B2.1- Membranes and Membrane Transport

Phospholipid Bilayer

Consists of two rows of phospholipids, with their tails facing inwards. These bilayers make up cell membranes

Phospholipids

A type of lipids with hydrophilic phosphate heads and two hydrophobic fatty acid tails

Polar

Describes molecules with positive and negative charged sections

Nonpolar

Describes molecules that are not charged

Hydrophobic

Describes molecules that are nonpolar, and are repelled by water

Hydrophilic

Describes molecules that are polar, and are attracted by water

Amphipathic

Describes molecules that have both hydrophobic and hydrophilic sections

Kinetic Theory

This theory states that particles are in constant random motion

Simple Diffusion

The passive transport of particles from a region of high concentration to a region of low concentration without using ATP or proteins

Facilitated Diffusion

The movement of particles from places of high concentration to areas of low concentration through channel proteins

Concentration Gradient

The difference in concentrations of a substance in two areas, such as inside and outside of a membrane

Osmosis

The passive transport of water from an area of low solute concentration to an area of high solute concentration through a semipermeable membrane

Passive Transport

The movement of particles across a membrane without using ATP

Integral Proteins

Proteins that are permanently attached to the plasma membrane, and penetrate into the center of the phospholipid bilayer

Transmembrane Proteins

Integral proteins that stretch across the entire phospholipid bilayer

Peripheral Proteins

Proteins that are temporarily attached to one side of the cell membrane

Channel Proteins

Proteins that span the length of the cell membrane, and have central pores which allow specific molecules to move in and out of the cell

Protein Pumps

A type of transmembrane protein that uses ATP to actively move a certain substance across the membrane

Aquaporins

Integral channel proteins that selectively transport water rapidly through membranes

Solution

Mixtures where one substance is completely dissolved in another

Solute

The substance being dissolved in a solution

Solvent

The substance doing the dissolving in a solution

Solute Concentration

The measure of how much solute is dissolved in a certain amount of solvent

Semipermeable Membrane

Barriers with pores that only let select particles through

Active Transport

The movement of particles against the concentration gradient using ATP

Adenosine Triphosphate (ATP)

A molecule that stores and transports energy to provide power for cells to function

Glycoproteins

Membrane proteins with a carbohydrate chain attached

Glycolipids

Phospholipids with a carbohydrate chain attached

Fluid Mosaic Model

This model depicts the cell membrane as a sea of phospholipids with embedded proteins and carbohydrates that constantly move through it