MEMBRANES L6

Question 1

membrane components

Answer 1

• primarily phospholipids

Question 2

bilayer formation

Answer 2

• forms spontaneously
• due to phospholipid shape and amphipathic nature
• held together by hydrophobic interactions - van Der Waals

Question 3

membrane proteins

Answer 3

• determine many membrane functions
• peripheral (surface) v. integral (imbedded)
• often transmembrane (go all the way through)

Question 4

Functions of membrane proteins

Answer 4

• transport
• enzymatic activity
• signal transduction
• cell to cell recognition
• intercellular joining
• attachment to something else (cytoskeleton, ECM)

Question 5

carbohydrates

Answer 5

• polysaccharides attached to protein (glycoprotein) or lipid (glycolipid)
• primarily cell identification

Question 6

fluid

Answer 6

• membrane components can move laterally within one layer of the membrane

Question 7

fluidity depends on:

Answer 7

• temperature
• chain length
• saturation
• cholesterol

Question 8

passive transport

Answer 8

• doesn’t use metabolic E (ATP)
• includes simple diffusion, osmosis, facilitated diffusion
• net movement down concentration gradient - no ATP required
• results in dynamic equilibrium

Question 9

diffusion

Answer 9

• tendency for molecules of a substance to fill available space
• all molecules in constant random motion, eventually evenly distributed in available space

Question 10

dynamic equilibrium

Answer 10

• no net movement at equilibrium

- different substances diffuse independently

Question 11

osmosis

Answer 11

• diffusion of water across a selectively permeable membrane
• direction of osmosis determined by difference in total solute concentration
• type of solute does not affect osmosis
• water diffuses from lower to higher solute concentration

Question 12

tonicity

Answer 12

• ability of a solution to cause a cell to gain or lose water

Question 13

isotonic solution

Answer 13

• solute concentration outside cell = solute concentration inside cell
• no net water movement

Question 14

hypertonic solution

Answer 14

• solute concentration outside > solute concentration inside

- cell loses water

Question 15

hypotonic solution

Answer 15

• solute concentration outside < solute concentration inside
• cell gains water

Question 16

facilitated diffusion

Answer 16

• passive transport through a transport protein
• does not require ATP
• specific
• 2 types: channel and carrier

Question 17

active transport

Answer 17

• requires ATP
• works against concentration gradient
• transport through carrier protein

Question 18

sodium potassium pump

Answer 18

• 3 Na out, 2 K in

- establishes electrical gradient

Question 19

bulk transport

Answer 19

• transport of a large number of molecules at once

- type of active transport, but not carrier protein

Question 20

exocytosis

Answer 20

• vesicle containing waste or secretory products fuses with plasma membrane
• releases contents from cell
• adds lipids to plasma membrane - primary mechanism for growing plasma membrane

Question 21

endocytosis

Answer 21

• material taken into cell by forming vesicles derived from plasma membrane

Question 22

phagocytosis

Answer 22

• “cellular eating”
• cell engulfs large particle
• fuses with primary lysosome
• particle digested

Question 23

pinocytosis

Answer 23

• “cellular drinking”
• ingestion of fluid and dissolved material
• forms vesicle, slowly transferred to cytoplasm
• non-specific

Question 24

receptor-mediated endocytosis

Answer 24

• receptor proteins in plasma membrane bind to specific macromolecules outside cell
• form coated pits
• fold inward to form vesicles
• main mechanism for uptake of macromolecules