The Membrane

Question 1

All membranes are

Answer 1

fluid mosaics

Question 2

All membranes have

Answer 2

phospholipids
proteins
carbohydrates
sterols (an exception)

Question 3

what are some factors that affect membrane fluidity?

Answer 3

-high temperatures can cause an increase the fluidity which can cause the membrane to be more permeable

low temperature can decrease fluidity and make the membrane more thick (this can make the cell stop moving leading to death of the cell)

Question 4

what are some factors that can affect membrane fluidity? (part 2)

Answer 4

-the type of phospholipid:

unsaturated fatty acids are more fluid because there double bonds allow them to be more flexible and movement

Question 5

say that the membrane has reached very low temperatures, what can the cell do to help the membrane with movement?

Answer 5

the cell will add more double bonds to the fatty acids and this is done with the help of the desaturase enzyme

Question 6

how can sterols help in maintaining optimal fluidity

Answer 6

in times of high temperature, sterols will decrease disruption by restraining the movement in membranes

in times of low temperatures, sterols will help prevent close packing of phospholipids

Question 7

integral proteins pass

Answer 7

through the lipid bilayer

Question 8

because integral proteins can pass through the entire lipid bilayer, what parts of the membrane can they both interact with?

Answer 8

hydrophobic regions & hydrophillic regions

Question 9

peripheral membrane proteins only attach to

Answer 9

the surface of the membrane but they can bind to phospholipids or integral proteins

Question 10

what carbohydrate is attached to integral membrane protein?

Answer 10

glycoproteins

Question 11

what carbohydrate is attached to phospholipid?

Answer 11

glycolipid

Question 12

what direction are glycoproteins and glycolipids facing?

Answer 12

carbohydrates always face outside of the cell (outside of the cytoplasm)

Question 13

what are the functions of these carbphydrates?

Answer 13

cell-cell recognition

ex: when we get sick, the body can recognize that it is a virus and start fighting the bad bacteria right away

Question 14

what causes membranes to be asymmetric ?

Answer 14

the lipid bilayer has different proteins and other components on one side and different components on the other side, causing an imbalance

Question 15

on the outside face of the membrane:

Answer 15

carbohydrates are attached to lipids and proteins
proteins anchor (attach) membrane to the extracellular matrix

Question 16

on the inside face of the membrane:

Answer 16

proteins anchor the membrane to the cytoskeleton

Question 16

on the inside face of the membrane:

Answer 16

proteins anchor the membrane to the cytoskeleton

Question 17

the tendency of molecules to move down a concentration gradient?

Answer 17

diffusion

Question 18

only small or non-polar molecules can move across the membrane

Answer 18

simple diffusion

Question 19

why is the lipid bilary permeable to small, non-polar molecules?

Answer 19

because the core of the phospholipid bilayer is non-polar so it likes to only interact with non-polar things

Question 20

can water pass through?

Answer 20

yes it can but its very difficult and is very slow

Question 21

large molecules cannot simply pass through the lipid billayer so what is required to help move them through?

Answer 21

membrane proteins help carry these large molecules through the bilayer

Question 22

diffusion of substances aided by membrane transport proteins

Answer 22

facilitated diffusion

Question 23

is energy required for this diffusion?

Answer 23

NO! because its moving from a concentration of high to low

Question 24

what are the type types of membrane proteins used to help these large molecules move through?

Answer 24

1. Channel proteins

2. Carrier proteins

Question 25

what do channel proteins do to move large molecules?

Answer 25

they form hydrophillic channels that allow specfific molecules to pass

ex: ions

Question 26

what do carrier proteins do to help?

Answer 26

carrier proteins will change the shape when large polar molecules bind to carry the across the membrane

ex: glucose transport

Question 27

what can’t and can cross the membrane ( osmosis)?

Answer 27

water can move through the membrane through osmosis , however the solutes cannot