Plasma Membrane

Question 1

describe the fluid mosaic model of membranes

Answer 1

fluid-phospholipid bilayer where individual phospholipids can move
mosaic-intrinsic and extrinsic proteins embedded

Question 2

explain the role of cholesterol in membranes

Answer 2

connects phospholipids and reduces fluidity so more stable

Question 3

explain the role of glycoproteins in membranes

Answer 3

cell signalling and cell recognition

Question 4

explain the functions of extrinsic proteins in membranes

Answer 4

binding sites
bind cells together
involved in cell signalling

Question 5

explain the functions of intrinsic proteins in membranes

Answer 5

electron carriers
channel and carrier proteins

Question 6

explain the functions of membranes in cells

Answer 6

internal transport system
selectively permeable to regulate passage of molecules into organelles provide reaction surface
isolate organelles from cytoplasm

Question 7

name and explain factors that affect membrane permeability

Answer 7

temperature-high temperature denatures enzyme
phospholipid molecules have more kinetic energy and move further apart
pH-changes tertiary structure

Question 8

define osmosis

Answer 8

water diffuses across semi permeable membrane from an area of high concentration to an area of low concentration until equilibrium reached

Question 9

how does osmosis affect plant cells

Answer 9

water in-protoplast swells and become turgid
water out-protoplast shrinks and becomes flacid

Question 10

how does osmosis affect animal cells

Answer 10

water in-lysis
water out-crenation

Question 11

what is simple diffusion

Answer 11

passive process requiring no energy
net movement of small, lipid soluble molecules directly through bilayer down concentration gradient

Question 12

what is facilitated diffusion

Answer 12

passive process
specific channel or carrier proteins with complementary binding site transport large polar molecules down concentration gradient

Question 13

how do channel proteins work

Answer 13

hydrophilic channel binds to specific ions
one side opens and the other closes

Question 14

how do carrier proteins work

Answer 14

binds to complementary molecule
conformational change releases molecules on other side of membrane

Question 15

define active transport

Answer 15

transport of ions/molecules from an area of high concentration to an area of low concentration against a concentration gradient
using energy

Question 16

name 5 factors that affect rate of diffusion

Answer 16

temperature
diffusion distance
surface area
size of molecule
difference in concentration