lecture 10 cell membranes part 2

Question 1

cell membranes are described as a ____ ______ of lipids and proteins

Answer 1

fluid mosaic

Question 2

_____ are dispersed among lipids

Answer 2

proteins

Question 3

how do lipids and proteins move with the plane of the membrane

Answer 3

move back and forth, spin on axis, change positions

they DO NOT move up and down

Question 4

what is membrane fluidity determined by

Answer 4

the movement of phospholipids

Question 5

why do phospholipids move

Answer 5

because of van der waals forces that are weak and transient. they are constantly breaking and forming

Question 6

when does the flip flop between lipids

Answer 6

when new membrane is synthesized in presence of enzyme

Question 7

how does decrease in temperature impact membrane fluidity

Answer 7

it decreases

Question 8

how does increase in temperature impact membrane fluidity

Answer 8

increases

Question 9

what can happen to membrane if it is too fluid

Answer 9

melt - there are too few VDW forces to hold membrane together

Question 10

what happens when membrane is too cold

Answer 10

it has gelled or become viscous

Question 11

what do cells need to maintain a specific degree of fluidity

Answer 11

membranes

Question 12

what factors of membranes are effected by changes in membrane fluidity

Answer 12

membrane permeability and the functioning

Question 13

what type of organism can be most impacted by temperature

Answer 13

ectoterms

Question 14

what are ectotherms

Answer 14

organisms whose body temp is regulated bu their environment

Question 15

how do cells maintain proper membrane fluidity

Answer 15

-adjust degree of phospholipid tail saturatino
-adjust ohospholpid tail length

Question 16

what does cholesterol help with in membrane

Answer 16

helps to buffer the fluidity of membranes o there is less fluid change due to temperature changes

-decrease fluidity at higher temps
-increase fluidity at lower temps

Question 17

why is proper membrane fluidity important

Answer 17

-too fluid: membranes become leaky (deadly)
-too stiff: may slow or inhibit motion of integral proteins or may slow r prevent membrane fusion or budding

Question 18

what are vesicles important for

Answer 18

expression on cell surface

Question 19

integral proteins need to ______ _______ to do job

Answer 19

change shape

Question 20

what does bulk transport move

Answer 20

large molecules in and out of a cell and depends on membrane fusion or budding

Question 21

exocytosis

Answer 21

large molecules are secreted when a vesicle fuses with the plasma membrane

Question 22

endocytosis

Answer 22

large molecules are taken in when the plasma membrane pinches inward forming a vesicle

Question 23

active transport

Answer 23

transport of small molecules that requires energy and a transport protein

Question 24

passive transport

Answer 24

of small molecules, does not require energy, may involve transport proteins

Question 25

what are two characteristics of molecules that can slip between phospholipids to cross a membrane? What size do they have to be?

Answer 25

-uncharged -nonpolar -small

Question 26

example of molecule that can slip between phospholipids to cross a membrane?

Answer 26

-CO2 -O2 -N2 -steroid molecules

Question 27

example of molecules that cannot cross between phospholipids to cross a membrane?

Answer 27

-Na -glucose -ions -macromolecules -amino acids -nucleotides

Question 28

amino acids and nucleotides are

Answer 28

large uncharged polar molcules

Question 29

diffusion

Answer 29

movement of molecule from area of high concentration to area of low concentration

Question 30

what increases diffusion

Answer 30

temperature and larger concentration rate

Question 31

when is diffusion at equilibrium

Answer 31

when diffusion in each direction = each other

Question 32

facilitated diffusion uses _______ protein and ________ protein

Answer 32

carrier and channel

Question 33

is protein needed for simple diffusion

Answer 33

no protein