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Physiology > Unit 3: The Plasma Membrane & Membrane Potential > Flashcards

Unit 3: The Plasma Membrane & Membrane Potential Flashcards

1
Q

True or False- All cells have both an internal and external plasma membrane.

A

False.

-All cells must only have an external membrane.

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2
Q

What type of molecules easily diffuse across the plasma membrane?

A

-small, non-polar, or uncharged molecules.

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3
Q

What are Trans-membrane proteins?

A

Exist within the plasma membrane and act as channels that allows for specific transport of molecules from the ECF to the ICF.

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4
Q

What is the purpose of Cholesterol within the membrane?

A

Contributes to the fluidity of the membrane.

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5
Q

Describe the fluid mosaic model

A

Proteins (icebergs) afloat in the sea of lipids.

Restricted by the cytoskeleton

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6
Q

What are Channel Proteins?

A

Highly selective canals that allow for the passage of certain molecules.
*Only ions pass through these channels.

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7
Q

What are Carrier Proteins?

A

-Allow for specific binging of molecules to proteins across the barrier that could not be done on their own.

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8
Q

What are Docking- Marker Acceptors?

A

-Located on the inner membrane surface, and bind to docking markers of secretory vesicles in a “Lock-in-key” fashion.

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9
Q

What are Membrane Bound Enzymes?

A

-Surface located proteins that control chemical reactions within the cell

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10
Q

What are Receptor Sites?

A

-Recognize and bind molecules on the plasma membrane.

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11
Q

What are Cell Adhesion Molecules (CAMS)?

A
  • Proteins that extend from the outer cell membrane that form loops that grip to connective tissues which interlace cells.
  • Can become signalling molecules.
  • ->Integrins, cadherins
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12
Q

What are Glycoproteins?

A

Important for cell’s to self-recognize.

*Carbohydrate containing markers which allow the cell to recognize it’s own cells as self.

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13
Q

What composes and holds together tissues?

A

-Cells, but also glue-like substances of fibrous proteins such as extracellular matrix! (biological glue)

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14
Q

What are the properties of collagen?

A

-Forms cable like fibres or sheets that give the cell tensile strength.

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15
Q

What are the properties of elastin?

A

-Protein within the ECM that is prominent in cells that stretch.

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16
Q

What are the properties of fibronectin?

A

-Promotes cell adhesion’s and keeps the cell in place.

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17
Q

What are desmosomes?

A

-Act like “spot rivets” that anchor 2 cells together so they are adjacent, but not touching. Glycofilaments attach these cells like string woven together.

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18
Q

What are tight junctions?

A

-Form fluid-tight seals between cells.
Join the lateral edges of epithelial cells so matter MUST pass through the cells and not around them.
–>Prevent undesirable leaks.

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19
Q

What are Gap junctions?

A

Link of 2 adjacent cells by connexon tunnels.

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20
Q

What are communication junctions?

A

Allow for the passage of ions and molecules without entering the cells extracellular fluid.

  • Abundant in cardiac/ smooth muscle.
  • NO passage of large molecules.
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21
Q

What are the two means of passive forces across the permeable plasma membrane?

A
  1. Diffusion down a concentration gradient.

2. Diffusion down an electrical gradient.

22
Q

PASSIVE Diffusion moves from?

A

High concentration to low concentration.

23
Q

What is Net Diffusion?

A
  • The total number of molecules that move in both directions of the concentration gradient.
    ex. -3 left, +7 right = 4
24
Q

Fick’s Law of Diffusion?

A

Magnitude of gradient, permeability of membrane, surface area over where diffusion occurs, molecular weight of the substance and distance of diffusion.

25
Q

Where do ions move in an electrical gradient?

A

-To the sides of opposite charge.

26
Q

What is an Electrochemical gradient?

A

-Occurs with both an electrical and chemical gradient occur at once.

27
Q

What are aquaporins?

A

Channels that allow for the passage of water through the plasma membrane.

28
Q

Define Osmosis.

A

-Water moves from areas of low concentration to high concentration.

29
Q

What is hydrostatic pressure?

A

-Pressure exerted by a large volume of water compared to a smaller volume of water. This difference in pressure moves water to the smaller volume side.

30
Q

What is osmotic pressure?

A

-A measure of the tendency for water to move into a cell, based on the concentration gradient and non-penetrating solutes.

31
Q

Osmotic pressure vs. hydrostatic pressure relationship.

A

-Greater concentration of solute= less volume of water= greater drive of water into the cell= higher drive of pressure to stop osmotic flow

32
Q

What is Tonicity?

A
  • The effect the solution has on cell volume (shrinks, swells or stays the same
  • Determined by solute concentration.
33
Q

What is an isotonic solution?

A

Solution has no impact on cell volume.

34
Q

What is a hypotonic solution?

A

Low concentration of solutes in solution= high volume of water in solution compared to cell, leads to cell swelling due to high volumes of water entering the cell.

35
Q

What is a hypertonic solution?

A

High concentration of solutes in solution= low volume of water in solution= cell shrinking (water moving out to environment)

36
Q

Explain carrier mediated transport?

A
  • Carrier proteins REVERSE the shape of the plasma membrane after binding of specific molecules to allow molecules to transfer from the ECF to the ICF.
  • Change in plasma membrane conformation.
37
Q

What is carrier mediated transport regulated by?

A
  1. Specificity of binding
  2. Saturation- A limited # of binding sites
  3. Competition for binding
38
Q

What is the Transport Maximum ? (Tm)

A
  • The maximum number of molecules that can bind carriers at once.
  • Until Tm is reached, more substrate can be carried over.
39
Q

What is Facilitated Diffusion?

A

-carrier mediated transport that occurs passively, from areas of high to low concentration.

40
Q

What is Active Transport?

A
  • carrier mediated transport that occurs “uphill”; areas of low to high concentration.
  • After phosphorylation on the low concentration side, the membrane is flipped so that the molecule is on the high concentration side. REQUIRES ATP
41
Q

How does the hydrogen ion pump work in the body?

A

-In specialized stomach muscles to transport H+ into the stomach lumen with the release of HCl.

42
Q

How does the Na/ K Pump work?

A

2 K+ moves from the outside to the inside, and 3 NA+ moves from the inside to the outside. This makes the outside of the membrane more positive and the inside more negative, making the inside negative.

43
Q

What is Vesicular Transport?

A

Transport of large particles into the cells ICF without touching the cells ECF as it passes through the tunnel.

44
Q

Exocytosis Mechanism

A

-Membrane enclosed vesicles bind to the cell surface and open contents up to the cell exterior.

45
Q

Endocytosis Mechanism

A

-Membrane enclosed vesicles bind to the cell surface, creating a pinch. This encloses material into the cell.
Materials may be further treated:
1. Degraded by lysosomes in the ICF.
2. Released to the exterior by ECF.

46
Q

What is membrane potential?

A
  • Separation of charges across the membrane or to a difference in the relative number of cations and anions in the ICF and ECF.
  • Potential is measured in volts (mV’s)
47
Q

Resting Membrane Potential?

A
  • When excitable tissues are at rest.
  • 70mV is the resting membrane potential, meaning there is more sodium outside the cell than potassium inside, making it negative inside.
  • It’s normal to have more sodium outside and more potassium inside the cell.
48
Q

K+ Equilibrium potential (Ek+) ?

A

Potassium will exit the cell and enter the ECF until it reaches a membrane potential of -90 mV.

  • Potential is usually closer to EK+ due to the membranes greater permeability to potassium.
  • ->Potassium leaves cell until it reaches -90mV (equilibrium potential- meaning it won’t allow any more potassium to leave at this level)
  • Only ever approaches membrane potential
49
Q

Na + Equilibrium potential (ENa+) ?

A

Sodium channels open and sodium ions move into the cell, until the membrane potential reaches +60mV.

*Won’t reach chemical equilibrium–> at +60mV the cell is positive enough to repel anymore entry of sodium ions from entering.

50
Q

How does the Na+/K+ pump counteract leaks?

A

All passive leaks are counteracted by active pumping.

-If sodium continuously leaks into the cell, potassium will counteract it by moving out of the cell.

Physiology (12 decks)

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