Lecture 3- The Cell Membrane

Question 1

what are the 4 functions of cell membranes?

Answer 1

physical barrier
gateway for exchange
communication
cell structure

Question 2

how does the cell membrane communicate?

Answer 2

the cell membrane has receptors that detect physical and chemical stimuli and cascades responses to stimuli

Question 3

what is the cell membrane made out of? (2)

Answer 3

protein and lipid

Question 4

ratio of protein to lipid is different for different cell types, so what does it mean if a membrane has lots of protein?

Answer 4

very metabolically active

Question 5

why is the cell membrane called a fluid mosaic?

Answer 5

proteins are afloat on a sea of lipid
some are anchored and held in place by the cytoskeleton
but everything is still floating regardless

Question 6

what are 4 examples of lipids?

Answer 6

glycolipids
phospholipids
cholesterol
sphingolipids

Question 7

what are 4 examples of proteins?

Answer 7

integral
peripheral
cytoskeletal
extracellular matrix

Question 8

what is the cell membrane mostly made of?

Answer 8

phospholipids with cholesterol wedged between the tails of each

Question 9

how many different phospholipids are there?

Answer 9

4

Question 10

how are there so many different types of phospholipids? what makes each different?

Answer 10

the different varieties of R- groups

Question 11

why is cholesterol wedged between phospholipid tails? 3

Answer 11

regulates membrane fluidity
slows diffusion of molecules across the membrane
helps the cell membrane to keep its shape

Question 12

what is the visual difference between phospholipids and sphingolipids?

Answer 12

sphingolipids have longer tails because they have sphingosine instead of glycerol

Question 13

when sphingolipids aggregate together, what is that called?

Answer 13

lipid rafts

Question 14

what are 2 unique things about lipid rafts?

Answer 14

have a high density of cholesterol
some proteins only associate with lipid rafts which leads to areas of specialization on cell membranes

Question 15

what can errors in lipid rafts cause?

Answer 15

plays a role in diseases

Question 16

what are 3 types of integral proteins?

Answer 16

polytopic
bitopic
monotopic

Question 17

characteristics of polytopic integral protein

Answer 17

transmembrane
spans over the cell membrane more than once

Question 18

characteristics of bitopic integral protein

Answer 18

transmembrane
spans over the cell membrane once

Question 19

characteristics of monotopic integral membrane

Answer 19

attached to one side of the membrane

Question 20

what is a peripheral protein?

Answer 20

attached to one side of membrane by non- covalent interactions; weak

Question 21

are integral proteins attached permanently to the cell membrane?

Answer 21

YES

Question 22

how are monotopic integral proteins permanently attached to the cell membrane from one side? 3

Answer 22

have strong hydrophobic sections (allow it to tightly associate with the lipid portion of bilayer)
addition of a fatty acid anchors monotropic protein to the membrane
electrostatic or ionic interaction between protein and phospholipid tightly bind monotropic protein to the membrane

Question 23

why do peripheral proteins not bond super tight?

Answer 23

associate non- covalently with integral proteins and polar heads of phospholipids

Question 24

where is the cytoskeleton located in the cell?

Answer 24

cytoplasm (therefore not a membrane protein)

Question 25

what does the cytoskeleton often interact with?

Answer 25

membrane proteins (just isnt apart of the membrane)

Question 26

extracellular matrix has variable glycosylation, what does it do in the matrix? 4

Answer 26

play crucial role in cell recognition, adhesion, migration and proliferation

Question 27

what connects the cytoskeleton and the extracellular matrix together? where is this link located?

Answer 27

dystrophin located on x chromosome

Question 28

what is the main goal of dystrophin?

Answer 28

keeps the integrity of the muscle cell membrane

Question 29

what is muscular dystrophy?

Answer 29

when the dystrophin link is missing

Question 30

in severe cases what can muscular dystrophy lead to?

Answer 30

causes muscles to waste away

Question 31

why is it normally boys that get MD? (normally around age 2 or 3)

Answer 31

because they only have one X chromosome girls have two X chromosomes so they would have to get the disease from both mom AND dad. whereas, boys only need to get the genetic disorder from mom

Question 32

what is the closest approach to curing MD?

Answer 32

utrophin approach

Question 33

what is the utrophin approach?

Answer 33

utrophin is a natural protein made in the body that is closely related with dystrophin with 80% of their amino acids in common. a drug needs to be found to entice muscles to overproduce utrophin

Question 34

what is the gene therapy approach?

Answer 34

researchers have found a way to make a small version of dystrophin and put it into a virus, but injection of this virus has revered the progression of MD :(

Question 35

what is the cell transplant approach?

Answer 35

injecting dystrophin from healthy donors into MD patients

Question 36

what is the anti- myostatin approach?

Answer 36

myostatin normally inhibits skeletal muscle growth, so they are working on ways to inhibit this inhibitor in patients with MD, thereby stimulating muscle growth