Cell Membrane

Question 1

Functions of cell membranes

Answer 1

Physical barrier
- separates intracellular fluid from extracellular fluid

Gateway for exchange
- controls movement of solutes: allows some to cross and some not (semipermeable)

Communication
- home to receptors that detect physical and chemical stimuli and starts cascade of response to stimuli

Cell structure
- some membrane proteins hold cytoskeleton proteins to give structure

Question 2

Structure of cell membranes

Answer 2

Made mostly of protein and lipids
Ratio of protein to lipid differs

Fluid mosaic (proteins are afloat on a sea of lipid)

Question 3

What type of lipids are apart of the cell membranes

Answer 3

Glycolipids
Phospholipids
Cholesterol
Sphingolipids

Question 4

What proteins are apart of cell membranes

Answer 4

Integral

peripheral

Question 5

Phospholipid membrane

Answer 5

Makes up majority

Different varieties

Polar heads at water

Non polar tails at inside

Question 6

Cholesterol in the membrane

Answer 6

Flat molecule that slips between fatty acid tails

Cholesterol regulates membrane fluidity

Slows diffusion of molecules across membrane

Question 7

Sphingolipids in membrane

Answer 7

Sphingolipids tend to aggregate together = lipid rafts

Rafts have high density of cholesterol

Question 8

Some proteins associate only with _____ leading to areas of specialization on cell membranes

Answer 8

Lipid rafts

Question 9

What might play a role in Alzheimer’s disease

Answer 9

Errors in lipid rafts

Question 10

What is a physical difference of sphingolipids from phospholipids

Answer 10

Shingolipids have longer tails

Question 11

Integral membrane proteins

Polytypic

Answer 11

Permanently attached to cell membrane

Polytypic are transmembrane proteins
-span the lipid bilateral once or several times approx 20-25 hydrophobic AA to span the membrane

Question 12

Integral proteins monotypic

Answer 12

Are permanently attached to the membrane from one side

Lipid anchored proteins

• modified by addition of a fatty acid
• often associated with lipid rafts

May have strongly hydrophobic sections that allow it to associate with Lipid portion of bilayer

Question 13

Peripheral proteins

Answer 13

Associate noncovalently with integral proteins or polar heads of phospholipids

Question 14

Cytoskeleton

Answer 14

Not a membrane protein but often interact with membrane proteins

Flexible 3D skeleton of fibrous proteins throughout the cytoplasm

Question 15

Extracellular matrix

Answer 15

Membrane proteins and secreted protein found on the extracellular side of cell membranes

Forms a husk around cells
Highly variable glycosylation
Contribute to cell strength

Question 16

Muscular dystrophy

Answer 16

A disease of cytoskeleton

Provides a link between cytoskeleton and extracellular matrix

Results in easily damaged muscles in severe forms repeated damage causes muscle to eventually waste away