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BIOLOGY 225 > Cell Physiology (Exam 1) > Flashcards

Cell Physiology (Exam 1) Flashcards

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1
Q

Function of plasma membrane

A
  • Helps maintain composition of intra- and extracellular fluids
    • Regulates traffic in and out of the cell
  • Forms a framework for protein components of the cell
    • Proteins embedded in the membrane
  • Detects chemical messengers at cell surface than can be transported through the membrane
  • Links adjacent cells together
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2
Q

Tight junctions

A
  • Impermeable barrier
  • Occurs on apical (silica) side
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3
Q

Anchoring Junctions

A
  • Desmosomes
    • Composed of proteins with cell adhesion molecules
  • Adherens junction
    • Forms rings around cells
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4
Q

Gap junctions

A
  • Composed of proteins that form channels between cell 1 and cell 2
    • Connects their cytoplasm
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5
Q

Glycoproteins

A
  • Membrane protein
  • Have sugar chains attached
  • Can be peripheral or integral
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6
Q

Integral proteins

A
  • Membrane protein
  • Tightly bound to the membrane
  • Either embedded in or span the entire bilayer
  • Involved in structural support, signaling, and transport
    • Channel proteins do the transport and are integral proteins
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6
Q

Peripheral proteins

A

○ Membrane protein
○ Interact with the membrane surface or with integral proteins
○ Not embedding into the membrane

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7
Q

Relationship between membrane permeability and hydrophobic molecules

A

Pass through the membrane easily

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8
Q

Relationship between membrane permeability and small, uncharged, polar molecules

A

○ Glycerol, water, etc.
* Move slightly through the membrane by simple diffusion

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9
Q

Relationship between membrane permeability and large, uncharged, polar molecules

A

○ Not permeable
* Glucose, sucrose

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10
Q

Relationship between membrane permeability and ions

A

Impermeable

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11
Q

Relationship between membrane permeability and charged polar molecules

A
  • Impermeable
  • Amino acids, ATP
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12
Q

Simple Diffusion

A

Passive form of diffusion in which molecules move due to the intrinsic kinetic energy of their chemical gradients, flowing from an area of high concentration to one of low concentration (no ATP). This diffusion never stops, however the net becomes 0

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13
Q

Flux

A

The difference between two one-way fluxes

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14
Q

Net Flux depends on:

A

® Permeability
® Concentration gradient
® Temperature
® Surface area
® Size of molecule
* Distance

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15
Q

Facilitated Diffusion

A

Movements on molecules through trans-membrane proteins, molecules move down their electrochemical gradient, no ATP required (passive)

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16
Q

Channel Proteins

A

A tunnel through the membrane

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17
Q

Types of Channel Proteins

A

Ion channels, constitutive channels, and gated channels

18
Q

Ion Channels

A
  • Selective or non-selective
    • Selective:
      ® Na+, K+, Cl_
    • Non-selective
      ® Monovalent channels
      * Allows Na+. K+, and Li+
19
Q

Constitutive channels

A

Always open, includes aquaporins

20
Q

Gated Channels

A

Only open under certain conditions (in response to stimulus)

21
Q

Osmosis

A
  • Passive transport of water
    • The net diffusion of water from a region of high water concentration to a region of low water concentration
  • Facilitated by aquaporins
22
Q

How is water movement determined

A

Direction of water movement is determined only by a difference in total solute concentration and not by types of solute

23
Q

Osmolarity

A

○ Total concentration of solute in solution in mols/L (OsM)
* Depends on the total number of molecules, not the individual type

23
Q

Isoosmotic

A

Same osmolarity

24
Q

Hyperosmotic

A

Higher OsM

25
Q

Hypoosmotic

A

Lower OsM

26
Q

Hydrostatic Pressure

A

○ Water above you pushed down (pressure) on you
* The pressure exerted by the standing column of water due to gravity

27
Q

Osmotic Pressure

A

○ Pressure generated by water moving based on osmolarity

28
Q

Ligand-Gated Channel

A

○ A signal molecule (ligand) binds to the receptor/channel regulating the opening and closing of the gates
○ Acetylcholine regulates entry of Na+ into muscle cells (selective channel)
* Less common, but some channels close with the binding of the ligand

29
Q

Voltage-Gated Channels

A

○ Regulated by electrical state of the cell
* Voltage gated Na+ channels are activated by the membrane (when membrane potential is met)

30
Q

Mechanically-gated channels

A

○ Regulated by a physical change
* Pressure is an example of such a change

31
Q

Function of Permeases

A
  • Carrier/permeases/transporters bind the substrate that they are moving across the membrane
    • It goes through a conformational change, which then allows the molecule to be released inside
    • ATP not needed
    • Never open on both side
  • Transport down the concentration gradient by carrier proteins instead of ATP
32
Q

Active Transport

A
  • Transported molecules must bind to a transporter
    • Metabolic energy is required
      • Directly in primary active transport
        - Indirectly in secondary active transport
33
Q

Primary Active Transport

A
  • Requires ATP
    • Moves solutes against their gradients
    • Specific membrane bound transport proteins involved
      • Are ATP-ases
        • Breaks down ATP into its parts, allowing movement of molecules across the membrane
  • Maintains electrochemical gradients
    • Not equilibrium
34
Q

Ca2+ Pump

A
  • Hydrolysis of ATP directly required for the function of the carriers
    • Molecule or ion binds to recognition site on one side of the carrier protein
    • Binding stimulates phosphorylation (breakdown of ATP) of carrier
    • Carrier protein undergoes conformational change
    • Hinge-like motion releases transported molecules to opposite side of membrane
      Primary active transport
35
Q

Na+/K+ Pump

A
  • Primary active transport
    • ATPase pulls both Na+ and K+ against their gradients
    • Na+ initially has sa high concentration outside of cell and low inside, K+ is the opposite
      1. Na+ binds to the protein, stimulating phosphorylation of ATP
      2. Phosphorylation of ATP causes the protein to change conformation
      3. The conformational change expels Na+ and takes in K+
      4. K+ binding gives you another phosphorylation of ATP
      5. That changes the conformation again
      6. K+ is released into the cell and the cycle repeats
    • ATP –> ADP and P
    • Actively extrudes 3Na+ and transports 2k+ inward against the concentration gradient
      • Changes osmolarity, and therefore flow of water
    • Involved in setting up the gradients that allows electrochemical impulses to occur
  • Provides energy for couples transport of other molecules
36
Q

Secondary Active Transport

A
  • No direct input of energy required, but it depends on the electrochemical gradient that is established by the primary active transport
    • Coupled transport
      • The energy required for uphill movement is obtained by the downhill transport of Na+
  • Hydrolysis of ATP by Na+/K+ pump required indirectly to maintain Na+ gradient
37
Q

Classifications of Transporters

A

Uniporter, symporter/cotransporter, antiporter/exchanges

38
Q

Uniporter

A

The specific transport of a single substance in or out of cells

39
Q

Symporter/cotransporter

A

carries two or more molecules across the cell membrane in the same direction

40
Q

Antiporter/exchanges

A

Moves multiple cells in opposite directions across the cell membrane

41
Q

Exocytosis

A

Fusion of the membrane-bound vesicles that contains cellular products with the plasma membrane

42
Q

Endocytosis

A

Specific molecules can be taken into the cell because of the interaction of the molecule protein receptor

BIOLOGY 225 (10 decks)

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