbohydrates (e.g., whole grains, pasta, fruits) for marathon athletes.

Role of Carbohydrates: Carbohydrates are stored as glycogen in muscles and liver. During a marathon, the body relies heavily on glycogen for energy. Effect on Performance: Adequate carbohydrate intake ensures maximum glycogen stores, delaying fatigue and improving endurance. If glycogen stores are depleted, the athlete will experience "hitting the wall" (fatigue, weakness). Meal Plan: Pre-race meal should be high in carbs, low in fat and fiber. During the race, athletes should consume carbohydrate gels or drinks to maintain blood glucose levels.

CONCEPT ASSESSMENT EXERCISE 15.1

1. Differentiate between DNA and RNA.

Answer:

2. Differentiate between proteins and lipids.

Answer:

Make a healthy meal diet plan and also identify food group of each food item.

Answer: (Guide for the project)

Title: My Healthy Meal Plan. Breakfast: Oatmeal with fruits and nuts, a glass of milk.

Food Groups: Grains (oatmeal), Fruits (banana, berries), Dairy (milk), Proteins (nuts).

Lunch: Grilled chicken breast, brown rice, mixed vegetables, and a small salad.

Food Groups: Proteins (chicken), Grains (rice), Vegetables (broccoli, carrots).

Snack: An apple and a handful of almonds.

Food Groups: Fruits (apple), Proteins/Fats (almonds).

Dinner: Baked fish, quinoa, and steamed spinach.

Food Groups: Proteins (fish), Grains (quinoa), Vegetables (spinach).

Hydration: 8-10 glasses of water throughout the day. Visuals: Create a chart or poster showing the meal plan with pictures of each food item and labels indicating their food group.