that two Flashcards
(114 cards)
1
Q
Why is DNA described as a polymer?
A
it is made of many repeating units
2
Q
Sickle-cell anaemia is an inherited disease caused by a mutation in the haemoglobin gene.
Genes are small pieces of DNA. The DNA in a gene consists of a sequence of bases. The figure below shows part of the base sequence in the DNA of a normal haemoglobin gene and the same section in the sickle-cell gene. A, C, G and T represent the different bases.
Normal gene: GGACTCCTC
Sickle-cell gene: GGACACCTC
Describe how the mutation causes a change in the shape of the haemoglobin protein molecule. (5)
A
- three bases code for one amino acid
- the middle code of CTC has changed to CAC
- so there will be a different amino acid in the (protein) chain
- therefore the protein / chain will have a different shape
- because there is a different sequence of amino acids
3
Q
A cat breeder noticed that four kittens from one Siamese cat mother had a new blue colour at the tip of their tails.
What has caused the new colour to appear?
A
mutation
4
Q
In 2006, Blue-moon butterflies almost became extinct.
Wolbachia bacteria killed males before they could hatch from eggs. Only females were resistant to the bacteria.
In 2006, the number of Blue-moon butterflies had decreased to only 1 percent of the population. Two years later, the number of males was equal to the number of females.
The number of Blue-moon butterflies in the population increased quickly after the new form of the gene had appeared.
Suggest why. (4)
A
- the mutated gene allows male to hatch
- the organisms with this allele are more likely to survive
- and reproduce
- to pass on the useful gene to the next generation / offspring
5
Q
Describe how a human gene could be used to genetically modify a pig embryo. (2)
A
- (human) gene is attached / inserted into pig DNA using enzymes
- transfer (DNA) into (pig) embryo using a vector / plasmid / virus
6
Q
The allele in bollworms for being able to eat GM cotton and survive is recessive.
A bollworm may evolve that has a new dominant allele that allows the bollworm to eat GM cotton and survive.
Explain how a new dominant allele emerging would cause a greater problem than the recessive allele that already exists. (4)
A
- more offspring will be able to eat (GM) cotton and survive
- (because) only one copy of the dominant allele is needed
- (and so) dominant allele is passed on
- (therefore) the population will evolve (to eat GM cotton and survive) faster
7
Q
Compare the structure and function of xylem tissue and phloem tissue. (6)
A
Structure
xylem is made of dead cells but phloem is made of cells that are alive
both are tubular
both are made of cells
xylem are hollow but phloem has cytoplasm
xylem contains lignin but phloem doesn’t
phloem have pores in their end walls but xylem don’t
Function
xylem transports water and phloem transports dissolved sugars
xylem is involved in transpiration but phloem is involved in translocation
xylem transports unidirectionally but phloem transports bidirectionally
both transport substances through the plant
8
Q
Explain why the rate of water loss is lower at midnight. (2)
A
stomata are (completely) closed
because there is little / less / no light
9
Q
Give a reason why someone with a high blood cholesterol concentration has a higher chance of having a heart attack.
A
they are more likely to get a blockage
or they’re more likely to have a bigger blockage
10
Q
Amylase is a polymer of smaller molecules. Name the type of smaller molecule.
A
amino acid
11
Q
Name three parts of the human digestive system that produce amylase. (2)
A
- salivary gland
- pancreas
- small intestine
12
Q
Explain the results at 5 degrees celcius and at 80 degrees celcius. (5)
A
(in both) the solution is not yellow-brown because no starch has been broken down
at 5 degrees celsius, the molecules have a low amount of kinetic energy
so there are less (enzyme-substrate) collisions
at 80 degrees celsius, the enzyme has denatured
so the starch can no longer fit the active site of the enzyme
13
Q
A person has a tumour blocking the tube leading from the gallbladder to the small intestine.
Explain why this person would have difficulty digesting fat. (5)
A
no / less bile reaches the small intestine
(so) less / no emulsification of fat
(so there is a) smaller surface area for lipase to break down fat
pH of small intestine is not neutralised / alkaline
allow pH of small intestine is acid / low
(so) lipase is not at its optimum pH to break down fat
pH (of small intestine) is not suitable for lipase to break down fat
14
Q
Describe and explain how the structure of an artery is related to its function. (6)
A
thick(er) (muscle) walls / tissue
to withstand high blood pressure
or to push blood (all) around the body
do not accept ‘pump’
thick(er) elastic walls / tissue
to maintain / withstand high (blood) pressure
or to retain / regain shape
narrow lumen
to maintain high (blood) pressure
15
Q
Explain why the leaf left in a cupboard with no light for two days contained glucose but did not contain starch. (3)
A
- starch (stores / reserves) have been converted to glucose
- (so that the glucose can be) used for respiration
- (because) there is no light to make (more) glucose by photosynthesis
16
Q
How do thorns defend a gorse plant? (1)
A
deter herbivores
prevent animals (from) damaging it
17
Q
Describe what happens during each stage of the cell cycle. (4)
A
- number of subcellular structures increase
- DNA / chromosomes replicate
- one set of each chromosome is pulled to each end of the cell
- cell membrane and cytoplasm divide
18
Q
A scientist noticed that in one area the gorse plants had yellow leaves and had stunted growth.
One reason for yellow leaves and stunted growth is a deficiency of nitrate ions in the soil.
Explain two other possible reasons for the yellow leaves and stunted growth.
Do not refer to nitrate ions in your answer. (5)
A
lack of magnesium (ions) / magnesium deficiency
(so) not enough chlorophyll for photosynthesis
(so) not enough glucose to make proteins for growth
infection by pathogen
(so) leaves become yellow / discoloured
(so) not enough glucose to make proteins for growth
infected by aphids
(which) removes sugars (from phloem)
(so) not enough glucose to make proteins for growth
lack of (available) light
(so) chlorophyll breaks down
(so) not enough glucose to make proteins for growth
19
Q
A gorse plant has nodules on its roots.
The nodules are part of the living root tissue.
Bacteria which convert nitrogen gas into soluble nitrate ions live in the nodule tissue.
Suggest how the nodules benefit the bacteria. (2)
A
(bacteria) obtain glucose (from the plant)
for respiration
20
Q
A gorse plant has nodules on its roots.
The nodules are part of the living root tissue.
Bacteria which convert nitrogen gas into soluble nitrate ions live in the nodule tissue.
Explain how the nodules benefit the gorse plant. (2)
A
(gorse plant) obtains nitrate (ions)
for amino acids / proteins
21
Q
Cirrhosis of the liver leads to liver failure.
Describe the effects of liver failure on the human body. (4)
A
Level 2: Scientifically relevant facts, events or processes are identified and given in detail to form an accurate account.
Level 1: Facts, events or processes are identified and simply stated but their relevance is not clear.
Indicative content
Responses may refer to either total or partial liver failure
- no bile made (in the liver)
fats / lipids are not emulsified
surface area of fats / lipids not increased
pH of small intestine will not be alkaline / neutralised
enzymes (in small intestine) will not work effectively or food won’t be digested
so may lose weight - lactic acid not broken down / oxidised
accumulation of lactic acid in blood / body
lactic acid is toxic or body will be poisoned
oxygen debt higher / prolonged
so muscle pain / fatigue - proteins / amino acids will not be broken down (in liver)
(amino acids) not deaminated
amino acids not made into urea or will not form ammonia
(however) any ammonia formed is toxic
so accumulation of amino acids in blood / body - liver does not break down / remove other toxins (like alcohol)
toxins accumulate in blood / body
body will be poisoned
so pain or jaundice or swollen liver or portal hypertension occurs - glycogen stores will not be formed
cannot control blood glucose (concentration)
so hyperglycemia / hypoglycemia / diabetes / coma may occur
22
Q
Explain how amylase breaks down starch. Answer in terms of the ‘lock and key theory’. (3)
A
starch / substrate binds to the active site (of the enzyme)
the shape of the substrate and the active site are complementary
a chemical reaction occurs to produce smaller molecules
23
Q
Candida albicans lives in the throat of infected patients.
A sample is taken from the throat of a patient with a suspected Candida albicans infection.
The sample is transferred onto a microscope slide.
Describe how monoclonal antibodies and a fluorescent dye could be used to see any Candida albicans pathogens on the slide. (3)
A
bind fluorescent dye to mAbs
put fluorescent mAbs on the slide
mAbs will bind to Candida albicans and show up under the microscope
24
Q
Explain how increased phagocytosis of the Candida albicans pathogen will help patients. (2)
A
more pathogens will be engulfed / killed by phagocytes
therefore less damage to cells / tissues / organs
25
Give three advantages of asexual reproduction. (3)
only one parent is needed
faster / takes less time
(more) energy efficient
successful traits / propagated / maintained / passed on
no transfer of gametes or seed dispersal
colonisation of local area
not wasteful of flowers / pollen / seeds
genetically identical offspring
26
Person K runs a 10km race.
The volume lost from the body through the skin and by breathing increased.
Explain why more water was lost through the skin during the race. (2)
more sweating
to maintain body temperature / to cool down the body / exercise releases heat
27
Person K runs a 10km race.
The volume lost from the body through the skin and by breathing increased.
Explain why more water was lost by breathing during the race. (3)
more energy is needed
(for) more respiration
so breathing rate increases or to remove carbon dioxide
28
Bluebell plants grow in woodlands in the UK and can sexually reproduce by producing seeds.
Explain why sexual reproduction is an advantage for bluebells. (4)
- (there is) genetic variation (in offspring)
- (so they are) better adapted to survive
- (and) colonise new areas by seed dispersal **or** escape adverse event in original area
- many offspring (are produced) **so** higher probability some will survive
29
A large amount of untreated sewage entered a river. Many fish died.
Untreated sewage contains organic matter and bacteria.
Explain why many fish died. (5)
bacteria decay organic matter / sewage
(by) digestion
(and) bacteria respire aerobically / using oxygen
(which) lowers oxygen concentration in water or fish have less oxygen
(so) reduced energy supply from respiration causes fish to die
30
Give three biotic factors that could affect the size of a population.
pathogens / disease / bacteria / fungi
predators / carnivores / consumers
food
31
Give two ways that a person can reduce the chance of developing Type 2 diabetes.
(more) exercise
eat less carbohydrate / sugar / fat
32
Name five harmful substances that could cause water pollution.
herbicide
fungicide
insecticide
oil
nuclear waster
fertiliser
sewage
33
Give two reasons why it is more energy-efficient to rear cows indoors than to treat cows outdoors. (2)
less energy **lost** as heat (for maintaining body temperature / keeping warm)
less energy **lost** in / for movement
34
Explain how you could tell if a condition is recessive.
parents without conditions produce a child with the condition
35
Amino acids are broken down by **enzyme A** to make ammonia and Toxic substance **P**. Ammonia is broken down by other enzymes to make urea. Toxic substance **P** is broken down by **enzyme B** to make harmless products.
A person with MSUD cannot make **enzyme B**.
Explain why the blood of a person with MSUD will have a high concentration of toxic substance P. (3)
- (enzyme B is not made so) P cannot be broken down
- (but / however) toxic substance / P is still made
- (and) toxic substance / P diffuses into the blood
36
Amino acids are broken down by **enzyme A** to make ammonia and Toxic substance **P**. Ammonia is broken down by other enzymes to make urea. Toxic substance **P** is broken down by **enzyme B** to make harmless products.
A person with MSUD cannot make **enzyme B**.
Explain why the **urine** of a person with MSUD will have a high concentration of toxic substance **P**. (2)
toxic substance / P passes through filter in kidney
(and is) not reabsorbed
37
Amino acids are broken down by **enzyme A** to make ammonia and Toxic substance **P**. Ammonia is broken down by other enzymes to make urea. Toxic substance **P** is broken down by **enzyme B** to make harmless products.
A person with MSUD cannot make **enzyme B**.
Explain why a person with MSUD must have a low-protein diet. (3)
- proteins are broken down into amino acids
- so amino acids should be kept in low amounts
- so (that) toxic substance / P does not build up in the body **and** cause damage to cells / tissues / organs
38
Two organisms X and Y both keep a constant body temperature.
X has a greater surface area to volume ratio.
Explain why the metabolic rate of organism X is greater than the metabolic rate of organism Y. (4)
X has a higher surface area and so will lose heat more quickly (per unit volume)
X requires a greater rate of respiration
(to) generate / release more heat (to keep itself warm / maintain body temperature)
respiration is a (large) part of metabolism
39
Describe how the alveoli and the villi are adapted to increase absorption. (4)
Level 2: Scientifically relevant facts, events or processes are identified and given in detail to form an accurate account.
Level 1: Facts, events or processes are identified and simply stated but their relevance is not clear.
Indicative content
both have a large surface area
to maximise diffusion
both have thin walls or walls that are one cell thick
to reduce (the) diffusion distance / time
both are in close proximity to the blood supply
to reduce (the) diffusion distance / time
both have a good blood supply or both have a capillary network
to maintain concentration gradient
villi have microvilli
to (further) increase surface area
cells of villi contain many mitochondria
for active transport
For Level 2 reference to functions of structural details of both alveoli and villi is required.
40
Explain how a vaccine for HIV could work to prevent a person developing HIV infection. (4)
nactive / weakened / dead HIV is injected (into body / bloodstream / muscle)
white blood cells / lymphocytes produce antibodies
(if infected with HIV) correct / specific antibodies are produced quickly
antibodies destroy / kill the HIV
41
Describe how the monoclonal antibody for HIV can be produced. (4)
HIV / antigen injected into mouse
extract / collect (mouse) **lymphocytes** that make the specific antibodies for HIV
combine lymphocytes with a tumour cell to create a **hybridoma** cell
hybridoma cell **clone**d to create many cells that produce the antibody
42
Describe how mitosis produces two genetically identical cells. (4)
DNA / chromosomes / genetic material replicates
chromosomes are pulled / moved apart (to each end of the cell)
cell membrane and cytoplasm divide to form two cells
the set of chromosomes in each new cell are identical
43
Give two ways a person with a mild infection of Salmonella can help prevent the spread of the bacteria to other people. (2)
- isolate yourself
- disinfect clothes / surfaces
- do not share utensils / cutlery / towels
- wash hands after using toilet / being sick
- wash hands before preparing / handling food
- do not prepare food (whilst infected)
44
*Salmonella* bacteria can be transmitted from chickens to humans. Chickens can be vaccinated to prevent the transmission of *Salmonella* bacteria to humans.
Suggest one other way farmers could prevent the transmission of *Salmonella* from chickens to humans.
antibiotics
don’t sell infected chickens / eggs
keep infected chickens indoors / isolated
slaughter the infected chickens
45
How would you change an investigation to make it repeatable? (1)
repeat the investigation **and** see if the results are the same / different
46
Explain why having more red blood cells per unit volume of blood is an advantage to an athlete. (3)
more haemoglobin
more oxygen can be transported / carried
more respiration of muscles or more energy released for muscle
47
Name three substances transported in the blood plasma.
urea
carbon dioxide
lactic acid
water
amino acids
glucose
proteins
antibodies
ions
48
Compare the structure of an artery with the structure of a vein. (4)
arteries have a narrow**er** lumen
arteries have a thick**er** layer of muscle
arteries have a thick**er** layer of elastic tissue
arteries don’t have valves **and** veins do
49
What is the function of the cell membrane?
to control the movement of substances in and out of the cell
50
In a person with cystic fibrosis, cells lining the lungs and the digestive system create too much mucus.
The mucus can:
- block the duct leading from the pancreas to the small intestine
- block the tubes leading to the alveoli in the lungs
Explain why children with cystic fibrosis grow more slowly than children without cystic fibrosis. (6)
Level 3: Relevant points (reasons / causes) are identified, given in detail and logically linked to form a clear account.
Level 2: Relevant points (reasons / causes) are identified, and there are attempts at logical linking. The resulting account is not fully clear.
Level 1: Points are identified and stated simply, but their relevance is not clear and there is no attempt at logical linking.
Indicative content
fewer (digestive) enzymes enter the small intestine
- (so) fewer enzymes break down / digest less food
- (therefore) less absorption of nutrients
- (so) less glucose can enter the blood(stream)
- (so) less (glucose) available for respiration
- (less absorption of nutrients so) fewer amino acids can enter the blood(stream)
- (so) less protein is made (for growth)
*ignore reference to bile*
less oxygen enters the blood(stream) / reaches cells / organs / tissues (ignore body / lungs)
- (so) less (oxygen) available for (aerobic) respiration
- (so) less energy released / available (for growth)
do **not** accept energy produced
for level 3, reference to both enzymes and oxygen is required
51
Lung transplants from donors have risks. One risk is organ rejection.
Scientists are researching how to solve the problem of organ rejection and hope to use stem cells to create healthy lungs.
The healthy lungs can then be transplanted in cystic fibrosis patients without the risk of organ rejection.
Describe how scientists may use stem cells to create healthy lungs that are not rejected by the patient with cystic fibrosis. (4)
- take stem cells from patient(‘s skin / bone marrow)
- remove / change / fix the faulty / CF gene
- create embryo using these stem cells
- remove stem cells (from embryo) and allow them to differentiate into lung (cells)
52
A farmer thinks a potato crop is infected with virus Y.
The farmer obtains a monoclonal antibody test kit for Y.
To make the monoclonal antibodies a scientist first isolates the Y protein from the virus.
Describe how the scientist would use the protein to produce the Y monoclonal antibody. (4)
- inject the protein into a mouse
- combine lymphocytes with tumour cells to make hybridoma cells
- find a hybridoma which makes a monoclonal antibody specific to Y
- clone the hybridoma cell to produce many cells
53
Plants infected with aphids may show symptoms of magnesium deficiency.
Magnesium deficiency symptoms include:
- yellow leaves
- stunted growth.
Explain how a deficiency in magnesium could cause these symptoms. (5)
- yellow leaves due to lack of chlorophyll
- less light absorbed
- lower rate of photosynthesis
- plant makes less glucose
- less glucose is converted into protein (for growth)
53
Describe how a student could test cow’s milk to show whether it contains protein and different types of carbohydrate. (6)
Level 2: Scientifically relevant facts, events or processes are identified and given in detail to form an accurate account.
Level 1: Facts, events or processes are identified and simply stated but their relevance is not clear.
Indicative content
- Biuret reagent tests for protein
- add Biuret reagent to milk
- solution will turn (from blue) to lilac if positive
- iodine solution tests for starch
- add iodine solution to milk
- solution will turn (from orange / brown) to blue / black if positive / present
- Benedict’s reagent tests for sugars
- add Benedict’s reagent to milk and boil / heat (any temperature above 60 °C)
- solution will turn (from blue) to (brick) red / brown / orange / yellow / green if positive
for level 2, reference to all three food tests is required
54
A scientist investigated the effect of bile on the breakdown of fat in a sample of milk.
The scientist used an indicator that is colourless in solutions with a pH lower than 10, and pink solutions with a pH above 10.
This is the method used:
1. Add 1 drop of bile to a test tube and one drop of water to a second test tube.
2. Add the following to each test tube:
- 5cm3 of milk
- 7cm3 of sodium carbonate solution (to make the solution above pH 10)
- 5 drops of the indicator
- 1cm3 of lipase
3. Time how long it takes for the indicator in the solutions to become colourless.
The results are shown below.
Time taken for the indicator **with bile** to become colourless: 65s
Time taken for the indicator **without bile** to become colourless: 143s
Explain the difference in the results for the two test tubes. (3)
bile emulsifies fats
creating a larger surface area
so lipase can break down lipids more quickly to produce fatty acids
55
Explain why a leaf left in a cupboard with no light for two days contained glucose but did not contain starch. (3)
- starch (stores / reserves) have been converted to glucose
- (so that the glucose can be) used for respiration
- (because) there is no light to make (more) glucose by photosynthesis
56
A student carried out an investigation using chicken eggs.
This is the method used.
1. Place 5 eggs in acid for 24 hours to dissolve the egg shell.
2. Measure and record the mass of each egg.
3. Place each egg into a separate beaker containing 200 cm3 of distilled water.
4. After 20 minutes, remove the eggs from the beakers and dry them gently with a paper towel.
5. Measure and record the mass of each egg
Explain how the student could modify the investigation to determine the concentration of the solution inside each egg. (3)
- use five (or more) different salt / sugar solutions
- plot percentage change (in mass / volume) on a graph
- determine the concentration where the line crosses the zero percentage change
57
Which plant does aspirin originate from?
willow
58
Which part of the heart recieves oxygenated blood from the lungs?
left atrium
59
Which part of the heart pumps deoxygenated blood to the lungs?
right ventricle
60
Explain the effect of a partly blocked coronary artery on the human body. (6)
Level 3: Relevant points (reasons / causes) are identified, given in
detail and logically linked to form a clear account.
Level 2: Relevant points (reasons / causes) are identified, and
there are attempts at logical linking. The resulting account is not
fully clear.
Level 1: Points are identified and stated simply, but their relevance
is not clear and there is no attempt at logical linking.
Indicative content:
* reduced blood flow to heart (muscle / tissue / cells)
* (so) less oxygen to heart (muscle / tissue / cells)
* (so) less glucose to heart (muscle / tissue / cells)
* (so) less (aerobic) respiration (in heart / body cells)
* (more) anaerobic respiration
* (so) less energy (released)
* (so) less muscle contraction
* (so) less blood / oxygen / glucose around the body (from heart) **or** slower flow of blood / oxygen / glucose to body (from heart)
* less carbon dioxide removed from body (muscle / tissue / cells)
* (resulting in) breathlessness
* (resulting in) tiredness
* (anaerobic respiration causes) production of lactic acid
* (build-up of lactic acid) causes muscle fatigue / pain **or** chest pain
For Level 3, students must explain the effect of reduced oxygen /
glucose on respiration or energy release and its consequence
61
Explain three different treatments for a blocked coronary artery and how they work. (6)
- (insert) stent(s)
- (to) open (coronary) artery
- (prescribe) statins
- (to) reduce (blood) cholesterol
- heart transplant
- (to) replace the diseased heart with a healthy heart
- (use an) artificial heart
- to keep patient alive whilst waiting for a transplant
- (artery / heart) bypass
- (to) divert blood around the blockage
62
Describe three aseptic techniques students should have used when investigating the effect of different antibiotics.
- **disinfect** hands / work surface
- work near a flame
- work in a fume cupboard
- pass inocculating loop / forceps through a flame (before use)
- secure lid of Petri dish using adhesive tape
- sterilise Petri dish or culture medium (before use)
63
Explain why scientists use 37°C but students must use 25°C to incubate bacteria. (3)
- 37°C is human body temperature
- bacteria grow best / better at 37°C
- 25°C reduces / prevents the growth of bacteria that are harmful to humans
64
Some antibiotics work because they damage the bacterial cell wall.
The bacteria die because the cells burst.
Explain why the cell bursts. (3)
- water enters the cell
- by osmosis
- damaged cell wall cannot withstand pressure of water
65
Explain the effects of anaerobic respiration on a person's body during vigorous exercise. (6)
- muscle fatigue or oxygen debt occurs
- caused by (build-up of) lactic acid
- (continued) heavy / deep / fast breathing
- to provide the oxygen needed to break down (built-up) lactic acid
- (continued) increased heart rate
- to provide the oxygen needed to break down (built-up) lactic acid
- fewer / weaker muscle contractions
- (because) less energy is released / available
66
Anabolic steroids increase muscle mass.
Explain how taking anabolic steroids could improve an athlete's performance. (2)
- faster / stronger
- more / stronger muscle **contract**ions
67
Describe how scientists make mAbs using hybridoma cells. (3)
any **three** from:
- (cell) is cloned
- many (identical) cells are produced
- all the cells make the same antibody
- the antibody is (collected and) purified
68
Suggest the purpose of having a control area in a test strip. (1)
to show that the test is working
69
Explain why the bursting of RBCs causes tiredness. (2)
- less oxygen carried (in blood)
- less energy released from respiration
70
Describe the process of cell division by mitosis. (5)
- cell grows and the number of sub-cellular structures increase
- DNA replicates
- one set of each chromosome is pulled to each end of the cell
- nucleus divides
- cell membrane and cytoplasm divide to form two form two (genetically identical daughter) cells
71
Explain why sodium hydrogencarbonate solution is used instead of water. (2)
- sodium hydrogencarbonate solution provides / releases carbon dioxide
- for photosynthesis
72
Why would you use a **thin layer** of onion epidermis for a microscopic slide?
to allow light to penetrate **or** help see indvidual cells
73
A hornet moth mimcs the striped pattern on a hornet.
Suggest how mimicry helps the hornet moth survive. (1)
predators / animals are deceived / tricked **and** so avoid eating it
74
Adult hornet moths lay eggs that hatch into larvae.
The larvae of the hornet moth:
- live inside the roots of trees
- use the tree roots as a source of food
- cause damage to the tree roots
Explain why a tree might die if the roots of the tree are damaged. (6)
Level 3: Relevant points (reasons / causes) are identified, given in detail and logically linked to form a clear account.
Level 2: Relevant points (reasons / causes) are identified, and there are attempts at logical linking. The resulting account is not fully clear.
Level 1: Points are identified and stated simply, but their relevance is not clear and there is no attempt at logical linking.
Indicative content
less absorption of water
- less water so lower rate of photosynthesis
- so less glucose produced
- for respiration / energy release
- so less cellulose produced so fewer cells walls / cells made
- so fewer amino acids produced to make new proteins
- cells lose turgidity
/
less absorption of (named) ions / minerals
- fewer nitrates so fewer proteins made for growth
- fewer magnesium ions so less chlorophyll produced
- so lower rate of photosynthesis
/
damage to phloem
- less transport of sugars to root cells
- for respiration / energy release
/
damage to xylem
- less water transported (to cells)
- fewer nitrates reach cells
- so fewer proteins made for growth
- fewer magnesium ions reach cells
- so less chlorophyll produced
- less magnesium / chlorophyll so lower rate of photosynthesis
/
* less anchorage
75
Organism M exchanges gases with the environment directly through its skin.
Organism N exchanges gases with the environment using its respiratory system.
M has a surface area to volume ratio of 2568:1
N has a surface area to volume ratio of 29:1
Explain why N requires a respiratory system, but organism M does **not** require a respiratory system. (2)
- N has a smaller surface area to volume ration than M
- so **diffus**ion distance is too large
76
Suggest **three** reasons for a decrease in the number of new HIV cases.
* better education (into prevention of spread of HIV)
* condoms more widely available **or** condoms easier to source **or** condoms cheaper
* new / better drugs (to prevent HIV infection / spread)
* better / more testing / identification (of people with HIV)
*ignore vaccination*
77
Suggest how the mAb for HIV helps to prevent a person infected with HIV from developing AIDS. (3)
- monoclonal antibody is complementary / specific to HIV antigen
- monoclonal antibodies attach to (all the) HIV antigens
- (so) HIV cannot bind to (human) cell
**or** (so) HIV genetic material cannot enter (human) cell
**OR**
- monoclonal antibody is complementary / specific to HIV antigen
- monoclonal antibody with (antiretroviral) drug attached attaches to the HIV antigens
- drug destroys the virus **or** drug destroys genetic material
78
Use of mosquito nets has helped to reduce the number of deaths from malaria each year.
Suggest two other reasons for the reduced number of deaths from malaria each year.
- improved health care
*allow **more / better / new vaccines / antibiotics / treatments***
- use of mosquito control methods
*allow prevent mosquitoes from breeding / draining water holes / spraying insecticides / repellants*
- changing behaviour to avoid being bitten
79
Describe how the human body:
- prevents pathogens from entering
- defends itself against pathogens inside the body
(6)
**Level 2:** Scientifically relevant facts, events or processes are identified and given in detail to form an accurate account.
**Level 1:** Facts, events or processes are identified and simply stated but their relevance is not clear.
**Indicative content**
**prevents pathogens from entering**
**skin**
* tough / dry / dead outer layer
* skin acts as a barrier
* sebum / oil on (surface of) skin
* sebum / oil repels pathogens
* scabs form over cuts or scabs form a barrier
* platelets are involved in forming clots / scab
**stomach**
* contains (hydrochloric) acid
* (HCl) kills bacteria
* in food or in swallowed mucus
**eyes**
* produce tears
* contains enzymes to kill bacteria
* tears are antiseptic
**breathing system**
* trachea / bronchi / nose produce mucus
* mucus is sticky
* (mucus) traps bacteria
* (mucus) carried away by cilia
**defends itself against pathogens inside the body**
* immune system / white blood cells (WBCs)
* WBCs engulf pathogens
* antitoxins are produced
* (antitoxins) neutralise toxins / poisons (produced by pathogen)
* antibodies are produced
* (antibodies) help destroy pathogens
* memory cells (are formed)
* (memory cells give a) more rapid response if pathogen re-enters
a **level 2** response should refer to body defence **and** the immune
system
80
Describe the transport of water through a plaant from the roots to the atmosphere. (3)
- transported in xylem
- water evaporates
- through the stomata
81
Two plants were moved to a new location.
Give three reasons volume of water lost per unit time increased. (3)
- **less** humid
- **high(er)** temperature
- wind**ier**
- light intensity was **higher**
*answers must be comparative*
82
Explain why a person with a leaking hart valve has difficulty exercising. (4)
**Level 2:** Relevant points (reasons/causes) are identified, given in detail and logically linked to form a clear account.
**Level 1:** Relevant points (reasons/causes) are identified, and there are attempts at logical linking. The resulting account is not fully clear.
**Indicative content:**
- backflow can occur **or** some blood flows backwards
- less blood leaves the heart **or** less blood is pumped around the body **or** some blood stays in the heart (instead of being
pumped out) **or** reduced blood pressure **or** reduced flow rate
- less oxygen supplied to muscles / cells
- (so) less **aerobic** respiration
- (so) less energy released
- (so) less (efficient) muscle contraction
- anaerobic respiration takes place
- less (efficient) removal of lactic acid **or** lactic acid builds up **or** oxygen debt occurs
- (lactic acid building up) causes muscle fatigue
- less (efficient) removal of carbon dioxide (from blood)
a **level 2** response should refer to both respiration **and** the effects
on exercise
83
Glucose is absorbed into the blood in the small intestine by both diffusion and active transport.
Describe how the small intestine is adapted for efficient absorption. (3)
- projections / folds / villi provide a large surface acrea
- walls of projections / folds / villi / capillaries are thin / one cell thick for shorter absorption / diffusion distance
- (small intestine is) very long, increasing time (for absorption)
- good / efficient blood supply to maintain concentration gradient
- cells have many mitochondria for (aerobic) respiration for active transport **or** cells have many mitochondria for energy release for active transport
84
Define the term double circulatory system.
right side of the heart pumps blood to the lungs **and** left side of the heart pumps blood to the body
85
Explain why having only one ventricle makes the circulatory system less efficient that having two ventricles. (2)
- oxygenated and deoxygenated blood mixes
- (so) less oxygen reaches the body / cells / tissues
86
Explain why an axolotl may die in water with a low concentration of water. (4)
- concentration gradient (of oxygen) is shallow(er) / less steep
- (therefore) less oxygen diffuses into blood / cells / gills **or** oxygen diffuses out of the axolotl's blood / cells / gills
- (so) less (aerobic) respiration occurs so less energy is released / available **or** (so more) anaerobic respiration occurs so less energy is released / available
- (so) less metabolism **or** (so when) anaerboci respiration occurs, lactic acid is produced (and is toxic)
87
Suggest two reasons why an axolotl is a suitable animal for research in the laboratory.
- don't take up much space
- easy / cheap to keep / rear
- easy to breed **or** reproduce quickly
88
If a gill of a axolotl is removed, a new gill will grow in its place.
An axolotl may **not** be suitable to study when researching regeneration in human tissue.
Suggest why.
- not a mammal / it's an amphibian
- regeneration in gills may be different to that in other organs
- metabolism / body processes are too different to humans
- it's an endagenered species
89
What is an enzyme? (2)
- protein
- biological catalyst
90
Where is carbohydrase / amylase produced? (3)
- small intestine
- pancreas
- salivary gland
91
Explain how pancreatic cancer may cause a person to lose weight.
Do **not** refer to hormones in your answer. (4)
- reduced / no (digestive) enzyme production / release
- food is not broken down fully **or** food is not digested fully
plus any **one** of the following routs for max **2** marks:
- less glucose / sugar absorbed **or** less glucose / sugar passes into the blood(stream)
- (so) less glucose available for respiration so more fat used up in metabolism / respiration
**OR**
- fewer amino acids avsorved **or** fewer amino acids pass into the blood(stream)
- (so) fewer amino acids are available for making new protein for repair / replacement
**OR**
- fewer fatty acids absorbed **or** fewer fatty acids pass into the blood(stream)
- (so) fewer fatty acids available so less fat is stored in the body
**OR**
- chemotherapy / radiotherapy causes nausea / loss of appetite
- (so) less intake of food
91
Where is lipase produced?
pancreas
92
Where is protease produced? (3)
- stomach
- pancreas
- small intestine
93
Where does protease act? (2)
stomach and small intestine
94
Enzyme A and enzyme B are involved in controlling cell division in pancreatic cancer cells.
Most cancer cells produce both enzyme A and enzyme B.
Some people have a gene mutation that stops cancer cells producing enzyme B.
In pancreatic cancer cells, enzyme A **or** B cause cells to divide uncontrollably and where neither are present, cells stop dividing and are destroyed.
Scientists have developed a drug that inhibits enzyme A.
The drug is given to pancreatic cancer patients who have the gene mutation that stops cancer cells producing enzyme B.
The drug only targets cancer cells.
Explain why the drug can be used to treat pancreatic cancer in patients with the gene mutation. (3)
- (cancer) cells cannot divide **or** (cancer) cells are destroyed / killed
- (so) tumour doesn't grow / get bigger **or** tumour less less likely to spread **or** tumour less likely to form secondary tumours
- (because) enzymes A and B are not working / active / effective / present **or** (because) A and B are inhibited
95
Enzyme A and enzyme B are involved in controlling cell division in pancreatic cancer cells.
Most cancer cells produce both enzyme A and enzyme B.
Some people have a gene mutation that stops cancer cells producing enzyme B.
In pancreatic cancer cells, enzyme A **or** B cause cells to divide uncontrollably and where neither are present, cells stop dividing and are destroyed.
Scientists have developed a drug that inhibits enzyme A.
The drug is given to pancreatic cancer patients who have the gene mutation that stops cancer cells producing enzyme B.
The drug only targets cancer cells.
Explain why the drug could **not** be used to treat pancreatic cancer in a patient that produces both enzyme A and enzyme B. (2)
- (functional) enzyme B would still be made / present
- (therefore cancer) cells would still divide uncontrollably **or** (therefore cancer) cells would not be destroyed **or** (therefore) the tumour will (continue to) grow / get bigger / spread **or** the tumour will form secondary tumours
96
Explain how a monoclonal antibody works to treat pancreatic cancer. (3)
| THIS ONES REALLY HARDDDD!!!
- monoclonal antibody is attached to radioactive substance / toxin / drug / chemical
- mAb will (only) attach to / target (antigen on) cancer cells / tumour
- (so) radioactive substance / toxin / drug / chemical will (bind to cancer cells and) stop them growing / dividing
97
ENZYME ACTION / LOCK AND KEY MODEL
1. the **substrate** binds to the active site of an enzyme because their shapes are **complementary**
2. bonds are broken
3. **products** are released and the enzyme is unchanged
98
MOVEMENT OF WATER IN PLANTS
1. water **evaporates** from the leaf cells (transpiration)
2. the water vapour diffuses out of the leaft through the **stomata**
3. this causes water to be pulled up the **xylem**
4. water enters root hair cells from the soil via **osmosis**
99
CELL CYCLE
1. during stage 1 the DNA is **replicated** and more sub-cellular structures are made
2. during stage 2, one set of **chromosomes** is **pulled to each end of the cell**
3. during stage 3, the **cytoplasm** and cell membrane **divide**
4. **two genetically identical cells are formed**
100
BREAKDOWN OF LIPIDS
1. bile is produced in the **liver** and stored in the **gallbladder**
2. when bile is released into the small intestine it **emulsifies** fats/lipids
3. this increases the **surface area** of fats so they can be digested by **lipase** into glycerol and fatty acids more quickly
101
PRODUCING MONOCLONAL ANTIBODIES
1. a mouse is injected with antigens
2. the mouse lymphocytes will produce **antibodies** specific to the antigens
3. the mouse lymphocytes are extracted
4. they are combined with **tumour** cells to create hybridoma cells
5. hybridoma cells are cloned **to produce many identical cells**
6. the cells will all produce the same antibodies which can be collected and purified
102
METASTASIS / SPREADING OF MALIGNANT TUMOURS
1. **cells** break off from a **malignant** tumour
2. cells enter the bloodstream
3. they travel to a different part of the body
4. a **secondary** tumour is formed in a different part of the body
103
OXYGEN DEBT
- lactic acid is produced during **anaerobic** respiration
- this can build up in muscles causing **fatigue** and muscles **contract** less efficicently
- lactic acid is removed from muscles by the blood
- in the **liver** lactic acid is broken down using **oxygen**
- this is why we **breath quickly / heavily** after exercise
104
DRUG TRIALS
1. preclinical trials are carried out in a lab on **cells, tissues and live animals**
2. clinical trials are first carried out on **healthy volunteers** using very low **doses**
3. if the drug is safe, it is tested on **patients** to find the optimum **dosage** and test how **effective** it is
4. in double blind trials, some patients are given a **placebo**
5. the results are published and **peer reviewed** to check for false claims
105
EFFECT OF MAGNESIUM DEFICIENCY
- if a plant is deficient in **magensium** ions, then the plant will produce lless chlorophyll
- this leads to yellow patches on the leaves (**chlorosis**)
- the plant will carry out less photosynthesis, and therefore create less **glucose**
106
Explain how a stent works to treat coronary heart disease. (2)
- opens / widens (blood) vessel
- to allow more blood to flow **or** to allow more glucose / oxygen to the heart
107
Explain how a reduced amount of oxygen entering the bloodwill affecet the human body. (3)
- less respiration
- less energy released
- increased heart / breathing rate **or** reduced metabolism / muscle contraction
108
The concentration of dissolved sugars in the phloem cell is higher than in cell **K**.
Explain how sub-cellular structures help to move dissolved sugars from cell **K** into the phloem cell. (5)
- mitochondria
- for respiration
- to release energy
- **energy** needed to move **sugars** against concentration gradient
- by active trasnport
109
Suggest two reasons why doctors are concerned about antibiotic resistance. (2)
- new antibiotics need to be developed which takes time / money
- curernt / available antibiotics do not kill (certain) bacteria
- diseases become more common **or** there will be some diseases that cannot be cured / treated
110
Suggest why viruses cannot be grown on agar. (1)
viruses **only** exist / reproduce inside (living) cells
111
Why is it difficult for scientists to develop drugs to destroy viruses?
drugs damage cells / tissues **or** it is hard to get drugs into cells
112
Give the reason why a drug that stops cell division helps to treat cancer.
tumours cannot grow
