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GENERAL PHYSIOLOGY > 2A: Cell Membrane structure > Flashcards

2A: Cell Membrane structure Flashcards

1
Q

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

A

Cell Membrane

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2
Q

provided the first evidence that biological membranes consist of lipid bilayers.

A

Studies of the red blood cell plasma membrane

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3
Q

is flexible and allows a unicellular organism to move

A

Cell membrane

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4
Q
  • Important component of Physiology
  • Makes life possible
A

Homeostasis

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5
Q

3 factors of Cell Membrane

A
  • Homeostasis
  • Protection
  • Setting boundaries
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6
Q

Semi permeable and allows maintenance of homeostasis

A

Cell membrane

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7
Q
  • Allows flexibility
  • Provided the first evidence that biological membranes consists of lipid bilayer
A

Plasma membrane

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8
Q

Allows unicellular organisms to move

A

Flexibility

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9
Q

Plasma Membrane models

A

Sandwich model
Unit membrane model
Fluid mosaic model

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10
Q
  • 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
A

Sandwich Model
(Danielli + Davson)

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11
Q

Protein coat of Sandwich model

A

Hydrophilic

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12
Q

Lipid layer of Sandwich model

A

hydrophobic

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13
Q
  • Outer layer of protein with phospholipid bilayer inside,
  • believed all cells same composition,
  • does not explain how some molecules pass through or the use of proteins with nonpolar parts
  • used transmission electron microscopy
A

Unit Membrane Model ( Robertson)

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14
Q

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

A

Fluid Mosaic Model
(Singer + Nicolson)

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15
Q
  • Hydrophilic heads facing outwards, hydrophobic tails facing inwards.
  • used the freeze-fructure membrane to test the model
A

Fluid-Mosaic model

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16
Q
  • Rapidly freeze specimen
  • use special knife to cut membrane into half.
  • Apply carbon + platinum
  • Viewed through scanner electron microscope
A

Freeze-fracture of membrane

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17
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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18
Q

– plasma membrane has consistency of olive oil at body temperature, due to unsaturated phospholipids.
-phospholipids and proteins move around freely within the layer, like it’s a liquid.

A

Fluid

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19
Q

– proteins form a collage that differs on either side of membrane and from cell to cell (greater than 50 types of proteins)
- proteins span the membrane with hydrophilic portions facing out and hydrophobic portions facing in.
- mosaic pattern produced by scattered protein molecules when membrane is viewed from above.

A

Mosaic

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20
Q

low temperatures

A
  • Gel phase or gel like cell membrane
  • Hydrocarbons are tightly packed
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21
Q

Higher temperature

A
  • Moves to fluid phase
  • bilayer “melts” movement is allowed
  • tails move
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22
Q

Formation of sphere is

A

energetically favorable

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23
Q

Spontaneously Form Vesicles

A

Planar Lipid Bilayers

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24
Q

commonly used solubilizing agents

A

SDS and Triton X-100

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25
Q
  • Harsh ionic detergent
  • sodium dodecyl sulfate
  • used in DNA
A

SDS

26
Q

a gentler non-ionic detergent

A

Triton X-100

27
Q
  • Disrupts the membrane from lipids
  • Disrupts the protein to isolate DNA
A

Detergent

28
Q

Structure and functions of Plasma

A
  • Selectivity
  • Barrier
29
Q

Movement of phospholipid

A
  • Most of the lipids and some proteins drift laterally on either side.
  • Flipflop happens rarely
  • Phospholipids do not switch from one layer to the nest
30
Q

Cholesterol

A

Affects fluidity

31
Q

Cholesterol affects fluidity: at body temperature

A
  • it LESSENS FLUIDITY by restraining the movement of phospholipids
  • reduce permeability to small mol
32
Q
  • Make the Membrane More Rigid
  • Less Permeable
  • Resistant to Low
    Temperature Crystalization
A

Planar Rings of Cholesterol

33
Q

Major membrane component (Animals)

A

Cholesterol

34
Q
  • Have the same function as cholesterol
  • Plants’ counterpart of cholesterol
A

Sterols

35
Q

3 classification of Membrane proteins

A

Peripheral membrane proteins
Integral membrane proteins
Transmembrane proteins

36
Q

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

A

Peripheral membrane proteins

37
Q

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

A

Integral membrane

38
Q

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

A

Transmembrane proteins

39
Q

Types of membrane proteins

A

Channel protein
Carrier protein
Cell recognition protein
Receptor protein
Enzymatic protein

40
Q
  • allows ions to cross freely
A

Channel Protein

41
Q

Ex. of disorder of channel

A

Cystic fibrosis

42
Q
  • Selectively interacts with a specific molecule of ion so that it can cross the plasma membrane.
A

Carrier protein

43
Q
  • The MHC (major histocompatibility complex)
A

Cell recognition

44
Q
  • Shaped in such a way that specific molecule can bind to it.
A

Receptor protein

45
Q
  • Essential for cell recognition
  • rejects incompatible cells
A

MHC (Major histocompatibility complex)

46
Q
  • Catalyzes specific reaction.
A

enzymatic protein

47
Q

Transport proteins

A

Channel Proteins
Carrier Proteins

48
Q

–
channel for lipid insoluble molecules and ions to pass freely through

A

Channel Proteins

49
Q

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

A

Carrier Proteins

50
Q
  • Bind to chemical messengers (Ex. hormones) which sends a message into the cell causing cellular reaction
A

Receptor Proteins

51
Q

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

A

Enzymatic Proteins

52
Q

– Glycoproteins (and glycolipids) onextracellular surface
serve as ID tags (which species, type of cell, individual).
- Carbohydrates are short branched chains of less than 15 sugars

A

Cell Recognition Proteins

53
Q
  • Attach to cytoskeleton (to maintain cell shape and stabilize proteins) and/or the extracellular matrix (integrins connect to both)
A

Attachment Proteins

54
Q

– protein fibers and carbohydrates secreted by cells and fills the spaces between cells and supports cells in a tissue.
- can influence activity inside the cell and coordinate the behavior of all the cells in a tissue.

A

Extracellular Matrix

55
Q

– Bind cells together
– Tight junctions
– Gap junctions

A

Intercellular Junction Proteins

56
Q

Types of cell Junctions

A

Tight junctions
Desmosomes
Gap junctions

57
Q

• Transmembrane Proteins of opposite cells attach in a tight zipper-like fashion
• No leakage Ex. Intestine, Kidneys, Epithelium of skin

A

Tight Junctions

58
Q

• Cytoplasmic plaques of two cells bind with the aid of
intermediate filaments of keratin
• Allows for stretching
• Ex. Stomach, Bladder, Heart

A

Desmosomes

59
Q

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

A

Gap Junctions

60
Q

Cholesterol1 colder temperatures

A
  • it MAINTAINS FLUIDITY by not allowing phospholipids to pack close together.

GENERAL PHYSIOLOGY (8 decks)

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