The building blocks of life Cells Chapter 3 Cell Organelles (Plasma Membrane (Phospholipid) Slide 46-67 The building blocks of life

Biology, 9th ed,Sylvia Mader Chapter 04 Plasma Membrane Cell Structure and Function Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. protein molecules phospholipid bilayer

Cell/Plasma Membrane http://vdinh.weebly.com/uploads/1/3/5/5/13557835/6310308_orig.jpg Surrounds all types of cells. Prokaryote & Eukaryotes In a plant cell, it lies beneath the cell wall In animal cells, it is the outer boundary (made of cholesterol) Provides cell with Protection and supports the cell Control of movement of materials in/out of cell Maintains condition of cell

Cytoplasmic Membrane Surrounds the cell and decides what comes in and out Semi-permeable: allows nutrients in and waste products out Made of a phospholipid bilayer Also called Plasma Membrane

Cytoplasmic Membrane Factory Part: Found in: Gates or Doors Plant cells Animal cells Prokaryotic cells

Cell membrane Encloses the cell contents, security gate phospholipid bilayer with embedded proteins Phospholipid bilayer Membrane proteins

Cytoplasmic Membrane The cytoplasmic/plasma/cell membrane In eukaryotic cells, as in prokaryotes Fluid phospholipid bilayer embedded with proteins and glycoproteins. Phospholipid bilayer is arranged so that the polar ends of the molecules (the phosphate and glycerol portion of the phospholipid that is soluble in water) form the outermost and innermost surface of the membrane while the non-polar ends (the fatty acid portions of the phospholipids that are insoluble in water) form the center of the membrane

Cytoplasmic Membrane The cytoplasmic/plasma/cell membrane Contains glycolipids as well as complex lipids called sterols Cholesterol molecules found in animal cell membranes not found in prokaryotic membranes(except for some mycoplasmas Sterols make the membrane less permeable to most biological molecules Help to stabilize the membrane Probably add rigidity to the membranes aiding in the ability of eukaryotic cells lacking a cell wall to resist osmotic lysis. Proteins and glycoproteins in the cytoplasmic membrane are quite diverse and function as: a. channel proteins to form pores for the free transport of small molecules and ions across the membrane b. carrier proteins for facilitated diffusion and active transport of molecules and ions across the membrane c. cell recognition proteins that identifies a particular cell d. receptor proteins that bind specific molecules such as hormones and cytokines e. enzymatic proteins that catalyze specific chemical reactions.

Cellular membranes are fluid mosaics of lipids and proteins Phospholipids are the most abundant lipid in the plasma membrane Phospholipids are amphipathic molecules, containing hydrophobic and hydrophilic regions (having two different affinities, as a polar end that is attracted to water and a nonpolar end that is repelled by it.) The fluid mosaic model states that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it For the Cell Biology Video Structure of the Cell Membrane, go to Animation and Video Files.

Plasma Membrane Contains cell contents Double layer of phospholipids & proteins

Phospholipids Polar Interacts with water Hydrophylic head Hydrophobic tail Interacts with water

AP1: BIOCHEMISTRY: PHOSPHOLIPIDS https://www.youtube.com/watch?v=sHN7e52Gh4U

BCLN - Phospholipids - Biology https://www.youtube.com/watch?v=SH_LgL12k1g

Cell/Plasma Membrane http://legacy.hopkinsville.kctcs.edu/instructors/Jason-Arnold/VLI/Module%202/m2cellstructure/f4-05_a_model_of_the_pl_c.jpg

The Plasma Membrane In animal cells, the plasma membrane has four principal components: 1. A phospholipid bilayer. Molecules of cholesterol interspersed within the bilayer. Proteins that are embedded in or that lie on the bilayer. Short carbohydrate chains on the cell surface, collectively called the glycocalyx, that function in cell adhesion and as binding sites on proteins.

The Plasma Membrane Figure 5.1 phospholipids cholesterol proteins glycocalyx cell exterior cell interior cytoskeleton peripheral protein integral protein Phospholipid bilayer: a double layer of phospholipid molecules whose hydrophilic “heads” face outward, and whose hydrophobic “tails” point inward, toward each other. Cholesterol molecules that act as a patching substance and that help the cell maintain an optimal level of fluidity. Proteins, which are integral, meaning bound to the hydrophobic interior of the membrane, or peripheral, meaning not bound in this way. Glycocalyx: sugar chains that attach to proteins and phospholipids, serving as protein binding sites and as cell lubrication and adhesion molecules. Figure 5.1

The Phospholipid Bilayer Phospholipids are molecules composed of two fatty acid chains linked to a charged phosphate group. The fatty acid chains are hydrophobic, meaning they avoid water, while the phosphate group is hydrophilic, meaning it readily bonds with water.

The Phospholipid Bilayer Such phospholipids arrange themselves into bilayers—two layers of phospholipids in which the fatty acid “tails” of each layer point inward (avoiding water), while the phosphate “heads” point outward (bonding with it).

The Phospholipid Bilayer Phospholipids take on this configuration in the plasma membrane because a watery environment lies on either side of the membrane.

The Phospholipid Bilayer As temperatures cool, membranes switch from a fluid state to a solid state The temperature at which a membrane solidifies depends on the types of lipids Membranes rich in unsaturated fatty acids are more fluid than those rich in saturated fatty acids Membranes must be fluid to work properly; they are usually about as fluid as salad oil The steroid cholesterol has different effects on membrane fluidity at different temperatures At warm temperatures (such as 37°C), cholesterol restrains movement of phospholipids At cool temperatures, it maintains fluidity by preventing tight packing

Unsaturated hydrocarbon tails Saturated hydrocarbon tails Figure 7.8 Fluid Viscous Figure 7.8 Factors that affect membrane fluidity. Unsaturated hydrocarbon tails Saturated hydrocarbon tails (a) Unsaturated versus saturated hydrocarbon tails (b) Cholesterol within the animal cell membrane Cholesterol 21

Cell membranes are made of PHOSPHOLIPIDs HYDROPHILIC heads (water liking) -Attracted to the water called POLAR HYDROPHOBIC tails (water fearing) -Not attracted to the water called NON-POLAR A Phospholipid