NEUR201 > Lecture 3 > Flashcards

Lecture 3 Flashcards

(44 cards)

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1
Q

How many cells in a human body

A

~10^4

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2
Q

What is the relative composition of ECF

A
  • high in Sodium
  • low in potassium
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3
Q

What is the relative composition of ICF

A
  • low in sodium
  • high in potassium
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4
Q

What is the cell membrane composed of

A

Phospholipids

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5
Q

What portion of the cell membrane is hydrophobic

A

Lipid portions

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6
Q

Why do we need a cell membrane

A

Normal cell function requires continuous regulated movement of water and solutes into and out of cells

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7
Q

What are two ways a transporter can move a solute against its concentration gradient

A
  • use of another ions concentration gradient
  • ATP
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8
Q

What establishes the concentration gradient

A

Resting membrane potential

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9
Q

What determines resting membrane potential

A

Ratio of K+ to Na+

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10
Q

Compare the conductance of potassium and sodium leak channels

A

Potassium is 100x leakier than sodium

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11
Q

What is the resting membrane potential of the average cell

A

-70mV

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12
Q

What is the EC sodium concentration

A

140mM

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13
Q

what is the EC potassium concentration

A

~4mM

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14
Q

What is the IC sodium concentration

A

~12mM

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15
Q

What is the IC potassium concentration

A

~140mM

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16
Q

Which side of the membrane is positive and negative

A

IC = -ve
EC= +ve

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17
Q

Chemical gradient

A

Difference in concentration across a membrane

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18
Q

Electrical gradient

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A

voltage across a membrane

19
Q

Electrochemical gradient

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A

The combined effect of the chemical and electrical forces acting to determine the direction of ion movement

20
Q

3 key properties of ion channels

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A
  • selectivity
  • conductance
  • gating
21
Q

Ion channel selectivity

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A

May allow only specific ions or ion types to transit

22
Q

Ion channel conductance

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A

How many ions can cross per unit time

23
Q

Ion channel gating

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A

External influences may act on a channel to cause a change in conductivity

24
Q

Examples of gating stimuli

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A

Mechanical, chemical, phosphorylation, or electrical

25
How are ion channels selective
- pore size - pore properties - sequence of amino acids inside
26
What do ion channels use to exclude substances
- size - electrical charge - chemical properties
27
Equation for conductance
Current over membrane voltage
28
What happens to ions in water
They associate with water molecules forming a shell
29
How is ion flux through a channel measured
Electrical current
30
What determines the magnitude of ion flux
The electrical and chemical driving forces for ion movement
31
What is the shape of the slope of conductance
Linear or non-linear
32
Phosphorylation gating
Activations of second messenger pathways (often by neurotransmitter interaction with GPCRs) can later result in ion channel opening via phosphorylation
33
Example of phosphorylation gating
mAChR - muscarinic AChR
34
Example of chemical gating
nAChR - nicotinic AChR
35
How do voltage gated sensors change configuration
Typically have a charged region that causes a change in shape of the channel when the voltage across it changes
36
What states can voltage gated sensors be in
Open Closed Inactive
37
How are voltage gated channels reactivated after entering the refractory phase
Hyperpolarisation of the membrane potential
38
What does mechanical gating do
Allow an increase in membrane permeability in response to physical force
39
What is mechanical gating important for
Touch, hearing, balance, other bodily functions (eg. Childbirth, BP)
40
Are carriers or channels faster
Channels
41
Types of secondary active transporters
Symporters Antiporters
42
Symporter
Move one substance down its concentration gradient and one substance against its concentration gradient. Both in the same direction
43
Antiporter
Move one substance down its concentration gradient and one substance against its concentration gradient. In opposite directions
44
transporters saturation
The maximum rate at which all carriers in a cell can work
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