Chapter 7: Membrane Structure and Function Flashcards
Part II (21 cards)
What cell structure helps maintain water balance?
Cell walls
Plasmolysis
When the membrane pulls away from the cell wall and the plant wilts because cell is immersed in hypertonic environment
Turgid
Plant cell is immersed in a hypotonic solution (i.e. rainwater) , the relatively inelastic cell wall will expand only so much before it exerts a back pressure on the cell that opposes further water uptake. At this point, the cell is very firm, the healthy state for most plant cells.
Flaccid
if a plant’s cells and surroundings are isotonic, there is no net tendency for water to enter and the cell becomes limp
What is facilitated diffusion?
Polar molecules and ions impeded by the lipid bilayer of the membrane diffuse passively with the help of transport proteins
What transport proteins are involved in facilitated diffusion?
i. Channel proteins
ii. Carrier proteins
What are some examples of carrier proteins?
carrier protein in the plasma membrane of red blood cells transports glucose across the membrane (glucose transporter)
Carrier proteins undergo a subtle change in shape that translocates (moves) the solute-binding site across the membrane. What can trigger the change in shape?
Binding and releasing of the transported molecule
Active Transport
requires energy to move substances against their concentration gradient
Sodium Potassium Pump
A transport (carrier) protein in the plasma membrane of an animal cell that actively transports sodium out of the cells and potassium into cell energized by transfer of phosphate from the hydrolysis of ATP
What is membrane potential?
a. The difference in electrical charge (voltage) across a cell’s plasma membrane due to the unequal distribution of anions and cations on the two sides of membrane.
What is the electrochemical gradient?
a. The diffusion gradient of an ion, which is affected by both the concentration difference of an ion across a membrane (a chemical force) and the ion’s tendency to move relative to the membrane potential (an electrical force)
What are the two combined forces that make up the electrochemical gradient?
a. Chemical force (the ion’s concentration gradient)
b. Electrical force (the effect of the membrane potential on the ion’s movement)
What is an electrogenic pump?
A transport protein that generates voltage across a membrane;
What is an example of a electrogenic pump?
Sodium potassium pump (generates a net positive from cytoplasm to extracellular fluid/inside negative & outside positive = voltage)
What is a proton pump?
The main electrogenic pump of plants, fungi and bacteria, which actively transports protons (hydrogen ions) out of cell
What is cotransport?
A transport protein (cotransporter) can couple the “downhill” diffusion of the solute to the “uphill” transport of a second substance against its own concentration gradient
What are the differences between exocytosis and endocytosis?
a. Exocytosis secretes molecules and endocytosis takes in molecules
b. Water and small solutes enter and leave the cell by diffusing through the lipid bilayer of the plasma membrane or by transport proteins. Large molecules generally cross the membrane in bulk, packaged in vesicles
Phagocytosis
cell engulfs particle
Pinocytosis
gulps droplets of extracellular fluid into tiny vesicles
Receptor mediated endocytosis
the movement of specific molecules into a cell by the infolding of vesicles containing proteins with receptor sites specific to- the molecules being taken in; enables a cell to acquire bulk quantities of specific substances
