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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
Describe the passive transports in context?
- Diffusion through lipid bilayer - Channel mediated facilitated diffusions - Carrier mediated facilitated diffusion
26
What is the equilibrium potential?
The potential gradient across the membrane to maintain concentration gradient
27
Describe the different types of channel mediated facilitated transport?
Can be gated i.e. voltage/ligand | Can be times i.e. signal regulated
28
What are carrier molecules subjected to?
Transport maximum + saturation
29
How is the hormone insulin regulated?
Its receptor , up-regulates glucose transporters
30
What do diabetic patients lack?
The ability to up-regulate GluT
31
What is osmosis?
The diffusion of water through a SEMI-PERMEABLE membrane
32
Diffusion through the lipid bilayer occurs through what?
Specific transmembrane proteins = aquaporins
33
How are RBCs destroyed?
Hypertonic + Hypotonic solutions
34
What are most intravenous solutions?
ISOTONIC (0.9& saline + 5% dextrose)
35
What does active transport involve?
The expenditure of energy from the hydrolysis of water
36
What is active transport used for?
Transport essential ions AGAINST their conc gradient
37
What does active transport help do?
Maintain tonicity, volume + charge
38
What is primary active transport?
Uses energy from the hydrolysis of ATP
39
What is secondary active transport?
Uses energy stored by an ionic conc grad
40
What does ATP change in active transport and how much ATP of a cell is used this way?
The shape of the carrier proteins | -40%
41
Give an example of primary active transport?
Sodium-potassium pump
42
Why must the sodium-potassium pump work non-stop?
Prevent passive leaking
43
Describe the stages of primary active transport?
1) 3Na+ bind 2) ATP hydrolysed (ATPase) 3) 2K+ bind / P released 4) 2K+ enter
44
Describe secondary active transport?
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
What is a symport?
Where the molecules travel in the SAME direction
46
What are symports used for?
Ca2+ + H+ regulation
47
What is an antiport?
Where the molecules go in the OPPOSITE direction
48
What is vesicular transport used for?
Endocytosis + exocytosis + inter-organelle transport | BOTH USE ATP
49
Further classify endocytosis?
1) receptor mediated endocytosis 2) phagocytosis 3) pinocytosis
50
What is receptor mediated endocytosis used for?
The uptake of LDL , vitamins , proteins + hormones
51
What is clathrin?
A protein enriching membrane domains
52
Describe the stages of clathrin-mediated endocytosis?
1) binding 2) vesicle formation 3) unseating 4) fusion with endosome 5) recycling of receptor 6) degradation in lysosomes
53
Describe phagpcytosis?
They engulf large particles (worn out cells/bacteria)
54
What carries out phagocytosis?
Macrophages + neutrophils
55
Describe the stages of phagocytosis?
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
What is the bulk phase of endocytosis?
Pinocytosis
57
Describe pinocytosis?
- small droplets are taken in - no receptors needed - all solutes in the extracellular fluid are brought in
58
Where does pinocytosis especially occur?
Intestines + kidneys
59
Which cells are exocytosis important to?
- Secretory cells (digestive enzymes + hormones) | - Nerve cells (neurotransmitters)
60
What is trancytosis?
Combo of endo + exo cytosis | -Substances passed THROUGH cells
61
Where is trancytosis common?
Endothelial cells - line the blood vessels
62
Describe the events at the synapse + exocytosis?
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
Name the types of junctions?
- tight junctions - adherens junctions - desmosomes - hemidesmosomes - gap junctions
64
What do tight junctions do?
Prevent the movement of substances through extracellular space between them e.g. cells lining the digestive tract
65
What do adherens junctions do?
Maintain cellular position
66
What do gap junctions do?
Allow the movement of substances
67
How are tight junctions formed?
Fusion of integral proteins of adjacent cells
68
Is there intercellular space when there is a tight junction?
NO
69
What are adherens junctions?
Plaques that attaches to membrane proteins + microfilaments
70
What do adherens junctions normally form?
Adhesion belts
71
What do adherens junctions do in peristalsis (contractile activities) ?
Resist separation
72
What are desmosomes + hemidesosomes?
Anchoring junctions held together by LINKER PROTEIN FILAMENTS
73
What are the linker protein filaments called in desmosomes + hemidesmosomes?
Cadherins + integrins
74
What is the function of desmosomes + hemidesmosomes?
Distribute tension + prevent tearing | e.g. skin + heart muscle
75
What are gap junctions?
Where adjacent cells are linked by HOLLOW CYLINDERS (connexons) made of transmembrane proteins
76
Where are gap junctions found?
In electrically excitable tissues for synchronization | e.g. heart + smooth cell
77
What is mechanical coupling?
When there is a small gap (0.02 micrometres) between the membranes of adjacent cells filled with connective tissue
78
What does mechanical coupling do?
Firmly binds 2 adjacent cells together
79
Where are cells bound together more strongly at?
Desmosomes
80
What is electrical coupling?
The longitudinal segments containing specialized regions where the membrane of the adjacent cells are very close together
81
What is in the nexus (gap junction)?
Regular arrays of proteins = connexins
82
What do connexins allow?
The formation of large channels allowing the passage of ions + small molecules
83
What are the 2 important roles of intercalated discs?
Mechanical + electrical coupling

Alia - Biology (10 decks)

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