Cellular Organization 1

Question 1

List the domains of cellular life

Answer 1

• Bacteria
• Archaea
• Eukaryotes

Question 2

Describe the ultrastructure of the cell membrane

Answer 2

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Question 3

List the 3 major classes of membrane lipids

Answer 3

1. Phospholipids
2. Cholesterol
3. Glyclolipids

Question 4

Describe the structure and function of phospholipids in the plasma membrane

Answer 4

• The most abundant membrane lipid
  *

Question 5

Describe the structure and function of cholesterol in the plasma membrane.

Answer 5

• 2nd most abundant component in plasma membrane
• Has a role in affecting fluidity
  
  • Depends on temperature
    
    • Normal temp = ridgidity
    • Low temp = increases fluidity
    • High temp = ridgidity

Question 6

Describe the structure and function of glycolipid in the PM

Answer 6

• Least numerous in PM
• Found only on the outer leaflet of PM
• Has sugar attached to them
• Cell recognition

Question 7

List the 2 major classes of membrane proteins

Answer 7

1. Integral membrane proteins
2. Peripheral membrane proteins

Question 8

Describe the categories of integral membrane proteins.

Answer 8

1. Pumps/carriers/transporters
2. Channels
3. Receptors
4. Linkers
5. Enzymes
6. Structural proteins

Question 9

Describe the freeze fracture technique to visualize integral membrane proteins

Answer 9

• The fracturing occurs in the lipid bilayer, splitting the layers to show proteins in the membrane

Question 10

Describe the structure and function of the glycocalyx

Answer 10

• “Sugar-coating” on the outside of cells
• Function:
  
  • Help establish microenvironemnt at cell surface
  • Protection
    
    • Mechanical and chemical damage
  • Cell recognition
  • Cell to cell interacation
    
    • Lectins: carbohydrate binding proteins

Question 11

List the 2 major types of vesicular transport

Answer 11

• Exocytosis: substances exit the cell by the fusion of a vesicle with the PM
  
  • Regulated
    
    • Secretory cells (endocrine, exocrine, neurons)
    • Not exited immediately; only when stimulus is receivied
  • Constitutive
    
    • Substance for export continuously delivered to PM
    • Fibroblasts: produce proteins for ECM (collagen, elastin, proteoglycans)

Question 12

List and describe the three different mechanisms of endocytosis.

Answer 12

• Receptor-mediated endocytosis: selective uptake of large molecules
  
  • Cargo-specific
  • Clathrin-dependent
• Pinocytosis
  
  • non-specific
  • clathrin-independent
• ​Phagocytosis
  
  • Clathrin-independent
  • actin-dependent

Question 13

Describe the precise targeting of vesicles within the cell.

Answer 13

• Snares are proteins involved in vesicle transport
• v-Snares interact with t-Snares

Question 14

Describe receptor-mediated endocytosis

Answer 14

1. Receptor-mediated endocytosis: selective uptake of large molecules and particles
   
   1. Clathrin-dependent process
   2. Clathrin coated pits
      
      1. Clathrin molecules interact with cargo receptors via Adaptin
      2. Clathrin forms a basket-like cage à drives vesicle formation
      3. Dynamin mediates the vesicle pinching-off from the PM

Question 15

describe pinocytosis

Answer 15

• cell-drinking
• non-specific ingestion by small vesicles
  
  • constitutive (constantly occurring)
• Invagiation of the PM
  
  • no receptor proteins
  • clathrin-independent
• Vesicle pinches off
• Fusion with lysosome

Question 16

describe phagocytosis

Answer 16

• Ingestion of large particles
• Generally performed by specialized phagocytes
  
  • Macrophage
  • Neutrophil
• Extension of psudeopods
  
  • dependent on actin microfilament polymerization
• Phagosome fuses with lysosome