B4. Nutrition

Question 1

List the chemical elements that make up:

• carbohydrates
• fats
• proteins

Answer 1

• Carbohydrates: carbon, hydrogen, oxygen
• Fats: carbon, hydrogen, oxygen
• Proteins: carbon, hydrogen, oxygen, nitrogen and sometimes sulphur

Question 2

Define ‘nutrition’

Answer 2

Taking in of nutrients which are organic substances and mineral ions, containing raw materials or energy for growth and tissue repair, absorbing and assimilating them.

Question 3

Describe tests for:

• starch
• reducing sugars
• protein
• fats

Answer 3

• Starch: iodine solution (positive: blue / black)
• Reducting sugars: Benedict’s solution to boil (positive: red / orange -> blue -> green -> yellow -> orange shows you how much sugar is present, cools to form precipitate.)
• Protein: biuret solution (positive: purple, violet or lilac)
• Fats: dissolve food in ethanol and add distilled water (positive: white emulsion)

Question 4

State the principle sources of:

• carbohydrates
• fats
• proteins
• vitamins (C and D only)
• mineral salts (calcium and iron only)
• fibre
• water

Answer 4

• Carbohydrates: rice, potatoes, bread, yams, sugar and honey
• Fats: butter, cheese
• Proteins: meat, fish, milk, nuts
• Vitamin C: citrus fruits, cabbage, tomato, mango
• Vitamin D: milk, cheese, egg yolk, fish-liver oil
• Calcium: milk, cheese, fish
• Iron: red meat, liver, kidney, green veg
• Fibre: cereal, fruit, vegetables
• Water: drinks, fruits

Question 5

Describe the importance of:

• carbohydrates
• fats
• proteins
• vitamins (C and D only)
• mineral salts (calcium and iron only)
• fibre
• water

Answer 5

• Carbohydrates: source of energy
• Fats: source of energy; insulation against heat loss; constituent of cell membranes and some hormones
• Proteins: growth; tissue repair; constituents of enzymes, some hormones, antibodies, haemoglobin, hair and nails
• Vitamin C: needed to make healthy skin and gums
• Vitamin D: needed to maintain hard bones; helps in absorption of calcium from the small intestine
• Calcium: needed to form healthy teeth and bones; and for normal blood clotting
• Iron: needed for formation of haemoglobin in red blood cells
• Fibre: it adds bulk to food passing through the intestines; helps to maintain peristalsis
• Water: forms blood & cytoplasm; helps to transport nutrients; removal of waste as urine ; cooling of body by sweating; enzymes only work in solution

Question 6

Describe the deficiency symptoms for:

• vitamins (C and D only)
• mineral salts (calcium and iron only)

Answer 6

• Vitamin C: scurvy - bleeding under skin & bleeding gums
• Vitamin D: rickets - soft bones that become deformed.
• Calcium: rickets; slow blood clotting
• Iron: anaemia - tiredness and lack of energy

Question 7

Describe the use of microorganisms in the manufacture of yoghurt

Answer 7

➢ The milk is heated to 700C and then cooled to kill organisms in the milk which might ferment it making unpleasant tasting substances;
➢ Bacteria (Lactobacillus) is added to warm milk;
➢ Bacteria uses the sugar of milk (lactose) and converts it to lactic acid (fermentation) for energy;
➢ Lactic acid lowers the pH of the milk;
➢ This affects the proteins in the milk which coagulate forming clumps;
➢ The milk separates out into clumps called curds and the liquid called whey;
➢ The temperature is then reduced to 50C to prevent further bacterial action.

Question 8

Define ‘photosynthesis’

Answer 8

The fundamental process by which plants manufacture carbohydrates from raw materials using energy from light.

Question 9

How is light energy taken in?

Answer 9

Chlorophyll traps light energy and converts it into chemical energy for the formation of carbohydrates and their subsequent storage.

Question 10

State the word equation for photosynthesis

Answer 10

Carbon dioxide + water -(+light)-> glucose + oxygen

Question 11

State the balanced symbol equation for photosynthesis

Answer 11

6CO2 + 6H20 -> C6H12O + 6CO2

Question 12

Describe the intake of carbon dioxide and water by plants.

Answer 12

Carbon dioxide:

• Through the stomata in the leaves -> diffusion
• Behind stomata is an air space which connects up with other air spaces between the spongy mesophyll cells
• CO2 then diffuse through the cell wall and cell membrane into the chloroplasts

Water:

• Absorbed into roots by osmosis and transported to the leaf through xylem vessels
• Travels from xylem vessels to the mesophyll cells by osmosis