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Chemistry and Cells Important Definitions: Define these terms (5 word definitions or less) 1. Elements 13. Steroid 25. Active transport 2. Isotopes 14. Mitochondria 26. Passive transport 3. Ions 15. Golgi apparatus 27. Endocytosis 4. -Carbohydrate 16. Rough E. R. 28. Phagocytosis 5. Protein 17. Smooth E. R. 29. Exocytosis 6. Enzyme 18. Lysosomes 30. Pinocytosis 7. Nucleic Acid 19. Peroxisomes 31. Tonicity 8. Deoxyribonucleic 20. Cytoskeleton 32. Isotonic Acid 21. Centrioloes 33. Hypotonic 9. Ribonucleic Acid 22. A. T. P 34. Hypertonic 10. Lipid 23. Simple Diffusion 11. Saturated Fat 24. Facilitated 12. Unsaturated Fat Diffusion What are you made from? Atom: - smallest unit of matter; unable to be cut into smaller units and still remain the same. But what do you get when you cut an atom in half? Proton: -positively charged + Neutron: -neutral charge (no charge) Electron: - negative charge - What is an element? Element: - a group of atoms with the same structure and properties. What happens when an atom has more neutrons than it is supposed to? It creates an Isotope Isotopes: - an isotope is an atom with more, or less neutrons than other atoms of its element. “Normal” Carbon 12 6 Protons 6 Neutrons 6 Electrons Radioactive Carbon 14 6 Protons 8 Neutrons 6 Electrons What happens when you put two elements together? Compounds are formed. Compound: - two or more elements that are combined in specific proportions. Ex - NaCl a.k.a………. Salt Water, Water, Everywhere…………. Water: – the universal solvent + Polar (polarity) : having a definite positive and negative region on/in a molecule. That means that a water molecule is like a little magnet! Anything that is magnetic (polar) will stick to water!! Carbon Compounds ` Carbon: An element that is used by organic life forms to make molecules of the body. Macromolecule: Macro = large or many Molecule = arranged atoms Def: a large molecule composed of many units, or smaller molecules Ex: Glucose A single 6 carbon ring But if I add a lot of them together, I get: Complex Carbs A single unit is a MONOMER Having multiple units is a POLYMER First Carbohydrates What is a Carb? Chemical Structure of a Carbohydrate: Carbohydrates are ALWAYS found in the Ratio of : O H 1 Carbon to 2 Hydrogen to 1 Oxygen 1:2:1 Glucose (simplest carb): C6H12O6 Usually found in a ring C H What do we use Carbohydrates for? Energy Both short term and long term Long term Complex carbs like pasta Short term Simple Sugars What can you eat that has more energy than Carbs? Second Molecule: Lipids (fats) can store enough energy that they can even hold a flame! Plants store fat as liquids. Animals store fat as solids Lipid Composition: A Glycerin Molecule This acts as a connector for: Three Fatty acids The fatty acids contain several carbon groups that store energy in their bonds. What are the main types of Lipids? Neutral Fats Saturated and Unsaturated fats Used for long term energy storage! Phospholipids These make the cell membrane Steroids These are messages carried all about the body! They are NOT only the illegal drugs Third Molecule: Nucleic Acids: The cells Blueprint DNA & RNA DeoxyriboNucleic Acid & RiboNucleic Acid The building block” that makes nucleic acids are NUCLEOTIDES Phosphate group Ribose Sugar Nitrogen Base DNA: Contains all the genetic material that is needed by the cell. It is found in a “Double Helix”, two twists in a clockwise spiral. RNA: A single strand of Nucleotides that carries genetic material out of the nucleus to be processed. Proteins Forth Molecule: Proteins are used as structural components in all cells! Amino acids: - 20 different molecules that combine to make all proteins These are just two Protein Uses: Construction: Proteins build components inside and outside our cells Enzyme reactions: Enzymes are special proteins that build or break down materials inside or outside the cells What happens to the food you eat? Enzymes break down the food by acting as a Catalyst Enzyme (catalyst) Food particle (substrate) Catalyst – anything The enzyme attaches that makes a to the food at the reaction take place “active site” without being changed itself The enzyme breaks the food into smaller usable pieces (products) and releases them Cells Cells are the basic units of life All organisms are composed of cells. The activity of the body’s cells determines the both the structure and the function of the body. What we’ll be concentrating on is how things move in and out of cells. Plasma Membrane The membrane separates the cell interior (the cytoplasm) from the cell exterior (extracellular or interstitial fluid). 2 PM’s as seen w/ an electron microscope Both the cytoplasm and the exterior are aqueous, or water Cartoon representation of the PM based. The membrane is a bilayer (double layer) of phospholipids. A phospholipid is a molecule made of a glycerol backbone to which 2 fatty acids and one phosphorous-containing group are attached. Because the cell has water inside and water outside, the phospholipids have to line up in two lines to protect the fatty (hydrophobic) tails This structure has important implications for how things travel thru this membrane. Plasma Membrane Notice that the membrane is made up of more than just phospholipids. Proteins are found either embedded within the membrane itself (membrane proteins), or weakly associated with either the interior or exterior face of the membrane (peripheral proteins). The membrane also has molecules of cholesterol embedded among the phospholipids. Cholesterol increases the temperature range over which the membrane can function. Some integral proteins protrude into the ECF and have sugars attached. These are called glycoproteins. Glycolipids often function as markers that label the cell as “self,” i.e., not foreign. Other integral proteins function as: Enzymes Channels Transport molecules Structural supports The membrane is a fluid structure. There is a lot of lateral movement of phospholipids and unanchored proteins. B/C of its gel-like nature and the fact that it’s made up of many different parts, we say the membrane is a fluid mosaic. Crossing the Membrane Nutrients must get in and wastes must get out. Signaling molecules received by a cell may need to get in, while signaling molecules sent by a cell need to get out. Fluid must be able to get in and out. Certain ions must be able to get in and out. Types of transport: Passive Transport: Requires NO Energy Either by simple diffusion or through a membrane protein Active Transport: Requires Energy - ATP Always happens through a membrane protein and uses ATP to force a molecule across a membrane against concentration grandient Big Stuff? Membrane Proteins are adequate for bring small molecules into the cell or out of the cell. However, a different kind of active transport is necessary to move large things into/out of the cell – vesicular transport. There are 2 types of vesicular transport: exocytosis and endocytosis Exocytosis Exocytosis literally means “out of the cell” It accounts for hormone secretion, neurotransmitter release, mucus secretion, and, sometimes, ejection of wastes. Inside the cell, the substance to be exported is enclosed in a membranous sac called a vesicle. The vesicle will migrate to the PM fuse with it, and then rupture, spilling the contents into the extracellular space. Endocytosis Reverse of exocytosis. Allows macromolecules to enter cells. The substance is progressively enclosed by an enfolding portion of the plasma membrane. This forms a vesicle which will pinch off the plasma membrane and enter the cytosol where it is typically digested. Types of endocytosis are: Phagocytosis Pinocytosis (a.k.a. bulk-phase endocytosis) Receptor-mediated endocytosis Literally “cell-eating.” Cytoplasmic extensions called pseudopods “reach out and grab” large, solid material such as a clump of bacteria or cell debris, and then engulf it. The resulting vesicle is called a phagosome. Usually, the phagosome fuses with a lysosome, a membranous organelle that contains digestive enzymes, and its contents are digested. Macrophages and white blood cells are the most phagocytic cells in the body. Phagocytosis Pinocytosis Literally means “cell-drinking.” A bit of infolding plasma membrane surrounds a droplet of extracellular fluid containing dissolved molecules. This creates a tiny membranous vesicle. Most cells routinely perform this. Unlike phagocytosis, pinocytosis is unselective! Diffusion Many molecules have the capacity to diffuse right through the phospholipid bilayer. Nonpolar molecules move thru w/ ease b/c they do not mind the hydrophobic interior of the plasma membrane. Such molecules include O2, CO2, steroid hormones, fat soluble vitamins, and alcohol. What governs whether these molecules will move into or out of a cell? Its CONCENTRATION GRADIENT. Hydrophilic molecules must diffuse thru special protein channels in order to get thru the cell membrane. This type of transport through the plasma membrane is termed simple diffusion. Based on the concept of diffusion. Random molecular movement (due to KE) results in molecules moving from areas where their concentration is high to where their concentration is low. Note: Concentration is defined as how many molecules of a substance are present in a certain volume of liquid. The dissolved particles are the solutes while the fluid in which they’re dissolved is the solvent. Together, they create a solution. Note that in the above diagram, molecules are moving down their concentration gradient! Diffusion Some polar molecules enter cells via diffusion. They cannot go straight through the nonpolar lipid bilayer, so they require the assistance of proteins that act as carrier molecules. These carriers bind the substance (glucose and other simple sugars are the best examples) on one side of the plasma membrane and then change their conformation and release the substance on the other side of the PM. This is known as facilitated diffusion. Osmosis Osmosis is the diffusion of water through a semipermeable membrane. A membrane that is semipermeable allows some molecules to pass thru, but does not allow others. Water will diffuse from an area of high concentration to an area of low conc. It’s important that you understand the following: An area that has a high [water] has a low [dissolved particles]. An area that has a low [water] has a high [dissolved particles]. Right: Water molecules (black dots) move to the right since they are high in conc. on the left and low on the right. Water will diffuse from a solution with low a concentration into a solution of high concentration if they are separated by a semipermeable membrane. This is simply another way of saying that water will flow down its concentration gradient. (Permeable to water only) Tonicity Tonicity is defined as the ability of a solution to change the shape of a cell immersed in it due to changes in the cell’s water volume. A solution with the same concentration of nonpenetrating solutes as those found in cells are isotonic, i.e., “the same tonicity.” Cells exposed to such solution retain their normal shape and exhibit no net gain or loss of water. Most intravenous solutions are isotonic (e.g., 0.9% saline or 5% glucose). Why is this necessary? Red Blood Cells in an Isotonic Solution Suppose you placed a cell in a solution, and the cell shrank (the Tonicity technical term is crenated): The cell must have lost water which means that, the [nonpenetrating solutes] was higher outside the cell. Thus, the solution was Red blood hypertonic (hyper cells in a means greater than hypertonic usual). environment Suppose you put a cell in solution and the cell burst (lysed): Tonicity The cell must have gained water which means that the [nonpenetrating solutes] was higher inside the cell. Thus the solution was hypotonic (hypo means less than usual). Do you think pure water is hypertonic to cells or hypotonic to cells? RBC’s in a hypotonic environment Cell Junctions: How do cells connect? Gap Junctions: These are the way cells communicate with cells adjoining them. They are semi-permeable and allow many things across the boundary Desmosomes: Anchors holding cells to neighboring cells. Tight Junctions: Creates a water-tight bond between the cells like rivets.