Cell Membrane Structure

Proteins and Membranes  Two main types of proteins are embedded in the cell membrane: INTEGRAL PROTEINS - penetrate the membrane - transport specific molecules across the cell membrane   PERIPHERAL PROTEINS - not embedded in the lipid bilayer - are attached to the surface of lipids or exposed part of integral proteins -gives the cell support

Other Parts of the Structure Glycoprotein Sugar and protein Gives unique identification of the cell Acts as a receptor for hormones and neurotransmitters Helps stabilize membrane structure (with Glycolipids) Glycolipid Sugar and fat Act as surface receptors (like glycoproteins) Stabilize membrane structure

Glycoprotein and Glycolipid

Other Parts of the Structure Cholesterol Helps to stabilize the phospholipids by preventing their fatty acid tails from sticking together Makes membrane less permeable Makes cell membrane fluid in low temperatures Makes cell membrane rigid in high temperatures Helps regulate membrane fluidity Important for membrane stability Carbohydrates On external surface of cell membrane Used to identify cells of similarity

Cholesterol and Carbohydrates

How does the Cell Membrane Maintain Homeostasis? Selective Permeability! This is when a membrane allows some molecules to pass through while keeping others out. (e.g. Screen Window – Air in, bugs out) The hydrophobic core of the membrane prevents the transport of ions and polar molecules that are hydrophilic (water loving)

How Does the Cell Membrane Maintain Homeostasis? The membrane is permeable to small molecules such as water, oxygen, and hydrocarbons   The membrane is impermeable to larger molecules such as glucose, and ions such as calcium ions or sodium ions – these must be allowed into the cell only at certain times, in certain amounts, and through certain channels.

Cell Membrane Coloring