Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A-level biology component 1 (+immunology) > Photosyntheis > Flashcards

Photosyntheis Flashcards

1
Q

What is photosynthesis?

A

a process that synthesises large organic molecules form simple inorganic molecules using energy from sunlight

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

Where are photosynthates produced?

A

at the source (the leaves)

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

What is the main photosynthetic tissue in a leaf?

A

palisade mesophyll

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

What are stomata essential for?

A

gas exchange in a leaf, without this photosynthesis would not occur

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

In the lab, how can the density of stomata be studied?

A
  1. Apply clear nail polish to the lower epidermis of a leaf between the veins and allow it to dry.
  2. Using forceps, peel the nail polish from the leaf to produce a replica of the lower epidermis.
  3. Place the replica on a microscope slide and count the number of stomata using the microscope.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are four adaptations of the leaf for photosynthesis?

A

•large SA
•Thin so light penetrates photosynthetic tissues
•densely packed palisade layer, palisade cells contains chloroplasts, air spaces to allow carbon dioxide to diffuse to photosynthesising cells
•Air spaces between spongy mesophyll to allow CO2 to diffuse photosynthetic cells (maintains O2 conc grad)

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

Why is it important that biochemical reactions in cells often involve cyclic metabolic pathways which occur in compartments (such as chloroplasts) inside cells?

A

•Reactions can occur in small volume/isolation of enzymes/reactants.
•membranes isolate reactions within organelles, keeping products separate from cytoplasm
•mitochondria can be positioned close to areas needing ATP/movement of organelles within cytoplasm.

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

What does the LDS make that the LIS uses?

A

ATP and NADPH

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

Where does the LDS take place?

A

Thylakoid membrane and thylakoid cavity of chloroplast

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

What is the function of the LDS?

A

Involves the conversion of light energy into chemical energy (ATP and NADPH)

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

What is the location of the LID?

A

Stroma of chloroplast

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

What is the function of the LIS?

A

Uses the products of the light dependent reaction to produce organic molecules such as glucose

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

where are photosynthetic pigments located?

A

within the thylakoid membranes of the chloroplasts

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

What is the role of photosynthetic pigments?

A

To capture energy from the sun and convert it to chemical energy

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

What are the two main types of photosynthetic pigment in flowering plants?

A

Primary pigment
Accessory Pigments

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

What is the primary pigment?

A

Chlorophyll a (absorbs blue and red wavelengths of light)

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

What are the accessory pigments?

A

carotenoids (xanthophyll and carotene)- absorb blue/violet light

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

why are accessory pigments important?

A

as they absorb wavelengths of light not absorbed by the primary pigments- this ensures a wider range of wavelengths are absorbed, increasing the efficiency of photosynthesis

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

what macronutrient is needed to produce chlorophyll a?

A

magnesium- one electron is energised from each mg2+ to a higher energy level (when absorbed), the fatty acid tail holds chlorophyll molecule in the thylakoid membrane

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

What can chromatography be used to separate?

A

photosynthetic pigments

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

How does chromatography work?

A
  1. Tear up leaves and grind with aetone to form a dark green pigment solution. 2. Use a capilary tube to spot the pigment on to chromatography paper
  2. Place the chromatography paper into a solvent (such as acetone/petroleum)
  3. Remove the chromatography paper once the solvent has travelled to the top of the strip. Observe the different distances the pigments have travelled.
  4. Calculate the Rf value for each pigment (distance travelled by the pigment divided by the distance travelled by the solvent).
  5. Identify each pigment by comparing the Rf values to known values (but must use same solvent for the known and unknown pigment)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Why do we add acetone when grinding the leaves (chromatography)?

A

Acetone (organic solvent) dissolves the phospholipid membrane to extract the pigments from the thylakoid membranes in the chloroplasts

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

Why do we need a solvent (chromatography)?

A

The running solvent dissolves the pigments (solutes) and carries the pigment up the chromatography filter paper

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

why do the pigments travel different distances?

A

The more soluble a substance (pigment) is in that solvent, the further it moves up the chromatography paper

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Why must the pencil line be drawn above the the solvent?

A

other wise dissolves in the solvent (off the paper)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How is the Rf value calculated?

A

distance travelled by pigment (from the origin)/distance travelled by solvent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is the absorption spectrum?

A

Graph that shows the amount of light absorbed by chlorophyll a and the accessory pigments at each wavelength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Why is so little light absorbed between 530nm and 640nm?

A

530-640 of the range of light wavelengths at which green light is reflected by chlorophyll pigments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what wavelengths does chlorophyll a absorb?

A

425nm + 675nm (red and blue)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What are the wavelengths absorbed by chlorophyll b?

A

450 and 640nm (blue and orange)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What wavelengths are absorbed my carotenoids?

A

475nm (blue)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What is the action spectrum?

A

A graph that shows the rate of photosynthesis at different wavelengths of light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What experiment could be conducted to measure the rate of photosynthesis?

A

count the number of bubbles (oxygenated) produced by pond weed (an underwater plant) over a certain period of time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What is the relationship between the absorption spectrum and the action spectrum?

A

There is a close correlation between greater light absorption and after faster rate of photosynthesis suggesting that the two the two pigments are responsible for absorbing the wavelengths of light used in photosynthesis to make glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Where are photosystems located?

A

in the thylakoid membranes of chloroplasts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

what is the role of photosystems?

A

-absorb photons of light energy.
-act as transducers by transferring this light energy to high energy electrons.
-this energy can then be used to fuel proton pumps and the synthesis of ATP.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What is the photo system structure?

A

-accessory pigments are grouped into clusters with associated proteins, forming an antenna complex.
-These pigments absorb photons of light energy and funnel this energy down the antenna complex to the reaction centre below.
-Chlorophyll a molecules are found in the reaction centre below the antenna complex.
-When photons of light energy reach chlorophyll a in the reaction centre, electrons are excited to become high energy electrons

38
Q

What are the two photosystems involved in the LDR?

A

-PHOTOSYSTEM I (PSI) or P700 - best absorbs light at 700nm wavelength
-PHOTOSYSTEM II (PSII) or P680 - best absorbs light at 680nm wavelength

39
Q

What does the LDR include?

A

•Requires light energy
•Takes place in the thylakoid membranes and thylakoid cavity.
•ATP is synthesised from ADP and Pi.
•This is photophosphorylation as light energy is involved.
•The splitting of water using light is involved and is known as photolysis
•NADP is reduced to form NADPH/H+ (reduced NADP).
• Oxygen gas is released as a by product.

40
Q

What are the two LDR’s in higher plants?

A

•Non-Cyclic Photophosphorylation
•Cyclic Photophosphorylation

41
Q

describe the LDR reactions that take place at the thylakoid membrane-

A

-Photosystem II (PSII) and Photosystem I (PSI) in thylakoid membranes;
-Accessory pigments {e.g. chlorophyll b / β-carotene / xanthophyll} absorb a wider range of different wavelengths of light (pass the energy to chlorophyll a);
-Electrons in chlorophyll a (in reaction centre) get excited to a higher energy level;
-High energy electrons released down the electron transport chain from PSII
-Electrons lose energy + activate proton pumps / build electrochemical gradient in thylakoid space;
-ATP made by combining ADP + Pi at ATP synthase / stalked particle;
-High energy electrons (from PSI reaction centre)and H+ ions reduce NADP to NADPH;
-Photolysis is light activated splitting of water to provide electrons to replace those lost from chlorophyll a (2H20 → 4H+ + 4e- + O2) in PSII

42
Q

What is the effect of the high concentration of H+ ions in the thylakoid space?

A

Becomes acidic- low pH

43
Q

What is photolysis?

A

the splitting of water using light It occurs in the thylakoid cavity

44
Q

What happens during photolysis?

A

-Water splits into oxygen hydrogen ions and electrons.
-The electrons replace those lost by photosystem II, making the chlorophyll molecule stable.
-The protons help maintain the electrochemical gradient between the thylakoid cavity and the stroma .

45
Q

Where does cyclic photophosphorylation occur?

A

in bacteria and primitive plants

46
Q

Why does higher plants use the pathway cyclic photophosphorylation?

A

to provide extra ATP, especially when CO2 is in short supply

47
Q

What photosystem is involved in cyclic photophosphorylation?

A

Only photosystem I-
-light energy is absorbed at PSI and channelled to chlorophyll a
-Electrons in the chlorophyll a become excited, energised and released. They are accepted by an electron acceptor and eventually passed along the same transfer chain as that used by the electrons from PSIl.
-Protons are pumped into the thylakoid space and ATP is produced from ADP + Pi.
-The same chemiosmotic theory as that used to describe the Z scheme is believed to be involved in the production of ATP.
-The electrons excited and released from PSI return to PSI.

48
Q

What type of photophosphorylation involves photolysis?

A

non-cyclic

49
Q

Where do the electrons and up in cyclic photophosphorylation?

A

Return to PSI

50
Q

Where do the electrons and up in non cyclic photophosphorylation?

A

NADPH

51
Q

What is the product in cyclic photophosphorylation?

A

ATP

52
Q

What are the products in non cyclic photophosphorylation?

A

ATP, O2, NADPH

53
Q

In non-cyclic photophosphorylation where does PSII obtain replacement electrons from?

A

photolysis of water

54
Q

non-cyclic photophosphorylation where does PSI obtain replacement electrons from?

A

PSII (low energy electrons that have travelled down the ETC)

55
Q

In cyclic photophosphorylation what happens to the electron excited and released from PSI?

A

They pass down an electron transport chain and then return to PSI

56
Q

In non-cyclic photophosphorylation, what happens to the O2 produced from photolysis?

A

Oxygen is released as a waste gas or used during aerobic respiration

57
Q

When might plants shift from non cyclic photophosphorylation to cyclic photophosphorylation?

A

A mechanism of generating some extra ATP in the chloroplast because it is needed in the calvin cycle when the chloroplast is low on ATP

58
Q

What does the LIS (calvin cycle) not require?

A

light

59
Q

What does the LIS/Calvin Cycle do?

A

It uses the products of the light dependent stage of photosynthesis (ATP and reduced NADP) to fix carbon dioxide from the atmosphere to organic molecules.

60
Q

Where does the LIS take place and who was it discovered by?

A

-it takes place in the the stroma of the chloroplast and was discovered by melvin calvin

61
Q

What is the process of the calvin cycle?

A

-CO2 from atmosphere is fixed with RuBP (5C).
-Enzyme RuBisCo catalyses this reaction
-Results in the formation of an unstable 6C compound which splits into two molecules of Glycerate-3-phosphate (3C).
-Glycerate-3-phosphate is then reduced using reduced NADP produced during the light dependent stage.
-ATP from the light dependent stage is also required. ATP is hydrolysed and the phosphate transferred to Glycerate-3-phosphate, resulting in the formation of two molecules of triose phosphate (3C).
-One carbon atom of the 6 available is removed from the Calvin cycle and can be used to produce organic molecules such as glucose.
-Five carbon atoms remain in the Calvin cycle and are used to regenerate RuBP so the cycle can begin again

62
Q

How many times does the calvin cycle go around to make 1 glucose?

A

6x

63
Q

What happens to 1 out of 6 carbon atoms from the 2 triose phosphates in the calvin cycle? 1

A

-They are not recycled
-They leave the Calvin cycle and form hexose phosphates, which ultimately yield sucrose, starch and cellulose.

64
Q

What can sugars produced during carbon metabolism can also act as? 2

A

carbon skeletons and can be used for other metabolic reactions like the production of amino acids and lipids.

65
Q

What are the inorganic nutrients in plant metabolism?

A

Nitrates- Taken up by roots and transported in xylem & amino acids in the phloem
Magnesium- Absorbed as Mg2+ and transported in the xylem.
Phosphates- Absorbed as PO4- by the roots and transported in xylem

66
Q

What is the function of nitrates in plant metabolism?

A

Synthesis of proteins
Synthesis of nucleic acids/DNA/RNA/Nucleotides

67
Q

What are the symptoms of nitrate deficiency in plants?

A

Reduced growth of organs
Chlorosis- yellow leaves due to inadequate chlorophyll production so plant no longer able to absorbs light energy

68
Q

What is the function of Mg2+ in plant metabolism?

A

-for chlorophyll production
-and activation of ATPase

69
Q

What is a symptom of mg2+ deficiency in plants?

A

Pronounced chlorosis between veins of older leaves as existing Mg2+ is moved and transported to new leaves.

70
Q

What is the function of phosphates in plant metabolism?

A

Form phospholipids
Form nucleotides (ATP/DNA/RNA) along with nitrogen.

71
Q

What is a symptom of phosphate deficiency in plants?

A

Stunting of plant growth.

72
Q

What are the limiting factors that affect the rate of photosynthesis?

A

-Temperature
-CO2 conc
-Light intensity

73
Q

What does temperature do?

A

Influences enzyme activity

74
Q

What is the effect of enzyme denaturation on the rate of photosynthesis?

A

Tertiary structure of the active site changes shape (e.g. Rubisco), therefore is no longer complementary to its substrate, no ESC form and the rate of reaction slows down (CO2 fixation).

75
Q

Why does an increase in temp speed up the rate of the LIS more than it speeds up the rate of the LDR?

A

The light dependent stage is much less dependent on enzyme activity than the light independent stage.

76
Q

How does temp affect the overall rate of photosynthesis?

A

-An increase in temp speeds up the LIS more than it speeds up the LDS.
-The supply of products from the LDS (ATP and reduced NADP) will not be able to keep up with the demand from the LIS.
-The overall rate of photosynthesis will become limited by the supply of reduced NADP and ATP.

77
Q

During photosynthesis, what happens to CO2?

A

it is fixed to form carbohydrates

78
Q

Why does the conc of CO2 often limit the rate of photosynthesis?

A

it makes up only 0.035% of atmospheric air

79
Q

What is a physical change that could occur in a leaf that might result in the rate of photosynthesis decreasing at very high CO2 concs?

A

•CO2 diffuses into leaves and dissolves in water
•The enzyme carbonic anhydrase catalyses the reaction
•Carbonic acid is formed which dissociates to form H+ ions and HCO3- ions
•The accumulation of H+ causes cells to become more acidic
•The acidity denatures enzymes in mesophyll cells in the leaves

80
Q

What is the role of light in photosynthesis?

A

-Light = essential for the excitation of electrons and for photolysis in the light dependent reaction.
-As light intensity increases so too does the rate of cyclic and non-cyclic photophosphorylation

81
Q

What affect does light intensity increasing the rate of cyclic and non cyclic photophosphorylation on the yield of photosynthates?

A

-As the light dependent reaction speeds up ATP and reduced NADP are produced at a faster rate.
-They enter the calvin cycle and organic molecules are produced at a faster rate.

82
Q

What are the physical changes that could occur in a leaf that might result in the plateau at high light intensity?

A

At high light intensity temperatures are also high so stomata close to reduce transpiration/wilting

83
Q

What is the compensation point?

A

When the rate of photosynthesis is equal to the rate of respiration

84
Q

What is RuBisCo?

A

Enzyme that fixes carbon dioxide onto ribulose bisphosphate

85
Q

What is Photo-phosphorylation?

A

Phosphorylation of ADP to ATP using light energy.
Can be cyclic or non-cyclic

86
Q

What is the antenna complex?

A

Clusters of associated proteins which absorb photons of light energy and funnel this energy downwards

87
Q

What is the reaction centre?

A

Where chlorophyll a is found, below the antenna complex

88
Q

What are photosystems?

A

Transducers which transfer light energy to high energy electrons.

89
Q

What are pigments?

A

Protein that absorbs light energy from the sun and convert it into chemical energy.

90
Q

What is the LDR?

A

Stage involving the conversion of light energy into chemical energy (ATP and NADPH)

91
Q

What is the LIDR?

A

Stage using the products of the light dependent reaction to produce organic molecules such as glucose.

92
Q

What is the palisade mesophyll?

A

The main photosynthetic tissue in a leaf

A-level biology component 1 (+immunology) (7 decks)

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