Nutrition in humans

Question 1

What is a balanced diet?

Answer 1

A diet that includes the seven essential nutrients in the correct proportions.

Question 2

What are the seven essential nutrients and their functions? (list all 7)

Answer 2

Carbohydrates – (soluble form: glucose)
* Main source of energy

Fats – (Soluble form: 1 glycerol + 3 fatty acids)
* Source and store of energy.
* Provides insulation.
* Protects organs.

Proteins – (Soluble form: amino acids)
* Growth.
* Hormones.
* Enzymes.
* Tissue repair.
* Antibodies.

Minerals
* Iron: Needed to make haemoglobin in red blood cells.
* Calcium: Needed to build bones and teeth.

Vitamins
* Vitamin A: Helps with night vision.
* Vitamin D: Helps absorb calcium and prevents rickets.
* Vitamin C: Supports immunity, keeps gums/skin healthy, prevents scurvy.

Fibres
* Stimulates peristalsis.
* Prevents colon cancer.
* Prevents constipation.

Water
* Acts as a solvent/transport medium.
* Helps cool body temperature.

Question 3

How does age affect diet?

Answer 3

Young people need more proteins (for growth) and carbohydrates (for energy).

Question 4

How does activity level affect diet?

Answer 4

Athletes and construction workers need more carbs (for energy) and proteins (for muscle growth).

Question 5

How does gender affect diet?

Answer 5

• Males need more carbs (higher activity levels).
• Males need more proteins (to maintain muscle mass).

Question 6

Why do pregnant women need more nutrients? (Give 4 examples)

Answer 6

They require additional nutrients for their own needs and foetal development, including:
* Carbs & proteins – For foetal growth.
* Vitamin C – For skin health and immunity.
* Vitamin D & calcium – For bone and teeth formation.
* Iron – For haemoglobin production (to compensate for blood loss due to menstruation).

Question 7

What are the five stages of nutrition?

Answer 7

• Ingestion – Eating food.
• Digestion:

Mechanical digestion: Breaking food into smaller pieces to increase surface area.
Chemical digestion: Using enzymes to break down food into smaller soluble molecules.

• Absorption – Transporting digested food molecules from the small intestine to the bloodstream.
• Assimilation – Using absorbed nutrients in body cells.
• Egestion – Excreting undigested food through the anus.

Question 8

What happens in the mouth? (2 points)

Answer 8

• Mechanical digestion: Chewing food.
• Chemical digestion: Salivary amylase breaks down starch → maltose.

Question 9

What is the function of the oesophagus?

Answer 9

Transports the food bolus from the mouth to the stomach using peristalsis.

Question 10

What is peristalsis?

Answer 10

Alternating contraction and relaxation of muscles in the digestive tract to push food forward.

Question 11

What happens in the stomach? (2 points)

Answer 11

• Mechanical digestion: Churning food.
• Chemical digestion: Pepsin enzyme breaks down proteins → amino acids in an acidic HCl environment.

Question 12

What happens in the duodenum? (2 points)

Answer 12

The duodenum receives:
Bile juice (from liver/gallbladder):
* Neutralises stomach acid.
* Emulsifies fats (breaks them into smaller droplets).

Pancreatic juice (from pancreas):
* Amylase: Starch → Maltose.
* Trypsin: Proteins → Amino acids.
* Lipase: Fats → 1 glycerol + 3 fatty acids.

Question 13

What happens in the Ileum? (2 points)

Answer 13

• Further digestion using enzymes (e.g., maltase: maltose → glucose).
• Absorption of nutrients by villi.

Question 14

How are villi adapted for absorption? (5 points)

Answer 14

• Thin walls → Faster diffusion.
• Dense capillary network → Maintains steep concentration gradient.
• Microvilli → Increase surface area.
• Lacteal vessels → Absorb fatty acids & glycerol.
• Many mitochondria → Provide energy for active transport.

Question 15

What happens in the large intestine? (2 points)

Answer 15

• Absorbs water.
• Faeces stored in rectum and egested via anus.

Question 16

How can you measure the energy content of food? (7 points)

Answer 16

1. Weigh the food sample.
2. Mount the food on a needle.
3. Fill a test tube with 50 cm³ of water, measure initial temperature.
4. Ignite the food sample and place it under the tube.
5. Let it burn completely, measure final water temperature.
6. Calculate energy using:
   Energy = 50 × 4.2 × ΔT
7. Repeat for accuracy.

Question 17

What are the disadvantages of this simple method? (Measuring energy content in foods, 4 points)

Answer 17

Inaccurate calculations and measurments due to:
* Incomplete combustion due to lack of oxygen.
* Heat loss to surroundings.
* Uneven heat distribution in water.
* Sample transfer must be fast to retain heat.

Question 18

How does a calorimeter improve accuracy? (4 points)

Answer 18

• Provides oxygen for complete combustion.
• Enclosed space reduces heat loss.
• Copper pipe efficiently transfers heat to water.
• Stirrer ensures even heat distribution.