1. 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?

2. Section 3-3 “Cell Membrane”

3. 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.

4. 3.3 KEY CONCEPT: The cell membrane is a barrier that separates a cell from the external environment.

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

6. 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

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

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

10. 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”

13. 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

15. 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

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

17. 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

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

19. The cell membrane is selectively permeable (only certain things get through) like a screen door

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

21. 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

22. • 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

23. • 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.

24. 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