A-level biology AQA (Questions with 100% correct answers)

give the two types of molecule from which a ribosome is made correct answers - protein - RNA describe the role of a ribosome in the production of a polypeptide correct answers - mRNA binds to ribosome - idea of two codons/ binding sites - allows tRNA with anti-codons to bind/associate - catalyses formation of peptide bonds between amino acids held by tRNa molecules - moves along mRNA to the next codon - polypeptide produced describe the structure of glucose correct answers - polysaccharide of many alpha glucose molecules - joined by glycosidic bonds with a branched surface. how does glycogen act as a source of energy... do not include transport across membranes correct answers - hydrolysed to glucose - glucose used in respiration suggest and explain two ways the cell-surface membranes of the cells lining the uterus may be adapted to allow rapid transport of nutrients correct answers - membrane folded so increases/large surface area for fast rate of diffusion - large number of channel/carrier proteins in the membrane for facilitated diffusion NHE3 actively transports one sodium ion into the cell in exchange for one proton out of the cell...how... correct answers - co transport - uses ATP (hydrolyses it) - sodium ion and proton bind to protein - protein changes shape to move the sodium ion across the membrane. tenapanor does reduce salt absorption in the gut... info provided... explain how reached this conclusion correct answers - tenapanor causes a significant increase - there is less than 0.05 probability that the difference is due to chance - more salt in the gut reduces water potential in the gut - so less water absorbed out of gut by osmosis high absorption of salt from the diet can result in higher than normal concentration of salt in the blood plasma entering capillaries. this can lead to a build up of tissue fluid... correct answers - higher salt= low w.p of tissue fluid - so less water returns to capillary by osmosis at venule end describe how bacteria divide correct answers - binary fission of prokaryotic - replication of circular DNA