Revision 11

Which structures are found in bacterial cells but not in animal cells?

• cell membrane and plasmids

• nucleus and cytoplasm

• nucleus and ribosomes

• plasmids and cell wall

Answer explanation

Bacterial cells have structures like plasmids and a cell wall, which are absent in animal cells. Plasmids are small DNA molecules, and the cell wall provides structural support, distinguishing bacteria from animal cells.

The diagram shows a plant cell in a concentrated salt solution.

Which row shows the net movement of water molecules and the effect on the plant cell?

• net movement of

  water molecules - out of cell

  effect on

  the plant cell - becomes turgid

• net movement of

  water molecules - out of cell

  effect on

  the plant cell - becomes flaccid

• net movement of

  water molecules - into cell

  effect on

  the plant cell - becomes turgid

• net movement of

  water molecules - into cell

  effect on

  the plant cell - becomes flaccid

Answer explanation

In a concentrated salt solution, water moves out of the plant cell to balance the concentration. This causes the cell to lose turgor pressure and become flaccid, confirming the correct choice.

The graph shows the effect of pH on the activity of an enzyme.

Which label shows where collisions between enzyme and substrate are the most effective?

• A

• B

• C

• D

Answer explanation

Label C indicates the optimal pH where enzyme activity is highest, leading to the most effective collisions between enzyme and substrate. At this point, the enzyme's active site is best suited for substrate binding.

The diagram shows part of the human digestive system.

Which row identifies structure X, an enzyme secreted by structure X and the action of this enzyme?

• structure X - liver

  enzyme - amylase

  action of enzyme - converts proteins to amino acids

• structure X - pancreas

  enzyme - amylase

  action of enzyme - converts starch to simple sugars

• structure X - liver

  enzyme - protease

  action of enzyme - converts proteins to amino acids

• structure X - pancreas

  enzyme - protease

  action of enzyme - converts starch to simple sugars

Answer explanation

Structure X is the pancreas, which secretes amylase. Amylase's action is to convert starch into simple sugars, making this the correct choice.

What is a function of the large surface area of root hair cells?

• to increase the uptake of mineral ions by active transport

• to increase the uptake of water by active transport

• to decrease the rate of transpiration by diffusion

• to decrease the uptake of oxygen by diffusion

Answer explanation

The large surface area of root hair cells enhances the absorption of mineral ions through active transport, allowing plants to efficiently take up essential nutrients from the soil.

Which row shows how blood is pumped out of the heart to the lungs?

• A

• B

• C

• D

Answer explanation

Row D correctly illustrates the pathway of blood being pumped from the heart to the lungs via the pulmonary arteries, highlighting the essential role of the right ventricle in this process.

The diagram shows part of the breathing system.

Which row identifies structures P, Q, R and S?

• alveolus - P

  capillary - Q

  plasma - R

  red blood cell - S

• alveolus - Q

  capillary - R

  plasma - S

  red blood cell - P

• alveolus - R

  capillary - S

  plasma - P

  red blood cell - Q

• alveolus - S

  capillary - P

  plasma - Q

  red blood cell - R

Answer explanation

The correct identification of structures is based on their roles in the breathing system. P is the alveolus where gas exchange occurs, Q is the capillary that carries blood, R is plasma, and S contains red blood cells.

Which molecule is broken down in aerobic respiration?

• starch

• glucose

• glycogen

• water

Answer explanation

In aerobic respiration, glucose is the primary molecule broken down to produce energy. Starch and glycogen are polysaccharides that can be converted to glucose, while water is a product, not a substrate.

Which statement about consumers is correct?

• They feed on other organisms to get their energy.

• They make their own organic nutrients.

• They only get their energy by feeding on producers.

• They use energy from sunlight for photosynthesis.

Answer explanation

Consumers are organisms that obtain their energy by feeding on other organisms, which includes both producers and other consumers. The correct statement is that they feed on other organisms to get their energy.

Which methods can be used to conserve an endangered species?

• 1, 2 and 3

• 1, 2 and 4

• 1, 3 and 4

• 2, 3 and 4

Answer explanation

To conserve an endangered species, methods such as habitat protection (1), breeding programs (3), and legal protection (4) are effective. Therefore, the correct answer is 1, 3 and 4.