Cell Bio 10

Question 1

Types of Integral Membrane Proteins that Move Molecules/ions across the membrane

Answer 1

Channels
Transporters
-Uniporter
-Symporter
-Antiporter
ATP-Powered Pumps

Question 2

Driving Force of Facilitated Transport

Answer 2

Concentration Gradient

No energy required

Question 3

Types of Facilitated Transporters

Answer 3

Pores: a hole through the plasma membrane

Channels: gated version of the pore

Gates

Question 4

Movement of ______ substances through a ______-_____ pathway so they don’t come in contact with ______ ______ of the membrane

Answer 4

hydrophilic
protein-lined
hydrophobic interior

Question 5

Facilitated diffusion is

Answer 5

Faster than predicted by passive diffusion

Specific

Saturable: Glucose can only get through this channel at a certain rate; even if there is a lot of glucose not all of it will transport at a certain rate

Question 6

Facilitated Transport Example

Answer 6

Glucose Uniporter

Question 7

Pores and Channels

Answer 7

Integral membrane proteins creat holes in the membrane, large enough for solutes to pass through.

Sized-Based Exclusion

Specificity

Question 8

Size Selectivity

Answer 8

The channel contains hydrophilic amino acids lining the channel, these proteins have residues in them that can bind to the specific molecule that is passing through.

K+ is surrounded by oxygen atoms in water in solution.

The oxygen in the K+ resting channel has the same spacing as water surrounding K+ ion.

K+ will favourably pass through but Na+ will not.

Question 9

K+ Resting Channel

Answer 9

Plasma membrane freely permeable to K+ due to open resting channels, not permeable to Na+ or Cl-

Selectivety of the transporter can lead to significant electric potential across the membrane without any input of energy beyond the inherent concentration gradient.

Electrical charge present on membranes due to the potassium resting channel.

All cells have a negative charge on the plasma membrane because of the potassium resting channel.

Question 10

Gates

Answer 10

Normally closed bu open when needed

Ligand gated/Voltage gated

Ligands opens channel by a change in gate conformation.

Specific, saturable, can be ligand or voltage gated, rely on a concentration gradient.

Question 11

Primary Active Transport

Answer 11

ATP-powered pumps

Classifed by subunit composition, molecules transported, mechanism of action.

Question 12

Types of ATP-Pumps

Answer 12

P-Class: H+, Na+, K+, Ca++

V-Class: H+ only

F-Class: H+ only

ABC-Type: Many small molecules
ATP binding cassette

Question 13

Na+/K+ pump

Answer 13

P-class Pump

Responsible for the Na+/K+ concentration gradient

3 Na+ out + 2 K+ in per ATP

Question 14

Muscle Ca++ ATPase

Answer 14

P-class Pump

Reversible phosphorylation = conformational change

Calcium is pumped out of the cytosol into the sarcoplasmic reticulum

working against a concentration gradient.

2 Ca2+ out /ATP

Question 15

ABC-class pumps

Answer 15

ATP-Binding Cassette

Not restricted to ions

Move very large molecules into the cell, flippases move things across the PM by flipping them in.

Moves molecules between leaflets

Move against the concentration gradients

Question 16

Secondary Active Transport

Answer 16

Co-transporter

Antiporter, symports

Coupled transport between two different molecules.

• one with gradient
• one against gradient

Use ion gradients generated by ATP-powered pumps, then couple the free energy associated with these ions going back along their concentration gradient to the import or export of other molecules against their concentration gradient.

Question 17

Na+ Glucose Symporter

Answer 17

Energy availably following Na+/K+ ATPase and K+ resting channel functions: concentration/electrical gradient

Harness this energy for other uses

2 Na+ down gradient, 1 glucose against concentration gradient

Use the free energy of sodium moving down its concentration gradient, glucose can move in with it.

Question 18

Co-transport in Epithelial Cells

Answer 18

Apical surface (luminal side)

Basal Surface (sitting on the extracellular matrix)

Epithelial gut cells are stuck together, gap junctions and tight.

Gap junctions allow ions to flow between the cell, tight junctions prevent movement the things between the cell.

All cells have a Na+/K+ pump, because of the potassium resting channels some K+ leaks out giving the PM a negatve charge on the inside of the cell.

These charges and ion concentration are continuous across of the epithelial cells due to the gap junctions

Move glucose from the gut into the cell.

Na+ can move glucose into the cell against its concentration gradient, high levels of glucose in the cell, facilitated transport is used on the basal side of the cell to move glucose and allow it to move down its concentration gradient.