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A-Level Bio > Topic 5 > Flashcards

Topic 5 Flashcards

1
Q

Chloroplast structure

A

Outer membrane
Intermembrane space
Inner membrane
Stroma (fluid with enzymes)
Granum (stacks of thylakoid membranes)
Lamellae (bridge between granum)

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2
Q

What are Thylakoid membranes?

A

Folded membranes which contain chlorophyll and electron carrier proteins embedded

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3
Q

What is the stroma?

A

Fluid centre which contains enzymes involved in the Light Independent Reaction

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4
Q

What is the function of the inner and outer membranes of chlorophyll

A

Controlling what can enter or exit the organelle

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5
Q

Where do the LDR and LIR occur?

A

LDR in thylakoid membranes (grana)
LIR in the stroma

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6
Q

What happens overall in the light dependent reaction

A

Light energy and water are used to create ATP and NADPH

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7
Q

4 Stages of the Light Dependent Reaction

A
  1. Photolysis
  2. Photoionisation of chlorophyll
  3. Chemiosmosis
  4. Production of ATP and NADPH
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8
Q

What happens in photolysis?

A

Light energy absorbed by chlorophyll and splits water into oxygen, H+ and e-

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9
Q

Photolysis equation

A

H2O -> 1/2O2 + 2e- + 2H+

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10
Q

What are the uses for each product of photolysis?

A

H+ picked up by NADP to form NADPH and is used in the Light Independent Reaction
e- are passed along the electron transport chain
Oxygen is used for respiration as the terminal electron acceptor or diffuses out of the leaf through the stomata

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11
Q

What happens during the photoionisation of chlorophyll?

A

Light energy is absorbed by the chlorophyll causes electrons to become excited and increase their energy levels so they leave the chlorophyll

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12
Q

What is the purpose of photoionising chlorophyll

A

The energy from released electrons is used to make ATP and NADPH in chemiosmosis

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13
Q

Chemiosmosis steps

A

Electrons that left the chlorophyll move along a series of proteins in the thylakoid membrane
They release energy at the proteins allowing for the proteins to pump proteins across chloroplast membranes
This causes the creation of an electrochemical gradient, allowing protons to move by facillitated diffusion down the gradient through ATP synthase out into the stroma, producing ATP
The protons combine with the coenzyme NADP to become NADPH

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14
Q

Where does the Calvin cycle occur?

A

In the stroma, which has the enzyme RuBisCo

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15
Q

Why is the Light Independent Reaction temperature sensitive

A

It has the enzyme RuBisCo, which could denature

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16
Q

What happens in the Light Independent Reaction (Calvin Cycle)

A

CO2 + NADPH + ATP -> Hexose sugar

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17
Q

Why do we need the NADPH and ATP in the Light Independent Reaction

A

ATP is hydrolysed to provide the energy reducing GP molecules to triose phosphates
NADPH donates the hydrogen to reduce the GP molecules in the cycle

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18
Q

Outline the steps of the Calvin cycle

A

CO2 reacts with RuBP (5C) to form 2 x GP molecules (3C each) CATALYSED by the RuBisCo enzyme
GP is reduced to triose phosphate using energy ATP and by accepting a proton from NADPH
1 carbon from the 2 Triose phosphates can then form organic substances while the remaining molecules are used to regenerate RuBP (5C) with energy from ATP

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19
Q

What can be done with the glucose from the Calvin cycle?

A

It can make disaccharides and polysaccharides and can be converted into glycerol and combine with fatty acids to form lipids

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20
Q

How many times must the Calvin cycle occur for glucose production

A

6 times

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21
Q

Limiting factors of photosynthesis

A

Temperature
CO2
Light intensity

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22
Q

How do greenhouses remove limiting factors of photosynthesis

A

Artificial lighting for max light intensity
Heating a greenhouse to increase temp
Burning fuel (eg paraffin burners) to release more CO2

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23
Q

4 Stages of aerobic respiration and locations

A

Glycolysis (cytoplasm)
Link reaction (mitochondrial matrix)
Krebs cycle (mitochondrial matrix)
Oxidative phosphorylation (mitochondrial inner membrane cristae)

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24
Q

Purpose of respiration

A

Produce ATP

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25
Q

Does glycolysis need oxygen?

A

No, it’s anaerobic

26
Q

Glycolysis steps

A
  1. Phosphorylating glucose to glucose phosphate using ATP
  2. The production of 2x triose phosphate
  3. Oxidation (loss of a H+) of both triose phosphates to produce 2 pyruvates ending with a net gain of ATP, NADH and 2 pyruvate molecules
27
Q

How do the pyruvate and NADH from glycolysis get to the mitochondrial matrix for the Link reaction?

A

Pyruvate and NADH are actively transported from the cytoplasm into the mitochondrial matrix

28
Q

Link reaction steps

A

Pyruvate(3C) in glycolysis is oxidised to acetate(2C) and CO2 (which is lost)
NAD picks up the hydrogen from that oxidation to become NADH
Acetate combines with coenzyme A to produce acetylcoenzyme A
This whole reaction occurs twice for every glucose molecule
Releasing 2 AcetylcoenzymeA, 2 CO2s out and 2 NADH

29
Q

Krebs Cycle steps

A

AcetylCoA(2C) reacts with a 4 carbon molecule releasing coenzyme A for reuse in the Link reaction and producing a 6 carbon molecule that enters the Krebs cycle
In a series of Redox reactions the Krebs cycle generates reduced coenzymes and ATP by substrate level phosphorylation and CO2 is lost

30
Q

Products per Krebs cycle

A

3 NADH
1 FADH
1 ATP
2 CO2

31
Q

Products per glucose molecule in the Krebs cycle

A

6 NADH
2 FADH
2 ATP
4 CO2

32
Q

Steps for oxidative phosphorylation

A

Reduced Coenzymes release protons and electrons
Electrons move along electron transfer chain releasing energy
Energy is used to actively transport protons form the mitochondrial matrix into the intermembrane space
An electrochemical gradient is made and the protons move by facillitated diffusion through ATP synthase into the mitochondrial matrix
ATP synthase catalyses the reaction to form ATP from ADP and Pi

33
Q

What happens to the 2H+ and 1/2O and 2e- after oxidative phosphorylation (and Chemiosmosis too)?

A

They form water in the mitochondrial matrix after the H+ passes through ATP synthase

34
Q

Anaerobic respiration occurs where?

A

Cytoplasm, after the link reaction occurs there too

35
Q

What happens in anaerobic respiration?

A

The 2x pyruvate produced in glycolysis is reduced to form ethanol and co2 in plants and microbes or lactate in animals by gaining the hydrogen from NADH
This oxidises NAD so it can be reused in glycolysis and produce more ATP

36
Q

What is the producer in any ecosystem’s food web?

A

Plants as they produce their own carbohydrates using CO2 and H2O

37
Q

Why is energy lost between tropic levels?

A

Respiration and excretion, leaving the remaining energy to form biomass

38
Q

What can biomass be measured in?

A

Mass of carbon or dry mass of tissue per given area

39
Q

How can you measure the chemical energy store of biomass?

A

Using calorimetry

40
Q

What is GPP

A

Gross Primary Production is the chemical energy store in plant biomass, in a given area or volume
(Total energy resulting from photosynthesis)

41
Q

What is NPP

A

the chemical energy store in plant biomass after respiratory losses to the environment have been taken into account
NPP = GPP - R

42
Q

What is the NPP for?

A

Plant growth and reproduction
Also available to other trophic levels

43
Q

Net production of consumers formula

A

N = I - (F+R)

I = ingested chemical energy from food
F = chemical energy lost to environment by faeces and urine
R = respiratory losses

44
Q

Rate of productivity units and reasons for each part

A

kJ ha-1 year-1
kJ is the unit for energy
Per unit area to standardise results to enable comparison between environments as different sizes are accounted for
Per year to take seasonal impacts on light, rain and heat into account, providing annual average for fair comparisons between environments

45
Q

Nitrogen cycle importance

A

Air is 78% Nitrogen
Plants and animals cannot obtain this through gas exchange due to the triple bond in N2
We need it for proteins, ATP and nucleic acids

46
Q

4 key stages of the nitrogen cycle

A
  1. Nitrogen fixation
  2. Ammonification
  3. Nitrification
  4. Denitrification
47
Q

Nitrogen fixation

A

Nitrogen fixing bacteria convert nitrogen gas into ammonia forming ammonium ions
Eg Rhizobium, in root nodules of leguminous plants
These bacteria are mutualistic, meaning they provide the plant with nitrogen compounds and the plant provides the bacteria with carbohydrates

48
Q

Ammonification

A

Saprobionts convert nitrogenous organic material (dead plants, animals, waste) into ammonia to form ammonium ions and release them back into the soil

49
Q

Nitrification

A

Ammonium ions can’t be used by plants
Nitrifying bacteria convert ammonium ions into nitrites then nitrates
Plants can use nitrates

50
Q

Denitrification

A

When nitrate ions are converted back into nitrogen gas by denitrifying bacteria in a reduction reaction (unlike every other one as they are oxidation reactions)
This requires anaerobic conditions like waterlogged soil.

51
Q

Why is the phosphorous cycle necessary?

A

used in
DNA
RNA
ATP
Phospholipid bilayer

52
Q

Difference between phosphorous and nitrogen cycles

A

It is not naturally found as a gas unlike nitrogen- it’s found as an ion in mineral form

53
Q

What are mycorrhizae

A

Fungal associations between plant roots and beneficial fungi

54
Q

Why are mycorrhizae beneficial for plant growth

A
  1. The fungi increase the surface area for water and mineral absorption
    The micorrhizae acts like a sponge and holds water and minerals around the roots
  2. This makes the plant more drought resistant and able to take up more inorganic ions
  3. They help plants improve the uptake of relatively scarce ions like phosphate ions in a mutualistic relationship
55
Q

Phosphorous cycle

A

Draw it out ..!! Use the studymind page if u forgot …

56
Q

Purpose of fertilisers

A

Added to soil to replace the nitrate and phosphate ions lost when plants are harvested and removed from nutrient cycles

57
Q

Fertiliser types?

A

Natural (manure)
Artificial (inorganic soluble chemicals with exact proportions of required chemicals)

58
Q

Natural fertiliser advantage and disadvantage

A

Cheaper or free if the farmer owns animals

Exact minerals and proportions of chemicals cannot be controlled

59
Q

Artificial fertilisers advantage and disadvantage

A

They are chemicals created to contain exact proportions of minerals and they are more water soluble so plants absorb nitrates and phosphates better

However the increased solubility means that larger quantities are washed away with rainfall which causes leaching and can lead to eutrophication in rivers and ponds

60
Q

Leaching definition?

A

When water soluble compounds are washed away often into rivers or ponds

61
Q

Eutrophication steps

A

Nitrates leached from fertilised fields stimulate algae growth in a pond
Excessive growth creates a blanket on the water surface blocking out light
As a result, plants below cannot photosynthesise and die
Bacteria within the water feed and respire on the dead plant matter
This results in an increase in bacteria, all respiring and using up dissolved oxygen
Eventually, fish and other aquatic organisms die due to lack of dissolved oxygen in the water

A-Level Bio (9 decks)

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