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AQA A Level Biology > Respiration + Photosynthesis > Flashcards

Respiration + Photosynthesis Flashcards

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1
Q

why is respiration needed?

A
  • growth - building larger molecules from smaller ones
    eg. make new organelles or biomass
  • movement - muscle contraction
  • keeping warm - birds + mammals use a lot of e for keeping warm and lose it to environment
  • active transport - plants use it to absorb nitrates from soil
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2
Q

equation for respiration

A

C6,H12,O6 + 6O2 —> 6Co2 + 6H2O + ATP

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3
Q

4 stages in aerobic respiration + where they take place

A
  1. glycolysis - cytoplasm
  2. link reaction - matrix in mitochondria
  3. krebs cycle - matrix in mitochondria
  4. oxidative phosphorylation - cristae in mitochondria
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4
Q

what happens if mitochondria is isolated

A

respiration cant occur as 1st step is glycolysis and occurs in cytoplasm

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5
Q

what is a coenzyme + give examples

A

molecule aiding functioning of an enzyme by transferring a chemical group from one molecule to another
NAD + FAD transfer H
coenzyme A transfers acetate
NADP transfer H

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6
Q

explain glycolysis

A

anaerobic process
makes pyruvate from glucose
1. phosphorylation of glucose to glucose phosphate, then again to hexose biphosphate
- Pi comes from ATP molecules (2)
- bond unstable so splits into 2 triose phosphate
2. oxidation
- NAD molecules come and oxidise triose phosphates by taking a H, becomes reduced itself - NADH.
- forms 2 pyruvates

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7
Q

products of glycolysis + where they go

A
  • 4x ATP , but 2 used in phosphorylation so net gain of 2
  • 2x NADH - go to stage 4
  • 2x pyruvate, go to matrix by active transport for link
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8
Q

explain link reaction

A

converts pyruvate to acetyl coenzyme A

  • pyruvate is decarboxylated
  • pyruvate is oxidised to acetate by NAD
  • NAD reduced to NADH
  • acetate + Coenzyme A –> acetyl CoA
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9
Q

products of link reaction + where they go

A

2x acetyl CoA
2x CO2 as waste
2x NADH to stage 4

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10
Q

explain krebs cycle

A

produces reduced CoA + ATP
series of redox reactions
- acetyl CoA combines with oxaloacetate to make citrate
- CoA goes back to stage 2
- decarboxylation + dehydrogenation occurs to make 5C. H is used to make NADH
- decarboxylation + dehydrogenation occur again to make 4C, release 1x FADH and 2x NADH
-ATP is produced by substrate - level phosphorylation.

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11
Q

products of 1 krebs cycle + where they go

A
  • 1x CoA, reused in link
  • oxloacetate, regenerated for next cycle
  • 2x CO2, waste
  • 1x ATP for energy
  • 3x NADH, go to stage 4
  • 1x FADH, go to stage 4
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12
Q

explain oxidative phosphorylation

A

1) H released from NADH + FADH and split into H+ and e-
2) e-s travel down electron transport chain, losing energy at each level
3) energy lost used to pump H+ to intermembrane space(ims) from mmatrix
4) electrochemical gradient is formed cuz ↑er conc of H+ in ims than mmatrix
5) H+ go ↓ ecg across inner mitochondrial membrane + back in membrane via ATP synthase (in IMmembrane). this movement drives synthesis of ATP from ADP+Pi (chemiosmosis)
6) at end of transport chain in mmatrix,
H+ + e- + O2 (from blood) –> H2O
O2 =final electron acceptor

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13
Q

work out total ATP produced in aerobic respiration

A 
glycolysis 
- 2xATP , 2xNADH
- 2 + (2.5 x 2) = 7
link reaction
- 2xNADH
- 2 x 2.5 = 5
krebs cycle
- 2xATP , 6xNADH , 2xFADH
- 2 + (6x2.5) + (2x1.5) = 20

7 + 5 + 20 = 32 total ATP

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14
Q

anaerobic respiration

alcoholic fermentation + lactate fermentation

A

alcoholic fermentation - plants + yeast

1) glycolysis
2) pyruvate –> ethanal + CO2
3) ethanal –> ethanol + NAD (from NADH)

lactate fermentation - animal cells + some bacteria

1) glycolysis
2) pyruvate –> lactate + NAD (from NADH)

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15
Q

how many ATP are made from 1 FADH?

A

1.5

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16
Q

what is a electrochemical gradient

A

conc gradient of ions

17
Q

what is a electrochemical gradient

A

conc gradient of ions

18
Q

name 2 types of anaerobic respiration

A

lactate fermentation

alcoholic fermentation

19
Q

how does glycolysis continue in lack of O2?

A

regeneration of oxidised NAD, so at least a small amount of ATP can be produced to keep biological processes continuing

20
Q

equation for photosynthesis

A

6CO2 + 6H2O + energy —> C6,H12,O6 + 6O2

21
Q

what are metabolic pathways

A

processes occurring in series of small enzyme controlled reactions
eg photosynthesis + respiration

22
Q

properties of ATP making it good energy source

6 things

A
  • stores or releases small manageable amounts of E at a time so no E wasted as heat
  • easily broken down - immediate E release
  • quickly remade
  • small + soluble so easily transported around cell
  • can phosphorylate other molecules
  • cant pass out of cell, so always there as E supply
23
Q

ATPs role

A
  • carries E around cell released from glucose since it cant get it directly from it
  • condensation reaction of ADP + Pi (+ATP synthase) using E from E releasing reaction - breakdown of glucose
  • E stored as chemical E in P-P bond
  • diffuses to area of cell needing E
  • broken by hydrolysis using H2O and ATP hydrolase to release E from bond
24
Q

compensation point

A
  • plants carry out photosynthesis and respiration
  • Cp is point where ROPhotosynthesis = RORespiration
  • Cp for light intensity is the point where ROP = ROR at certain light intensity
25
Q

where in cell does photosynthesis take place?

- describe structure of organelle

A

chloroplasts - small flattened organelles surrounded by double membrane

  • thylakoids = fluid filled sacs , contain pps
  • grana = structures of stacked thylakoids
  • lamellae = bits of thylakoid linking grana
  • stroma = gel like substance in inner membrane containing enzymes, sugars + organic acids
26
Q

how are carbohydrates produced by photosynthesis stored

A

stored as starch grains in stroma

27
Q

photosynthetic pigments (pp) + photosystems (ps)

A
  • pp in thylakoid membranes, eg carotene and chlorophyll a + b
  • coloured substances absorbing light E for photosynthesis
  • pp attached to proteins
  • pp + protein = ps
28
Q

wavelength photosystem 1 absorbs light best at

A

700nm

- primary pigment is chlorophyll a

29
Q

wavelength photosystem 2 absorbs light best at

A

680nm

- primary pigment is chlorophyll b

30
Q

light dependent reaction (LDR)

A
  1. Chlorophyll in ps absorbs light energy
  2. Excites e-s which eventually get removed from chlorophyll molecule due to high E (photoionisation)
  3. e-s move along carriers in etc releasing E
  4. E used to join ADP and Pi to form ATP
  5. Photolysis of water produces protons, electrons and oxygen
  6. NADP reduced and carries H to LIR
31
Q

what E from photoionisation is used for

A
  • photophosphorylation (phosphorylation using molecule of light)
  • making reduced NADP from NADP
  • photolysis of water
32
Q

non-cyclic photophosphorylation

A
  1. light E absorbed by psII, exciting e-s in chlorophyll which are removed from chlorophyll + move down etc to psI
  2. photoloysis of water (producing 2e- , 2H+ , 1/2O2) to replace e- lost from psII
  3. excited e-s lose E moving down etc, which is used to transport H+ into thylakoid from stroma so proton gradient along thylakoid membrane
  4. H+ move along gradient, driving synthesis of ATP from ADP + Pi + ATP synthase which is embedded in membrane
  5. light E absorbed by psI, exciting e-s to even higher E level + e- and H+ (from stroma) reduce NADP
  6. this process produces ATP, NADPH and O2
33
Q

cyclic photophosphorylation

A
  • no O2 or NADPH produced
  • only produces small amount ATP
  • e- from chlorophyll aren’t passed to NADP but back to psI via electron carriers
  • electrons recycled + repeatedly flow through psI
34
Q

light independent reaction

A
  • in stroma
  • doesn’t use light E directly, but uses products of LDR
  • NADPH + ATP supply E and H to make glucose from CO2
    1. CO2 enters leaf via stomata and diffuses to stroma
    2. CO2 + ribulose biphosphate (rubp) –rubisco catalyst–> unstable 6c compound –> 2 x glycerate phosphate (gp)
    3. hydrolysis of ATP from LDR provides E to reduce gp –> triose phosphate (tp)
    using H+ from NADPH + oxidising to NADP
    4. 5/6 tp used to regenerate rubp in cycle, using up rest of ATP from LDR
    1/6 is converted to useful organic compounds like hexose sugars
35
Q

hexose sugars

A

= 6c sugars eg glucose

  • made from 2x tp
  • can be used to make larger carbohydrates
  • calvin cycle turns x6 to make 1 hexose since 3 turns makes 6 tp - only 1 will go towards being a hexose
36
Q

what can gp and tp be used to make

A
  • carbohydrates - made from joining 6cs together
    eg cellulose, starch and sucrose
  • lipids - glycerol is made from tp + Fas (made from gp)
  • amino acids - some made from gp

AQA A Level Biology (4 decks)

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