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Biology > Photosynthesis > Flashcards

Photosynthesis Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is photolysis?

A

Splitting of a molecule using light energy.

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2
Q

What is photophosphorylation?

A

Process of adding a phosphate to a molecule using light energy.

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3
Q

What is photoionisation?

A

Process of turning an atom/molecule into an ion using light energy.

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4
Q

What is an electrochemical gradient?

A

Conc gradient of ions.

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5
Q

What is a photoautotroph?

A

Organisms that use light energy to synthesise organic molecules during photosynthesis.

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6
Q

What is a heterotroph?

A

Organisms that obtain organic materials from plants to supply energy and nutrients it needs.

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7
Q

What is a producer?

A

Organism that synthesises biomass using energy from the environment in 1st trophic level of food chain.

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8
Q

What is a photoautotroph?

A

Organisms that use light energy to synthesise organic molecules in photosynthesis.

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9
Q

What is a heterotroph?

A

Orgasims that obtain organic material from plants for energy + nutrients.

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10
Q

What is the compensation point?

A

Point photosynthesis and respiration are at the same rate.
No net change of carbs.

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11
Q

What is the compensation period?

A

The time taken for the plant to reach the compensation point.

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12
Q

What is the structure and function of different parts of a chloroplast?

A

PS have pigments, electron carriers, ATP synthase
Thylakoid stacks = large SA - within, photosystems bound to proteins
Stroma surrounds grant = contains enzymes for LDR
Stroma has small ribosomes - assemble proteins for photosynthesis
Chloroplast has large SA + 3 compartments for conc and electrochemical gradients

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13
Q

What is a photosynthetic pigment?

A

Can absorb specific wavelengths of light and trap energy associated with the light.

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14
Q

What are accessory pigments?

A

Funnel energy associated with light wavelengths down to primary pigment reaction centre
made of chlorophyll a
in walls of funnel, made of chlorophyll b and carotenoids

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15
Q

What is chlorophyll a?

A

Most abundant, P680, P700, absorbs light around 440 nm

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16
Q

What is chlorophyll b?

A

Absorbs light around 400-500 nm, and 650 nm

17
Q

What are carotenoids?

A

Absorb light around 400-500 nm, yellow/orange

18
Q

What are xanophylls?

A

Absorb light 375-550 nm, yellow

19
Q

What happens in the light dependent stage?

A
  • photoionisation of chlorophyll a in PS2
  • electrons excited and released from PS2 to electron chain
  • energy from electrons - pump H+ stroma to thylakoid space
  • electrons move to PS1 and re photo ionised
  • electrons used to reduce NADP with NADP reductase
  • H+ flows down electrochemical gradient
  • via ATP synthase, to ATP by chemiososis
  • photolysis and electrons replace lost electrons from PS2
20
Q

What is the difference between cyclic and non-cyclic LDR?

A

Cyclic: PS1, water not needed, not make NADPH, used to make extra ATP to meet cell energy demands
Non-cyclic: PS1+2, needs photolysis of water, O2 evolved, NADPH synthesised, products used for LIR

21
Q

What are the key roles of water?

A

Source of protons
Donates electrons to chlorophyll to replace lost
Photolysis of water = O2 source for respiration
Needed for turgidity - stomata open for gas exchange

22
Q

What are the uses of triose phosphate?

A

2 TP to 1 hexose sugar so can make glucose
some glucose to sucrose/starch/cellulose
some TP to aa/fatty acids/glycerol
5 of 6 TP to regenerate RuBP

23
Q

What happens in the LIR?

A

Aka Calvin cycle.
1. carbon fixation - CO2 in air enters via stomata and diffuses to palisade cells then to stroma. conc gradient across chloroplast envelope.

24
Q

How is 1 hexose sugar made in the Calvin cycle?

A

6 turns of cycle for 6 spare carbons. 2 ATP for 1 glucose, other 10 TP fr RuBP regeneration.

25
Q

Why can the LIR only run in daylight?

A
  • pump H+ into space for LDR, increasing pH of stroma
  • optimum for enzymes
  • Mg2+ = cofactor for rubisco by bind to AS
  • electrons from PS1 needed to lower ferredoxin - activates other enzymes in Calvin
26
Q

What are the factors affecting photosynthesis?

A

Light intensity - of certain wavelength. Light compensation point = all CO2 from respiration used, little NADPH made so GP increases and Calvin not continue.

CO2 conc - if too low, RuBP not react in Calvin so increases.

Temperature - low temps have low KE so fewer enzyme collisions. Above 30’C, stomata close. If higher, denature. GP + TP decrease, RuBP increases then decreases as not regenerated.

27
Q

How can water availability limit photosynthesis?

A

Too much decreases ion uptake, if limited stomata close and rate decreases. too little, cells lose water and become plasmolysed.

Biology (32 decks)

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