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A Level Biology Paper 2 > Key Points Document > Flashcards

Key Points Document Flashcards

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
Describe the need for plants to photosynthesis and respire
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
Why is the concentration of carbon dioxide different at different heights and times over 24 hours
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
What is meant by a carbon sink
Takes up and stores carbon/carbon dioxide | Peat, roots, coal, trees, chalk, shells
28
What is global warming
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
Describe the role of sabrobionts in the nitrogen cycle
``` Use enzymes to decompose proteins/DNA/urea Releasing ammonia (ammonium ions) ```
30
How do carbon containing compounds in pine leaves that fall from trees be absorbed and used for growth by saprobionts living in soil
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
Nitrogen compounds in plants are made available for the main crop after ploughing Describe the role of microorganisms in this process
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
Why would units upg-¹ be used
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
Give two examples of biological molecules containing nitrogen that would be removed when a crop is harvested
``` DNA RNA Nucleic acid Amino acid NADP ATP Chlorophyll ```
34
Why are phosphates needed for growing plants
``` Production of phospholipids In cell membranes ATP synthesis Production of DNA Production of RNA Production of NADP ```
35
How can a lack of phosphates in soil affect plant growth
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
Advantage of having Mycorrhizae growing near plants
Help plants defend themselves so increase yield | Help plants take up nitrates and phosphates causing increased growth snd yield
37
Describe the process of eutrophication
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
Causes of genetic variation
Crossing over Independent segregation Random fusion of gametes Mutation
39
Genome
All the DNA in a cell/total number of DNA bases | All the genes/genetic material in an organism
40
How do multiple alleles of a gene arise
Mutations | Which are different/at different positions in the gene
41
Reasons why observed phenotypic ratios aren't always the same as expected
``` Small sample size Epistasis Fusion of gametes is random Linked genes/sex linkage Lethal genotypes (die early) ```
42
Gene linkage
Gene on same chromosome
43
Rules for dominant alleles
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
Why are males more likely to express recessive sex linked diseases
Recessive allele always expressed in males since they only need one Females would need two recessive copies
45
Totipotent
Can give rise to a complete human/all cell types | Zygote
46
Pluripotent
Can give rise to most cell types | Foetus
47
Hoe can cells produced from stem cells have the same genes but be different types
Not all genes are switched on/active | Depends on promoters and transcription factors
48
Allopatric speciation
``` 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
Sympatric speciation
``` 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
Succession
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
Mark release recapture
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
How do you decide how many quadrants to use
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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