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B12 > The Plasma Membrane (2.3) > Flashcards

The Plasma Membrane (2.3) Flashcards

1
Q

State what controls plasma membrane impermeability to polar molecules

A

The phospholipid bilayer

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2
Q

Describe the impact of temperature on the fluidity of the cell membrane (absence of cholesterol)

A

low temp - rigid, low flexibility (membrane may break)

high temp - fluid, high flexibility (membrane won’t hold shape)

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3
Q

Describe amphipathic

A

Both hydrophobic and hydrophilic regions

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4
Q

Provide one example of an amphipathic structure

A

Phospholipids

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5
Q

Describe lateral movement of phospholipids

A

Rotate to switch places horizontally

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6
Q

Describe transverse movement (flip-flopping) of phospholipids

A

Rotate to switch places vertically

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7
Q

Define phospholipid bilayer

A

Two layers of phospholipids with hydrophobic fatty acid tails projecting inwards and hydrophilic glycerol and phosphate head groups projecting outwards

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8
Q

Describe polar and non-polar organisation of plasma membranes

A

Glycerol and phosphate head group - polar

Fatty acid tails - non-polar

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9
Q

Describe temperature as a factor affecting the fluidity of the plasma membrane

A

High temp = High fluidity

Low temp = High viscosity (saturated hydrocarbon tails)

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10
Q

State whether a phospholipid head is hydrophilic or hydrophobic

A

Hydrophilic

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11
Q

State whether a phospholipid tail is hydrophilic or hydrophobic

A

Hydrophobic

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12
Q

State 4 functions of peripheral proteins

A
  • Enzymes
  • Receptors
  • Structural attachment points
  • Recognition sites
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13
Q

Describe 2 major functions of the plasma membrane

A
  1. Controls entry and exit of substances into and out of the cell (differentially permeable)
  2. Separates internal and external environment
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14
Q

Describe the structure of the plasma membrane

A

Double layer of phospholipids with proteins scattered throughout which creates a differentially permeable barrier between the intracellular and extracellular fluid

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15
Q

Compare and contrast membrane fluidity and viscosity (Describe phospholipid composition and structure)

A

Fluidity: Unsaturated hydrocarbon tails prevent packing
Viscosity: Saturated hydrocarbon tails pack together

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16
Q

Describe transmembrane proteins

A

Integral proteins that span both phospholipid layers

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17
Q

Describe integral proteins

A

Proteins that are a permanent part of the plasma membrane

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18
Q

Describe peripheral proteins

A

Proteins that are a temporary part of the plasma membrane

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19
Q

Describe why peripheral proteins are a temporary part of the plasma membrane

A

Not embedded in the phospholipid bilayer

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20
Q

State 2 structures which peripheral proteins attach to on the plasma membrane

A
  1. Phospholipid molecules

2. Integral proteins (either layer of the plasma membrane)

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21
Q

State classification of a phospholipid with a cis double bond

A

Unsaturated

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22
Q

State classification of a phospholipid without a cis double bond

A

Saturated

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23
Q

State the 6 major functions of integral proteins

A
  1. Act as transport channels
  2. Function as enzymes
  3. Involved in signal transduction
  4. Cell-to-cell recognition
  5. Attach to cytoskeleton/extracellular matrix
  6. Intercellular joining
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24
Q

Describe impact of cis double bonds on fluidity of the plasma membrane

A

Creates kinks in the unsaturated fatty acid chains of the plasma membrane - less easy to pack together
(increasing membrane fluidity)

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25
Q

Describe lipophilic

A

(Hydrophobic)

Not water soluble - substances easily cross membrane

26
Q

Describe hydrophobic

A

Not water soluble - ‘water hating’

27
Q

Describe hydrophilic

A

Water soluble - ‘water loving’

28
Q

Describe why proteins group in clusters

A
  • similar functions

- same biochemical pathways

29
Q

Outline what the fluid mosaic model proposes

A

Phospholipids and unanchored proteins are free moving, with anchored proteins scattered throughout.

30
Q

State 3 materials which are scattered throughout the plasma membrane

A
  1. Proteins
  2. Carbohydrates
  3. Cholesterol
31
Q

Define phospholipid

A

Essential component of the plasma membrane, comprised of a hydrophilic glycerol and phosphate head group and two hydrophobic fatty acid tails

32
Q

Define plasma membrane

A

Semi-permeable boundary that regulates the movement of substances between the extracellular to intracellular fluid, composed of a phospholipid bilayer

33
Q

State the 2 forms of phospholipid tails

A
  1. Saturated

2. Unsaturated

34
Q

Describe the hydrophobic and hydrophilic regions of the phospholipid bilayer

A

Hydrophobic interior and hydrophilic exterior

35
Q

State what 2 types of regions integral proteins have

A
  • Hydrophobic

- Hydrophilic

36
Q

State 2 major carbohydrate forms found within the plasma membrane

A
  • Glycoproteins (attached to proteins)

- Glycolipids (attached to lipids)

37
Q

Describe the extracellular matrix

A

Collection of extracellular molecules secreted by cells that provides biochemical support to surrounding cells

38
Q

State the 2 common locations of proteins within the plasma membrane

A
  • Clustered in groups

- Distributed randomly throughout the membrane

39
Q

State 3 major functions of carbohydrates within the plasma membrane

A
  • Cell-to-cell recognition
  • Cell adhesion
  • Recognition of antibodies, hormones and viruses
40
Q

Describe how compartmentalisation within eukaryotes optimises cellular efficiency

A

Groups particular enzymes and reactants for particular functions in high concentrations at optimal levels

41
Q

Describe the structure of phospholipids

A

Composed of a hydrophilic glycerol and phosphate head group and two fatty acid tails

42
Q

Phospholipids will react with the presence of water. True/False

A

True

43
Q

State 4 major functions of the plasma membrane

A
  1. Active boundary
  2. Cell identity
  3. Receiving external signals
  4. Transport
44
Q

Classify non-polar molecules as hydrophilic or hydrophobic

A

Hydrophobic

45
Q

Classify polar molecules as hydrophilic or hydrophobic

A

Hydrophilic

46
Q

Relate the characteristics of phospholipids to the arrangement of the plasma membrane

A

Phospholipids are amphipathic
- Fatty acid tails have a low interaction with water
- Phosphate head groups have a high interaction with water
Phospholipids aggregate by orientating hydrophobic tails towards one another

47
Q

Describe the structure of glycolipids as an amphipathic protein

A

Sugar group (hydrophilic) and covalently bonded lipid tail (hydrophobic)

48
Q

Describe the structure of cholesterol as an amphipathic protein

A

Hydroxyl group (-OH) (hydrophilic) and hydrocarbon chain and steroid (hydrophobic)

49
Q

State in which plasma membranes cholesterol is present

A

Animal cells

50
Q

Describe the effect of cholesterol on the plasma membrane in high temperature

A

Prevents increase in fluidity

51
Q

Describe the effect of cholesterol on the plasma membrane at low temperatures

A

Prevents increase in viscosity

52
Q

Describe the effect of cholesterol on the movement of phospholipids at various temperatures

A

Restricts phospholipid movement and acts as a buffer for changing temperatures

53
Q

State 2 characteristics of membrane proteins in relation to plasma membrane structure

A
  • Move within the bilayer

- Attach to cytoskeleton

54
Q

State the 3 factors that influence the fluidity of the plasma membrane

A
  • Phospholipid composition and structure
  • Temperature
  • Cholesterol
55
Q

Describe what cholesterol is composed of

A

4 fused carbon rings

56
Q

Describe phospholipid composition and structure as a factor affecting plasma membrane fluidity

A

Increase saturated fatty acid tails = low fluidity

Decrease saturated fatty acid tails and increase unsaturated fatty acid tails = high fluidity

57
Q

Describe how compartmentalisation within eukaryotes decreases cell vulnerability to environmental changes

A

Separates processes inside the cell (an environmental change would affect the cell cytosol more than individual membrane bound organelles)

58
Q

Describe 2 factors supporting the importance of plasma membrane fluidity

A
  • Substance permeability

- Capacity for proteins to move across the membrane to particular cell areas

59
Q

Describe vesicle

A

Structure within or outside a cell, consisting of liquid or cytoplasm enclosed by a lipid bilayer.

60
Q

State whether or not carrier and channel proteins are considered permanent or temporary parts of the plasma membrane and identify the overall protein classification

A

Permanent

Transmembrane proteins

61
Q

Provide an example of a peripheral protein in function

A

Proteins involved in controlling the synthesis/destruction of the cell membrane

B12 (41 decks)

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