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Alia - Biology > Lecture 6-Plasma Membrane > Flashcards

Lecture 6-Plasma Membrane Flashcards

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1
Q

What is the fluid mosaic model?

A

A 2-dimensional liquid that restricts the LATERAL DIFFUSION of membrane components

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2
Q

What type of regions does the cell membrane contain?

A
  • Lipid rafts
  • Proteins
  • Glycolipids
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3
Q

Give the breakdown of the membrane?

A
  • Phospholipids (75%)
  • Cholesterol (20%)
  • Polar glycolipids in external layer (5%)
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4
Q

What is cholesterol a useful structural lipid for in membranes?

A

LIPID RAFTS

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5
Q

How many times to neighbouring lipid molecules swap places?

A

10 million times /s

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6
Q

What does the cholesterol in a membrane do?

A

IMMOBILIZES the 1st hydrocarbon group of the phospholipids

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7
Q

What effect does the immobilising cholesterol have on the membrane>

A

Less deformable + decreases permeability (to small-water soluble molecules)

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8
Q

What does fluidity in the membrane allow?

A

The movement of the membrane components required for cell movement + growth + division + secretion / formation of cellular junctions

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9
Q

How does the glycocalyx protect the GI?

A

Prevents drying out by making RBCs slippery

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10
Q

What is the function of phospholipid bilayer?

A

Regulates what enters + exits the cells

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11
Q

What does regulating what enters + exits the cell affect?

A

Altering pH + charge

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12
Q

What does the phospholipid bilayer play a huge roll in?

A

Cell signalling e.g. hormones

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13
Q

What type of functions do phospholipid bilayers have?

A

Enzymatic functions

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14
Q

What do phospholipids bilayers aid in?

A

Cell linking + cross-talk

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15
Q

What is the lipid bilayer permeable to?

A
  • Non-polar molecules
  • O2
  • CO2
  • Hormones
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16
Q

WHat is the lipid bilayer impermeable to?

A

Ions + Large molecules

  • Na+
  • Glucose
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17
Q

How do Na+ + glucose cross the impermeable lipid bilayer?

A

Transmembrane channels + carrier proteins

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18
Q

What is the lipid bilayer SLIGHTLY permeable to?

A

Small , uncharged polar molecules

-H20

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19
Q

What does selective permeability allow?

A
  • Build-up concentration gradients
  • Regulate pH
  • Build electrical gradients (inside = more -ve) creating MEMBRANE POTENTIAL
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20
Q

Which is more concentrated in the extracellular fluid?
-02 + Na+
or
-K+ + CO2

A

02 + Na+

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21
Q

Name all the passive types of transport?

A
  • diffusion
  • osmosis
  • facilitated diffusion
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22
Q

Name all the active types of transport?

A
  • primary

- secondary

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23
Q

Name all the vesicular types of transport?

A
  • endocytosis
  • phagocytosis
  • pinocytosis
  • transcytosis
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24
Q

What is passive transport?

A

No cellular energy is used as substances move DOWN their conc gradient

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25
Q

Describe the passive transports in context?

A
  • Diffusion through lipid bilayer
  • Channel mediated facilitated diffusions
  • Carrier mediated facilitated diffusion
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26
Q

What is the equilibrium potential?

A

The potential gradient across the membrane to maintain concentration gradient

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27
Q

Describe the different types of channel mediated facilitated transport?

A

Can be gated i.e. voltage/ligand

Can be times i.e. signal regulated

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28
Q

What are carrier molecules subjected to?

A

Transport maximum + saturation

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29
Q

How is the hormone insulin regulated?

A

Its receptor , up-regulates glucose transporters

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30
Q

What do diabetic patients lack?

A

The ability to up-regulate GluT

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31
Q

What is osmosis?

A

The diffusion of water through a SEMI-PERMEABLE membrane

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32
Q

Diffusion through the lipid bilayer occurs through what?

A

Specific transmembrane proteins = aquaporins

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33
Q

How are RBCs destroyed?

A

Hypertonic + Hypotonic solutions

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34
Q

What are most intravenous solutions?

A

ISOTONIC (0.9& saline + 5% dextrose)

35
Q

What does active transport involve?

A

The expenditure of energy from the hydrolysis of water

36
Q

What is active transport used for?

A

Transport essential ions AGAINST their conc gradient

37
Q

What does active transport help do?

A

Maintain tonicity, volume + charge

38
Q

What is primary active transport?

A

Uses energy from the hydrolysis of ATP

39
Q

What is secondary active transport?

A

Uses energy stored by an ionic conc grad

40
Q

What does ATP change in active transport and how much ATP of a cell is used this way?

A

The shape of the carrier proteins

-40%

41
Q

Give an example of primary active transport?

A

Sodium-potassium pump

42
Q

Why must the sodium-potassium pump work non-stop?

A

Prevent passive leaking

43
Q

Describe the stages of primary active transport?

A

1) 3Na+ bind
2) ATP hydrolysed (ATPase)
3) 2K+ bind / P released
4) 2K+ enter

44
Q

Describe secondary active transport?

A

Where a transporter protein couples the movement of an ion (Na+/H+) DOWN its electrochemical grad (which was made by the primary active transport)

45
Q

What is a symport?

A

Where the molecules travel in the SAME direction

46
Q

What are symports used for?

A

Ca2+ + H+ regulation

47
Q

What is an antiport?

A

Where the molecules go in the OPPOSITE direction

48
Q

What is vesicular transport used for?

A

Endocytosis + exocytosis + inter-organelle transport

BOTH USE ATP

49
Q

Further classify endocytosis?

A

1) receptor mediated endocytosis
2) phagocytosis
3) pinocytosis

50
Q

What is receptor mediated endocytosis used for?

A

The uptake of LDL , vitamins , proteins + hormones

51
Q

What is clathrin?

A

A protein enriching membrane domains

52
Q

Describe the stages of clathrin-mediated endocytosis?

A

1) binding
2) vesicle formation
3) unseating
4) fusion with endosome
5) recycling of receptor
6) degradation in lysosomes

53
Q

Describe phagpcytosis?

A

They engulf large particles (worn out cells/bacteria)

54
Q

What carries out phagocytosis?

A

Macrophages + neutrophils

55
Q

Describe the stages of phagocytosis?

A

1) Chemotaxis + adherence of microbe to phagocyte
2) Ingestion
3) Phagosome formation
4) Fusion of phagosome to lysosome —–> Phagolysosome
5) Digestion by enzymes
6) Residual body formation containing material
7) Discharge of waste materials

56
Q

What is the bulk phase of endocytosis?

A

Pinocytosis

57
Q

Describe pinocytosis?

A
  • small droplets are taken in
  • no receptors needed
  • all solutes in the extracellular fluid are brought in
58
Q

Where does pinocytosis especially occur?

A

Intestines + kidneys

59
Q

Which cells are exocytosis important to?

A
  • Secretory cells (digestive enzymes + hormones)

- Nerve cells (neurotransmitters)

60
Q

What is trancytosis?

A

Combo of endo + exo cytosis

-Substances passed THROUGH cells

61
Q

Where is trancytosis common?

A

Endothelial cells - line the blood vessels

62
Q

Describe the events at the synapse + exocytosis?

A

1) Action potential DEPOLARIZES axon terminal
2) Ca2+ voltage-gated channels open
3) Ca2+ entry triggers EXOCYTOSIS of synaptic vesicle contents
4) Neurotransmitter diffuses across cleft + binds with postsynaptic receptors
5) Binding initiates a response

63
Q

Name the types of junctions?

A
  • tight junctions
  • adherens junctions
  • desmosomes
  • hemidesmosomes
  • gap junctions
64
Q

What do tight junctions do?

A

Prevent the movement of substances through extracellular space between them
e.g. cells lining the digestive tract

65
Q

What do adherens junctions do?

A

Maintain cellular position

66
Q

What do gap junctions do?

A

Allow the movement of substances

67
Q

How are tight junctions formed?

A

Fusion of integral proteins of adjacent cells

68
Q

Is there intercellular space when there is a tight junction?

A

NO

69
Q

What are adherens junctions?

A

Plaques that attaches to membrane proteins + microfilaments

70
Q

What do adherens junctions normally form?

A

Adhesion belts

71
Q

What do adherens junctions do in peristalsis (contractile activities) ?

A

Resist separation

72
Q

What are desmosomes + hemidesosomes?

A

Anchoring junctions held together by LINKER PROTEIN FILAMENTS

73
Q

What are the linker protein filaments called in desmosomes + hemidesmosomes?

A

Cadherins + integrins

74
Q

What is the function of desmosomes + hemidesmosomes?

A

Distribute tension + prevent tearing

e.g. skin + heart muscle

75
Q

What are gap junctions?

A

Where adjacent cells are linked by HOLLOW CYLINDERS (connexons) made of transmembrane proteins

76
Q

Where are gap junctions found?

A

In electrically excitable tissues for synchronization

e.g. heart + smooth cell

77
Q

What is mechanical coupling?

A

When there is a small gap (0.02 micrometres) between the membranes of adjacent cells filled with connective tissue

78
Q

What does mechanical coupling do?

A

Firmly binds 2 adjacent cells together

79
Q

Where are cells bound together more strongly at?

A

Desmosomes

80
Q

What is electrical coupling?

A

The longitudinal segments containing specialized regions where the membrane of the adjacent cells are very close together

81
Q

What is in the nexus (gap junction)?

A

Regular arrays of proteins = connexins

82
Q

What do connexins allow?

A

The formation of large channels allowing the passage of ions + small molecules

83
Q

What are the 2 important roles of intercalated discs?

A

Mechanical + electrical coupling

Alia - Biology (10 decks)

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