Unit 4 Exam Cards

Question 1

What is the correct sequence of stages in mitosis?

Answer 1

1. Prophase
2. Metaphase
3. Anaphase
4. Telophase

Question 2

Suggest why temperatures below 0 °C or above 40 °C would be unsuitable for most organisms.

Answer 2

Below 0 °C:

• Enzymes are inactive

Above 40 °C:

• Enzymes are denatured - structure of active site changed

Question 3

Why might some scientists disagree with the suggestion that lowering use of fossil fuels will prevent further global warming?

Answer 3

• Carbon dioxide released from fossil fuels - no direct evidence which suggests it causes global warming
• Other fossil fuels such as methane released from other sources like ruminant animals
• Natural phenomena may be involved in global warming such as solar activity or volcanic eruptions
• Past evidence is being used to indicate global warming, and it is not a good indicator of future climates
• Scientists may be biased by working for a company

Question 4

Which mineral ion must be present for plants such as grasses and herbs to grow?

Answer 4

Nitrate ions.

Question 5

Why are lichens and mosses referred to as pioneer species?

Answer 5

They can grow with little to no soil and they break up rock fragments to form soil.

Question 6

Define bactericidal antibiotics.

Answer 6

Antibiotics which kill bacteria by causing the bacteria cells to burst.

Question 7

Define bacteriostatic antibiotics.

Answer 7

Antibiotics which stop bacteria from reproducing by stopping cell division.

Question 8

State two characteristic features of antibodies.

Answer 8

• Antigen binding sites
• Disulphide bridges between peptides

Question 9

Suggest three factors that could influence the rate at which a body cools after death.

Answer 9

• Size of the body
• Humidity
• Air flow

Question 10

Suggest reasons as to why 95% of the light hitting the surface of a leaf is not used by the chloroplasts.

Answer 10

• The light is reflected
• The light may be the incorrect wavelength

Question 11

Outline the light-dependent reactions of photosynthesis.

Answer 11

• Light energy excites 2 electrons from each chlorophyll molecule to a higher energy level
• These electrons leave the chlorophyll by travelling along electron carrier molecules through redox reactions
• The energy lost from the electrons are used in the productions of ATP from ADP in photophosphorylation reactions
• Light energy is used to split water into hydrogen ions, oxygen, and electrons. The electrons are used to replace those lost from the chlorophyll
• The electrons that have passed along the electron transport chain combine with the hydrogen ions and NADP to form reduced NADP

Question 12

Outline the light-independent reactions of photosynthesis.

Answer 12

• Carbon dioxide combines with RuBP (catalysed by RuBISCO) to form a compound which breaks down into 2 3-carbon molecules of GP
• GP is reduced to form GALP using the hydrogen from the reduced NADP and energy from the ATP
• 2 out of every 12 GALP molecules formed are used in the production of hexose which can be converted into other organic compounds
• The 10 other GALP molecules are used to replace RuBP by rearranging to form 6 5-carbon molecules which are converted to RuBP through phosphorylation using ATP for energy

Question 13

Define the term gene mutation.

Answer 13

A change in DNA which from a change of the nucleotides.