Plasma membrane & structure

Question 1

What is the Plasma Membrane?

Answer 1

• The overcovering= a bilayer that ALL CELLS HAVE
• Acts as a barrier & a very selective door for things that need to be let in (food) & let out (waste)= semipermeable
• HOMEOSTASIS BEIBI

Question 2

What does the Plasma Membrane separate?

Answer 2

-Separates external from internal compartments (extracellular fluid from cytoplasm)

Question 3

What is the structure of the Plasma Membrane?

Answer 3

• Thin, flexible covering over ENTIRE SURFACE of cell

- Thickness is less than 10nm (1 millionth of a cm)

Question 4

What makes the Plasma Membrane so flexible?

Answer 4

-phospholipids in the membrane are held together by noncovalent interactions (hydrophobic effect)= AREN’T HELD TOGETHER BY RIGID COVALENT CONNECTIONS

Question 5

What is the Plasma Membrane based on?

Answer 5

• Phospholipid bilayer w/ nonpolar heads on the inside

- Also contains Cholesterol, Glycoproteins, Glycolipids

Question 6

How do we know that membranes have a bilayer?

Answer 6

• Area of the phospholipid is twice the surface area of starting cells (P.L in cell formed a layer that’s 2 molecules thick= bilayer)
• Monolayer area is twice the RBC surface area= membranes in cells is a bilayer

Question 7

What makes the Plasma Membrane complex?

Answer 7

-Multiple lipid & protein components

Question 8

What are the lipid components?

Answer 8

• Cholesterol, steroid (4 carbon rings)
• Sphingolipids (have 2 nonpolar tails but connected differently w/ a non-glycerol core
• Glycolipids (have carbs attached)

Question 9

What are the Protein components?

Answer 9

• Integral membrane proteins (span across the membrane & tightly attached to it)
• Peripheral membrane proteins (sit only on the surface & loosely bound it membrane)

Question 10

What is the complete membrane described by?

Answer 10

-Fluid Mosaic Model

Question 11

What does the Fluid Membrane Model describe?

Answer 11

• Membrane lipids & proteins that aren’t fixed can move laterally (in the plane of membrane)
• Integral membrane proteins float freely even though they are partially submerged in sea of lipid
• Peripheral membrane proteins can float freely on the surface (either extracellular or intracellular)