B4

Photosynthesis produces oxygen.

(a) Complete the word equation for photosynthesis.

Carbon dioxide+water→glucose+oxygen

Explain how oxygen is used in cells.

(used in aerobic) respiration

do not accept anaerobic

1

to release / transfer energy

A student investigated the effect of light from different coloured light bulbs on

photosynthesis.

The student:

• used pondweed in a beaker of water

• used different coloured light bulbs in a lamp

• counted the number of bubbles of oxygen the pondweed produced in 2

minutes for each colour of light bulb.

(c) Give one hazard the student would need to consider when using the

apparatus in this investigation.

Give the risk the hazard would cause.

Hazard

any one pair from:

• bulb / lamp is hot

(so) may burn you / skin

1

1

• glassware is breakable (1)

(so) may cut skin (1)

• electricity in close proximity to water (1)

allow named example of electrical item

in close proximity to water

(so) may get electric shock (1)

• scissors / scalpel (to cut pondweed) are sharp (1)

may cut skin (1)

mark in pairs

The student needed to keep the temperature of the water in the beaker the

same throughout the investigation.

Describe how the student could keep the temperature of the water the

same.

(use a) water bath

(e) The beaker of water contained the pondweed.

Explain why the temperature of the water in the beaker needed to be kept

the same throughout the investigation.

(change in) temperature affects / changes (the rate of)

photosynthesis

allow temperature is a limiting factor (of

photosynthesis)

allow temperature affects enzyme

(activity)

allow temperature affects rate of

reaction

1

(so) will affect / change the number of bubbles (produced

Blue

What is the best way to display the data in the table above?

Bar graph

h) The student wanted to measure the volume of oxygen the pondweed

produced in 2 minutes.

Name one piece of apparatus the student could use to measure the

volume of oxygen.

any one from:

• measuring cylinder

• (gas) syringe

• burette

(i) as light (intensity) increases, rate / photosynthesis increases

allow positive correlation

1

(rate / photosynthesis increases) at the same rate as light (intensity)

Give two control variables the scientist should have used in the

investigation

any two from:

• temperature

• size of tomato plants or size / number of leaves

allow age of plant

• light

• (volume of) water

allow (amount of) water

• (amount / type of) fertiliser / minerals / ions / nutrients (given to

plants)

allow (type of) compost / soil

allow named example of mineral ion such as nitrate

/ magnesium

• time before rate readings are taken

How could the scientist have improved the validity of the results?

repeat each reading three times and calculate a mean

Explain the change in the rate of photosynthesis when the concentration of

carbon dioxide increased between 0.00% to 0.08%.

(the rate of photosynthesis) increases

ignore values

1

(because) carbon dioxide is needed for photosynthesis

allow 2 marks for (there is) more carbon dioxide for

(more) photosynthesis

A farmer decided not to use a concentration of carbon dioxide higher than

0.08% to grow tomato plants.

Suggest two reasons for the farmer’s decision.

Use information from above table and your own knowledge.

any two from:

• it would not increase the rate (of photosynthesis)

allow it would not change the rate (of

photosynthesis)

allow photosynthesis would not increase

• it would not increase the growth of tomatoes

• it would cost more

allow idea of profit will not increase

allow reference to avoiding global warming

Leaf 1 or covered with black paper

no light so no photosynthesis (occurs)

ignore reference to water

ignore reference to carbon dioxide

1

Leaf 2 or covered with transparent plastic

no carbon dioxide so no photosynthesis

1

Leaf 3 or not covered

light and carbon dioxide present so leaf can photosynthesise

ignore no limiting factors

1

for either Leaf 1 / 2

(so) glucose not made

1

(and therefore) glucose / sugar cannot be converted to starch

B)green) starch / present / positive

allow blue-black / black or dark blue

and

(white) no starch or not present or negative

C)green part contains chlorophyll and white part does not

ignore chloroplasts

1

(so) light is absorbed by green part (but not by white part) so

photosynthesis occurs and starch can be formed

In some leaves, the green parts become yellow because of an ion deficiency.

(d) Which ion is deficient in a plant with yellow leaves?

magnesium

Give the scientific term that describes the yellow colour of the leaves.

Chlorosis

The rate of photosynthesis is affected by different factors.

How could the oxygen produced during photosynthesis be used to

measure the rate of photosynthesis?

(measure the) volume (of oxygen) released / produced in a given time

or

(count / number of) bubbles released / produced in a given time

What is meant by a ‘limiting factor’?

a factor that) if increased would increase the rate (of a reaction)

or

(a factor that) prevents the rate (of a reaction) increasing

Explain the effect of increasing temperature and increasing carbon dioxide

concentration on the rate of photosynthesis shown in Figure 2.

increasing temperature while keeping the carbon dioxide

(concentration) constant increases the rate (of photosynthesis)

allow increasing the carbon dioxide (concentration)

while keeping temperature constant increases the

rate (of photosynthesis)

1

increasing the temperature increases the movement of the

molecules / particles / substrate

or

increasing the temperature increases the rate of enzyme activity

increasing carbon dioxide concentration increases (the

concentration of) substrate / reactants

1

all rates plateau at a certain point due to another factor being limiting

from 0 to 5 000 lux

Give one way the student could change the colour of the light shining on

the leaf discs.

any one from:

• use (different) coloured bulb(s) / LED(s)

• use (different) coloured filter(s) in front of lamp

• put (different) coloured transparent material(s) over lamp /

beaker

allow named transparent material(s)

Give the independent variable and the dependent variable in this

investigation

independent

colour of light

allow wavelength of light

ignore colour of filter / bulb / lamp

1

dependent

time (taken for 10 leaf discs to reach the surface of the solution)

All of the air had to be removed from the leaf discs before placing them in

the beaker.

Suggest one reason why.

any one from:

• so that discs would sink (to the bottom of the beaker)

allow leaf for disc throughout

allow so the discs do not float

• so any gas (that makes the discs rise) is from photosynthesis

• air is a gas so any left in discs would add to the oxygen

produced by photosynthesis

ignore reference to carbon dioxide

allow as a control variable

The leaf discs were placed in a beaker of sodium hydrogencarbonate

(NaHCO3) solution.

Explain why sodium hydrogencarbonate solution was used instead of

water.

(sodium hydrogencarbonate) provides / releases carbon dioxide

ignore (sodium hydrogencarbonate)

contains carbon dioxide

ignore provides water

1

(carbon dioxide is used) for photosynthesis

Explain why the leaf discs moved to the surface of the solution during the

investigation

oxygen was produced in photosynthesis

1

oxygen / gas is trapped in / around disc / leaf

Suggest the advantage to a plant of having two types of chlorophyll.

to absorb / use many / more colours / wavelengths of light

allow to increase the rate of

photosynthesis

The leaf discs in the investigation are green.

Explain the results in Table 1 for blue light and for green light.

Use data from Figure 3 and Table 2.

chlorophyll absorbs most or a lot of blue light

chlorophyll absorbs least or very little or not much green light

if neither mark awarded allow 1 mark for

chlorophyll absorbs more blue light

(than green light)

allow chlorophyll reflects most of the

green light

1

1

(so) discs in blue light took the least time to rise (to surface) because

they photosynthesised faster / more

or

(so) discs in green light took the most time to rise (to surface)

because they photosynthesised slower / less

1

use of data (from Figure 3 and Table 2) eg approximately 80% of

blue light absorbed

CF reduces the amount of oxygen that can enter the blood from the alveoli.

Explain how a reduced amount of oxygen entering the blood will affect the

human body.

less (aerobic) respiration

allow (more) anaerobic respiration

1

(so) less energy (released)

created

do not accept less energy produced / made /

1

(results in) less muscle contraction

or

or

(results in) reduced metabolism

allow relevant named metabolic processes

(results in) increased breathing rate / depth

or

(results in) increased heart rate

allow (results in) person getting out of breath

OR

(more) anaerobic respiration (1)

(so) lactic acid produced (1)

(results in) muscle fatigue

or

or

or

(results in) less muscle contraction

(results in) increased breathing rate / depth

(results in) increased heart rate (1)

allow muscle ache / cramp / tiredness / pain

allow (results in) person getting out of breath

Gas exchange happens in the alveoli in the lungs.

Describe three features of the alveoli that help maximise gas exchange.

large surface / area

allow large surface / area to volume (ratio)

1

(large) capillary network

or

good / efficient blood supply

allow many capillaries

1

walls are thin

or

walls are one cell thick

This question is about exercise.

(a) During vigorous exercise, anaerobic respiration occurs in a person’s body.

Explain two effects of anaerobic respiration on the person’s body.

effect) muscle fatigue or oxygen debt occurs (1)

allow muscle cramp ignore fatigue /

cramp unqualified

(reason) caused by (build-up of) lactic acid (1)

• (effect) (continued) heavy / deep / fast breathing (1)

(reason) to provide the oxygen needed to break down (built-up)

lactic acid (1)

allow to repay the oxygen debt

• (effect) (continued) increased heart rate (1)

(reason) to provide the oxygen needed to break down (built-up)

lactic acid (1)

allow to repay the oxygen debt

• (effect) fewer / weaker muscle contractions (1)

(reason) (because) less energy is released / available (1)

do not accept energy being produced /

made / created

Design an investigation to show the effect of different types of exercise on

the heart rate of athletes.

• test a group of athletes

• use at least two different types / intensities of exercise

• get each athlete to do all exercises or have a large (≥30) group

doing each exercise

• record heart rate for each athlete before and after exercise or

calculate increase in heart rate for each athlete after exercise

• calculate the mean increase in heart rates for each type / intensity

of exercise

• compare mean increase in heart rates for each type / intensity of

exercise

• control variables:

o same (biological) sex or mix of sexes

o same level of activity / exercise

o same age

o same caffeine / drug / medicine intake

o same length of time for exercise

o no health issues / illnesses

o return to resting heart rate before each exercise

Anabolic steroids are drugs.

Anabolic steroids:

• increase muscle mass in humans

• are banned in most competitive sports.

Some athletes take anabolic steroids to improve their performance in sport.

(c) Explain how taking anabolic steroids could improve an athlete’s

performance.

athlete is) faster / stronger

allow description of improved

performance

allow reference to increased stamina /

endurance

1

(because more muscle mass so) more / stronger muscle contractions

Scientists use monoclonal antibodies to test for the presence of anabolic steroids

in an athlete’s urine.

To produce monoclonal antibodies, a mouse lymphocyte is combined with a

tumour cell.

(d) What type of cell is created when a mouse lymphocyte and a tumour cell

combine?

hybridoma

Describe how scientists make monoclonal antibodies using the cell created

when a mouse lymphocyte and a tumour cell combine.

any three from:

• (cell) is cloned

ignore name of cell

• many (identical) cells are produced

allow many clones are produced

• all the cells make the same antibody

• the antibody is (collected and) purified

What property makes a monoclonal antibody useful in detecting the

presence of an anabolic steroid in urine?

a monoclonal antibody only binds to the anabolic steroid

The end of the test strip is dipped in urine.

The urine moves up through the test strip.

The test area and the control area contain a dye.

The dye turns blue when monoclonal antibodies bind to it.

(g) Suggest the purpose of the control area in the test strip.

to show that the test is working

Describe the evidence in Figure 2 that shows the test for athlete B has not

worked.

Suggest one reason why the test did not work

evidence

no blue / visible dye (in control area)

allow no line(s) (in control area) allow

no colour change (in control area)

1

reason

(because) no (free) monoclonal antibodies bound to control area

allow the (free) monoclonal antibodies

did not move up the test strip

allow urine did not move up the test

strip

1

or

(because) there were no (free) monoclonal antibodies on the end of

the (test) strip

Name the sub-cellular structures where aerobic respiration takes place

mitochondria / mitochondrion

Energy is released in respiration.

Give two uses of the energy released in respiration.

any two from:

• movement / muscle contraction

• keeping warm

• active transport

• building larger molecules

ignore reference to metabolism

unqualified

allow examples of movement

allow examples of building larger

molecules e.g. making (named) proteins

/ cellulose

allow cell division

ignore growth

Describe two differences between aerobic and anaerobic respiration in

humans.

Do not refer to oxygen in your answer.

any two from:

• anaerobic produces lactic acid and aerobic does not

allow anaerobic creates an oxygen debt

and aerobic does not

• aerobic produces carbon dioxide and anaerobic does not

• aerobic produces water and anaerobic does not

• aerobic occurs (mainly) in the mitochondria and anaerobic

does not

allow anaerobic only occurs in the

cytoplasm

• anaerobic releases less energy than aerobic

allow anaerobic releases less ATP

(than anaerobic)

do not accept anaerobic produces /

makes / creates less energy

What are the two products of anaerobic respiration in plant cells?

Co2

Ethanol

pondweed takes in CO2 for photosynthesis

snail and pondweed are respiring producing CO2

Suggest why the concentration of carbon dioxide increased between day 5

and day 10.

no light so) no photosynthesis

or

plant is not taking in CO2

and

snail and plant are respiring and so are releasing CO2

On day 10, the pond snail died.

Explain why the death of the pond snail caused the concentration of carbon dioxide to increase after day 10.

snail is being decayed / decomposed / broken down

ignore being fed on

1

(by) decomposers / bacteria (in pond water / snail)

allow fungi / microbes / microorganisms

1

(therefore) respiration (of decomposers / bacteria) releases CO2

Describe how energy for the photosynthesis reaction is gained by plants

light

ignore description of subsequent parts of the

photosynthesis reaction

allow sunlight

ignore sun

1

(light) is captured / trapped / absorbed by chlorophyll / chloroplasts

Suggest one possible cause of the anomalous result. (Measuring rate of photosynthesis)

any one from:

• scale / value was misread

ignore human error

ignore references to counting bubbles or time

allow measurement error

• there was air / oxygen in the syringe / measuring cylinder / apparatus

• the lamp / light was moved

temperature changed

• had different mass / length of pondweed

• pondweed had not acclimatised

Give one factor the students should have kept constant in this

investigation. (Photosynthesis)

any one from:

• light (intensity)

do not accept temperature

ignore time

allow distance / power / colour of lamp / light

• carbon dioxide (concentration)

• pondweed size / amount

• pondweed species

allow same (piece of) pondweed

enzyme(s) lose the shape of the active site

allow enzyme(s) (start to) denature

allow enzyme(s) destroyed / damaged

do not accept enzyme(s) killed

glucose from photosynthesis

do not accept starch made in

photosynthesis

(excess) glucose converted to starch

g) Explain why the leaf left in a cupboard with no light for two days did contain

glucose but did not contain starch.

Suggest one way the students could develop the investigation to find out

more about glucose and starch production in plants.

any one from:

• test roots / stems of plants (in the light and dark)

do not accept reference to changing the

independent variable

allow test other parts of the plants

• test other species of plant

allow test other types of plant

• measure the concentrations of glucose and starch

ignore mass / amount

• vary the time in the dark / light

• test variegated leaves

allow any other valid extension ignore

repeats

B) power output of bulb

C) any two from:

• repeat and calculate a mean

or

repeat and to eliminate anomalies

ignore do a control experiment

unqualified

• control the (water) temperature

allow a method of controlling (water)

temperature

• control the concentration of carbon dioxide

allow a method of controlling carbon

dioxide concentration

• control the distance of the bulb from the pondweed

• control the mass / length / species / age of the pondweed

allow use the same piece of pondweed

• give pondweed time to equilibrate

allow do experiment with the bulb off / in

the dark

A)rate of photosynthesis increases

or

number of bubbles produced (in one minute) increases

or

volume of gas / oxygen produced (in one minute) increases

allow decreases / stays the same throughout

B)light intensity

C)reduces the effect of heat from the lamp

or

prevents temperature affecting photosynthesis

D)52

E)should be 62- is to 3sf/ not rounded

the numbers of bubbles at each distance are similar

blue light gives highest (rate of) photosynthesis

allow ecf from candidate’s graph allow blue light is

best

1

green light gives the lowest (rate of) photosynthesis

energy

in this order only

1

cell wall(s)

allow cell

do not accept (cell) membrane

starch / fat / oil / lipid

apparatus set up:

– weed in water in beaker

– light shining on beaker

• method of varying the light intensity–eg changing distance of lamp from

plant

• method of controlling other variables

– use same pond weed or same length of pond weed

– temperature: water bath or heat screen

– CO2

• leave sufficient time at each new light intensity before measurements taken

• method of measuring photosynthesis – eg counting bubbles of gas

released or collecting gas and measuring volume in a syringe

• measuring rate of photosynthesis by counting bubbles for set period of

time

• repetitions

A) trachea

(b) any two from:

• only one air space (per balloon)

or

alveoli not represented

• blood vessels / capillaries not represented

• bronchioles not represented

do not accept bronchi not represented

• glass tube not flexible (like trachea / bronchi)

• bell jar does not move during breathing (like ribs)

• ribs have gaps between them

• rib cage contains muscles

• pleural cavity not represented

A scientist investigated the effect of exercise on breathing rate.

This is the method used.

1. Record the breathing rates of 10 male non-smokers at rest.

2. Tell each man to run on a treadmill at the same speed for 8 minutes.

3. Record the breathing rate of each man every 2 minutes.

4. Continue to record the breathing rate of each man for 4 minutes after he

stops running.

(c) Give two variables the scientist controlled in the investigation.

(c) any two from:

• speed (of treadmill)

• type of exercise or all were running

• (biological) sex or all male

• all were non-smokers

• time spent running

allow ran for 8 minutes

ignore reference to time interval for

counting breaths

Explain why the man’s breathing rate increased when he was running

to get more oxygen (into the blood)

for use in respiration or for releasing energy (for muscle contraction)

or

to remove more carbon dioxide (1)

produced in respiration (1)

Give one measurement that could be taken to show a different effect of

exercise on the body.

Do not refer to breathing rate in your answer.

any one from:

• heart / pulse rate

allow heart beat per minute

• depth / volume of breathing

allow amount of sweat

• volume of sweat

• body temperature

allow body mass / measurement

The men in the investigation were all non-smokers.

Give one effect that smoking can have on the body.

any one from:

• (lung) cancer

• increased blood pressure

• lung disease

allow named example of lung disease

e.g. asthma

• low birth weight in babies of mothers who smoke

• increased risk of heart / cardiovascular disease

allow persistent cough ignore cough

unqualified

A 45-year-old man exercised on a rowing machine for six minutes.

A fitness monitor recorded his heart rate and breathing rate every minute.

The graph below shows the results.

increased (at first)

until 4 minutes or 50 breaths per minute

(then) stayed constant (from 4 minutes or at 50 breaths per minute)

Explain the ways the man’s body has responded to the exercise.

Use information from the graph above.

heart rate increased

○ to increase blood flowing to muscles / lungs

○ to provide more oxygen (to muscles)

○ to provide more glucose (to muscles)

○ to remove carbon dioxide more quickly (from the

muscles / blood)

○ to remove lactic acid more quickly (from the muscles)

• breathing rate increased

○ supplies more oxygen / air to lungs

○ so more oxygen to blood

○ more carbon dioxide removed

• more oxygen to muscles

○ needed for (increased) respiration

○ to release / provide energy

○ for muscle contraction

• anaerobic respiration occurs

○ due to lack of oxygen

○ which causes a build-up of lactic acid

○ oxygen debt

○ muscle fatigue / pain

What conclusion can you make about the relationship between the mass of

sugar used and the volume of gas produced?

the greater the mass of sugar, the greater the volume of foam / gas

produced

Why was no foam produced in the mixture with 0 g of sugar?

no respiration occurs

or

sugar / glucose is needed for respiration

Why was the measuring cylinder with 0 g of sugar included in the

investigation?

for comparison / to compare

allow as a control (experiment)

allow as a base line

do not accept as a control variable

or

to check that no other factor / variable is influencing the results

or

to ensure validity

The top of the mixture can be covered with a layer of oil after step 3 in the

method.

Suggest why the layer of oil stops the yeast respiring aerobically.

it) stops the oxygen / air getting in / through

Metabolism is the sum of all the chemical reactions in the cells of the body.

One metabolic reaction is the formation of lipids.

(a) Give one other metabolic reaction in cells.

any one from:

• respiration

• formation of proteins

• formation / breakdown of glycogen

• breakdown of (excess) protein or formation of urea

• photosynthesis or formation of glucose / starch (in plants)

males have a higher metabolic rate than females after five years of

age

the mean metabolic rate of females decreases faster than males up

to 25 years of age

Calculate the percentage decrease in the mean metabolic rate of males

between 5 years and 45 years of age.

Use the equation:

Decrease in metabolic rate/original metabolic rate x100

Give your answer to 3 significant figures.

17/53×100

32.075472…

32.1

any two from:

allow converse

• (person) R heart rate rose / increased more slowly than

(person) S

• (person) R heart rate levelled off whereas (person) S continued

to increase

• (person) R heart rate rose less (overall / after 5 minutes of

exercise) than S

allow correct use of figures

e.g. R increased (overall) by 39 bpm /

65% and S by 54 bpm / 69%

ignore lack of units

132-78/12

54/12

4.5

A student made the following hypothesis about the heart rate of smokers

and non-smokers during exercise.

“During exercise, the heart rate of smokers increases more than

the heart rate of non-smokers.”

Design an investigation that would allow you to test this hypothesis.

two groups of people − non-smokers and smokers

• have at least five people in each group or large groups

• get each person to do (named) exercise

• controlled variables:

− same number of people in each group or large groups

− same gender

− same level of activity / exercise

− same age

− no health issues / illnesses

− same type of exercise

− same time for exercise

• record heart rate for each person before and after exercise

• calculate increase in heart rate for each person after exercise

• compare results for each group

Limewater goes cloudy when carbon dioxide is added to it.

(b) After 10 minutes the limewater in flask B was cloudy, but the limewater in

flask A remained colourless.

Explain why.

atmospheric air contains less carbon dioxide than exhaled air

allow converse

(flask B goes more cloudy because) carbon dioxide is produced in

(aerobic) respiration (by woodlice)

do not accept anaerobic respiration

Flask A acts as a control in this investigation.

What is the purpose of a control?

) for comparison / to compare

allow answers in the context of the investigation

e.g.

or

to check that no other factor / variable is influencing the results to prove that the results obtained were due to the

woodlice respiring and nothing else

or

to prove that the woodlice produced the carbon

dioxide and nothing else

The student repeated the investigation with no woodlice.

Describe the appearance of the limewater in flask A and flask B after 10

minutes

flask A) would remain colourless

ignore references to clear

allow not cloudy

(flask B) would remain colourless

Exercise cannot be sustained when anaerobic respiration takes place in

muscle cells.

Explain why.

muscles become fatigued / stop contracting

because not enough energy is transferred

C) co2

D) count the bubbles or measure volume of gas In a given time

E) bread making/ brewing

All living cells respire.

(a) Respiration transfers energy from glucose for muscle contraction.

Describe how glucose from the small intestine is moved to a muscle cell.

glucose is absorbed by diffusion into the bloodstream

1

then blood delivers glucose to muscles in capillaries

(b) to stop air getting in

(c) yellow

(d) collect the CO2 / gas with a measuring cylinder / gas syringe

(volume collected) in a certain time using a timer / watch

) Compare anaerobic respiration in a yeast cell with anaerobic respiration in

a muscle cell.

yeast produces ethanol but muscles produce lactic acid

marks can be awarded from correct word or

balanced symbol equations

yeast produces CO2 but muscles do not

answers must be comparative

both release small amounts of energy

Without oxygen

ii) more high/ increased lactic acid

Describe what happens to the rate of blood flow through the athlete’s

muscles during the run.

Use data from Figure 2 in your answer.

I)1.5

increases at first and levels off

ignore subsequent decrease

1

1

1

suitable use of numbers eg

rises to 10 / by 9 (dm3 per min)

or

increases up to 1.5 (min) / levels off after 1.5 (min) (of x axis

Explain how the change in blood flow to the athlete’s muscles helps

him to run.

supplies (more) oxygen

supplies (more) glucose

need ‘more/faster’ once only for full marks

allow removes (more) CO2 / lactic acid / heat as an

alternative for either marking point one or two,

once only

for (more) respiration

1

1

1

releases (more) energy (for muscle contraction)

do not allow energy production or for respiration

The damaged alveolus has a smaller surface area.

1

(b) Less oxygen is taken in