Exam 2 ULTIMATE STUDY GUIDE
Exam 2 ULTIMATE STUDY GUIDE NHM 361
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This 11 page Study Guide was uploaded by Soledad Tyler on Wednesday July 13, 2016. The Study Guide belongs to NHM 361 at University of Alabama - Tuscaloosa taught by in Summer 2016. Since its upload, it has received 35 views. For similar materials see Biochemistry in Human Nutrition and Hospitality Management at University of Alabama - Tuscaloosa.
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Date Created: 07/13/16
Mod 6-9 Study Guides Saturday, February 20, 10:23 PM Self-study guide for Module 6: Enzymes (ch. 10) Why are enzymes important? Know that enzymes are proteins that catalyze chemical reactions in the body by lowering activation energy required for reactions to proceed. Nearly all of these reactions are dependent on enzymes. Enzymes = proteins that act as catalysts for chemical reactions As catalysts, enzymes increase the rate of chemical reactions, but they are not changed by the reaction. Enzymes work by lowering the activation energy required for a reaction to proceed. • So, enzymes don’t force reactions that wouldn’t otherwise occur, but they significantly speed up reactions. Enzymes are well suited to their essential roles in living organisms in three major ways: They have enormous catalytic power, they are highly specific in the reactions they catalyze, and their activity as catalysts can be regulated. Define the following classes of enzymes: We will encounter kinase and phosphatase enzymes when we study pathways of macronutrient metabolism. a. Kinases any of a group of enzymes that catalyze the transfer of a phosphate group from a high-energy donor (such as ATP) to a substrate. E.g. Glucose + ATPHexokinaGlucose-6-phosphate + ADP b. Phosphatases any of a group of enzymes that catalyze the removal of an inorganic phosphate group What is a “cofactor”? What is a cofactor called when it is an organic molecule? A nonprotein molecule or ion required by an enzyme for catalytic activity. coenzyme An organic molecule required by an enzyme for catalytic activity. coenzyme An organic molecule required by an enzyme for catalytic activity. Which organic molecules often function as coenzymes in the body? Vitamins Define the following terms: a. Absolute specificity The characteristic of an enzyme that it acts on one and only one substance. b. Relative specificity The characteristic of an enzyme that it acts on several structurally related substances. c. Apoenzyme A catalytically inactive protein formed by removal of the cofactor from an active enzyme. d. Holoenzyme a complete enzyme-cofactor complex e. Active site The location on an enzyme where a substrate is bound and catalysis occurs. f. Competitive enzyme inhibition An inhibitor that competes with substrate for binding at the active site of the enzyme. of the enzyme. g. Noncompetitive enzyme inhibition An inhibitor that binds to the enzyme at a location other than the active site. h. Feedback inhibition A process in which the end product of a sequence of enzyme-catalyzed reactions inhibits an earlier step in the process. i. Allosteric enzyme regulation (Note, allosteric regulation may upregulate or downregulate enzyme activity.) An enzyme with quaternary structure whose activity is changed by the binding of modulators. Contrast the “lock-and-key” theory of enzyme-substrate binding with the “induced-fit” theory. lock-and-key theory A theory of enzyme specificity proposing that a substrate has a shape fitting that of the enzyme’s active site, as a key fits a lock. induced-fit theory A theory of enzyme action proposing that the conformation of an enzyme changes to accommodate an incoming substrate (enzyme conformations are not rigid) How would changing each of the following factors change enzyme activity/reaction rates: a. Enzyme concentration Availability of more enzyme molecules increases the reaction rate. a. Substrate concentration Increasing concentration of substrate will increase the reaction rate to a certain point. However, at a certain concentration, the enzyme becomes saturated with However, at a certain concentration, the enzyme becomes saturated with substrate, and the reaction cannot proceed any faster. This point is known as the maximum rate (Vmax). a. Temperature - Like any chemical reaction, reaction rates of enzyme-catalyzed reactions tend to increase with higher temperatures. However, remember that enzymes are proteins, and high temperatures can denature proteins. Thus, most enzymes have an optimum temperature at which enzyme activity is the highest. a. pH - Most enzymes have an optimum pH range at which enzyme activity is the highest. Often, optimum pH is near 7.4, the pH of most body fluids, but there are exceptions (eg., pepsin, an enzyme that catalyzes protein digestion in the stomach, has an optimum pH ~1.5). What is a zymogen? (zymogen or proenzyme)The inactive precursor of an enzyme. Self-study guide for Module 7 Nucleic Acids Ch.11 1. What is the principal location of DNA within human cells? DNA IS PRESENT IN HUMAN CELLS AS CHROMATIN. CHROMATIN is DNA and histones; histones are small structural proteins, chromatin condenses during cell division to form chromosomes!!! 2. Which pentose sugar is present in DNA? DEOXYRIBOSE 3. Which pentose sugar is present in RNA? RIBOSE 4. Indicate whether each of the following is a purine or a pyrimidine: a. Guanine = PURINE b. Thymine = PYRIMIDINE c. Uracil = PYRIMIDINE d. Cytosine = PYRIMIDINE d. Cytosine = PYRIMIDINE e. Adenine = PURINE 5. Which bases are found in DNA? ADENINE, CYTOSINE, GUANINE, THYMINE 6. Which bases are found in RNA? ADENINE, CYTOSINE, GUANINE, URACIL 7. What type of bonding is responsible for complementarybase pairing in a DNA double helix? The bases of DNA are joined by hydrogen bonds ***Individual nucleotides are joined together by PHOSPHODIESTERBONDS-- which join the 5' (5 prime) carbon of one nucelotide to the 3' (3 prime) carbon of the next nucleotide. 1. What is meant by “complementarybase pairing”? OCCURS SO THAT THE BASE PAIRS OF DNA ARE JOINED BY HYDROGEN BONDS ( ADENINE ALWAYS PAIRS WITH THYMINE AND GUANINE ALWAYS PAIRS WITH CYTOSINE. THUS THE TWO STRANDS ARE COMPLEMENTARYTO EACH OTHER) 2. What is a chromosome?A molecule of DNA tightly coiled around histone protein 3. What is a gene? Is a specific sequence of DNA on a chromosome;each gene directs the synthesis of a specific protein ***GENES ARE INSTRUCTIONS FOR MAKING PROTEINS*** 4. What is the function of the following enzymes in DNA replication? a. Helicase = replication begins when an enzyme called HELICASE catalyzes the unwinding- breaking of hydrogen bonds- of the double helix b. Ligase = a final step of DNA replication, the enzyme DNA ligase catalyzes the covalentjoining of Okazaki fragments to form a continuous strand c. DNA polymerase = an enzyme that catalyzes synthesis of a new DNA strand using a DNA template; several types of DNA polymeraseenzymes exist 5. What is a replication fork? The point where the double helix unwinds is called the replication fork!!! 6. Write the full name and briefly describe the functions of the 3 types of RNA: a. mRNA = messenger RNA = b. tRNA = transfer RNA = function is to transfer amino acids from the cytoplasmto the ribosomewhere they can be joined to form a polypeptide, tRNA has a clover leaf structure. One end is an amino acid and on the other end is a triplet of nucleotide bases called an ANTICODON that binds to a complementarycodon on the mRNA!!! c. rRNA = ribosomal RNA= codon by codon, the genetic message is translated as tRNA moleculesdeposit amino acids in the order prescribed. RIBOSOMAL ENZYMES JOIN THE AMINO ACIDS TO FORM A POLYPEPTIDECHAIN 7. What is a codon? Genetic instructions are written in DNA and RNA as a series of 3 nucleotide words called codons!!! 8. What is an anticodon = binds to a complementarycodon on the mRNA!!! 9. What is the difference between an intron and an exon? Introns are non-coding segments of DNA interrupting the coding sequences (exons) Think of introns as intervening sequences of nucleotides; exons are the sequences of DNA that are expressed. Introns may enable different kinds of cells to make different proteins from the same sequence of DNA. Introns are cut out, exons are joined together 10. Describe the basics of transcription and translation, including where in the cell each occurs. Genetic transcription is the transfer of informationfrom DNAs base sequence to the complementarybase sequence of an mRNA molecule.Transcription occurs in the nucleus. Then, the mRNA molecule movesto the cytoplasmwhere translation occurs. Translation step of protein synthesis takes the language of nucleic acids- nucleotide sequences - and translates it into the language of proteins- amino acid sequences. Translation takes place in the cytoplasmon organelles called ribosomes. ** TRANSCRIPTION (mRNA synthesis) = is the transfer of information from DNA's base sequenece to a complementarybase sequence of an mRNA molecule! **TRANSLATION:a cell translates genetic messageand builds a protein accordingly. The message is a series of codons on the mRNA molecule, and the translator is another type of RNA called TRANSFER RNA (tRNA) 1. Define the term nutrigenomics. An emerging area of nutritional science research is nutrigenomics!!!Nutrigenomics is the study of how different foods may interact with genes to either increase or decrease the risk of disease!!! 19. RNA - single strand, carries out instructions for protein synthesis 20. DNA= double strand, provides instructions for protein synthesis, DNA doesn’t synthesize proteins directly. Rather, RNA acts as a bridge between genetic informationand the polypeptide sequence of a protein. REMEMEMBERTHE FLOW OF INFORMATION= DNA TO RNA TO PROTEIN SYNTHESIS. The two major steps in this flow of genetic informationis 1. transcription 2. translation Self-study guide for Module 8 Digestion 21. List 2 important qualities of saliva. SALIVA CONTAINS SALIVARY AMYLASE, AN ENZYME THAT HYDROLYZESSTARCH** A small degree of chemical digestion occurs in the mouth. Saliva contains salivary amylase, an enzyme that hydrolyzes starch. Usually, starch isn’t in the mouth long enough for salivary amylase to do any more than break it down to smaller polysaccharides. Saliva contains lysozyme,antibodies, and other anti-microbial agents. Saliva also neutralizes acid in the mouth to help prevent dental caries. The water in saliva serves to moisten food, and slippery glycoproteinslubricate food making it easier to swallow. 22. Name the enzyme that begins protein digestion in the stomach. ***PEPSIN? The stomach is the first site of significant chemical digestion (the breaking of chemical bonds by hydrolysis reactions). As mentionedabove, two intricate systems regulate digestion and absorption – the endocrine system (via hormones)and the nervous system. Two large plexuses of nerves innervate the GI tract. Food in the stomachsignals release of the hormone gastrin from (G-cells of) the stomach mucosa. Gastrin stimulates parietal cells to secrete hydrochloric acid (HCL). Stretch receptors of enteric neurons respond to stimulate muscle contraction. So, food mixes with HCL allowing proteins to be denatured. Parietal cells also secrete intrinsic factor, a glycoprotein that will be important for B-12 absorption in the small intestine. Chief cells in the stomach secrete pepsinogen. Pepsinogen is a zymogen that is activated by HCL Chief cells in the stomach secrete pepsinogen. Pepsinogen is a zymogen that is activated by HCL to the active enzyme pepsin. Pepsin catalyzes the hydrolysis of peptide bonds. A small amount of gastric lipase is secreted from chief cells, but very little fat digestion occurs in the stomach. Churning of the stomachmixes the food, HCL, enzymes, and mucus together to form a creamy paste called chyme. The pyloric sphincter regulates the passage of chime from the stomach into the small intestine. A small amount of chyme (just a few milliliters with each persistaltic wave) enters the small intestine. 23. Identify the function of each of the following hormonesin digestion: a. Gastrin = Food in the stomachsignals release of the hormone gastrin from (G-cells of) the stomach mucosa. Gastrin stimulates parietal cells to secrete hydrochloric acid (HCL). a. Secretin= • Secretin is an intestinal hormone that is secreted in response to acid in the duodenum. Secretin signals the pancreas to release bicarbonate-rich fluid through the pancreatic duct. Bicarbonate (HCO3 ) helps neutralize the acidic chyme from the stomach. b. Cholecystokinin= • Cholecystokinin(CCK) is an intestinal hormonethat signals the gallbladder to release bile. CCK also signals the pancreas to secrete a variety of hydrolytic digestive enzymes. Pancreatic digestive enzymes include: 24. Name the biomoleculethat each of the following pancreatic enzymesacts on: a. Amylase - for STARCH digestion b. Lipase - for FAT digestion c. Trypsin - for PROTEIN digestion d. Nuclease - for NUCLEIC ACID digestion 25. Name the end products of digestion for each of the following macronutrients: a. Carbohydrate= MONOSACCHARIDES b. Protein=AMINOACIDS, DIPEPTIDES,TRIPEPTIDES c. Fat= ? 26. What is the role of bile salts in fat digestion? BILE SALTS EMULSIFY FAT IN THE SMALL INTESTINE 27. Define the following: a. Micelle = Tiny, water-soluble micelles are formed from bile salts, monoglycerides,and free fatty acids. By orienting hydrophobic portions to the inside and hydrophilic portions to the outside, micelles allow the end products of fat digestion to reach the intestinal mucosa for absorption. In the ileum, most bile salts are reabsorbed and returned to the liver to be recycled. b. c. Chylomicron= Chylomicrons are a type of lipoprotein. As the name suggests, lipoproteins are made of lipids and proteins. The hydrophilic protein portion surrounds the hydrophobic lipid portion thereby allowing lipid transport in the blood. 28. In what region of the small intestine does most absorption take place? Most chemical digestion and most absorption occur in the small intestine! Recall that the small intestine consists of 3 sections: THE DUODENUM,JEJUNUM, AND ILEUM 29. What is a “brush border” enzyme? Absorption of fat is a bit more complicated.At the brush border, free fatty acids and monoglycerides detach from micelles and enter intestinal epithelial cells. Inside intestinal epithelial cells, they reform triglyceride molecules. Inside intestinal epithelial cells, they reform triglyceride molecules. Then, triglycerides (along with cholesterol,fat soluble vitamins, and phospholipids) are packaged in particles called chylomicrons. Chylomicrons are a type of lipoprotein. As the name suggests, lipoproteins are made of lipids and proteins. The hydrophilic protein portion surrounds the hydrophobic lipid portion thereby allowing lipid transport in the blood. Unlike the end products of carbohydrate and protein digestion, chylomicronsdo not enter hepatic portal circulation. Rather, they are absorbed into lacteals, and they enter lymphatic circulation. Lymphatic vessels empty into venous circulation, so chylomicronsenter the bloodstream where they deliver fat to tissues. Enzymes of the brush border completedigestion of carbohydrate and protein: ○ Maltase, sucrase, and lactase ensure that the end products of CHO digestion are simple sugars. These monosaccharidesare absorbed across the intestinal epithelium into capillaries which empty into the hepatic portal vein for delivery to the liver. ○ Peptidases in the brush border completePRO digestion so that amino acids, dipeptides, and tripeptides are absorbed. Like CHO, they enter the hepatic portal vein to the liver. 30. Describe the importance of villi and microvilli. Absorption: To be used by cells, the end products of digestion must be absorbed from the GI tract and delivered to cells by the circulatorysystem. The small intestine, primarily the jejunum, is the principal site of absorption. The small intestine has a huge surface area for absorption. The anatomy of the intestinal mucosal layer makes this possible. Villi are the fingerlike projections of the small intestinal mucosa. Each villus is supplied by a capillary bed and a lacteal (a wide lymph capillary). Tiny projections of the plasma membranecalled microvilliform the brush border of the small intestine. 31. What are normal flora? Normal flora: • The undigested food material entering the large intestine could potentially present an overwhelming osmoticload to the large intestine. However,the large intestine is colonized by hundreds of species of microorganisms. These “good bacteria” that reside in large intestine are called normal flora. • Normal flora bacteria ferment certain types of fiber and resistant starches to form short chain fatty acids that nourish colonocytes. • The gut bacteria also synthesize some vitamins. An insignificant amount of B-vitamins(B-12, thiamin, riboflavin) and a significant amount of vitamin K that does get absorbed, but still insufficient to meet our needs. Module 9: Metabolism and Energy (ch 12.6-12.8; pages 345-356) 1. What is a metabolic pathway? A sequence of consecutivechemical reactions that convert a starting material into a product. METABOLIC PATHWAYS CAN BE EITHER ANABOLIC OR CATABOLIC 2. Contrast anabolism and catabolism? ANABOLISM= REACTIONS INVOLVED IN THE SYNTHESIS OF BIOMOLECULES CATABOLISM= REACTIONS INVOLVED IN THE BREAKDOWN OF BIOMOLECULES 3. What is the “commoncatabolic pathway”? The reactions of the citric acid cycle plus those of the electron transport chain and oxidative phosphorylation. 4. Contrast the amount of energy yielded from the oxidation of glucose vs. fatty acids. - On an equal-mass basis, lipids contain more than twice the energy of carbohydrates. The reason for this difference is that fatty acids are a more reduced form of fuel, with a number of —CH2— groups as plentiful sources of H atomsfor the energy-yielding oxidation process. Glucose, in contrast, is already partially oxidized, with an oxygen atom located on each carbon atom. - On the basis of equal numbers of carbons, lipids are nearly 25% more efficient than carbohydrates as energy-storagesystems. - Glucose (96 ATP molecules),fatty acid 120! 5. Describe the structure and function of ATP. ATP consists of adenosine bonded to ribose bonded to three phosphate groups. A large amount of chemical energy is stored in the phosphate bonds of ATP. Hydrolysis of the high energy phosphate bonds of ATP can release free energy that cells then use to carry out processes that require energy because remember that energy cannot be created or destroyed,but it can be changed from one form to another----THE FIRST LAW OF THERMODYNAMICS 6. Where is most ATP produced in the cell? Mitochondrion(for this reason the mitochondriaare called "POWERHOUSESOF THE CELL") the process of ATP synthesis in mitochondriais called CELLULAR RESPIRATION 7. Define each of the following, and identify which vitamin serves as a precursor for each: a. CoenzymeA = ACETYL CoA = Amino acids, monosaccharides,and fatty acids/glycerolgenerated from the breakdown of macronutrientscan be further degraded to the 2-C molecule acetyl CoA. Rememberthat vitamins often serve as precursors for important coenzymes.Coenzyme A is derived from the vitamin PANTOTHENIC ACID b. Nicotinamide adenine dinucleotide = COENZYME NAD+ = COENZYME CARRIER that transfers electrons and hydrogen ions. During the oxidation of a substrate, NAD+ accepts two electrons and one hydrogen ion, and in the process becomesREDUCED to NADH. Note that NAD+ is derived from the B-vitamin NIACIN c. Flavin adenine dinucleotide = COENZYME FAD = COENZYME CARRIER that transfers electrons and hydrogen ions. CoenzymeFAD is a major electroncarrier in the oxidation of fuel molecules!!!!!FAD accepts two electrons and two hydrogen atoms from a substrate, and in the process becomes REDUCED TO FADH2. Note that FAD is derived from the vitamin RIBOFLAVIN 8. Define the following: a. Energy balance = Energy balance is achieved when a person’s intake of energy from food equals energy expenditure. b. Positiveenergy balance Someonein positive energy balance is ingesting moreenergy than he/she expends. •We will see in future modules how that excess energy intake can be stored as body •We will see in future modules how that excess energy intake can be stored as body fat. c. Negative energy balance weight loss 9. What is REE, and how is REE assessed clinically? REE = resting energy expenditure 10. What is RQ? Respiratory quotient (RQ) RQ = the ratio of CO2 produced to O2 consumed = vCO2/vO2 Thus, an RQ of 1 indicates a person is metabolizing carbohydrate. Thus, an RQ of .7 indicates a person is metabolizing fat. Thus, an RQ > 1 would suggest lipogenesis (fat storage) and overfeeding.
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