Alevel

Question 1

Plant growth requires the production of new xylem cells.

Describe how new xylem cells are produced.

Answer 1

produced in meristems by differentiation of the stem cells

Question 2

Suggest why Hydra plant reproduces asexually when conditions are favourable.

Answer 2

offspring produced can be produced rapidly in large number and all have same adaptations

Question 3

Suggest and explain adaptation that is likely to be present in these sperm cells.

Answer 3

acrosome to penetrate the egg
lots of mitochondria for energy

Question 4

Show the main differences in structure between glucose and starch.

Answer 4

Glucose -
monomer
monosaccharide
no glycosidic bond

Starch -
polymer
polysaccharide
glycosidic bond

Question 5

Carbohydrates contain only the elements carbon, hydrogen and oxygen.

Polypeptides contain carbon, hydrogen, oxygen and nitrogen.

Name one other element present in polypeptides.

Answer 5

Sulfur

Question 6

Creatine kinase (CK) is an enzyme that catalyses reactions in heart muscle.

Suggest why high levels of CK in the blood indicate that a person may have had a heart attack.

Answer 6

creatine kinase is an intracellular enzyme, presence in blood indicates damage to the heart

Question 7

Explain why the oncotic pressure of the blood depends only on the concentration of large plasma proteins.

Answer 7

large plasma proteins cannot pass through capillary wall

Question 8

Explain blood glucose levels (negative feedback loops)

Answer 8

When blood glucose levels are high, beta cells detect, and insulin is produced so that it can turn glucose into glycogen to be stored for later.
When blood glucose levels are low, alpha detect, and glucagon is produced so that glycogen can turn into glucose by the liver

Question 9

What is the final electron acceptor in the light dependent stage of photosynthesis

Answer 9

NADP

Question 10

Suggest and explain the function of DCPIP in photosynthesis practicals

Answer 10

DCPIP acts as the final electron acceptor instead of NADP

Question 11

Describe how new xylem cells are produced

Answer 11

Produced in meristems by differentiation

Question 12

When doing a potometer practical, what precaution is needed

Answer 12

Ensure screw clip is closed to prevent entry of water whilst measuring

Cut shoot slanted to ensure continuous column of water

Question 13

Explain why the oncotic pressure of the blood depends only on the concentration of large plasma proteins

Answer 13

Too large to fit through the pores so left in the blood
Imbalance of large plasma protein between blood and tissue fluid results in oncotic pressure.

Question 14

What is the most important process in determining the overall body plan of an organism

Answer 14

Mitosis

Question 15

Define species richness

Answer 15

The number of species in an area

Question 16

Explain why some regions of DNA can be described as non coding

Answer 16

Not present in the mature mRNA and cannot be translated

Question 17

Evaluate the treatments for type 1 diabetes that have been used in the past as well as current and potential future treatments (6)

Answer 17

In the past insulin was gained from animal pancreas, and this was advantageous as it kept people alive however there was a high production cost and ethical issues as animal products were involved.

Currently, genetically modified bacteria is used. It is much purer, overcomes ethical issues, has a lower production cost and is easier to use. However side effects can occur, and the routine is difficult to understand at first - not user friendly.

Potential future treatments, is transplants of pancreas this means no need for insulin injections, and improved quality of life however it is initially a high cost and needs a donor which can take a long time.

Question 18

Explain how glucose produced in photosynthesis is translocated to parts of the plant where glucose is metabolised or stored. (6)

Answer 18

Phloem loading -
Glucose is converted to sucrose

Mass flow - The pressure difference causes mass flow where sucrose moves from source to sink

Phloem unloading.
Diffusion of sucrose
sucrose is converted back to glucose

Question 19

What is cofactor for carbonic anhydrase

Answer 19

Zn 2+

Question 20

Name and define two other levels of biodiversity

Answer 20

Habitat biodiversity - number of different habitats
Species biodiversity - richness and evenness of a species

Question 21

Describe how oncotic pressure is established

Answer 21

Plasma proteins are too large to leave the capillary
creates a low water potential in the capillary
water moves by osmosis down the water potential gradient into capillary

Question 22

Explain the role of meristem tissue in a stem.

Answer 22

Source of undifferentiated cells for growth
Can differentiate into other cells

Question 23

Name one potential use of stem cells in medicine

Answer 23

Medical research
Repair of damaged tissue

Question 24

explains why plants need a vascular system to support amino acid synthesis

Answer 24

To transport nitrates to the leaves using xylem tissue

Question 25

Outline how ATP is produced in mitochondria by chemoiosomosis

Answer 25

H+ ions flow down a concentration gradient from inter membrane space to matrix
Energy provided to join ADP and Pi to form ATP