Exam 3 - Cell Membrane And Transport Flashcards

1
Q

Passive movement across cell membrane

A
  • Will move passively if lipid soluble

- If not…need to move via channel or carrier proteins (selective)

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2
Q

Simple Diffusion

A
  • Movement driven by a gradient

- carrier proteins can move in both directions

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3
Q

Facilitated

A
  • Driven by a gradient but helped by movement of another molecule
  • carrier proteins can move in both directions
  • used by glucose and amino acids
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4
Q

Active transport

A
  • Primary: energy provided directly by energy source
  • Secondary: energy stored in gradient that was created via use of energy source
  • Carrier proteins move in only one direction
  • Against gradient (usually electrochemical…Na, K, Ca, H, Cl)
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5
Q

Brownian motion

A
  • random motion in all directions

- affected by temperature (or KE)

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6
Q

Factors that affect rate of diffusion

A
  • Gradient (direct)
  • Surface Area (direct)
  • Solubility (direct)
  • Distance (indirect)
  • Sqrt of MW (indirect)
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7
Q

Gradients that affect rate of diffusion

A
  • [ ]
  • Electrical
  • Pressure (hydrostatic / osmosis)
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8
Q

Movement of water given osmolarity

A
  • Water will move toward area of higher osmolarity

- Osmolairty is measure of [solute]

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9
Q

Substances that passively diffuse

A
  • Oxygen
  • CO2
  • N2
  • Alcohol
  • For gases…solubility always the same unless disease is present
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10
Q

Osmosis

A
  • Movement of water through channel protein across membrane
    - not membrane itself
  • Very rapid
  • Aquaporins: water selective channel proteins (other ions can’t pass)
    - Ions move across via other channels if water soluble and small
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11
Q

Na channels

A
  • small diameter
  • strong negative charge inside channel (attracts Na+)
  • gradient across Membrane determines movement
  • gate is on outside
  • opens when inside of cell becomes less negative
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12
Q

Gated channels

A
  • can control permeability (really low to really high)
  • gates can be on outside or inside or both)
  • conformational change of protein causes opening or closing
  • Can be voltage or chemical (ligand) gated
    - voltage will open if voltage gradient changes…
    - ligand will open if bonded to ( ACH is common)
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13
Q

If we say potential of cell is negative….

A
  • The cell is more negative on the inside relative to outside
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14
Q

K gates

A
  • Gate is on inside

- opens when inside of cell becomes positive

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15
Q

Maximum facilitated diffusion rate

A
  • Depends on # of channels available
  • Depends on time it takes channel to complete cycle
  • V max
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16
Q

Na/K pump

A
  • ATP required
  • 3 Na out / 2 K in
  • Establishes negative voltage inside of cell
  • Made of two proteins (large and small…small function unknown)
  • maintains normal cell volume (w/o pump…cell would swell due to high [protein] on inside)
  • increase activity if increase in cell volume/osmolarity
  • creates a -4mV membrane potential
17
Q

Four gradients created with Na/K pumps

A
  • Increase in [Na] on outside
  • Increase in [K] on inside
  • More negative on inside
  • More osmotic particles on outside….so H2O moves out
18
Q

Na/K pump proteins

A
  • Large and Small
  • Large: 3 Na binding sites on inside
    2 K binding sites on outside
    ATP binding site on inside
  • Breakdown of ATP and release of energy causes change in shape
19
Q

Energy required for active transport

A

Energy = (1400)*( log([new or in]/[old or out]))

Units: calories/osmole

20
Q

Co-transport

A
  • using Na gradient to move amino acids/glucose down gradient into the cell
21
Q

Counter-transport

A
  • using Na gradient to move Ca/H in opposite direction out of cell
22
Q

Nernst equation

A

EMF (mV) = (-61.5/charge of ion)*(log([ion in]/[ion out]))

  • Tells us the potential charge that would be created if ions were to move across their gradients
23
Q

Starling forces acting on capillary

A
  • Capillary Hydrostatic P: pushes out of capillary
  • Interstitial Hydrostatic P: pushes into cap (+) or pulls out (-)
  • Plasma Oncotic P: Pulls into Cap
  • Interstitial Oncotic P: Pull out of Cap
24
Q

Edema

A
  • Build up of fluid in tissues if lymph system cannot remove fluid coming out of capillaries fast enough
25
Normal Osmolality of ECF/ICF
300 milliosmoles/Kg of H2O
26
Normal Osmolarity
285 - 300 mOsm/L - Long term: equilibrium will be reached - Short term: movement can happen between compartments
27
Calculate Osmolarity
- Determine g/L from % - Find number of moles using MW - Multiply by i factor if needed - note units (usually should end up in milliosmoles/L)
28
Pressure created by 1 osmole / L
19,300 mmHg or 19.3 mmHg (mOsm/L)
29
Common cell resting Membrane potential
- Most cells are negative
30
Stable voltage / potential
- No net current across the membrane | - Potential WILL NOT change unless there is a net movement of ions
31
Nernst Potential
- Like the equation but + or - depends on ion - + for NEGATIVE ions and - for POSITIVE ions - Put the sign in front of the 61.5
32
Number of ions needed to move to create a potential
- Very few number of ions | - Number of ions needed to start potential has no effect on overall gradient
33
Equation for multiple permeable ions
EMF = (P% of Na)(EMF of Na) + (P% of K)(EMF of K) + .....
34
Normal RMP for cardiac cells
- -90mV - Created by leaky K+ channels (move out of the cells) - Leaky channels polarize the membrane - Some effect caused by small amount of Na