The Cell Membrane

What is the cell membrane? AKA: Plasma membrane The boundary between the cell and the environment Does every cell have a cell membrane? – Yes, Each and every cell has a cell membrane.

How do cell membranes help to maintain homeostasis? The cell membrane allows nutrients to come into the cell Glucose, amino acids, lipids The cell membrane removes waste

Selective Permeability The cell membrane lets some molecules in and keeps others out EX. A cell is low on glucose so the membrane lets in some glucose, but does not overfill the cell with the monomer.

Structure of the cell membrane What does the cell membrane look like up close? Lets look at one of these structures up close

Structure of cell membrane Phospholipids – Phosphate head – Glycerol – 2 Fatty acid tails

Phospholipids 1.) Phosphate Head Polar Hydrophilic Make up the outer borders of the membrane 2.) Fatty Acid Tails Nonpolar Hydrophobic Make up the inner part of the membrane

Structure of cell membrane Phospholipid bilayer – 2 layers of phospholipids make up a cell membrane

Phospholipid Bilayer Remember polar heads and nonpolar tails

The fluid Mosaic Model of the cell membrane Lipid bilayer is not strong & firm like a hard shell, but it is fluid like a soap bubble consistency So, it is called the Fluid Mosaic Model (fluid like, with many proteins stuck in it)

The fluid Mosaic Model of the cell membrane It is a flexible membrane, made fluid because of cholesterol molecules located in the phospholipid bilayer. Proteins in the membrane move around.

Other components of the cell membrane Cholesterol – Helps to stabilize the phospholipids and keep them from sticking together

Other components of the cell membrane Carbohydrates- linked to lipids or proteins – Recognition of Cells – “Name tag of cell” – Ex. Is the cell a heart cell, liver cell, or brain cell? – Ex. Glycolipids & Glycoproteins (marker protein)

Other components of the cell membrane Proteins- make up 50 %- 70% of membrane – Regulate which molecules enter and which molecules leave a cell. – Receive info & ID the cell

Types of proteins in the cell membrane Carrier Protein – Allow needed substances or waste materials to move through the cell membrane

Types of proteins in the cell membrane Receptor Protein – These have binding sites for molecules such as hormones or substrates to bind to

Types of proteins in the cell membrane Channel or Pore protein – Hydrophilic channel – allows lipid insoluble substances to pass in and out of cell.

Types of proteins in the cell membrane Glycoproteins – Protein with what macromolecule attached to it? Carbohydrate – Functions for cell to cell recognition

Where are proteins located in the cell membrane? Integral Proteins – Proteins inside the cell membrane Peripheral Proteins – Proteins outside the cell membrane