MCAT Biology Practice Exam Questions Graded A+ (Answered)

MCAT Biology Practice Exam Questions Graded A+ (Answered) The chemical reaction that breaks down all the major macro-molecules - ANSWER Hydrolysis What is the strongest type of INTER-molecular bonds? - ANSWER Hydrogen bonds are the strongest intermolecular bonds.... diople-dipole bonds are weaker. . . Vander wall bonds are the weakest. Why is water a liquid at high temperatures? - ANSWER Hydrogen bonding bonds the water molocules closer together. What is an ampipathic molecule? give an Example. - ANSWER A molecule with both hydrophobic and hydrophilic regions. Example: PhoshpoLipid (Phospho=philic,lipid= phobic) What is a lipid? - ANSWER A lipid is a biological molecule with low solubility in water. Lipid means fat. Liposuction is fat removal. Peptides are NOT lipids. What are the 6 major groups of lipids? - ANSWER 1) fatty acids... the next 3 have a 3-carbon back bone: 2) Tri-glyceride 3) Phospholipids 4) Glycolipids 5) Steroids 6) Terpenes - A large class of organic compounds. examples: smelly pine oils, beer hops aroma and vitamin A. What is the structure of a Tri-glyceride? - ANSWER triglicerides are esters. Composed from 3 carbon glycerol backbone and 3 fatty acid chains dangling. Each carbon chain is attached by an ester bond. What happens if you add water to an ester group in a Tri-glyceride? How is this reaction rate increased? - ANSWER Water cleaves the ester bond into an alcohol and a carboxylic/ fatty acid. LIPASES speed are the enzyme that speed this reaction. in terms of water solubility, What is important to know about the longer the carbon chain in a Tri-glyceride when broken down? - ANSWER longer carbon chains are less water soluble. In longer chains the polar carboxylic acid are less significant. How soluble is a Shorter chain fatty acids? - ANSWER Shorter chain fatty acids are slightly water soluble. explain what is so special about Saturated Fatty Acids........Also, explain the melting point. - ANSWER saturated fatty acids have only single, alkane bonds along the carbon chain. They have a straighter chain and have more van der wall forces, and therefor a higher melting point. explain what is so special about Unsaturated Fatty Acid.... Also, explain the melting point. - ANSWER Unsaturated fatty acids have at least one double bond. They are not saturated with Hydrogen. they have a LOWER melting point. At room temperatures unsaturated fatty acids may be oily, like Healthy peanut butter. explain the phospho-lipids structure. Where are phoshpo lipids common? - ANSWER Phospholipids are also built on a 3 Carbon backbone. One of the carbon has a Phosphate PO4 group. the other 2 carbons have carbon chains attached by a ester bond. This is the lollypop of the cell membrane. Esters have 2 oxygens. What regions are poplar nonpolar in a membrane? - ANSWER 1)the phosphates are Polar, water lovin, hydro philic regions that face the outside. 2) Nonpolar, hydro phobic carbon chain regions face the inside. Explain glycolipids structure. - ANSWER glycolipids have 3 carbon backbone with 2 Carbon chains attached by an ester group. THe third carbon has a carbohydrate What do steroids look like? - ANSWER Slightly amphipathic 4 ring structures lipids are insoluble. So how do they move through the blood? - ANSWER They are usually carried by lipoproteins, like HDL or LDL. What are the major classes of lipoproteins? - ANSWER 1) Chylomicrons which are the largest 2) VLDLs these are low denstiy, but large. 3) LDLs 4) HDLs. these high density lipids are the smallest, and called good proteins. What are proteins made up of? - ANSWER one or more chains of amino acids, perhaps in a crazy ass arrangement. describe amino acid structure. - ANSWER Amino acids have 4 parts attached to the alpha carbon. 1. the amino group, which is NH2 2. the R group, which is one of 20 choices 3. the Carboxylic acid or C O O the last thing attached to the Carbon is the Hydrogen. What are the basic amino acids? - ANSWER Hal Histidine Arginine Lysine What are the acidic amino acids? - ANSWER Aspartic acid and Glutamic acid What are the nonpolar amino acids? - ANSWER Poor LTMG Is Venezuelan At Parties 1) Phenylalanine 2) Leucine 3) Tryptophan 4) Methionine 5) Glycine 6) Isoleucine 7) Valine 8) Alanine 9) Proline What is the primary structure of a protein? - ANSWER Sequence of amino acids and Location of disulfide bonds between cistine residues What is the secondary structure of a protein? - ANSWER 1) Twisting of the alpha helix 2) Beta sheets What is the tertiary structure of a protein? - ANSWER 3D structure including bending What is the quaternary structure of a protein? - ANSWER Multiple proteins in formation What are the five forces that create tertiary structure? - ANSWER 1) Covalent 2) Disulfide bonding between cysteine residues (Bond itself creates tertiary structure) 3) H bonds 4) HPhob away from cytosol and Hphil interactions towards cytosol 5) Van Der Waals (dipoles, instantaneous dipoles) What levels of structure are disrupted during the denaturation process? - ANSWER Secondary - quaternary What is the difference between a proteoglycan and a glycoprotein? - ANSWER Glycoproteins: 1) Made of protein and carbohydrate 2) More stable than proteins 3) Often used in IS to bridge the cellular membrane. 4) Ratio - have more proteins Proteoglycans: 1) Special class of glycoprotein 2) Contain extra carbohydrates 3) Structure = protein with one or more glycosaminoglycan chains. 4) Ratio - have more carbs What is the empirical formula for any carbohydrate? - ANSWER CH2O Describe the chemical structure of glucose - ANSWER 1) Aldehyde 2) Has 4 chiral carbons 3) Fischer - R, L, R, R 4) 6 membered ring where one of the ring members is oxygen 5) C1 - anomeric carbon Where is glucose stored in alpha linkages? - ANSWER Animals (glycogen) and plants (starch) Who stores glucose with beta linkages? - ANSWER beta linkages are in Plant cell walls. Cellulose. What molecule is added to glycogen, starch, and cellulose to break off individual glucose molecules? - ANSWER Water Hydrolysis reaction. and enzymes like amylase speed it up. What are the four macromolecules? - ANSWER Protein Lipids Carbohydrates Nucleic acids What are the three parts of a nucleotide? - ANSWER Ribose sugar Nitrogenous base PO4 group What molecule breaks up nucleic acids into nucleotides? - ANSWER Water. with the help of nucleases. What are some other important nucleotides? - ANSWER FADH, NADH, ATP cyclic AMP What are minerals? - ANSWER 1) Inorganic elements that typically exist in the form of ions inside and outside of the cell. 2) Function to: a) Establish electrochemical gradients b) Act as cofactors to enable protein function c) Form matrix compounds in bone and etc What are enzymes? - ANSWER Typically a protein that Increase the rate of reaction by lowering activation energy. but ribosomes are enzymes What is activation energy? - ANSWER energy needed to break the bonds of the reactants creating the transition state, or the species between the reactants or the products T/F: enzyme is typically larger than the substrate - ANSWER True Where does a substrate attach to an enzyme? - ANSWER at the active site What are the two hypotheses of enzyme and substrate interactions? - ANSWER 1) Lock and Key Model 2) Induced Fit Model T/F: One enzyme is tailor made for one reaction. - ANSWER True: Enzyme specificity; gives the cell more control in regulating chemical reactions What are saturation kinetics? - ANSWER Since a single enzyme molecule works on one set of substrate at a time, the reaction rate increases when we add substrate only as long as there are unoccupied enzyme molecules. Once we reach saturation, adding more substrate won't increase the reaction rate. Enzyme is not used up! What are the factors that affect enzymatic reactions? - ANSWER 1) Optimal temp (rate increases as temp incr until end is denatured) 2) Optimal pH How do cells regulate enzymes? - ANSWER 1) Inhibition 2) Production of inactive form, activate only when needed What are the general types of enzyme inhibition? - ANSWER 1) Feedback inhibition 2) Chemical inhibition (poisons) What is feedback inhibition? - ANSWER When the product of a reaction near the end of a chain of reactions inhibits the function of an enzyme in an earlier reaction of the chain. What are specific ways in which enzymes are inhibited (mechanism)? - ANSWER 1) Competitive 2) Non-competitive 3) Irreversible What is competitive inhibition? - ANSWER 1) Compete for active site. 2) Can be overcome by increasing substrate concentration. What is non-competitive inhibition? - ANSWER 1) Doesn't attach to active site, but changes the shape of the enzyme so the substrate doesn't fit as well. 2) Reduces affinity for enzyme to substrate What is irreversible inhibition? - ANSWER 1) Something covalently bonds to active site. 2) Cannot be removed. What is respiration? - ANSWER The E requiring stages of metabolism Where does glycolysis take place? - ANSWER In the cytosol of the cell Does glycolysis require oxygen? - ANSWER No Is glycolysis poisoned by oxygen? - ANSWER No What is the net ATP produced by glycolysis? - ANSWER 1) 2 ATP 2) 2 NADH 3) 2x 3C pyruvates If oxygen is not present, or the organism is incapable of aerobic respiration, what happens to the NADHs at the end of glycolysis? - ANSWER Fermentation: The NADHS are oxidized back to NAD+ in a process that removes 1C from each pyruvate to produce CO2 and EtOH(yeast)/Lactic acid If oxygen is present, what happens to the products of glycolysis? - ANSWER They enter the mitochondria. What is the E cost of transporting one NADH into the mitochondria? - ANSWER 1 ATP per NADH across inner membrane How many ATPs does each NADH produce during the ETC? - ANSWER Each NADH produces 3 ATPs via ETC In the mitochondrial matrix, what happens to the pyruvates? - ANSWER Each pyruvate is converted to acetyl-CoA, which transfers 2C to oxaloacetate to make citrate, beginning the TCA cycle. What are the energetic products of the TCA cycle? - ANSWER 1 ATP 3 NADH (Each NADH is converted to 3 ATPS via ETC) 1 FADH (Each FADH is converted to 2 ATPs via ETC) Overall, aerobic respiration of a single glucose molecule results in a net of how many ATPs? - ANSWER 36 What is the ETC? - ANSWER