Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Biology IGCSE > Photosynthesis > Flashcards

Photosynthesis Flashcards

(60 cards)

Start Studying
1
Q

Word equation for photosynthesis

A

Carbon dioxide + water –> Glucose + oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Chemical equation for photosynthesis

A

6CO2 + 6H2O –> C6H12O6 + 6O2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Pondweed photosynthesis experiment using CORMS

A

Change : Distance between lamp and beaker containing pondweed.
Organism: Elodea (pondweed)
Repeat: 10 x
Measure: Number of 02 bubbles produced in a minute at each distance. To improve experiment measure volume of 02 bubbles using gas syringe.
Same: Length of elodea, temperature, species of plant, type of light bulb, CO2 concentration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Control variables in pondweed experiment

A

Length of elodea used, temperature of beaker, species of plant, type of light bulb, CO2 concentration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Independent variable in pondweed experiment

A

Intensity of light/ distance between lamp and pondweed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Dependant variable of pondweed experiment

A

Number of oxygen bubbles produced by pondweed in a minute or volume of oxygen bubbles produced by pondweed in a minute

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Improvements to pondweed experiment

A

Keeping temperature controlled so rate of photosynthesis isn’t affected: Put the elodea in a boiling tube of water which is then placed in a beaker with a thermometer, to act as a water bath.
Accurate measurement of O2: Collect the gas (oxygen) produced in an inverted measuring cylinder to measure the volume of oxygen produced per time. Or use a gas syringe.
CO2 concentration: Add a fixed mass of sodium bicarbonate to water to provide a higher, constant concentration of CO2.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Steps for testing a leaf for starch.

A

Destarch the leaf for 24 hours in the dark before starting the experiment.
Place leaf in boiling water for 1 min.
Turn off the bunsen burner and transfer the leaf into a test tube containing ethanol and then place the test tube in hot water (acts as hot water bath)
Place the leaf in hot water to soften it.
Spread the leaf out on a white tile and cover it with Iodine solution.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Why is the leaf de-starched in the experiment?

A

So that the leaf is free from starch at the start of the experiment. Ensures any starch tested was made from glucose made in photosynthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How does placing the leaf in the dark destarch it?

A

Without any sunlight, photosynthesis doesn’t take place in the leaf. Photosynthesis produces glucose which is stored as starch in the leaf. Without photosynthesis, no glucose is produced and no starch is stored. The starch stores in the leaf are converted to glucose for respiration, to produced energy for the plant. The starch stores are used up.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Why is the leaf placed in boiling water at the start of the experiment?

A

To kill the tissue and break down the cell walls.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why is the leaf boiled in ethanol?

A

To dissolve the chlorophyll so colour change can be seen more clearly.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why is the leaf placed back in hot water/ rinsed with water?

A

To soften the leaf/ to allow Iodine to penetrate the leaf.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What colour does Iodine turn in presence of starch?

A

Yellow –> blue/black

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How would you change the experiment if you wanted to show that a leaf needed light for photosynthesis?

A

Cover part of the leaf so it isn’t exposed to sunlight. Only the part of the leaf exposed to sunlight will produce starch and turn blue/black

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How would you change the experiment if you wanted to show that chlorophyll is required for photosynthesis?

A

Use a variegated leaf. The white parts of leaf lack chlorophyll. Only the green parts of the leaf (containing chlorophyll) will produce starch. Green parts of leaf contain the green pigment chlorophyll which is used in photosynthesis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How would you change the experiment if you wanted to show that carbon dioxide is needed for photosynthesis?

A

One leaf of a plant is enclosed in a conical flask (or
plastic bag) containing soda lime to absorb the carbon dioxide and this leaf is compared
to another enclosed in a flask but without the soda lime. Only the leaf that had access to
carbon dioxide (not soda lime one) produces starch.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Explain why the ‘Testing a leaf for starch’ experiment shows what is needed for photosynthesis.

A

Photosynthesis produces glucose, which is stored in the leaves as starch. When a leaf has photosynthesised, starch will be present.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Safety precautions for ‘testing a leaf for starch’ experiment.

A

Ethanol is flammable so turn off the bunsen burner when boiling the leaf in ethanol. Safest way to heat ethanol is in an electric water bath.
Iodine is an irritant to the eyes so wear goggles.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Describe how energy for photosynthesis reaction is gained by plants.

A

Light is absorbed by chloroplasts/ chlorophyll

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Limiting factors of photosynthesis

A

Carbon dioxide, temperature and light intensity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Describe and explain the waxy cuticle

A

Protective layer, prevents water from evaporating

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Describe and explain the upper epidermis

A

Thin and transparent to allow light to penetrate through to the palisade mesophyll layer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Describe and explain the palisade mesophyll

A

Long, thin cells tightly packed with lots of chloroplasts to absorb more light, maximising photosynthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Describe and explain the spongy mesophyll
Contains air spaces that increase surface area to volume ratio for the diffusion of gases
26
Describe the lower epidermis
Contains guard cells and stomata
27
Describe and explain the guard cell
Opens and closes the stomata to allow CO2 to diffuse in and oxygen to diffuse out
28
Describe and explain the stomata
Where gas exchange takes place. Evaporation of water also takes place here.
29
Describe and explain the vascular bundle
Contains xylem and phloem to transport substances to and from the leaf
30
Describe and explain the xylem in the leaf
Transports water and mineral ions from the root hair cell into leaf for mesophyll cells to use in photosynthesis and for transpiration from stomata
31
Adaptations of root hair cell
Hair like extension create high surface area for maximum water and mineral absorption Lots of mitochondria so lots of energy produced for active transport of minerals No chloroplasts, no photosynthesis Thin walled to provide short distance
32
Why do stomata open in the light?
In light, guard cells photosynthesise, sugar concentration increases (glucose produced) so water potential decreases. Water moves into the guard cells by osmosis so they become turgid. Because of the inflexible inner cell wall the guard cells change shape, opening the stomata.
33
Why do stomata close in the dark?
Photosynthesis doesn't occur in the dark. Sugar concentration falls (due to use of glucose in respiration), water potential increases and water moves out of the guard cells. This causes the guard cells to become flaccid and the stomata close.
34
What are the 3 main minerals plants need?
Nitrates, magnesium ions and phosphates
35
What are nitrates used for in plants?
Used to create amino acids and proteins, needed for cell growth
36
What are magnesium ions used for in plants?
Used to make chlorophyll which is needed for photosynthesis
37
What are phosphates used for in plants?
Used to make nucleic acids (RNA and DNA) and cell membranes
38
Observation of a plant with a nitrate deficiency
Stunted growth
39
Observation of a plant with a magnesium deficiency
Yellow leaves
40
Observation of a plant with a phosphate deficiency
Poor root growth, purple leaves
41
How is the leaf adapted for photosynthesis?
Thin so short diffusion distance Leaf is wide for large surface area for diffusion Upper epidermis transparent to allow light through Palisade mesophyll cells contain many chloroplasts to absorb light Spongy mesophyll have air spaces for gas exchange/diffusion Stomata absorbs carbon dioxide Xylem/vascular bundle brings water for photosynthesis
42
Describe how gas exchange occurs in a plant during respiration
Oxygen diffuses down a concentration gradient from a high concentration (outside leaf) to low concentration (inside leaf). Carbon dioxide diffuses down a concentration gradient from a high concentration (inside leaf) to a low concentration (outside leaf)
43
Describe how gas exchange occurs in a plant during photosynthesis
Oxygen diffuses down a concentration gradient from a high concentration (inside leaf) to low concentration (outside leaf). Carbon dioxide diffuses down a concentration gradient from a high concentration (outside leaf) to a low concentration gradient (inside leaf)
44
Explain the function of the phloem
Translocation of sugars. Transports sucrose (made in photosynthesis) and amino acids between leaves and other parts of the plant.
45
How are water and minerals absorbed by root hair cells?
Water enters root hair cell by osmosis, moving down a water potential gradient from high water potential to low water potential across a semi-permeable membrane. Mineral ions are actively transported into root hair cells, moving against a concentration gradient from low water concentration (soil water) to high concentration (inside root hair cell) requiring energy.
46
Define transpiration
Transpiration is the evaporation of water from the surface of a plant.
47
Describe how temperature affects transpiration
Transpiration increases as temp increases. Higher temp means water will evaporate more quickly from the leaves of a plant as the water molecules have more kinetic energy.
48
Describe how humidity affects transpiration
Transpiration increases as humidity decreases. Humid air contains lots of water vapour, smaller concentration gradient, so transpiration decreases.
49
Describe how wind speed affects transpiration
Transpiration increases as wind speed decreases. In moving air, water vapour will be blown away from leaf as fast as it diffuses out, speeding up transpiration as there is a high concentration gradient.
50
Describe how light intensity affects transpiration
Light itself doesn't affect transpiration however in daylight the stomata of leaves are open to supply carbon dioxide for photosynthesis. This allows more water to diffuse out of the leaves and into the atmosphere.
51
Describe how the plant reduces rate of transpiration if water is in short supply
If water is in short supply, plant is losing water by transpiration more than it is being taken up by roots. Plant may start to wilt. Guard cells become flaccid and stomata start to close, reducing transpiration
52
Which factors affect transpiration?
Temperature, wind speed, humidity, light intensity
53
Describe how to set up a potometer to investigate effect of light intensity on transpiration
Cut shoot underwater Dry leaves of the shoot Remove capillary tube from beaker to allow one air bubble to form then place tube back in water Set up lamp 10cm from plant Record starting position of bubble using ruler Leave for 30 mins Record end position of bubble Rate of transpiration = distance moved by air bubble/time taken Further the bubble travels in same time period, greater the rate of transpiration Repeat experiment but change light intensity by increasing distance from lamp.
54
Describe how you would alter potometer experiment to investigate the effect of wind speed on transpiration
Set up a fan or hairdryer 10cm away from plant instead of a lamp Repeat experiment but alter distance of fan from plant
55
Describe how you would alter potometer experiment to investigate the effect of humidity on transpiration
Spray water in a plastic bag and wrap around plant Repeat but without plastic bag
56
Describe how you would alter potometer experiment to investigate the effect of temperature on transpiration
Place plant in a warm room then repeat experiment and place plant in a cold room instead of using lamp.
57
Why does the shoot have to be cut underwater for potometer experiment?
To prevent air entering the xylem.
58
What are the limitations of potometer experiment?
Equipment has a leak - Ensure equipment fits tightly and assemble underwater to produce a good seal Plant cutting has a blockage - Cut stem underwater and assemble equipment underwater to prevent air bubbles from entering the xylem Potometer shows no change - Use plant cuttings as soon as they have been cut. Transpiration rates may slow as cuttings are no longer fresh
59
Describe what happens to water after it has been absorbed by root hair cells, how does it reach leaves?
Water moves up xylem due to transpiration stream as water is loss from stomata. Xylem replaces water lost.
60
How does transpiration help plants?
Draws water up to leaves which is needed for photosynthesis Transports mineral ions Evaporation cools plant Prevent wilting

Biology IGCSE (20 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions