KINE 2P09: LECTURE TWO PART TWO

Question 1

Simple Diffusion

Answer 1

Movement of molecules from one location to another as a result of random thermal motion

Question 2

Flux

Answer 2

movement from one compartment to another, down a concentration gradient

Question 3

Factors that influence the rate of diffusion

Answer 3

1. Concentration- high to love
2. Temperature- diffusion on thermal motion
3. Mass/size of the molecule- diffusion larger moves slower
4. Surface area separating two regions- the narrow area will be slower, i.e. tunnel
5. Medium (e.g., air vs. water) - diffusion spread out less resistance
6. Distance- longer to diffuse over farther distance

Question 4

Diffusion Rate versus Distance

Answer 4

Diffusion is limited by distance. It is very slow if a substance has to diffuse a long distance. Therefore, moving solutes over large distances would not be an effective way.

Question 5

Simple diffusion through a membrane

Answer 5

Membranes act as a barrier that slows diffusion and is governed by Fick’s first law of diffusion.

Question 6

Fick’s first law of diffusion

Answer 6

whole equation: J = PA (Co–Ci)
* J = Rate of diffusion
* P = permeability coefficient
* A = surface area
* Co = concentration outside cell
* Ci = concentration inside cell

Question 7

The rate of diffusion is faster through a membrane if:

Answer 7

– The membrane surface area is larger
– The membrane is thinner
– The concentration gradient is larger- the difference between 2 sites
– Membrane permeability of a given molecule is greater

Question 8

Types of gated channels include

Answer 8

• Ligand-gated
• Voltage-gated
• Mechanically-gated

Question 9

ligand-gated:

Answer 9

A molecule binds to the receptor on or near the channel to change the conformation/shape and open it

Question 10

voltage-gated:

Answer 10

A change in the electrical charge in the membrane near to the channel to change the conformation/shape and open it- physical force

Question 11

Mechanically gated:

Answer 11

Deformation (e.g., stretch) of the membrane changes the confirmation to open it

Question 12

Membrane potential:

Answer 12

separation of electrical charges across plasma membrane

Question 13

Electrochemical gradient:

Answer 13

Because opposites charges (+ -) attract and like charges repel (++ / –), positive ions are driven into cells and negative ions driven out of cells

Question 14

Many molecules, including amino acids and glucose cross membranes yet are too polar to diffuse through lipid bilayers and too large to diffuse through channels. How does this happen?

Answer 14

cross cellular membrane

Question 15

Conformational changes of integral membrane proteins known as ____ bring these solutes into and out of cells; this movement is called _____

Answer 15

1. transporters
2. mediated-transport

Question 16

Types of mediated transport

Answer 16

-Facilitated diffusion
- Active Transport
– Primary active transport
– Secondary active transport

Question 17

Facilitated diffusion

Answer 17

-Transporter-mediated flux across a membrane down a molecule’s concentration gradient
-solute or molecule
-Not directly coupled to ATP metabolism
-ATP broke down no energy is used.

Question 18

Active Transport

Answer 18

Uses energy (ATP) to move a substance against (up) its concentration graduate across a membrane. From areas of low to high concentration

Question 19

Primary Active Transport- consumer of ATP

Answer 19

ATP hydrolysis provides energy to move molecules –thus, aka ATPase
* ATPases are responsible for large proportion of total body ATP usage
* Most common example: Na+/K+ ATPase pump
– Pumps 3 Na+ intracellularly (low [Na+] to extracellularly (high
[Na+]) ie salty banana ex.
– Pumps 2 K+ extracellularly (low [K+]) to intracellularly (high [K+]

Question 20

Secondary Active Transport

Answer 20

Movement of ions down electrochemical gradient (e.g., + charges driven inside cells and – charges driven outside cells) coupled to transport of another molecule against its concentration gradient

Question 21

Recall, cells are _____ charged inside and ____ charged outside

Answer 21

negative, positive

Question 22

Osmosis

Answer 22

Diffusion of water across plasma membranes
* Aquaporins: membrane proteins that enable water diffusion
– Number varies by cell type
– Some cells can transiently modify the number of aquaporins to alter water permeability
* E.g., Kidney epithelium – increases number of aquaporins to increase water retention during dehydration

Question 23

Osmolality

Answer 23

The total solute concentration of a solution is known as its osmolality (or osmolarity).

Question 24

study graph

Question 25

Endocytosis

Answer 25

regions of plasma membrane fold into the cell forming small pockets of intracellular membrane-
bound vesicles (bring substances in)

Question 26

Exocytosis

Answer 26

membrane-bound vesicles in cytoplasm fuse with the plasma membrane and release contents outside the cell
(eject substances out)
* Often triggered by increased Calcium concentration
* E.g., involved in neuronal release of neurotransmitters and thus is critical for cellular communication

Question 27

define Phagocytosis

Answer 27

process similar to eating, where the cell engulfs a molecule in order to move it to the interior of the cell.

Question 28

define pinocytosis

Answer 28

a process similar to drinking, it engulfs dissolved ions and other solutes in the liquid medium surrounding the cell.