Module 2: How Things Work

These flashcards cover key concepts related to membrane structure, fluidity, transport mechanisms, and the role of proteins and ions in cells.

What is the fluid mosaic model of membrane structure?

It describes the membrane as a mosaic of various components, including lipids and proteins, that are fluid and can move laterally.

How does temperature affect membrane fluidity?

Changes in temperature can alter the saturation of fatty acid tails, affecting membrane fluidity; unsaturated tails maintain fluidity at lower temperatures.

What are two ways water can cross a membrane?

Water can cross either through simple diffusion across phospholipids or facilitated diffusion through aquaporins.

What is osmosis?

Osmosis is the diffusion of water across a selectively permeable membrane.

What is simple diffusion?

The net movement of particles from an area of higher concentration to an area of lower concentration without the aid of transport proteins.

What is the difference between facilitated diffusion and active transport?

Facilitated diffusion occurs along the gradient without energy use, while active transport moves substances against their gradient using energy.

What is a sodium-potassium pump?

A transport protein that moves sodium ions out of and potassium ions into the cell, using ATP for energy.

What role do aquaporins play in membrane transport?

Aquaporins are passive channels that facilitate the rapid movement of water across the membrane.

What happens to sodium ions if there are sodium ion channels in a membrane with a 0.5M Na+ solution on side A and 0.2M on side B?

There would be a net movement of sodium ions from side A to side B.

How does the movement of ions generate electrochemical gradients?

Transport of ions across membranes creates differences in ion concentrations and charges, leading to a voltage across the membrane.

What is the function of membrane proteins?

Functions include transport, enzymatic activity, signal transduction, cell-cell recognition, and attachment.

What molecules can diffuse directly through a phospholipid bilayer?

Small nonpolar molecules, such as oxygen and carbon dioxide, can diffuse directly through a phospholipid bilayer.

What does the term 'solute' refer to?

A solute is a substance that is dissolved in a solution.

What is the role of cholesterol in membrane fluidity?

Cholesterol helps maintain membrane fluidity by preventing tight packing of phospholipids at low temperatures and stabilizing membranes at high temperatures.

What is dynamic equilibrium in diffusion?

Dynamic equilibrium occurs when molecules continue to move but there is no net change in concentration on either side of the membrane.

What are channel proteins?

Channel proteins are membrane proteins that form pores through which specific ions or molecules can passively move across the membrane.

What determines the direction of water movement across a semi-permeable membrane?

The net direction of water movement is determined by the concentration of solutes on either side of the membrane.