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Honors Biology Midterm Review BASIC CHEMISTRY: ● Atom smallest unit of matter ○ Neutrons(N charge) and protons(+ charge) are packed in the atom’s nucleus ■ The negative charge of electrons( charge) and the positive charge or protons keep electrons near nucleus ○ Number of protons is the atom’s atomic number ○ Mass number is the sum of protons and neutrons in the nucleus ○ Same number of protons and electrons but different numbers of neutrons= isotopes ○ Atom may have 1, 2, or 3 electron shells ■ Number of electrons in cell determine chemical properties of atom ■ Want to fill their outer electron shells, and accomplish this by sharing, donating, or receiving electrons, also known as chemical bonds ● Isomers different compounds with same molecular formula ● Element a substance that cannot be broken down to other substances ○ 92 elements in nature, only a few exist in pure state ○ Trace elements 25 essential elements ● Compound a substance consisting of 2 or more different elements combined in a fixed ratio ● Covalent bond results when atoms share outershell electrons ○ A molecule is formed when atoms are held together by covalent bonds ○ Pull for shared electrons= electronegativity ● Ionic bond when attraction between 2 ions with opposite charge holds ions together ○ ion an atom or molecule with an electrical charge resulting from gain or loss of electrons ■ when electron is lost: positive charge results ■ when electron is gained: negative charge results ● Number of bonds a carbon makes: 4 ○ carbonbased molecules= organic compounds ○ chain of carbon atoms= carbon skeleton ○ compounds composed of only carbon and hydrogen= hydrocarbons ● Functional groups affects a biological molecule’s function in a characteristic way ○ Compounds containing functional groups are hydrophilic (waterloving) ○ Function groups are: ■ Hydroxyl group: consists of a hydrogen bonded to an oxygen ■ Carbonyl: carbon linked by a double bond to an oxygen atom ■ Carboxyl: consists of a carbon doublebonded to both an oxygen and hydroxyl group ■ Amino: composed of a nitrogen bonded to 2 hydrogen atoms and the carbon skeleton ■ Phosphate: consists of a phosphorus atoms bonded to 4 oxygen atoms WATER(H20): ● Has atoms with different electronegativities, oxygen attracts shared electrons more strongly than hydrogen ● Pull toward each atom is equal, because each atom has same electronegativity= nonpolar covalent bonds ● Unequal electron sharing= polar covalent bond ● Oxygen atom has slight charge and hydrogen has slight + charge ○ Molecules with unequal distribution of charges= polar molecules ● Heat energy associated with movement of atoms and molecules in matter ○ Heat must be absorbed to break hydrogen bonds, heat is released when hydrogen bonds form ○ water has a greater ability to resist temperature change than other liquids ● Temperature measures intensity of heat ● When water freezes each molecules forms a stable hydrogen bond with 4 neighbors ○ 3d crystal results with space between water molecules ○ ice is less dense than water, so it floats ● Hydrogen bond ○ Weaker than covalent bonds ○ Water molecules are electrically attracted to oppositely charged regions on neighboring molecules ○ Positively charged region is always a hydrogen atom, and it will share attractions with other electronegative atoms ● Cohesion hydrogen bonding causes molecules to stick together ○ much stronger for water than other liquids ○ Plants depend upon cohesion to help transport water and nutrients up plant ○ surface tension a measure of how difficult it is to break surface of liquid(hydrogen bonds are responsible for this) ● Adhesion keeps water drops in place, water seems to stick to surface, attraction of water to unlike substance ● Transportation ACIDS, BASES, ETC. ● Acids chemicals other than water that can contribute H+ to a solution ○ has a higher concentration of H+ than OH ● Bases accept hydrogen ions and remove them from solution ○ reduces H+ concentration ● Solution a liquid consisting of a uniform mixture of 2 or more substances ○ dissolving agent= solvent ■ Water is versatile solvent (results from its polarity) ○ substance that is dissolved= solute ● pH (potential of hydrogen) scale used to describe whether a solution is acidic or basic ○ ranges from 0 (most acidic) to 14 (most basic) ○ neutral (7) neither acidic or basic ● Chemical reaction formation of water from hydrogen and oxygen ○ reactants are converted into product ■ ex: H2 and O2 → H2O ● Neutralization reaction ○ when an acid and a base react to form water and a salt and involves the + combination of H ions and OH ions to generate water. The neutralization of a strong acid and strong base has a pH equal to 7. ORGANIC CHEMISTRY ● Carbohydrate range from small sugar molecules (monomers) to large polysaccharides (monomers linked together) ● ○ ○ ○ ○ ○ ○ ○ Carbon skeleton of monosaccharides vary in length Monosaccharides are main fuels for cellular work 2 monosaccharides can bond together to form a disaccharide in a dehydration reaction Polysaccharides are polymers of monosaccharides Starch storage polysaccharide composed of glucose monomers and found in plants Glycogen storage polysaccharide composed of glucose, hydrolyzed by animals when glucose is needed Cellulose polymer of glucose that forms plant cell walls ○ Cellulose polysaccharides used by insects and crustaceans to build exoskeleton ○ Polysaccharides are hydrophilic ● Lipids water insoluble (hydrophobic/ water fearing) compounds that are important in energy storage ● ○ Fats(aka triglycerides) are lipids made from glycerol and fatty acids ■ Fatty acids link to glycerol by a dehydration reaction ○ Fats with maximum number of hydrogens= saturated fats ○ Fatty acids containing double bonds= unsaturated fats ○ Phospholipids structurally similar to fats and are important component of all cells ■ Have hydrophilic heads that are in contact with water and hydrophobic tails that band in center of bilayer in cell membranes ○ Steroids lipids composed of fused ring structures ○ Cholesterol a steroid that plays a significant role in structure of cell membrane ● Proteins a polymer built from various combination of 20 amino acid monomers ● ○ Enzymes proteins that serve as metabolic catalysts, regulate chemical reactions within cells ○ Structural proteins provide associations between body parts ○ contractile proteins found within muscle ○ defensive proteins include antibodies of immune system ○ signal proteins hormones ○ receptor proteins serve as antenna for outside signals ○ transport proteins carry oxygen ○ Amino acids building blocks of proteins, have an amino group and a carboxyl group (covalently bonded to a central carbon atom) ■ hydrophobic or hydrophilic ■ link together by enzymemediated dehydration reaction to form polymeric proteins ■ covalent linkage of carboxyl group of one amino acid to amino group of other amino acid= peptide bond ■ polypeptide chain contains hundreds or thousands of amino acids linked by peptide bonds ○ Shape of proteins determines function ○ Denaturation will cause a polypeptide chain to unravel and lose their shape and function ■ can be denatured by changes in salt concentration, pH, and temperature ○ Protein can have 4 levels of structure primary, secondary, tertiary, and quaternary ● Nucleic Acids are also part of 4 classes of biological molecules ● Dehydration synthesis monomers are linked together to form polymers through dehydration reactions, which remove water ○ Polymers are broken by hydrolysis, the addition of water ● Polymers 4 classes of biological molecules containing very large molecules (macromolecules) ○ made from identical building blocks strung together ■ building blocks= monomers PLASMA MEMBRANE STRUCTURE, ETC. ● Plasma Membrane Structure composed of phospholipids and proteins ● Described as fluid mosaic ○ Fluid proteins can drift about in phospholipid ○ Mosaic proteins are embedded in phospholipids ○ Unsaturated fatty acids from phospholipids have kinks in tains that prevents them from packing tightly together, which keeps them liquid ○ Aided by cholesterol wedged in bilayer to keep liquid at lower temp. ○ Contain integrins give the membrane a strong framework by attaching to extracellular matrix and cytoskeleton ○ Some glycoproteins in membrane serve as id tags that are recognized by membrane proteins of other cells ○ ● Forms of transport across membrane ○ Selectively permeability membranes allow some substances to cross or be transported more easily than others ■ nonpolar molecules cross easily ■ polar molecules do not ○ Diffusion process in which particles spread out evenly in available space ■ particles move from area of more concentrated particles to an area where they are less concentrates ● ● ● ● ■ Particles diffuse down their concentration gradient and eventually reach equilibrium where concentration of particles is same throughout ■ Passive transport does not require energy ■ aquaporins transport proteins that help substances diffuse across membrane ■ Facilitated diffusion type of passive transport that doesn’t require energy ● some proteins function by becoming a hydrophilic tunnel for passage, and others bind to passenger, change shape, and release passenger on other side ○ Osmosis water moves across membranes in response to solute concentration in and out of cell ■ Osmoregulation organisms are able to maintain water balance within their cells Tonicity ability of a solution to cause a cell to gain or lose water ○ Isotonic indicates concentration of a solute is same on both sides ○ Hypertonic concentration of a s solute is higher outside of cell ○ Hypotonic higher concentration of solute inside cell Active transport move substances against concentration gradient ○ requires energy Exocytosis used to export bulky molecules Endocytosis used to import substances useful to the livelihood of the cell ○ Phagocytosis engulfment of a particle by wrapping cell membrane around it, forming vacuole ○ Pinocytosis fluids taken into small vesicles ○ Receptormediated endocytosis when receptors in a receptor coated pit interact with a specific protein, initiating formation of a vesicle Scientific Method process that uses questioning and evidence to solve problems or answer a question ● Hypothesis writing make a short definitive statement that can be proven true or false ○ If...Then ● Control experiment is an experiment that contains only one experimental variable ● Independent variable is the thing being tested ( what scientist changes) ● Dependent variable what changes when the independent variable changes (depends on outcome of independent variable) ○ Both should be organized on a graph ● Negative control an trial of the experiment in its natural state ○ shows a normal situation ● Positive control the part of the experiment that receives treatment ○ has a known result, if something doesn’t happen as planned something is wrong with experiment ● Conclusion writing may or may not support hypothesis ○ may be quantitative (numbers) or qualitative (appearance, properties, etc) Reactant substance that takes part in or undergoes change during reactions Products end product during a reaction Endergonic requires an input of energy and yields products rich in potential energy ● reactants contain little energy in beginning, but is absorbed from surroundings and stored in covalent bonds of the products ● Photosynthesis makes energyrich sugar molecules using energy from the sun Exergonic chemical reaction that releases energy ● reaction releases the energy in covalent bonds of reactants ● burning wood releases the energy in glucose, producing heat, light, carbon dioxide, and water ● Cellular respiration releases energy and heat and products, uses energy released to perform works ● Energy coupling use of exergonic processes to drive an endergonic one ○ energy released during exergonic reaction is used as energy in an endergonic reaction ATP (adenosine triphosphate) energy currency of cells ● adenine (nitrogenous base), ribose (fivecarbon sugar), and 3 phosphate groups ● immediate source of energy that powers most forms of cellular work ● Hydrolysis of ATP releases energy by transferring its third phosphate from ATP to another molecule ○ phosphorylation going from ADP + P to ATP, energy enters ○ ATP energizes molecules ○ ● ATP renewable energy source ● When energy is released in an exergonic reaction, such as breakdown of glucose, the energy is used in an endergonic reaction to generate ATP Energy of Activation the energy that must be available to break bonds to form new ones ● there is a lot of potential energy in biological molecules, it is not released spontaneously needs energy of activation Enzymes proteins that function as biological catalysts (drives or speeds up biological reactions) ● Speeds up the rate of the reaction by lowering energy of activation ● Substrate each enzyme has particular target molecule ● 3D shape ● Active site where the enzyme interacts with the enzyme’s substrate ○ substrate’s chemistry is altered to form the product of the enzyme reaction ● Denaturalization enzymes require certain conditions ○ 37 degrees C, or body temperature ○ pH around neutral for best results ○ Salt concentration can also denature an enzyme ● Inhibitors stops enzyme activity ○ Competitive inhibitors blocks active site so substrate cannot enter ○ Noncompetitive inhibitor binds somewhere else and changes shape of enzyme so substate no longer fits into active site ● Metabolism chemical processes occurring within a living cell or organism that are necessary for the maintenance of life ○ some substances are broken down to yield energy for viral processes while other substances, necessary for life, are synthesized