Physiology Ex 1 - Ion Gradients and Transport

Question 2

How long do each of the 1 billion ATP molecules in the cell last?

Answer 2

less than one minute and 70% is used to pump Na+/K+

Question 3

What is ADP to ATP conversion used for?

Answer 3

Glycolysis

Oxidative metabolism

Question 4

What is ATP to ADP conversion used for?

Answer 4

Membrane transport

Anabolism

Catabolism

Mechanical work

Etc

Question 5

What is required for the efficient production of ATP by cells?

Answer 5

A hydrogen ion gradient across the mitochondrial inner membrane

Question 6

ATP synthase uses the energy of hydrogen ions diffusing down the gradient to produce?

Answer 6

ATP

Question 7

Electron Transport Chain proteins use energy derived from metabolism to?

Answer 7

Pump hydrogen ions across the inner mitochondrial membrane

Question 8

What does the metabolic poison 2,4-Dinitrophenol (DNP) do?

Answer 8

Uncouples oxidative phosphorylation (inhibits ATP production) by acting as a proton ionophore carrying protons across the mitochondrial membrane and decreasing the proton gradient.

Question 9

Why was DNP discontinued from use as a diet pill in the 1930’s?

Answer 9

Because of the risk of fatal hyperthermia and development of cataracts

Question 10

What does the metabolic poison Sodium Azide do?

Answer 10

Inhibits cytochrome oxidase by binding irreversibly to the heme cofactor (similar to cyanide poisoning). It affects organs that undergo high rates of repiration, such as the heart and brain. It inhibits growth of bacteria and fungi and is an airbag explosive.

Question 11

What types of transport down a concetration gradient do not require added energy?

Answer 11

Simple diffusion

Facilitated diffusion (vmax)

Question 12

What types of transport down a concetration gradient require added energy?

Answer 12

• Active transport - Na/K ATPase, Ca ATPase, P-glycoprotein
• Secondary active transport
• Endocytosis and Exocitosis

Question 13

Which types of molecules can diffuse across the membrane without a carrier?

Answer 13

Small lipid soluble molecules

Question 14

Which molecules require a carrier or channel to diffuse across the membrane?

Answer 14

Hydrophilic molecules

Question 15

Which are the membrane proteins that enable or facilitate passage of molecules across the membrane?

Answer 15

Channel proteins

Carrier proteins (passive, active)

Question 16

How does Vmad limit the rate of transport (or diffusion)

Answer 16

Facilitated diffusion is driven by the concentration gradient across the membrane but limited by the number and function of the transporters

Question 17

Does transporter-mediated diffusion require energy(net diffusion down a concentration gradient)?

Answer 17

No, however the rate of diffusion is NOT exclusively concentration-dependent unlike simple diffusion - the max rate of transport (Vmax) is related to the number of carrier molecules in the membrane and the speed with which the transporter protein can transport the molecule.

Question 18

What is the main use of facilitated diffusion?

Answer 18

To transport glucose and most amino acids into cells

Question 19

What is the specificity of the channel (channel proteins) determined by?

Answer 19

The size of the passageway and the charge of properties of the amino acids that make up the passageway

Question 20

What causes the net movement through a channel (channel proteins)?

Answer 20

An electrochemical gradient

Question 21

What are aquaporins?

Answer 21

Water channels

Question 22

Name some ion channels

Answer 22

K+

Na+

Ca++

Cl-

monovalent

divalent

etc

Question 23

Who discovered aquaporins?

Answer 23

Peter Agre (2003)

Question 24

Which channels are always open?

Answer 24

Pores

Leak channels

Question 25

Which channels are gated?

Answer 25

Gated channel

Question 26

What are the types of gated channels?

Answer 26

• Ligand-gated channel (triggered by binding of specific molecules to the channel)
• Phosphorylation-gated channels (function altered by phosphorylation/dephosphorylation)
• Voltage-gated channels (triggered by change in membrane potential)
• Mechanically-gated channels (triggered by mechanical stress to membrane)

Question 27

What type of gated channel are Nicotinic Cholinergic receptors?

Answer 27

Ligand-gated ion channels. 2 acetylcoline binding sites-binding of Ach opens the channel and allows Na+ ions to cross the membrane

Question 28

What are carrier proteins?

Answer 28

Membrane proteins that transport molecules in one or both directions

Question 29

Some molecules are transported by both carriers and channels. T/F?

Answer 29

True

Question 30

Oxygen enters cells by

Answer 30

Simple diffusion

Question 31

Sodium ions enter cells by

Answer 31

Primary active transport