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APHY 201 Exam 1c
Ch. 4 Enzymes and Energy
| Question | Answer |
|---|---|
| hydrolases function | promote hydrolysis reactions |
| phosphatases function | catalyze the removal of phosphate groups |
| synthases and synthetases function | catalyze dehydration synthesis reactions |
| dehydrogenases function | remove hydrogen atoms from their substrates |
| kinases function | add phosphate group to phosphorylate particular molecules |
| isomerases function | rearrange atoms within their substrate molecules to form structural isomers such as glucose and fructose |
| what are the 4 notable roles/properties of enzymes? | enzymes are biological catalysts that increase the rate of a reaction; they are not changed by the reaction and can be used again; they don't change the nature of the reaction, and they lower the activation energy of the reaction |
| true or false, catalysts/enzymes help the reaction occur by raising the heat | false, catalysts help the reaction occur at lower temperatures. heat has some negative effects on cells |
| do exergonic reactions release more energy in a catalyzed state or noncatalyzed state? | neither, they both release the same amount (!) |
| what is the name of the enzyme model where the substrates/reactants fit exactly into the active site of the enzyme? | lock-and-key model |
| what is the name of the enzyme model where the initial fit of substrates is not exact in the active site, but the fit will change as the substrate moves into the active site? | induced-fit model |
| when a substrate binds to the active site of an enzyme, it forms what? (hint: these weaken the original bonds of the substrate and allow them to break easily) | temporary bonds |
| true or false, the enzyme-substrate is temporary and breaks to yield the products of the reaction | true |
| how can the amount of enzyme in a sample of fluid be measured? (recognize for multiple choice) | the amount of enzyme in a sample of fluid can be measured based on the rate of product synthesis. the more enzyme present, the faster the product is formed |
| what is the term for different forms of an enzyme that catalyze the same biochemical reaction but differ slightly (especially in location/ different tissues in the body)? | isoenzymes |
| what enzyme abnormality level is associated with obstructive jaundice, Paget's disease (osteitis deformans), and carcinoma of bone? | alkaline phosphatase |
| what enzyme abnormality level is associated with benign hypertrophy of the prostate/ cancer of the prostate? | acid phosphatase |
| what enzyme abnormality level is associated with pancreatitis and perforated peptic ulcer? | amylase (!) |
| what enzyme abnormality level is associated with muscular dystrophy? | aldolase |
| (starred) what enzyme abnormality level is associated with muscular dystrophy, myocardial infarction? | creatine kinase (CK) or creatine phosphokinase (CPK). CK-1 / CK-BB, CK-3 / CK-MM, CK-2 or CKMB (the last of which can confirm a heart attack) |
| what enzyme abnormality level is associated with myocardial infarction, liver disease, renal disease, pernicious anemia? | lactate dehydrogenase (LDH), different isoenzymes of which can indicate which organ tissue is being affected |
| what enzyme abnormality level is associated with myocardial infarction, hepatitis, muscular dystrophy? | transaminases (AST in several organs, and ALT in liver) |
| what are 5 factors that influence enzyme activity? | temperature, pH, concentration of cofactors/coenzymes, concentration of enzyme & substrate, possible stimulatory or inhibitory effects of products on enzyme function |
| in what 2 ways can pH influence enzyme activity? | acidity -- too much acidity inhibits enzyme activity; also, different enzymes differ in their optimal pH number |
| pH optimum reflects the pH of the fluid in the LOCATION in which the enzyme is found. where are pepsin, salivary amylase, and trypsin found, and what does that have to do with their pH? | pepsin is found in the acidic stomach (pH of 2), salivary amylase is found in the saliva at the mouth (rel. neutral pH), and trypsin is found in the alkaline small intestine (pH of 9 or so) |
| most enzymes need additional small molecules to aid in a reaction. what are the ORGANIC molecules derived from water-soluble vitamins? | coenzymes |
| NAD and FAD are well-known electron and hydrogen atom carriers. they are also coenzymes (organic small molecules...). from what are they derived? | NAD derived from niacin (vitamin B3) and FAD derived from riboflavin (vitamin B2)! |
| you should associate cofactors with conformational change of the enzyme or help in enzyme-substrate binding. what are some common cofactors? | metal ions such as Ca2+, Mg2+, Mn2+, Cu2+, Zn2+ |
| pepsinogen is the inactive form of pepsin. what is the term for the inactive form of an enzyme like this? | zymogen |
| if active pepsin were produced directly inside the cells that make it, the enzyme would destroy cells and tissues before it reached the food. how is pepsinogen activated? | when it mixes with the highly acidic hydrochloric acid in the stomach lumen |
| true or false, zymogens often require additional enzymes to de-/phosphorylate themselves | true |
| the maximum number of substrate molecules a single enzyme active site can convert into product per second | enzyme turnover (Kcat) |
| will increasing substrate concentration to a reaction forever increase the rate of the reaction? why? | no, because the enzyme will become saturated (every enzyme in the solution is being used) |
| what is the term for when a single enzyme can drive a reaction in two directions, depending on the concentrations of substrate/product, and when one side gets higher, the other reaction reverses? | law of mass action |
| what is the classic example of the law of mass action (hint: an enzyme within a bigger equation)? | carbonic anhydrase in the bicarbonate buffer equation (H2O + CO2 <carbonic anhydrase> <--> H2CO3 <--> HCO3- + H+ |
| what is the term for how most reactions are linked together in a chain (or web)? | reactions that begin with an initial substrate and end with a final product are linked together via a chain or web called a metabolic pathway, which can be endergonic or exergonic, etc |
| true or false, most metabolic pathways are branched | true |
| metabolic pathways' branching points are often inhibited by a form of negative feedback called what? | end product inhibition or feedback inhibition |
| how is end product inhibition/ feedback inhibition characterized? (hint: different from competitive inhibition) | feedback inhibition uses allosteric inhibition, such as ATP binding to PFK-1 in glycolysis - ATP binds to a location away from the enzyme's active site so that the enzyme can't bind its substrates properly |
| what is the benefit of end product inhibition via allosteric inhibition? | keeps the final product from accumulating and prevents toxic or inefficient buildup |
| when do inborn errors of metabolism occur? | when there is a mutation in a single gene that codes for an enzyme in a metabolic pathway---products to be formed after this enzyme in the chain are NOT formed and diseases often occur |
| what 3 ways do inborn errors of metabolism occur? | due to loss of end product; due to accumulation of intermediary products (those before the bad enzyme); due to accumulation of alternative products in a branch |
| (starred) which disease is an amino acid metabolic defect and displays intellectual disability and epilepsy as a result of an increase in phenylpyruvic acid? | phenylketonuria, an autosomal recessive disease that occurs because of deficit of enzyme phenylalanine hydroxylase (PAH), which normally converts the AA phenylalanine into tyrosine |
| (starred) which disease is an amino acid metabolic defect and results in susceptibility to skin cancer due to a lack of the amino acid derivative, melanin? | albinism, an autosomal recessive disease that occurs because of deficit of enzyme tyrosinase, required to convert AA tyrosine into melanin |
| (starred) which disease is a carbohydrate metabolic defect and presents with diarrhea/flatulence due to lack of lactose utilization? | lactose intolerance, which occurs because of a lack of digestive enzyme lactase in the small intestine |
| (starred) which disease is a lipid metabolic defect and presents with brain degeneration and death by age 5 due to lipid accumulation (ganglioside GM2)? | Tay-Sach's disease, an autosomal recessive disease that occurs because of deficit or absence of beta-hexosaminidase A (Hex-A), which is usually found in the lysosomes of nerve cells--it supposed to break down GM2 ganglioside |
| (starred) which disease is a lipid metabolic defect and presents with atherosclerosis of coronary arteries and large arteries due to high blood cholesterol? | hypercholesterolemia, an autosomal dominant disease, in 90% of cases caused by gene mutations affecting clearance of LDL--it impairs the LDLR protein, which acts like a sponge to pull LDL-C out of the blood |
| what is the term for the flow of energy in living systems? | bioenergetics |
| what is the first law of thermodynamics? | energy cannot be destroyed or created, only transformed (some energy is lost during the conversion!) |
| what is the second law of thermodynamics? | energy always spreads out, lost with each transformation as heat, moving from concentrated and ordered to dispersed and chaotic. systems naturally progress toward disorder over time, and energy becomes less usable/ less free energy is available to do work |
| does entropy increase or decrease at each step of energy transformation? | increase, because entropy has to do with degree of disorganization (know endergonic and exergonic in relation to this) |
| true or false, the production of ATP is actually an endergonic reaction coupled to an exergonic reaction to drive it | true, energy from food is broken down in exergonic reactions to drive the endergonic reactions in our bodies |
| true or false, redox reactions are always coupled | true, and many molecules can be both oxidizing agents and reducing agents in a chain reaction where electrons are passed along |
| what are the full names of the hydrogen carrier molecules that come from vitamin B2 and B3? | from B3: NAD = nicotinamide adenine dinucleotide; from B2: FAD = flavin adenine dinucleotide |
| what are the coenzymes that play an important role in hydrogen transfer? | NAD and FAD |
| true or false, FAD can accept 2 electrons and bind to 2 protons--more than NAD--but cellular respiration gets more energy from NAD | true |
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