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Transcript
The Cell and Its Environment Fall 2010 What is a cell? A cell is the basic unit of living things. Some living things are composed of only one cell and are called UNICELLULAR organsims. Organisms that have many different cells are called MULTICELLULAR organisms. Homeostasis – Maintaining a Balance Cells must keep the proper concentration of nutrients and water and eliminate wastes. The plasma membrane is selectively permeable – it will allow some things to pass through, while blocking other things. What is the function of a cell? * All living things obtain energy different ways through the processes of photosynthesis or respiration. Since organisms must use energy there are certain things that have to get into and out of the cell to enable the organism to use or convert energy. Materials that must be able to move INTO ANIMAL cells: 1.Oxygen 2. Water 3. Particles of food 4 Minerals and vitamns for proteins(K, Na, Fe) Materials that must be able to move OUT of ANIMAL cells: 1. Carbon dioxide 2. Waste materials Materials that must move INTO PLANT cells: 1. Sunlight 2. Water 3. Carbon dioxide Materials that must be able to get OUT of PLANT cells: Oxygen Waste products What lets stuff in and out of the cell? Cell Membrane Definition- a membrane that controls how materials move into or out of a cell. It acts as a gatekeeper to allow things in and out Cell of the cell. Membrane Overview Cell membrane separates living cell from nonliving surroundings thin barrier = 8nm thick Controls traffic in & out of the cell selectively permeable allows some substances to cross more easily than others hydrophobic vs hydrophilic Made of phospholipids, proteins & other macromolecules What is a cell membrane? Cell membranes are the outside covering of a cell that allows things in and out of the cell. Cell membranes are composed of 3 things: 1. double layer of phosolipid molecules (fats) 2. Proteins – moves large molecules. 3. carbohydrate chains 4. cholesterol 3 Types of Membrane Proteins Transport large charged molecules!! 1.Receptor Proteins: Determine what particles can pass through the membrane. 2. Enzymes: Serve as enzymes (may speed reactions). 3.Transport proteins:moves substances across the membrane. This moves K, Na, Fe, Water, amino acids any charged particle. Phospholipids – allows not charged small particle through! Phosphate Fatty acid tails – hydrophobic Phosphate group head - Fatty acid hydrophilic Arranged as a bilayer Aaaah, one of those structure–function examples Why does the phosolipid align in 2 layers? Phosphate head – hydrophilic because it is charged opposite of water and they attract each other. They will be on the outside touching the Water. Fatty acid tail – hydrophobic because it has no charge and is repelled by water that is charged. They are pushed way from water and align on the inside. Molecules that can move through phosolipid part of membrane Oxygen, carbon dioxide !! ANY PARTICLE THAT IS SMALL AND NOT CHARGED!!! ttp://www.teachersdomain.org/asset/tdc02_int_membraneweb/ Any particle that is charged cannot move through membrane because of lipid charged tails. Function of Carbohydrates in Membrane Attached to the membrane’s proteins act as identification tags. This allows cells to tell each other apart. A heart cell will have different carbohydrates than a heart cell. Function of cholesterol in Cell Membrane Cholesterol strengthens the cell membrane. Structure of the Cell Membrane Outside of cell Proteins Lipid Bilayer Transport Protein Animations of membrane Go to structure Section: Carbohydrate chains Phospholipids Inside of cell (cytoplasm) How does stuff get in and out of the cell? The cell membrane is what allows stuff in and out of the cell. The membrane is selectively permeable. Selectively permeableDefinition- means that some substances can cross the membrane while others cannot. Polar heads love water & dissolve. Non-polar tails hide from water. Carbohydrate cell markers Proteins Fluid Mosaic Model This model describes the structure of the cell membrane!! How do phosolipids control what can pass through Membrane? The hydrophobic tails will not let any substance pass through that has a charge(ion)(hydrophilic). Only substances that are not charged (hydrophobic)can pass through. If they cannot pass through the membrane, then they must go through the must get in another way. Fluid Mosiac Model of Cell Membrane This model describes the structure of the cell membrane because it acts likes a liquid. 1. The cell membrane is flexible not rigid. The phosolipids move from side to side. 2. There are so many molecules that make up the membrane that it looks like a mosiac. Structure of the Cell Membrane Outside of cell Proteins Lipid Bilayer Transport Protein Animations of membrane Go to structure Section: Carbohydrate chains Phospholipids Inside of cell (cytoplasm) Cell Transport To understand cell transport, you must understand how molecules move. All molecules move. Even solids vibrate. Most of the cell environment is liquid. Molecules want to reach EQUILIBRIUM! Equilibrium – equal amount of molecules everywhere(across cell membrane). Diffusion Movement of molecules moving from an area of higher concentration to an area of lower concentration. Example: air freshener, perfume, food cooking, food coloring in water. Increase temperature; increase rate of diffusion Diffusion occurs in liquids and gases. Which direction will molecules flow? Concentration Gradient Difference in concentration of molecules that makes the molecules move. They move from highest level to the lowest level. The greater the difference the faster the molecules move. Concentration Gradient Diffusion video http://video.search.yahoo.com/search/vide o;_ylt=A0SO8ZpVTNdMKS8AS3H7w8QF; _ylu=X3oDMTBncGdyMzQ0BHNlYwNzZ WFyY2gEdnRpZAM-?p=diffusion&ei=utf8&fr2=tab-img&n=21&tnr=21&y=Search How does stuff get in and out of the cell? Substances that move into and out of a cell do so by means of one of two processes: PASSIVE TRANSPORT or ACTIVE TRANSPORT. Types of Cell Transport No Energy Passive Transport Energy Active Transport Diffusion Faciliated diffusion(osmosis) Bulk transport endocyotsis exocytosis Passive Transport http://video.search.yahoo.com/search/vide o;_ylt=A0PDoX1LTNdMKyoAZayJzbkF?ei =UTF-8&p=passive%20transport&fr2=tabimg&fr=The Cell and Its Environment 2010.ppt Passive Transport Definition: is the movement of dissolved materials across a cell membrane without using the cells energy. Energy required: NO Type of Transport: PASSIVE Diffusion or facilitated diffusion(osmosis) Passive Transport Diffusion – passive transport Definition: is the process by which molecules move from an area of higher concentration to an area of lower concentration(liquids or gases). Ex: If a bacteria lives in a pond, the water in the pond contains oxygen molecules. The area inside the bacteria cell has a lower amount of oxygen than the pond. So, the oxygen molecules outside of the cell will freely move into the cell. Diffusion CONT’D Energy required: NO Type of Transport: PASSIVE Faciliated Diffusion- Type of Passive Transport Movement of molecules across the cell membrane but using a carrier molecule(protein) NO ENERGY Follows the same rules as diffusion but these molecules cannot slip through the phosolipid tails. Osmosis – facilitated diffusion Definition: is the diffusion of water molecules across a selectively permeable membrane(sometimes uses carrier protein). -Many life processes require water, therefore; all cells must have the appropriate amount of water in them to function. Energy Required: NO Type of Transfer: PASSIVE Osmosis – Type of Faciliated Diffusion Movement of WATER across the cell membrane. Cells are 75 – 90 % water so osmosis is an important process. Water molecules will continue to move until EQUILIBRUIM is reached. NO ENERGY NEEDED!! Click on link below to see the flow of water during osmosis. http://people.eku.edu/ritchisong/RITCHISO /osmosis3.gif What Makes Water Move? It is determined by the type of surroundings the cell is placed that determines the concentration gradient Solution: mixture in which molecules of one substance are evenly dispersed. Solvent: substance that makes up the greatest part of the solution.(usually water) Solute: substance dissolved in the solvent.(K, NaCl, O Na, Amino acids) Types of solutions cell can be placed Isotonic Hypertonic Hypotonic Isotonic Concentration of solutes are EQUAL inside and outside the cell. Why do they give a person who is dehydrated a saline(minerals and salt) drip(IV) vs. distilled 100% water. Hypertonic Solutes on the outside of cell is higher. Water leaves cell This is why slugs shrivels up with salt. Animals that leave in salt water have adaptations to deal with the salt in the water. This is why you do not drink salt water. How will road salt affect roadside plants? Hypertonic Solution Cells are shrinking because more solute outside so water leaves cell. Hypotonic Concentration of solute is greater inside the cell so water moves in. Animal cell will burst. Plant cells fill vacuole creates RIGOR! This is what causes plant to stand up. Hypotonic Solution Hypotonic Blood Cells What do cells look like when they have too much or too little water? Video – diffusion, osmosis & solutions http://video.search.yahoo.com/search/vide o;_ylt=AgiX5UpIi9KIAFvWdkNyYsubvZx4? p=diffusion&toggle=1&cop=mss&ei=UTF8&fr=yfp-t-701 Facilitated Diffusion CONT’D Active Transport Sometimes cells need materials to flow the opposite direction of the flow of diffusion. In this case the cell would need to use ACTIVE TRANSPORT to carry these materials in and out. DEFINITON: is the movement of materials a cross a cell membrane against the gradient using cellular energy. The cell uses its’ energy so the transport proteins “pick up” materials and “carry” them across the membrane. Examples of substances that are carried in and out of the cell this way are: calcium, potassium, and sodium. ENERGY REQUIRED: YES TYPE OF TRANSPORT: ACTIVE Active Transport – the energy changes the shape of the protein to match the molecule Once the molecule is through the membrane the protein will change its shape back! http://video.search.yahoo.com/search/vide o;_ylt=A0SO8ZrQT9dMlgEAXAD7w8QF;_ ylu=X3oDMTBncGdyMzQ0BHNlYwNzZW FyY2gEdnRpZAM?p=active+transport&ei=utf-8&fr2=tabimg&n=21&tnr=21&y=Search Bulk Transport – No energy Particles too large to move through the membrane.(Particle of food, proteins) 2 Types of Bulk Transport 1. Endocytosis 2. Exocytosis Steps of Endocytosis 1. Molecules move into the cell by the cell surrounding the particle and forming a vacoule around it. 2.Once vacuole is in cell, lysosomes will place digestive juices in the vacoule and break up the food or particles. Pinocytosis: liquid is surrounded brought into cell. Phagocytosis: solids are surrounded and brought into the cell. SOLID LIQUID Endocytosis http://video.search.yahoo.com/search/vide o;_ylt=A0SO8Z1uUddMelcAfjn7w8QF;_ylu =X3oDMTBncGdyMzQ0BHNlYwNzZWFy Y2gEdnRpZAM-?p=endocytosis&ei=utf8&fr2=tab-img&n=21&tnr=21&y=Search Steps of Exocytosis 1. Opposite of endocytosis 2. Vacoule send to the cell membrane with waste and particles and ejected out of cell membrane. Exocytosis Exocytosis http://video.search.yahoo.com/search/vide o;_ylt=A0SO8ZrfUddMOygAFNj7w8QF;_yl u=X3oDMTBncGdyMzQ0BHNlYwNzZWFy Y2gEdnRpZAM-?p=exocytosis&ei=utf8&fr2=tab-img&n=21&tnr=21&y=Search Types of Cell Transport No Energy Passive Transport Diffusion Faciliated diffusion Bulk transport endocyotsis exocytosis Energy Active Transport