Yilan

Zhao Yilan Chapter 8 Section 1&2 Period 3 10/21/2011

Section 1

Key terms

Phospholipid:(FAHS foh LIP id)a lipid that contains phosphorus and that is structural component in cell membranes.

Lipid bilayer:(LIP id BIE uhr)the basic structure of a biological mambrane,composed of two layers of phospholipids.

Key ideas

One way that a cell maintains homeostasis is by controlling the movement of substances across the cell membrane.

The phospholipids form a barrier through which only small,nonpolar substances can pass.

Cell-surface markers/Receptor proteins/Enzymes.Transport proteins.

Critical thinking

Individual cells,as well as organisms,must maintain homeostasis in order to live.If the cell membrane were fully permeable to all substances,the organism would die.

Section 2

Key term

Equilibrium:a state that exists when the concentration of a substance is the same throughout a space.

Concentration gtadient:a different in the concentration of a substance across a distance.

Diffusion:the movement of particals from regions of higher density to regions of lower density.

Carrier protein:a protein that transports substances across a cell membrane.

Osmosis;the diffusion of water or another solvent from a more dilute solution(of a solute)to a more dilute solution(of a solute)through a membrane that is permeable to the solvent.

Sodium-potassium pump:a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassion ions into the cell.

Key ideas

Ions,sugars,and amino acids can diffuse through the cell membrane through channel proteins.These proteins,sometimes called pores,serve as tunnels through the lipid bilayer.Each channel allows the diffusion of specific substances that have right size and charge.Carrier proteins transport substances that fit within their binding site.A carrier protein binds to a specific substance on one side of the cell membrane.This binding causes the protein to change shape.As the protein's shape...