Cell Membranes

Question 1

What do bilayered dynamic structures do

Answer 1

perform vital physiological roles
form boundaries between cells and their environments
regulate movement of molecules into and out of cells

Question 2

What does the lipid part of the fluid mosaic model fo

Answer 2

barrier for water soluble molecules
contain membrane proteins
carbs attach to lipid or protein molecules

Question 3

aqueous regions names

Answer 3

hydrophilic region (phosphate)
hydrophobic region (fatty acids)

Question 4

Integral membrane proteins

Answer 4

have hydrophobic
regions of amino acids that
penetrate or entirely cross
the phospholipid bilayer.

Question 5

Transmembrane proteins

Answer 5

have a specific orientation,
showing different “faces” on
the two sides of the
membrane

Question 6

Peripheral membrane proteins

Answer 6

lack hydrophobic regions and are not embedded in the bilayer

Question 7

Are proteins and lipids fixed

Answer 7

some can move around membrane

Question 8

when proteins and lipids move

Answer 8

two cells fuse
single continous memrbane forms around both cells and membrane proteins distrubute evenly around the membrane

Question 9

why are some proteins restricted in movement

Answer 9

-anchored to cytoskeleton
-trapped within regions of lipid = unequal distribution of proteins

Question 10

what happes when proteins are unequally dsitributed

Answer 10

allow for specialization of certain regions of the cell membrane

Question 11

describe how carbohydrates are composed in the membrane

Answer 11

cells have carbs on external surface
glycolipid
carb covalently bonded to protein = glycoprotein

Question 12

What do plasma membrane glycoproteins enable

Answer 12

cells to be recognized by other cells and proteins

Question 13

two types of binding between cells membranes

Answer 13

homotypic binding (same cell binds to eachother)
hetertypic binding

Question 14

what forms between cells in a tissue

Answer 14

specialized cell junctions

Question 15

three types of junctions

Answer 15

tight junctions
desmosomes
gap juncitons

Question 16

Tight junctions

Answer 16

plasma membrane
link adjacent epithelial cells
1. restrict migration of membrane proteins and phospholipids from one region of the cell to another
2. Prevent substances moving through intercellular space

Question 17

Desmosomes

Answer 17

-weld adjacent cells
-have dense plaques that attach to cytoplasmic fibres and membrane adhesion proteins
-membrane cell adhesion proteins bind to proteins of adjacent cell

Question 18

What are gap junctions

Answer 18

connections that facilitate communication between cells
made of connexons

Question 19

What are connexons

Answer 19

span plasma membrane of two adjacent cells
made of connexins that snap together to generate a pore

Question 20

faciliated diffusion is what

Answer 20

transport of polar molecules and ions in or out of the cell involving carrier and channel proteins

Question 21

diffusion passive definition

Answer 21

proces of random movement towards the state of equilibrium
net movement directional
greater conc to lower until ewquilibrium is reached

Question 22

what are diffusion rates determined b

Answer 22

temp, size of molecule, electrical charge of molecule and concentration gradient

Question 23

how is lipid bilayer affected by simple diffusion

Answer 23

more lipid soluble = more rapid diffusion
except water
polar and charged do not pass across lipid bilayer

Question 24

what is active transport

Answer 24

ions or molecules move against conc gradient across a membrane
requires atp

Question 25

three types of proteins for active transport

Answer 25

uniport symport antiport

Question 26

example of primary active transport

Answer 26

sodium potassium pumps only cations use

Question 27

wat are secondary active transport

Answer 27

uses atp to establish gradient uses gradient to move substances e.g. symport and antiport systems

Question 28

difference between secondary and primary

Answer 28

primary = release energy as ions down gradient secondary = against gradient

Question 29

what is endocytosis and examples

Answer 29

taking in molecules by a living cell by invagination of its membrane to form a vacuole phagocytosis pinocytosis receptor-mediated endocytosis`

Question 30

exocytosis

Answer 30

transports moecules out of cell from vesicles which fuse with membrane

Question 31

what are pinocytosis

Answer 31

vescile formation

Question 32

what are receptor mediated endocytosis

Answer 32

cells absorb SPECIFIC molecules by binding them to receptors on membrane

Question 33

where are receptor proteins

Answer 33

exposed on outside of cell in coated pits clathrin molecules form coat of the pits

Question 34

Membranes functions

Answer 34

information processing energy transformation = inner mitochondrial membrane converts energy of fuel to ATP, thylakoid of chloroplasts light energy

Question 35

how are membranes dynamic

Answer 35

participate in numerous cellular processes continually form, move and fuse segments of membrane moves, changes structures and fuses with other membranes each organelle modifies membrane to carry out specific functions dynamic structure and activity