Unit 2: Cells, Membranes and Signaling CELL MEMBRANE. Chapter 5 Hillis Textbook

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1 Unit 2: Cells, Membranes and Signaling CELL MEMBRANE Chapter 5 Hillis Textbook

2 HOW DOES THE LAB RELATE TO THE NEXT CHAPTER? SURFACE AREA: the entire outer covering of a cell that enables materials pass. VOLUME: the inside spare that can be filled with organelles/etc. CELLS WITH MORE SURFACE AREA AND LESS VOLUME WILL BE VERY EFFICIENT!!! You looked at the rate of diffusion Which cell could diffuse materials quicker and more efficiently?

3 HOW DO MOLECULES GET IN AND OUT OF THE CELL? MANY different molecules nee to get into the cells For example, after we eat BIOMOLECULES are broken into monomers and absorbed by the small intestines, into the blood and traveled all around the body to the CELLS! Biomolecules must get into the cells for the cells to use them Ex: Mitochondria need glucose, ribosomes need amino acids CELL MEMBRANE needs lipids, carbs and proteins These molecules get in and out of the cell by the CELL MEMBRANE!

4 PART ONE: PROPERTIES OF THE CELL MEMBRANE PHOSOPHOLIPID BILAYER A membrane s structure and functions are determined by its constituents: lipids, proteins, and carbohydrates. The general structure of membranes is known as the fluid mosaic model. Phospholipids form a bilayer which is like a lake in which a variety of proteins float.

5 LIPIDS Lipids form the hydrophobic core of the membrane. Most lipid molecules are phospholipids with two regions: Hydrophilic regions electrically charged heads that associate with water molecules Hydrophobic regions nonpolar fatty acid tails that do not dissolve in water

6 BILAYER: A bilayer is formed when the fatty acid tails associate with each other and the polar heads face the aqueous environment (Water). Bilayer organization helps membranes fuse during vesicle formation and phagocytosis.

7 FLUID MOSAIC: Membranes are fluid due to the flexible composition and mosaic due to the patterns that form from lipids and proteins Two important factors in membrane fluidity: Lipid composition types of fatty acids can increase or decrease fluidity Temperature membrane fluidity decreases in colder conditions Proteins are randomly scattered within the cell membrane to form a mosaic pattern

8 PROTEINS: Biological membranes contain proteins, with varying ratios of phospholipids. Peripheral membrane proteins lack hydrophobic groups and are not embedded in the bilayer. Integral membrane proteins are partly embedded in the phospholipid bilayer. Anchored membrane proteins have lipid components that anchor them in the bilayer. Proteins are asymmetrically distributed on the inner and outer membrane surfaces. A transmembrane protein extends through the bilayer on both sides, and may have different functions in its external and transmembrane domains. Some membrane proteins can move within the phosopholipid bilayer, while others are restricted. Proteins inside the cell can restrict movement of membrane proteins, as can attachments to the cytoskeleton.

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10 CARBOHYDRATES: Plasma membrane carbohydrates are located on the outer membrane and can serve as recognition sites. Glycolipid a carbohydrate bonded to a lipid Glycoprotein a carbohydrate bonded to a protein

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12 Active transport requires input of metabolic energy. SELECTIVELY PERMEABLE (SEMI-PERMEABLE): Biological membranes allow some substances, and not others, to pass. This is known as selective permeability. Two processes of transport: Passive transport does not require metabolic energy.

13 Building a Plasma Membrane Build a cell membrane from the pieces you received. Cut and paste them into the design you believe the plasma (cell) membrane would have. Label the following and check them off as you go: Intracellular polar heads cholesterol Extracellular non-polar tails saturated lipid Aqueous environment peripheral protein unsaturated lipid Phospholipid integral protein channel protein Hydrophilic region transmembrane protein Phosphate heads glycolipid Hydrophobic region glycoprotein Fatty acid tails carbohydrate (polysaccharide) Define the following terms somewhere on your page: Fluid Mosaic Model Phospholipid bilayer Selectively (semi) permeable membrane Cellular transport

14 Building a Plasma Membrane Build a cell membrane from the pieces you received. Cut and paste them into the design you believe the plasma (cell) membrane would have. Label the following and check them off as you go: Intracellular polar heads cholesterol Extracellular non-polar tails saturated lipid Aqueous environment peripheral protein unsaturated lipid Phospholipid integral protein channel protein Hydrophilic region transmembrane protein Phosphate heads glycolipid Hydrophobic region glycoprotein Fatty acid tails carbohydrate (polysaccharide) Define the following terms somewhere on your page: Fluid Mosaic Model Phospholipid bilayer Selectively (semi) permeable membrane Cellular transport