Lecture 7 - Plasma Membrane

Question 1

what is the plasma membrane composed of?

Answer 1

75% phospholipids, 20% cholesterol, 5% polar glycolipids in the external layer

Question 2

what is cholesterol and how does it work?

Answer 2

it is a steroid lipid formed from a 4 ring structure, it immobilises the first few hydrocarbon groups in the phospholipid molecules making the bilayer less deformable

Question 3

what is the gylcocalyx?

Answer 3

membrane proteins associated with oligosaccharides, aids in cell adhesion

Question 4

what is the function of the bilayer?

Answer 4

regulates what enters + exits the cell, cell recognition and cell signalling

Question 5

what are the 5 types of vesicular transport?

Answer 5

endocytosis, exocytosis, phagocytosis, pinocytosis and transcytosis

Question 6

what is a symport?

Answer 6

she direction of travel with transport across the membrane

Question 7

what is an antiport?

Answer 7

opposite direction of travel across the membrane

Question 8

Describe endo vesicular transport

Answer 8

receptor mediated, Clathrin causes vesicles to form
phagocytosis - engulf large particles, macrophages, neutrophils
pinocytosis- small droplets of fluid taken in, doesn’t use receptors

Question 9

Describe the exo forms of vesicular transport

Answer 9

exhibited in all cells but important in secretory cells specifically enzymes and hormones and nerve cells

Question 10

Describe transcytosis

Answer 10

combines endo and exo, substances are passed through the cell, common in endothelial cells that line the blood vessels

Question 11

what are tight cell junctions?

Answer 11

Fusion of integral proteins of adjacent cells, prevent anything passing through the extracellular space

Question 12

what are adherens junctions?

Answer 12

plaque which attaches to membrane proteins and microfilaments of cytoskeleton to form adhesion belts and resists separation in contractile activities

Question 13

what are desmosomes and hemidesmosomes?

Answer 13

anchoring junctions held by linker protein filaments, clathrins or interns extending from plaques distributes tension and prevents tearing

Question 14

what are gap junctions?

Answer 14

adjacent cells connected by hollow cylinders called connexions made of trans membrane proteins found in electrically excitable tissues for synchronisation

Question 15

what are cell- cell junctions?

Answer 15

a Nexus (small gap) of 0.02 um between membranes filled with connective tissue

Question 16

what are longitudinal sections of cell-cell junctions?

Answer 16

regions where the nexus is very close and regular arrays of proteins (connexins) are found which allow passage of small ions and molecules between cells