Bio f4 chap 3

Question 1

What will happen to the plasma membrane if there is no cholesterol?

Answer 1

• become to fluid
• too permeable to dissolve substances

Question 2

Explain the role of phospholipid and protein in ensuring the permeability of plasma membrane.

Answer 2

• only allow passage for a certain number of substances
• enables / limits the free movement of certain substances
• determines the selectively permeability of plasma membrane

Question 3

Why mineral salts concentration in the roots increased when the oxygen concentration in the solution increases by 10%?

Answer 3

• active transportation
• involves usage of energy
• more energy is generated
• root cells carry out more cellular respiration using oxygen

Question 4

Why do hawkers spray water on their fruits and vegetables?

Answer 4

• water diffuses into cells via osmosis
• vacuole expand
• cell sap within vacuole pushes cytoplasm and plasma membrane to cell wall
• cells become turgid

Question 5

Why green chili is preserved using vinegar and sugar?

Answer 5

• concentrated sugar solution is hypertonic to the cell sap of chili
• water diffuses out of the chili via osmosis
• chili undergoes dehydration
• bacteria unable to survive without water
• pickled chili can be kept for long time
• vinegar reduces pH
• bacteria cannot live in acidic environment

Question 6

Advantages and disadvantages of pickles

Answer 6

Two advantages:
* Prevents wastage due to spoilage
* Preserved pineapples last longer

Two disadvantages:
* contain too much sugar
* Nutrients are damaged by oxidation during
preparation, causes low nutrients

Question 7

Why cosmetic cream containing liposome is said to be more effective in skin care?

Answer 7

• liposome is a vesicle that contains aqueous solution encased in a membrane made up of phospholipids
• liposome is used to transport active substances in cosmetics into the epidermal layer of the skin
• liposome transports active substances to the lower epidermal layer so the active substance can be more effective
• without liposome, active substance will be easily oxidised (vitamin C)

Question 8

Explain why the suggested carbohydrate concentration of drinks for gymnast is 1-3%, middle distance runner 6-8% and footballer 10-12%

Answer 8

Gymnast:
- hypotonic
- hydrate body
- replace water lost
- only needs small amount of carbohydrate to provide energy

Moderate distance runner:
- isotonic
- replace water lost
- provide some energy

Football:
- hypertonic
- provide instant energy
- high usage of energy during training
- replenish glycogen storage in muscles