What Is A Membrane?

Question 1

Major components of cell plasma membrane:

Answer 1

Cholesterol provides stability

Fluid (phospholipids constantly moving)

Small, uncharged molecules can diffuse through membrane. Charged, water-soluble molecules can’t

Question 2

How are various membrane components arranged?

Answer 2

Phospholipid bilayer:
- Hydrophobic tails, hydrophilic heads
- Forms bilayer in aqueous solutions

Peripheral proteins: Adhere to surfaces on membrane (not embedded)

Integral proteins:
- Transmembrane proteins span bilayer
- Some integral proteins are only partially embedded

Question 3

Molecular structure of membrane lipids:

Answer 3

Cholesterol:
- Fused carbon rings with hydrocarbon tail

Glycocalyx:
- Made of glycoproteins and glycolipids
- Layer that coats cell

Question 4

Functions of the lipid bilayer

Answer 4

Impermeable to charged molecules (ions, proteins, sugars)

Hydrophobic interior acts as a barrier allowing cell to have a different environment from outside

Responsible for fluidity

Question 5

How does cholesterol affect membranes?

Answer 5

Aids in stiffening the membrane and can flip easily

Question 6

Types of membrane proteins and their functions:

Answer 6

Ligand-binding:
- Bind external signalling molecules

Adhesion molecules:
- Form physical contacts with surrounding extracellular matrix
- Regulates cell shape, growth and differentiation

Pores and channels:
- Allow passive transport

Carriers

Membrane bound enzymes

Intracellular signalling integral proteins

Question 7

How do proteins aid in cell diversity?

Answer 7

It is the proteins within the plasma membrane that confer distinct cellular properties and lead to diversity of cell types/ functions