AP BIO - Unit 3 Test
Enzymes are protein catalysis responsible for increasing the rate at which biochemical reactions occur in a cell. Which of the following statements best describes how enzyme accomplish this task
The enzyme decreases the activation energy needed for the chemical reaction to occur
Which of the following describes a metabolic consequence of a shortage of oxygen in muscle cells?
A buildup of lactic acid in the muscle tissue due to fermentation
The graph above shows changes in glucagon and insulin secretions at different concentration of blood glucose. Which of the following feedback mechanisms is best supported by the data
A low glucose level causes the release of glucagon, which stimulates the release of more glucose from tissues, which in turn lowers the amount of glucagon being released
Of the following, a receptor protein in a membrane that recognizes a ligand is most similar to
A specific catalytic site of an enzyme binding a substrate
In 1944 Avery, MacLeod, and McCarty performed transformation experiments using live, harmless bacteria treated with various enzymes. Which of the following enzymes were used and why? A. Proteases and RNAases to rule out protein and RNA as transforming factors B. Lipase (an enzyme that facilitates breakdown of lipids) to rule out lipoproteins as the transforming factor C. Kinase (an enzyme that facilitates transfer of a phosphate group from ATP to a substrate molecule) to show that transformation is phosphorylation dependent D ATPase to show that transformation isn't dependent on ATP A
A. Proteases and RNAases to rule out protein and RNA as transforming factors
In the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of
ATP, CO2, and ethanol (ethyl alcohol)
Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's
Activation Energy
How can one increase the rate of a chemical reaction?
Add a catalyst
The endocrine system incorporates feedback mechanisms that maintain homeostasis. Which of the following demonstrates negative feedback by the endocrine system
After a meal, blood glucose levels become elevated, stimulation beta beta cells of the pan crease to release insulin into the blood. Excess glucose is then converted to glycogen in the liver, reducing blood glucose levels
Antidiuretic hormone (ADH) is important in maintaining homeostasis in mammals. ADH is released from the hypothalamus in response to high tissue osmolarity. In response to ADH, the collecting duct and distal tubule in the kidney become more permeable to water, which increases water reabsorption into the capillaries. The amount of hormone released is controlled by a negative feedback loop. Based on the model presented,which of the following statements expresses the proper relationship between osmolarity, ADH release, and urine production?
As tissue osmolarity rises, MORE ADH is released, causing LESS WATER to be excreted as urine
The vertebrate forelimb initially develops in the embryo as a solid mass of tissue. As development progresses, the solid mass near the end of the forelimb is remodeled into individual digits. Which of the following best explains the role of apoptosis in remodeling the forelimb? A. apoptosis replaces old cells with new ones that are less likely to contain mutations B. Apoptosis involves the regulated activation of proteins in specific cells of the developing forelimb that leads to the death of those cells C. Apoptosis involves the destruction of extra cells in the developing forelimb, which provides nutrients for phagocytic cells D. apoptosis in the developing forelimb triggers the differentiation of cells whose fate was not already determined
B. Apoptosis involves the regulated activation of proteins in specific cells of the developing forelimb that leads to the death of those cells
Control of body temperature is an example of which of the following
Both homeostatic mechanism and negative feedback system
Butterflies of the genus Colias live in the Rocky Mountains, where they experience a wide range of temperatures. Different variants of a particular glycolytic enzyme in the flight muscles are optimally active at different temperatures.Within the same population, some individual butterflies fly most effectively at 29 C° , while others fly most effectively at 40°C. Still others can be equally active at both temperatures. Which of the following claims is most consistent with the observed butterfly behavior?
Butterflies that express two variants of the enzyme are active over a greater range of temperatures
All of the following are pat of the phosphorylation cascade model EXCEPT
GTP donates a phosphate group to an inactive protein kinase
If ATP breakdown is inhibited, which of the following types of movement across cell membranes is also inhibited? A. Movement of oxygen into a cell B. Movement of water through aquaporins C. Passage of a solute against its concentration D. Facilitated diffusion of a permeable substance
C. Passage of a solute against its concentration
Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?
Catabolism
Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?
Competitive inhibition
When glucose is used as the energy source, the largest amount of ATP is produced in
Electron transfer phosphorylation
Epinephrine is a protein hormone found in many animals. Epinephrine stimulates a signaling pathway that results in the breakdown of glycogen to glucose in the liver cells. Which of the following describes the initial steps in the process whereby epinephrine stimulates glycogen breakdown?
Epinephrine binds to the cell-surface receptor; the activated receptor stimulates production of the second messenger, cAMP
Which metabolic pathway is common to both fermentation and cellular respiration of glucose
Glycolysis
Which of the following questions will best direct an investigation of the mechanism of ATP Synthase?
Is the phosphorylation of ADP by ATP synthase dependent on the formation of a proton gradient
When ATP releases some energy, it also releases inorganic phosphate. What happens to the inorganic phosphate in the cell?
It can be added to other molecules in order to activate them
Which of the following statements is true about the neurotransmitter used to transmit the impulse at the synapse?
It is released by fiber X when an impulse travels the length of fiber X.
which of the following statements is true of signal molecules?
Protein kinase A activation is one possible result of signal molecules binding to G protein coupled receptors.
The figure above represents a generalized hormone-signaling pathway. Briefly explain the role of each numbered step in regulating target gene expression.
Step one represents reception, where the target cell first receives a signal from a protein outside the cell. Step two represents transduction, where the signal is passed through a series of chemical reactions through enzymes (kinases) and proteins in the cytoplasm of the cell. Step three represents response, where the cell performs the desired activity. In this case, the cell is regulating the expression of a certain gene.
When a stimulus is applied to a receptor in the skin, an action potential is propagated along a neuron to the brain, where another signal is sent back to then muscle for response.Which of the following best describes what occurs when the action potential reaches a chemical synapse at the end of an axon
The action potential cause a release of neurotransmitter that travel across the synapse
According to the induced fit hypothesis of enzyme catalysis, which of the following is correct?
The binding of the substrate changes the shape of the enzyme's active site
The pH of the inner thylakoid space has been measured, as have the pH of the stroma and of the cytosol of a particular plant cell. Which, if any, relationship would you expect to find?
The pH within the thylakoid is less than that of the stroma
A human kidney filter about 200 liters of blood each day. Approximately 2 liters of liquid and nutrients waste are excreted as urine. The remaining fluid and dissolve substances are reabsorbed and continue to circulate throughout the body. ADH is secreted in response to reduce plasma volume. ADH targets this collection ducts in the kidney, stimulating the insertion of aquaporions into their plasma membrane and an increased reabsorption of water
The person would produce greater amounts of dilute urine
Assume a thylakoid is somehow punctured so that the interior of thylakoid is no longer separated by the stroma. This damage will have the most direct effect on which of the following processes
The synthesis of ATP
Trypsinogen is split by the enzyme enterokinase to form an activated molecule of the protease trypsin. Which of the following would confirm that the activation of trypsin is an example of how a positive feedback mechanism can amplify a biological process?
The trypsin produced by the reaction is capable of splitting and activating additional trypsinogen molecules
phosphorylation cascade involving a series of protein kinases are useful for cellular signal transduction because
They amplify the original signal many fold
How do tryosine-kinase receptors transduce a signal?
They form a dimmer, they phosphorylate each other's tyrosines; specific relay or response proteins ind to and are activated by specific phosphorylated tyrosines.
what is most likely to happen to an animal's target cell that lack receptors for local regulators?
They might not be able to multiply in response to growth factors for nearby cells
The process of transduction usually begins
When the signal molecule changes the receptor protein in some way
The figure above shows a model of a ligand precursor being cleaved to produce an active ligand that binds to a specific receptor. Which of the following is most likely to reduce the binding of the active ligand to its receptor?
a mutation in the receptor gene that causes a substitution on a charged amino acid for a nonpolar amino acid in the ligand binding site of the receptor
if a reaction results in (delta)G = -625kcal/mcl, one can conclude a. free energy was released b. free energy was absorbed c. the reaction is endothermic d. the reaction is catabolic e. the reaction is anabolic
a. free energy was released
34. this is a coupled reaction, which means a. it links endergonic and exergonic processes b. it links 2 reaction with the same enzyme c. it links ADP and phosphate d. it links reaction together in a metabolic pathway e. it links glucose with a phosphate
a. it links endergonic and exergonic processes
Molecule M binds to enzyme E at the binding site that's not the active site and the enzymes activity decreases. all are true but a. molecule M is a competitive inhibitor of the enzyme b. this is one mechanism in feedback inhibition c. upon binding, molecule M changed the structre of the enzyme, thus affecting the enzymes ability to bind to its substrate d. molecule M is an allosteric inhibitor e. molecule M is most likely a product of the pathway of which enzyme E is a part
a. molecule M is a competitive inhibitor of the enzyme
33.the enzyme-catalyzed reaction depicted represents a. the phosphorylation of glucose b.the phosphorylation of ADP c. the addition of dehydrogenase d. phosphofructokinase activity e. the dephosphorylation of glucose
a. the phosphorylation of glucose
which of the following statements is NOT correct a. they raise the energy of activation of all reactions b. they enable reactions to occur at relatively low temps c. some enzymes require coenzymes to work d. enzymes remain unchanged during a reaction e. they're located within the plasma membrane of cell
a. they raise the energy of activation of all reactions
Nerve growth factor (NGF) is a water-soluble signaling molecules. Its receptor is most likely a. a cell surface transmembrane receptor because NGF is hydrophobic b. a cell surface transmembrane receptor because NGF is hydrophilic and unable to cross the lipid bilayer c. an intracellular receptor because NGF is hydrophilic and is able to cross the lipid bilayer d. an AP biology student that possess specificity for NGF and is biophilic
b. a cell surface transmembrane receptor because NGF is hydrophilic and unable to cross the lipid bilayer
enzymes are predominantly made up of... a. monosacchrides b. amino acids c. fatty acids d. nucleotides e. inorganic materials
b. amino acids
which of the following best describes the reactions:A + B ----> AB + energy a. hydrolysis b. an exergonic reaction c. an endothermic reaction d. catabolism
b. an exergonic reaction
enzymes function to increase the rate of a reaction by a. increasing the concentration of substrate b. decreasing the Ea (activation energy) c. competing with the substrate d. breaking down ATP e. hydrolyzing the substrate
b. decreasing the Ea (activation energy)
all of the following are correct about enzyme-catalyzed reactions EXCEPT a. enzymes exhibit specificity with substrates b. enzymes add necessary energy to speed up chemical reactions c. enzymes lower the activation energy needed for the reaction to occur d. enzymes often require the presence of cofactors like vitamins and minerals e. not all enzymes are active at the same pH
b. enzymes add necessary energy to speed up chemical reactions
Ethylene is an organism compound produced by ripening fruits. In a controlled experiment, researchers found that ethylene gas stimulated the ripening process in newly harvested fruits. Which of the following describes the most likely connection between natural ethylene production and fruit ripening? a. as a result of metabolic inactivity, newly harvested fruits are unable to absorb ethylene gas from the atmosphere b. ethylene gas is a chemical signal through which ripening fruits trigger the ripening process in other fruits c. because of normal phenotypic variation, only some of the fruits in a given generation are expected to produce ethylene gas d. the rate of ethylene gas production by ripening fruits is an indicator of the relative ago an ecosystem
b. ethylene gas is a chemical signal through which ripening fruits trigger the ripening process in other fruits
the effect of competitive inhibitors can be minimized by a. increasing the pH above the enzymes optimal range b. increasing the concentration of substrate c. adding noncompetitive inhibitors d. lowering the temp below the enzyme's optimal range e. removing cofactors
b. increasing the concentration of substrate
when atp is used for transport, mechanical, or chemical work: a. it is the adenosine that provides the energy b. it is the phosphate groups that perform the work c. it is the precursor, ADP, that performs the work d. energy is released as ATP is formed e. the sugar of ATP is broken down to produce energy
b. it is the phosphate groups that perform the work
you do an experiment in the lab and add increasing amount of substrate to a solution containing an enzym and a pH buffer. container is at optimal temp for the enzyme. each time you add substrate, you measure the rate of the reaction. x-axis is the substrate and the y-axis is the reaction rate. what will you find over time? a. the rate of the reaction will have a slope of 1 and continue in a linear fashion until reactants run out b. the rate will increase rapidly, taper off, and plateau c. the rate will increase slowly, plateau, and drop to 0. d. the graph will be a perfect bell curve e. the graph is unpredictable without more info about the enzymes properties
b. the rate will increase rapidly, taper off, and plateau
You and your lab team have designed a drug that blocks the transfer of a phosphate group to a protein molecule. Which of the following would be most directly affected by this drug? a. intracellular protein receptor activity b. transduction of a signal along a protein kinase signaling pathway c. transmembrane protein receptor activity d. binding of transcription factors to DNA
b. transduction of a signal along a protein kinase signaling pathway
if the free energy change of a reaction is greater than zero, then the reaction is a. favorable/spontaneous b. unfavorable/nonspontaneous c. at equilibrium d. endothermic e. exothermic
b. unfavorable/nonspontaneous
A drug designed to inhibit the response of cells to testosterone would almost result in which of the following? a. lower cytoplasmic levels of cAMP b. an increase in receptor tyrosine kinase activity c. a decrease in transcriptional activity of certain genes d. an increase in cytosolic calcium concentration
c. a decrease in transcriptional activity of certain genes
the difference between cofactors and coenzymes is a. cofactors are no necessary and coenzymes are b. cofactors bind to the active site of the enzyme and coenzymes bind to the allosteric site c. cofactors can be inorganic or organic, coenzyme is just another name for organic cofactors d. cofactors are always vitamins, coenzymes are ions e. cofactors help with essential metabolic reactions, coenzymes assist with nonessential reactions
c. cofactors can be inorganic or organic, coenzyme is just another name for organic cofactors
which involves the binding of a molecule to the active site of an enzyme? a. noncompetitive inhibition b. allosteric inhibition c. competitive inhibition d. a, b, and c e. none of the above
c. competitive inhibition
allosteric regulation of enzyme activity involves a. competitive binding at the active site b. reducing the number of available cofactors c. conformational changes in enzyme due to binding at sites other than the active site d. binding of allosteric inhibitors to the substrate e. activators binding to the active site
c. conformational changes in enzyme due to binding at sites other than the active site
which best describes the relationship between enzyme activity and temperature? a.enzyme activity always increases with increasing temp b.higher temps. increase enzyme activity by lowering the activation energy c. higher temps increase enzyme activity by increasing the number of activated complexes that form each min d. lower temps. denature proteins by freezing them e. enzymes are activated allosterically at certain temps
c. higher temps increase enzyme activity by increasing the number of activated complexes that form each min
Cell communication is critical fro the function of both unicellular and multicellular eukaryotes. Which of the following is likely true of cell signaling? a. cell signaling uses the highest molecular weight molecules found in living cells b. cell signaling has largely been replaced by other cell functions in higher mammals c. similar cell signalizing pathways in diverse eukaryotes are evidence of conserved evolutionary processes d. cell signalizing functions mainly during early developmental stages
c. similar cell signalizing pathways in diverse eukaryotes are evidence of conserved evolutionary processes
which is an anabolic reaction? a. ATP ---> ADP + P b. hydrolysis c. starch + n(H2O) ---> n(C6H12O6) d. CO2 + H2O ---> C6H12O6 + O2 e. glycolysis
c. starch + n(H2O) ---> n(C6H12O6)
what does NOT affect the rate of an enzymatic reaction a. temperature b. pH c. the concentration of enzyme d. presence of inhibitors e. all of the above
c. the concentration of enzyme
A cell lacking oligosaccharides on the external surface of its plasma membrane would likely be inefficient in
cell-cell communication
all are true EXCEPT: a.enzymes lower the activation energy of a reaction b. most enzymes have allosteric binding sites c. enzymes are made up of proteins d. all enzymes in the human body are most active at 37°C and pH around 7 e. they catalyze reactions in both directions
d. all enzymes in the human body are most active at 37°C and pH around 7
enzymes act as a. reduction reagents b. oxidation reagents c. reactants that convert into product d. catalysts e. substrates
d. catalysts
At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of estrogens and other steroid hormones. How can one hormone, such as estrogen, mediate so many effects? a. estrogen is produced in very large concentration and therefore diffuses widely b. estrogen has specific receptors inside several cell types, but each cell responds in the same way to its binding c. estrogen is kept away from the surface of any cells not able to bind at the surface d. estrogen binds to specific receptors inside many kinds of cells, each of which have different responses to its binding
d. estrogen binds to specific receptors inside many kinds of cells, each of which have different responses to its binding
an enzyme speeds up a chemical reaction by a. giving up electrons in reduction reactions b. gaining electrons in an oxidation reaction c. acting as a reactant to form new products d. providing intermolecular strain to weaken chemical bonds e. acting as a substrate and being used up in reaction
d. providing intermolecular strain to weaken chemical bonds
Precise regulation of specific hormone levels is required for optimal sperm production in mammals, as summarized in the figure above. Anabolic-androgenic steroids (AAS) are synthetic variants of or alter their physique. Assuming that AAS function in the same way as naturally occurring testosterone, it is most likely that long-term abuse of AAS would a. stimulate FSH secretion b. stimulate testosterone production c. stimulate LH secretion d. reduce sperm production
d. reduce sperm production
The diagram above illustrates feedback control as exerted by the hormone thyroxine. Following surgical removal of the thyroid gland, the level of TSH in the blood will increase. Which of the following best explains this increase?
decrease in thyroxine levels means a loss of inhibition to the hypothalamus and anterior pituitary, leading to increased TSH secretion
you decide to increase the rate of an enzymatic reaction. which action is LEAST likely to help? a. adding more reactants b. adding more enzymes c. adding heat d. mechanically stirring the reactants in the beakers e. adding more product
e. adding more product
which best describes enzymes? a. they're present in the nucleus during DNA replication b. they are made of amino acids c. its collective action regulates the metabolism of cell d. many enzymes can be activated or inactivated by the presence of absence of specific chemicals or hormones e. all of the statements above are correct
e. all of the statements above are correct
egg whites contain albumin, which looks clear when uncooked eggs are opened. cooking them at high temps changes the structure of the albumin, turning it white. which term correctly identifies this process? a. hydrolysis b. saturation c. synthesis d. allosteric inhibition e. denaturation
e. denaturation
ATP serves as the cellular energy source for all organisms because a. it is a small molecule b. it is a negatively charged molecule c. its synthesis is exergonic d. it is stable for long periods of time e. its hydrolysis releases energy that can do cellular work
e. its hydrolysis releases energy that can do cellular work
if an enzyme is saturated, this means a. the enzymes cannot continue to catalyze the reaction b. the reaction is at dynamic equilibrium c. the rate of the reaction will slow until it stops d. the enzymes need more reactants e. the enzymes are catalyzing the reaction at the maximum rate
e. the enzymes are catalyzing the reaction at the maximum rate
which of the following can be used to determine the rate of an enzyme-catalyzed reaction? a. the rate of substrate formed b. the decrease in temp c. the rate of enzyme formed d. the rate of enzyme used up e. the rate of substrate used up
e. the rate of substrate used up
if a reaction in a cell requires an enzyme, a. the reaction must be exergonic b. the reaction must require ATP c. the reaction is subject to allosteric regulation d. the reaction is regulated by competitive inhibition e. the reaction occurs more readily with the enzyme than it would if there were no enzyme
e. the reaction occurs more readily with the enzyme than it would if there were no enzyme
A chemical reaction that has a positive ∆G is correctly described as
endergonic
Under anaerobic condition, muscle cells produce
lactate
The signaling system in an animal cell lacking the ability to produce GTP
would not be able to activate and initiate the G-protein on the cytoplasmic side of the plasma membrane
