AP BIO Chapter 7 - Membrane Structure and Function

Cell Membrane

the boundary separating a cell from it’s environment

Cell Membrane Structure

made of phospholipid bilayer (phosphate head on outside, fatty tails on inside)

What molecules can get through the cell membrane directly?

fats and other lipids can slip directly through the phospholipid cell membrane

peripheral proteins

loosely bound to surface of membrane

integral proteins/transmembrane proteins

penetrate into lipid bilayer, often completely spanning the membrane

Channel Proteins

wide open passage

Ion Channels

gated (opening and closing the space)

Aquaporins

water only, kidney and plant root only

Carrier Proteins

change shape

Transport Proteins

require ATP

Recognition Proteins

glycoproteins

Adhesion Proteins

anchors

Receptor Proteins

hormones

Membrane Carbohydrates

Play a key role in cell-cell recognition and are the basis for rejection of foreign cells by immune system

Cholesterol

Provides stability in animal cells

Sterol

cholesterol but for plants

Passive Transport

molecule movement that does not require energy and that moves down concentration gradient

Active Transport

molecule movement that does requires ATP and that moves against concentration gradient

2nd Law of Thermodynamics

Universe tends towards disorder

Diffusion

movement from high → low concentration

Diffusion of 2 solutes

Each substance diffuses down its own concentration gradient, independent of concentration gradients of other substances (each substance does their own movement to balance regardless of others)

Osmosis

Movement of water across the cell membrane; the diffusion of water from high concentration of water to low concentration of water

direction of osmosis

determined by comparing total solute concentrations

Hypertonic

more solute, less water

Hypotonic

less solute, more water

Isotonic

equal solute, equal water