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Biology > Section 5- Photosynthesis > Flashcards

Section 5- Photosynthesis Flashcards

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1
Q

What is photosynthesis?

A

The biochemical process where plants absorb light energy using chlorophylls.

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2
Q

What are the 2 main reactions that occur in photosynthesis?

A

The light dependent reaction

The light independent reaction

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3
Q

Where does the light dependent reaction occur?

A

Occurs across the thylakoid membrane.

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4
Q

What is the grana in a chloroplast?

A

Stacks of disk like structures called thylakoids

Thylakoids contain chlorophyll

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5
Q

What is the stroma in a chloroplast?

A

Fluid-like matrix, also contains starch grains.

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6
Q

Where does the light-dependent reaction occur in the chloroplast?

A

Grana/ Thykaloid

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7
Q

Where does the light-independent reaction occur in the chloroplast?

A

Stroma

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8
Q

What are the products of the light-dependent reaction?

A

Reduced NADP
ATP
Oxygen

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9
Q

What are the key steps of non-cyclic photophosphorylation?

A 
Photolysis of water
Photoionising PS2
The electron transport chain
ATP synthesis
Reduction of NADP
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10
Q

What is the photolysis of water in non-cyclic photophosphorylation?

A

A photon strikes water inside thylakoid

Water splits into 2 electrons, 2 hydrogen ions and oxygen

Oxygen releases as waste products

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11
Q

What is the photoionising of PS2 in non-cyclic photophosphorylation?

A

Energy from photon of light is transferred to electrons in PS2

Electrons become energised, leave the photosystem and join electron transport chain.

Pigment becomes oxidised.

Electrons replaced by those from photolysis of water.

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12
Q

What is the electron transport chain in non-cyclic photophosphorylation?

A

Energy from electron pumps hydrogen ion across the membrane into lumen of thylakoid

Once all of energy is used the electron joins PS1.

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13
Q

What is ATP synthesis in non-cyclic photophosphorylation?

A

Electrochemical gradient of hydrogen ion means that they will move back into the stroma by facilitated diffusion

Movement of hydrogen ion = chemiosmosis

Provides energy for phosphorylation of ADP into ATP by ATP synthase

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14
Q

What is the reduction of NADP in non-cyclic photophosphorylation?

A

Electrons in PS1 will become excited by light energy and leave the photosystem into the stroma

Electrons & excess hydrogen ions from photolysis of water are collected by oxidised NADP

Makes reduced NADP

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15
Q

What is the Calvin cycle?

A

CO2 + RuBP catalysed by rubisco- makes 3x Glycerate-3-phosphate.

G3P is reduced to triose phosphate by 1x reduced NADP and 1x ATP.

3 carbon TP is used to recycle RuBP, 5/6 TP converted to RuBP using energy from ATP.

Remaining 1/6 molecules of TP are made into glucose

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16
Q

What other organic compounds are made in the Calvin cycle?

A

Plants will add nitrate from the soil to glucose to make amino acids

Lipids are made from glycerol (produced from triosephosphate) and fatty acids (produced from glycerate-3-phosphate)

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17
Q

What is the light dependent reaction also known as?

A

Non-cyclic photophosphorylation

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18
Q

What is the light independent reaction also known as?

A

The Calvin Cycle

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19
Q

What is cyclic photophosphorylation?

A

Only involves PS1

When light energy excites electrons in PS1 they leave and join electron transport chain

Energy is used to pump hydrogen ions into thylakoid driving process of chemiosmosis

Energy is used to phosphorylate ADP into ATP

Electrons return to PS1

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20
Q

What is the substance that combines with carbon dioxide in a chloroplast?

A

Ribulose bisphosphate

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21
Q

How is NADP reduced in the light-dependent reaction of photosynthesis?

A

Electrons in PS1 become excited by light energy and leave photosystem into stroma.

They’re collected along with excess hydrogen ions from photolysis of water by NADP.

This made reduced NADP

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22
Q

Precisely where within a plant cell are the electron carriers involved in the light-dependent reaction found?

A

On the thylakoid membranes

of the grana in the chloroplast

23
Q

What is the role of ribulose bisphosphate in the Calvin cycle?

A

It combined with carbon dioxide to produce 2 molecules of glycerate-3-phosphate

24
Q

How is reduced NADP, from the light-dependent reaction, used in the light-independent reaction?

A

Used to reduce glycerate-3-phosphate to triose phosphate

25
Q

Apart from reduced NADP, which other product of the light-dependent reaction is used in the light-independent reaction?

A

ATP

26
Q

Where in the plant cell is the enzyme that is involved in the Calvin Cycle found?

A

Stroma of the chloroplasts

27
Q

What proportion of TP is converted to RuBP?

A

5/6

28
Q

How many carbons does RuBP, G3P, TP and glucose have?

A

RuBP- 5c

G3P- 6c

TP- 3c

Glucose- 6c

29
Q

What is most of the energy from the sun, fixed into?

A

Chemical energy by photosynthesis

30
Q

Why is there no build-up of phosphate ions when they enter chloroplasts?

A

Used in phosphorylation of ATP in the light-dependent reaction

Catalysed by ATP synthase

31
Q

Why can only triose phosphate be transported via a specific carrier protein?

A

Carrier proteins are complementary

Have tertiary structure specific to substrate

32
Q

What is the role of coenzymes in a leaf cell?

A

NAD can accept hydrogen to be reduced

Reduced NAD carries electrons to electron transport chain

Coenzyme A carries acetate to Krebs cycle

33
Q

How would the rate of photosynthesis affect the rate of translocation?

A

If photosynthesis decreases, the rate of translocation will decrease

Less sucrose will be actively transported into the phloem so less decrease in the water potential

Less water diffuses in by osmosis

Leads to less pressure gradient

34
Q

What is the purpose of chromatogrpahy?

A

To separate different components in a sample

35
Q

What are the factors affecting the rate of migration of different pigments?

A

Solubility

Mass

Affinity to paper

36
Q

What is the formula for Rf value?

A

Distance moved by pigment
/
Distance moved by solvent

37
Q

What is the procedure to using chromatography to separate photosynthetic pigments?

A
  1. Grind leaf sample onto filter paper on pencilled line
  2. Suspend paper in solvent but just so the bottom is touching
  3. Once solvent has run up paper, mark pencil line of distance travelled
  4. Find Rf value for each pigment spot
38
Q

In chromatography, why is it important to use a pencil line and not pen?

A

A pen may dissolve in the solvent

39
Q

Why do chlorophyll contain several different photosynthetic pigments?

A

So they can absorb energy from a wide range of wavelengths

40
Q

What is the function of dehydrogenase in chloroplasts?

A

It catalyses the acceptance of electrons by NADP in the light-dependent reaction

41
Q

What is the purpose of DCPIP?

A

Redox indicator that acts as an alternate electron acceptor instead of NADP

Turns blue to colourless when reduced

42
Q

Why is the chloroplast chilled in an ice-bath?

A

To lower activity of enzymes to prevent them breaking down the chloroplasts

43
Q

What is the control in the photosynthesis practical?

A

Fill capillary tube with chloroplast and distilled water

44
Q

Why are the stalks of the leaves removed in the photosynthesis practical?

A

They do not contain any chloroplasts

45
Q

What is the loose procedure to investigating the effect of different wavelengths of light using DCPIP?

A

Observe capillary tubes filled with chloroplast extract and DCPIP solution under different colour wavelengths

Time how long it takes solution to match control tube (green)

46
Q

How is the rate of reaction calculated in the DCPIP practical?

A

Rate= 1000/time

47
Q

In the photosynthesis practical, using DCPIP, an additional tube containing oxidised DCPIP without leaf extract was included.
Why?

A

To prove presence of chlorophyll is causing reduction reaction

48
Q

In the photosynthesis practical with DCPIP, what causes the DCPIP to change colour?

A

Reduction of DCPIP by electrons

From light-dependent reaction

49
Q

In the photosynthesis practical, with DCPIP, why is a tube set up with DCPIP, no leaf extract, in light?

A

To show light doesn’t affect DCPIP, causing colour change

Shows chloroplasts are needed

50
Q

In the photosynthesis practical into the effect of different wavelengths of light, what is the reason for the change when the tube is exposed to green light?

A

Chlorophyll doesn’t absorb light of wavelength

Green light can be used

Little photosynthesis

51
Q

Other than the temperature and pH, give two factors which should be kept constant during an investigation into photosynthesis?

A

Light intensity

Photosynthesising cells number

Carbon dioxide

Time

52
Q

If no buffer was used, what would happen to the pH of a solution in a photosynthesis practical?

A

pH increase

More CO2 removed

53
Q

Why would reducing light intensity affect the amount of oxygen released by seaweeds?

A

Light is limiting factor

Fewer electrons released from chlorophyll

Less photolysis of water

Biology (25 decks)

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