Module 5 Membrane Transport

Question 1

What is the purpose of the plasma membrane?

Answer 1

1. Keeps components of the cell together in one place
2. Membrane provides a barrier between inside and outside - separates intracellular fluid from extracellular fluid
3. Selectively permeable - regulates movement of ions and molecules into/out of cell
4. Involved in cell-cell communication (receptors/ligands, see module 6)
5. Membrane attaches cells to extracellular matrix
6. Cytoskeleton attaches to membrane on the inside to maintain cell shape

Question 2

Phospholipid bi-layer

Answer 2

Amphiphilic in nature allowing it to interact with both water (extracellular side) and fats.
Contains a phosphate containing head which is the polar region and two fatty acid tails which are nonpolar.
There are two sets of phospholipids that are arranged with their fatty acid tails facing each other.

Question 3

Whenever diffusion is required in the body (like in the lungs or intestines), the surface area is maximized and the diffusion distance is decreased

Answer 3

true

Question 4

What is facilitated diffusion?

Answer 4

A form of transport that uses ion channels and transporters to move polar molecules across the membrane. It does not require energy.

Question 5

Describe how transporters work in facilitated diffusion?

Answer 5

A polar molecule acts as a solute/substrate and binds to the transporter which induces a conformational change and the molecule can enter the cell. Transporters work at a slower rate and can be saturated. Only one side is open at a time to the extracellular or intracellular fluid.

Question 6

Allows the movement of small nonpolar molecules such as oxygen, carbon-dioxide, fatty acids, and steroids to move across the membrane without the need for a membrane transporter. Requires no energy. Molecules move randomly and there is net movement with their gradient.

Answer 6

Simple Diffusion

Question 7

Describe how ion channels work in facilitated diffusion?

Answer 7

Ion channels move chemical ions or water across the membrane. Once open there is a complete pathway into the cell unlike transporters. They are triggered by a stimulus and are essential for the nervous system.

Question 8

Aquaporin, cation, or K+ channels

Answer 8

These are types of ion channels that are found in the cell.

Question 9

Osmosis

Answer 9

Facilitated diffusion of water via aquaporins.

Question 10

Osmolarity

Answer 10

The total concentration of solute in a liquid solution

Question 10

Isosmotic

Answer 10

The water solution and the cell have the same solute concentration. It’s homeostasis.

Question 11

Hyposmotic

Answer 11

The solution has lower solute concentration then the cell so the water will flow into the cell making it swell.

Question 12

Hyperosmotic

Answer 12

The solution has a lot more solute compared to the cell so water leaves the cell causing it to shrivel up.

Question 12

Active Transport

Answer 12

Utilizes energy such as ATP or couples molecular movement energy to move solutes against their concentration gradient. The net movement is from low to high concentration.

Question 13

Primary Active Transport

Answer 13

The pump hydrolyzes ATP to induce a conformational change to move solutes against their gradient. It’s never fully open. ATPase pump is a well known pump that moves potassium and sodium across their gradients. [pumpkin]

Question 14

Secondary Active Transport

Answer 14

The transporter will couple energy from the molecule moving down its concentration gradient to another molecule moving against it’s concentration gradient.

Question 15

Cells use all of these forms of transports to move molecules across the membrane. Cells use 40% of ATP to power movement of solutes against their concentration gradient.

Answer 15

True