Chapter 11

Question 1

what is plasma membrane and two functions

Answer 1

selective barrier separating cell contents from exterior

functions
-recognition
-import/export of small molecules

Question 2

prokaryotes have ___ plasma membrane while eukaryotes have ___

Answer 2

one while euk have many

Question 3

plasma membrane approx thickness

Answer 3

5-10 nm thick

Question 4

what is special about nuclear and mitochondrial membranes

Answer 4

contain their own unique DNA

Question 5

if you place pure phospholipids in water ______ are formed

Answer 5

liposomes

Question 6

a bilayer of ____ forms the backbone of the plasma membrane and which types and most abundant

Answer 6

lipids

types:
- phospholipids (most abundant)
- cholesterol
- glycolipids

Question 7

3 key components of cell membrane

Answer 7

-lipids
-proteins
-carbohydrates

Question 8

fluid mosaic model

Answer 8

singer and nicolson (1972)
-proposed membranes were not rigid/composed of a lipid bilayer where proteins are embedded and float freely

Question 9

what is the phospholipids structure

Answer 9

• a glycerol molecule
• two fatty acid tails (hydrocarbon chains) with COOH at end
• phosphate group
• polar group (choline polar group)

Question 10

how long are fatty acid tails in human cells

Answer 10

typically 18-20 carbons

Question 11

in the phospholipid structure describe the heads vs tails

Answer 11

heads - hydrophilic (polar)
tails - hydrophobic (non-polar)

Question 12

what is amphipathic

Answer 12

has both hydrophilic and hydrophobic parts

Question 13

what are the two categories of proteins found in membranes

Answer 13

integral and peripheral

(integral are integrated in membrane)

Question 14

membranes are _____ and they do what ? what kind of diffusion?

Answer 14

fluid

they move, vibrate, spin, and exchange places within bilayer

lateral diffusion

Question 15

how are membranes fluid

Answer 15

the phospholipids are NOT held together by covalent bonds, rather weaker HYDROPHOBIC INTERACTIONS stabilize them which allows movement

Question 16

is it common for phospholipids to naturally flip from one side to the other?

Answer 16

no it’s very rare

Question 17

proteins and phospholipids are constantly _____

Answer 17

moving

Question 18

3 factors that affect membrane fluidity

Answer 18

1. temperature
2. fatty acid tail composition (saturation & length)
3. cholesterol content

Question 19

how does temperature affect membrane fluidity

Answer 19

↑ temperature = ↑ membrane fluidity (membrane becomes leaky)

↓temperature = ↓ fluidity (becomes gel like)

Question 20

how does fatty acid tail saturation affect membrane fluidity

Answer 20

↑saturation = ↓ fluidity

Question 21

unsaturated vs saturated

Answer 21

unsaturated = fluid
- double bonds cause tails to have kinks

saturated = not fluid (viscous)
- phospholipids packed tightly together

Question 22

how does fatty acid tail length affect membrane fluidity

Answer 22

↑length = ↓fluidity

Question 23

what enzyme can add double bonds to fatty acid tails (turn saturated into unsaturated)

Answer 23

desaturase

Question 24

when temp is high you want to ____ saturation

Answer 24

increase

Question 25

when temp is low you want to ____ saturation

Answer 25

decrease

Question 26

which tail length is good for low vs high temps

Answer 26

low temps = want shorter chains (↑fluidity) high temps = want longer chains (↓fluidity)

Question 27

what does cholesterol do for the membrane

Answer 27

acts as a buffer & helps maintain constant fluidity (animal cells)

Question 28

how does cholesterol affect membrane fluidity

Answer 28

- STIFFENS bilayer present at high temps to avoid being too fluid as -PREVENTS TIGHT PACKING of phospholipids avoids crystallization at low temps

Question 29

cell membrane is ___ symmetrical and this means what

Answer 29

NOT - each monolayer has a distinct set of phospholipids and proteins (particularly important for proteins)

Question 30

glycolipids only found on ____ side

Answer 30

ECF (extracellular fluid)

Question 31

phosphatidylcholine mainly found on ___ side

Answer 31

ECF side

Question 32

phosphatidylinositols are involved in ___ and pases signals on ___ side

Answer 32

cell signalling and passes signals on cytosolic side

Question 33

cholesterol molecules distributed on ____ leaflets

Answer 33

both

Question 34

scramblases

Answer 34

randomly moves phospholipids from one side to another - work in the ER

Question 35

how does asymmetry of the membrane result?

Answer 35

flippases = select specific phospholipids and move them to the appropriate bilayer

Question 36

membranes are synthesized in the ____

Answer 36

E.R

Question 37

lumen side will become the ____ monolayer while cytosolic side will ___

Answer 37

lumen - becomes exterior cytosolic - remain facing cytosol

Question 38

how are membranes a mosaic model ?

Answer 38

lipids - backbone proteins - determine function

Question 39

4 categories of membrane proteins

Answer 39

1. transmembrane 2. monolayer associated alpha helix 3. lipid linked 4. protein attached peripheral

Question 40

what are transmembrane proteins (3)

Answer 40

- non polar/ hydrophobic - in the membrane - alpha helix shape to maximize number of hydrogen bonds

Question 41

describe hydrophobic vs hydrophilic in transmembrane protein beta barrel porins

Answer 41

- hydrophilic AA line the inside of the barrel (allow water to pass thru) -hydrophobic AA face the fatty acid tails

Question 42

alpha helices are _____

Answer 42

amphipathic

Question 43

describe monolayer associated alpha helix (2)

Answer 43

- almost entirely on cytosolic side - anchored by an amphipathic alpha helix

Question 44

describe lipid linked proteins (3)

Answer 44

- found outside of bilayer - secured thru one or more covalent attachments to phospholipids - on either side of the membrane

Question 45

describe protein attached peripheral proteins (3)

Answer 45

- attached to other membrane proteins - can be on either side - DONT need a detergent to remove

Question 46

describe cell membrane cortex

Answer 46

- meshwork of fibrous proteins attached to transmembrane proteins that adds strength and support to plasma membrane

Question 47

in vivo cells ____ movement of proteins

Answer 47

restrict

Question 48

describe glycocalyx (3)

Answer 48

-exterior sugar coating of plasma membrane - on lumen side - helps with cell recognition & protection from mechanical damage

Question 49

glycolipid vs glycoprotein vs proteoglycans

Answer 49

(all included in glycocalyx) lipid - carbohydrate attached lipid protein - carbohydrate attached protein proteoglycans -sub category of glycoprotein (help protect)

Question 50

what is glycosylation

Answer 50

attachment of carbohydrate to the backbone of a protein