2024 BIOLOGY AQA A LEVEL COMMON EXAM QUESTIONS, Exams of Advanced Education

Download 2024 BIOLOGY AQA A LEVEL COMMON EXAM QUESTIONS and more Exams Advanced Education in PDF only on Docsity! 2024 BIOLOGY AQA A LEVEL COMMON EXAM QUESTIONS    give two factors other than age and gender that would affect the concentration of creatinine in the blood ? - CORRECT-ANSWERSmuscle/ body mass ethnicity Explain how the cells of the collecting duct are able to absorb water from the filtrate through the protein channels in their plasma membranes? - CORRECT-ANSWERSlower w.p/ more negative inside tubule cells so h2o enters by osmosis structure of DNA ? - CORRECT-ANSWERSsugar phosphate backbone provides strength and protects bases large molecules stores lots of info helix - compact base sequence codes for AA double stranded so strands act as templates - comp b.p weak h-bonds for strand seperation describe how dna is replicated? - CORRECT-ANSWERSstrands seperate dna helicase breaks h bonds both strands act as a template free nucleotides attach by complementary b.p dna polymerase joins nucleotides on new strand h-bonds reform semi conservative new dna contains 1 old and 1 new strand starch ? - CORRECT-ANSWERSa-glucose insoluble in h2o so doesn't affect w.p by osmosis coiled - compact - helical shape branched so glucose is released for respiration Cellulose ? - CORRECT-ANSWERSb-glucosw straight chain 1,4 glycosidic bonds long unbranched chain joined by h-bonding forms microfibrils provides rigidity glycogen ? - CORRECT-ANSWERSa-glucose branched/coiled 1,4 + 1,6 glucosidic bonds branched hydrolysed to glucose used in respiration why are enzymes specific ? - CORRECT-ANSWERStertiary structure of enzyme means active site is only complementary to substrate active site changes shape to become complementary ( induced fit) by forming e-s complexes only substrate can bind describe induced fit ? - CORRECT-ANSWERSactive site is not complementary to substrate active site changes shape as e-s complexes form ATP ? - CORRECT-ANSWERSreleases relatively small amounts of energy releases energy instantaneously involves a single reaction immediate energy source soluble easily hydrolysed lock and key model? - CORRECT-ANSWERSactive site does not change shape fixed shape already fits substrate xerophtic features the leaves might have ? - CORRECT-ANSWERShairs so trap h2o vapour and w.p.g stomata in pits decreased thick waxy cuticle increases diffusion distance waxy cuticle so reduces transpiration cohesion-tension theory? - CORRECT-ANSWERSh2o lost from leaf b.c of transpiration of h2o mol lowers w.p of mesophyll cells h2o pulled up xylem creates tension h2o molecules stick together by h-bonds forming continuous h2o column adhesion of h2o molecules to the walls of the xylem measurements needed for index of diversity ? - CORRECT-ANSWERSn.o of individuals of each species total n.o of individuals 2. (mutation) changes base sequence; 3. Of gene controlling cell growth / oncogene / that monitors cell division; 4. Of tumour suppressor gene; 5. Change protein structure / non-functional protein / protein not formed; 6. (Tumour suppressor genes) produce proteins that inhibit cell division; 7. Mitosis; 8. Uncontrolled / rapid / abnormal (cell division); 9. Malignant tumour; why would one area ( e.g wild ower meadow) have a higher species diversity than another e.g potato field ? (5) - CORRECT-ANSWERS1) there would be more plant species 2) hence more habitats 3) more niches 4) more food sources 5) the area is able to support more biomass describe competitive and non-competitive inhibition of enzyme ? (6) - CORRECT-ANSWERScompetitive inhibitor 1) inhibitors reduce binding of enzyme to substrate/prevent formation of e-s complexes 2) inhibitor similar shape to substrate binds to active site of enzyme 3) inhibition can be overcome by adding more substrate non-competitive inhibitor 4) inhibitor binds to site on enzyme other than active site 5) prevents formation of active site/ changes shape of active site 6) cannot be overcome by adding more substrate Meiosis - CORRECT-ANSWERScell ÷ to form gametes 2 ÷ forming 4 haploid daughter cells genetically non-identical due to crossing over and independent segregation (assortment) crossing over- creates new combination of alleles independent assortment - creates new combination of chromosomes Mitosis - CORRECT-ANSWERScell divides for growth and repair 2 genetically identical daughter cells prophase - nuclear membrane breaks down and chromosomes condense metaphase- chromosomes line up on the equator and spindle fibres attach to chromosome at the centromere anaphase - centromeres split and chromatids move to opposite poles telophase - nuclear membrane reforms, chromosomes uncoil and cell ÷by cytokinesis interphase - cells grow and organelles multiply and dna replicates, organelles multiply ready to ÷ heart disease ? (6) - CORRECT-ANSWERSatheroma is cholesterol in artery wall atheroma is linked to blood clot blocks coronary artery ( artery supplying heart muscle/tissue/ cells) reduces o2 supply to heart muscle/ tissues/cells unable to respire so die Meiosis - CORRECT-ANSWERSprophase 1 - nuclear membrane breaks down, chromosomes condense metaphase 1 - homologous pair of chromosomes line up next to each other on the equator, spindle attaches to chromosome at the centromere, crossing over chromatid takes place anaphase 1 - homologous pairs seperate 1 to each pole ( independent assortment ) telophase 1 - nuclear membrane reforms, cell ÷ by cytokinesis prophase 2 - nuclear membrane breaks down, chromosomes condense metaphase 2- chromosomes line up on the equator and spindle attaches to chromosome at the centromere anaphase 2 - centromere split, chromatids move to opposite poles telophase 2- nuclear membrane reforms, chromosomes uncoil, cell ÷ by cytokinesis natural selection? (6) - CORRECT-ANSWERS1) variation of phenotypes in population due to random mutations 2) individuals that do not show behaviour die 3) change in selection pressue- environmental change 4) allele frequency increases in population 5) those who have the advantageous alleles, survive and reproduce and pass on their alleles giving a selective advantage to their offspring 6) until all individuals show the phenotype frequency of alleles in the population changes tissue fluid? (6) - CORRECT-ANSWERShigh b.p/h.p forces h2o out large proteins remain in capillary low w.p in capillary due to plasma proteins h2o enters capillary by osmosis describe what happens to chromosomes in meiosis? (8) - CORRECT- ANSWERSchromosomes shorten/ condense chromosomes associate in homologous pairs/ formation of bivalents crossing over / chiasmata forms join to spindle fibres at equator join via centromere homologous chromosomes move to opposite poles/ chromosomes separate pair of chromatids separated in 2nd ÷ Explain how the gills of fish are adapted for efficient gas exchange ? (6) - CORRECT-ANSWERSmany lamallae on many filaments provide a large s.a increases diffusion thin epithelium of lamellae short diffusion pathway increases rate of diffusion blood flows over the gills in the opposite directions to blood flowing in the capillaries ( countercurrent flow) maintains a steep diffusion gradient along whole length of gill lamellae- equilibrium is not achieved as water always meets blood with higher o2 conc large n.o of capillaries and circulation replaces oxygenated blood with deoxygenated blood to maintain steep conc gradient-increases rate of diffusion pressures change due to ventilation replaces deoxygenated h2o as oxygenated h2o maintains steep diffusion gradient increase rate of diffusion describe aseptic techniques and justify the chosen method ? (6) - CORRECT- ANSWERSkeep lid on petri dish to prevent unwanted bacteria contamination wear gloves and wash hands prevent spread of bacteria outside lab use sterile pipette or flame loop of the culture to maintain a pure culture of bacteria use bunsen burner to maintain upward movement of air helps to prevent contamination of culture when lid is removed describe strucure of an AA moelcule and explain how AA link together? (8) - CORRECT-ANSWERSAA based on with 4 groups attached Nh2 and carboxyl (cooh) group r group and h r group differs from 1 amino acid to another AA joined by condensation bond formed between Nh2 and cooh involves removal of h2o molecule h from nh2 and oh from cooh Mitosis vs. Meiosis differences (4) - CORRECT-ANSWERSmitosis- chromsomes n.o same (diploid cells) , meiosis- chromosomes n.o halved (haploid cells) mitosis- cells produced identical, meiosis- cells produced non-identical mitosis- only 1 ÷/ 2 cells, meiosis- only 2 ÷/ 4 cells spindle fibres contract/ centromeres ÷ sister chromatids separate in anaphase and move to opposite poles each pole receives identical copies of each chromosome nuclear envelope forms around each gorup of chromosomes at each pole each chromatid uncoils and unwinds describe the differences between active and passive immunity? (6) - CORRECT-ANSWERSactive does involve memory cells, passive does not active involves production of antibody by memory cells/ plasma passive involves antibody introduced into body from outside active long term, because antibody produced in response to antigen passive is short term, bc antibody given is broken down active can take time to develop/work , passive is fast acting genetic fingerprinting? (6) - CORRECT-ANSWERS× dna is cut using restriciton endonuclease enzyme × electrophoresis run an electric current seperates dna according to the length of dna fragments × shorter dna fragments travel further × southern blotting place nylon sheet over the gel picks up radioactivity autoradiography × place photographic film/ x-ray over the nylon the radioactivity produces a picture of bars × dna made is single stranded structure of plasma membrane and explain how different substances are able to pass through the membrane by diffusion? (6) - CORRECT-ANSWERS× phospholipid forming bilayer with 2 layers × hydrophilic heads on the outside and hydrophobic tails on the inside × carrier proteins and channel proteins × pass right through intrinsic or extrinsic × substances move down conc gradient × water and ion through channel proteins × small lipid soluble molecules pass through phospholipid layer × carrier protiens involved in F.D describe the mass flow hypothesis for the mechanism of translocation in plants ? (6) - CORRECT-ANSWERS× mass flow from source to sink × in the leaf sugars (sucrose) is actively transported into the phloem (atp against conc gradient) × by companion cells × lowers w.p of sieve tubes in phloem and h2o enters by osmosis × increase in H.P causes mass movement towards roots × at sink sugars are removed × sugars in root are converted to starch for storage or used for respiration describe how the cells of the xylem are adapted for this function? (6) - CORRECT-ANSWERS× thick cell walls - withstand negative pressure × narrow tubes - increases s.a for adhesion × molecules in cell walls - allows adhesion × have no cytoplasm so a continous column of h2o Bohr effect ? (6) - CORRECT-ANSWERSincrease respiration increase co2 in blood blood becomes more acidic lowers haemoglobin affinity for o2 and release more o2/ dissociates more readily to muscles/cells/ tissues for rapid respiration oxyhaemoglobin dissociation curve shifts to the right (bohR) Carbohydrate digestion? (6) - CORRECT-ANSWERSamylase (saliva secreted by pancreas) starch to maltose maltase enzyme (small intestine) maltose to glucose hydrolysis of glycosidic bond advantage of shrew having haemoglobin with a dissociation curve to the right explain? - CORRECT-ANSWERSat the tissues low p.p of o2 - haemoglobin is less reduced affinity more o2 released oxyhaemoglobin dissociated more readilt more o2 released allows greater respiration rate explain how o2 is loaded and transported in the blood ? (6) - CORRECT- ANSWERShaemoglobin carries o2 has a high affinity for o2 in r.b.c loading in lungs at high p.p of o2 dissociates to respiring cells / tissues at low p.p of o.2 unloading linked to higher o2 dissociation curve shifts right How does phagocytosis destroy pathogens ? ( 6) - CORRECT- ANSWERSphagocyte attracted by a substance/ recognises a foreign antigen pathogen engulfed / ingested enclosed in a vacuole / vesicle joins with a lysosome lysosome contain hydrolytic enzymes pathogen digested/ molecules hydrolysed describe and explain how the structure of DNA results in accurate replication? - CORRECT-ANSWERS2 strands therefore s.c.r possible b.p holds strands together weak h-bonds allow strands to seperate base sequence exposed so acts as a template/ can be copied a with t, c with g, complementary copy dna now made of one parent strand and the new strand a mutation can lead to the production of a non functional enzyme. explain how? (6) - CORRECT-ANSWERS× change in base sequence of DNA × change in AA sequence/ 1° structure of enzyme × change in h, ionic/ disulphide bonds × change in 3° structure × change in active site × substrate not complementary cannot bind to active site no e-s complexes the events that take place dyeint interphase and mitosis lead to the production of genetically cells. explain how? (4) - CORRECT-ANSWERS× dna replicated × involving specific complementary b.p × 2 identical sister chromatids × each chromatid moves/ seperated to opposite poles of cell how do the structures of mrna and rna compare ? (4) - CORRECT- ANSWERSmrna has more nucleotides than trna mrna is a straight linear shape trna is clover leaf shaped molecule mrna contains no paired bases but trna has some paired bases/ h-bonds describe how meiosis causes this variation and explain the advantage of variation in the species ? (6) - CORRECT-ANSWERScrossing over involves exchange of alleles between homologous chromosomes independent segregation maternal and paternal chromosomes line up in meiosis randomly with their homologous partner produces gametes which have a random combination of maternal and paternal allele different adaptations/ some better adapted some survive, reproduce and pass on allele allow for coping in a changing environment Explain how tissue fluid is formed and how it may be returned to the circulatory system ? (6) - CORRECT-ANSWERSH.P of blood high at arterial end fluid/h2o/ soluble molecules pass out proteins/ large molecules remain this lowers the w.p (w.p more -) Explain 3 features of a plasma membrane adapt it for its functions ? (6) - CORRECT-ANSWERSphospholipid bilayer as a barrier to h2o soluble molecules -move through channel proteins allows non polar substances to pass bilayer is fluid can form vesicles channel proteins through bilayer by A.T using ATP glycoprotein/glycolipids extrinsic proteins act as receptors increase stability carriers change shape structure of fibrous proteins ? - CORRECT-ANSWERSlong chain of AA folding of chain in to a-helix/ b-pleated sheets several polypeptide chains together h-bonds/ disulfide bonding fibres provide strength and flexibility sheets provide flexibility e.g keratin in hair, collagen in bone insoluble because external R groups are non polar some substances can cross the cell surface membrane of a cell by simple diffusion through the phospholipid bilayer describe other ways by which substances cross this membrane ? (6) - CORRECT-ANSWERSby osmosis from a higher w.p to a lower w.p down a w.p gradient through h2o channels by F.D down conc gradient by active transport carrier proteins against conc gradient using ATP from respiration by phagocytosis engulfing by cell surface membrane to from vesicle-endocytosis fusion of vesicle with cell surface membrane - exocytosis compare the structures of a prokaryotic cell with a eukaryotic cell ? similarities and differences (6) - CORRECT-ANSWERSdifferences × p - has no membrane bound organelles ( mitochondria, golgi,E.R ), e- has membrane bound organelles × p - do not have DNA inside a nucleus/ dna is in a loop rather than linear (e) × p - smaller ribosomes (70s), e- larger ribosomes (80s) × p- capsule, flagellum , cell walls , plasmids , e- does not similarities × both have cytoplasm × ribosomes × phospholipid membrane /cell membrane describe and explain the effects of increasing light intensitt on the tension in the xylem vessels in the leaves ? (7) - CORRECT-ANSWERS1) increase in light intensity causes stomata to open more 2) increase evaporation, increase h2o loss from mesophyll cells 3) more h2o diffuses out of the leaves through the stomata which lowere w.p of mesophyll c ells 4) more h2o moves from xylem in to mesophyll cells by osmosis down a w.p gradient 5) more h2o is pulled up due to h2o molecules 'sticking' together by h bonds cohesion forms a continuous column of h2o 6) creates greater tension in the xylem and creates more - pressure than atmospheric pressure 7) tension and adhesion of h2o molecules to the walls of the xylem create an inward pull to the walls of the xylem Explain ecological succession ? (6) - CORRECT-ANSWERS1. colonisation/pioneering; 2. microscopic plants at start; 3. death / decomposition; 4. named change in environment e.g. increase in organic matter/ stabilisation; 5. new species colonise once there is a change; 6. increase in number of species 7. increase in biomass/ more niches; 8. increase in nutrient availability; 9. change from hostile environment / more stability; explain how root pressure and cohesion tension are responsible for the movement of h2o in xylem vessels? (14) - CORRECT-ANSWERSroot pressure × a.t of salts in to xylem × endodermis × prevents leakage × lower w.p inside xylem × h2o enter xylem by osmosis down w.p gradient cohesion tension × solar energy source × evaporation of h2o × w.p.g created across leaf × tension created in xylem × cohesion of h2o molecules maintains column due to h bonding insect gas exchange and h2o loss ? (6) - CORRECT-ANSWERSgas exchange ×air enters trachea through open spiracles × diffusion gradient in trachea × trachea associated with all cells × o2 diffuses into cells × ventilation replacing air in trachea h2o loss × body covered with waterproof waxy cuticle × spiracles are able to close H2o? (10) - CORRECT-ANSWERSdipolar molecule h delta positive and o delta negative forms h bonds high latent heat of evaporation efficient cooling mechanism high specific heat capacity large amounts of energy to change temp thermally stable environment for aquatic organisms - use less energy for temp control internal temp of organisms change slowly h2o good solvent - ionic compounds dissolve in h2o e.g Na+ cohesion and adhesion h2o pulled up xylem ( cohesion tension theory) describe why an antibody will only detect a specific antigen? (3) - CORRECT- ANSWERS× because the antibody has a specific and complementary binding site has a specific tertiary structure × because the antibody is complementary and binds to a specific antigen to form antigen-antibody complex × variable region is made of a sequence of AA