A-Level Biology - Ocr |251 Questions| With Correct Answers.

What is a scanning electron microscope used for? {Ans: Viewing the surface of objets under high magnification and resolution}Most bony fish have 5 pairs of gills which are covered by a bony flap, known as the ...? What is the function of this bony flap? {Ans: Operculum; protects the gills and ensures a constant flow of water}Describe how water moves up the stem via the transpiration pull {Ans: Loss of water by evaporation at the top of the plant must be replaced by water from the xylem. This puts water at the top of xylem under tension. Tension pulls the column of water up the xylem as water molecules are cohesive.}What is the purpose of intercalated discs between adjacent muscle cells? {Ans: Ensures an even, synchronised contraction}The distance moved by the meniscus in a potometer is 45mm in 5 minutes. The radius of the capillary tube is 0.5 mm. Calculate the rate of transpiration. {Ans: 7.1mm3/min}Describe the role of ATP in bulk transport {Ans: ATP is required to provide energy for the movement of vesicles along microtubules of cytoskeleton (via motor proteins); ATP is needed to fuse vesicle membrane and plasma membrane together (PM