Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
63 Cards in this Set
- Front
- Back
|
What are enzymes?
|
• Biological catalysts that speed up reactions without being consumes
• DO NOT shift equilibrium, just reach it faster! • Very specific • most are proteins |
|
|
Why does the body need enzymes?
|
• Nearly all reactions require enzymes
• Digestion and metablolism of carbs, fats, and proteins |
|
|
Why do foods need enzymes?
|
• tenderize meat, ripen or brown fruits, chill-proof beer
|
|
|
What is the difference between Cofactors and Coenzymes?
|
Cofactors:
• inorganic component needed to work • Minerals (Fe, Mg, Zn, Se) Coenzyme: • organic component needed to work • vitamins (Vit. B6, B12, thiamin, folate, ribflavin, biotin, niacin) |
|
|
What is the difference between an Apoenzyme and Holoenzyme?
|
Apoenzyme:
• protein part of enzyme only • missing cofactor/coenzyme Holoenzyme: • complete (active) enzyme • enzyme + cofactor/coenzyme |
|
|
What is Zymogen?
|
• enzyme precursor (inactive) that must be converted to active form
|
|
|
1) How do you recognize an inactive enzyme (Zymogen)?
2) How do you recognize an active enzyme (Holoenzyme)? |
1) Begins w/ pro- or ends in -gen
2) Ends in -in |
|
|
Naming enzymes is based on:
|
• What it reacts with
• How it reacts • ends in -ase |
|
|
Give two examples of naming enzymes
|
1) Lactase: enzyme that digests Lactose (milk sugar)
2) Alcohol Dehydrogenase: enzyme that removes hydrogen from alcohol to form an aldehyde |
|
|
What are the 6 enzyme classifications?
|
1. Oxidoreductase
2. Transferase 3. Hydrolase 4. Isomerase 5. Lyase 6. Ligase |
|
|
1) What is Osidoreductase?
2) What does it require? 3) Where are they found? |
1) Addition or removal of H
2) Requires coenzymes (NAD+ and FAD) • Dehydrogenase - remove H • Reductase - add H 3) • electron transport chain in mitochondria • Krebs cycle • AA metabolism |
|
|
What do NAD+ and FAD stand for?
|
NAD+ - Nicotinamide Adenine Dinucleotide
FAD - Flavin Adenine Dinucleotide *Note: you may want to look at their structures on p. 2 of this section |
|
|
1) What is Transferase?
2) Name 5 types 3) Where is it found? |
1) Transfers a functional group from one molecule to another: 2 reactants and 2 products
2) transketolase, transaldolase, transaminase, transmethylase, phosphotransferase 3) Krebs cycle, AA metabolism |
|
|
What is phosphotransferase?
|
Transfers phosphate group from ATP onto another group
|
|
|
1) What is Hydrolase?
2) Name four types 3) Where is it found? |
1) Causes hydrolysis reactions (water is a reactant), water breaks bonds
2) lipase, protease, phosphatase, amylase 3) • Digestive enzymes that digest lipids, carbs, proteins, etc • AA metabolism |
|
|
1) What is Isomerase?
2) Name 3 types 3) Give 3 examples |
1) Rearranges functional groups on one molecule (one reactant and one product)
2) Racemase, epimerase, mutase 3) Glycolysis, Krebs Cycle, AA metabolism |
|
|
In glycolysis what does Phoshohexose isomerase do?
|
Converts glu-6-phosphate to fru-6-phosphate
|
|
|
1) What is Lyase?
2) Name 3 types 3) Where do they take place? |
1) Cleaves (breaks) C-C, C-S, or C-N bonds (excluding peptide bonds)
2) • Decarboxylase (COO- --> CO2) • Aldoase • Deaminase (removes amine from AA) 3) Krebs cycle, fatty acid degradation, AA metabolism |
|
|
1) What is Ligase?
2) Name 2 types 3) Where do they take place? 4) How do you recognize this reaction? |
1) Joins bond between C and another element (O, S, N) and require ATP!
2) Carboxylases (add CO2 onto molecule) and synthetases 3) Fatty acid synthesis, Krebs cycle, AA metabolism 4) Pi (inorganic phosphate) in the reaction |
|
|
How do you recognize each of the following reactions?
1. Oxidoreductase 2. Transferase 3. Isomerase 4. Hydrolase 5. Lyase 6. Ligase |
1. Removal/addition of H or O (NAD+ or FAD)
2. Transfer of group from one molecule to another (2 reactants and 2 products) 3. Structural rearrangement (1 reactant, 1 product) 4. Water breaks bonds (water is a reactant) 5. Break bond without water or redox (C-C, C-N, C-S) 6. Make bond (uses ATP), Pi |
|
|
Which enzyme catalyzes this reaction:
glucose + ATP --> ADP + Glucose - 6 - phosphate |
Transferase
|
|
|
Which enzyme class catalyzes this reaction:
Pyruvate + ATP + HCO3- --> ADP + Pi + Oxaloacetate |
Ligase
|
|
|
1. How do enzymes work?
2. Show a generic reaction illustrating this. |
1. Enzymes contain an active site that reacts with a specific substrate.
2. E + S <-> ES <-> EP <-> E + P (ES <-> EP is the complex) |
|
|
What is the specificity based on?
|
Functional group, optical isomer, bond, and cofactors
|
|
|
What are the two types of active sites?
|
1. Binding site - holds substrate in a proper place (weak, non-covalent interactions b/t AA & substrate [LDF, dip-dip, ion-dip, H-bond most common])
2. Catalytic site - where reaction actually occurs |
|
|
What are the 2 active site models?
|
1. Lock and key model (not very common)
2. Induced-fit Model (most common) - more than one substrate can fit into the enzyme b/c they have flexible active sites |
|
|
What is a:
1. Transition State 2. Activation Energy |
1. The place where the reaction takes place
2. The amount of energy it takes for a reaction to occur |
|
|
Do catalyzed reactions increase or reduce the energy required for a reaction to take place?
|
Reduce
|
|
|
1. Reaction velocity (Vo)
2. Maximum Velocity (Vmax) 3. Michaelis constant (Km) |
1. Number of reactions catalyzed by enzyme per second
2. Enzyme is completely saturated with substrate • the larger the better 3. Affinity for binding (least amount needed for the reaction to happen) • amount of substrate required for 50% of enzyme to be bound • 1/2Vmax or 1/2 saturation • the smaller the better • 50% bound to substrate, 50% not = 1/2 efficient |
|
|
What is the reaction velocity (Vo) dependent on:
1. [S] >> Km (leveling off near the Vmax) 2. [S] > Km (between Vmax and 1/2 Vmax) 3. [S] << Km |
1. Vo is dependent on [E]
• enzyme is saturated with S • as [E] increases the amount of product increases 2. Vo is dependent on [E] and [S] • not completely saturated • as [E] & [S] increase so does the amount of product 3. Vo is dependent on [S] • as [S] increases so does the product |
|
|
1. Smaller Km =
2. Larger Km = 3. Which is better? |
1. high affinity to bind S (less [S] needed to reach 1/2 saturation
2. low affinity to bind S (more [S] needed to reach 1/2 saturation 3. Smaller Km b/c less substrate is needed to reach 1/2 saturation |
|
|
What is a Lineweaver-Burke plot?
|
Double recipricle plot:
• 1/[S] • 1/Vo • -1/Km • 1/Vmax • Slope = Km/Vmax |
|
|
On a Lineweave-Burke Plot, as you approach the origin does the Km and the Vmax get bigger or smaller?
|
Gets bigger
|
|
|
On a bell curve where is the optimum?
|
The highest point on the bell curve
|
|
|
On a Lineweaver-Burke Plot:
1. Where is the Vmax and how do you find it? 2. Where is the Km and how do you find it? |
1. x = 0, solve for y and take the reciprical = Vmax
2. y = 0, solve for x and take the negative reciprical = Km |
|
|
Find the:
1. Vmax 2. Km using this equation: y = 2x +4 |
1. 0.25
2. 0.5 |
|
|
What factors affect enzyme activity?
|
1. Temperature
2. pH 3. Enzyme and substrate concentrations 4. Cofactors/Coenzymes 5. Effectors |
|
|
1. How does temperature affect enzyme activity?
2. Where is the peak activity? |
1. As the temperature increases so does the rate of enzyme catalyzed reaction
• rate doubles every 10 C increase • denatures enzyme 2. Peak activity at the optimal temperature |
|
|
What does protein denaturation cause?
|
Loss of structure and funcion
|
|
|
How does pH affect enzyme activity?
|
Each enzyme has an optimum pH. This is where it will reach its peak activity.
|
|
|
What happens to the enzymes in raw foods (not cooked above 116 F) when they reach the stomach?
|
Our body is not able to denature them resulting in a nutritional deficiency in: calcium, Vitamin D, Iron, Vitamin B12, Protein, Calories
|
|
|
How do enzyme and substrate concentrations affect enzyme activity?
|
If there is excess substrate the velocity of the reaction depends on [E].
|
|
|
How do Cofactors and Coenzymes affect enzyme activity?
|
Vitamin or mineral deficiencies will decrease enzyme activity.
|
|
|
What affect do effectors have on enzyme activity?
|
• Activators increase activity
• Inhibitors decrease activity |
|
|
What is an inhibitor?
|
Anything that decreases enzyme activity!
|
|
|
How does a competitive inhibitor affect the reaction of an enzyme and a substrate?
|
The substrate (S) and the competitive inhibitor (I) compete for the same active site. If the substrate binds to the enzyme there is a product. If the competitive inhibitor binds to the enzyme no product is made.
|
|
|
Compare and contrast how Competitive and Noncompetitive inhibitors affect enzymes.
|
1. Competivitve
• If the enzyme binds to the inhibitor no product is formed • Vmax - no change • Km - larger (less affinity for binding) 2. Noncompetitive Inhibitor: • The enzyme can bind to the substrate and then the inhibitor, or to the inhibitor and then to the substrate • Substrate binds to active site • Inhibitor binds to allosteric site • Vmax decreases (reducing the potential for product to be made) • Km - doesn't change |
|
|
Why doesn't the Vmax change with the presence of a competitive inhibitor?
|
The effect of the competitive inhibitor can be overcome with the addition of more substrate. The product can be produced, but it will happen slower.
|
|
|
Why does the Vmax decrease with the presence of a noncompetitive inhibitor?
|
The noncompetitive inhibitor can't be overcome with the addition of more substrate. It reduces the potential for product to be made.
|
|
|
If the Vmax doesn't change, and the Km increases, what type of inhibitor is present?
|
Competitive Inhibitor
|
|
|
If the Vmax decreases, and the Km doesn't change, what type of inhibitor is present?
|
Noncompetitive Inhibitor
|
|
|
What are the 3 types of enzyme regulation?
|
1. Covalent Modification
2. Modulation of ALLOSTERIC enzymes 3. Enzyme induction (increasing enzyme concentration) |
|
|
What is an allosteric site?
|
The site other than the active site
|
|
|
What is the primary way to regulate cellular enzymes?
|
Covalent Modification
|
|
|
How does covalent modification work?
|
1. Adding or removing a phosphate group can turn the enzyme on or off (E dependent)
2. Very fast |
|
|
Which increases activity and which decreases activity:
1. Phosphorylation of glycogen phosphorylase 2. Phosphorylation of glycogen synthase |
1. Increases activity
2. Decreases activity |
|
|
Allosteric Enzymes are:
|
1. Rate-limiting (slows it down)
2. Activator or inhibitor binds to an allosteric site on the enzyme 3. Feedback inhibition: build up of product turns off allosteric enzyme |
|
|
1. What is enzyme induction?
2. What is the rate determined by? 3. What does it occur from? 4. Is it fast or slow? 5. e.g. |
1. Cells regulate the amount of enzymes by induction
2. Rate dictated by cellular circumstances 3. Hormones and diet 4. Very slow 5. Insulin - stimulates an increase in enzymes needed to metabolize glucose |
|
|
In the following reaction, which would be the most functional after a high carbohydrate meal:
Glucose + ATP --> ADP + Glucose - 6 - phosphate (stimulates glycogen synthesis [carb storage] in muscles and liver 1. Hexokinase: • Found in muscles • Km = 1.5 mM • Allosterically inhibited by glu-6-P OR 2. Glucokinase: • found in liver • Km = 20 mM • induced by insulin |
Glucokinase b/c the Km is larger meaning that you need a larger amount of glucose, which you would have after a meal high in carbohydrates.
|
|
|
In the following reaction, which would be the most functional between high carbohydrate meals:
Glucose + ATP --> ADP + Glucose - 6 - phosphate (stimulates glycogen synthesis [carb storage] in muscles and liver 1. Hexokinase: • Found in muscles • Km = 1.5 mM • Allosterically inhibited by glu-6-P OR 2. Glucokinase: • found in liver • Km = 20 mM • induced by insulin |
Hexokinase, the Km is smaller meaning that you need less glucose which you would have in between meals.
|
|
|
Enzymes that utilize coenzymes that are reversibly oxidized and reduced are in what class of enzymes?
|
Oxidoreductases
|
|
|
Which type of enzyme would catalyze the following reaction:
Tripeptide + 2H20 --> 3AA |
Hydrolases
|
|
|
Which is tru when [S] > Km?
a. velocity is 1/2 Vmax b. velocity is directly proportional to [S] c. velocity depends on [S] and [E] d. velocity is near Vmax |
c. Velocity depends on [S] and [E]
|
