Biology aqa A level common questions

Biology aqa A level common questions with answers well elaborated 100% success. 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 Suggest why diabetes insipidus is more common in males ? - correct answersBc males only have X chromosome do not have Y chromosome single copy of recessive allele will be expressed A recessive allele which has harmful effects is able to reach a higher frequency in a population than a harmful dominant allele. Explain how ? - correct answersrecessive allele can be carried by individuals showing effects dominant allel always expressed organisms that are affected are more likely to reproduce therefore recessive alleles are more likely to be passed on In some forms of kidney disease, proteins from the blood plasma are found in the urine. Which part of the nephron would have been damaged by the disease to cause proteins from blood plasma to be present in the urine? Explain your answer - correct answersglomerulus/ bowmans capsule basement membrane proteins are large molecules cannot normally pass through filter can only pass through if filter damaged Describe the role of the hormone glucagon in the control of blood sugar concentration ? - correct answersglucagon binds to specific receptor on liver cells activation of enzymes in liver hydrolysis of glycogen F.D of glucose out of liver cells increases blood glucose levels Explain two ways in which the cells of the proximal convoluted tubule are adapted for reabsorption.? - correct answersmicrovilli provide a large S.A for reabsorption carrier protiens in membrane for A.T channel proteins for F.D many mitochondria for A.T and providing Atp Explain the role of the loop of Henle in the absorption of water from the flitrate ? - correct answersin the ascending limb na+ ions actively transported ascending limb impermeable to water in descending limb na+ ions diffuse in descending limb h2o moves out low w.p ( high conc of ions in medulla) the longer the loop, lower w.p in medulla h2o leaves collecting duct by osmosis down w.p gradient Explain the role of ADH in the production of concentrated urine? - correct answerswhen w.p of blood too low it is detected by receptors in hypothalamus pituitary secretes releases more ADH ADH increases permeability opens channels for h2o in DCT more h2o reabsorbed into blood by osmosis down w.p gradient Explain how different subspecies of giraffe may have evolved from a common ancestor ? (5) - correct answers1) no interbreeding/geographical isolation 2)variation due to mutation linked to different markings (colours) 3) survival linked to different markings different selection pressure 4) adapted organisms survive and reproduce ( different reproductive success) 5) increase in allele frequencies describe how crop plants use light energy during the light dependent reaction? (5) - correct answers1) excites electrons 2) electrons move along electron transfer chain releasing energy 3) energy used to join ADP + Pi - ATP 4) photolysis of H2O produces P, e- and O2 5) NADP reduced by hydrogen describe how altered DNA may lead to cancer ? (6) - correct answers1. (DNA altered by) mutation; 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