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A2 Biology (5-8) > 5 - Photosynthesis, Respiration, Cycles > Flashcards

5 - Photosynthesis, Respiration, Cycles Flashcards

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1
Q

Where does the light dependant reaction in photosynthesis occur?

A

Thylakoids membrane in chloroplast
(Production of ATP)

  • chlorophyll absorbs light and electrons are lost
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2
Q

Where does the light independant reaction in photosynthesis occur?

A

In stroma in chloroplast

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3
Q

What is the role of light in photoionisation

A

chlorophyll absorbs light energy (photon) which excites electrons to a higher energy level, releasing them from chlorophyll

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4
Q

What are the 2 main stages involved in ATP production in the LDR

A
  1. Electron transfer chain
  2. Chemiosmosis
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5
Q

Describe production of ATP in the LDR part 1) What happens in the electron transfer chain

A

1 - electrons pass down the chain from PSII to PSI via redox reactions, losing energy at each step
2 - this energy is used to actively transport protons from stroma into thylakoid
3 - which creates a electrochemical gradient across the thylakoid membrane

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6
Q

Describe production of ATP in the LDR part 2)

A

4 - protons move by facilitated diffusion down the electrochemical gradient into the stroma via ATP synthase embedded in the thylakoid membrane
5- energy from this allows ADP + Pi—> ATP (chemiosmotic theory)

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7
Q

LDR part 3)
Describe production of NADPH

A

In PSI electrons are excited and transferred to NADP (with a proton from photolysis) to reduce NADP and form NADPH

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8
Q

LDR part 4) Describe photolysis

A
  • Splitting of water using light energy produces protons, electrons and oxygen (2H20 -> O2 + 4e + 4H+)
  • electrons replace those lost from chlorophyll
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9
Q

What are the products of the LDR

A
  • ATP
  • reduced NADP
  • oxygen
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10
Q

What are the 3 stages of the Calvin cycle (LIR)

A
  1. Carbon fixation
  2. Reduction
  3. Regeneration
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11
Q

Describe carbon fixation in the Calvin cycle (1)

A
  • CO2 reacts with RuBP, catalysed by the enzyme rubisco
  • this produces 2 molecules of (GP) (3C)
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12
Q

Describe reduction in the Calvin cycle (2)

A
  • GP is reduced to TP using products from the LDR:
  • energy from the hydrolysis of ATP and H+ from reduced NADP
  • some TP is converted into useful organic substances eg glucose
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13
Q

Describe regeneration in the Calvin cycle (3)

A
  • (5/6) TP is used to regenerate RuBP (using rest of ATP)
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14
Q

How does temperature effect the rate of photosynthesis

A

Increased temp up to the optimum - more E-S complexes (rubisco) and more kinetic energy

Above optimum - H bonds in tertiary structure break so active site changes shape. Rubisco denatures so fewer E-S complexes

  • it limits the light independent reaction as it is enzyme controlled (rubisco)
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15
Q

How would dramatically reduced light intensity effect the rate of photosynthesis

A

Levels of ATP and reduced NADP would fall because:

  • LDR is limited as less photoionisation of chlorophyll and photolysis

so LIR also slows because:
- GP cant be reduced to TP (requires ATP and reduced NADP)
- TP can’t regenerate RuBP (requires ATP)

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16
Q

How would dramatically reduced CO2 conc effect the rate of photosynthesis

A

LIR limited because:
- less CO2 to combine with RuBP to form GP
- less GP reduced to TP
- less TP and GP converted to organic substances eg to regenerate RuBP

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17
Q

How could you maximise light intensity for photosynthesis

A

Growing plants under artificial lighting

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18
Q

How could you increase temperature for photosynthesis

A

By heating a greenhouse

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19
Q

How could you increase CO2 conc for photosynthesis

A

Burning fuel eg paraffin burners

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20
Q

What is the effect on photosynthesis of limiting factors being only minimal

A

Rate of photosynthesis will increase because:
- faster production of glucose so faster respiration
- more ATP to provide energy for growth eg cell division, protein synthesis
- higher yield so more profit

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21
Q

Which chemicals are needed for the LDR

A

NADP
ADP
Pi
Water

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22
Q

What’s the advantage of having different coloured pigments in leaves

A

Absorb more wavelength’s of light for photosynthesis

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23
Q

Where is rubisco found in a cell

A

Stroma

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24
Q

What are the two molecules produced in the LDR which are needed for the LIR/Calvin cycle

A

ATP
NADPH

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25
Q

Where does glycolysis occur

A
  • cytoplasm
  • anaerobic process
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26
Q

Describe glycolysis

A

Occurs in cytoplasm
1) phosphorylation of glucose to GP using the inorganic phosphates from 2 ATP

2) hydrolysed to 2 x triose phosphate (TP)

3) 2x TP is oxidised 2x pyruvate
. 2 NAD is reduced
. 4 ATP regenerated

4) net production of 2 ATP

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27
Q

What happens after glycolysis if no oxygen present (anaerobic respiration)

A

1) pyruvate reduced to lactate (animals) or ethanol (plants/yeast)

2) oxidising reduced NAD -> NAD regenerated

3) so glycolysis can continue which uses NAD

Some energy is still in lactate (incomplete breakdown of glucose)

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28
Q

Why is anaerobic respiration less efficient than aerobic

A
  • the ATP yield is lower
  • majority of ATP is formed in oxidative phosphorylation
29
Q

What happens after glycolysis if oxygen is present (aerobic respiration)

A

1) pyruvate is actively transported into mitochondrial matrix

2) the 4 stages of aerobic respiration occur

30
Q

What are the 4 stages of aerobic respiration

A
  1. Glycolysis
  2. Link reaction
  3. Krebs cycle
  4. Oxidative phosphorylation
31
Q

Describe aerobic respiration stage 2:
Link reaction

A

1 - occurs in mitochondrial matrix
2 - pyruvate is oxidised and decarboxylated to form acetate
. CO2 and NADH produced
3. Acetate combines with coenzyme A to form Acetyl Coenzyme A (CoA)
4. Per glucose molecule, 2x Acetyle CoA, 2x CO2, and 2x NADH produced

32
Q

Describe aerobic respiration stage 3:
Krebs cycle (1-3)

A

1 ) occurs in mitochondrial matrix
2) Acetyl CoA reacts with a 4-carbon molecule, producing a 6-carbon molecule that enters the Krebs cycle. (CoA is released)
3) - 4C molecule is regenerated through a series of redox reactions.

33
Q

Describe aerobic respiration stage 3:
Krebs cycle (4-5)

A

4) Decarboxylation and dehydrogenation occurs
. CO2 is removed
. Coenzymes NAD AND FAD reduced (important for oxidative phosphorylation) into NADH and FADH2

5) ATP produced by substrate level phosphorylation

34
Q

Describe aerobic respiration stage 4:
Oxidative phosphorylation (1-3)

A

1) occurs on the Cristae of mitochondria
2) reduced NAD/FAD oxidised to release H atoms split into protons and electrons (e-)
3) e- transferred down the electron transport chain by redox reactions

35
Q

Describe aerobic respiration stage 4:
Oxidative phosphorylation (4 - chemiosmotic theory)

A

4) energy released by electrons moving along the chain is used to make ATP from ADP +Pi (chemiosmotic theory)
- Energy used to actively transport protons from matrix to the inter membrane space
- Electrons At the end of the chain react with O2 and H+ to make water. Which is why Oxygen is the final electron acceptor
. Protons diffuse down via ATP synthase back into the matrix
. Releasing energy to produce ATP

36
Q

Why is oxygen needed for the production of ATP on the cristae of the mitochondria

A
  • O2 is the terminal electron acceptor for electrons passing along the ETC
  • the ETC releases energy for the formation of most ATP
  • if no O2 to accept them then e- cannot be passed along the e- transport chain
37
Q

Why is oxygen needed for the Krebs cycle and link reaction

A
  • NAD and FAD cannot be produced
38
Q

What are some other respiratory substrates

A

breakdown products of lipids and amino acids, which enter the Krebs cycle

39
Q

Why is high carbon has efficiency an advantage for an organism

A
  • low respiration
  • more growth
40
Q

Describe the role of saprobionts in the nitrogen cycle

A
  • they secrete enzymes to decompose proteins (extracellular digestion)
  • producing ammonium ions
41
Q

Give one way an increase in phosphate uptake in a plant could increase growth

A

Used to produce DNA

42
Q

Describe the role of mycorrhizae

A
  • symbiotic relationship between fungi and roots of plants
  • mutualistic relationship
  • increases SA and rate of absorption of water/nutrients
43
Q

Describe ammonification (3)

A
  • nitrogen containing compounds from animal waste are broken down by saprobionts into ammonia which gets converted into ammonium ions
44
Q

Describe nitrification (2)

A
  • ammonium ions in the soil -> nitrites -> nitrates
  • by nitrifying bacteria.
  • using O2
45
Q

Why do farmers aerate their soil

A
  • to increase O2 which allows number of nitrifying bacteria to increase and denitrifying bacteria to decrease
  • this maximises nitrogen availability
46
Q

Describe denitrification (4)

A
  • nitrates in the soil -> nitrogen gas
  • by denitrifying bacteria (anaerobically respire)
47
Q

Describe nitrogen fixation (1)

A
  • nitrogen gas in air is converted into ammonia and then ammonium ions
  • by nitrogen fixing bacteria
  • can be in foot nodules of plants eg legumes
48
Q

Why is the nitrogen cycle important

A
  • nitrogen gas is unreactive and not easily converted to other compounds
  • most plants can only take up nitrogen as nitrate
  • used by plants to make proteins/nucleic acids for growth
49
Q

Why are fertilisers needed

A
  • replaces nutrients lost from an ecosystem when crops are harvested or livestock is removed
  • improve effiency of energy transfer to increase productivity of the land
50
Q

What are the features of natural fertilisers

A
  • organic
  • eg manure, compost
  • cheaper/free
  • but exact nutrients cannot be controlled
51
Q

What are the features of artificial fertilisers

A
  • inorganic
  • contain pure chemical
  • inorganic substances more water soluble so larger quantities washed away which harms the environment
52
Q

What is eutrophication

A
  • rapid growth of algae in water
  • algae blocks light so it can’t reach plants below
  • plants die bc they can’t photosynthesise
  • aerobically respiring saprobionts decompose the dead plants, reducing o2 concentration in water
  • death of fish as no o2 left to respire
53
Q

What are stages 1-2 in the phosphorus cycle

A
  • phosphate ions in rocks released by erosion
  • then taken into plants and incorporated into their biomass
  • DNA, RNA, phospholipids
  • rate of absorption increased by mycorrhizae
54
Q

What are stages 3-4 in the phosphorus cycle

A
  • phosphate ions transferred through food chain
  • some lost from animals in waste products and plants and animals die
  • decomposed by saprobionts
  • release phosphate ions into the soil
55
Q

What are photoautotrophs

A

Use light energy to synthesis their own food

56
Q

What are chemoautotrophs

A

Use inorganic molecules to synthesis their food

57
Q

What are heterotrophs

A

Cannot synthesis their own energy but obtain it from autotrophs or other heterotrophs
- they act as consumers in food webs

58
Q

What are the two ways biomass can be measured

A
  • Mass of carbon
  • dry mass of tissue per given area
59
Q

What is gross primary production (GPP)

A

Total energy resulting from photosynthesis

60
Q

What is net primary production (NPP)

A

NPP = GPP - R (respiratory losses)

61
Q

How do you work out net production of consumers

A

N = I - (F+R)

I = energy store in digested food
F = energy lost in faeces and urine
R = respiratory losses

62
Q

What are some reasons for energy loss between trophic levels (sun to producer)

A
  • wrong wavelength of light
  • light strikes non-photosynthetic region
  • light reflected
  • lost as heat
63
Q

What are some reasons for energy loss between trophic levels (producer to consumer)

A
  • respiratory loss (energy used for metabolism
  • lost as heat
  • not all parts eaten eg bones
  • some food not digested eg faeces
64
Q

How could you increase energy transfer via livestock

A

Reduce respiratory losses by:
- restrict movement
- keep warm
- slaughter animal while still young

65
Q

How could you increase energy transfer via crops

A

Simplify food webs:
- herbicides
- fungicides
- pesticides

66
Q

Why is DCPIP used in the photosynthesis experiment

A

As a control to show that light does not effect it

67
Q

What are the names of the two types nitrogen fixing bacteria

A
  • free living: Azotobacter
  • Mutualistic: Rhizobium
68
Q

What are the names of the two types nitrifying bacteria

A

Converts ammonium ions to nitrite: Nitrosomonas
Converts nitrite to nitrate: Nitrobacter

69
Q

What adaption of mitochondria allows them to produce a large amount of ATP

A
  • their cristae have a large surface area for oxidative phosphorylation

A2 Biology (5-8) (5 decks)

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