Practise IB Biology HL B2.1 with membrane diagrams and data questions covering selective permeability, transport mechanisms, fluidity, vesicles and ion pumps.
Outline how the amphipathic properties of phospholipids play a role in membrane structure.
State the role of cholesterol in animal cell membranes.
Neural pathways in living brains can now be mapped by tracking the movement of water molecules inside axons. What keeps water molecules inside axons?
Plasma membrane
Hydrogen bonding
Pump proteins
Synapse
Which process results in the exchange of gases across the membrane of pneumocytes?
Active transport
Simple diffusion
Facilitated diffusion
Mass flow
Outline how the amphipathic properties of phospholipids play a role in membrane structure.
Oxygen is needed to complete aerobic cell respiration.
Outline four different functions of membrane proteins.
In the early 1990s, investigations involving egg cells from the African clawed frog (Xenopus laevis) led to the discovery of membrane channel proteins called aquaporins.
In one investigation, scientists injected 10 frog egg cells with a solution containing mRNA encoding for an aquaporin, and another 10 frog egg cells with distilled water (control cells). All the frog egg cells were then incubated in a hypotonic solution. The volume of the frog egg cells was then measured during a period of five minutes.
The graph shows the mean results of the investigation.
State the direction of net movement of water across the plasma membrane of all the frog egg cells between 0 and 3 minutes.
Explain the reasons for the different results obtained for the frog egg cells with aquaporin mRNA and the control frog egg cells.
The diagram shows protein channels involved in the passive movement of a substance into the cell across the cell membrane.
What describes this movement?
Energy of ATP is used to transport substances into the cell.
Substances can move from areas of low to areas of high concentration.
The proteins ensure that movement of substances is only in one direction.
Net movement occurs until the concentrations in and out of the cell are equal.
Calcium is absorbed from food in the human gut by both active and passive processes. Outline active transport, including the benefits of the process.
Cells use a variety of methods to move particles across membranes. What is a similarity between facilitated diffusion and active transport?
Both are carried out by proteins in the membrane.
Both move particles against the concentration gradient.
Both use ATP.
Both move non-polar ions across the membrane.
The diagram shows the cross section of a plasma membrane.
What is found in area X ?
Glycolipid
Glycoprotein
Polar amino acid
Non-polar amino acid
Draw a labelled diagram to show the fluid mosaic model of the plasma membrane.
Voltage-gated ion channels are proteins that are embedded in the phospholipid bilayer of plasma membranes. They conduct ions at high rates, regulated by the voltage across the membrane. The diagram shows a typical voltage-gated potassium ( ) channel when it is closed and when it is open.
Outline the effect of fatty acids on the fluidity of membranes.
State the role of cholesterol in animal cell membranes.
Cholinergic synapses use acetylcholine as their neurotransmitter. They are widespread in the body, passing on signals to muscle cells. These synapses are affected by neonicotinoid pesticides.
The diagrams, which are not drawn to scale, show the synapse between two neurons and a detail of the synaptic cleft.
On the diagrams, label:
On the diagrams, label with a letter E a vesicle involved in exocytosis.
Voltage-gated ion channels are proteins that are embedded in the phospholipid bilayer of plasma membranes. They conduct ions at high rates, regulated by the voltage across the membrane. The diagram shows a typical voltage-gated potassium ( ) channel when it is closed and when it is open.
Explain the action of the voltage-gated potassium channel during a nerve impulse.
State another type of gated ion channel.
Hypertension (blood pressure exceeding 140 mmHg ) affects millions of people worldwide. Many modern societies consume more sodium in the form of salt (NaCl) than is required for normal physiology. The effect of changing the levels of dietary sodium has been studied in various organisms.
Scientists recorded the blood pressure changes in chimpanzees (Pan troglodytes) fed a diet without added sodium (control) or a sodium supplemented diet (experimental) as follows
- 5 grams of salt per day from December 1991 until May 1992
- 10 grams of salt per day until June 1992
- 15 grams of salt per day until August 1993
after which no more salt was added to the diet until the experiment ended.
Suggest how sodium-potassium pumps in the membranes of nephron cells in the kidney could allow blood sodium concentrations to be reduced, if there is sufficient potassium in the diet.
What transport method is used in the reabsorption of glucose in the proximal convoluted tubule of the kidney?
Diffusion
Osmosis
Endocytosis
Active transport