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A Level Biology Paper 2 > Key Points Document > Flashcards

Key Points Document Flashcards

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1
Q

Describe the light dependent reaction

A

Chlorophyll absorbs light energy and excites its electrons
Electrons removed and chlorophyll oxidised via photoionisation
Electrons move along Electron Transport Chain, releasing energy via REDOX reactions
Energy released used to create an electrochemical gradient
H+ ions diffuse through ATP synthase
Providing the energy to join ADP and Pi into ATP via photophosphorylation
Photolysis of water produces 2 protons, 2 electrons and 0.5 oxygen
NADP reduced by electrons

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2
Q

Describe the light independent reaction

A 
Carbon dioxide combines with RuBP
Producing 2 GP
GP reduced to Triose Phosphate
Using reduced NADP
Using energy from ATP
Triose Phosphate converted to glucose
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3
Q

ATP is produced in the light dependant reaction

Suggest why this is not plants only source of ATP

A

Plants don’t photosynthesise in the dark
Not all parts of a plant photosynthesise
Plants require more ATP than is produced in the light dependant reaction
ATP is used in active transport

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4
Q

Effect of introducing a herbicide/inhibitor on the electron transport chain

A

Reduced transfer of protons across the thylakoid membrane
Reduced electrochemical gradient across thylakoid membrane
So less ATP
So less reduced NADP
So light independant reaction slows
Less GP reduced to Triose Phosphate

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5
Q

Describe what happens during photoionisation in the light dependant reaction

A

Chlorophyll absorb light which excites electrons

Electrons are lost and move down the electron transport chain

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6
Q

When producing a chromatogram explain why the origin is marked using a pencil rather than pen

A

Ink and leaf pigments would mix
Origin would be in different place with pen
With pencil the origin is still visible and in same position

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7
Q

While making a chromatogram describe the method used to separate the pigments after the solution of pigment has been applied to origin

A

Level of solvent below origin line

Remove before solvent reaches the top

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8
Q

Suggest and explain the advantage of having different colour pigments in leaves

A

Absorb different/more wavelengths of light for photosynthesis

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9
Q

Describe how oxidation tales place in glycolysis and the krebs cycle

A

Removal of hydrogen (dehydrogenation)
By enzymes (dehydrogenase)
H accepted by NAD (forms reduced NAD)
In Krebs cycle, H accepted by FAD (forms reduced FAD)

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10
Q

Water is a waste product of aerobic respiration

Describe how water is formed at the end of aerobic respiration

A

Oxygen is the final electron acceptor

Combines with protons and electrons to form water

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11
Q

Explain why converting pyruvate to lactate allows the continued production of ATP by anaerobic respiration

A

Regenerates NAD/NADH oxidised

So glycolysis can continue

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12
Q

Explain how the amount of ATP is increased by reactions occurring inside a mitichondria

A

Oxidation/removal of electrons and hydrogen
From pyruvate
Acetyl CoA the 6 carbon compound
Substrate level phosphorylation produces ATP in krebs cycle
Producing NADH and FADH
In the matrix of the mitochondria
Electrons move into the ETC and pass along carriers
Releasing energy
Protons move into innermembrsne space
ADP and Pi using ATP synthase for ATP

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13
Q

Why is a log scale used to record the numbers of cells/bacteria

A

Large range/difference in numbers

Reference to exponential increase

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14
Q

Give two reasons why a respirometer is left for 10 minutes when first placed in the bath

A

Equilibrium reached
Allow for expansion/pressure change in apparatus
Allow respiration rate of x to stabilise

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15
Q

The mitochondria in muscles contain many cristae

Why is this an advantage

A

Larger surface area for electron carrier system/oxidative phosphorylation
More room for attachment of ATP synthase
Provide ATP so energy for muscle contraction

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16
Q

Describe the role of coenzyme and carrier protein in ATP synthesis

(Describe the events of oxidative phosphorylation)

A

NAD/FAD reduced by hydrogen
H+ ions transferred from coenzyme to coenzyme in the ETC on cristae of inner membrane
Energy released through series of redox reactions
Energy used to pump protons into innermembrane space
H+ diffuses through ATP synthase to produce ATP from ADP and Pi

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17
Q

Biomass

A

Mass of carbon (organic compounds)

Dry mass of tissue per given area

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18
Q

What do you do to remove all water from a tissue sample

A

Regularly weigh and heat

Until mass is constant

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19
Q

GPP

A

Gross Primary Productivity

Chemical energy stored in plant biomass in a given area or volume (rate of photosynthesis)

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20
Q

NPP

A

Net Primary Production

Chemical energy stored in plant biomass after respiratory losses to the environment have been taken into account (NPP=GPP-R)
Available for new plant growth, reproduction or for other trophic levels in the ecosystem (like herbivors or saprobionats)

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21
Q

Why is the percentage of light energy trapped by producers very low

A

Relected/absorbed by water vapour
Wrong wavelength
Tramsmitted/passes between chloroplast/two few chloroplast

22
Q

The biomass of primary consumers is less than the biomass of producers
Why

A 
Loss of energy as heat through thermoregulation
Loss of energy in respiration
Loss of energy in excretion and urine
Indigestible parts like roots and bark
So less energy available to pass on
23
Q

Describe and explain why the efficiency of energy transfer is different at different stages

A

Some light energy fails to strike chlorophyll or isn’t the correct wavelength
Efficiency of photosynthesis is low in plants (~2%)
Respiratory losses, excretion, faeces and indigestible parts of plants and animals
Energy lost as heat
Efficiency of transfer to consumers greater than transfer to producers (~10%)
Efficiency low in older animals/warm blooded animals
Carnivores use more of their food than herbivores

24
Q

Explain how the intensive rearing of domestic livestock increases net productivity

A

Slaughtered when still growing and young so mire energy transfered to biomass
Fed on controlled diets so higher proportion of food absorbed
Movement restricted so less energy used for respiration
Kept inside and heated so less heat loss and no predators
Genetically selected for high productivity

25
Q

Describe the need for plants to photosynthesis and respire

A

In the dark no ATP produced in photosynthesis
Some tissues unable to photosynthesise
ATP cannot be moved from cell to cell/stored
Plants use more ATP than is produced in photosynthesis
ATP used for active transport
ATP used for protein synthesis

26
Q

Why is the concentration of carbon dioxide different at different heights and times over 24 hours

A

High concentration at night because no photosynthesis in the dark
In the dark plants and other organisms respite so produce carbon dioxide
In light, the net uptake of carbon dioxide by plants uses more carbon dioxide than they produce so carbon dioxide decreases
Decrease in carbon dioxide concentration with increasing height
At ground level fewer leaves so less photosynthesis and organisms are respiring which reduces carbon dioxide concentration lower down

27
Q

What is meant by a carbon sink

A

Takes up and stores carbon/carbon dioxide

Peat, roots, coal, trees, chalk, shells

28
Q

What is global warming

A

Increase in temperature of earths surface
Due to an increase in greenhouse gases like carbon dioxide
Which trap and reflect back heat/infra red into the atmosphere
Causing an increased greenhouse effect
And melting ice caps, increased flooding
Leading to climate change

29
Q

Describe the role of sabrobionts in the nitrogen cycle

A 
Use enzymes to decompose proteins/DNA/urea
Releasing ammonia (ammonium ions)
30
Q

How do carbon containing compounds in pine leaves that fall from trees be absorbed and used for growth by saprobionts living in soil

A

Extracellular digestive enzymes are secreted and break down compounds
Absorbed by saprobionts because soluble
Used to synthesise structural component
And in respiration to provide energy for growth

31
Q

Nitrogen compounds in plants are made available for the main crop after ploughing

Describe the role of microorganisms in this process

A

Proteins/amino acids broken down
Ammonification releases ammonium compounds
By saprobions (decomposers)
Nitrities are converted to nitrates
By nitrifying bacteria
Nitrates absorbed into roots via active transport

32
Q

Why would units upg-¹ be used

A

up because very little amounts of x
up because avoids use of lots of decimal places or standard form
g^-1 allows comparisons to be made between samples

33
Q

Give two examples of biological molecules containing nitrogen that would be removed when a crop is harvested

A 
DNA
RNA
Nucleic acid 
Amino acid
NADP
ATP
Chlorophyll
34
Q

Why are phosphates needed for growing plants

A 
Production of phospholipids
In cell membranes
ATP synthesis
Production of DNA
Production of RNA
Production of NADP
35
Q

How can a lack of phosphates in soil affect plant growth

A

Needed for ATP synthesis so less respiration and less energy for growth
Needed to make nucleotides so less DNA and protein synthesis
Required to make RuBP and NADP so less carbon dioxide fixed to make glucose
Required in phospholipids in membrane

36
Q

Advantage of having Mycorrhizae growing near plants

A

Help plants defend themselves so increase yield

Help plants take up nitrates and phosphates causing increased growth snd yield

37
Q

Describe the process of eutrophication

A

Nitrates/phosphates/ammonium ions flushed into waterway
Increased algal bloom
Light blocked out
Plants at the bottom unable to photosynthesis and die
Increase in saprobionts so increase rate of aerobic respiration
Organisms respiring aerobically die from lack of oxygen (anoxic)
Increase in anaerobic microorganisms
Production of toxins

38
Q

Causes of genetic variation

A

Crossing over
Independent segregation
Random fusion of gametes
Mutation

39
Q

Genome

A

All the DNA in a cell/total number of DNA bases

All the genes/genetic material in an organism

40
Q

How do multiple alleles of a gene arise

A

Mutations

Which are different/at different positions in the gene

41
Q

Reasons why observed phenotypic ratios aren’t always the same as expected

A 
Small sample size
Epistasis
Fusion of gametes is random
Linked genes/sex linkage
Lethal genotypes (die early)
42
Q

Gene linkage

A

Gene on same chromosome

43
Q

Rules for dominant alleles

A

Affected offspring must have at least one affected parent
Unaffected parent only have unaffected offspring
If both parents are affected and have an unaffected offspring the parents must be heterozygous

44
Q

Why are males more likely to express recessive sex linked diseases

A

Recessive allele always expressed in males since they only need one
Females would need two recessive copies

45
Q

Totipotent

A

Can give rise to a complete human/all cell types

Zygote

46
Q

Pluripotent

A

Can give rise to most cell types

Foetus

47
Q

Hoe can cells produced from stem cells have the same genes but be different types

A

Not all genes are switched on/active

Depends on promoters and transcription factors

48
Q

Allopatric speciation

A 
Geographical isolation
Separate gene pools (no interbreeding)
Variation due to mutation
Different selection pressures
Different alleles deemed advantageous
Selected for organisms more likely to survive and reproduce
Leading to change in allelic frequencies
So different they can no longer breed to produce fertile offspring
49
Q

Sympatric speciation

A 
Leads to reproductive isolation 
Separate gene pools so no interbreeding
Selection for different alleles
Selected organisms more likely to survive snd reproduce
Leading to change in allelic frequencies
Can't breed to produce fertile offspring
50
Q

Succession

A

Colonisation by pioneer species
Causing change in environment eg more hummus
So less hostile for new species
New species makes it less suitable for previous species
Change in biodiversity
Stability increases
Climax community

51
Q

Mark release recapture

A

Capture sample, mark and release
Marking should not harm organisms
Take a second sample after integrated back into population and count number of marked individuals

( Sample number 1 × Sample number 2 )/ Number marked in sample 2

52
Q

How do you decide how many quadrants to use

A

Calculate a running mean
When there’s enough quadrants there is little change/levels out
Enough to carry out a statistical test
Large number to make sure results are reliable
Need to be realistic, can it be carried out in time available

A Level Biology Paper 2 (16 decks)

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