What are Enzymes?
Protein Catalysts that can slow the rate of a reaction
Protein Catalysts that can accelerate the rate of a reaction
Tightly bound coenzymes
A reaction such as the addition of a molecule of water to carbon dioxide requires an enzyme, carbonic anhydrase, in red blood cells. What are some functions of this enzyme?
Operates in animal cells, plants cells, and in the environment to stabilize carbon dioxide concentrations
The conversion from carbon dioxide to bicarbonate, would be extremely fast without this enzyme
The conversion from carbon dioxide to bicarbonate, would be extremely slow, without this enzyme
Carbonic anhydrase adjusts the acidity of the chemical environment to prevent damage to the body
Reactants in enzyme-catalyzed reactions are called substrates apoenzyme coenzyme( substrates, apoenzyme, coenzyme )
What enzyme catalyzes the hydrolysis of peptide bonds and ester bonds?
Proteolytic Enzymes
Lytic Enzymes
Carbonic anhydrase
Enzymes can display a high degree of specificity
Specificity of enzymes is due to the precise interaction of the enzyme and its cofactor
What are functions of Trypsin ?
Protein digesting enzyme
Present in pancreatic juices secreted into your small intestine during a meal
Pancreas secretes trypsin as an inactive proenzyme called trypsinogen
Helps break down food protiens
Proteolytic enzymes trypsin and papain have different degrees of specificity
Enzymes do not require cofactors for activity
Cofactors are
Large molecules that some enzymes require for activity
Small molecules that some enzymes require for activity
The two main classes of cofactors are
Coenzymes and metals
Coenzymes and acids
Metals and acids
Tightly bound coenzymes are called
Apoenzyme
bioenzyme
prosthetic groups
Substrates
An enzyme with its cofactor is an apoenzyme, without the cofactor, the enzyme is called an holoenzyme
Specific Enzymes play key roles in the conversion of light energy and carbon oxidation energy into ATP
Using ATP, enzymes can generate
Red blood cells
Chemical gradients
Electrical gradients
The free- energy change provides information about the spontaneity but not the rate of reaction
Exogeneric reactions are
A reaction that will occur without the input of energy, or spontaneously, lf delta G is negative
A reaction that will occur without the input of energy, or spontaneously, if delta G is positive
A reaction that will occur with the input of energy, or nonspontaneous, if delta G is positive
A reaction that will occur without the input of energy, or nonspontaneous, if delta G is positive
Exergonic reactions refers to
a reaction where energy is taken up
a reaction where energy is released
Delta G is negative
Delta G is positive
Do require energy to proceed occur nonspontaneously
Do not require energy to proceed, occur spontaneously
Endergonic reaction refers to
Energy being absorbed
Energy being released
Nonspontaneous reaction
Spontaneous reaction
The delta G reaction depends only on the free energy difference between reactants and products and is independent of how the reaction occurs
The delta G, of a reaction provides information about the rate of the reaction
Enzymes alter only the reaction rate and not the reaction equilibrium
The energy required to form the transition state from the substrate is called the
Activation energy
Catalyst
Endergonic
Exergonic
A chemical reaction proceeds through a , a molecular form that is no longer substrate but not yet product
What is the first step in the enzymatic catalysis process?
The formation of an enzyme substrate complex
The formation of an enzyme product complex
The formation of an enzyme reactant complex
Enzymes bring substrates together to form an enzyme-substrate enzyme-product( enzyme-substrate, enzyme-product ) complex on a particular region of the enzyme called the active site transition site( active site, transition site )
Enzymes function by lowering the activation site
The interaction between enzyme and substrate was established by
The observation that a fixed amount of enzyme displays a maximal velocity
The observation that a fixed amount of enzyme displays a minimal velocity
The maximal rate of catalysis, Vmax occurs when all of the enzyme is bound to substrate
Active sites of enzymes have common features such as
Active site is a 3 dimensional cleft or crevice created by amino acids from different parts of the primary structure
Active sites constitutes a small portion of the enzyme volume
The interaction of the enzyme and substrate at the active sites involves multiple strong interactions
Enzyme specificity depends on molecular architecture at the active site
Active sites create unique microenvironments
The enzyme changes shape upon substrate binding, a phenomenon called
Binding energy is
Free energy released upon interaction of enzyme and substrate
greatest when the enzyme interacts with the transition state
Free energy released upon interaction of enzyme and product
greatest when the enzyme interacts with the active state
Enzymes do not interact with their substrates like a lock and key
The Michaelis constant equal to the substrate concentration at which reaction rate is half its maximal value
Alcohol Aldehyde( Alcohol, Aldehyde ) dehydrogenase converts ethanol acetaldehyde( ethanol, acetaldehyde ) into acetaldehyde acetate( acetaldehyde, acetate )
Aldehyde Alcohol( Aldehyde, Alcohol ) dehydrogenase converts acetaldehyde ethanol( acetaldehyde, ethanol ) to acetate acetaldehyde( acetate, acetaldehyde )
What two enzymes play a key role in the metabolism of alcohol
Alcohol dehydrogenase and Aldehyde dehydrogenase
Alcohol dehydrogenase and Acetaldehyde dehydrogenase
Aldehyde dehydrogenase and Acetaldehyde dehydrogenase
What are the two different acetaldehyde dehydrogenase in most people ?
Low km in mitochondria
High km in cytoplasm
Low km in cytoplasm
High km in mitochondria
Kcat, is the turnover number of the enzyme,
which is the number of substrate molecules converted into product per second
which is the number of reactant molecules converted into product per second
Irreversible enzyme inhibitors bind
covalently or noncovalently to the enzyme, but with a negligible dissociation constant
covalently to the enzyme, but with a negligible dissociation constant
noncovalently to the enzyme, but with a negligible dissociation constant
Reversible inhibition is characterized
by slow dissociation of the enzyme inhibitor complex
by rapid dissociation of the enzyme inhibitor complex
Name three common types of reversible inhibition
Competitive inhibition
Uncompetitive inhibition
Noncompetitive inhibition
None of the above
The inhibitor is structurally similar to the substrate and can bind to the active site, preventing the actual substrate from binding
The inhibitor binds only to the enzyme substrate complex in what is essentially substrate dependent inhibition
The inhibitor binds either the enzyme or enzyme substrate complex
Uncompetitive inhibition is essentially substrate dependent inhibition
Binds either the enzyme or enzyme substrate complex
Substrate dependent inhibition
Prevents the actual substrate from binding
Penicillin
is an antibiotic that consist of a thiazolidine ring fused to a reactive β-lactam ring
inhibits the formation of cell walls in certain bacteria such as S. aureus.
binds to the transpeptidase because it resembles the substrate.
participates in its own inhibition, penicillin is a suicide inhibitor
The cell wall of S. aureus is constructed from the molecule peptidoglycan, which is a linear polysaccharide chain cross-linked by short peptides.
What catalyzes the peptide cross links
peptidoglycan
Glycopeptide transpeptidase
The transpeptidase reaction proceeds through an acyl-enzyme terminator.
When penicillin binds to the transpeptidase,
a serine residue at the active site attacks the carbonyl carbon of the lactam ring as if penicillin were a substrate.
a serine residue at the active site attacks the carbonyl carbon of the lactam ring as if penicillin were a product
Penicilloyl-serine derivative is inactive and very unstable
