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Cell Biology > Lecture 7 > Flashcards

Lecture 7 Flashcards

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1
Q

What is the function of the cell membrane?

A

compartmentalize the cell and form a barrier between extracellular environment and cytoplasm

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2
Q

What are membranes made of?

A

Lipids

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3
Q

What are three properties of membranes?

A
  • stable lipid bilayer which form spontaneously in water
  • Stabilized by hydrophobic interactions
  • low permeability
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4
Q

4 characteristics of liposomes

A
  • are most stable 50-500nm range
  • Larger liposomes break up because of thermo-motion
  • high salt concentrations stabilize liposomes
  • carriers of hydrophilic molecules
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5
Q

What two things form the membrane?

A

Lipids + cholesterol

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6
Q

What does more structure mean within lipid movements

A

less structure = less movement

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7
Q

What 3 things affects lipid fluidity

A
  • temperature
    -unsaturated fatty acids
  • cholesterol
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8
Q

What does it mean for the membranes to be asymmetric?

A

It means the two bilayer are different

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9
Q

What can easily pass though the membrane?

A

Small, non-charged molecules
O2, CO2, N2

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10
Q

Can small uncharged polar molecules pass through the membrane?

A

The permeability of membranes is in part determined by lipid composition, water can move through but no very fast
h2O, ethanol, glycerol

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11
Q

Can larger uncharged polar molecules pass through the cellular membrane?

A

They can, but very slow
Amino acids, glucose, and nucleotides

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12
Q

Can ions pass through the membrane?

A

No
H+, Na+, K+, Ca2+

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13
Q

What is osmolarity?

A

total concentration of all solute particles

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14
Q

What has higher osmolarity, cytoplasm or extracellular space?

A

cytoplasm

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15
Q

What causes turgor pressure?

A

Water pushing into the cell from the cytoplasm, having a higher osmolarity

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16
Q

What allows for fast exchange of water?

A

aquaporins

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17
Q

What keeps the plants “in shape”

A

Turgor pressure

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18
Q

What stabilizes the plasma membrane of mammalian cells

A

cytoskeleton

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19
Q

What is cytosol low in and high in

A

Low in Na+ and Ca2+
High in K+

20
Q

What is the concentration gradient?

A

Higher concentration of molecules on one side of the membrane compared to other side

21
Q

What is membrane potential?

A

Unequal charge distribution across the membrane

22
Q

Concentration gradient + membrane potential = ????

A

Electrochemical gradient

23
Q

What is electrochemical gradient?

A

determines which direction charge solutes will move

24
Q

What are two ways to transport molecules across membranes

A
  1. transporter
  2. Channels
25
Q

What are characteristics of transporters?

A

Contains a central binding site for the molecule/solute. The binding site chances accessibility from one side of the membrane to the other

26
Q

What are characteristics of channels?

A

Channels are selective pores
Channels allow ions to pass membranes
Electrochemical gradient determines the direction of flow

27
Q

What is passive transporter?

A

Follows the concentration gradient

28
Q

What is an active transporter?

A

Works against concentration gradient

29
Q

Describe the alternate access model of transporter function

A
  • central binding pocket is accessible either from the outside or the cytosol
  • glucose transporters can function in both directions and thus follows concentration gradient
30
Q

What is hexokinase?

A

(Converting glucose to glucose-6-phosphate) drives the import forward. The transport across the membrane is passive, by the system uses energy to trap glucose which makes the glucose import an active transport system

31
Q

What drives the ion gradient?

A

ATP

32
Q

Amino acids can be imported or synthesized from what …

A

glucose

33
Q

What are the jobs of ion channels?

A

The selectivity filter allows only specific ions to pass through (no water)

34
Q

Job of the gates in ion channels

A

signal open and close

35
Q

Where is the tetrametric protein complex found?

A

plasma membrane

36
Q

What is the function of the tetrametric protein?

A

pain receptor

37
Q

When is the tetrametric protein activated and what happens?

A

Activated by high temperature or chemicals which causes cations to flux

38
Q

What is a good example of ion channel?

A

neurons

39
Q

What is the job of the neuron?

A

Neurons receive information from other neurons on the dendrites, process the information, and send a signal down the axon to other neurons

40
Q

What are signals neurons use?

A

Changes in membrane potential

41
Q

Action potential = ???

A

a rapid and local change in membrane potential propagating along the membrane of neurons

42
Q

What is synapses?

A

Specialized areas of the neurons that make contact with other cells and deliver a signal to the postsynaptic cell

43
Q

What makes synapses unique?

A

Large number of vesicles present

44
Q

What occurs during step 1 of synaptic activity?

A
  • the action potential from the axon ends up in synapses which include calcium channels
  • the calcium triggers the fusion of synaptic vesicles with the plasma membrane, which release a neurotransmitter
45
Q

What occurs during step 2 of synaptic activity?

A
  • the neurotransmitter diffuses across the synaptic cleft and opens a cation channel in the postsynaptic neuron
  • the influx of cations produces an action potential in the postsynaptic neuron

Cell Biology (18 decks)

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