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BB10005- Cell Biology > Lec 4 (membrane 1) > Flashcards

Lec 4 (membrane 1) Flashcards

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1
Q

Membranes

A

are barriers/define boundaries

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2
Q

Pros have what type of membranes

A

Single membrane (no membrane bound organelles)

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3
Q

Eus have what type of membranes?

A 
plasma membrane (outside) 
- membrane bound organelles (intracellular)
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4
Q

Barrier function (4)

A

1) Prevents loss of required metabolites
2) Protects against unwanted outside molecules (disease)
3) Capacitor function: stores electrical chemical energy (enables a ion gradient)
4) Important for energy production and electrical signalling

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5
Q

Importation and exportation?

A

Cells need import and export molecules

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6
Q

Importation and exportation tends to be carried about by?

A

Intergral membrane proteins

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7
Q

Intergral membrane proteins definition?

A

Set of proteins which give the membrane is properties

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8
Q

Example of exportation in mammalian cells?

A

Insulin in order to control glucose conc

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9
Q

Receptors function?

A

receiving information (cell signalling)

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10
Q

Functions of membrane proteins? (8)

A

Selective permeability
Maintaining ionic composition on either side
Maintaining cytoplasmic pH
Controlling cytoplasmic osmotic pressure
Sensing the environment: receptors
Anchoring cytoskeletal structures
Mediating cell/cell and cell extracellular matrix interactions
Carrying out membrane requiring enzymatic reactions

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11
Q

Usual pH inside cells?

A

7.2

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12
Q

Membrane surrounding outside?

A

Plasma membrane

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13
Q

Which cell has the lowest amount of plasma membrane?

A 
Liver cell, 2% 
internal membrane (rest)
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14
Q

Lysosome contains

A

hydrolytic enzymes/hydrolases

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15
Q

Lysosome pH

A

pH 5

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16
Q

How thick is the lipid bilayer ?

A

5nm

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17
Q

Amphipathic

A

have both hydrophobic and hydrophilic components

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18
Q

Lipids when added to water

A

will spontaneously arrange themselves

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19
Q

The bilayer is

A

thermodynamically favourable

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20
Q

how many nm is 1mm

A

1 000 000

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21
Q

Bilayer is what shape?

A

Plannar

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22
Q

How do liposomes form?

A

It is energetically favourable for lipids to form sealed compartments. With a sealed compartment there are no hydrophobic ‘edges’ in contact with water. (circular)

23
Q

Glycerophospholipids other name?

A

Phosphoglycerides

24
Q

3 Carbon backbone

A

glycerol

25
Q

3rd chain in glycerophospholipids?

A

phosphate and x group which can vary between each. Giving different properties

26
Q

R (fatty acid hydrocarbon chain) number

A

Varys which each usually r1 and r2 are different

27
Q

When x= serine

A

phosphatidyl serine
^ “ for each
acidic due to positively charged serine

28
Q

Sphingoldlipids

A

sugars attached to lipids» phospholipid

Also have variable c (classed as phospholipids)

29
Q

Sterols example in membranes

A

cholesterol

30
Q

Lipid bilayers are

A

fluid

31
Q

Lipids within the bilayer can

A

rotate freely

32
Q

flip flop mechanism?- when and if it occurs, limitations

A

Hydrophilic head through a hydrophilic environment (not energetically favourable, but does occur sometimes eg protein mediated)

33
Q

Why is membrane fluidity important?

A
  • allows for interactions to take place

- E.G groups of membrane assembling at particular sites within the membrane

34
Q

Why is the fluidity of the membrane perfect for its function?

A

provides the perfect compromise between ridged and ordered, and fluid and non viscous

35
Q

Experiment which demonstrated membrane fluidity?

A

cell fusion between two cells. One of which contained a rhodamine labelled membrane protein and the other containing a flouresein labelled membrane protein. The two cells were fused, to form a hybrid.

after 40 minutes, incubated at 37 degrees»»> equally distributed within a cell

36
Q

Factors influencing membrane fluidity (no reasons)

A
  • Temperature (in exotherms)
  • Saturation of acyl chains
  • Length of acyl chains
  • Cholesterol
37
Q

Temperature factor (increasing membrane fluidity)

A

only applies to exotherms (don’t control their body temperature, relies on its environment)

38
Q

How does saturation of acyl chain effect membrane fluidity?

A

if unsaturated= kink in chain (double c=c) increases the fluidity of the membrane as the lipids are further apart, and therefore experience less van Der Waals interactions

Vice versa for saturated.

39
Q

Cholesterol?

A

decreases membrane fluidity, therefore mobility. Increases the rigidness of it

40
Q

Lipid asymmetry is described by?

A

Lipid distribution not being random.

41
Q

Leaflet

A

One layer of the bilayer

42
Q

Usually negative phospholipids are restricted to the cytoplasmic leaflet unless?

A

Apoptosis, lipid asymmetry begins to breakdown and we start to see negatively charged phospholipids on the extracellular leaflet.

43
Q

Orientation is maintained?

A

During budding and fusion (planar)

44
Q

Lipid compositions are ??

A

Different on different membranes&raquo_space;>. functional consequences

45
Q

Why are there so many different lipids?+ examples

A

Due to their many different functions

  • biological effects: curvature, fusion, fluidity
  • Can act as signalling molecules
  • Cell interactions (exportation/importation)
  • Effect the activity of membrane proteins
46
Q

Lipid bilayers are permeable and impermeable to? examples of each

A 
permeable to:Small hydrophobic
molecules (02, n2), Small uncharged 
Polar molecules (h20, glycerol)

Impermeable to: Larger uncharged (amino acids, glucose nucleotides)
Polar molecules, and ions (H+ Na+ etc)

47
Q

Types of membrane protein

A

Integral membrane proteins
Peripheral membrane proteins
Lipid anchored membrane proteins

48
Q

Intergral membrane proteins cover?

A

Entire length of the bilayer (domains on either side of the membrane)

49
Q

Peripheral

A

Lipid associated

50
Q

Lipid anchored membrane proteins

A

Lipid linked

51
Q

If you wash cells in high salt?

A

Peripheral aren’t removed due to non covalent interactions in which are occurring.

52
Q

What percentage of ORF’s (Protein coding genes) in genomes are predicted to encode membrane proteins

A

20-30

larger genomes contain a larger fraction than smaller ones

53
Q

How many structures of membrane protein are known at high resolution? By which method Is this information derived?

A

300

via x-ray crystallography

BB10005- Cell Biology (6 decks)

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