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A-Level Biology > 5A - Photosynthesis and Respiration > Flashcards

5A - Photosynthesis and Respiration Flashcards

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1
Q

What is the equation of photosynthesis?

A
  • Carbon dioxide + water + energy -> glucose + oxygen
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2
Q

What is the equation for respiration?

A
  • glucose + oxygen -> carbon dioxide + water + energy
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3
Q

What specific properties does ATP have that makes it a good energy source?

A
  • stores and releases only small amounts of energy, no energy is wasted
  • small, soluble molecule - easily transported
  • easily broken down
  • can be quickly re-made
  • can make other molecules more reactive by transferring a phosphate group
  • can’t pass out of a cell, cell always has immediate source of energy
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4
Q

What is the coenzyme used in photosynthesis?

A
  • NADP

- transfers hydrogen from one molecule to another (reduction or oxidation)

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5
Q

What are coenzymes used in respiration?

A
  • NAD, FAD and Coenzyme A
  • NAD and FAD either reduce or oxidise a molecule
  • Coenzyme A transfers acetate between molecules
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6
Q

Where does photosynthesis take place?

A
  • chloroplasts
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7
Q

What are thylakoids?

A
  • fluid-filled sacs stacked up into grana
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8
Q

What are grana linked together by?

A
  • lamellae
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9
Q

What are photosynthetic pigments and what are the 3 types?

A
  • coloured substances that absorb light energy

- chlorophyll a, chlorophyll b and carotene

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10
Q

What wavelength does Photosystem I absorb light best?

A
  • 700nm
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11
Q

What wavelength does Photosystem II absorb light best?

A
  • 680nm
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12
Q

What is the stroma?

A
  • gel-like substance which contains enzymes, sugars and organic acids
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13
Q

What is the first stage of the light-dependent reaction?

A
  • light energy is absorbed by chlorophyll in photosystems

- light energy excites electrons in chlorophyll, leading to eventual release (photoionisation)

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14
Q

What is the second stage of the light-dependent reaction?

A
  • some of the energy from released electrons is used to add phosphate group to ADP to form ATP, and some is used to form reduced NADP
  • H2O is oxidised to O2
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15
Q

The energy resulting from photoionisation in chlorophyll is used for what three things?

A
  • photophosphorylation (ADP + Pi = ATP)
  • making reduced NADP from NADP
  • photolysis (splitting water into protons, electrons and oxygen)
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16
Q

What happens during the first stage of non-cyclic phosphorylation?

A
  • light energy is absorbed by PSII
  • light energy excites electrons in chlorophyll
  • electrons move to higher energy level
  • electrons are released from chlorophyll and move down electron transport chain to PSI
17
Q

What happens during the second stage of non-cyclic phosphorylation?

A
  • light energy splits water into protons, electrons and oxygen (photolysis)
  • to replace the released electrons
18
Q

What happens during the third stage of non-cyclic phosphorylation?

A
  • excited electrons lose energy as they move down the electron transport chain
  • energy is used to transport protons into thylakoid, so thylakoid has higher concentration of protons than the stroma
  • proton gradient is formed across thylakoid membrane
  • protons move down gradient into stroma via ATP synthase. Energy from this movement makes ATP.
19
Q

What is the fourth stage of non-cyclic phosphorylation?

A
  • light energy is absorbed by PSI, exciting electrons again to an even higher energy level
  • electrons are transferred to NADP along with a proton to form reduced NADP
20
Q

What is ‘cyclic phosphorylation’?

A
  • electrons are passed back to PSI via electron carriers rather than being passed to NADP
  • only produces small amounts of ATP
21
Q

What is the first stage of the light-independent reaction?

A
  • CO2 enters leaf through stomata and diffuses into stroma
  • combines w/ ribulose biphosphate (RuBP), reaction is catalysed by rubisco
  • gives unstable 6-carbon compound, which quickly breaks down into 2 glycerate 3-phosphate (GP)
22
Q

What is the second stage of the light-independent reaction?

A
  • hydrolysis of ATP from light-dependent reaction provides energy to turn GP into triose phosphate (TP)
  • reaction also requires H ions, which come from reduced NADP. Reduced NADP is recycled to NADP.
  • some TP is then converted into useful organic substances and some regenerates RuBP
23
Q

What is the third stage of the light-independent reaction?

A
  • 5/6 molecules of TP produced in the cycle is used to regenerate RuBP
  • regenerating RuBP uses the rest of ATP produced by light-dependent reaction
24
Q

What are the three limiting factors of photosynthesis?

A
  • light intensity
  • CO2 concentration
  • temperature
25
Q

What is the first stage of glycolysis?

A
  • glucose is phosphorylated using a phosphate from ATP
  • creates 1 glucose phosphate and 1 ADP
  • ATP adds another phosphate, forming hexose bisphosphate
  • hexose bisphosphate is then split into 2 triose phosphate
26
Q

What is the second stage of glycolysis?

A
  • triose phosphate is oxidised, forming two pyruvates
  • NAD collects hydrogen ions, forming 2 reduced NAD
  • 4 ATP are produced, but 2 were used up in the first stage, so net gain is 2 ATP
27
Q

What happens to the pyruvate in anaerobic respiration?

A
  • converted to ethanol or lactate

- regenerates oxidised NAD, means glycolysis can continue even when there isn’t much O2 around

28
Q

What happens first in the link reaction?

A
  • pyruvate is decarboxylated (one carbon atom is removed in the form of CO2
29
Q

What happens second in the link reaction?

A
  • pyruvate is oxidised to form acetate

- NAD is reduced to form reduced NAD

30
Q

What happens third in link reaction?

A
  • acetate is combined with coenzyme A to form acetyl coenzyme A
31
Q

Is ATP produced in the link reaction?

A
  • No
32
Q

What happens in the first stage of the Krebs Cycle?

A
  • acetyl CoA from link reaction combines with 4-carbon molecule to form 6-carbon molecule
  • coenzyme A goes back to link reaction to be used again
33
Q

What happens in the second stage of the Krebs Cycle?

A
  • 6C citrate molecule converted to 5C molecule
  • decarboxylation occurs, CO2 removed
  • dehydrogenation also occurs, H removed
  • hydrogen used to produce reduced NAD from NAD.
34
Q

What happens in the third stage of the Krebs Cycle?

A
  • 5C molecule converted to 4C molecule
  • decarboxylation and dehydrogenation occur, producing 1 molecule of reduced FAD and 2 reduced NAD
  • ATP is produced by direct transfer of phosphate group from an intermediate compound to ADP
  • citrate is now converted into oxaloacetate
35
Q

What happens first in oxidative phosphorylation?

A
  • hydrogen atoms are released from reduced NAD and reduced FAD as they’re oxidised to NAD and FAD
  • H atoms split into protons and electrons
36
Q

What happens second in oxidative phosphorylation?

A
  • electrons move down transport chain, losing energy at each carrier
  • energy is used to pump protons from mitochondrial matrix into the intermembrane space
  • concentration of protons is now higher in intermembrane space than the matrix - forms electrohemical gradient
37
Q

What happens third in oxidative phosphorylation?

A
  • protons move down electrochemical gradient via ATP synthase
  • ATP is synthesised from ADP and P
38
Q

What happens fourth in oxidative phosphorylation?

A
  • in the mitochondrial matrix, protons, electrons and O2 combine to form water
  • oxygen is the final electron acceptor
39
Q

What is the process of ATP production being driven by the movement of H+ ions across a membrane called?

A
  • chemiosmosis

A-Level Biology (19 decks)

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