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Biology Noor > 13.3 Photosynthesis > Flashcards

13.3 Photosynthesis Flashcards

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1
Q

What is the word and symbol equation for photosynthesis?

A

Word: Carbon dioxide + Water —> Glucose + Oxygen
Symbol: 6CO2 + 6H2O —> C6H12O6 + 6O2

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2
Q

What does ATP consist of?

A

ATP (Adenosine TriPhosphate) consists of:
- A nitrogenous organic base
- A ribose sugar
- Three phosphate groups

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3
Q

Give two uses of ATP.

A
  • Provides energy for active transport/ muscle contraction/ protein synthesis.
  • Phosphorylation: BINDS to enzymes/substrates and either:
    > Lowers activation energy
    > Alters tertiary structure
    > Makes molecules MORE reactive
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4
Q

How is ATP formed?

A
  • Formed from ADP (Adenosine DiPhosphate) and inorganic phosphate.
  • It requires energy to add a phosphate group (PO4 3-) to ADP to form ATP, creating a high energy bond.
  • This involves a condensation reaction.
  • ATP synthase
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5
Q

How is ATP broken down?

A
  • Easily broken down back to ADP and inorganic phosphate.
  • When this happens, the bond between 2nd and 3rd phosphate breaks, releasing small manageable amounts of useable energy.
  • ATP breaks down to ADP and Pi in a hydrolysis reaction, which requires 1 molecule of water.
  • ATP hydrolase
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6
Q

Give 2 reasons why ATP is so useful.

A
  • Releases energy in small, manageable amounts.
  • Broken down in one-step/ single bond broken.
  • Immediate energy compound/ makes energy available rapidly.
  • Phosphorylates/ adds phosphate.
  • Makes (phosphorylated substances) more reactive/ lowers activation energy.
  • Reformed/ made again.
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7
Q

What is the co-enzyme NADP?

A
  • NADP= Nicotinamide Adenine Dinucleotide Phosphate
  • NADP is an essential molecule which acts as a HYDROGEN ACCEPTOR, becoming reduced to form NADPH.
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8
Q

What is the co-enzyme NADPH?

A
  • NADPH is a reducing agent.
  • This means it can donate hydrogen to other molecules during REDOX reactions.
  • As it loses this hydrogen, NADPH is oxidised to NADP and the molecule that accepts hydrogen/e- is said to be reduced.
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9
Q

Where does the LDR occur?

A

Granum

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10
Q

What two products are formed from the LDR which are used for the LIR?

A

NADPH and ATP

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11
Q

Where does the LIR/ Calvin Cycle occur?

A

Stroma

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12
Q

What is the light-dependent reaction?

A

• Chlorophyll absorbs light energy & Excites electrons
• electrons removed (Oxidation of chlorophyll) via photoionisation;
• Electrons move along carriers/electron transport chain releasing energy (Series of REDOX reactions)
• Energy released (by electrons) used to form proton gradient;
• H+ ions move through ATP synthase;
• providing energy to join ADP and Pi to form ATP;
• Photolysis of water produces 2 protons, 2 electrons and ½ oxygen;
• NADP reduced by electrons / electrons and protons / hydrogen;

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13
Q

What are the phases of LIR?

A
  • Carbon Fixation
  • Reduction
  • Regeneration
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14
Q

What is the light-independent reaction?

A
  • Carbon dioxide combines with RuBP (ribulose diphosphate) using the enzyme rubisco.
  • Produces two GP molecules (gylcerate 3-phosphate)
  • 2x GP reduced to 2x triose phosphate
  • Using reduced NADP
  • Using energy from ATP
  • Triose phosphate converted to glucose/amino acid etc.
  • Triose phosphate regenerated into RuBP
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15
Q

How is the chloroplast adapted to maximise the rate of photosynthesis in the stroma?

A
  • Large number of thylakoids/grana
  • Short diffusion distance
  • Aqueous
  • Protein,
  • High abundance of rubisco
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16
Q

What are the limiting factors affecting the rate of photosynthesis and their effects?

A
  • Temperature= smallest effect
  • Carbon dioxide concentration = 2nd biggest effect
  • Light intensity and wavelength= biggest effect
17
Q

What does it mean when a graph plateaus in terms of the limiting factor?

A

When the graph plateaus, the limiting factor is no longer the variable on the x-axis, e.g., light intensity, it is another factor.

18
Q

ATP is produced in the light dependant reaction, suggest why this is not their (plants) only source of ATP.

A
  • Plants don’t photosynthesis in the dark;
  • Not all the parts of the plants photosynthesise;
  • Plants require more ATP than is produced in the light dependant reaction;
  • ATP used in Active Transport (accept other named processes)
19
Q

Describe the effect of introducing a herbicide/inhibitor on the electron transport chain (4)

A
  • Reduced transfer of protons across thylakoid membrane
    OR
  • Reduced chemiosmotic gradient/proton gradient across thylakoid membrane;
  • (So) less ATP produced;
  • (So) less reduced NADP produced;
  • (So) light-independent reaction slows/stops
    OR
  • Less reduction of GP to triose phosphate;
20
Q

Describe what happens during photoionisation in the light dependent reaction.

A
  • Chlorophyll absorbs light
    OR
    Light excites/moves electrons in chlorophyll;
  • Electron/s are lost
    OR
    (Chlorophyll) becomes positively charged;
    Accept electrons go to electron transport/carrier chain for ‘electrons lost’.
21
Q

Explain why scientists measure the rate of production of oxygen in this investigation.

A

Oxygen is produced in LDR.
The faster oxygen is produced, the faster the LDR.

22
Q

Explain why plants with more chlorophyll grow faster than plants with less chlorophyll.

A

Faster production of ATP and NADPH.
So faster LIR.
So produce more sugars used in respiration.
So have more energy for growth.
Faster synthesis of organic material.

23
Q

Suggest and explain the advantage to plants of having different colour pigments in leaves.

A
  • Absorb different/more wavelengths of light for photosynthesis;
24
Q

Explain the relationship between stomatal opening and photosynthesis.

A

Stomata allow uptake of CO2.
CO2 required for photosynthesis.

25
Q

The concentrations of CO2 in the air at different heights above ground in a forest change over a 24hr period.

Use your knowledge of photosynthesis to describe these changes and explain why they occur.

A

High concentration of CO2 linked with darkness.
No photosynthesis in dark. Light required for photosynthesis.
In dark, plants respire.
In light, plants use more CO2 than they produce. Rate of photosynthesis higher than rate of aerobic respiration.
Decrease in CO2 concentration with height.
At ground level, fewer leaves, less photosynthesising.

Biology Noor (30 decks)

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