Excitable cells Part 1 (6/16/15)

Question 1

Electrical events provides a mechanism for what 2 things?

Answer 1

A mechanism for sensing environmental changes

A mechanism for triggering intracellular events (activation of muscle)

Question 2

What are the 3 components of Cell Excitation?

Answer 2

• Extracellular fluid (High NaCl content)
• Membrane (Phospholipid bilayer and with proteins)
• Intracellular fluid (Predominant salt is KCl)

Question 3

_____ is random diffusion down an electrical or concentration gradient (Organic molecules or ions).

Answer 3

Simple diffusion

Question 4

______ diffuse rapidly through the membrane (No energy required)

Answer 4

Non-polar, organic molecules

Question 5

________ cross membrane through channels which are proteins.

Answer 5

Ions (K-channels & Na-channels)

Question 6

What are some examples of Nonpolar substances?

Answer 6

O2, Co2 = crosses membrane easily for breathing
Fatty acids = Heart needs these
Steroid hormones = synthesized as needed and can quickly enter cells to meat metabolic demands

Question 7

_____ is the amount of a substance crossing a surface per unit of time.

Answer 7

Flux *Flux is bidirectional

Question 8

____ is the difference between the two directional fluxes.

Answer 8

Net flux

Question 9

When net flux = 0 the system is referred to as being _______.

Answer 9

In a state of diffusion equilibrium (Does not mean flux has stopped, just means it is balanced)

Question 10

What are the 2 types of Mediated Transport?

Answer 10

1. Facilitated diffusion = No ATP needed, uses membrane protein to serve as a carrier. (Transports glucose and other large polar molecules.)
2. Active Transport = ATP required, Molecule or ion is bound to transporter and moves UP concentration/electrical gradient.

Question 11

What can Energy input in active transport affect?

Answer 11

Affinity of transport for the ligand on one side of the membrane more than the other.

Rate of transporter conformational change.

Question 12

Describe the process of PRIMARY active transport…

Answer 12

Energy source is hydrolysis of ATP –> Transporter becomes phosphorylated –> changes affinity for solute (ligand) –> increases transport rate.

Question 13

Active Transport of Na is almost always ______ the cell.

Answer 13

out of the cell. Because the concentration gradient for Na is going into the cell.

Question 14

Describe the process of SECONDARY active transport…

Answer 14

uses energy in ION CONCENTRATION GRADIENT (no ATP needed) *Transporter has two binding sites and s the primary transporter of amino acids.

Question 15

What are the 3 basic steps of mediated transport?

Answer 15

Ligand binds to transporter, Transporter undergoes conformational change, ligand is released on the other side of membrane.

Question 16

What are the 3 factors that determine the rate of flux?

Answer 16

1. Number of transporters in the membrane
2. Extent of transporter saturation, which will affect Transporter affinity and ligand concentration.
3. Rate of transporter conformational change.

Question 17

What are the three types of transport channels?

Answer 17

Ligand sensitive
Voltage sensitive
Mechanosensitive

Question 18

_____ is bulk flow of water across a membrane (swelling or shrinkage if flow is large).

Answer 18

Osmosis

Question 19

Water diffuses through channels called ______.

Answer 19

Aquaporins *Water is polar therefore needs to use channels.

Question 20

Osmolarity of ECF = ?

Answer 20

300 mOsm

Question 21

What are the 3 types of External solutions?

Answer 21

Isotonic = 300 mOsm of non-penetrating solutes = np change in cell volume

Hypotonic = 300 most of non-penetrating solutes = cells shrink

Question 22

What is Isoosmotic?

Answer 22

= 300 mOsm of non-penetrating PLUS penetrating solutes.

Question 23

What is Hypoosmotic?

Question 24

What is Hyperosmotic?

Answer 24

> 300 mOsm of non-penetrating PLUS penetrating solutes.

Question 25

T or F, A solution can be Hyperosmotic and Isotonic at the same time?

Answer 25

True, For example, it has 300 mosm of non-penetrating solute and 100 mosm of penetrating solutes!

Question 26

What are the 2 types of endocytosis?

Answer 26

Pinocytosis = Cell drinking (Engulfment of small particles and fluid) *can be preformed by any cell.
Phagocytosis = engulfment of large particles or cellular debris, preformed by specialized cells- phagocytes.

Question 27

What is Exocytosis?

Answer 27

Reverse of Endocytosis, replaces membrane patches internalized through endocytosis!

Question 28

K+ is found more _______ the cell.

Answer 28

Inside the cell.

Question 29

Na+ is found more _______ the cell.

Answer 29

Outside the cell.

Question 30

Electrical charge difference between the inside and outside of the cell is called _____.

Answer 30

Voltage

Question 31

The plasma membrane must have ______. (in regards to voltage)

Answer 31

Resistance

Question 32

Current is described as what?

Answer 32

Movement of Ions across membrane

Question 33

What is Ohms law?

Answer 33

V = IR (Voltage = Current X Resistance)

Question 34

What is Nernst Equation and what does it Describe?

Answer 34

Ex = (58/z) log10 ([X1]/[X2])

It Relates Equilibrium voltage (E) between 1 and 2 and the concentration difference between 1 & 2.

Question 35

Log10 0.1 =

Answer 35

-1

Question 36

Log10 1 =

Answer 36

0

Question 37

Log10 10 =

Answer 37

1

Question 38

Log10 100 =

Answer 38

2

Question 39

What is a Diffusion potential?

Answer 39

A Transient (temporary potential) that is due to the asymmetric ion flow, an imbalance in the flow of an ion or several ions between two compartments.

Question 40

Can a diffusion potential be maintained at a steady level over time?

Answer 40

Yes

Question 41

What is resting membrane potential?

Answer 41

Describes the conditions of the living, resting cell.

• Higher K+ inside
• Higher Na+ outside
• The membrane of resting cell favors K+ permeability 60 times more than Na+