1. The Cell Membrane
Biology Honors

2. Main Functions Regulates materials moving in and out of the cell.
Provides a large surface area on which specific chemical reactions can occur.
Site for receptors containing specific cell identification markers that differentiate one cell from another.
Separates cells from one another.
Protects the inside of the cell.
The main goal is to maintain homeostasis.
The membrane doesn’t completely protect the cell because many substances that aren’t beneficial to the cell, can still enter through diffusion.
Membranes allow cells to create and maintain internal environments that differ from external environments.

3. Selectively Permeable
Some materials can pass through and others cannot.
Permeability depends on:
1. Lipid solubility
2. Size
3. Charge (ions)
4. Presence of channels and transporters
Think of it like a strainer

4. Fluid Mosaic Model
A membrane that is a fluid (can move easily) structure, with a “mosaic” of various proteins and carbohydrates embedded in it.

6. General Structure
Phospholipids are made up of a hydrophilic phosphate and glycerol head and a hydrophobic fatty-acid tail
The head makes up the outside of the lipid bilayer and the hydrophobic tails make up the inside.
Proteins that extend through the entire membrane are called amphipathic, they have both hydrophilic and hydrophobic regions.
Along the membrane, many proteins and lipids are attached to carbohydrates. Together they function in cell recognition and communication.

7. Coloring Instructions
Hydrophilic heads yellow.
Hydrophobic fatty acid tails green.
Carbohydrate chains red.
Outline the glycolipid in light blue.
Outline the glycoprotein in pink.
All membrane proteins orange.
Peripheral proteins purple.
Cholesterols dark blue.
Transport protein yellow.
Receptor & enzymatic (ATP synthase) proteins pink.
Attachment / Recognition dark green.

8. 1) Phospholipid- label the structures on your foldable!
Made up of polar phosphate and glycerol heads, and nonpolar fatty acid tails.

9. 2) Phospholipid Bilayer
Allows some substances to diffuse through, such as small and nonpolar (O2) or small and polar (H2O). Substances can’t pass the membrane if they are charged ions or large (sodium ions and glucose).

10. 3) Integral Protein
A protein partially or fully embedded in the membrane.
Serve as transport channels for particles to enter and leave the cell.
Some can move around the membrane.

11. 4) Peripheral Protein
Proteins loosely bound on the surface of the membrane or to an integral protein
May help regulate cell signaling.

12. 5) Cholesterol
Secure proteins in the membrane, prevents the cell from becoming too fluid, and gives cells the ability to communicate with each other.
Holds the bilayer together.

13. 6) Glycolipid Carbohydrate bonded to a lipid.
Function as identification markers for cell recognition, and may provide energy.

14. 7)Oligosaccharide / Carbohydrate Chain
ID tags that allow cells to distinguish one cell from another.

15. 8) Glycoprotein Carbohydrates bound to proteins on the membrane.
Brings other cells together; act as receptors on cell surfaces, and offers strength and support.

16. 9. Transport Protein
Help substances that can’t cross the bilayer. They can’t cross because they are charged (ion), too large (glucose), or both (amino acids).

17. 10. Attachment and Recognition
Attachment sites for different elements on either side of the membrane.
Intracellular & Extracellular

18. Receptor for Signaling / Receptor Proteins
Proteins that bind to hormones or growth factors. When bound they can trigger a signal that begins a cascade of reactions.

19. Hey, it ends in “ase” what am I?
Enzymatic Activity
Some proteins are involved in catalyzing biochemical reactions.
Example: ATP Synthase in the inner membrane of the mitochondria.
Hey, it ends in “ase” what am I?