Cells - Membrane Transport

What is the primary function of the cell membrane?

To create a barrier that allows the cell to control what enters and exits.

What term describes the permeability of the cell membrane?

Selectively permeable.

What are the main components of the cell membrane?

Lipids (phospholipids and cholesterol), proteins (integral and peripheral), and carbohydrates (glycolipids and glycoproteins).

What are the properties of phospholipids?

They have amphipathic properties with hydrophilic phosphate heads and hydrophobic fatty acid tails.

How do phospholipids arrange themselves in a bilayer?

The tails face inward towards each other, while the heads face outward towards the extracellular and intracellular fluids.

What role does cholesterol play in the cell membrane?

It maintains membrane fluidity by embedding itself between phospholipid tails.

What are integral membrane proteins?

Proteins that extend partially or completely through the membrane, often involved in transport.

What are peripheral membrane proteins?

Proteins that associate with the surface of the membrane, usually hydrophilic and may bond covalently to membrane components.

What are glycoproteins and glycolipids used for?

They are involved in cell recognition and chemical signaling.

What does the fluid mosaic model describe?

The structure of the cell membrane, highlighting its fluidity and the diverse components that make it appear mosaic-like.

What is the difference between semi-permeable and selectively permeable?

Semi-permeable allows all solvents and some small solutes to pass, while selectively permeable allows variable permeability to specific solutes.

What is passive transport?

The movement of particles from high to low concentration without using energy.

What are the types of passive transport?

Simple diffusion, facilitated diffusion, and osmosis.

What is simple diffusion?

The movement of particles directly through the phospholipid bilayer along their concentration gradient.

What is facilitated diffusion?

The movement of particles that cannot pass directly through the bilayer, using channel proteins.

What is osmosis?

The movement of water across the membrane, often through aquaporins.

What is active transport?

The movement of particles against their concentration gradient, requiring ATP energy.

What is an example of active transport?

The sodium-potassium pump, which moves sodium out and potassium into the cell.

What is the role of protein pumps in active transport?

They move specific particles in one direction and change conformation during the process.

What is the significance of aquaporins?

They facilitate the rapid movement of water across cell membranes, especially in cells that require high water transport.

What happens to membrane fluidity when cholesterol is present?

Cholesterol helps maintain fluidity by preventing the fatty acid tails from packing too closely together.

How do membrane proteins vary?

Different membranes can have different proteins, and the position and structure of a protein depend on its function.