Cell Physiology (Exam 1)

Question 1

Function of plasma membrane

Answer 1

• 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

Question 2

Tight junctions

Answer 2

• Impermeable barrier
• Occurs on apical (silica) side

Question 3

Anchoring Junctions

Answer 3

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

Question 4

Gap junctions

Answer 4

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

Question 5

Glycoproteins

Answer 5

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

Question 6

Integral proteins

Answer 6

• 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

Question 6

Peripheral proteins

Answer 6

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

Question 7

Relationship between membrane permeability and hydrophobic molecules

Answer 7

Pass through the membrane easily

Question 8

Relationship between membrane permeability and small, uncharged, polar molecules

Answer 8

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

Question 9

Relationship between membrane permeability and large, uncharged, polar molecules

Answer 9

○ Not permeable
* Glucose, sucrose

Question 10

Relationship between membrane permeability and ions

Answer 10

Impermeable

Question 11

Relationship between membrane permeability and charged polar molecules

Answer 11

• Impermeable
• Amino acids, ATP

Question 12

Simple Diffusion

Answer 12

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

Question 13

Flux

Answer 13

The difference between two one-way fluxes

Question 14

Net Flux depends on:

Answer 14

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

Question 15

Facilitated Diffusion

Answer 15

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

Question 16

Channel Proteins

Answer 16

A tunnel through the membrane

Question 17

Types of Channel Proteins

Answer 17

Ion channels, constitutive channels, and gated channels

Question 18

Ion Channels

Answer 18

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

Question 19

Constitutive channels

Answer 19

Always open, includes aquaporins

Question 20

Gated Channels

Answer 20

Only open under certain conditions (in response to stimulus)

Question 21

Osmosis

Answer 21

• 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

Question 22

How is water movement determined

Answer 22

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

Question 23

Osmolarity

Answer 23

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

Question 23

Isoosmotic

Answer 23

Same osmolarity

Question 24

Hyperosmotic

Answer 24

Higher OsM

Question 25

Hypoosmotic

Answer 25

Lower OsM

Question 26

Hydrostatic Pressure

Answer 26

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

Question 27

Osmotic Pressure

Answer 27

○ Pressure generated by water moving based on osmolarity

Question 28

Ligand-Gated Channel

Answer 28

○ 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

Question 29

Voltage-Gated Channels

Answer 29

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

Question 30

Mechanically-gated channels

Answer 30

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

Question 31

Function of Permeases

Answer 31

* 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

Question 32

Active Transport

Answer 32

* Transported molecules must bind to a transporter * Metabolic energy is required * Directly in primary active transport - Indirectly in secondary active transport

Question 33

Primary Active Transport

Answer 33

* 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

Question 34

Ca2+ Pump

Answer 34

* 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

Question 35

Na+/K+ Pump

Answer 35

* 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

Question 36

Secondary Active Transport

Answer 36

* 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

Question 37

Classifications of Transporters

Answer 37

Uniporter, symporter/cotransporter, antiporter/exchanges

Question 38

Uniporter

Answer 38

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

Question 39

Symporter/cotransporter

Answer 39

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

Question 40

Antiporter/exchanges

Answer 40

Moves multiple cells in opposite directions across the cell membrane

Question 41

Exocytosis

Answer 41

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

Question 42

Endocytosis

Answer 42

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