Lec 5. Single cell dynamics, membrane structure

Question 1

Prokaryotic

Answer 1

bacteria and archea (no nucleus)

Question 2

Eukaryotic

Answer 2

protist, fungi, animal, plant cells (with nucleus)

Question 3

Organelle

Answer 3

a membrane bound structure found in a cell

Question 4

Ampipathic

Answer 4

Can be hydrophobic or hydrophillic

Question 5

Function of fluid cell membrane

What stabilizes membrane fluidity

Answer 5

• phospholipids drift laterally in the plane of membrane
• held together by weak hydrophobic interactions that can be broke
• due to kinks (2x bonds) which results in unsaturated hydrocarbons

Cholesterol= membrane buffer (solidify at moderate) (fluid at low temp)

Question 6

Plasma membrane structure

(Role of each macromolecule)

Meaning of fluid mosaic model

Answer 6

Thin barrier
Lipids: Phospholipids (amphipathic) w/ hydrophobic tail and hydrophilic head, forms main fabric of membrane forms bilayer, cholesterol
Proteins: Can be embedded in bilayer (transmembrane) and peripheral proteins
Carbohydrates: on extracellular surface (glycoproteins and glyco-lipids
Nucleic acids: NONE

tapestry of multiple types of molecules that are always moving (fluid)

Question 7

Role of cell membrane

Answer 7

serve as a barrier between inside and outside of cell

Question 8

Roles of membrane proteins

Answer 8

1. Transport
2. Enzymatic activity
3. Signal transduction
4. Cell-cell recognition
5. Intercellular joining
6. Attachment to cytoskeleton and ECM

Question 9

How can infections (ie HIV) infect a cell?

How can antibiotics hinder the spread of HIV?

Answer 9

Viral membrane proteins mimic the structure of natural ligands for CD4 anf CCR5 receptors to gain access into host cells
- Cells lacking CCR 5 are resistant to HIV infection

Maraviroc (HIV drug) blocks CCr5 receptor in host cell

Blocking CD4 has too many side effects

Question 10

How does COVID (SARS coV-2) hijack membrane proteins?

Answer 10

1. Spike proteins bind to ACE 2 receptors on the target cell
2. protease binds to and cleaves the ACE-2 receptor
3. Spike protein is activated
4. Results in viral entry/spreading into cell