Lecture 11: Active vs. Passive Transport

Passive transport

Ions move with their electrochemical gradients (no energy needed)

* pushing a boulder down a hill

Do ion channels use active or passive transport?

passive transport

Active Transport

Ions move against their electrochemical gradients (must spend energy)

* pushing a boulder up a hill

Do pumps and ion exchangers use active or passive transport?

active transport

What is permeability and how is it controlled?

How easy it is for ions to move across the membrane and it is controlled by passive transport through ion achannels

T/F: Active transport is always working

True

What form of energy do ion pumps use?

Adenosine Triphosphate (ATP)

Adenosine Triphosphate (ATP)

* Nucleotide with a large amount of chemical energy stored in its high- energy phosphate bonds
* Releases energy when broken down into ADP
* Energy used for many biological processes
* Considered the universal energy currency for metabolism

How many phosphates does ATP have?

three phosphates

(cram extra phosphate in to the adenosine and put it into a super high energy state)

What do Na+ and K+ ion pumps do?

Moves Na+ and K+ against their concentration gradients by forming complexes with them

What type and how much of that energy is required for Na+ and K+ ion pumps?

Requires lots of energy in the form of ATP

Whats a good analogy between ATP and ADP?

ATP is money in the bank and ADP is money spent

How do sodium and potassium pumps work?

1. Sodium Binding (three binding pumps)
2. When they bind, ATP spends energy or sticks a phosphate on protein (change the shape of the protein so that it does something different)
3. Pump goes from pointing inside the cell to pointing out of the cell and thus releases sodium to the outside of the cell
4. This allows potassium from the outside of the cell to bind with the cell and the phosphate is released
5. the channel flips back to pointing towards the inside of the cell because the phosphate is released and the potassium is released inside the cell

What does binding a phosphate from ATP to a protein do?

It changes the shape of the protein

Why do sodium and potassium pumps require active transports?

Because sodium doesn’t want to leave the inside of the cell and potassium doesn’t want to come inside the cell

Ion Exchangers

Don’t use energy from ATP, but fro the electrochemical gradient of sodium

What happens while Na+ moves down its concentration gradient (inside the cell)?

causes changes in ion exchanger protein conformation (shape) that move another ion species out

What are the two main things that we don’t want to be in the cell and are filtered out through ion channels?

calcium and protons (H+)

How do ion exchangers use the electrochemical gradient of sodium?

If they let sodium into the inside of the cell, it will push out the positive ions of calcium and protons which is what we want