Cell Membrane

Question 0

Diseases arise when cell malfunctions due to ?

Answer 0

genetic mutations or environmental conditions

Question 1

Cell are the fundamental unit of life because?

Answer 1

they can grow, adapt and reproduce/replicate

Question 2

Cell membranes

Answer 2

define the outer limits of cells and prevent organelles and other important molecules from diffusing out

Question 3

Cell membrane are permeable to?

Answer 3

gases and steroids

Question 4

Phospholipids

Answer 4

hydrophillic head group (diversity of head groups for protein recognition and cell signaling pathways)
hydrophobic tail (sat or unsat)

Question 5

What are the roles of proteins in the cell membrane?

Answer 5

transport, adhesion, detection

Question 6

Na gradient

Answer 6

145 mM out

15 mM in

Question 7

K gradient

Answer 7

120 mM in

4.5 mM out

Question 8

Ca gradient

Answer 8

0.001 mM in
1.2 mM out
leak in cell that lets Ca in triggers enzymatic process that leads to cell death

Question 9

How does cell membrane counteract its flexibility?

Answer 9

cytoskeleton under membrane helps provide stability/ structural support (actin linked to integral membrane proteins); prevents damage when external forces push and pull on membrane proteins
interaction of cytoskeleton with membrane proteins limits their diffusion and provides a stable framework for the proteins to attach
problem with cytoskeleton –> muscular dystrophy

Question 10

What is the biological role of ion gradients?

Answer 10

• cell communication, active neuron use ion gradients to generate action potentials
• regulate activity of enzymes; many enzymes need Ca for activity so low cytosolic calcium keeps enzymes inactive and can activate at certain times by raising cytosolic Ca

Question 11

Why is the diffusive nature of membranes important?

Answer 11

cell membrane is dynamic, i.e. proteins and lipids are rapidly moving within the membrane meaning lipids and proteins are randomly distributed in membrane without any other system acting on it , cells therefore expends a lot of energy to create domains in membrane that contain specific proteins and lipids that play roles in adhesion and communication

Question 12

What are the ways proteins can associate with the membrane?

Answer 12

1) integral membrane proteins ( receptors or channels); hard to remove
2) peripherally associated proteins; associate with specific head group; easy to remove; structural support and signaling events
3) anchor protein; covalent link between protein and phospholipid; outer leaflet; enzymes

Question 13

How does the structure of the membrane determine which chemicals it prevents from diffusing across it?

Answer 13

the tight packing of phospholipds in a membrane prevent large molecules from diffusing across and hydrophobic layer prevents diffusion of ions