Physiology- What is a Membrane?

Question 1

Permeability of membrane

Answer 1

Selectively permeable

Question 2

Importance of the membrane

Answer 2

• controls entry of nutrients and exit of waste and secretory products
• maintain differences ion conc inside and out of cell
• helps join cells to form tissue and organs
• allows a cell to respond to signals in the cell’s environment

Question 3

what are the main principal constituents of the membrane?

Answer 3

lipid, protein and carbohydrates

Question 4

How does a phospholipid bilayer form?

Answer 4

Polar end of phospholipid orients towards water (polar) and non-polar end orients away from water

Question 5

Which type of molecules can cross membrane fairly freely?

Answer 5

small, uncharged, polar molecule

Question 6

3 main functions of lipid bilayer

Answer 6

1. forms basic structure of membrane
2. hydrophobic interior acts as a barrier
3. responsible for fluidity of membrane, allowing it to change shape

*primary barrier to diffusion

Question 7

The 2 classes in which membrane proteins can belong to

Answer 7

Peripheral or integral

Question 8

peripherally associated membrane proteins

Answer 8

not embedded within the membrane; they adhere to the cytoplasmic/ ec surface of the plasma membrane

Question 9

integral membrane proteins

Answer 9

intimately associated with the lipid bilayer in 3 ways

Question 10

in which 3 ways can integral membrane proteins be intimately associated with the lipid bilayer?

Answer 10

1. transmembrane proteins- span the lipid bilayer at least once
2. embedded but do not cross the bilayer
3. linked to lipid component/ fatty acid derivative that intercalates into the membrane

Question 11

Functions of integral membrane proteins

Answer 11

• ligand binding receptors
• adhesion molecule, which is important in controlling shape, growth and differentiation
• transmembrane movement
• pores and channels
• carriers
• pumps
• enzymes
• signalling

Question 12

What makes up the glycocalyx layer?

Answer 12

glycoproteins and glycolipids

Question 13

Role of membrane carbohydrates

Answer 13

self-identify markers, enabling cells to interact with each other and ensure cells do not overgrow themselves

Question 14

Tight junctions

Answer 14

joins lateral edges of epithelial cells near nominal/ apical membranes

Question 15

Desmosomes

Answer 15

Adhering junctions which anchors cells together, especially in ‘stretchy’ tissues

Question 16

Gap junctions

Answer 16

communicating junctions which allow movement of change carrying ions and small molecules between 2 adjacent cells