Section 5.1 & 5.2 (JL&MP)

Question 1

What is Selective Permeability?

Answer 1

A feature and a function of the plasma membrane that is essential to survive by regulating the passage of some substances while preventing others from entering the cell. Supplement.

Question 2

What does Amphipathic mean?

Answer 2

Has both a hydrophilic and hydrophobic region; phospholipids as an example

Question 3

What is the Fluid Mosaic Model?

Answer 3

Describes the cell membrane, fluid refers to the flowing/always moving aspect of the membrane, and the mosaic depicts the proteins and other molecules on the membrane.

Question 4

What type of interactions holds the fatty acid chains of the cell Membrane together?

Answer 4

Hydrophobic interactions

Question 5

What can the proteins in the membrane be attached to?

Answer 5

Cytoskeleton (inside cell), or the extra-cellular matrix (outside cell)

Question 6

Explain the role of cholesterol in the membrane

Answer 6

temperature decreases = still remain fluid - cholesterol prevents side chains from attaching (as do the kinks in tail where there are double bonds prevent them from becoming solid). Warm temps - cholesterol holds the membrane together by being a reservoir of weak bonds between lipids.

Question 7

What happens when a Membrane solidifies?

Answer 7

its permeability changes and enzymatic proteins in the membrane may become inactive.

Question 8

Describe the Evolution of Differences in Membrane Lipid Composition with respect to temperature

Answer 8

• Fishes that live in the extreme cold have membranes with high amounts of unsaturated hydrocarbon tails, which allows their membranes to remain fluid
• The ability to change lipid composition to adapt has evolved in organisms that live where temperatures may vary

Question 9

Membrane Proteins and Their Functions

Answer 9

• Lipids = fabric of membrane, while proteins = function of membrane
  *

Question 10

Integral Proteins

Answer 10

• Penetrate the hydrophobic interior of the lipid bilayer

Question 11

Peripheral Proteins

Answer 11

• Not embedded in the lipid bilayer, loosely bound to the surface of the membrane

Question 12

Cell-Cell Recognition

Answer 12

• Cell-cell recognition is a cell’s ability to distinguish one type of neighboring cell from another and is crucial to the functioning of an organism

Question 13

Importance of Cell-Cell Recognition?

Answer 13

rejects foreign and dangerous cells, sorts cells into tissues and organs

Question 14

Membrane Carbohydrates

Answer 14

• Short, branched chains fewer than 15 sugar units
• Some covalently bonded to lipids → glycolipids
• Some covalently bonded to proteins → glycoproteins

Question 15

Supramolecular structure

Answer 15

Multiple molecules interacting with one another (quarternary structure) with emergent properties beyond the individual molecules (the whole is greater than the sum of the parts)

Question 16

What is the most important property of a supra molecular structure

Answer 16

Ability to regulate transport across cells

Question 17

What helps explain how membranes regulate the cells molecular traffic

Answer 17

The Fluid Mosaic Model

Question 18

What can move across the cell membrane without the help of proteins?

Answer 18

Small molecules & ions

Question 19

How does the selective permeability of the cell membrane affect it?

Answer 19

It is able to take up some small molecules and exclude others

Question 20

Why can CO₂, O₂, and other lipids/hydrocarbons cross the membrane easily?

Answer 20

They are non-polar and can dissolve in the lipid bilayer

Question 21

Why is it difficult for sugars like glucose to cross the membrane?

Answer 21

They are polar and the hydrophobic portion of the membrane makes it difficult for them to get across.

This also affects all polar molecules and ions, including water

Question 22

The lipid bilayer is one part of the membrane’s selective permeability. What is another type of molecule that helps?

Answer 22

Proteins

Question 23

Transport proteins

Answer 23

are proteins that facilitate the movement of molecules across the cell membrane

Question 24

Transport proteins in passive transport

Answer 24

Channel proteins, involved in passive transport, are hydrophilic, allowing polar molecules and ions to pass through

Question 25

Most aquaporins have ___ polypeptide subunits, and can allow up to ___ water molecules per second

Answer 25

4, 3 billion

Question 26

Transport proteins in active transport

Answer 26

Carrier proteins hold on to their passengers and change shape to move them across the membrane against the concentration gradient

Question 27

For a transport protein to be effective, it needs to be ___ (+/-) efficient at moving molecules than them crossing the membrane on their own

Answer 27

more effective