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Biology February Mock > Photosynthesis > Flashcards

Photosynthesis Flashcards

1
Q

Define phosphorylation

A

Adding phosphate to a molecule eg. ADP to ATP

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2
Q

Defin photoposphorylation

A

Adding phosphate to a molecule using light

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3
Q

Define photolysis

A

The splitting of a moleule using light energy

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4
Q

Define hydrolysis

A

The splitting of a molecule using water eg. ATP to ADP

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5
Q

Define redox reactions

A

Reactions that involve:
Reduction = gain of electrons and maybe a gain of hydrogen
Oxidation = loss of electrons and maybe a loss of hydrogen

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6
Q

What is photosynthesis?

A

The process where energy from light is used to break apart water
The hydrogen from water is stored as a fuel in glucose which forms when combined with CO2. O2 is released into atmosphere

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7
Q

Gibe the equation for photosynthesis

A

6CO2 + 6H20 —-> C6H12O6 + 6O2

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8
Q

How is ATP made?

A

Its synthesised by the phosphorylation of ADP using energy from the breakdown of glucose in respiration

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9
Q

How and where is energy stored in ATP?

A

Stored as chemical energy in the phosphate bond

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10
Q

What enzyme catalyses the hydrolysis of ATP into ADP and Pi?

A

ATP synthase

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11
Q

What is a coenzyme and how do they work?

A

A molecule that aids the function of an enzyme

They transfer a chemical group from one molecule to another

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12
Q

Give an example of a coenzyme used in photosynthesis:

A

NADP transfers hydrogen so can either reduce or oxidise a molecule

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13
Q

Where does photosynthesis take place?

A

The chloroplast of a plant cell

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14
Q

What are chloroplasts?

A

Flattened organelles that contain a double membrane (chloroplast envelope)

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15
Q

What are thylakoids?

A

Fluid-filled sacs found in the chloroplast that are stacked into grana

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16
Q

Why do thylakoids have a large surface area?

A

So as much light energy can be absorbed as possible

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17
Q

How are grana linked?

A

Llamelae

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18
Q

What molecules are abundant in the thylakoids membranes?

A

ATP synthase (to produce ATP in light dependent reaction)

19
Q

What pigments do chloroplasts contain and where are they found?

A

Photosynthetic pigments – chlorophyll a, chlorophyll b, carotene
Found in thylakoid membranes and attached to proteins = photo system

20
Q

What are photosynthetic pigments?

A

Coloured substances that absorb light energy

21
Q

What wavelength does photo system 1 absorb?

A

700nm

22
Q

What wavelength does photo system 2 absorb?

A

680nm

23
Q

What is the stroma?

A

A gel-like substance surrounding the thylakoids that contains enzymes, sugars and organic acids required for light independent reaction

24
Q

Briefly describe the light dependent reaction:

A
  • Requires light energy which is absorbed by photo systems
  • Light energy adds a phosphate group to ADP to form ATP
  • NADP converted to reduced NADP
  • H2O oxidised to O2
  • Occurs in thylakoids membranes
25
Q

How is ATP made in the light dependent reaction?

A

Photophosphorylation

26
Q

What is light energy needed for in light dependent reaction? X3

A

1) Making ATP from ADP and Pi = photophosphorylation
2) Making reduced NADP from NADP
3) Splitting water into protons, electrons and oxygen = photolysis

27
Q

What two types of photophosphorylation occur in light dependent reaction?

A

Cyclic and non-cyclic

28
Q

Name the products of non-cyclic photophosphorylation:

A

ATP, reduced NADP and O2

29
Q

What are electron carriers?

A

Proteins that transfer elections

30
Q

What is an electron transport chain?

A

A chain of proteins through which excited electrons flow

31
Q

Describe non-cyclic photophosphorylation:

A
  • Light energy is absorbed by PSII
  • Light energy excites electrons in chlorophyll moving them to a higher energy level
  • High-energy electrons move along the electron transport chain to PSI
  • As electrons move along the chain, they must be replaced so light energy splits water into protons, electrons and oxygen through photolysis
  • Excited electrons lose energy as they move along the ETC
  • Energy used to pump protons INTO THE THYLAKOIDS so higher concentration inside than in the stroma = proton gradient
  • Protons diffuse down their concentration gradient into the stroma via enzyme ATP synthase which combines ADP + Pi to form ATP = chemiosmosis
  • Electrons from NADP, and a proton from stroma, are transferred to form reduced NADP
32
Q

Describe cyclic photophosphorylation:

A
  • Only uses PSI
  • Only produces small amounts of ATP
  • Electrons are recycled repeatedly through PSI and not passed onto NADP
33
Q

Briefly describe the light independent reaction (Calvin Cycle):

A
  • Doesn’t require light energy
  • ATP and reduced NADP (made in light dependent reaction) supply energy and hydrogen to make glucose and CO2
  • Occurs in stroma
34
Q

Describe the Calvin cycle:

A
  1. CO2 enters leaf through stomata and diffuses into the stroma
    Combines with ribulose bisphosphate
    Catalysed by RUBISCO
    Creates 2x GP (3C)
  2. Hydrolysis of ATP provides energy to turn GP into GALP (some converted to useful organic compounds and some is put back into Calvin cycle
    Reduced NADP is recycled into NADP
  3. Two molecules of GALP used to make a hexose sugar
    BUT 5 out of every 6 GALP molecules used to regenerate RuBP which uses ATP
35
Q

What biological molecules are made from GALP and GP?

A
  • Carbohydrates – simple sugars made from joining 2 GALP together, polysaccharides made by joining two hexose sugars together
  • Lipids – made using glycerol which is synthesised from GALP and fatty acids from GP
  • Amino acids – some made from GP
  • Nucleic acids – sugar in RNA (ribose) made from GALP
36
Q

Name of experiment to investigate photosynthesis using extracts of chloroplasts:

A

Hill Reaction

37
Q

Name of redox indicator dye and colour change:

A

DCPIP turns from blue to colourless

38
Q

Describe the Hill Reaction:

A
  1. Cut spinach leaves into pieces, removing tough stalks
  2. Grind leaf with chilled isolation solution
  3. Filter liquid through a funnel with muslin cloth and transfer to centrifuge tubes
  4. Place in centrifuge at high speed for 10 minutes – chloroplast will be observable as a pellet
  5. Get rid of excess liquid
  6. Re-suspend pellets in fresh chilled isolation solution = chloroplast extract = store in ice
  7. Set up a colorimeter with red filter and fill cuvette with chloroplast extract and distilled water
  8. Set up a test tube rack a set distance from lamp
  9. Put a test tube in the rack and fill with a set volume of chloroplast extract and a set volume of DCPIP – mix
  10. Immediately take a sample from test tube and place into a cuvette and record absorbance using a colorimeter – continue doing every 2 mins for 10 mins
  11. Repeat experiment including two controls
39
Q

What will happen to the absorbency as DCPIP becomes reduced?

A

The absorbance will decrease as DCPIP becomes reduced and loses its blue colour

40
Q

Independent variable of Hill Reaction:

A

Light reaching chloroplast samples

41
Q

Dependent variable of Hill Reaction:

A

Amount of DCPIP reduced

42
Q

Control variables for Hill Reaction: x4

A
  • Chloroplast from same species of plants
  • Amount of buffer solution added to each tube 5cm3
  • Amount of DCPIP added to each tube 10cm3
  • Length of time left for
43
Q

What substance does DCPIP take the place of?

A

NADP

Acts as an electron receptog

Biology February Mock (9 decks)

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