3.5.1 Photosynthesis Flashcards

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1
Q
A
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2
Q

Describe the structure of a chloroplast

A

Double membrane bound thylakoid stacks (grana). Linked by thylakoid membrane (lamellae). ATP synthase and chlorophyll pigments present in thylakoid membrane/stroma

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3
Q

Why do plants have accessory pigments?

A

To absorb a wider range of wavelengths of light

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4
Q

what evidence is there that chloroplasts used to be free-living cyanobacteria?

A

Own circular DNA free from histones, 70S ribosomes, double membrane surrounding them

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5
Q

What is found within the stroma?

A

Grana/oil droplets/starch/enzymes/sugars/ ribosomes/DNA

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6
Q

Where does the light dependent stage of photosynthesis take place?

A

Thylakoid membrane

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7
Q

Where does the light independent stage of photosynthesis take place?

A

Stroma

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8
Q

What structural features of the thylakoids increase rate of photosynthesis?

A

Stacked into granum/increased surface area/maximum absorption of light in membrane

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9
Q

What is a photosynthetic pigment?

A

Coloured substances that absorb the light energy needed for photosynthesis (e.g. chlorophyll)

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10
Q

What is a thylakoid?

A

A system of interconnected, flattened fluid filled sacs with proteins embedded in the membranes, where the light dependent stage takes place

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11
Q

Describe the stroma

A

Gel-like fluid surrounding the thylakoids. contain all the enzymes, sugars and organic acids needed for the light independent reaction.

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12
Q

Where the Calvin cycle occurs ?

A

Stroma

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13
Q

What are the products of the Calvin cycle?

A

NADP, ADP and glucose

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14
Q

What happens to light energy when it enters the chloroplast ?

A

Absorbed by the photosynthetic pigments and used to excite electrons so that they can leave chlorophyll (photoionisation). They are then replaced by the splitting of water (photolysis) into H+ ions, electrons and oxygen.

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15
Q

How do the electrons move along the electron transport chain in photosynthesis?

A

A series of redox reactions

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16
Q

State the name for the synthesis of ATP using light ?

A

Photophosphorylation

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17
Q

What is produced from the photolysis of water?

A

Two hydrogen ions, one oxygen, two electrons

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18
Q

What happens to the electrons when they leave the electron transport chain (photosynthesis) ?

A

Combine with one hydrogen ion and NADP to form NADPH

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19
Q

How many times does the Calvin cycle have to happen to form one glucose molecule ?

A

Six

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20
Q

How does GP turn into TP?

A

It is reduced. The H atom comes from NADPH and ATP provides energy for the endothermic reaction

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21
Q

What does RUBISCO do ?

A

Combines CO2 with RuBP to make 2 molecules of GP

22
Q

What is 5 carbon sugar which is part of the Calvin cycle ?

A

RuBP (Ribulose BisPhospate)

23
Q

What is photolysis?

A

The process where light energy is used to split apart the strong bonds in water molecules. Hydrogen from the breakdown of water is stored in glucose, which is formed when the hydrogen is combined with CO2. O2 is formed and released into the atmosphere.

24
Q

What does the hydrolysis of ATP provide ?

A

an immediate supply of energy for biological processes

25
Q

Why do thylakoids have a large surface area ?

A

to allow as much light energy to be absorbed as possible

26
Q

Why are lots of ATP synthase molecules present in the thylakoid membranes?

A

To produce ATP in the light dependent reaction

27
Q

What is the electron transport chain?

A

A chain of proteins through which excited electrons flow.

28
Q

How do H+ help to generate ATP in photosynthesis?

A

H+ move down their concentration gradient, into the stroma via the enzyme ATP synthase. The energy from this movement combines ADP with Pi to form ATP

29
Q

What is cyclic photophosphorylation and what are its products

A

Light absorbed by photosystem 1 excites electrons that are then passed back to the electron transport chain. H+ ions are pumped and ATP is produced. Oxygen and reduced NADP are NOT produced

30
Q

what is the lolipop experiment? Could you draw it?

A
31
Q

What are the limiting factors of photosynthesis

A

LIght, CO2, Temperature

32
Q

Why do the Light independent reactions stop in the dark

A

As ATP and reduced NADP quickly run out. Hence there is no energy / hydrogen for the reduction of GP to triose phosphate

33
Q

What happens to the calvin cycle if CO2 is removed

A

There will be an accumulation of RuBP as there is no CO2 for Rubisco to fix and the creation of GP will cease.

34
Q

What experiment proved the sequence of events in the calvin cycle? Briefly describe it

A

Lolipop experiment. Radioactive CO2 was added to algae. Samples of the algae were taken over time and the compounds containing C-14 slowly built up. The sequence of which compounds showed readioactivity was used to re-create the steps of the cycle

35
Q

what are 2 reasons for cyclic photophosphorylation

A
  1. The calvin cycle needs more ATP than redNADP. 2 Guard cells use it to couple opening / closing to thre presence of light
36
Q

Draw the calvin cycle

A
37
Q
A
38
Q
A
39
Q

What happens when light is absorbed by chlorophyll in non-cyclic photophosphorylation?

A
40
Q

What is photoionisation?

A
41
Q

What happens to the electrons that leave photosystem 1 and 2

A
42
Q

How are the electrons lost by photosystem 1 replaced?

A
43
Q

How are the electrons lost by photosystem 2 replaced

A
44
Q
A
45
Q
A
46
Q

what happens next

A
47
Q

what happens next

A
48
Q

what happens next

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49
Q

what happens next

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50
Q

what happens next

A
51
Q

In the lolipop what was the independent variable?

A

Time: algae samples were killed by dropping in hot methanol every few seconds so Calvin could work our the order in which C-14 appeared in different compounds