Fluid Mosaic Model a k a Phospholopid Bilayer

Fluid Mosaic Model a. k. a: Phospholopid Bilayer

Cellular membrane Overall functions - Boundary between intracellular compartments, living cells, and abiotic environment – Selectively permeable – – Some molecules cross membranes more easily than others.

Membrane Structure • Mostly made of phospholipids (review your notes on these) • Dual natured molecules: hydrophobic AND hydrophilic • Also has proteins throughout the membrane (see picture) • Membrane organization and properties referred to as a: FLUID MOSAIC MODEL

This bilayer has MANY components…. make sure you look at this and study the parts

Refer to previous illustration and plate 36 worksheet (test material) • Some proteins are only on the surface of the membrane • Attached to some of the surface proteins are carbohydrate groups that function as identification tags so cells recognize each other and do not attack each other. Find these on plate 36.

LE 7 -2 Organization of membrane phospholipids WATER Hydrophilic head Hydrophobic tail WATER

Fluid Mosaic Model • Called the F. M. M. because it is hypothesized that the membranes of a cell consist of phospholipid bilayers in which proteins and carbohydrates are also present • The term “mosaic” means made of small parts • Fluid because it is like a fluid so proteins are able to migrate throughout it

LE 7 -3 Mosaic: Proteins dispersed among phospholipids in membrane: Hydrophilic region of protein Phospholipid bilayer Hydrophobic region of protein

LE 7 -5 c Cholesterol within the animal cell membrane

Movement of membrane proteins Proteins and lipids Can drift within the bilayer • Picture the ball bin at Chuck. E Cheese. • You = proteins/lipids that move through the balls • The balls = phospholipid bilayer Proteins much larger than lipids so proteins move more slowly

Membrane Transport Proteins and their Functions • Some proteins have pores in them that allow facilitated diffusion of small polar molecules – This means small polar molecules can fit through the pores (like tunnels) and get to the other side of the membrane – Facilitate = to help – Diffusion = net movement across the membrane – Polar molecules are able to pass through the pores because the protein pores are also hydrophilic (polar) and allow them to pass

Diffusion (3 types to know about) • Simple Diffusion - gases, such as O 2 and CO 2, and small, uncharged polar molecules can cross the lipid bilayer membrane without the help of a protein • Facilitated diffusion-diffusion of polar and charged molecules, such as carbohydrates, amino acids, nucleosides, and ions, across the membrane to the other side (inside of cell). These molecules can cross the plasma membrane through USE OF A TRANSPORT PROTEIN (the proteins help, or “facilitate”) • Active Transport – REQUIRES ENERGY (ATP) because molecules are moved across the membrane against their gradient (this means molecules are going to the side of the membrane that already has more of those molecules)

Transport Proteins This slide illustrates the 3 types of diffusion. Please look carefully and make sure you know and understand the differences.

Refer to previous illustration and plate 36 worksheet (test material) • Some proteins are only on the surface of the membrane – Attached to some of the surface proteins are carbohydrate groups that function as identification tags so cells recognize each other and do not attack each other. Find these on plate 36. • Some proteins are embedded all the way through the membrane. – Remember, proteins are made of polar (hydrophilic) and non-polar (hydrophobic) amino acids. The hydrophobic part of the protein will be next to the hydrophobic portion of the membrane. Same goes for hydrophilic. (see plate 36 illustration/text) (test material!!)

LE 7 -7 Fibers of extracellular matrix (ECM) Glycoprotein Carbohydrate Glycolipid EXTRACELLULAR SIDE OF MEMBRANE Cholesterol Microfilaments of cytoskeleton Peripheral proteins Integral protein CYTOPLASMIC SIDE OF MEMBRANE