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MMBIO240 Ch 3 EVANS
Chapter 3
67
Microbiology
Undergraduate 1
01/26/2011

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Term
Hypervariable region
Definition
is a location within nuclear DNA or the D-loop of mitochondrial DNA in which base pairs of nucleotides repeat (in the case of nuclear DNA) or have substitutions (in the case of mitochondrial DNA). Changes or repeats in the hypervariable region are highly polymorphic
Term
Immunoglobulin G (IgG)
Definition
are antibody molecules composed of four peptide chains-two heavy Y chains and two light chains. Each IgG has two antigen binding sites. IgG is considered the monomer. Involved in secondary immune response.
Term
Cooperativity
Definition
is a phenomenon displayed by enzymes or receptors that have multiple binding sites where the affinity of the binding sites for a ligand is increased positive cooperativity, or decreased, negative cooperativity, upon the binding of a ligand to its binding site.
Term
Amphipathic
Definition
describes a chemical compound that is both hydrophilic, and lipohilic (fat loving) Soaps and detergents are examples.
Term
In terms of what type of polymer it is, myoglobin is a
Definition
monomer
Term
In terms of what type of polymer it is, Hemoglobin is a
Definition
Heterotetramer with two alpha subunits and two beta subunits.
Term
The oxygen binding curve for myoglobin is____.
Definition
hyperbolic
Term
The oxygen binding curve for hemoglobin is______
Definition
Sigmodal
Term
A sigmoidal oxygen binding curve indicates what?
Definition
cooperative binding
Term
Cooperative binding is
Definition
Term
Allosteric regulation is
Definition
the regulation of an enzyme or other protein by binding an effector molecule at the protein's allosteric site (that is a site other than the protein's active site)
Term
True or False. Proteins can have domain structures that may behave independently or exhibit degrees of interaction.
Definition
true
Term
Describe IgG in terms of what type of polymer it is
Definition
IgG is a tetramer with two identical light chains and two identical heavy chains.
Term
True or False. Only heavy chains have variable and constant regions.
Definition
False, both the Light chains and heavy chains have variable and constant regions.
Term
In IgG how many hypervariable regions are within the variable regions?
Definition
three
Term
How does the constant and variable regions fold
Definition
As separate domains
Term
Enzymes do what
Definition
they catalyze reactions that take place in a cell
Term
Enzyme activity can be measured by?
Definition
the rate of product formation or substrate breakdown.
Term
Enzymes speed up a reaction by ____ the activation energy but not the ______ ______ ______ change.
Definition
lowering, overall free energy
Term
True or false-Enzymes do not change equilibrium
Definition
true
Term
Activation energy can also be lowered by...
Definition
-stabilizing the transition state,
-straining the susceptible bond to make it easier to break,
-holding substrates in close proximity and proper orientation
-forming a covalent bond with a reactant that destabilizes another bond
- acting as a proton donor or acceptor
Term
The Michaelis constant (Km) is...
Definition
the substrate concentration required to achieve 1/2 Vmax and provides a measure of the affinity of the enzyme for substrate
Term
Vmax is observed when...
Definition
all enzyme molecules are in the ES complex
Term
ES complex=
Definition
Enzyme Substrate complex
Term
A high Km indicates... a low Km indicates...
Definition
weak affinity... strong affinity
Term
What are the two generally accepted mechanisms for enzyme substrate binding.?
Definition
1. Lock and Key-the active site shape is similar to the substrate shape.
2. Induced Fit- the active site changes shape after substrate binding to fit the substrate
Term
Metabolic pathways are often controlled at...
Definition
a few key committed steps, usually at a branch point
Term
Regulatory enzymes exhibit _____ kinetics and are influence by ______ effectors.
Definition
Sigmoidal kinetics, allosteric
Term
Positive effectors of enzyme activity ____ the Km, _____ Vmax, or both
Definition
lower, increase
Term
Negative Effectors of enzyme activity ____ the Km, ____ the Vmax, or both.
Definition
increase, decrease
Term
The _________ transmits information (signals) across the cell membrane
Definition
the G protein signal system
Term
Proteins can function as...
Definition
in structure, as ligands, receptors, membrane transporters, molecular motors, antibodies, and/or enzymes
Term
What are the two components of the G protein signal system?
Definition
-A G protein coupled receptor that responds to external signals,
- a G protein complex that transfers the signal from the receptor to an intracellular molecule or complex
Term
In an enzyme activity assay what happens?
Definition
Substrate is added to the enzyme sample and either the amount of product produced or the amount of substrate depleted is measured.
Term
Induced fit mechanism
Definition
the active site changes shape after substrate binding to fit the substrate
Term
Domain
Definition
Term
Effector
Definition
is a molecule that binds to a protein and thereby alters the activity of that protein. A modulator molecule binds to a regulatory site during allosteric modulation and allosterically modulates the shape of the protein. Can also be a protein that is secreted from a pathogen that alters the pathogen’s host organism to enable infection.
Term
Lock and key mechanism
Definition
enzymes and the substrate possess specific complementary geometric shapes that fit exactly into one another. Since enzymes are flexible stuctures the active site is continually reshaped by interactions with the substrate as the substrate interacts with the enzyme.
Term
Michaelis- Menton constant (Km)
Definition
describes the rates of irreversible enzymatic reactions by relating reaction rate to the concentration of the substrate.
Term
Turnover number (Kcat)
Definition
- is defined as the maximum number of molecules that an enzyme can convert to produce per catalytic site per unit of time and can be calculated as follows : Kcat=Vmax/[E]t
Term
Polyclonal antibody
Definition
(or antisera) are antibodies that are obtained from different B cell resources. They are a combination of immunoglobulin molecules secreted against a specific antigen, each identifying a different epitope.
Term
Polyclonal antibody
Definition
(or antisera) are antibodies that are obtained from different B cell resources. They are a combination of immunoglobulin molecules secreted against a specific antigen, each identifying a different epitope.
Term
G protein
Definition
(guanine nucleotide binding proteins) are a family of proteins involved in transmitting chemical signals outside the cell, and causing changes inside the cell. They communicate signals from many hormones, neurotransmitters and other signaling factors.
Term
Sigmoidal curve
Definition
a logistic function or logistic curve. It can model the S shaped curve.
Term
G protein- coupled receptors
Definition
(also known as seven transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptor and G protein- linked receptors) comprise a large protein family of transmembrane receptors that sense molecules outside the cell and activate inside signal transduction pathways and ultimately cellular responses. (Only in eukaryotes)
Term
Substrate
Definition
is a molecule upon which an enzyme acts. Substrate binds with the enzyme active site and an enzyme substrate complex is formed. The substrate is transformed into one or more products, which are then released from the active site.
Term
G protein signal system
Definition
Term
Transition state
Definition
Term
Heavy chain
Definition
Term
Variable region
Definition
Term
Globular protein
Definition
are one of the two main protein classes, comprising globe like poteins that are more or less soluble in aqueous solutions.
Term
Specific activity
Definition
in biochemistry- it is the amount of product formed by an enzyme in a given amount of time under given conditions per milligram of total protein. (equal to the rate of the reaction multiplied by the volume of the reaction divided by the mass of total protein.
Term
Fibrous protein
Definition
generally form connective tissue, tendons, bone matrices, and muscle fiber, is typically water insoluble and have long chains
Term
ß-galactosidase
Definition
is a hydrolase enzyme that catalzyes the hydrolysis of ß galactosides into monosaccharides. (Lactase is often confused as an alternative name for this but it is actually simply a sub class )
Term
domain
Definition
is a part of a protein sequence and structure that can evolve, function, and exist independently of the rest of the protein chain.
Term
pK
Definition
is a specific type of equilibrium constant that measures the propensity of a larger object to separate reversibly into smaller components, as when a complex falls apart into its component molecule, or when a salt splits up into its component ions.
Term
monoclonal antibody
Definition
are monospecific antibodies that are the same because they are made by identical immune cells that are all clones of a unique parent cell
Term
Homogenate
Definition
its is when all constituents are all of the same nature
Term
Enzyme activity assay
Definition
used to measure enzymatic activity
Term
True or False- Differences in myoglobin and hemoglobin function are explained by differences in myoglobin and hemoglobin tertiary structures
Definition
False- they are explained by differences in QUATERNARY structures
Term
Ribonuclease and trypsin are
Definition
proteins that catalyze chemical reactions
Term
Fingerprinting does what?
Definition
provides a two dimensional separation and analysis of peptides.
Term
_____ are RNA catalysts
Definition
Ribozymes
Term
____ assays are based on the fact that a substrate absorbs light of a particular wavelength.
Definition
Colorimetric
Term
Enzyme activity can be altered by...
Definition
phosphorylation, dephosphorylation, and allsoteric effectors.
Term
True or False- The term cooperativity embodies the idea that changes in the conformation of one subunit are communicated to the other identical subunits in any given molecule so that all of these subunits are in the same conformation
Definition
True
Term
Phosphorylation
Definition
is the addition of a phosphate group to a protein or other organic molecule. Phosphorylation activates or deactivates many protein enzymes, causing or preventing the mechanisms of diseases such as cancer and diabetes- causes enzymes to become activated or deactivated (dephosphorylation)
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