Lecture 2.1 - Membranes, Channels and Transport Flashcards
1
Q
- separates the cytoplasm from the external environment
- one of the most important cell organelles
- highly selective permeable barrier that surrounds all living cells
- controls how molecules and compounds move in and out of the cell
- important for proper nutrition, maintenance of irritability of the cells, and homeostasis
A
cell membrane
2
Q
cell membranes are __ __ __ barrier
A
highly selective permeable
3
Q
cell membranes controls how molecules and compounds move ___ of cell
A
in and out
4
Q
importance of cell membrane
A
- proper nutrition
- maintenance of irritability
- homeostasis
- signal detection
- cell-to-cell communication
5
Q
for organization and localization of specific functions
A
compartmentalization
6
Q
thickness of cell membrane
A
6-23 nm
7
Q
what happens when the cell membrane sustains different concentrations of certain ions on their two sides
A
lead to concentration gradient
8
Q
participates in the transport of substances
A
protein structures
9
Q
- model that describes the organization of cell membranes
- phospholipids drift and move like a fluid
- bilayer is a mosaic mixture of phospholipids, steroids, proteins, and other molecules
A
fluid mosaic model
10
Q
membrane composition
A
- phospholipids
- proteins
- carbohydrates
11
Q
how are lipids and protein molecules in the cell membrane kept together
A
non-covalent interactions
12
Q
impermeable to the passage of most water-soluble molecules
A
lipid bilayer
13
Q
fundamental structure of the membrane
A
lipid molecules
14
Q
- usually span from one side of the phospholipid bilayer to the other, but can also sit on one of the surfaces
- can slide around the membrane very quickly and collide with each other, but selfom flip from one side to the other
- responsible for most of the membrane’s properties
A
proteins
15
Q
Two types of proteins based on where they are found
A
- integral proteins
- peripheral proteins
16
Q
- embedded in the lipid bilayer
- provide a mechanism for trans-membrane transport
A
integral proteins
17
Q
different trans-membrane transport integral proteins provide a mechanism for
A
- passive transport pores and channels
- active transport pumps and carriers
- membrane-linked enzymes
- chemical signal receptors and transducers
18
Q
associated with the surface of the membrane via electrostatic interaction
A
peripheral proteins
19
Q
how are the peripheral proteins associated with the surface of the membrane
A
via electrostatic interaction
20
Q
what do proteins inside the surface maintain
A
cell shape or cell motility
21
Q
catalyze reactions in the cytoplasm
A
enzymes
22
Q
what are receptor proteins used for
A
- cell signaling
- cell recognition
23
Q
Different major cell functions of the proteins in plasma membrane
A
- transport
- enzymatic activity
- signal transduction
- intercellular joining
- cell-cell recognition
- attachment to the cytoskeleton and extracellular matrix (ECM)
24
Q
Special functions of proteins
A
- adhesion proteins
- recognition proteins
- receptor proteins
- enzymes
- transport proteins (active and passive)
25
- found on the outer surface and attached to the proteins or sometimes to the phospholipids
- form a cell coat outside the cell membrane
carbohydrates
26
Different types of carbohydrates on the cell membrane
1. glycoproteins
2. glycolipids
27
carbohydrate chains attached to membrane proteins
glycoproteins
28
carbohydrate chains attached to the lipid element of the cell membrane
glycolipids
29
- defined as a thick mixture of protein lipids and post-translational sugar structures
- surround all living cells and act as a buffer
Glycocalyx
30
functiono of glycocalyx
- protection
- cell recognition
31
facilitate cellular recognition
glycolipid
32
serve as receptor for chemical signals
glycoproteins
33
what is the side chain of glycoproteins
oligosaccharide side chain
34
Primary types of lipids
1. phosphoglycerides
2. sphingolipids
3. sterols
35
glycerol backbone
phosphoglycerides
36
backbone made of sphingosine bases
sphingolipids
37
cholesterol, nonpolar and only slightly soluble in water
sterols
38
amphipathic lipids
- phosphoglycerides
- sphingolipids
39
what does the differences in the lengths of the two fatty acid tails and composition influence
fluidity
40
binds weakly to phospholipids making the membrane less fluid but stronger
cholesterol
41
how are membrane molecules help in place
relatively weak hydrophobic interactions
42
Two possible movement of phospholipids
1. lateral movement
2. flip-flop
43
frequent movement of phospholipids
lateral movement
44
rare movement of phospholipids
flip-flop
45
influenced by temperature and constituents
membrane fluidity
46
what influences membrane fluidity
temperature and constituents
47
fluid membrane
unsaturated hydrocarbon tails with kinks
48
viscous membrane
saturated hydrocarbon tails
49
- wedged between phospholipid molecules in the plasma membrane of animal cells
- at warm temperature, it restrains the movement of phospholipids and reduces fluidity
- at cool temperatures, it maintains fluidity by preventing tight packing
steroid cholesterol
50
what does steroid cholesterol do at warm temperatures
restrains movement of phospholipids and reduce fluidity
51
what does steroid cholesterol do at cool temperatures
maintains fluidity by preventing tight packing
52
enzymes that break down protein
Proteolytic enzymes (proteases)
53
- consists of physically breaking apart (fracturing) a frozen biological sample
- used to split the cell membrane apart
freeze-fracture technique
54
what was seen when a cell membrane was freeze fractured
protein particles interspersed with a smooth matrix, supporting fluid mosaic model
55
- rate at which a substance can passively penetrate a cell membrane
- influenced by inherent properties of both the membrane and the substance
membrane permeability
56
Different Transport Systems
1. passive process
2. active transport (pumping)
57
- no energy expenditure and move down their normal gradient
- simple diffusion/lipid diffusion
- osmosis
- facilitated diffusion
passive processes
58
- requires metabolic energy
- moves substances against their gradients
active transport (pumping)
59
Different types of passive transport
1. simple diffusion/lipid diffusion
2. osmosis
3. facilitated diffusion/passive transport
60
Three basic routes in transport systems
1. dissolving in lipid phase
2. diffusion through labile or fixed aqueous channels
3. carrier-mediated transport
61
- dissolves directly in the lipid bilayer
- enters the aqueous phase on the opposite side
dissolving in the lipid phase
62
- solute molecule remains in the aqueous phase
- diffuses through aqueous channels (water-filled pores in the membrane)
diffusion through labile or fixed aqueous channels
63
water-filled pores in the membrane
aqueous channels
64
- solute molecule combines with a carrier molecule dissolved in a membrane
- carrier "mediates" of "facilitates" the movement of the solute molecule across the membrane
carrier-mediated transport
65
random thermal motion of suspended or dissolved molecules causes their dispersion from regions of higher concentration to regions of lower concentrations
diffusion
66
each substance diffuse down its __ concentration gradient, independent of the concentration gradies of other substances
own
67
diffusion of a substance across a biologial membrane
passive transport
68
Diffusion is __ because in this process the particle uses free energy (potential energy).
exergonic
69
states that the rate of diffusion across a membrane is directly proportional to the concentration gradient of the substance on the two sides of the membrane and inversely related to the thickness of the membrane
Fick's Law of Diffusion
70
According to Fick's Law, diffusion is proportional to what?
- concentration gradient
- difference in partial pressure
71
intrinsic factors governing diffusion across membranes
1. size rules
2. polarity rules
3. ionic rules
72
size rule ex.
water > urea
73
polarity rule ex.
non polar > polar
74
ionic rule ex.
O2 > OH-
75
Five factors where the rate of diffusion depends on
1. size
2. temperature
3. steepness of concentration gradient
4. charge
5. pressure
76
Factors that influence mobility of solute molecules
1. lipid solubility
2. hydrogen bond with water
3. molecular weight
4. molecular shape
5. partition coefficient
77
mobility with high lipid sobility
high
78
mobility with high hydrogen bond with water
low
79
ratio of the distribution of a substance between two different liquid phases
partition coefficient
80
rate of influx increases in proportion to the concentratin of the solute in the extracellular fluid
non-saturation kinetics
