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125 terms

Enzymes & Energy

STUDY
PLAY
Enzymes are ___________ __________ that speed up chemical reactions:
Biological Catalysts
This enzyme in the blood & kidney helps maintain acid-base balance:
carbonic anhydrase
Helpers of cell respiration:
facilitators
help to create hormone response
enzymes
biolotical catalysts that increase rate of chemical reactions (without change in temperature)
enzymes
Most enzymes are:
proteins
Enzymes act by ___________ energy required for a reaction to proceed
lowering
Do enzymes change at the end of the reaction?
no
The ability of enzymes to lower energy requirement is due to:
structure
enzymes have highly ordered 3 dimensional shapes:
conformation
Enzymes contain pockets called:
active sites
What are the reactants of enzymes called?
substrates
The substrates are converted to ________ at the active site.
product
Substrates fit into what?
active sites
After substrates fit into the active sites what is formed?
enzyme-substrate complex
After enzyme-substrate complex is formed what happens?
reaction occurs
After enzyme-substrate complex is formed & reaction occurs what then happens?
product dissociates
Is enzyme altered after the reaction occurs & product dissociates?
No
Classes of enzymes are named according to their:
activity
What are the enzymes called that remove phosphage groups?
phosphatases
What are the enzymes called that add phosphage groups?
kinases
What converts lactic acid to pyruvate acid?
lactate dehydrogenase
These have same catalytic function but a slightly different primary structure:
isoenzymes
The rate at which the enzyme conerts substrate to product is called:
enzyme activity
What structure of enzymes must be maintained?
teritiary structure
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
cofactors
Organic group derived from vitamins (modified by the liver); transport small molecules needed by enzymes
Coenzymes
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
What is cell regulation?
the flow of molecules through pathways
Many enzymes are activated by:
phosphorylation
Many enzymes are inactivated by:
dephosphorylation
Other enzymes are activated by _________ (small molecules) called 2nd messengers.
ligands
The rate of product formation __________ as substrate concentration increases.
increases
When the reaction reaches a plateau it is said to be:
saturated
When saturation occurs the rate of rxn (activity):
cannot increase
the Law of Mass Action states direction of reaction is from side of equation where concentration is ____________ to side where concentration is _________.
higher; lower
Sequences of enzymatic reactions that begin with initial substrate, progress through intermediates, & end with a final product:
Metabolic pathways
Occurs when 1 product in a divergent pathway inhibits activity of the branch-point enzyme:
end-product inhibition
Prevents final product accumulation:
end-product inhibition
causes reaction to favor alternate pathway
end-product inhibition
What's it called when product binds to enzyme causing it to change to an inactive shape?
allosteric inhibition
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 are some examples of inborn errors of amino acid metabolism?
PKU & albinism
Refers to flow of enery in living systems
Bioenergetics
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)
(anabolic) require input of energy to proceed
Endergonic reactions
(catabolic) release energy as they proceed
Exergonic reactions
In which reaction does the product contain more free energy than reactatants?
Endergonic
In which reaction does the product contain less free energy than reactants?
Exergonic
What is it called when cells require constant inputs of free energy from environment to buck entropy & remain highly organized?
coupled reactions
Exergonic reaction is breakdown of:
ATP
What is the universal energy carrier?
ATP
Which reactions in body make ATP?
Exergonic
What does ATP stand for?
Adenosine Triphosphate
If a molecule gains electrons it is:
reduced
If a molecule loses electrons it is:
oxidized
What donates electrons?
reducing agent
What accepts electrons?
Oxidizing agent
Reduction & oxidation are always __________ reactions
coupled
Reduction/oxidation often involve transfer of _______ instead of electrons
H's
Coenzymes that play important roles as H carriers are:
NAD & FAD
Is NAD+ oxidized or reduced?
oxidized
Is NADH oxidized or reduced?
reduced
Enzymes are ___________ so they have primary, secondary, ..... structures
proteins
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
primary
Changes in the pH and temp can distort the _________ structure of an enzyme
tertiary
Each FAD can accept ___ electrons 7 bind to ___ protons, thus reduced FAD=FADH2.
2;2
Each NAD can accept ___ electrons & bind to ___ proton, thus reduced NAD=NADH + H+.
2;1
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
Catalysts make reactions go faster by:
lowering the activation energy
In enzyme-catalyzed reactions, the reactant molecules are better known as:
substrates
Enzymes that rearrange atoms within their substrate molecules to form products with the same composition but with a different structure, are called:
isomerases
Different models of the same enzyme (they must have the same active site and catalyze the same reaction) made by different tissues are called:
isoenzymes
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
d. H2CO3
T/F: Most proteins are enzymes
False. Most enzymes are proteins
T/F: Without enzymes all chemical reactions simply will not run.
False. Without enzymes all chemical reactions will run, but much slower.
T/F: Energy of activation is the amount of energy required for a reaction to proceed.
True
T/F: There are enzymes whose names do not have the characxteristic "-ase" ending, or suffic.
True
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.
True
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.
True
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.
True
T/F: The term substrate always refers to the reactant molecule in an enzyme-catalyzed reaction.
True
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)
Pepsin, an enzyme secreted by the stomach lining, would be expected to have an optimal pH of:
2
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 _____________.
enzymes; substrates
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.
increase; increase
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:
phenylketonuria (PKU)
T/F: Higher temperatures decrease the rate of enzyme activity by altering the tertiary structure of the enzyme.
True
T/F: The rate of enzyme activity is decreased by concentrations of hydrogen ion (pH), which are either too high or too low.
True
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.
True.
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.
True.
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.
True
T/F: Given a certain number of enzymes, increasing the number of substrate molecules will increase the number of products formed.
True
T/F: Two different enzymes often catalyze reversible reactions, one for each direction in the reaction.
True
T/F: During metabolism, one intermediate can serve as a substrate for two different enzymes, thus ultimately forming two different products.
True
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:
oxygen
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: Only organized or free energy can be used to perform work.
True
T/F: Photosynthesis is an example of an endergonic reaction.
True
T/F: A calorie is a unit of free energy
False. A calorie is a unit of heat energy
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: the breakdown of ATP to ADP to Pi is an exergonic reaction.
True
T/F: Oxygen is a very strong oxidizing agent and thus, a strong electron acceptor in oxidation-reduction reactions.
True
T/F: NAD is a coenzyme derived from vitamin B2
False. NAD is a coenzyme derived from vitamin B3
T/F: A molecule such as NAD or FAD can be an electron acceptor in one reaction and an electron donor in another reaction.
True