Anatomy and Physiology 1 exam 1 1 Chapter 3 Cells 1 What is a cell and discuss its diversity When you break an organism down to its smallest part you get to the cell The cell is the smallest building block that everything living thing is made out of Life starts out with one cell and it divides repeatedly and eventually you have an organism The cell is the smallest living unit and it can vary in length and type depending on its function Its shape will determine its function nerve cell muscle cell blood cell ect The layout of the body starts with a cells then when a bunch of cell get together with a specific function you get a tissue Then a bunch of tissues together make an organ Then organs together make a human body So cell Tissue Organ Body 2 Discuss a generalized cell List the three main parts of a cell and their functions A cell is composed of carbon hydrogen nitrogen oxygen mainly and other trace elements Every cell has three main parts and these are the cytoplasm plasma membrane and the nucleus If you think of the cell as being a city all the organelles compartments in the cell make better sense and are easier to understand Think of the plasma membrane as the border control of the cell These are the gates and they only lets certain molecules in It seperates the intracellular fluid or the fluid in the cell from the extracellular fluid or the fluid outside the cell The cytoplasm is the air of the city It is everything that surrounds the cell and specifically it is a fluid The organelles are surrounded by the cytoplasm The nucleus is like the city hall of the cell it controls the cell and is in the center of the cell Tony Berardi 2 3 Discuss the fluid mosaic model of membrane structure This refers to the plasma membrane or the border control of the cell The plasma membrane is the barrier around the cell that controls what gets into and out of the cell The membrane is a bilayer made of phosolipids with a polar head and a nonpolar tail The heads of the phosolipids are on the outside of the bilayer and these are hydrophilic Meaning they are attracted to fluid such as the extra and intracellular fluid The tails of each phosolipid are faced inward away from the fluid and are hydrophobic These phosolipids can move side to side but they cannot switch sides because the hydrophobic end would have to touch to fluid to do that Understanding the nonpolar concept of the hydrophobic tails makes knowing what molecules that can enter the cell much easier 4 List and describe the plasma membrane specializations Along with the bilayer mentioned above the phosolipids have additional molecules attached to them Around 20 of the bilayer is cholesterol which is shaped as nonpolar rings that help stabilize the phosolipids This shows that cholesterol is essential to normal function of the body just having too much is bad There are proteins embedded in the bilayer that serve as transport molecules to help substances into and out of the cell These are integral proteins and peripheral proteins o By name the integral proteins and in the bilayer with half in the hyrophobic section and the other half sticking out of the cell These are transport molecules o Peripheral proteins aren t attached to the bilayer These are on the integral protiens on the periphery and function as support and enzymes o Some just float around the cell for support and if a sugar group is attached it is called a glycoprotein Tony Berardi 3 The function of the membrane is to control what gets into and out of the cell and for communication with other cells Communication is done by junction which are when surrounding cells fit together like a puzzle There are three Tight junctions are when the cells fuse together tightly with no space between them The integral proteins latch onto each other and fuse making an impermable junction This prevents molecules from passing through the juctions Desmosomes are formed when two cells are joined by protein filaments and the space between them is wider that in tight junctions Gap junctions are a communicating gap between cells and they are connected by connexons a protein These junctions are how all the different epithlium tissues which is a mass of cells with a function are connected 5 Discuss membrane transport Differentiate between active and passive transport Remember the metaphor of the plasma membrane to border control Now this will make much better sense The membrane controls what enters and leaves the cell and only certain molecules can thus it is selectively permeable So nutrients for the cell can pass in and harmful substances bacteria viruses can t Alternatively proteins stay in the cell and water can leave as needed Substances can move through the barrier via active need energy to transport or passive transport no energy depending on the substances structure 6 Compare and contrast simple diffusion facilitated diffusion osmosis and filtration There are essentially four types of passive transport There is simple diffusion which is when a substance moves down its concentration gradient This means something moves from an area of high concentration to area of low concentration A simple rule to memorize is that most everything moves from high to low concentration air gas exchange pressure blood etc This requires no energy Also there is a formula to figure out the diffusion rate but all you need to know is that the warmer a molecule is and the smaller the molecule is the faster it will diffuse down its gradient Filtration is like a type of diffusion so no energy input that happens in capillaries So think of the blood and oxygen at the capillaries or the ducts of the kidney Tony Berardi 4 Osmosis is another type of diffusion that involves the movement of a solvent usually water The water will move from an area of low concentration of solutes salt sugar etc to an area of high solute concentration This makes sense and follows the basic rule of diffusion because the water is moving from an area of high water to an area of low water If you have low solute concentration you would have a high water concentration and vice versa The terms for osmosis that are relative to two environment are isotonic meaning the solute concentration is equal hypertonic meaning that environment has an excess of solute hyper compared to water and hypotonic meaning the environment has less solute hypo compared to water So what would a cell do in a hypertonic solution Water would leave because the hypertonic solution would
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