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BIOSCI 107 > Cell Processes > Flashcards

Cell Processes Flashcards

1
Q

What is the membrane structure?

A

Made out of a polar head and non polar tails (heads are at the outside and the tails are in the inside - tail to tail)

Proteins embedded within.

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2
Q

Describe the membrane structure.

A

A thin 8nm flexible and sturdy barrier that surrounds the cytoplasm of a cell

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3
Q

What model describes the membrane structure?

A

Fluid mosaic model

- Sea of lipids in which proteins float like icebergs

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4
Q

What are the %s of lipid and protein and what are they held together by?

A

50% lipid
50% protein
- held together by H bonds

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5
Q

What do the membrane structure do (lipid)?

A

Lipid is a barrier to entry and exit of polar substances

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6
Q

WHo are the gatekeepers of in the lipid bilayer?

A

Proteins embedded – regulate traffic

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7
Q

Are polar heads hydrophilic/phobic?

A

HydroPHILIC

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8
Q

Describe the lipid bilayer of the cell membrane.

A

2 back to back layers of 3 types of lipid molecules

- Cholesterol and glycolipids scattered among a double row of phospholipid molecules

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9
Q

What determines the different permeability properties of lipid bilayer?

A

Composition of lipids will change between cells give you a type of lipid bilayer which will change their permeability properties.

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10
Q

What are phospholipids comprised of?

A

75% lipids

Amphipathic molecules

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11
Q

What does amphipathic mean?

A

Each molecule is amphipathic meaning have non polar and polar region.

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12
Q

What is the distance between the polar heads in the bilayer?

A

9nm between the polar heads

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13
Q

What is the hydrophobic core?

A

Non polar tails the key which forms the structure the barrier for the permeability of molecules.

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14
Q

Are membrane fluid or rigid?

A

Membranes are fluid and lipids can move around within the plane of the membrane leaflet

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15
Q

How can the lipid composition of the leaflets be asymmetric?

A

Because lipids barely flip flop between membrane leaflets

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16
Q

What is a leaflet?

A

One side of the bilayer (red and white)

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17
Q

What does leaflet assymetric mean?

A

One side is all red and the other is all yellow (cannot mix red yellow in one leaflet)

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18
Q

What are the factors affect the fluidity of the membrane?

A

Lipid tail length
Number of double bonds
AMount of cholesterol

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19
Q

How does lipid tail length affect fluidity?

A

The longer the tail, the less fluid the membrane

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20
Q

How does number of double bonds affect the fluidity?

A

more double bonds, the more fluid the membrane is

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21
Q

How does amount of cholesterol affect fluidity

A

The more cholesterol the more fluid the membrane is.

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22
Q

Integral proteins are…

A

extend into or completely across cell membrane

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23
Q

What is the name of integral proteins which extend completely into the cell membrane?

A

Transmembrane protein

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24
Q

What are some examples of integral proteins and which ones are transmembrane?

A
  1. Integral protein (through only one leaflet)
  2. curly one
  3. channel one
  4. receptor looking one
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25
Q

What are peripheral proteins?

A

attached to either inner our outer surface of cell membrane and are easily removed form it

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26
Q

Why are peripheral proteins easily removable?

A

Break bonds in ionic strength so protein to protein interactions are broken and can remove.

Change the ionic concentration

integral protein acting as anchor

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27
Q

How do you remove integral proteins?

A

Detergent is used to break hydrophobic bonds between the proteins and the lipid.

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28
Q

What are the two types of protein membrane?

A

Peripheral

Integral (inclu. Transmembrane)

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29
Q

Which protein membrane is responsible for cell movement of molecules?

A

Integral protein

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30
Q

Are integral proteins amphipathic?

A

Yea

Have hydrophobic region that span the hydrophobic core of the lipid bilayer

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31
Q

What are hydrophobic regions usually comprised of>

A

Usually consists of non polar amino acids cooilded into helices

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32
Q

What interacts with aqueous solution?

A

Hydrophilic ends of the proteins interact with the aqueous solution

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33
Q

What are the function of membrane proteins?

A 
Receptor protein 
Cell identity markers
Liners
Enzymes 
Ion channels 
Transport proteins
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34
Q

Which molecules can freely move through the cell membrane?

A
  • Non-polar uncharged molecules (O2, N2)
  • lipid soluble molecules (steroids, fatty acids, some vitamins)
  • Small polar molecules (water, urea, glycerol, CO2)
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35
Q

What cannot pass through the membrane?

A
  • Large uncharged polar molecules (glucose, amino acids)

- Small charged ions (K+ Na+ CL- H+)

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36
Q

What is the direction determined by (the movement of the particles)

A

Laws of physics

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37
Q

What is diffusion?

A

Movement of particles/ions down their concentration gradient until the system has reached equilibrium

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38
Q

What affects the rate of diffusion? Difference of conc between the 2 sides:

A

The greater the difference in conc between the 2 sides of the membrane, the faster the rate of diffusion

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39
Q

What affects the rate of diffusion? Increase temp

A

The higher the temperature, the faster the rate of diffusion

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40
Q

What affects the rate of diffusion? larger size of diffusion substance

A

The larger the size of the diffusion substance, the slower the rate of diffusion

41
Q

What affects the rate of diffusion? increase in SA

A

An increase of SA increases the rate of diffusion

42
Q

What affects the rate of diffusion? diffusion distance

A

Increasing the diffusion distance, slows the rate of diffusion

43
Q

What are the physical consequences of diffusion in cells?

A
  • Rate of diffusion sets limit on size of the cells (20um)
  • If you want increase diffusion, cell must increase the membrane area available for exchange (diffusion) of substance
  • Membrane thickness, the thicker the membrane the slower the rate of diffusion
  • DIffusion is very fast over small distances
44
Q

What are the 2 main types of gradients?

A

Concentration gradient

Electrical gradient

45
Q

What is electrical gradient?

A

Ions influenced by the membrane potential in addition to their concentration gradient

46
Q

What is concentration gradient?

A

Non charged molecules will diffuse down their concentration gradients

47
Q

What influences the movement of ions?

A

The electrochemical gradient

48
Q

Molecules is to which gradient?

A

CONCENTRATION

49
Q

Ions is to which gradient?

A

ELECTRICAL

50
Q

What are ion channels?

A

Are water-filled pores that span the hydrophobic core of the lipid bilayer

51
Q

What do ion channels allow the passage of?

A

small molecules and passage of ions across the cell membrane

52
Q

Do ions bind to the channel pore?

A

No they do not bind to the channel pore so transport can be very rapid

53
Q

By rapid ion passage, how fast is it?

A

1 million ions per sec

54
Q

What lines the ion channels?

A

Amino acid lines the pore

55
Q

What is special about the amino acids lining the pore?

A

It determines the permeabilty of the channel ions

56
Q

What does ion channel being selective mean?

A

channel can harness the energy stores in different ion gradients

57
Q

What are the two types of transmembrane transport?

A

Mediated and non-mediated

58
Q

What does mediated transmembrane protein mean?

A

It needs proteins

59
Q

What is non mediated membrane importont for?

A

for the absroption, excretion of wastes

60
Q

Which types of molecules can cross non-mediated>

A

many small hydrophobic molecules including O2, CO2, N, fatty acids, steroid etc

61
Q

What is an example of ion channels?

A

Na+K+ pump

62
Q

What do the gated channels look like?

A

The have a gate which looks like a ball and chain.

63
Q

What can affect the opening and closing of the gate in an ion channel?

A

Different stimuli:

  1. Voltage
  2. Ligands bind
  3. Cell volume (stretch)
  4. pH
  5. Phosphorylation
64
Q

Diffusion of ions through a channel can generate what>

A

A current across the cell membrane

65
Q

How can we measure the individual channel’s current activity>

A

Through the patch and clamp technique. `

66
Q

What does current fluctuation mean?

A

They rep the opening and closing of a single ion channel, the conformation changes in channel structure that are associated with channel gating

67
Q

What an carrier mediated transport be? A or P?

A

Active or facilitated dpassive diffusion

68
Q

Ar etransport rates slowere that those obtained for in channels?

A

Ya

69
Q

What other thing/traits have similar charctaeristics to transporters?

A

Enzymes but do not catalyse

70
Q

What do transoprt prtoeins do?

A

They mediate transport across cell membrreane at faster than normal rate.

71
Q

What do transporters exhibit?

A

Specifity
Inhibition
Competition
Saturation

72
Q

What is facilitaed diffusion ?

A

Mediated passive transport (no ATP)( down a conc gradient

73
Q

What is an example of facilitated diffusion?

A

GLUT glucose binds to transport protein GLUT

74
Q

What happens when glucose binds to GLUT the transport protein?

A

GLUT changes shape and glucose moves across the cell membrane but ONLY DOWN CONC GRAD

75
Q

What is important about glucose reducing glucose?

A

Kinase enzymes reduce glucose concentration by cinverting into glucose–phosphate.

76
Q

Why does kinase enzyme reduce glucose into glucose-6-phosphate?

A

Maintains the concentration gradient for continued glucose absorption

77
Q

What is Active transport?

A

Using ATP to drive substances AGAINST their ELECTROCHEMICAL POT. GRAD

78
Q

What are the two forms of active transport?

A

Primary and Secondary

79
Q

What is primary AT?

A

Energy is directly derived from the hydrolosis of ATP

80
Q

What is secondary AT?

A

energy relased bu a substance diffusing down conc grad used to activley transortr another substance against their conc grad

81
Q

How much % do cells use energy for primary AT?

A

30%

82
Q

What is an example of primary tAT?

A

Na/K - maintains a low conc of Na+ in cell and high K in cytosol

83
Q

What are the numbers of Na+ and K+

A

3 Na+ is pumped out of the cell and 2 K+ get into the cell

84
Q

What does the Na?K pump generate?

A

A net current and is elctrtogenic

85
Q

What is the importance of generating different ion conc from the Na/K pump?

A

Maintence of the restign membrane potential

Electrical excitabiltiy

Maintence of steady cell volume

Uptake of nutrients vis secondary AT

maintence of intra cellular pH by secondary AT

86
Q

How is secondary AT?

A

Because of the low conc of Na in the cell, througha symporter, the Na from out of the cell in lumen is going down its conc gradient into the cell but it moves glucose with it which is going against its conc gradient.

87
Q

In passive diffusion, what are the ways it can diffuse?

A

Through the lipid

facilitated/mediated

carrier mediated (pac man looking thing, glucose kinase enzymatic)

88
Q

In Active diffusion what are the types of it can diffuse?

A

Ligand gated channel

Carrier-mediated

89
Q

Example of primary AT

A

NA/K (making the electrochemical gradient for secondary AT)

90
Q

Example of secondary AT

A

They use the gradient of primary which they created and they move like glucose with Na to the inside of the cell

91
Q

What are epithelial tissues seperated by?

A

Their neighbours by lateral intercellular space,

92
Q

What are epitheliat tissues joined up with?

A

held by lumical edges; tight junctions

93
Q

How can transport in epithelia occur?

A

paracellular or transcellular

94
Q

WHat is paracellular?

A

via tight junction

95
Q

What is intercellular?

A

through the cell

96
Q

What is paracellular governed by?

A

the laws of diffusion and the tightness og the TJ

97
Q

What can be measured in paracellular through TJ?

A

electrical resistance to ion flow through the TJ can be measured.

The higher the electrical resistance to ion flow, the greater the number of TJ strands holding the cell together

98
Q

Epithelial cells use primary and secondary transport often with passive diffusion through ion channels to produce transport across epithelial cells

A

Absroption:Lumen to blood
Secretion: blood to lumen

BIOSCI 107 (8 decks)

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