biolotical catalysts that increase rate of chemical reactions (without change in temperature)
What causes enzyme activity?
change in acid-base balance or variations in body temp can disrupt the protein's structure and interfere with its ability to regulate metabolism
Since enzymes have a major job that is vital to life, they get hlp from other molecules called:
coenzymes & cofactors
Inorganic group, includes metal ions (mineral in our diets) such as Ca+2, Mg+2, Mn+2, Cu+2, Zn+2 & selenium
Organic group derived from vitamins (modified by the liver); transport small molecules needed by enzymes
2 important examples of cofactors/coenzymes that function as carriers of hydrogen atoms (carrying atoms from place to place in the metabolic pathways of the cell)
NAD & FAD
the Law of Mass Action states direction of reaction is from side of equation where concentration is ____________ to side where concentration is _________.
Sequences of enzymatic reactions that begin with initial substrate, progress through intermediates, & end with a final product:
Occurs when 1 product in a divergent pathway inhibits activity of the branch-point enzyme:
What's it called when product binds to enzyme causing it to change to an inactive shape?
This is due to inherited defects in genes for enzymes in metabolic pathways:
inborn errors of metabolism
Metaboic disease can result from either:
Increases in intermediates formed prior to the defective enzyme; decreases in products normally formed after the defective enzyme
What does the First Law of Thermodynamics state?
Energy can be transformed byt not created or destroyed
What does the 2nd Law of Thermodynamics state?
Energy transformations increase entropy (=degree oniof disorganization of a syemtem)
What is it called when cells require constant inputs of free energy from environment to buck entropy & remain highly organized?
Enzymes bind to their ___________ with a lock & key precision, so any change in the lock (_______) will interfere with the binding by the key (_________)
substrates; enzyme; substrate
Inborn errors of metabolism (defects in the DNA) will alter the enzyme's _________ structure (amino acid sequence) and can cause disease by interfering with the fit between the substrate and enzyme
A catalyst is a chemical substance that:
increases rate of reaction
is not itself changed by the reaction
does not change the nature of the reaction
does not change the final result of the reaction
Enzymes that rearrange atoms within their substrate molecules to form products with the same composition but with a different structure, are called:
Different models of the same enzyme (they must have the same active site and catalyze the same reaction) made by different tissues are called:
Which of the following statements about enzymes is false?
a. enzymes are biological catalysts
b. enzymes speed up chemical reactions by raising the activation energy
c. enzymes work faster at higher temperatures
d. enzymes are not changed by the reaction they catalyze
e. enzymes often require the presence of minerals or other "helper" molecules
b. Enzymes speed up chemical reactions by raising the activation energy (false statement)
Which of the following molecules is the correct substrate molecule for the enzyme carbonic anhydrase?
a. H2) b. starch c. lactic acid d. H2CO3
T/F: Without enzymes all chemical reactions simply will not run.
False. Without enzymes all chemical reactions will run, but much slower.
T/F: Isoenzymes display the same active site and catalyze the same chemical reaction but will differ in composition and structure elsewhere in the molecules.
T/F: Riboenzymes are unique molecules of RNA that function as enzymes in reactions involving the remodeling of other RNA molecules and in the formatin of a growing polypeptide during protein synthesis at the ribosome.
T/F: Enzymes known as synthases or synthetases catalyze reactions that involve removing water (dehydration) from smaller molecules to form bonds that result in a larger product molecule.
T/F: The term substrate always refers to the reactant molecule in an enzyme-catalyzed reaction.
Which of the following does not alter enzyme activity?
a. the temp & pH of the solution
b. the concentration of cofactors & coenzymes present
c. the concentration of oxygen present
d. the concentration of enzyme & substrate molecules present
c. the concentration of oxygen present (does not alter enzyme activity)
Which of the following is least likely to act as a cofactor? a. calcium b. magnesium c. copper d. oxygen e. zinc
d. oxygen (least likely to act as a cofactor)
In enzyme-catalyzed reactions, cofactors bind directly to the a. enzyme b. active site c. substrate d. cofactors bind to all of these locations e. cofactors bind to none of these locations
d. cofactors bind to all of these locations
Coenzymes participate in enzyme-catalyzed reactions by:
transporting hydrogen atoms & small molecules from one enzyme to another
Which statement about zymogens is false?
a. zymogens are extremely active, hydrolytic enzymes b. ex's of zymogens include the protein kinase enzymes in ctyoplasm c. ex's of zymogens include the digestive enzymes from the pancreas d. zymogens must first be activated by another enzyme or ligand molecule e. attachment of a phosphage group can inactivate certain zymogens
a. zymogens are extremely active, hydrolytic enzymes
"Saturation" in an emzyme-catalyzed reaction means that the ____________ are saturated with _____________.
Allosteric inhibition is a mechanism along metabolic pathways by which:
a. inhibition of an earlier step at a branch point along the pathway occurs b. structural changes at the active site occurs to interfere with the enzyme c. the final product inhibits an earlier enzymatic step (end-product inhibition) d. all statements describe allosteric inhibition
d. all statements describe allosteric inhibition
Inborn errors of metabolism that cause disease result in a (an) __________ (increase/decrease) in the amount of intermediates formed prior to the defective step, and an (an) __________ (increase/decrease) in the number of final products formed along alternate pathways.
The inborn error of metabolism that all newborn babies are tested for and that, once detected, can be controlled by a diet low in one specific amino acid, is known as:
T/F: Higher temperatures decrease the rate of enzyme activity by altering the tertiary structure of the enzyme.
T/F: The rate of enzyme activity is decreased by concentrations of hydrogen ion (pH), which are either too high or too low.
T/F: Alkaline phosphatase is an enzyme with a pH optimum having a lower number than that of acid phosphatase enzymes.
False: Alkaline phosphatase is an emzyme with a pH optimum having a higher number than that of acid phosphatase enzymes.
T/F: Cofactors are organic molecules derived from water-soluble vitamins such as niacin and riboflavin.
False: Coenzymes are organic molecules derived from water-soluble vitamins such as niacin & riboflavin.
T/F: Powerful digestive enzymes destined to digest food in the intestine must be secreted in an inactive zymogen form by the pancreas to prevent local damage to cells of the pancreas.
T/F: The activation or inactivation of zymogen molecules can be as simple as adding (phosphorylation) or removing (dephosphorylation) of a phosphage group from the molecule.
T/F: Cyclic AMP (cAMP) is an important neurotransmitter molecule released from the axon terminal of neurons.
False: Cyclic AMP (cAMP) is an important intracellular regulator released from the axon terminal of neurons.
T/F: Circulating hormones from the blood & neurotransmitters from neurons can regulate the activities of intracellular enzymes, and thereby regulate many aspects of metabolism in those cells.
T/F: Given a certain number of enzymes, increasing the number of substrate molecules will increase the number of products formed.
T/F: Two different enzymes often catalyze reversible reactions, one for each direction in the reaction.
T/F: During metabolism, one intermediate can serve as a substrate for two different enzymes, thus ultimately forming two different products.
T/F: In end-product inhibition, the function of the last product formed is inhibited.
False. End-product inhibition features inhibition of earlier steps by the last product.
T/F: In diseases known as inborn errors of metabolism, the quantity of intermediates formed prior to the defective enzyme step decreases, and the quantity of intermediates & final products formed after the defective steps increases.
False. intermediates formed prior to defective enzyme step increases, & quantity of intermediates & final products formed after defective step decreases.
T/F: Phenylketonuria (PKU) is an inborn error of phenylalanine metabolism due to an inherited defect in the enzyme that catalyzes the formation of melanin from dihydroxyphenylalanine (DOPA).
False. Albinism is an inborn error of phenylalanine metabolism......
Which of the following statements about entropy is false? a. it describes the degree of disorganization of a system b. it is increased as energy is changed to another form c. as it increases the amount of free energy available to do work is reduced d. it is defined by the first law of thermodynamics e. all statements are true
d. it is defined by the first law of thermodynamics
Which of the following statements about exergonic reactions is false? a. they can release energy in the form of heat b. they convert molecules with less free energy to molecules with more free energy c. the combusion of glucose to CO2 & H2O is an example d. they convert molecules with less entropy to molecules with more entropy e. all statements true
b. they convert molecules with less free energy to molecules with more free energy
Which of the following statements about oxidation-reduction reactions is false? a. reducing agents donate electrons to another atom or molecule b. oxidizing agent accept electrons from another atom or molecule c. an atom or molecule cannot be both an oxidizing and reducing agent d. oxidation & reduction are always coupled reactions e. all statements true
c. an atom or molecule cannot be both an oxidizing & reducing agent
The final electron acceptor in a chain of oxidaton-reduction reactions that provides energy for ATP production in the cell is:
T/F: The first law of thermodynamics states that entropy can be neither created nor destroyed.
False. The first law of thermodynamics states that energy can be neither created nor destroyed.
T/F: Living cells are able to use heat energy to drive most chemical reactions.
False. Heat energy is lost from the cell & can't be used.
T/F: Oxygen is a very strong oxidizing agent and thus, a strong electron acceptor in oxidation-reduction reactions.