Warm-Up Where does protein synthesis begin? INSTRUCTIONS: Answer the following questions on a piece of lined paper, using complete sentences. Where does protein synthesis begin? What is the function of the endoplasmic reticulum and Golgi apparatus? What role do ribosomes play in protein synthesis? What role does a vesicle play in protein synthesis?

Section 3-3 “Cell Membrane”

Describe the structure of the cell membrane Today’s Objectives Describe the structure of the cell membrane Summarize how chemical signals are transmitted across the cell membrane.

3.3 KEY CONCEPT: The cell membrane is a barrier that separates a cell from the external environment.

The Cell membrane functions: forms a boundary between inside and outside of the cell controls passage of materials cell membrane outside cell inside cell

List 2 functions of the cell membrane 1. forms a boundary between inside and outside of the cell 2. controls passage of materials cell membrane outside cell inside cell 7

The cell membrane is made of a phospholipid bilayer. protein cholesterol carbohydrate chain protein channel The cell membrane is made of a phospholipid bilayer. 8

Charged phosphate group, glycerol and two fatty acid chains Phospholipid bilayer. Forms a double layer surrounding the cell Composed of : Charged phosphate group, glycerol and two fatty acid chains 9

Polar and Nonpolar Heads are Polar HYDROPHILIC “Water loving” Polar : Tendency of a molecule, or compound, to be attracted or repelled by electrical charges because of an “Charged” arrangement of atoms Nonpolar – having “no charge” or evenly spread charge Tails are Nonpolar HYDROPHOBIC “Water fearing”

The cell membrane is made of a phospholipid bilayer. There are other molecules embedded in the membrane. The fluid mosaic model describes the membrane. cell membrane protein cholesterol carbohydrate chain protein channel

It has two characteristics The fluid mosaic model describes the membrane. It has two characteristics 1. the cell membrane is flexible not rigid moves like a fluid 2. there is a variety of molecules studding the membrane like tiles in a mosaic http://www.youtube.com/watch?v=ULR79TiUj80&feature=related

Cholesterol – strengthens membrane Other Molecules cell membrane protein cholesterol carbohydrate chain protein channel Cholesterol – strengthens membrane

Other Molecules cell membrane protein cholesterol carbohydrate chain protein channel Proteins- aid in cell identification and movement of molecules across the membrane and cell signaling

Carbohydrates – aid in cell identification Other Molecules cell membrane protein cholesterol carbohydrate chain protein channel Carbohydrates – aid in cell identification

The cell membrane is selectively permeable (only certain things get through) like a screen door http://www.youtube.com/watch?v=JShwXBWGMyY&feature=related

Selective permeability: it allows some but not all materials to cross. Allows cell to maintain homeostasis Variety of ways molecules can cross membrane

Receptor: detects a signal molecule(ligand) and performs an action in response. Signalling molecules (blue spheres) bind the cell surface receptors (pink tube) and induce a conformational change (represented by the shortening of the tubes in the right image compared to the left). These changes in the cytoplasmic domain (lower part of images) can then activate other proteins

• Intracellular: a receptor that is located inside a cell • Intracellular: a receptor that is located inside a cell. They bind to molecules that can cross the membrane

• Membrane: A receptor that is located in the membrane; binds to molecules that cannot cross the membrane, change in shape transmits the message to the cell interior.

Time to answer the objectives from 3-3 1. Describe the structure of the cell membrane Composed of 2 phospholipid layers with proteins stuck in it 2. Summarize how chemical signals are transmitted across the cell membrane Receptors on the cell membrane recognizes and binds to only certain molecules Carbon, Oxygen, Nitrogen, & Hydrogen make up 96 % of human body mass