4. Cell membranes and transport
A section of Biology, 9700
Listing 10 of 418 questions
The cells in the roots of beetroot plants contain a red pigment. When pieces of root tissue are soaked in cold water, some of the red pigment leaks out of the cells into the water. An experiment was carried out to investigate the effect of temperature on the loss of red pigment from the root cells. It was found that the higher the temperature of the water, the higher the rate of loss of red pigment from the root cells. Which of these statements could explain this trend?
9700_m17_qp_12
MCQ
2017
Paper 1, Variant 2
View
is a transmission electron micrograph of a plant parenchyma cell. X Y tonoplast cytosol (fluid part of cytoplasm) cell sap in vacuole The external environment of the parenchyma cell has a higher water potential than the internal environment of the cell. One function of parenchyma cells is to provide support to the plant. With reference to , suggest how parenchyma cells provide support to the plant. The image shown in is at a higher magnification than can be obtained using a typical light microscope. Explain what is meant by the term magnification. The actual diameter of the parenchyma cell in along the line X—Y is 35 µm. Calculate the magnification of the image. magnification = × The cell sap in the vacuole of the cell shown in has a pH of 5.0. The cytosol has a pH of 7.2. The tonoplast controls the passage of hydrogen ions from the cytosol into the vacuole. The low pH created by the entry of hydrogen ions is optimum for the action of acid hydrolase enzymes in the vacuole. Acid hydrolase enzymes are also found in lysosomes in animal cells. Suggest which transport mechanism is used to move hydrogen ions from the cytosol of the parenchyma cell into the vacuole. Explain your choice. transport mechanism explanation Suggest how the structure of the tonoplast allows hydrogen ions to be transported into the vacuole, but does not allow the ions to leave the vacuole. The acid hydrolases in the vacuole cannot function in neutral conditions (pH 7.0) or alkaline conditions. Explain the advantage to the plant cell of having acid hydrolases that cannot function in neutral, near neutral or alkaline conditions.
9700_m20_qp_22
THEORY
2020
Paper 2, Variant 2
View
is a drawing of a transverse section of a leaf. Use label lines and the letters X, S, E and D to indicate the following on : X – a xylem vessel S – a phloem sieve tube E – a lower epidermal cell D – a palisade mesophyll cell Calculate the magnification of . Show your working and express your answer to the nearest whole number. Answer 0.5 mm Use [T Name two assimilates that move from the palisade mesophyll cells to the vascular tissue to be exported from the leaf. Explain, using the term water potential, how water moves from the vascular tissue to the atmosphere.
9700_s05_qp_2
THEORY
2005
Paper 2, Variant 0
View
Questions Discovered
418