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BIOLOGY 204 > UNIT 5 MEMBRANES AND TRANSPORT > Flashcards

UNIT 5 MEMBRANES AND TRANSPORT Flashcards

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1
Q

Plasma membrane

A

Is selectively permeable that allows the uptake of key nutrients and the elimination of waste.

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2
Q

What is consisted a plasma membrane

A

lipid bilayer

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3
Q

What is the fluid mosaic model of membranes?

A

Consist of fluid lipid molecules wit proteins that are embedded and float freely.

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4
Q

Bilayer

A

Double layer of lipids with heads facing out and tails facing in.

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5
Q

Evidence of the fluid mosaic model?

A
  • Membranes are fluid

- membrane asymmetry

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6
Q

Experimental evidence of the fluid mosaic model?

A
  • They fused human and mouse cells each dyed with different colours and they began mixing. (membrane fluidity)
  • Froze a block of cell and fractured it, were able to split the bilayer and see that both sides have molecules from different shape, size and number. (membrane asymmetry)
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7
Q

Dominant liquids in membrane

A

phospholipids

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8
Q

phospholipids

A

2 fatty-acids tails linked to 1 type of alcohol or amino-acids by a phosphate group.

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9
Q

Amphipatic bilayer

A

each phospholipid molecule contains a hydrophobic and hydrophilic region.

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10
Q

Membrane fluidity is influenced by

A

How tightly the individual lipid molecule can pack togheter.

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11
Q

How tightly individual lipid molecule can pack tighter depends on?

A

the composition of the lipid molecules that makes up the membrane and the temperature.

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12
Q

composition of lipid molecules that make up the membrane (fluidity of membrane)

A
  • Saturated hydrocarbons have a straight shape which allows them to be close together.
  • Unsaturated hydrocarbons have double bonds which introduces bends in the structure. Not packed as tightly together.
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13
Q

Temperature (fluidity of membrane)

A

-Low temp: phospholipid molecules pack closely together and creates a gel like membrane.

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14
Q

Organisms can adjust their fatty acid composition by

A

By producing unsaturated fatty-acids produced by the fatty-acids synthesis with the action of desaturases.

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15
Q

Desaturases

A

Removes 2 hydrogen atoms from a saturated fatty-acid and giving it a double bond. Which makes it unsaturated.

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16
Q

More desaturases when?

A

When the temperature is low, increasing the abundance of unsaturated fatty-acids.

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17
Q

Sterols

A

influence membrane fluidity in animal membranes

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18
Q

How do sterols work?

A

Act as a membrane buffer

  • at high temp. they restrain the movement of lipid molecules, reducing the fluidity of the membrane.
  • low temp. disrupt fatty-acids from associating by taking the space between lipid molecules. slowing the transition to the gel state.
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19
Q

4 function of membrane proteins

A
  • transport
  • enzymatic activity
  • signal transduction
  • attachment recognition
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20
Q

Membrane protein function of transport:

A

Can provide a hydrophilic channel to allow movement of a specific compound in or out of the membrane. Can also change its shape to shuttle a molecule in or out

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21
Q

Membrane protein function of enzymatic activity

A

A number of enzymes are membrane proteins

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22
Q

Membrane protein function of signal transduction

A

Membranes often have receptor proteins that binds to specific chemicals such as hormones.It triggers changes on the inside surface of the membrane, transducting the signal through the cell.

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23
Q

Membrane protein function of attachment recognition

A

Act as attachment point for a bunch of cytoskeleton elements.

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24
Q

Membrane proteins can be classified in two type

A

Integral membrane proteins and peripheral membrane proteins.

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25
Q

Integral membrane proteins

A

Are imbedded in the phospholipid bilayer.

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26
Q

Most type of integral membrane proteins

A

transmembrane proteins

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27
Q

Transmembrane proteins

A

Span from one side to the other of the membrane. They are a stretch of 17-20 hydrophobic amino-acids.

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28
Q

Peripheral membrane protein

A

On the surface of membrane, doesn’t interact with the hydrophobic core of the membrane. They are mostly on the cytoplasmic side and some are part of the cytoskeleton.

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29
Q

How are peripheral membrane proteins held on the membrane?

A

By hydrogen and ionic bonds

30
Q

Passive transport

A

Based on diffusion, movement of a substance across a membrane without the need of ATP.

31
Q

Diffusion

A

Movement of a substance from a region of higher concentration to a region of low concentration.

32
Q

Diffusion facts

A

Works to increase entropy. The bigger concentration gradient, the faster rate of diffusion.

33
Q

2 types of passive transport

A

simple and facilitated

34
Q

Simple diffusion

A

The size and charge of molecules determines if it can diffuse through a membrane.

35
Q

Facilitated diffusion

A

Protein complexes help speed up the transport of polar and charged molecules. When the gradient falls to 0, the transport stops.

36
Q

Passive transport energy source

A

concentration gradient

37
Q

Proteins that do facilitated diffusion

A

Channel proteins and carrier proteins

38
Q

Channel proteins

A

Form hydrophilic pathway in the membrane in which ions and water can pass. Most of them are gated channels, which switch between open, closed or intermediate states.

39
Q

Carrier proteins

A

Binds to a specific solute and transports it across the membrane. Undergoes many conformation changes to do it, the transport is faster but it reaches a plateau when all transporters are occupied.

40
Q

Osmosis

A

Diffusion of water only.

41
Q

Aquaporins

A

Water- specified transport proteins that facilitates osmosis.

42
Q

Hypotonic

A

In osmosis, when the solution around the cell has lower concentration substances than in the cell.

43
Q

Hypertonic

A

In osmosis, the solution around the cell has more concentration than in the cell. Must constantly expend energy to replace the water lost.

44
Q

Isotonic

A

Concentration on both sides are the same.

45
Q

Active membrane transport

A

Substances pushed against their concentration gradient by active transport pumps.

46
Q

Does active membrane transport need energy?

A

Yes, it uses 25% of the cells ATP

47
Q

2 types of active membrane transport

A

primary and secondary

48
Q

Primary active transport

A

The same protein that transport the substance also hydrolyses ATP to power that transport.

49
Q

Secondary active transport

A

Transport is indirectly driven by ATP hydrolysis. Transporter use a favorable concentration gradient of ions as their energy source for the transport of another molecule.

50
Q

Primary active transport moves what?

A

Positively charged ions

51
Q

Pumps in primary active transport

A

H+, Ca2+, Na+/K+

52
Q

H+ pump

A

Push hydrogen ions from the cytoplasm to the cell exterior.

53
Q

Ca2+ pump

A

Pushed Ca from the cytoplasm to the cell exterior and from the cytosol to the ER.

54
Q

Na+/K+ pump

A

Pushes 3 N ions out and takes 2 ions in at the same time. So positive charges accumulates on the outside while the inside becomes negatively charged.

55
Q

Electrical potential difference

A

In Na+/K+ pumps, when the inside and outside have different charges. It creates a voltage

56
Q

Membrane potential

A

Voltage across a membrane (Na+/K+ pump)

57
Q

Electrochemical gradient

A

Difference in voltage and gradient across the membrane.

58
Q

Secondary active transport moves what?

A

ions and organic molecules. The transfer of the solute is always coupled with the ion supplying the driving force.

59
Q

Symport

A

solute moves through the membrane in the same direction as the ion. Known as cotransport.

60
Q

Antiport

A

Ion moves through in one direction, providing the energy for the transport of another molecule in the opposite direction. Known as exchange diffusion

61
Q

Transport of bigger molecules

A

endocytosis, exocytosis. Both requires energy.

62
Q

Exocytosis

A

Export waste with secretory vesicles. The vesicles fuse with the plasma membrane and releases it’s contents to the exterior.

63
Q

Endocytosis

A

Import proteins and larger molecules, enven whole cells.The substances are trapped in puttylike depression that bulge inward from the plasma membrane.

64
Q

2 pathways of endocytosis

A

Pinocytosis (bulk-phase) and phagocytosis.

65
Q

Pinocytosis

A

extracellular water is taken as well as any molecules in the solution. just takes everything.

66
Q

Phagocytosis

A

The molecules to be taken in depends on the receptor proteins on the outer cell surface. Receptors collect in the plasma membrane to form a coated pit because of a protein called Clathrin, once in the cytoplasm it loosed the clathrin and fuses with a lysosome where it digest the contents into useable molecules.

67
Q

Hydrophilic has which charge?

A

polar

68
Q

hydrophobic has which charge?

A

non-polar

69
Q

Phospholipids assemble into a bilayer because of

A

their amphipathic nature

70
Q

The bilayer has what energy state?

A

low

71
Q

The interior of the bilayer is

A

hydrophobic

72
Q

aquaporins functions by

A

forming a channel to facilitate the rapid diffusion of water.

BIOLOGY 204 (9 decks)

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