Bio f4 chap 7

Question 1

Give five examples of the necessity of energy in a metabolic process.

Answer 1

• maintaining body temperature at 37
• muscle contractions to enable movement
• cell division
• absorption of digested food through active transport
• synthesis of lipids, hormones, proteins and enzymes

Question 2

Explain how humans, animals and plants acquire glucose to produce energy

Answer 2

• in humans and animals (breakdown of carbohydrates)
• plants (photosynthesis)

Question 3

Suggest another substrate apart from glucose that can be used by cells for cellular respiration

Answer 3

• fructose
• galactose
  (monosaccharides)

Question 4

State where the process of fermentation usually occurs

Answer 4

• human muscle cells
• some bacteria
• yeasts
• plants

Question 5

Give three examples of microorganisms and food produced by the fermentation process.

Answer 5

Organism: Saccharomyces
Product of fermentation: carbon dioxide, ethanol
Example: wine, beer

Organism: Aspergillus
Product of fermentation: lactic acid
Example: soy sauce

Organism: Acetobacter
Product of fermentation: Acetic acid
Example: vinegar

Question 6

While helping your father to cut grass at the farm, you come across a snake. Terrified, you run away from the snake. Explain the cellular respiration that takes place in the muscle cells of you legs.

Answer 6

• the lungs and blood supply are unable to supply oxygen quickly enough to meet the demands of the muscles to produce ATP
• muscle cells undergo fermentation, ATP produced without oxygen
• produces lactic acid

Question 7

The uses of alcohol fermentation products

Answer 7

ethanol: beer and wine
CO2: breadmaking to help the dough rise

Question 8

A 100-metre sprinter usually holds his breath while running compared with a long-distance runner. After running, the sprinter needs seven litres of oxygen to remove the lactic acid in his muscle cells. Explain this difference between the sprinter and the long-distance runner.

Answer 8

• By doing so, the runner uses existing oxygen efficiently.
• However, lactic acid is accumulated because the oxygen supply to the muscles is insufficient.
• On the other hand, long distance runners who run at a slower speed are able to dispose off the lactic acid accumulated in the early stages of running.
• Long distance runners cannot hold their breath because lactic acid accumulation causes rapid muscle fatigue.
• As such, long distance runners need to breath throughout the race.

Question 9

Why energy is required in metabolic processes

Answer 9

• maintain body temperature at the optimum temperature of 37
• for division as well as growth and development of cells

Question 10

Why yogurt can spoil if it is not kept in the refrigerator

Answer 10

• the sugar in milk is oxidised by bacteria such as Lactobacillus and Streptococcus into lactic acid
• solidifies the milk and produces a sour taste until curd is formed
• when kept in the fridge, low temperature controls bacterial activity from reproducing and spoiling the product
• if kept at room temperature, the curd will spoil as bacteria will continue to grow and oxidise the milk sugar

Question 11

How sodium bicarbonate or baking soda increase muscle efficiency during intense activities that involve muscle fermentation.

Answer 11

• baking powder has a high pH
• neutralise the lactic acid produced by muscles during exercise
• increases muscle efficiency because lactic acid causes muscle fatigue

Question 12

How to activate yeast to make bread?

Answer 12

• add a little lukewarm water into the dry yeast
• activate the dry yeast which is in a dormant state when its environment is dry
• activated yeast will undergo respiration by breaking down the carbohydrates in the flour and releasing carbon dioxide
• Co2 causes the bread to expand and rise