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Physiology 210A > Cell Physiology Lecture 2 > Flashcards

Cell Physiology Lecture 2 Flashcards

1
Q

Vesicular Transport

A

A type of transport that uses vesicles to move substances across biological membranes

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2
Q

Endocytosis

A

The uptake of material into the cell using vesicles containing material that pinch off from the plasma membrane, and enter the cytoplasm of the cell.

-basically cell membrane wraps around and then pinches

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3
Q

What are the 3 types of endocytosis?

A
  1. Phagocytosis
  2. Pinocytosis
  3. Receptor-mediated endocytosis
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4
Q

Exocytosis

A

release of material from the cell using vesicles containing material
that fuse with the plasma membrane and release their contents into the
extracellular fluid

-basically the vesicle fuses with the membrane and releases contents out to the ECF

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5
Q

Phagocytosis is also called _______

A

cell eating

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6
Q

How does phagocytosis bring things in the cell?

A

It uses extensions of the plasma membrane called pseudopodia to surround material being brought up into the cell.

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7
Q

Phagocytosis is used for bringing __________

A

large particles into the cell, such as bacteria or cell debris from nearby cells

(process used by white blood cells)

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8
Q

Pinocytosis is also called _______

A

Cell drinking

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9
Q

How does pinocytosis bring things in the cell?

A

-Plasma membrane simply ‘indents’ below the particles to be brought into the cell (does not use pseudopodia)

-Plasma membrane pinches together once it has indented and the vesicle containing particles brought into the cell is called an endocytic vesicle

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10
Q

Pinocytosis is as __________

A

Nonspecific process

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11
Q

Nonspecific process meaning in pinocytosis

A

Means it simply brings in extracellular fluid and substances dissolved in that fluid

-reason for why it is called “drinking”

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12
Q

Pinocytosis is used for ingesting ________

A

small molecules, ions, and nutrients (can not bring in large things into the cell such as bacteria or cell debris)

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13
Q

Steps of phagocytosis:

A

Once activated, the phagocytic cell moves to the material it will ingest

Steps of Phagocytosis:

  1. (Recognition) of substance to be ingested
  2. (Attachment) of phagocyte to the substance to be ingested
  3. (Pseuopodia) reach around the substance and come together to form a phagosome inside the phagocytic cell
  4. (Fusion) of the phagosome to a lysosome to form phagolysosome
  5. (Destruction) of ingested substance by lysosomal enzymes
  6. (Release) of end products into the cell or out of the cell by exocytosis
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14
Q

Receptor-mediated endocytosis is a ___________

A

Specific process as it involves receptors which bind specific ligands to be brought into the cell

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15
Q

What is the name of the cytoplasmic protein involved in receptor-mediated endocytosis?

A

Clathrin

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16
Q

Receptor-mediated endocytosis steps:

A
  1. The ligand binds to the receptor which causes it to change its shape. This causes clathrin to move to the membrane.

2.many receptors with ligands attached gather together in one small area on the cell’s surface, where clathrin is also present. By doing this, the cell can bring in more of the ligand at once, making the process more efficient

3.the part of the cell membrane where the clathrin and receptor-ligand complexes are gathered starts to bend inward, forming a small dip or pocket. This pocket, covered in clathrin and holding the receptors with their ligands, is called a clathrin-coated pit.

4.the indented part of the membrane, which contains the receptor-ligand complexes and is covered in clathrin, pinches off from the rest of the cell membrane to form a small bubble or vesicle. This vesicle is still lined with clathrin and carries the receptor-ligand complexes inside the cell.

5.
Once the vesicle is formed and inside the cell, the clathrin (the outer coating) is removed from the vesicle.

6.After the vesicle is inside the cell and the clathrin is removed, it has several options for what to do next: deposit contents into the lumen, travel across the cell and fuse with plasma membrane to releae conent, fuse with orghanellesd called endosomes, which then sort contents to the golgi or lysosomes.

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17
Q

Exocytosis Function

A

-Secrete specific substances like hormones

-release waste products

-add components of the membrane like lipdes and proteins to the plasma membrane when vesicles fuse with the membrane (balances portion removed by endocytosis).

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18
Q

Are there process that do not utilize vesicles to move substances across the membrane?

A

Yes

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19
Q

A difference in energy across a membrane acts as a __________

A

driving force to move a substance

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20
Q

Substances always move from a region of high energy to a region of ________

A

low energy

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21
Q

What are the 3 types of driving forces for non-vesicular transport?

A
  1. Chemical
  2. Electrical
  3. Electrochemical
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22
Q

When is there a chemical driving force?

A

When there is a difference in concentration between a substance on either side of a membrane.

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23
Q

How do molecules move in a chemical driving force?

A

They move passively from high to low concentration or “down” the concentration gradient.

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24
Q

What happens as the gradient gets more extreme in chemical driving force?

A

The rate of transport of the substance increases

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25
Q

What substances can be affected by the electrical driving force?

A

Any substance that is charged

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26
Q

Cells in our body have a membrane ________

A

potential

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27
Q

The electrical driving force exists due to the ___________

A

membrane potential

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28
Q

Membrane Potential meaning

A

the difference in electrical potential or voltage across a cell membrane

-also called a ‘seperation’ of charge across the membrane

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29
Q

Any charged substance experiences ____________ due to the membrane potential.

A

Attractive or Repulsive forces

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30
Q

Electrochemical Driving Force

A

The sum of the electrical and chemical driving forces acting on an ion.

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31
Q

Are neutral (not charged) substances affected by electrical driving force?

A

No

32
Q

The direction of the electrochemical driving force depends on _________

A

the net direction of the electrical and chemical driving forces.

33
Q

Simple Diffusion

A

The passive movement of a molecule through a biological membrane’s lipid bilayer

34
Q

Simple diffusion does not require the __________

A

input of energy

35
Q

Two factors affecting. the solubility of the substance in lipid

A
  1. Polarity
  2. Size
36
Q

The plasma membrane has a __________ core

A

non-polar

37
Q

Polar solubility

A

Soluble in water,
insoluble in lipids

38
Q

Nonpolar solubility

A

water in-insoluble
soluble in lipids

39
Q

Substances that move by simple diffusion move from _________

A

a region where they are found in high concentration to a region where they are found in a low concentration, or “down” their concentration gradient.

40
Q

Which substances move across a phospholipid bilayer by simple diffusion?

A
  1. If a substance is small, non-polar and uncharged
  2. If a substance is polar and uncharged, it may cross by SD if small enough
41
Q

When will you not be able to move across a phospholipid bilayer by simple diffusion?

A

-Any substance that has a charge, regardless of size, polarity because their charge will not allow them to interact with the non-polar tails of the phospholipids.

-If a substance is large, uncharged, and polar

42
Q

3 other factors affecting the rate of simple diffusion:

A
  1. Magnitude of the driving force
  2. Membrane surface area
  3. Membrane Permeability
43
Q

Factor affecting rate of simple diffusion - Magnitude of the driving force

A

The greater the concentration difference of a substance on either side of the membrane, the greater the driving force, and the greater the rate of SD

44
Q

Factor affecting rate of simple diffusion - Membrane Surface Area

A

The amount of membrane available for cells to cross matters. A larger cell has a bigger surface area for membranes and thus more molecules can cross at once.

45
Q

Factor affecting rate of simple diffusion - Membrane Permeability

A

The permeability of the membrane to a specific substance depends on the membrane, and the substance.

Depends on:

  1. The lipid solubility of the diffusing substance (non-polar substances cross more easily)
  2. Size and shape of the diffusing substance (small and more regularly shaped cross the membrane more easily)
  3. Temperature of the substance, at high temperature substances move around more helping them diffuse faster across the membrane
  4. Diffusing Distance, if a substance has to cross more layers of cells it will diffuse slower than if it had to only cross one layer (referring to the membrane cells)
46
Q

What is osmosis

A

The net movement of water across a selectively permeable membrane driven by a difference in solute concentration on both sides of the membrane.

47
Q

In osmosis water flows from:

A

A region of high water concentration to low water concentration

or

a region of low solute concentration to a region of high solute concentration

48
Q

How do you change the concentration of water?

A

By adding solute

49
Q

Pure water

A

water with no solute added

50
Q

Water can move across membrane through _________

A

simple diffusion

51
Q

Why can water flow across membranes through simple diffusion?

A

Because water molecules are polar but small, the simple diffusion of water is limited but finite.

52
Q

Certain tissues have a larger permeability to water such as the _________ because ________-

A
  1. Kidneys
  2. there are water channels called aquaporins
53
Q

Mediated transport is ________

A

The use of a protein to cross a cell

54
Q

What are the two forms of mediated transport?

A

-Facilitated Diffusion

-Active Transport

55
Q

Facilitated Diffusion is a type of _______

A

passive transport

56
Q

Passive Transport

A

Energy is not required, as substances move passively down their concentration gradient

57
Q

In facilitated diffusion, types of proteins are involved as _______

A

carriers or channels

58
Q

Facilitated Diffusion is a ___________ transport process

A

specific

59
Q

Facilitated Diffusion selectivity

A

-Carriers are proteins with specific binding sites for the substance to be transported across the membrane

-Channels are selective for a specific ion (ie: sodium ion) or a type of ion (ie: cation or anion)

60
Q

Channel-mediated facilitated diffusion:

A

-Channels may be selective for a specific ion or type of ion that moves through them

-Channels do not just allow ions to pass through. For example, aquaporins are water channels that are specific for water molecules

-The direction and magnitude of ion flux through a channel depends on the
electrochemical gradient of that ion

-Channels exist in an open or closed state and may be gated. Gating refers to the opening
(activation) or closing (by deactivation or inactivation) of ion channels. Gating is the process of an ion channel transforming between any of its conducting and non- conducting states.

60
Q

Carrier-mediated facilitated diffusion:

A

-Uses proteins called carriers which have a specific binding site

-Carrier proteins bind the substance and move it across the plasma membrane from a region of high concentration to a region of low concentration (diffusion)

-Does not require energy such as ATP

61
Q

Example of Carrier-mediated facilitated diffusion

A

The GLUT family of proteins, which are carriers move glucose across the membrane from a region of high concentration to a region of low concentration (glucose is non-polar and uncharged but it is too big to move across the membrane by simple diffusion).

62
Q

Channel gates may be:

A

voltage-gated (changes in voltage cause the channel to open or close)

ligand-gating (the binding of a substance or ligand to a binding site on the channel causes it to open or close)

mechanically-gated (mechanical stimuli such as swelling or stretching of a cell causes the channel to open or close)

63
Q

Active transport proteins are often called:

A

pumps

64
Q

Active transport:

A

-Involves transport proteins with specific binding sites for the substance to be transported

-Capable of uphill transport, or moving a substance against an gradient from low to high

-utilize energy to do uphill transport

65
Q

Primary or secondary active transport obtain energy from __________

A

Different sources

66
Q

Example of Primary Active Transport

A

Na+/K+ Pump

67
Q

Na/K pump at rest

A

At rest, a cell has a high Na+, outside the cell, and a high K+ inside the cell

68
Q

What does the Na/K pump do for every molecule of ATP hydrolyzed?

A

It moves 3 Na+ ions out of the cell, and 2 K+ into the cell, against their concentration gradients

69
Q

Function of Na+/K+ pump

A

contributes to establishing and maintaining the membrane potential of the cell and maintains the Na+ and K+ concentration gradients

70
Q

Secondary Active Transport

A

Uses electrochemical gradient established by primary active transport to move ions

71
Q

Secondary Active Transport Example

A

Na+/glucose transporter, moves glucose same direction (against its gradient)

Na+/H+ exchanges, moves Hydrogen in opposite direction of Sodium (both against their gradient)

72
Q

Simple Diffusion is a _______________

A

unsaturable transport process

73
Q

Mediated Transport is a _____________

A

saturable transport process

74
Q

Why is Simple Diffusion an unsaturable transport process?

A

Because it does not involve proteins and binding sites. As you increase the concentration of the substance you increase the movement of the substance across the membrane

75
Q

Why is mediated transport a saturable transport process?

A

Because it involves proteins and binding sites, each cell has a limited amount of proteins and each protein has a limited number of binding sites for a substance.

As the concentration of substance increases, an increased number of binding sites are occupied. The transport rate will plateau once all site are occupied, and increasing the concentration would not do anything.

Physiology 210A (10 decks)

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