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BIOL 2202 CMBean Midterm 2 > Chapter 11 > Flashcards

Chapter 11 Flashcards

1
Q

what is plasma membrane and two functions

A

selective barrier separating cell contents from exterior

functions
-recognition
-import/export of small molecules

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2
Q

prokaryotes have ___ plasma membrane while eukaryotes have ___

A

one while euk have many

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3
Q

plasma membrane approx thickness

A

5-10 nm thick

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4
Q

what is special about nuclear and mitochondrial membranes

A

contain their own unique DNA

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5
Q

if you place pure phospholipids in water ______ are formed

A

liposomes

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6
Q

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

A

lipids

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

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7
Q

3 key components of cell membrane

A

-lipids
-proteins
-carbohydrates

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8
Q

fluid mosaic model

A

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

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9
Q

what is the phospholipids structure

A
  • a glycerol molecule
  • two fatty acid tails (hydrocarbon chains) with COOH at end
  • phosphate group
  • polar group (choline polar group)
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10
Q

how long are fatty acid tails in human cells

A

typically 18-20 carbons

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11
Q

in the phospholipid structure describe the heads vs tails

A

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

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12
Q

what is amphipathic

A

has both hydrophilic and hydrophobic parts

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13
Q

what are the two categories of proteins found in membranes

A

integral and peripheral

(integral are integrated in membrane)

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14
Q

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

A

fluid

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

lateral diffusion

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15
Q

how are membranes fluid

A

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

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16
Q

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

A

no it’s very rare

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17
Q

proteins and phospholipids are constantly _____

A

moving

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18
Q

3 factors that affect membrane fluidity

A
  1. temperature
  2. fatty acid tail composition (saturation & length)
  3. cholesterol content
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19
Q

how does temperature affect membrane fluidity

A

↑ temperature = ↑ membrane fluidity (membrane becomes leaky)

↓temperature = ↓ fluidity (becomes gel like)

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20
Q

how does fatty acid tail saturation affect membrane fluidity

A

↑saturation = ↓ fluidity

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21
Q

unsaturated vs saturated

A

unsaturated = fluid
- double bonds cause tails to have kinks

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

22
Q

how does fatty acid tail length affect membrane fluidity

A

↑length = ↓fluidity

23
Q

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

A

desaturase

24
Q

when temp is high you want to ____ saturation

A

increase

25
Q

when temp is low you want to ____ saturation

A

decrease

26
Q

which tail length is good for low vs high temps

A

low temps = want shorter chains (↑fluidity)

high temps = want longer chains (↓fluidity)

27
Q

what does cholesterol do for the membrane

A

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

28
Q

how does cholesterol affect membrane fluidity

A
  • STIFFENS bilayer
    present at high temps to avoid being too fluid as

-PREVENTS TIGHT PACKING of phospholipids
avoids crystallization at low temps

29
Q

cell membrane is ___ symmetrical and this means what

A

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

30
Q

glycolipids only found on ____ side

A

ECF (extracellular fluid)

31
Q

phosphatidylcholine mainly found on ___ side

A

ECF side

32
Q

phosphatidylinositols are involved in ___ and pases signals on ___ side

A

cell signalling and passes signals on cytosolic side

33
Q

cholesterol molecules distributed on ____ leaflets

A

both

34
Q

scramblases

A

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

35
Q

how does asymmetry of the membrane result?

A

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

36
Q

membranes are synthesized in the ____

A

E.R

37
Q

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

A

lumen - becomes exterior
cytosolic - remain facing cytosol

38
Q

how are membranes a mosaic model ?

A

lipids - backbone
proteins - determine function

39
Q

4 categories of membrane proteins

A
  1. transmembrane
  2. monolayer associated alpha helix
  3. lipid linked
  4. protein attached peripheral
40
Q

what are transmembrane proteins (3)

A
  • non polar/ hydrophobic
  • in the membrane
  • alpha helix shape to maximize number of hydrogen bonds
41
Q

describe hydrophobic vs hydrophilic in transmembrane protein beta barrel porins

A
  • hydrophilic AA line the inside of the barrel (allow water to pass thru)

-hydrophobic AA face the fatty acid tails

42
Q

alpha helices are _____

A

amphipathic

43
Q

describe monolayer associated alpha helix (2)

A
  • almost entirely on cytosolic side
  • anchored by an amphipathic alpha helix
44
Q

describe lipid linked proteins (3)

A
  • found outside of bilayer
  • secured thru one or more covalent attachments to phospholipids
  • on either side of the membrane
45
Q

describe protein attached peripheral proteins (3)

A
  • attached to other membrane proteins
  • can be on either side
  • DONT need a detergent to remove
46
Q

describe cell membrane cortex

A
  • meshwork of fibrous proteins attached to transmembrane proteins that adds strength and support to plasma membrane
47
Q

in vivo cells ____ movement of proteins

A

restrict

48
Q

describe glycocalyx (3)

A

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

49
Q

glycolipid vs glycoprotein vs proteoglycans

A

(all included in glycocalyx)

lipid
- carbohydrate attached lipid

protein
- carbohydrate attached protein

proteoglycans
-sub category of glycoprotein (help protect)

50
Q

what is glycosylation

A

attachment of carbohydrate to the backbone of a protein

BIOL 2202 CMBean Midterm 2 (4 decks)

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