AQA Biology AS Past Paper Questions, Exams of Advanced Education

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AQA Biology AS Past Paper

Questions

water will affect the mass, only a measure of the water taken up or lost only is needed. - before reweighing, the student blotted dry the outside of each cylinder. explain why. to add phosphate to other substances and make them more reactive. to provide energy for other reactants. - give two ways in which the hydrolysis of ATP is used in cells. dissolve the piece of food in alcohol. then add water. white emulsion shows the presence of lipid. - Describe how you would test a piece of food for the presence of lipid. Glycerol - The figure below shows a phospholipid. The part of the phospholipid labelled A is formed from a particular molecule. Name this molecule. Ester - Name the type of bond between A and fatty acid X. Y because it contains a double bond between adjacent carbon atoms in hydrocarbon chain. - Which of the fatty acids, X or Y, in the figure above is unsaturated? Explain your answer. divide the mass of each lipid by the total mass of all the lipids in that type of cell. multiply answer by 100. - Scientists investigated the percentages of different types of lipid in plasma membranes from different types of cell. The table shows some of their results. The scientists expressed their results as Percentage of lipid in plasma membrane by mass. Explain how they would find these values. red blood cells are free to move in blood, they are not supported by other cells so cholesterol helps to maintain the shape. - Cholesterol increases the stability of plasma membranes. Cholesterol does this by making membranes less flexible.

Suggest one advantage of the different percentage of cholesterol in red blood cells compared with cells lining the ileum. Pushing down hard spreads the tissue. Not pushing sideways prevents the chromosomes from breaking. - A student investigated mitosis in the tissue from an onion root tip. The student prepared a temporary mount of the onion tissue on a glass slide. She covered the tissue with a cover slip. She was then given the following instructions. "PUSH DOWN HARD ON THE COVER SLIP, BUT DO NOT PUSH THE COVER SLIP SIDEWAYS". Explain why she was given this instruction. they are resynthesised from ADP and phosphate by ATP synthase during respiration. - Cells constantly hydrolyse ATP to provide energy. Describe how ATP is resynthesised in cells. the complementary strand of HIV DNA is made through complementary nucleotides. DNA polymerase helps nucleotides join together to form a new strand. - When HIV infects a human cell, the following events occur. A single-stranded length of HIV DNA is made. The human cell then makes a complementary strand to the HIV DNA. The complementary strand is made in the same way as a new complementary strand is made during semi-conservative replication of human DNA. Describe how the complementary strand of HIV DNA is made. It was important because there are fewer layers of cells so that light can pass through. - A student found the number of stomata per cm2 on the lower surface of a daffodil leaf. He removed a small, thin piece of lower epidermis and mounted it on a microscope slide. He examined the slide using an optical microscope. Explain why it was important that the piece of the epidermis that the student removed was thin.

they are made through using a thin slice. put on slide in water stain before adding a cover slip. - A scientist examined the structure of mustard plant leaves. He viewed temporary mounts of leaf tissues with an optical microscope. The figure below shows a drawing of typical results. Describe how temporary mounts are made. bacteria are destroyed by phagocytes when a phagocyte engulfs to form a vacuole. then lysosome empties contents into vacuole. thus, releasing enzymes that digest bacteria. - describe how bacteria are destroyed by phagocytes. a bacterial cell has a cell wall and a mesosome. - Give two structures a bacterial cell may have that a white blood cell does not have. the mean number of chloroplasts in mesophyll cells of a leaf can be determined through selecting a large number of cells before counting up the number of chloroplasts and finally dividing the number of chloroplasts by the number of cells. - Describe how the scientist could have used the temporary mounts of leaves to determine the mean number of chloroplasts in mesophyll cells of a leaf.