Membranes

Question 1

Describe movement of phospholipid bilayer components

Answer 1

Question 2

What are weird ways integral proteins can be attached to the membrane ?

Answer 2

Question 3

Give examples of adhesion molecules which are integral membrane proteins

Answer 3

Form physical contacts with the surrounding extracellular matrix or with cellular neighbours
Important in regulating cell shape, growth and differentiation, allowing the cell to adapt to its immediate surroundings
E.g. integrins (cell-matrix adhesion molecules)/ cadherins (cell adhesion molecules) etc.

Question 4

Give an example of where integral membrane proteins are enzymes

Answer 4

Integral membrane proteins can also be enzymes
-Membrane-bound enzymes in the mitochondria that are part of the electron transport chain

Question 5

What are Docking-marker acceptors ?

Answer 5

Membrane proteins
-Located on the inner membrane surface
-Interact with secretory vesicles leading to exocytosis of the vesicle contents: important in the nervous system

sperm things are the docking proteins

Question 6

What does sugar coating of cells refer to ?

Answer 6

Small amount of membrane carbohydrate cell outer surface of cells
-Short carbohydrate chains are often bound to membrane proteins and to a lesser extent lipids: glycoproteins and glycolipids
-Together they form a layer called the glycocalyx (“sweet husk”) which coats cells

Question 7

What is the purpose of short carbohydrate chains on the outer membrane surface of cells ?

Answer 7

Serve as self-identity markers that enable cells to identify and interact with one another

Different cell types have different markers.
-Important in cell-to-cell interactions, e.g. during embryonic development.

Role in tissue growth
-Cells do not overgrow their own territory
-Exception: cancer cell growth – abnormal

Question 8

How can cells be directly connected to eachother ?

Answer 8

Tight junctions
-Join the lateral edges of epithelial cells near their luminal (apical) membranes (tight or leaky)
-Prevents movement of stuff between cells, seals intercellular space; many in bladder so no urine leaks
-Often have specilised apical regions, with different proteins expressed from lateral surfaces
-Often at apical most lateral regions of cell; seperates apical and basolateral regions

Desmosomes
-Anchor cells together, especially in tissues subject to stretching (e.g. skin, heart, uterus)
-Mainting structural integrity in strong heart contractions
-Prevents cells pulling apart under stress

Gap junctions
-‘Communicating’ junctions that allow the movement of charge carrying ions and small molecules between two adjacent cells.
-important in electrical conduction

Also, adherens junctions