Membrane Transport and Excitable Cells

Question 1

What are integral membrane proteins?

Answer 1

Spans the plasma membrane, functions include channeling or transporting molecules across the membrane.

Question 2

What are peripheral proteins?

Answer 2

Attached to integral proteins. Can be enzymes, involved in attachment functions and shape changes, or act as receptors if they are on the cell surface

Question 3

What is the cytoskeleton?

Answer 3

A structure that helps cells maintain their shape and internal organization. Anchors to the plasma membrane

Question 4

What is the glycocalyx?

Answer 4

Mix of carbohydrates attached to lipids and proteins on outer face. Allows cells to recognize one another

Question 5

What happens to the glycocalyx when the cell becomes cancerous?

Answer 5

It changes, and can even change repeatedly, making it difficult for the immune system to keep up

Question 6

What is the function of cholesterol?

Answer 6

Reduces general membrane fluidity and stabilizes its structure.

Question 7

What does excess cholesterol do?

Answer 7

Causes the membrane to lose flexibility

Question 8

What are tight junctions?

Answer 8

Fusion of adjacent plasma membranes to prevent passage of molecules in between cells

Question 9

What are desmosomes?

Answer 9

Anchoring junctions: molecular linking of cells to resist mechanical stress

Question 10

What are gap junctions?

Answer 10

Molecular channels between cells to allow passage of cytoplasmic molecules

Question 11

What are connexons?

Answer 11

An assembly of 6 proteins called connexins that form the pore for a gap junction between the cytoplasm of 2 adjacent cells

Question 12

Connexons are ___ tissues

Answer 12

Electrically excitable

Question 13

What are some functions of plasma membranes?

Answer 13

Transport, intercellular joining, enzymatic activity, cell-cell recognition, receptors for signal transduction, attachment to extracellular matrix

Question 14

Plasma membranes provide:

Answer 14

A selectively permeable, hydrophobic barrier between the interstitial fluid and the cytoplasm

Question 15

What is interstitial fluid?

Answer 15

A filtrate of blood

Question 16

What does interstitial fluid contain?

Answer 16

Salts, sugars, amino acids, vitamins, hormones, metabolites, O2, CO2 and other gases

Question 17

How do water soluble molecules get across the plasma membrane?

Answer 17

Facilitated diffusion

Question 18

What is facilitated diffusion?

Answer 18

The passive movement of molecules across the cell membrane via the aid of a membrane protein. Requires a source of ATP

Question 19

What are 2 examples of facilitated diffusion?

Answer 19

Carrier proteins and channel proteins

Question 20

Characteristics of facilitated diffusion for water soluble substances

Answer 20

1) Specific
2) Not ATP requiring
3) Limited by carrier/channel saturation
4) movement DOWN a concentration gradient

Question 21

What is carrier-mediated facilitated diffusion?

Answer 21

Molecules are “helped” through the membrane by a membrane component

Question 22

When is carrier-mediated facilitated diffusion used?

Answer 22

With lipid insoluble molecules that are too large to pass through membrane channels/pores

Question 23

What are leaky channels?

Answer 23

Some ion channels that are always open

Question 24

Channel mediated facilitated diffusion is ___ due to ___ and ___ of ___ that line the channels

Answer 24

Selective
Pore size
Charges
Amino acids

Question 25

What are gated channels?

Answer 25

Ion channels that require some signal in order to be activated and opened

Question 26

What are aquaporins?

Answer 26

Water channels on many cells

Question 27

What is osmolarity?

Answer 27

Total concentration of solute particles in a solution

Question 28

What is tonicity?

Answer 28

Ability of a solution to change the shape of a cell by altering its water content

Question 29

What is an isotonic solution?

Answer 29

Solutions that contain the same concentration of water and solutes as the cell cytoplasm

Question 30

What is a hypertonic solution?

Answer 30

The solute concentration is higher than that inside the cell, and the solutes cannot cross the membrane

Question 31

What is a hypotonic solution?

Answer 31

The solute concentration is lower than that inside the cell

Question 32

Molecules that are ionically bonded have ___ than those that are covalently bonded

Answer 32

Greater osmotic power

Question 33

How are hypertonic solutions used in patients?

Answer 33

Used carefully and with monitoring for edema; pull water out of swollen cells

Question 34

How are hypotonic solutions used in patients?

Answer 34

Used carefully and with monitoring to rehydrate severely dehydrated patients

Question 35

Active transport requires ATP because the substance is:

Answer 35

1) Too large for pores and is lipid insoluble
2) Moving against its concentration gradient

Question 36

Active transport requires a carrier. What does it do?

Answer 36

Combines specifically and reversibly with a substance to help it across the plasma membrane

Question 37

Unlike facilitated diffusion, active transport solute pumps move substances:

Answer 37

AGAINST their concentration gradients

Question 38

What is a symporter?

Answer 38

A membrane protein that facilitates the simultaneous transport of two distinct substances across the cell membrane in the SAME DIRECTION

Question 39

What is an antiporter?

Answer 39

A membrane protein that transports two molecules across the cell membrane at the same time in the OPPOSITE DIRECTION

Question 40

Does passive transport require energy?

Answer 40

No

Question 41

Oxygen and water enter the cell through:

Answer 41

Simple diffusion

Question 42

How do aquaporins work?

Answer 42

The inside of the channel protein is hydrophilic, drawing water to/through it