Chapter 5 Transport of Solutes and Water

Question 1

Solute

Answer 1

Materials that are dissolved in a solvent

Question 2

Transport

Answer 2

Movement of solutes and water across a cell membrane or epithelium

Question 3

Equilibrium

Answer 3

The state toward which an isolated system changes; that is, the state toward which a system moves when it has no inputs or outputs of energy or matter

A system is at equilibrium when it is internally stable and no further change is possible without system inputs or outputs

Question 4

Passive transport

Answer 4

Passive transport systems move material only towards equilibrium

They do not require energy!

Question 5

Active transport

Answer 5

Active transport systems may carry material away from equilibrium

They require energy!

Question 6

Passive (Simple) Diffusion

Answer 6

Diffusion: The movement of solutes or suspended substances from a region of high concentration to a region of low concentration via random thermal movement

Brownian motion: the random motion of particles suspended in a fluid resulting from their collision with the quick atoms or molecules in the gas or liquid

Simple diffusion does not require a channel. Molecules dissolve in the lipid bilayer as they cross the membrane.

Question 7

Examples of substances that cross the membrane via simple diffusion

Answer 7

lipid solutes such as steroids and fatty acid, molecular oxygen, nitric oxide, and the thyroid hormones.

Question 8

Factors that affect the rate of diffusion

Answer 8

• Concentration gradient
• Temperature
• Membrane permeability
• Membrane surface area
• Molecular weight of solute
• Diffusion distance
• Boundary layer

Question 9

What equation is used to calculate rate of diffusion?

Answer 9

Frick’s Equation

• J = rate of diffusion
• D = diffusion coefficient (mainly determined by permeability and temp)
• C1 and C2 = the two concentrations
• X = distance between the two concentrations

Question 10

Passive Transport/Facilitated Diffusion

Answer 10

Passive transport requires the assistance of protein molecules. A key point of passive transport is that it does not require energy.

Small compounds that facilitate the movement of ions across the membrane are called ionophores.

There are 2 types of passive transport.

The first is composed of a simple channel that allows specific ions to diffuse through it.

The second is carrier mediated (facilitated). In this case, the ion combines with the transporter resulting in a conformational change of the transporter that allows the ion access to the other side of the membrane.

Carriers, or transporters, can mask the electrical properties of the solute molecule.

Question 11

Passive Transport/Facilitated Diffusion

Ion channel types

Answer 11

• voltage-gated channel
• stretch-gated/ tension-gated channel

Question 12

Passive Transport/Facilitated Diffusion

Ion channel types 2

Answer 12

• phosphorylation-gated channel
• ligand-gated channel

Question 13

Types of Transporters

Answer 13

Question 14

An electrical gradient can also cause diffusion

Answer 14

Question 15

Donnan Equilibrium II

Answer 15

Now, we add a potassium salt to the left side. Here, the added potassium is freely diffusable across the membrane, while the anion is not.

Since the anion can’t move down it’s electrochemical gradient, the left side becomes more negative than the right. This sets up multiple effects.

• K+: K+ will tend to flow down its concentration gradient to the right. However, the electrical charge of the anion will prevent K+ from achieving chemical equilibrium. So, K+ will attain electrochemical equilibrium with more K+ on the left than on the right.
• Cl-: Since Cl has a negative charge it will be pushed through the left side of the membrane and driven up it’s concentration gradient until electrochemical equilibrium has been attained. This means that more Cl ions will be on the right than on the left.

Question 16

Primary Active Transport

Answer 16

• Unlike facilitated transport, active transport requires the use of energy to move molecules across the membrane.
• This transport mechanism is capable of moving molecules against the electrochemical equilibrium.
• uses ATP directly

Question 17

Donnan Equilibrium I

Answer 17

The Donnan equilibrium is the electrochemical equilibrium developed between two sides of a membrane that is not permeable to all of the ions.

If we have a two-chamber system and put KCl on the left of a semi-permeable membrane, the dissociated K+ and Cl- ions will flow down their electrochemical gradients until both the concentration and charges of each ion are equally distributed along both sides of the membrane.

Question 18

Secondary Active Transport Examples

Answer 18

Question 19

Secondary Active Transport Examples

Answer 19

Question 20

Types of Secondary Active Transport

Answer 20

• symporters
• antiporters

Question 21

Directions Na+, K+, Ca2+,Cl-, and A- ions move

Answer 21

• Na+ in
• K+ out
• Ca2+ in
• Cl- in
• A- out

Question 22

Osmosis

Answer 22

The movement of water down its concentration gradient.

Osmosis is the movement of water from a solution with low osmotic pressure to another with high osmotic pressure. The movement of water creates hydrostatic pressure. So, water movement into side 2 continues until the hydrostatic pressure there equals the osmotic pressure from side 1.

Question 23

Osmotic Pressure

Answer 23

The amount of pressure needed to stop osmosis.

Question 24

Tonicity

Answer 24

• Isotonic- The osmotic pressure inside the cell equals that of the extracellular space.
• Hypotonic- The osmotic pressure outside the cell is lower than that inside the cell (hypo=low).
• Hypertonic- The osmotic pressure outside the cell is greater than that inside the cell (hyper=high).