W12 L1 - Membrane Proteins and Transport Flashcards

Flashcards about membrane proteins and transport.

What is the role of membranes?

Form a barrier preventing the passage of molecules from one side to the other and create compartments for biochemistry.

Why do polar compounds need specific transporters?

Specific transporters are needed to get polar compounds across membranes.

What must a hydrated compound do to dissolve in the hydrophobic core of a membrane?

The compound needs to shed its hydrated shell, go into the membrane, and then come out the other side, and then it will rehydrate.

What causes the difficulty for a polar compound to dissolve into the hydrophobic core of a membrane?

A high activation energy barrier.

How does a transporter reduce the activation energy barrier for polar compounds?

A transporter carries the hydration shell through a central pore, so the compound doesn't have to desolvate.

What is the relationship between the activation energy barrier and the rate of reaction?

The activation energy barrier is proportional to the rate of reaction.

What are the two large families of membrane proteins that facilitate solute transfer?

Channels or transporters (passive) and active transporters or pumps.

What are channels?

Passive transporters that don't need energy and have fast transport.

What is another way to describe channels?

Facilitated diffusion.

What are pumps?

Active transporters that need energy and are slower.

What is something active transporters can do?

They can push compounds against their chemical gradient.

What is passive transport?

A non-energy requiring mechanism to move from high to low concentration until equilibrium is reached.

What happens at equilibrium in passive transport?

The rate of transport from one side of the membrane to the other is equal.

What two things need be to balanced to achieve equilibrium?

The chemical differences and the electrical gradients.

What is the GLUT one transporter an example of?

Glucose transport across the membrane.

How does glucose enter the cell via the GLUT one transporter?

It goes into the binding pocket, the enzyme switches conformation, and then the glucose goes to the inside of the cell.

What happens when glucose transporters go wrong?

Diabetes.

How does insulin affect glucose uptake?

Insulin interacts with a receptor, causing vesicles with glucose transporters to fuse with the external membrane.

What happens in patients with diabetes that prevents grabing glucose from the bloodstream?

They don't produce enough insulin.

What is cystic fibrosis?

A disease associated with a pump that pumps chloride ions, making mucus less viscous.

What causes cystic fibrosis?

Missing the chloride ion channel due to a point mutation.

What are the different kinds of transporters?

Uniporters, symporters, and antiporters.

What does a uniporter do?

It simply takes a compound, brings it across the membrane, and drops it off.

What does a symporter do?

It takes two compounds from the extracellular space and brings them in together.

What does an antiporter do?

It brings one compound into the cell and pumps another out.

What do direct active transporters use to pump a substrate against its chemical gradient?

Direct active transporters require energy in the form of ATP or sunlight.

In oxidative phosphorylation, what are the electrons used for?

Electrons are used to pump protons into the intermembrane space, creating a proton gradient.

What does the F1FO ATPase do?

It dissipates energy from the gradient, working as a rotary motor to generate ATP.

What are ABC transporters?

ATP binding cassettes; they bind to nucleotides and use that energy to power transport against a chemical gradient.

How do secondary transporters work?

They utilize already established gradients to antiport or symport compounds through the membrane.