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Chapter 8

Chapter 8. Cells and Their Environment. Plasma = liquid portion of blood It’s a aqueous solution. (H 2 0) It’s the cell’s environment Contains: CO 2 , O 2 , glucose, enzymes, salts, proteins like hormones and insulin and platelets among other things. 8-1 Cell Membrane.

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Chapter 8

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  1. Chapter 8 Cells and Their Environment

  2. Plasma = liquid portion of blood It’s a aqueous solution. (H20) It’s the cell’s environment Contains: CO2, O2, glucose, enzymes, salts, proteins like hormones and insulin and platelets among other things

  3. 8-1 Cell Membrane • How does a cell membrane (CM) help a cell maintain homeostasis? • How does the CM restrict the exchange of substances? • What are some functions of membrane proteins? A simple defect in a cell membrane protein can make a life or death difference, in people who have cystic fibrosis, the cell membrane does not work properly.

  4. Roles of the CM • Surrounds every cell (support; contain) • Protects the cell (identification; antigens) • Regulates transport(gate keeper; pores and channels) • moves substances in and out • blocks substances from entering/exiting • Moves messages between cells (communication) • Maintains consistency and order

  5. Homeostasis • The maintaining of a constant, steady internal state while the outside environment fluctuates (ex: environment moves between hot and cold while thermostat maintains constant room temp) • Cells live in an aqueous (water filled) environment – must constantly regulate amount of water inside cell • Cells spend LOTS of energy maintaining homeostasis

  6. Structure of membraneYou should be able to draw and label this pictureHolt pg. 177

  7. Lipid bilayer • Called the “phospholipid bilayer” • Phosphates (PO4-3) represented by circles • Lipid “tails” represented as squiggly lines • Two rows of phospholipids = bilayer • Phosphate areas are polar (charged) and attract water. This are called hydrophilic • Lipid areas are nonpolar and repel water. This is called hydrophobic • CM idea of “water balloon”, really made of WAXY or OILY layer

  8. Functions of lipid bilayer • Water is inside cell (cytoplasm is mostly water) • Water is outside cell (extracellular fluid) • Chemical reactions in cells take place in water • Waxy CM keeps everything in the right place • Only certain substances can pass through the membrane (usually small and nonpolar like CO2, oxygen and simple sugars)

  9. Membrane Proteins • CMs are also made of proteins • Some proteins run throughout the depth of the membrane and are called Integral Proteins • “something that is integrated is throughout a process, program or structure”….. Rebar in integrated into concrete roads; academic vocabulary is integrated into GLHS • Other proteins are just on the outside edge or the inside edge and are called Peripheral Proteins • “ something at the periphery is at the edge”…. Like your peripheral vision. • Proteins are made of amino acids with polar and non-polar regions so they are three dimensionally ‘locked’ in the membranes by their charge and their shape.

  10. Types of CM Proteins • Cell-Surface Markers • Special chains of sugars • Used for Identification (like a name tag or bar code) • Receptor Proteins • Sense cells surroundings • Cause changes to the cell (different shape or chemical reaction) • Junctions • Connect cells to other cells (velcro or rivet); tight junction, gap junctions, plasmodesmata • Enzymes • Help to coordinate and regulate chemical reactions • Transport Proteins • Move substances across CM • Especially if substance is required but is large, polar or charged.

  11. Review - Proteins • Made of amino acids • Made in the RIBOSOMES • Coded for by DNA directions • Contain C,H,O and N and S • Used by organisms/cells for: • Storage (egg white stores amino acids) • Movement (muscle contractions) • Structure (hair, nails, hooves and cytoskeleton) • Transport (hemoglobin carries oxygen and move substances into cells ) • Regulation (enzymes cause reactions) • Defense (antigens and surface markers) • Communication (neurotransmitters between nerves) • Hormonal proteins (important compounds like insulin are protein)

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