Ingenuity Honor’s Biology November 27th, Tuesday Baltimore Polytechnic Institute Ingenuity Honor’s Biology November 27th, Tuesday Unit 3: Cell membrane Insong James Lee, Ph.D.

Unit 3: cell membrane November 27th, Tuesday Learning objectives: What are the three macromolecule components of the cell membrane and what are their functions? Describe the lipid bilayer structure of the cell membrane. Explain what the fluid mosaic model is. Discuss selective permeability of cell membranes. Unit 3: cell membrane

Cell membrane Topic slides Brief review of macromolecules 4 (relevant to cell membrane). 2. Cell membrane overview. 5-6 3. Phospholipids. 7-12 Semi-permeability of cell membranes. 13-14 Fluid mosaic model of membrane 15-17 Phospholipid differences in different 18-23 Organisms

Complete chart labeled “Do Now” on notes handout. TASK: Glycerol is a straight-chain carbohydrate with the formula C3H8O3. Draw its structure. Complete chart labeled “Do Now” on notes handout.

Overview of cell membrane slide 6

The Cell Membrane (aka Plasma Membrane) Every cell has a membrane around it Provides a boundary to the cell system It selectively brings nutrients in and wastes out Membranes are made of 3 types of molecules LIPIDS Proteins Carbohydrates

Phospholipids slides 8-12

Membrane Lipid = Phospholipid YOU REMEMBER THE PHOSPHOLIPID RIGHT? Polar Head Two Nonpolar Tails

Let’s take another look: HYDROPHILIC – loves water HYDROPHOBIC – fears water

Water, Water Everywhere… Ok, so we know that the cell membrane is made mainly of these phospholipids We also know that there is water outside and inside of a cell Question: How do the phospholipids arrange to create protective barrier for the cell?

A Bilayer!!!! HYDROPHILIC HYDROPHOBIC HYDROPHILIC Phospholipid Bilayer – two rows of phospholipids that surround every cell.

Put It All Together Remember: The membrane is made of 3 major molecules, not only LIPIDS!

Semipermeability of cell membranes slide 14

Semipermeability of cell membrane The purpose of the external membrane of the cell is to allow only certain molecules to enter, while allowing wastes to exit: Small non-polar molecules are the most likely to cross the membrane while large, polar molecules are the least likely.

Fluid mosaic model slides 16-17

“Fluid Mosaic” Model

Differences in cell membrane in organisms slides 19-23

Remember the three domains of life? Bacteria and Archaea are domains of unicellular prokaryotes. What’s so different about them anyway?

Ester and ethers An ester is an organic compound where the hydrogen in the compound's carboxyl group is replaced with a hydrocarbon group. Esters are derived from carboxylic acids and (usually) an alcohol. While carboxylic acid has the -COOH group, the hydrogen is replaced by a hydrocarbon in an ester. The chemical formula of an ester takes the form RCO2R′, where R is the hydrocarbon parts of the carboxylic acid and R′ is the alcohol. An ether is an organic compound that contains two alkyl or aryl groups by an oxygen atom. The general formula for an ether is R-O-R'.

One difference is the membrane lipids! Unlike other organisms, archean cells use ether linked (-OH : -OH) lipids in their membranes. Also, the “tails” are funky. Take home: archea have weird membrane lipids

The wonderful world of lipid chemistry

The Basics are as easy as 1. hydrophilic heads 2. hydrophobic tails 3 The Basics are as easy as 1. hydrophilic heads 2. hydrophobic tails 3. phospholipid bilayer!

Wrap Up Cell membrane structure: phospholipid bilayer Cell membrane function: selective permeability controls what enters / exits cell Time for a video? Inner Life of A Cell Harvard U BioVisions computer modeling lab.