EduNinja• Describe active transport as the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration (i.e. against a concentration gradient), using energy from respiration
Fig. 1.1 shows several villi from the ileum, which is part of the small intestine.
Fig. 1.2 shows the tip of a villus in more detail.
Fig. 1.2
The epithelial cells of the villi absorb nutrients by diffusion and active transport.
Describe how active transport differs from diffusion.
Some examples of substances moving across membranes are listed.
1 glucose molecules into the epithelium that lines the small intestine
2 nitrate ions from a dilute solution in soil into a more concentrated solution in root hair cells
3 water molecules from mesophyll cells into the air spaces of a leaf
For which examples must oxygen be present?
1, 2 and 3
1 and 2 only
1 and 3 only
2 and 3 only
Which is an example of active transport?
carbon dioxide entering a leaf
ion uptake by root hair cells
oxygen moving from the alveoli into the blood
water uptake by root hair cells
Which process is involved in the uptake of glucose by the epithelial cells of kidney tubules?
active transport
diffusion
osmosis
transpiration
Which statement describes active transport?
the movement of ions through proteins in a cell membrane, releasing energy
the movement of ions through proteins in a cell membrane, using energy
the movement of water through lipids in a cell membrane, releasing energy
the movement of water through lipids in a cell membrane, using energy
Which statement about diffusion is correct?
The process requires energy from respiration.
The particles must cross a cell membrane.
The net movement of particles is up a concentration gradient.
The process involves the random movement of particles.
The graph shows the rate of uptake of magnesium ions by two similar plants, X and Y .
The roots of each plant were placed in a range of solutions. Each solution contained a different concentration of magnesium ions. All other conditions were kept constant.
What is a possible explanation for the difference in the results for the two plants?
Plant Y has fewer protein carriers for magnesium ions in its cell membranes.
Plant Y has a higher rate of respiration.
Plant Y has more root hair cells.
The root hair cells in plant Y have a lower water potential.
The diagram shows the movement of glucose molecules across a cell membrane.
Which statement describes molecule T?
It is a fat molecule used to transport glucose down a concentration gradient.
It is a fat molecule used to transport glucose against a concentration gradient.
It is a protein molecule used to transport glucose down a concentration gradient.
It is a protein molecule used to transport glucose against a concentration gradient.
The graph shows the results of an investigation into the effect of oxygen on the uptake of glucose by cells.
Which conclusion can be made about these data?
Glucose only enters the cells by active transport.
Glucose only enters the cells by diffusion.
Glucose enters the cells by both active transport and diffusion.
Glucose enters the cells by osmosis.
Which process requires energy from respiration?
active transport
diffusion
osmosis
transpiration