EX1; Excitable Cells; Ions/Transport

Question 1

What three types of cells are considered excitable cells

Answer 1

neurons
sensory cells
most muscle cells

Question 2

What categorizes an excitable cell

Answer 2

their physiologic functions rely critically on electrical events in their plasma membrane

Question 3

What three things categorize a mechanism of cell-to-cell (intercellular) communication

Answer 3

very rapid
allow precise timing of signals between cells
allow complex patterns of communication between cells

Question 4

This is a mechanism for sensing environmental changes (light, sound, temp, etc.)

Answer 4

stimuli from environment; electrical events in receptor cells

Question 5

This is a mechanism for triggering intracellular events

Answer 5

electrical events in cells; intracellular changes that are either rapid or can accumulate over time

Question 6

This is the activation to initiate an event

Answer 6

excitation

Question 7

What are the three major components of excitation

Answer 7

extracellular fluid
intracellular fluid
membrane

Question 8

What is the composition of extracellular fluid

Answer 8

primarily ions, proteins, and other molecules

high NaCl concentration

Question 9

What is the composition of intracellular fluid

Answer 9

ions, much higher concentrations of proteins, other molecules
high KCl concentration

Question 10

This allows cells to communicate with one another

Answer 10

the differences between the inside (KCl) and outside (NaCl) of cells

Question 11

What is the composition of the membrane

Answer 11

phospholipid bilayer and proteins (equal amount), small (~5%) carbohydrates

Question 12

This characteristic of cell membranes is essential to excitation

Answer 12

permeability

Question 13

What is the permeability of a membrane to an ion an index of

Answer 13

the ability of the ion to cross the membrane; if the ions can readily cross the membrane, then the membrane has a high ion permeability

Question 14

Changes in the permeability that are these two things are essential to excitation in cells

Answer 14

ion-specific

exquisitely timed

Question 15

This is random diffusion down an electrical or concentration gradient; organic molecules or ions

Answer 15

simple diffusion

Question 16

These type of molecules diffuse rapidly through the membrane which is 50% lipid; solubility in lipid is high

Answer 16

non-polar organic molecules; O2, CO2, fatty acids, steroids

Question 17

Does the diffusion of non-polar organic molecules require energy?

Answer 17

No; no energy is required

Question 18

These type of molecules cross membranes via channels which are proteins, often several subunits and generally specific for that molecule

Answer 18

ions

Question 19

This is the amount of a substance crossing a surface per unit of time

Answer 19

flux

Question 20

Diffusion between two compartments is always what

Answer 20

bi-directional; 1 to 2 and 2 to 1

Question 21

This is the difference between the two unidirectional fluxes

Answer 21

net-flux

Question 22

When net-flux is zero, the system is referred to be in a state of what

Answer 22

diffusion equilibrium

Question 23

What are the two types of mediated transport

Answer 23

facilitated diffusion

active transport

Question 24

This type of mediated transport has no energy requirement; a membrane protein serves as a carrier to translocate a molecule across a membrane

Answer 24

facilitated diffusion

Question 25

This type of mediated transport requires energy; a molecule is bound to a transporter (pump) and it moves up the concentration and/or electrical gradient

Answer 25

active transport

Question 26

What two things does energy effect involving active transport

Answer 26

the affinity of the transporter for the ligand on one side of the membrane more than the other rate of transporter conformational change

Question 27

What is the energy source of the primary active-transport model

Answer 27

hydrolysis of ATP

Question 28

What is the primary-active transport model

Answer 28

hydrolysis of ATP transporter becomes phosphorylated changes affinity for solute (ligand) increases transport rate

Question 29

What is the secondary-active transport model

Answer 29

uses energy in ion concentration gradient across membrane | transporter has 2 binding sites

Question 30

What three factors determine the rate of flux

Answer 30

number of transporters in the membrane extent of transporter saturation rate of transporter conformational change

Question 31

What are three types of channels

Answer 31

``` ligand-sensitive (chemically regulated) voltage sensitive (voltage regulated) mechanosensitive ```

Question 32

What are the three basic steps in mediated transport

Answer 32

ligand binds to transporter transporter undergoes conformational change ligand is released on other side of membrane

Question 33

This is the bulk flow of water across a membrane; shrinking or swelling

Answer 33

osmosis

Question 34

Water is polar and therefore diffused down its concentration gradient through these channels

Answer 34

aquaporins

Question 35

This is the total solute concentration in a solutaion

Answer 35

osmolarity | 1. 0 osmol = 1.0 mol solute 1. 0 mol NaCl = 2.0 osmols

Question 36

What is the osmolarity of extracellular fluid

Answer 36

300 mOsm

Question 37

300 mOsm of non-penetrating solutes; no change in cell volume is what type of solution

Answer 37

isotonic

Question 38

< 300mOsm of non-penetrating solutes; cell swells, is what type of solution

Answer 38

hypotonic

Question 39

> 300 mOsm of non-penetrating solutes; cell shrinks, is what type of solution

Answer 39

hypertonic

Question 40

300 mOsm of non penetrating solutes plus penetrating solutes is what type of solution

Answer 40

isoosmotic

Question 41

< 300 mOsm of non penetrating solutes plus penetrating solutes is what type of solution

Answer 41

hypoosmotic

Question 42

> 300 mOsm of non penetrating solutes plus penetrating solutes is what type of solution

Answer 42

hyperosmotic

Question 43

True or False | A solution can be hyper osmotic and isotonic at the same time

Answer 43

True

Question 44

This is engulfment of fluid and particles from the extracellular space

Answer 44

endocytosis

Question 45

This is engulfment of small particles with or without small volume of ECF; performed by all cell types

Answer 45

pinocytosis

Question 46

This is engulfment of large particles or cellular debris; performed by specialized cells

Answer 46

phagocytosis

Question 47

This is the export of material from a cell

Answer 47

exocytosis

Question 48

What is the purpose of exocytosis

Answer 48

replaces membrane patches internalized through endocytosis

Question 49

What is the mechanism of release of molecules synthesized within cells

Answer 49

secretion