cell membrane structure and transport exam questions Flashcards
give two similarities in the movement of substances by diffusion and osmosis (2)
-movement down a concentration gradient from an area of high to low conc
-passive processes that no not require energy from ATP
Putting bee honey on a cut kills bacteria. Honey contains a high concentration of sugar.
Suggest how putting honey on a cut kills bacteria (3)
-water potential in honey is lower than in bacterial cells
-water leaves bacterial cells by osmosis
-loss of water stops metabolic reactions which causes the bacterial cells to die
use your knowledge of water potential to suggest how watering plants with sodium chloride solution affects fresh mass (3)
-water potential inside tomato plant become higher
-water drawn out of tomato plants
-by osmosis
-most of the fresh mass is mass by water so mass decreases
Name and describe five ways substances can move across the cell-surface membrane into a cell. (5)
-simple diffusion of small/ non-polar molecules down a concentration gradient
-facilitated diffusion of larger/ polar molecules down a concentration gradient via carrier or channel proteins
-osmosis of water down a water potential gradient across a partially permeable membrane
-active transport against a concentration gradient using a carrier protein and energy from ATP
-co transport of two different substances using a carrier protein
explain the function of the enzyme ATP hydrolase in the membrane (2)
catalyses hydrolysis of ATP to ADP and Pi which releases energy to be used in active transport movement of substances against the concentration gradient
The movement of substances across cell membranes is affected by membrane structure. Describe how. (5)
-phospholipid bilayer allows movement/ diffusion of non-polar/ lipid substances
-phospholipid bilayer prevents movement/ diffusion of polar/ non-lipid soluble substances OR proteins allow polar/ non-lipid soluble substances to cross the membrane
-carrier proteins allow active transport
-channel/ carrier proteins allow facilitated diffusion
-shape of channel/ carrier determines which substances can move
-number of channels/ carriers and SA of the membrane determines how much transport can occur
-cholesterol affects fluidity
A scientist measured the rate of uptake of a monoglyceride and a monosaccharide by epithelial cells of the small intestine of mice. A monoglyceride is a molecule of glycerol with one fatty acid attached. She did this
for different concentrations of the monoglyceride and monosaccharide.
Explain the of the curve for the uptake of monosaccharides between A and B and C and D. (3)
-movement through carrier proteins via facilitated diffusion
-between A and B the rate of uptake is proportional to external concentration
-between C and D, all carrier proteins are in use/ saturated so rate levels off
Suggest how the graph is evidence for monoglycerides being lipid soluble molecules(2)
-rate of uptake is proportional/ does not level off (so diffusion occurring)
-only lipid soluble molecules can diffuse through the phospholipid bilayer
Suggest and explain two ways the cell-surface membranes of the cells lining the uterus may be adapted to allow rapid transport of nutrients. (2)
-membrane highly folded so large SA for increased rate of facilitated diff/ active transport
-large numbers of protein carriers for active transport and facilitated diffusion
Sodium ions from salt (sodium chloride) are absorbed by cells lining the gut. Some of these cells have membranes with a carrier protein called NHE3.
NHE3 actively transports one sodium ion into the cell in exchange for one
proton (hydrogen ion) out of the cell.
Use your knowledge of transport across cell membranes to suggest how
NHE3 does this. (3)
-co transport
-uses hydrolysis of ATP
-sodium ion and proton bind to the protein
-protein changes shape to transport across cell membrane
High absorption of salt from the diet can result in a higher than normal concentration of salt in the blood plasma entering capillaries. This can lead
to a build-up of tissue fluid.
Explain how. (2)
-higher salt results in lower water potential of tissue fluid
-so less water returns to capillary via osmosis which causes build up of tissue fluid
