Chapter 7: Cell Membrane

Question 1

How thick is the cell membrane?

Answer 1

8 nm

Question 2

What does the plasma membrane do?

Answer 2

It’s the boundary that separates the living cell from its surroundings.

Question 3

What does the plasma membrane exhibit?

Answer 3

Selective permeability

Question 4

What is selective permeability designed to do?

Answer 4

Keep damaging materials out of the cell

Allow needed material into the cell.

Help control chemical reactions in the cell

Question 5

What is the plasma membrane made of?

Answer 5

Phospholipids
Proteins
Cholesterol
Carbohydrates

Question 6

What did scientists find out about the membrane in 1915

Answer 6

It was made out of proteins & lipids

Question 7

What did scientists in 1935 Hugh Davison & James Danielli thought the cell membrane was like?

Answer 7

They thought the cell membrane was like a sandwich w/ the protein in the middle.

Question 8

In 1972, J. Singer & G. Nicolson thought the cell membrane was like?

Answer 8

They thought the proteins were within the bilayer

Question 9

What can phospholipids in the plasma membrane can do?

Answer 9

They can move within the bilayers

Question 10

How do most lipids move through move through bilayer?

Answer 10

They move sideways

Question 11

How do molecules rarely move in the bilayers?

Answer 11

Flip-Flop cross across the membrane

Question 12

What do the proteins in the membrane do?

Answer 12

The proteins determine the membrane’s specific functions

Question 13

What are peripheral proteins?

Answer 13

Bound to the surface of the membrane

Question 14

What are integral proteins?

Answer 14

They penetrate through the hydrophobic core

Question 15

What are the six major functions of membrane proteins?

Answer 15

Transport
Enzymatic Activity
Signal Transduction
Cell-Cell Recognition
Intercellular Joining
Attachment to the cytoskeleton and extra cellular matrix

Question 16

Diffusion

Answer 16

The movement of anything from a region of higher concentration to a region of lower concentration.

Question 17

The membrane structure is a result of what?

Answer 17

Selective Permeability

Question 18

What type of movement is diffusion for?

Answer 18

Small to no energy along the membrane

Question 19

How do hydrophilic molecules interact with the membrane?

Answer 19

They don’t cross the membrane easily & require a protein

Question 20

How do hydrophobic molecules interact with the membrane?

Answer 20

They can dissolve in the lipid bilayer, and pass through the layer rapidly

Question 21

What factors influences the behavior of the membrane?

Answer 21

of double bonds b/tw the carbons in the phospholipid’s hydrophobic tail

length of the tail

of cholesterol molecules in the membrane

Temperature

Question 22

What is the permeability of lipid bilayer w/ short & unsaturated hydrocarbon tail?

Answer 22

Higher permeability & fluidity

Question 23

What is the permeability of lipid bilayer w/ long & saturated hydrocarbon tail?

Answer 23

Lower permeability & fluidity

Question 24

What does cholesterol do to the membrane?

Answer 24

Adding cholesterol decreases membrane permeability.

Question 25

What does temperature do to the membrane?

Answer 25

Membrane fluidity decreases as temperature drops

Question 26

What are the three types of passive transport?

Answer 26

Diffusion Facilitated Diffusion Osmosis

Question 27

Diffusion

Answer 27

Cross membrane through phospholipid spaces

Question 28

Facilitated Diffusion

Answer 28

molecules cross using proteins within the membrane

Question 29

Osmosis

Answer 29

a specific type of facilitated diffusion/ allows for the diffusion of water across the selectively permeable membrane

Question 30

What is created by the difference in solute concentration?

Answer 30

Concentration Gradient

Question 31

What is diffusion along a concentration gradient?

Answer 31

Its spontaneous & goes from higher concentration to a lower concentration

Question 32

3 things to remember about diffusion

Answer 32

Substances diffuse down their concentration gradient No energy needed Passive transport

Question 33

Concentration Gradient

Answer 33

the unequal distribution of ions b/tw intercellular and extracellular fluids

Question 34

What do transport proteins allow the cell to do?

Answer 34

allows the passage of hydrophilic substances across the membrane

Question 35

What are channel proteins?

Answer 35

Proteins that have a channel that allows certain molecules & ions can use as a tunnel

Question 36

What do aquaporins facilitate?

Answer 36

the passage of water

Question 37

Cystinuria

Answer 37

no transport protein available to transport the amino acid cysteine from kidney back to blood, this creates kidney stones.

Question 38

How many water molecules do the channel protein aquaporin allow to pass through?

Answer 38

3 billion water molecules per second

Question 39

Tonicity

Answer 39

the way cell will lose or gain water depending on the solution it is in.

Question 40

Isotonic Solution

Answer 40

solute concentration is the same as that inside the cell; no net movement across the plasma membrane

Question 41

Hypertonic Solution

Answer 41

Solute concentration is greater than that inside the cell; cell loses water

Question 42

Hypotonic Solution

Answer 42

solute concentration is less than the inside of the cell, cell gain water

Question 43

Active Transport

Answer 43

Requires energy Used for moving up a concentration gradient Used for charged ions (like the nervous system) Used when a shape change occurs