Chapter 4 Study Guide Flashcards
Give a definition of “enzymes” What does the term mean in Greek?
Greek for “in yeast”. Enzymes are biological catalysts that increase the rate of chemical reactions. They are specific, easily denatured, and competitive.
Enzymes are made up of___________?
Enzymes are made of proteins. The only exception are a few special cases in which RNA demonstrates enzymatic activity, these are called ribosomes.
Complete the following phrase: One Gene, one__________.
Polypeptide
What is “activation energy”? How do enzymes speed up the rate of a reaction?
Activation energy is the amount of energy required for a reaction to proceed. Enzymes lower the activation energy of a reaction, which increases the rate of the reaction.
What does the term “conformation” mean?
Conformation means the shape of a molecule, enzyme, structure, etc.
What are reactants? Products? Substrates?
Reactants: subtrates in enzymes.
Products: Are released after the enzyme dissociates, this also yields free energy.
Substrates: reactant molecules of the enzyme.
What is the “active site”?
Are particular pockets that are active in catalyzing a reaction located on the enzyme.
In the naming of enzymes, we have their name end in:________.
~ase.
The only exceptions are: pepsin, trypsin, and rennin.
Most enzymes have a double worded name. The first word tells you ________& the second word names the_____________.
First tells u the substrate and second tells you the action
What are “isoenzymes”?
Isoenzymes are different models of the same enzyme, found in different locations of the body. Very useful in the diagnosis of a disease.
How is the presence of some enzymes in the plasma of use to us?
In clinical test, abnormally high plasma concentrations of a particular enzymes (think SGPT) are characteristic of certain diseases. (See Clinical on 92)
What did I have to say about the title of this section?
This section should be title things that influence enzyme activity. These are: 1. Temp and ph, concentration of cofactors and coenzymes 2. concentration of enzyme and substrate molecules in the solution and 3. the stimulatory and inhibitory effect of some products of enzymes action on the activity of the enzymes that helps to form these products.
How do both pH and temperature influence enzyme activity?
An increase in any of these influencers with increase the rate of nonenzyme-catalyzed and enzyme-catalyzed reactions.
What does pH optimum mean?
Each enzyme characteristically exhibits peak activity in a very narrow pH range, which is known as the pH optimum. If the pH is changes so that it is no longer within the enzyme’s optimum range, the reaction rate will decrease.
Over what pH range is trypsin effective?
Trypsin is effective between the 5 to 10 range, the pH optimum is 9.5
Pepsin is effective between the 1 to 6 range, the pH optimum is 2.
See Table 4.3 on 94
What are cofactors and what do they do?
Cofactors are necessary for the enzymes to have the proper shape. They assist with the conformation of the enzyme. All cofactors are metallic ions with plus 2 charges. (Ca, Mg, Mn, Cu, Zn, and Se (selenium)).
What are coenzymes and what do you do?
Coenzymes are organic molecules derived from water-soluble vitamins, such as niacin and riboflavin (mainly B vitamins).
In what ways might an enzyme be activated?
Activation of an Enzyme
-Remove excess amino acids
-Phosphorylate
-Dephosphoryation
Deactivation of an Enzyme
-Remove amino acid
-Dephoshorylation
-Phosphorylate
- destroy
Control gene expression
End product modulationBe able to explain what metabolic pathways are.
A sequence of enzymatic reactions that begins with an initial substrate, progress through a number of intermediates, and end with a final product. There are two types, linear and branched.
See Fig 4.7, 4.8. (A is Initial Substrate, B-E is Intermediates, F is the Final Product. The First Arrow at A is Enz 1, B to C is Enz 2, C to D is Enz3, D to E is Enz4, E to F is Enz5.)
A → B → C → D → E → F
Why would one branch of a pathway be more active than another?
Pathways keep Moving Forward because of
- Law of Mass Action - 2nd Law of Thermodynamics - Enzyme Specificity
Be able to explain “End Product Inhibition”
See fig 4.9 and 4.10.
End Product Inhibition is the regulation system of the branch points of metabolic pathways. This inhibition prevents that final product from accumulating excessively and results in a shift toward the final product of the alternate pathway.
How does this process work? That is, what is the mechanism of end Product Inhibition?
The mechanism by which the final product inhibits an earlier enzymatic step in its pathway is known as allosteric inhibition.
What does “Allosteric Modulation” mean?
THE MECHANISIM BY WHICH A FINAL PRODUCT INHIBITS AN EARLIER ENZAMITC STEP. An allosteric inhibitor combines with a part of the enzyme at a location other than the active site. This causes the active site to change shape so that it can no longer combine properly with its substrate.
Understand the process and significance of “inborn errors of metabolism”.
This type of disease, the quantity of intermediates formed prior to the defective enzymatic step formed after the defective step decreases. If the defective enzyme is active at the step that follows a branch point in a pathway, the intermediates and final products of the alternate pathway will increase. An abnormal increase in the production of these products can be the cause of some metabolic diseases. Diseases like albinism, PKU.
Explain the 1st and 2nd Laws of Thermodynamics.
Law 1: Energy can neither be created nor destroyed, however , it can be converted from one form to another. (e.g. light in a light bulb). This is known as the conservation of energy.
Law 2: When you convert energy from one form to another there is never a 100% transfer, you will always loose some as heat (e.g. light bulb being hot…lumens).
Endergonic anabolism.
Endergonic: A type of anabolism reaction that requires an input of energy (heat). In these reactions products must contain more free energy than the reactants.
A + B → C
Explain the “Law of Mass Action”.
The Law of Mass Action states that reversible reaction will be driven from the side of the equation where the lower is.
3 reasons metabolic pathways go forward
Law of mass action
2nd law of thermodynamics
Enzyme specificity
Enzyme activation
How cells control activity
Enzyme properties
Specificity
Competition
Saturation
Hydrolase
Promotes hydrolysis
Phosphatase
Catalyzes the removal of phosphate group
Synthases & synthetase
Catalyze dehydration a synthesis reactions
Dehydrogenase
Removes hydrogen atoms from their substrates
What are NAD+, NADH, FAD+, FADH2? What is their use?
NAD = Nicotinamide Adenine Dinucleotide - derived from the vitamin niacin (Vitamin B3). This is the Oxidized state. NADH,H, is the reduced state. (NAD + 2H → NADH,H.
FAD = Flavin Adenine Dinucleotide – which is derived from the vitamin riboflavin (Vitamin B2). This is the Oxidized state. FADH,H is the reduced state. (FAD + 2H → FADH,H.
These molecules are coenzymes that function as hydrogen carriers because they accept hydrogen (reduction) in one enzyme reaction and donate hydrogen (oxidation) in a different enzyme reaction.
Kinase
Add phosphate group to particular molecules
What is “Free Energy”?
Free energy means the available/potential energy in a molecule.
exergonic
Exergonic: A type of catabolist reaction that must release energy as they proceed. The reactions that convert molecules with more free energy to molecules with less.
C → A + B
oxidation
Oxidation: Removal of electons or hydrogen, by removing energy
reduction
Reduction: adding of electrons or hydrogen, adding of energy.
catabolism,
Catabolism: (Greek kata = downward + ballein = to throw) is the set of metabolic pathways that breaks down molecules into smaller units and release energy. Large molecules are (e.g. proteins, lipids) are broken down into smaller units (e.g. fatty acids, amino acids
anabolism.
Anabolism: (from Greek ana, “upward”, and ballein, “to throw”) is the set of metabolic pathways that construct molecules from smaller units. These reactions require energy.
Catalysts
Increases the rate of reaction
Is not changed at the end of the reaction
Does not change the nature of the reaction or final result and
Makes the reaction go faster at lower temps by lowering the activation energy
Enzymes are
Specific
Saturated
Competitive
Easily Denatured
What do the following enzymes do? Hydrolases. Phosphatases. Synthetases. Kinases & Dehydrogenases.
Hydrolases: promote hydrolysis reactions.
Phosphatases: catalyze the removal of phosphate groups.
Synthetases: catalyze dehydration synthesis reactions.
Dehyodrenases: remove hydrogen atoms from their substrates
Kinases: Add a phosphate group to particular molecules. (phosphorlation)
Isomerases: rearrange atoms within their substrate molecules to form structural isomers like glucose and fructose.
Ligands
(smaller molecules) serve as intracelluar regulators that are called second messengers.
Saturated
When the relationship between concentration & reaction rate reaches a plateau of maximum velocity. (pg 94, Fig 4.6)
Phosphorlation/Dephosphorlation
The activation/inactivation of a protein kinase is achieved by this process.
Entropy
the degree of disorganization of a system’s total energy
Bioenergetics
flow of energy in living systems
Coupled
Energy-liberating (exergonic) reactions are “coupled” to energy-receiving (endogoneric) reactions.
ATP
Adenosine Triphosphate
ADP
Adenosine Diphosphate
Reducing Agent
Atom or molecule that donates an electron to another
Oxidozing Agent
Atom or molecule that accepts electrons from another.
