Ch 6: Cell Membranes

Question 1

Fluid Mosaic Model

Answer 1

• Membranes are mostly made of lipids (phospholipids)
• Are lipid bilayers with hydrophilic heads and hydrophobic tails
• Lipids move aka fluid mosaic model

Question 2

integral membrane proteins

Answer 2

o Traverse the bilayer (have transmembrane domains)

o Embedded into one side of the lipid bilayer and don’t traverse it

Question 3

peripheral membrane proteins

Answer 3

o Interact with polar head groups of lipids

o Interact with integral membrane proteins

Question 4

Lipid rafts

Answer 4

• Float in the phospholipid membrane and are mobile
• Contain sphingomyelin and cholesterol
o Sphin has 2 long hydrophobic tails and a polar head
o Cholesterol has a small polar head and a long nonpolar/hydrophobic region
o Have complementary shapes

Question 5

cell adhesion

Answer 5

• Cell adhesion is when cells interact with each other

Question 6

tight junctions

Answer 6

• Strong protein-protein interactions, which form tight seals
• Tight seals are spaced (quilts)
• Pockets of intercellular space

Question 7

desmosomes

Answer 7

• Have connections btw cells that resemble a mesh, which allow the intercellular space to be continuous

Question 8

gap junctions

Answer 8

• Proteins that form tubes btw cells, called channels

* Channels allow molecules to pass from one cell into a neighboring cell

Question 9

ECM

Answer 9

animal cells’ protein mesh that surrounds them

o Provides cell rigidity
o Made up of collagen fibers plus proteoglycans
o Integrin proteins bind to the extracellular matrix and traverse the membrane to the inside of the cell, where they interact with the cell’s cytoskeleton

Question 10

Simple diffusion

Answer 10

o Hydrophobic molecules
o Higher to lower concentration
o Does not require an input of energy

Question 11

facilitated diffusion

Answer 11

o Requires a transmembrane protein, which has a binding site for a particular substance
o Upon binding, the protein assists the substance thru the membrane in the direction of higher to lower concentration

Question 12

Diffusion through a channel

Answer 12

o Requires an integral membrane protein with a channel, which has specificity to permit one or a few types of ions or molecules thru the channel
o Involves “gated channels”
• Voltage gated sodium channel

Question 13

active transport

Answer 13

o	Requires a transmembrane protein
o	Substance can be transported against its concentration gradient by coupling transport to ATP hydrolysis
•	Uniporters: 1 sub 1 dir
•	Symporters: 2 sub 1 dir
•	Antiporters: 2 sub 2 dir

Question 14

secondary active transport

Answer 14

o Involves a transmembrane protein that transports one substance with its concentration gradient while transporting another substance against its concentration gradient