FUNBIO 5 - Cell Ultrastructure: Cell Wall, Plasma Membrane

Question 1

What is the cell?

Answer 1

The cell is the most basic unit of structure and reproduction in all living organisms.

Question 2

What type of cells are animal and plant cells?

Answer 2

Animal and plant cells are Eukaryotic cells.

Question 3

What is a plasma membrane?

Answer 3

The plasma membrane separates the inside of the cell from the outside of the cell.

Question 4

What is the lipid bilayer?

Answer 4

The lipid bilayer is the universal basis of cell plasma membrane structure.

• It consists of two lipid layers made of amphipathic molecules with hydrophilic heads and hydrophobic tails.
• The outer face of the lipid bilayer has more saturated fatty acids (more cholesterol), while the inner face has more unsaturated fatty acids.
• Together they form a bilayer due to their chemical properties and spontaneous self-organization.

Question 5

What are the three classes that plasma membrane lipids fall into?

Answer 5

1. Phospholipids
   - choline
   - phosphate group
   - 3 carbon glycerol backbone
   - 2 fatty acid tails (unsaturated fatty acid tails pack loosely, allowing for fluidity / saturated tails pack tightly, creating rigidity and viscous effects)
2. Glycolipids
3. Cholesterol

Question 6

What is the fluid mosaic model?

Answer 6

A two-dimensional liquid consisting of phospholipids and embedded proteins & lipids that are continually moving.

Question 7

What is glycocalyx?

Answer 7

Glycocalyx is a covering that surrounds the plasma membrane of some cells. Its purpose is to protect the cell, keep other cells at a distance, and allow cells to recognize one another. It consists of polysaccharide side chains of proteins and lipids.

Question 8

What are the two classes of membrane proteins?

Answer 8

1. Integral membrane proteins
   - attached to the plasma permanently.
2. Peripheral membrane proteins
   - attached to integral membrane proteins to associate with regions outside the lipid bilayer.

Question 9

What are the two types of integral membrane proteins?

Answer 9

1. Transmembrane proteins
   - span entire plasma membrane
   - folded as alpha-helix or beta-barrel
   - acts as a transporter, enzyme, ion channel, or receptor
2. Integral monotopic membrane proteins

Question 10

What are Aquaporins?

Answer 10

Aquaporins are embedded in the plasma membrane to regulate the flow of water. Water can still enter the cell through the lipid bilayer via diffusion but moves more rapidly into the cell via aquaporins.

Question 11

Name seven types of channels/carriers of the lipid bilayer.

Answer 11

1. Anchoring (Integrins)
2. Passive Transport (diffusion of ions)
3. Active Transport (ATP)
4. Enzymatic Activity
5. Signal Transduction (receptors bind to hormones
6. Cell Recognition (antigens)
7. Intracellular Junction (adjacent cells are joined)