Biology Paper 2 Mistakes

Question 1

) Light affects gas exchange in leaves. (Lines 19 and 20)
Describe an experiment that shows how the net gas exchange from a leaf varies with light intensity

Answer 1

Question 2

Stomata also have a role in water transport in the plant.
Explain the role of stomata in water transport

Answer 2

• water loss / transpiration / evaporation / diffusion (through
  stomata) / (set up) transpiration stream
• draws water up from roots / up stem / up xylem / into leaf /
  creates a (water potential) gradient

Question 3

Explain the effect of changing pH on an enzyme-controlled reaction

Answer 3

Question 4

Blood plasma contains much glucose, but urine normally does not.
Explain what happens to glucose in the kidney.

Answer 4

Question 5

Mutation can cause changes in the enzymes produced during protein synthesis.
State what is meant by the term mutation

Answer 5

(a rare random) change to DNA / change to gene /
change to genetic material

Question 6

Explain the different effects that a single base mutation can have on transcription and translation and the production and activity of an enzyme. (5)

Answer 6

Question 7

Answer 7

V nitrogen fixation
X nitrification
Y denitrification

Question 8

Describe the changes within a river due to an increase in nitrate levels

Answer 8

Question 9

Describe how stem cells are different from other cell types

Answer 9

• undifferentiated / unspecialised
• and can become different cell types
• can continue to divide / continue to
  multiply

Question 10

Stem cells from a donor can be used for stem cell therapy.
- Human blood cells are produced in bone marrow.
- Explain how using stem cells from the bone marrow enables doctors to treat a number of different blood conditions.

Answer 10

Question 11

One type of stem cell transplant uses a patient’s own stem cells.
They can be used if the patient is producing enough healthy bone marrow cells.
These cells can be collected, frozen and stored for later use.
Explain the advantage of using the patient’s own stem cells rather than using stem cells from a donor.

Answer 11

Question 12

Explain why reducing leaf temperature reduces transpiration rate

Answer 12

An explanation that makes reference to two of the following
points:
 lower temperature reduces (kinetic) energy
 water molecules move less
 less diffusion / evaporation

Question 13

Describe the role of one named mineral ion in plant growth.

Answer 13

• nitrate for amino acids / protein
• magnesium for chlorophyll / chloroplasts

Question 14

Describe how water is transported from the soil to the leaves in plants

Answer 14

Question 15

Which tube is labelled Q in the diagram:
A - renal artery
B - renal vein
C - ureter
D - urethra

Answer 15

C - ureter

Question 16

Describe how to test for glucose in a sample of urine

Answer 16

• Benedict’s added
• Heated

Question 17

Name an abiotic factor that could affect the distribution of the plant species

Answer 17

temperature / water / sunlight / wind speed / mineral
ions

Question 18

Describe the differences between the structure of DNA and the structure of RNA.

Answer 18

• DNA double (strand(ed)) (helix)
• DNA contains deoxyribose
• DNA contains thymine
• DNA longer (molecule)

Question 19

Describe the roles of RNA in protein synthesis.

Answer 19

1. transcription produces mRNA
2. mRNA copies code of DNA strand / DNA code copied / carried
   by mRNA
3. mRNA moves out of nucleus / into cytoplasm
4. binds with ribosome
5. tRNA brings amino acids to ribosome
6. anticodon binds with codons
7. translation produces polypeptide / protein / amino acid chain

Question 20

Describe the role of structure D in reproduction

Answer 20

• site of implantation of embryo
• placenta grows (in uterus)
• provides nutrition / removes waste from embryo/ / allow named substances

Question 21

Explain the importance of the changes in hormone M and hormone N during the menstrual cycle.

Answer 21

1. M is oestrogen / N is progesterone
2. M / oestrogen increases and peaks before
   ovulation
3. M / oestrogen repairs uterine lining (following
   menstruation)
4. (ready) for implantation (of fertilised egg)
5. N / progesterone increases after ovulation
6. N maintains uterine lining / prevents menstruation
7. drop in N / progesterone causes menstruation

Question 22

Other hormones are involved in the menstrual cycle.
Describe the role of one other named hormone in the menstrual cycle.

Answer 22

• FSH causes growth of follicle (in ovary)
• LH causes ovulation

Question 23

Some children are receiving treatments that reduce the activity of their immune system.
Explain why vaccinations are not used on these children.

Answer 23

• cannot produce antibodies /fewer antibodies produced
• no / fewer memory cells produced
• could develop disease / give child disease

Question 24

Answer 24

Question 25

Which type of bacteria converts ammonia into nitrates? A decomposer B denitrifying C nitrifying D nitrogen fixing

Answer 25

C (nitrifying) A is incorrect as decomposers do not release nitrates B is incorrect as denitrifying bacteria do not release nitrates D is incorrect as nitrogen fixing bacteria do not convert ammonium to nitrates

Question 26

Answer 26

prevent evaporation (from surface of water)

Question 27

Explain why the rate of water loss would be different if a working fan is placed in front of the plant shoot.

Answer 27

- more transpiration / more evaporation / higher (water loss) - (wind) blows /moves the water away - increases / maintains / steeper diffusion gradient

Question 28

The lumen of blood vessel X is wider than the lumen of blood vessel Y (see picture) Explain why this difference in the width of the lumen of the two blood vessels is important for kidney function.

Answer 28

- increases the pressure / creates high pressure - (for) ultrafiltration - so that plasma / small molecules leave glomerulus / enter Bowman’s capsule

Question 29

Explain the effect of increasing the temperature on the mean time taken for the indicator to change from orange to red

Answer 29

-faster photosynthesis - (more) carbon dioxide is removed /absorbed - increased collisions / more (kinetic) energy - (levels off as) light intensity limits the rate instead of temp limiting

Question 30

In another experiment, the student places a test tube containing a leaf and hydrogen‑carbonate indicator in a 25°C water bath. The student then places all this apparatus in the dark for one hour. Explain why the indicator solution changes from orange

Answer 30

- respiration is faster than photosynthesis / more respiration than photosynthesis - so carbon dioxide is released / increases (in indicator / tube)

Question 31

Describe the roles of FSH and LH in the menstrual cycle.

Answer 31

* (FSH) matures eggs / follicles * (FSH) stimulates oestrogen (release) * (LH) induces ovulation / egg release * (LH) stimulates progesterone / oestrogen (release) / stimulates corpus luteum (development

Question 32

Micropropagation is often used to make copies of a snapdragon plant. Describe the process of micropropagation

Answer 32

- take small samples / small tissue / few cells - sterilise - (place into) agar (1) - provide minerals / glucose / carbohydrates / amino acids - plant growth substances / auxin / rooting powder

Question 33

Answer 33

- more radiation increases the number of changes in DNA - mutations (have occurred in the DNA) - (mutations) change amino acid sequences / different protein / different enzyme - changes in DNA increases more - (some) DNA changes have no effect - DNA changes may be recessive (so do not affect phenotype)