4 and 6 markers

Question 1

(4) Discuss the advantages and disadvantages of the use of biofuel.

Answer 1

removes CO2 when growing (1)
less use of {fossil fuels/named
fuel} (1)
reduced SO2 emissions (1)
renewable / can be regrown
quickly /sustainable (1)

reduced food production (1)
takes up land (1)
reduced biodiversity (1)
crop growth is weather
dependent (1)

Question 2

(6) Explain how optimum conditions for the growth of microorganisms are controlled in a fermenter.

Answer 2

• water (cooling) jacket
• temperature probe
• to maintain an optimum temperature
• inlet pipes for nutrients eg ammonia
• to supply microorganism with food source eg materials to make proteins
• oxygen pumped in
• for aerobic microorganisms or aerobic respiration
• carbon dioxide removed
• pH probe
• alkali added to raise pH
• maintain optimum pH
• paddles
• to evenly distribute nutrients, oxygen and break up clumps of microorganisms
• aseptic conditions
• to prevent contamination of the fermenter
• reduce competition

Question 3

(6) Using the information in the graph, explain how temperature affects the
fermentation process during yogurt production.

Answer 3

Data trends
 pH of milk is 6.8
 pH reduces to pH 4.5 in 6 hours at 40°C
 pH reduces to pH 4.5 in 9 hours at 20°C
 pH not significantly reduces at 60°C
Interpretation
 fermentation faster at the optimum temperature
 optimum temperature for bacteria growth at 40°C
 enzymes more active at optimum temperature
 no fermentation/bacteria killed/enzymes denature at high
temperatures
Yogurt production
 lactose in the milk
 converted into lactic acid
 by bacteria/named bacteria
 reduces pH
 thickens/clots/coagulates the milk

Question 4

(6) Describe how Agrobacterium tumefaciens can be used to create transgenic plants.

Answer 4

genetic modification
• transferring a gene from one organism to another
• restriction enzymes to cut the gene out
• plasmids used to carry gene
• sticky ends to join complementary bases
• ligase to join the DNA

use of Agrobacterium
• Agrobacterium is a vector (for the gene)
• the Agrobacterium has a suitable gene added to it • example of a suitable gene eg drought resistance
/ insect resistance / larger yield / for flavonoids
• Agrobacterium naturally invades plant cells
• its DNA is incorporated into the plant’s DNA

production of plants
• plant sprayed with Agrobacterium
• crown gall (formed)
• crown gall is cut into small pieces

• leaf discs are incubated with Agrobacterium

• (crown gall tissue / leaf discs) grown in tissue culture
• explants
• grown into crops

Question 5

(4) Explain one advantage and one disadvantage of introducing this gene into crop plants.

Answer 5

crop produces a toxin that kills insects (that eat plant)(1)
•so less damage by insect / increased crop yield (1)
cross pollination / fertilisation with other plants (species) (1)
•producing weeds that contain the toxin(1)

Question 6

(6) Describe how enzyme technology can be used to produce these food products.

Answer 6

Sweets
• made using invertase/sucrase
• converts sucrose into glucose and fructose
• reduces viscosity of sugar mixture
• increases simple sugar content, increasing sweetness
• production of soft centred sweets
• production of lower calorie sweets

Vegetarian Cheese
• made using chymosin
• produced by genetically modified organisms
• Chymosin initiates clotting/protein coagulation
• reduces the use of rennet extracted from animals

Lactose free milk
• made using lactase
• using immobilised enzymes
• lactose converted to galactose and glucose
• beneficial to people with lactose intolerance

Question 7

(6) Explain how the menstrual cycle is controlled by hormones and negative feedback.

Answer 7

Stages and hormones
• menstrual cycle consists of menstruation, uterus lining thickening and ovulation
• hormones involved in the menstrual cycle are oestrogen, progesterone, FSH and LH
Role of the hormones
• FSH stimulates the follicles to mature
• follicles secrete oestrogen
• oestrogen is responsible for the repair of the uterus wall
• high levels of oestrogen stimulate the release of LH
• LH triggers ovulation
• corpus luteum produces progesterone
• progesterone maintains the lining of the uterus
Control mechanisms
• oestrogen inhibits the production of FSH
• progesterone inhibits the production of LH
• progesterone inhibits the production of FSH
• menstruation is triggered by low levels of oestrogen and progesterone
• Low progesterone levels cause FSH to be released

Question 8

(4) Use the diagram to help explain the body’s hormonal response to dehydration.

Answer 8

• (dehydration detected by) osmoreceptors/hypothala mus (1)
• pituitary gland (1)
• (releases more) ADH (1)
• ADH acts on the nephron/collecting duct/tubules (1)
• making the {collecting duct/tubules/nephron} more permeable (1)
• so more water is reabsorbed (by the body/blood) (1)