Forces Across Membranes 2 Flashcards

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1
Q

Why does a difference of charge occur across the membrane?

A

The ions creating the concentration gradient are charged particles, causing an electric gradient

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2
Q

What is an electrochemical gradient?

A

Net effect of the chemical and electrical gradients

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3
Q

What defines the movement of ions across the membrane?

A

The electrochemical gradient

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4
Q

What does movement against the electrochemical gradient require?

A

Energy (active transport)

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5
Q

What is the resting membrane potential?

A

-70mV inside compared to outside

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6
Q

What are the 5 mechanisms of movement across the membrane?

A

Endocytosis and exocytosis

Diffusion

Mediated transport

Osmosis

Filtration

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7
Q

What is endocytosis/exocytosis?

A

Mechanism for moving macro molecules across the membrane without disrupting them

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8
Q

What are the steps of endocytosis?

A
  1. Invigination of the membrane to form a vesicle
  2. Disintegration on the cytoplasmic surface of the membrane
  3. Releasing the contents
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9
Q

What is the process of exocytosis?

A

The reverse process of endocytosis (leaving the cell)

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10
Q

What is diffusion?

A

Process where gas or a substance in solution expands to fill all available space

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11
Q

What does diffusion means in terms of the movement of molecules?

A

Molecules spread from regions of high concentration to regions of low concentration

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12
Q

During diffusion what direction to molecules move?

A

From high concentration to low, although some do randomly go from low to high - but the net movement is from high concentration to low concentration

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13
Q

What must the barrier be to allow diffusion to occur?

A

Permeable to the substance

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14
Q

What expression describes the size of diffusion?

A

F = kpA(C2-C1)

kp is the permeability coefficient

A is the surface area

F is the magnitude of diffusion

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15
Q

What are the two ways diffusion through the membrane can occur?

A

Through the phospholipid bilayer or protein channels

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16
Q

What must molecules be to pass through the phospholipid bilayer?

A

Small

Lipophillic

Uncharged

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17
Q

Do any lipophobic molecules pass through the lipid bilayer by diffusion?

A

Yes, small uncharged ones such as CO2 and urea

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18
Q

What are the two ways that ions cross the membrane?

A

Through protein channels or mediated transport proteins

19
Q

What are protein channels?

A

Transmembrane proteins that act as an aqueous route though the membrane

20
Q

Why can molecules like glucose not use protein channels?

A

The molecules are too large

21
Q

What forms of protein channels are there?

A

Open

Closed

22
Q

What are closed protein channels controlled by?

A

Gates

23
Q

What are the two types of closed protein channels?

A

Voltage gated protein channel

Ligand gated protein channel

24
Q

What are voltage gated protein channels?

A

Open/close in response to alternations of the membrane electrical potential

25
Q

What are ligand gated protein channels?

A

Open/close in response to a chemical such as a neurotransmitter or a hormone

26
Q

What do ligand gated protein channels act as?

A

A receptor and a transporter

27
Q

How do gated protein channels work?

A

Stimuli causes a conformational change of the protein which opens or closes the channel

28
Q

When is electrochemical equilbrium reached?

A

When the electrical and chemical gradients are in balance

29
Q

What is carrier mediated transport?

A

Proteins that are only open on one side of the membrane at any time that move molecules across

30
Q

What are the two forms of carrier mediated transport?

A

Facilitated diffusion

Active transport

31
Q

What is facilitated diffusion?

A

Movement of molecules through transport proteins down their electrochemical gradient

32
Q

What is active transport?

A

Movement of molecules through transport proteins against their electrochemical gradients using energy (ATP)

33
Q

How does carrier mediated transport switch the side of the membrane that it is open on?

A

A molecule binds to it and causes a conformational change which exposes the binding site on the other side

34
Q

What do carrier mediated transport proteins act as (other than a transporter)

A

An enzyme as it hydrolysis ATP to release energy

35
Q

What are active transporters otherwise known as?

A

Pumps

36
Q

What do active transporters maintain?

A

The concentration gradient

37
Q

What does each molecule of ATP allow to pass through a pump?

A

3 molecules of Na+ and 2 molecules of K+

38
Q

How much of the bodies resting energy is used to pumps?

A

40%

39
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42
Q
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43
Q
A