Membrane transport

Question 1

How does compartmentalization affect the cellular environment?

Answer 1

Having membranes blocks free diffusion, which creates different properties inside the cell vs the outside

Question 2

What creates the boundaries between body regions in animals to compartmentalize them?

Answer 2

Epithelia

Question 3

What are the two surfaces on an epithelial cell?

Answer 3

Apical, which faces a cavity, and basolateral, which faces another cell

Question 4

What is the basement membrane?

Answer 4

Permeable extracellular matrix that is between blood vessels and the epithelium

Question 5

What are the two types of membrane proteins?

Answer 5

Integral and peripheral

Question 6

What is an integral membrane protein?

Answer 6

Membrane protein that goes into the membrane

Question 7

What is a peripheral membrane protein?

Answer 7

Membrane protein that is associated with but not in the membrane

Question 8

What are the 4 types of junctions?

Answer 8

Tight, septate, desmosome, gap

Question 9

What are the two types of occluding junctions?

Answer 9

Tight (vertebrates) and septate (invertebrates)

Question 10

What is the function of a desmosome?

Answer 10

Maintain very tight contact between cells

Question 11

What is the function of a gap junction?

Answer 11

Communication through pores between the cytoplasm of two cells

Question 12

What are the two paths that a molecule can take to get across the epithelium?

Answer 12

Transcellular and paracellular

Question 13

What is the transcellular path?

Answer 13

The molecule goes through the membrane, into the cell, then back out through the membrane. Used by large molecules

Question 14

What is the paracellular path?

Answer 14

The molecule squeezes through the junction. Used for things like water and ions

Question 15

What is the bulk solution?

Answer 15

The portion of the solution not in contact with the membrane

Question 16

What is simple diffusion?

Answer 16

Solutes move down their concentration gradient, no energy input or carrier required

Question 17

What is osmosis?

Answer 17

Simple diffusion of water

Question 18

What does the Fick equation tell us?

Answer 18

The rate of diffusion

Question 19

What is the purpose of a boundary layer? What animals have one?

Answer 19

Slows the diffusion of solutes from the animals into the environment. Seen in aquatic animals

Question 20

What is the electrical gradient of the cell?

Answer 20

The inside of the cell is negative, outside is positive

Question 21

How is diffusion affected when the solute is going down both its concentration and electrical gradient?

Answer 21

It goes fast

Question 22

What is the Donnan equilibrium?

Answer 22

The balance of both the electrical and concentration gradients on both sides of the cell membrane

Question 23

What is facilitated diffusion?

Answer 23

The solute goes down its concentration gradient, no energy input, but needs a transport protein to get across the membrane

Question 24

What are the 4 ways ion channels are regulated?

Answer 24

Voltage, mechanical, phosphorylation, ligand binding

Question 25

What is a permease?

Answer 25

A transport protein that isn't a channel

Question 26

What is a porin?

Answer 26

Large channels that let bigger molecules through

Question 27

What does the Na+/glucose symporter do? Which membrane in an intestinal epithelial cell is it found on?

Answer 27

Brings one Na+ (down gradient) and one glucose (against gradient) into the cell. Found on the apical membrane

Question 28

What does the Na+/H+ antiporter do?

Answer 28

Moves one Na+ into the cell and one H+ out

Question 29

What causes a voltage gated ion channel to open?

Answer 29

A change in voltage, when the membrane potential becomes negative on the outside and positive on the inside (aka action potential)

Question 30

What causes a phosphorylation gated ion channel to open?

Answer 30

Phosphorylation

Question 31

What causes a mechanically gated ion channel to open?

Answer 31

Physical stretching of the membrane

Question 32

What causes a ligand gated ion channel to open?

Answer 32

Ligand binding to a receptor

Question 33

What does the Na+/K+ ATPase do?

Answer 33

Maintains the electrochemical gradient of ions by using active transport to pump 3 Na+ out of the cell and K+ into the cell (both against their concentration gradients)

Question 34

What causes the confromational change in the Na+/K+ ATPase?

Answer 34

ATP hydrolysis

Question 35

What is membrane potential?

Answer 35

Difference of electrical charges across the cell membrane

Question 36

Which membrane is the Na+/K+ ATPase on in intestinal epithelial cells?

Answer 36

Basolateral

Question 37

How is glucose transported across the intestinal epithelium?

Answer 37

Enters through the Na+/glucose symport (secondary active transport), moves through the cell and out through a glucose transporter on the basolateral membrane (facilitated diffusion). Uses the gradient built by the Na+/K+ ATPase on the basolateral membrane