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AAA BIO108: General Physiology > 2a. Cell Membrane Structure > Flashcards

2a. Cell Membrane Structure Flashcards

1
Q

What is a cell membrane?

A
  • Acts as a boundary
  • Controls what enters and leaves cell
  • Regulates chemical composition
  • Maintains homeostasis
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2
Q

Why is cell membrane call the gateway to the cell?

A

cell’s outer membrane acts as a gate, preventing intruders from invading the cell.

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3
Q

What is the importance of the cell membrane?

A

main role is to provide protection to the cell from its surroundings. It controls the passage of some solutes and water into and out of the cell.

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4
Q

The cell membrane in unicellular organisms is

A

flexible and allows to
move

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5
Q

Studies of the red blood cell plasma
membrane provided ____

A

the first evidence that
biological membranes consist of lipid bilayers.

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6
Q

The role of the cell membrane in the plant cell is ____

A

to separate the cytoplasm of the cell from its cell wall.

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7
Q

Sandwich model was proposed by?

A

Danielli and Davson

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7
Q

3 Plasma Membrane Model

A
  1. Sandwich Model
  2. Unit Membrane Model
  3. Fluid Mosaic Model
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8
Q

What is fluid mosaic model?

A

Phospholipid bilayer with proteins partially or fully imbedded, seen with freeze-fractured membrane via electron micrographs

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8
Q

What is sandwich model?

A

2 layers of globular proteins with phospholipid inside to make a layer and then join 2 layers together to make a channel for molecules to pass

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9
Q

Who proposed unit membrane model?

A

Robertson

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10
Q

What is the outer layer of PPL bilayer?

A

glycoprotein coat

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10
Q

What is unit membrane model?

A
  1. Outer layer of protein with phospholipid bilayer inside,
  2. believed all cells same composition,
  3. does not explain how some molecules pass through or the use of
    proteins with nonpolar parts
  4. used transmission electron microscopy
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11
Q

Who proposed fluid mosaic model?

A

Singer and Nicolson

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12
Q

Process on how to verify the correct membrane model?

A

1) Rapidly freeze specimen
2) Use special knife to cut membrane in half
3) Apply a carbon + platinum coating to the surface
4) Use scanning electron microscope to see the surface

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13
Q

According to the electron micrograph which membrane model is correct?

A

Fluid-Mosaic Model

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14
Q

What model is the Basic paradigm of biological
membrane structure

A

Fluid-mosaic model

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15
Q

The lattice becomes ____ at
the transition temperature.

A

frozen crystalline gel

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15
Q

The lipids in a membrane are organized into a
_____

A

liquid crystalline lattice.

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16
Q

What composes in FM model freeze-fracture?

A

there is a P face and E surface, extracellular surface of membrane

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16
Q

What composes in FM model section?

A

bimolecular lipid leaflets (trilaminar)

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16
Q

The Plasma Membrane is composed of two layers of lipids. Why is this important?

A

Having lipids in the plasma membrane means that at least a portion of the membrane repels the water that constantly surrounds it. Allowing
too much water inside the cell could cause the cell to burst.

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17
Q

2 Layers of the FM Model

A
  1. Fluid
  2. Mosaic
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18
Q

Describe the fluid in FM Model

A

plasma membrane has consistency of olive oil at body temperature, due to unsaturated phospholipids

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19
Q

What happens to the PPL and proteins in the fluid layer

A

move around freely within the layer, like it’s a
liquid.

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20
Q

Describe the mosaic layer of FM Model

A
  1. proteins form a collage that differs on either side of membrane and from cell to cell (greater than 50 types of proteins)
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21
Q

Describe the protein span of the mosaic layer

A
  1. proteins span the membrane with hydrophilic portions facing out and hydrophobic portions facing in.
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22
Q

describe the mosaic pattern of the FM Model

A
  1. mosaic pattern produced by scattered protein molecules when membrane
    is viewed from above.
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23
Q

What happens if it in low temperature?

A

hydrocarbons are tightly packed and in gel phase

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24
Q

What happens if it in higher temperature?

A

moves to fluid phase, bilayer “melts”, movement is allowed

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25
Q

Formation of sphere is ____?

A

energetically favorable

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26
Q

Describe the sphere in energetically unfavorable?

A

planar phospholipid bilayer with edges exposed to water

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27
Q

Describe the sphere in energetically favorable?

A

sealed compartment formed by phospholipid bilayer

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27
Q

planar lipid bilayers spontaneously ___

A

form vesicles

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28
Q

What is the surroundings of the sphere bilayer?

A

water inside and outside

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29
Q

it is a harsh ionic detergent

A

SDS (sodium dodecyl sulfate)

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30
Q

a gentler non-ionic detergent and commonly used solubilizing agents

A

Triton X-100

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30
Q

What happens when you put SDS in the bilayer?

A

SDS will intercalate first with the phospholipids and will increase the hydrophilicity of the membrane promoting a leak first and complete disruption eventually

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30
Q

What is the difference between triton X-100 and SDS in terms of effects?

A

Triton-X-100 is a non-ionic detergent suitable for gently solubilizing proteins without denaturing them, while SDS is an anionic detergent that denatures proteins

31
Q

What happens when you have detergent in the bilayer?

A

lysing cells to extract protein and other cellular organelles or to permeabilize the living cell membrane for transfection

32
Q

What are integral membrane proteins?

A

Integral membrane proteins are embedded in the lipid bilayer and can be removed only by disrupting the bilayer.

33
Q

how does detergent remove protein membrane?

A

These amphipathic molecules disrupt the bilayer by forming mixed phospholipid-detergent micelles.

34
Q

Process to isolate a protein from its membrane

A
  1. detergent micelles + monomers added to the membrane
  2. they will be solubilized membrane proteins
  3. will now became lipid-detergent micelles
  4. purification of NaK pump
  5. Removal of detergent micelles + monomers
  6. Addition of phospholipids (mixed with detergent)
  7. functional protein incorporated into phospholipid vesicle
34
Q

Scheme to Study a
Membrane Protein (3)

A

Solubilization,
Purification, and
Reconstitution in
Liposomes

35
Q

Membrane
Proteins Can Be
Solubilized by?

A

Detergents That
Disrupt the
Membrane

36
Q

Structure of the Plasma Membrane (9)

A
  1. extracellular matrix
  2. glycoprotein
  3. carbohydrate
  4. glycolipid
  5. cytoplasm
  6. cholesterol
  7. proteins
  8. phospholipid
  9. microfilaments of cytoskeleton
37
Q

Membrane movement

A
  1. lateral movement (frequent)
    > flexion
    > rotation
  2. flip-flop (rare)
38
Q

movement of phospholipids

A
  1. Most of the lipids and some proteins drift laterally on either side.
  2. Phospholipids do not switch from one layer to the next.
39
Q

Movement of lipids and proteins in the cell membrane

A

not fixed in position but constantly moving.

40
Q

While the lipids can move both laterally and rotate 360 degrees

A

flip-flop diffusion

40
Q

The proteins move laterally within the cell membrane

A

lateral diffusion

41
Q

Cholesterol affects ____

A

fluidity

42
Q

Cholesterol at colder temperature

A

it maintains fluidity by not allowing phospholipids to pack close together.

42
Q

Cholesterol at body temperature (2)

A
  1. it lessens fluidity by restraining the movement
    of phospholipids
  2. reduce permeability to small mol
43
Q

our body needs some cholesterol to make _____

A

hormones, vitamin D, and substances that help you digest foods

43
Q

The Planar Rings of Cholesterol Make
the Membranes what? (3)

A
  1. More Rigid
  2. Less Permeable
  3. Resistant to Low Temperature Crystalization
44
Q

a waxy, fat-like substance that’s found in all the cells in your body.

A

cholesterol

45
Q

plant membrane have no cholesterol but have

A

sterols

46
Q

A major membrane component in animal cells

A

cholesterol

47
Q

Cholesterol stabilizes the cell membrane by ____

A

forming interactions with the phospholipid tails and heads
This makes their structure more rigid and helps provide stability

48
Q

Paracrystalline state (solid)

A

a. heat produces thermal motion of acyl side chains (solid –> fluid transition)
b. (fluid state) lateral diffusion in plane of bilayer
c. transbilayer diffusion

49
Q

Classification of membrane proteins

A
  1. peripheral membrane proteins
  2. integral membrane proteins
  3. transmembrane proteins
50
Q

proteins that dissociate from the membrane following treatments with polar reagents that do not disrupt the phospholipid bilayer.

A

peripheral membrane proteins

51
Q

Integral membrane proteins

A

can be released only by
treatments that disrupt the phospholipid bilayer.

51
Q

can be released only by
treatments that disrupt the phospholipid bilayer.

A

integral membrane proteins

51
Q

span the lipid bilayer with portions exposed on both sides of the membrane.

A

Transmembrane proteins

52
Q

Peripheral MP

A

proteins that dissociate
from the membrane following treatments with polar reagents that do not disrupt the phospholipid bilayer.

53
Q

Transmembrane proteins

A

span the lipid bilayer with portions exposed on both sides of the membrane.

54
Q

6 types of membrane proteins

A
  1. transport protein
  2. receptor protein
  3. enzymatic protein
  4. cell recognition protein
  5. attachment proteins
  6. intercellular junction proteins
55
Q

channel for lipid
insoluble molecules
and ions to pass freely
through

A

Channel Proteins

56
Q

bind to a substance and
carry it across membrane, change
shape in process

A

carrier proteins

57
Q

Bind to chemical
messengers (Ex.
hormones) which
sends a message into
the cell causing
cellular reaction

A

receptor proteins

58
Q

Carry out enzymatic
reactions right at the
membrane when a
substrate binds to the
active site

A

enzymatic proteins

59
Q

Glycoproteins (and
glycolipids) on
extracellular surface
serve as ID tags
(which species, type of
cell, individual).

A

cell recognition proteins

60
Q

are short branched chains of less than 15 sugars

A

Carbohydrates

61
Q

Attach to cytoskeleton (to maintain cell shape and stabilize proteins) and/or the extracellular
matrix

A

attachment proteins

61
Q

protein fibers and carbohydrates secreted by cells and fills the
spaces between cells and supports cells in a tissue.

A

extracellular matrix

62
Q

Extracellular matrix can
influence the ____

A

activity inside the cell and coordinate the behavior of all the cells in a tissue.

63
Q

types of cell junction (2)

A

–Tight junctions
–Gap junctions

63
Q

Bind cells together

A

intercellular junction proteins

64
Q

Transmembrane Proteins of opposite cells attach in a tight zipper-like fashion; No leakage

A

tight junction

64
Q

Examples of tight junctions

A

Ex. Intestine, Kidneys, Epithelium of skin

65
Q

Describe the tight junction in epithelial cells

A

TJ bar the movement of dissolved materials from the lumen through the spaces in between

66
Q

Cytoplasmic plaques of two cells bind with the aid of intermediate filaments of keratin; allows for stretching

A

desmosomes

67
Q

Examples of desmosomes

A

stomach, bladder, heart

68
Q

a transmembrane protein that binds with other cadherins to form junctions known as desmosomes between cells

A

desmogleins

69
Q

Channel proteins of opposite cells join together providing
channels for ions, sugars, amino acids, and other small
molecules to pass.

A

gap junctions

70
Q

allows communication between cells

A

gap junctions

71
Q

only intercellular junctions in plants between walls of 2 adjacent plant cells

A

plasmodesmata

71
Q

examples of gap junctions

A

heart muscle, animal embryos

72
Q

the motion of protein molecules under the influence of an electric field that is applied across the fluid that they are dispersed in

A

mobility of membrane proteins

73
Q

Many Membrane Proteins Move _____

A

Freely in the Plane of the Membrane

74
Q

(FRAP)

A

Fluorescence Recovery After Photobleaching

74
Q

fusion of membrane protein process

A
  1. cell fusion creates heterocaryon
75
Q

2 types of transport protein

A
  1. channel protein
  2. carrier protein

AAA BIO108: General Physiology (12 decks)

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