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BIOL1090 > Lecture 15: Membranes > Flashcards

Lecture 15: Membranes Flashcards

1
Q

Functions of the biological membranes are? (6)

A
  1. Define cell boundary - PM specific
  2. Define enclose compartments
  3. Control movement of material into and out of cell/organelles - PM specific
  4. Allow response to external stimuli. - PM specific
  5. Enable interactions between cells - PM specific
  6. Provide scaffold for biochemical activities
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2
Q

Biological membranes are _______ structures

A

Semi-permeable
(Control what goes in and out)

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3
Q

Energy production is done by which two organelles?

A

Mitochondria and chloroplast (photosynthesis)

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4
Q

Biological membranes are ________ structures

A

Trilaminar (3 layers)

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5
Q

Membranes are _____

A

Lipid bilayers

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6
Q

The lipid bilayer is made up of?

A

Phospholipids

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7
Q

In the phospholipid bilayer, there are many ____ embedded

A

Proteins

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8
Q

Fluid mosaic model is?

A

Fluid - components are mobile
Mosaic - diverse proteins, carbs, cholesterol, components can interact

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9
Q

Outer leaflet faces?

A

Exterior of the cell

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10
Q

Inner leaflet faces?

A

Cytosol, or inside of the structure

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11
Q

Biological membranes consist of ?

A

Outer leaflet and Inner leaflet

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12
Q

Phospholipid structure consists of?

A

Glycerol backbone bound by two non-polar fatty acrylic molecules (FA chains) and a polar head group linked by phosphate residue

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13
Q

Phospholipids are amphipathic..?

A

Hydrophilic - attracted to water
Hydrophobic - repelled by water

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14
Q

Hydrophilic part of phospholipid is?

A

Polar head

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15
Q

Hydrophobic part of phospholipid is?

A

FA tails

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16
Q

Types of phospholipids with different heads (4)

A

Ethanolamine
Choline
Serine
Inositol

17
Q

If thrown in water, phospholipids will…?

A

Spontaneously aggregate to bury their hydrophobic tails in the interior and expose their hydrophilic heads to the water

18
Q

Where do phospholipids come from?

A

Synthesis occurs in multistep process at cytosol and outer endoplasmic reticulum membrane - ER membrane contains all enzymes for synthesis and distribution

19
Q

What are the three classes of membrane proteins?

A
  1. Integral
  2. Peripheral
  3. Lipid-anchored
20
Q

Membrane protein - Integral

A

Span the lipid bilayer, parts of proteins exposed to one side of membrane and another part that is also on the other side, (sticks out of both side), can be transport proteins

21
Q

Membrane proteins - Peripheral

A

Associate with surfaces of the lipid bilayer, do not interact with the membrane itself but interact with other proteins or other objects integrated in the membrane itself

22
Q

Membrane proteins - Lipid anchored

A

Attach to a lipid in the lipid bilayer, integrate into one of the leaflets

23
Q

Functions of membrane proteins (3)

A
  1. Transport of nutrients and ions
  2. Cell-cell communication (gap junction) (pores)
  3. Attachment
24
Q

Dynamic of plasma membrane

A

(Lateral shift) Lipids move laterally, easily, within leaflet
(Transverse diffusion) Lipids movement between leaflets is difficult and slow

25
Q

Dynamics of proteins in the biological membranes

A

Diffuse within the bilayers, movement is restricted, diffusion is slow, rapid movement is spatially limited
Modifications to allow proteins to move

26
Q

Structure of biological membranes (4)

A
  • 6nm thick
  • Stable
  • Flexibke
  • Capable of self assembly
27
Q

Biological membrane - mitochondria

A
  • inner membrane of mitochondria have very high concentration of proteins to make ETC and ATP synthesis
28
Q

Biological membrane - neuronal cells

A
  • myelin sheath - consists of layers of plasma membrane wrapped around neurons axon, provides insulation and increases speed
  • myelin sheaths have ow amounts of protein
29
Q

Symmetry of biological membranes is _______

A

Asymmetrical

30
Q

The two leaflets of a membrane are _____

A

Distinct

31
Q

Leaflet distinction

A
  • Distinct lipid composition
  • Outer leaflet contains glycolipids and glycoproteins (sugar molecules)- attach to proteins and phospholipids
  • Glycolipids and glycoproteins - tells cell where to move to, glycosylation event, allows proteins to binds and perform certain functions
32
Q

How does temperature affect the fluidity of biological membranes? (2)

A
  • warming increases fluidity - fluid like
  • cooling decreases fluidity - gel
33
Q

Membrane fluidity is determined by nature of _____ in membrane

A

Lipids

34
Q

(Double bonds - Kinks) Unsaturated lipids ____ _____

A

Increase fluidity

35
Q

(Single bonds) Saturated lipids _____ ______

A

Reduce fluidity

36
Q

Balance between rigid and disordered structure allows (3)

A
  • mechanical support and flexibility
  • membrane assembly and modification
  • dynamic interactions between membrane components
37
Q

What modulate membrane fluidity?

A

Cholesterol

38
Q

How does cholesterol regulate membrane fluidity?

A
  • bidirectional
  • at high temp, stabilizes membrane and raises melting point
  • at low temp, intercalates between phospholipids and prevents from clustering together and stiffening
39
Q

Cholesterol impacts (3)

A
  • alter packing and flexibility of lipids
  • if added to a liquid crystal membrane, fluidity will decrease
  • if added to crystalline gel membrane, fluidity will increase

BIOL1090 (11 decks)

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