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Medicine 1 COPY > Membranes and Lipids > Flashcards

Membranes and Lipids Flashcards

1
Q

Which membrane type consists of the greatest percentage of cell membranes in a cell in liver hepatocytes or liver exocrine cells

A

rER

Plasma is only 2%/5%

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2
Q

Does the plasma membrane consist a majority of a cell’s membrane content?

A

no lol

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3
Q

What is a membrane lipid bilayer permeable/impermeable to

A

permeable to:

  • Small Hydrophobic Molecules (e.g. O2)
  • Small Uncharged polar molecules (H2O, Ethanol)

Impermeable to:

  • Large uncharged polar molecules (e.g. amino acids, glucose)
  • Ions (e.g. H+, Cl-)
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4
Q

Hydrophobic Lipid Bilayer Rough Thickness

A

5-8nm

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5
Q

Integral Proteins

A

Membrane Spanning Protein

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6
Q

Peripheral Proteins

A

Protein attached to Membrane

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7
Q

Layer of associated carbohydrates on membranes

A

Glycocalyx

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8
Q

How are glycocalyxes attached to membranes

A

Via glycoproteins or glycolipids

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9
Q

Nature of all membrane lipids (in terms of attraction to water)

A

Amphipathic

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10
Q

Micelles

A

The formation of a spherical monolayer by membrane lipids

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11
Q

Saturated Fatty Acids

A

No Double Bonds

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12
Q

Two Main Types of Lipids in Membranes

A

Phospholipid
- Contains phosphate group in hydrophilic part

Glycolipid
- Contains covalently attached carbohydrate

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13
Q

How are phospholipids joined

A

Via a phosphodiester linkage

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14
Q

3 Classes of Membrane Lipids

A
  • Phosphoglycerides (Phospholipid)
  • Sphingolipids (Phospho- or Glyco- Lipid)
  • Cholesterol (Sterol)
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15
Q

Describe the vague structure of a phosphoglyceride

A

Fatty acids Esterified to glycerol backbone

Phosphate attached to position 3 of glycerol

Phosphate head is hydrophilic

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16
Q

How do phosphoglycerides vary

A

The hydrophilic head groups generally differentiate them

17
Q

Most prominently occurring phosphoglyceride

A

Phosphatidylcholine

**Lecithin

18
Q

Sphingolipids

A

A simple fatty acid joined to sphingosine (Fatty Amine)

Can be phosholipid or glycolipid

Has 2 Hydrophobic tails; one fatty acid residue (R) and one from fatty acid tail

19
Q

Where are sphingolipids found

A

Often prominent in neuron membranes

**Sphingomyelin found in myelin sheaths

20
Q

Purpose of sphingolipids

A

Not really known

21
Q

What percentage of membranes does cholesterol account for

A

Around 10%

22
Q

Why is vegan diet cholesterol free

A

Plant membranes use phytosterols not cholesterol

23
Q

How does cholesterol maintain fluidity

A

Ring structure is very rigid so the fatty acids that it attracts are held but other parts are not held and this promotes fluidity

24
Q

What is more prominent in outer membrane leaflet

A

Phosphatidylcholine and Sphingomyelin

**DONT MEMORISE

25
Q

What lipid is more prominent in inner membrane leaflet

A

Phosphatidylserine and Phosphatidylethanolamine

**DONT MEMORISE

26
Q

What phosphoglyceride has a negative charge

A

Phosphatidylserine (Thought to affect membrane potential)

27
Q

What membrane lipid has a high proportion in the golgi membrane

A

Phosphatidylcholine

**Relevant in how it affects plasma membrance concentrations

28
Q

What membrane lipid has a high proportion in transport vesicles

A

Sphingolipids & Cholestrol

**Relevant in how it affects plasma membrance concentrations

29
Q

Why do sphingomyelin and cholesterol stay in lipid microdomains/lipid rafts

A

To produce a microdomain enriched with proteins and that signalling pathways that must interact together so when their processes are kicked off they can occur much more rapidly

30
Q

Role of Flippase

A

Moving phospholipids from outer to cytosolic leaflet

** Inwards

31
Q

Role of Floppase

A

Moving phospholipids from cytosolic to outer leaflet

** Outwards

32
Q

Membranes can vary significantly in content, some can have more proteins than lipids (e.g. bacteria) (fyi)

A

yeah what she said

33
Q

Why are myelin sheaths primarily lipids

A

Since this is needed to maintain their role as an electrical insulator

34
Q

State of Membrane when below physiological temperature

A

Semi-Solid Liquid-ordered state

35
Q

State of Membrane when above physiological temprature

A

Liquid disordered state

36
Q

How to avoid membrane entering liquid disordered state (and vice versa)

A

Increasing ratio/amount of cholesterol molecules (and vice versa)

37
Q

How can peripheral proteins be released from membranes

A

Ionic solvents

38
Q

What can enzymes on membranes do

A

They can synthesise other membrane proteins

39
Q

Role of glycocalyx

A
  • Protecting cell from digestion
  • Preventing the uptake of hydrophobic compounds
  • Cell Recognition

Medicine 1 COPY (88 decks)

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