Biology A level AQA Paper 2

Glycolysis

Glycolysis

1. Phosphorylation of glucose using ATP;

2. Oxidation of triose phosphate to pyruvate;

3. Net gain of ATP;

4. NAD reduced;

Describe eutrophication

1. (Growth/increase of) algae/surface plants/algal bloom blocks light;

2. Reduced/no photosynthesis so (submerged) plants die;

3. Saprobiotic (microorganisms) aerobically respire OR Saprobiotic (microorganisms) use oxygen in respiration;

4. Less oxygen for fish to respire;

Describe and explain calorimeter

1. Stirrer distributes heat (energy);

2. Insulation/space/air reduces loss/gain of heat OR Insulation/space/air reduces conduction/convection;

3. Water has high (specific) heat capacity;

Why is not all light used in photosynthesis?

1. (Light is) reflected;

2. (Light is) wrong wavelength;

3. (Light) misses chlorophyll/ chloroplasts/photosynthetic tissue;

4. CO2 concentration or temperature is a limiting factor.

How can we find the amount of photosynthetic pigments present?

1. Use (distilled) water and creatinine solution to produce dilutions (series);

2. Addition of (creatinine-)detecting solution (to each solution);

3. Using a known/specified/constant volume of a solution (e.g. diluted creatinine solution);

4. Record absorbance/transmission of solution/s using a colorimeter;

5. Plot dilution/concentration of (creatinine) solution against absorbance/transmission;

Describe role of light in the light dependent reaction

1. Chlorophyll absorbs light OR Light excites/moves electrons in chlorophyll;

2. Electron/s are lost OR (Chlorophyll) becomes positively charged;

Describe how to measure populations

1. Use a grid OR Divide area into squares/sections;

2. Method of obtaining random coordinates/numbers e.g. calculator/computer/random numbers table/generator;

3. Count number/frequency in a quadrat/section;

4. Large sample and calculate mean/average number (per quadrat/section);

5. Valid method of calculating total number of sundews, e.g. mean number of plants per quadrat/section/m2 multiplied by number of quadrats/sections/m2 in marsh;

NPP

1. Represents dry mass / mass of carbon;

GPP - R

1. Represents gross production minus respiratory losses;

Why is aerobic respiration more beneficial?

1. (More aerobic respiration) produces more ATP;

2. Anaerobic respiration delayed;

3. Less or no lactate;

Explain how resting potential is maintained across axon

1. Higher concentration of potassium ions inside and higher concentration of sodium ions outside (the neurone) OR potassium ions diffuse out OR sodium ions diffuse in;

2. (Membrane) more permeable to potassium ions (leaving than sodium ions entering) OR (Membrane) less permeable to sodium ions (entering than potassium ions leaving);

3. Sodium ions (actively) transported out and potassium ions in;

Explain why action potential travels faster in myelinated axons

1. Myelination provides (electrical) insulation;

2. (In myelinated) saltatory (conduction) OR (In myelinated) depolarisation at nodes (of Ranvier);

3. In non-myelinated depolarisation occurs along whole/length (of axon);

Explain phototropism and why plants grow towards light

1. Tip produces IAA;

2. IAA diffuses (into shoot);

3. (More) elongation of cells on one side (than other);

Control variables in IAA investigation

1. Size of shoot/tip;

2. Number of shoot tips;

3. Size/type of agar (block);

4. (Shoots) at same stage of growth/development;

5. Time (period) tips kept on agar OR Time (period) agar/block kept on (cut shoot) OR Time (period shoots) kept in dark;

6. Temperature;

7. (Repeat several times and) calculate a mean;

8. Compare/read degree of curvature (on calibration curve) to determine (IAA) concentration OR Higher the degree of curvature the higher the IAA concentration;

Explain how genes can be linked

1. The (two) genes are linked OR Autosomal linkage;

2. No crossing over (occurs) OR (Linked) genes are close together;

3. No Gl and no gL (gametes produced) OR No Ggll and no ggLl (offspring produced) OR Only GL and gl (gametes produced);

Why isn’t 100% of the glucose reabsorbed

1. High concentration of glucose in blood/filtrate;

2. Not all the glucose is (re)absorbed at the proximal convoluted tubule;

3. Carrier/co-transport proteins are working at maximum rate OR Carrier/co-transport proteins/ are saturated;

Describe and explain features of rods

1. High (visual) sensitivity;

2. Several rods connected to a single neurone;

3. Enough (neuro)transmitter to reach/overcome threshold OR Spatial summation to reach/overcome threshold;

Describe how an action potential is generated

1. Depolarisation of presynaptic membrane;

2. Calcium channels open and calcium ions enter (synaptic knob); 3 (Calcium ions cause) synaptic vesicles move to/fuse with presynaptic membrane and release acetylcholine/neurotransmitter; 4 Acetylcholine/neurotransmitter diffuses across (synaptic cleft);

3. (Acetylcholine attaches) to receptors on the postsynaptic membrane;

4. Sodium ions enter (postsynaptic neurone) leading to depolarisation

Why might there be a high concentration of water in urine?

1. Fat (store) used in respiration/metabolism;

2. Less energy/food (store) is required due to low respiration/metabolism OR Less energy/food (store) is required due less movement;

3. Gluconeogenesis; 4.Low surface area to volume reduces heat loss OR Fat (layer/insulation) reduces heat loss;

4. Long loop of Henle so less water lost;

5. Water provided from respiration;

6. Reduced/no urination;

7. Less evaporation;

Explain how the heart rate is reduced

1. (Lower metabolism so) less/low CO2 (in blood);

2. (Detected by) chemoreceptors;

3. (Chemoreceptors) located in aorta/medulla OR (Chemoreceptors) located in carotid artery;

4. Fewer impulses to cardiac centre; OR Fewer impulses to medulla (oblongata);

5. (More) impulses along parasympathetic/vagus pathway/neurones/nerve OR Fewer impulses along sympathetic pathway/neurones/nerve;

6. (To) SAN;

Why might an inhibitor prevent muscle contraction

1. (Less/No) tropomyosin moved from binding site OR Shape of tropomyosin not changed so binding site not exposed/available;

2. (Fewer/No) actinomyosin bridges formed;

3. Myosin head does not move OR Myosin does not pull actin (filaments) OR (Less/No) ATP (hydrol)ase (activation);

Impact of less/no glucagon

1. Less/no ATP is converted to cyclic AMP/cAMP;

2. Less/no kinase is activated;

3. Less/no glycogen is converted to glucose OR Less/no glycogenolysis;

How does an impulse travel from an axon to a muscle?

1. (Refers to) saltatory conduction OR (Nerve) impulses/depolarisation/ions pass to other neurones OR Depolarisation occurs along whole length (of axon);

2. (Nerve) impulses slowed/stopped;

3. (Refers to) neuromuscular junction OR (Refers to) sarcolemma;

Explain how impulses to the SAN decreases heart rate

1. Slower/fewer impulses along the sympathetic/parasympathetic pathway

2. (impulses) from cardiac centre OR from medulla

3. to SAN

Why does osmosis not occur in the convoluted tubule as much as in the collecting duct

1. Water potential of filtrate/tubule decreased;

2. Less water (reabsorbed) by osmosis (from filtrate/tubule);

3. Collecting duct (is where osmosis occurs);

Describe the role of dopamine/neurotransmitters in inhibiting action potentials from being generated across a synapse

1. (Dopamine) diffuses across (synapse);

2. Attaches to receptors on postsynaptic membrane;

3. Stimulates entry of sodium ions and depolarisation/action potential;

4. (Inside of postsynaptic) neurone becomes more negative/hyperpolarisation/inhibitory postsynaptic potential;

5. More sodium ions required (to reach threshold) OR Not enough sodium ions enter (to reach threshold);

6. For depolarisation/action potential;

What happens if not acetylcholinesterase is not present

1. Less/no acetylcholine broken down;

2. Acetylcholine attaches to receptors;

3. (More) Na+ enter to reach threshold/for depolarisation/action potential/impulse;

Increase in CO2 causes the heart rate to increase, describe how

1. Chemoreceptors detect rise in CO2/H+ /acidity/carbonic acid/fall in pH OR Baro/pressure receptors detect rise in blood pressure;

2. Send impulses to cardiac centre/medulla;

3. More impulses to SAN;

4. By sympathetic (nervous system for chemoreceptors/CO2) OR By parasympathetic (nervous system for baro/pressure receptors/blood pressure);

Non-disjunction

1. (In) meiosis;

2. Chromosomes not separated OR All chromosomes stay in one cell OR Chromosomes do not form (homologous) pairs;

How does allele frequency change?

1. Flies with ADF /allele have selective advantage (in presence of alcohol);

2. So insects (with ADF more likely to) reproduce;

3. Pass on ADF (allele/gene);

4. (So) allele frequency increases;

How to investigate populations

1. Method of randomly determining position (of quadrats) e.g. random numbers table/generator;

2. Large number/sample of quadrats;

3. Divide total percentage by number of quadrats/samples/readings;

Why is increased diversity beneficial?

1. Increase in variety/diversity of species/plants/animals; OR Increase in number of species/populations;

2. Provides more/different habitats/niches OR Provides greater variety/types of food;

Describe speciation

1. Variation/differences due to mutation/s;

2. (Reference to) allopatric (speciation);

3. Smaller/different lakes have different environmental conditions OR Smaller/different lakes have different selection pressures;

4. Reproductive separation/isolation OR No gene flow OR Gene pools remain separate;

5. Different alleles passed on/selected OR Change in frequency of allele/s;

6. Eventually different species/populations cannot breed to produce fertile offspring;

Describe how to mark individuals

1. Capture/collect sample, mark and release;

2. Ensure marking is not harmful (to fish) OR Ensure marking does not affect survival (of fish);

3. Allow (time for) fish to (randomly) distribute before collecting a second sample;

4. (Population =) number in first sample × number in second sample divided by number of marked fish in second sample/number recaptured;

Describe how variation occurs in meiosis

1. Crossing over;

2. Independent segregation/assortment (of homologous chromosomes);

3. Random fusion of gametes OR Random fertilisation;

Explain how new ecosystems form over time

1. (Colonisation by) pioneer species;

2. Pioneers/species/organisms change the environment/habitat/conditions/factors;

3. (Environment becomes) less hostile for other/new species OR (Environment becomes) more suitable for other/new species OR (Environment becomes) less suitable for previous species;

4. Change/increase in diversity/biodiversity;

5. (To) climax community;

Explain how a new ecosystem is formed

1. Beach grass is the pioneer (species);

2. Pioneers/named species change the (abiotic) environment/habitat/conditions/factors;

3. (So) less hostile for named species OR (So) more suitable for named species;

4. Conifer/hardwood trees represent climax community;

How does the allele for LP change over time

1. Allele due to mutation;

2. Milk provides named nutrient;

3. Individuals with LP more likely to survive and reproduce OR Individuals with advantageous allele more likely to survive and reproduce;

4. Directional selection;

5. Frequency of allele increases (in the offspring/next generation);

Define a dominant allele

1. Dominant allele;

2. (Always) expressed/shown (when present in phenotype/offspring)

OR

1. Expressed when only one (dominant allele) present;

Phenotype

1. (Expression / appearance / characteristic due to) genetic constitution/genotype/allele(s);

2. (Expression / appearance / characteristic due to) environment;

Interspecific competition

1. Compete (with fertile males) to mate/for food/resources OR intraspecific competition;

2. Do not reproduce/breed OR Reduces population (of mosquitoes);

Describe a mutation

1. Change in (sequence of) amino acid(s)/primary structure;

2. Change in hydrogen/ionic/disulfide bonds;

3. Alters tertiary/30 structure;

Describe affect of methylation of tumour suppressor gene

1. Methyl groups (could be) added to (both copies of) a tumour suppressor gene;

2. The transcription of tumour suppressor genes is inhibited;

3. Leading to uncontrolled cell division

Describe benign tumour

Cells of benign tumours cannot spread to other parts of the body / metastasise;

OR

Cells of benign tumours cannot invade neighbouring tissues.

Explain how immune system can target tumour cells

1. Faulty protein recognised as an antigen / as a ‘foreign’ protein;

2. T cells will bind to faulty protein / to (this) ‘foreign’ protein;

3. (Sensitised) T cells will stimulate clonal selection of B cells;

4. (Resulting in) release of antibodies against faulty protein

How does oestrogen enter the cell?

1. Lipid soluble;

2. (Diffuse through) phospholipid (bilayer);

How does a lipid soluble hormone bind to a transcription factor?

1. Has a (specific) tertiary structure/shape;

2. (Structures are) complementary;

Action of transcription factors

1. (AR is) a transcription factor;

2. Binds to DNA/promoter;

3. (Stimulates) RNA polymerase;