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Transcript
Macromolecules, the Cell Membrane, and Movement Sections 7.3 and 2.3 Organic Macromolecules • Organic matter has carbon in it, but it has a few exceptions including carbon dioxide, carbon monoxide, etc. Living things are made up of carbon and other elements. • 4 Categories of Organic Macromolecules – Carbohydrates, Nucleic Acids, Proteins, and Lipids Carbohydrates • Carbohydrates are sugars made of carbon, hydrogen, and oxygen. • They are used as an energy source and can be either monosaccharides or polysaccharides – Monosaccharides: single chain sugars; used quickly; EXAMPLE: glucose – Polysaccharides: multi-chain sugars; put into storage; EXAMPLE: glycogen Nucleic Acids • Nucleic Acids are made up of nucleotides – Nucleotides have a sugar, phosphate, and a base • They transmit genetic information in the form of DNA and RNA – DNA: deoxyribonucleic acid – RNA: ribonucleic acid Proteins • Proteins are made up of amino acids. – Structural proteins provide shape and structure for a physical trait. EXAMPLE: hair – Enzymes are specialized proteins that bind to activation sites and speed up a chemical reaction. LIVING THINGS NEED ENZYMES TO CARRY OUT THE FUNCTIONS OF LIFE!!! Lipids • Lipids are fats and oils. • Lipids have a hydrophilic ( “water”“loves” ) head and a hydrophobic (“water” “fear”) tail • LIPIDS MAKE UP MEMBRANES IN CELLS!!! Cell / Plasma Membrane • Composed of double layer of phospholipids and proteins • Surrounds outside of ALL cells • Controls what enters or leaves the cell Outside of cell Proteins Carbohydrate chains Cell membrane Inside of cell (cytoplasm) Protein channel Lipid bilayer copyright cmassengale 7 Phospholipids • Heads contain glycerol & phosphate and are hydrophilic (attract water) • Tails are made of fatty acids and are hydrophobic (repel water) • Make up a bilayer where tails point inward toward each other • Can move laterally to allow small molecules (O2, CO2, & H2O to enter) copyright cmassengale 8 The Cell Membrane is Fluid Molecules in cell membranes are constantly moving and changing copyright cmassengale 9 Cell Membrane Proteins • Proteins help move large molecules or aid in cell recognition • Peripheral proteins are attached on the surface (inner or outer) • Integral proteins are embedded completely through the membrane copyright cmassengale 10 GLYCOPROTEINS Recognize “self” Glycoproteins have carbohydrate tails to act as markers for cell recognition copyright cmassengale 11 Cell Membrane in Plants Cell membrane • Lies immediately against the cell wall in plant cells • Pushes out against the cell wall to maintain cell shape copyright cmassengale 12 Diffusion • Solutions have solutes dissolved in solvents (e.g. salt dissolved in water). The ratio between the solute and the solvent is the concentration. • Usually molecules move from a HIGHER concentration gradient to a LOWER one through diffusion. For example, this is why you are able to smell freshly bakes cookies after they have started to cook. • When diffusion occurs, molecules move so that they are equally spread out in a space. This is called equilibrium. Diffusion Osmosis • Osmosis is the diffusion of water. Cells need water, so this is especially important in Biology. • Water is attracted to the solute and moves towards it because it is going from a HIGHER concentration of water to a LOWER concentration. – Isotonic: solution outside of the cell is EQUALLY concentrated; water moves in and out but there is no net change – Hypertonic: solution outside of the cell is MORE concentrated; water leaves cell – Hypotonic: solution outside of the cell is LESS concentrated; water enters the cell Osmosis Facilitated Diffusion • Sometimes molecules that are moving from a higher concentration to a lower concentration cannot pass through a cell membrane because they are too large. • Facilitated diffusion occurs when special proteins in the cell membrane serve as a VIP doorway for these large molecules. Facilitated Diffusion Active Transport • When molecules move AGAINST the concentration gradient, this is called active transport • Molecules can either be pumped across the membrane using a specialized protein pump or be escorted by parts of the membrane that break off and surround the material. – Endocytosis: when the membrane surrounds a molecule to go INTO the cell – Exocytosis: when the membrane surrounds a molecule to go OUT of the cell Active Transport – Protein Pump Active Transport - Endocytosis Active Transport - Exocytosis