Which of the following is an example of potential rather than kinetic energy?
- the muscle contractions of a person mowing grass
- water rushing over Niagara falls
- light flashes emitted by a firefly
- a molecule of glucose
- the flight of an insect foraging for food
Which of the following is (are) true for anabolic pathways?
- they do not depend on enzymes
- they are usually highly spontaneous chemical reactions
- they consume energy to build up polymers from monomers
- they release energy as they degrade polymers to monomers
- they consume energy to decrease the entropy of the organism and its environment
Which of the following is true for all exergonic reactions?
- the products have more total energy than the reactants
- the reaction proceeds with a net release of free energy
- the reaction goes only in a forward direction: all reactants will be converted to products, but no products will be converted to reactants
- a net input of energy from the surroundings is required for the reactions to proceed
- the reactions are rapid
When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated?
- it is used to power yet more cellular work
- it is used to store energy as more ATP
- it is used to generate ADP from nucleotide precursors
- it is lost to the environment
- it is transported to specific organs such as the brain
According to the induced fit hypothesis of enzyme catalysis, which of the following is correct?
- the binding of the substrate depends on the shape of the active site
- some enzymes change their structure when activators bind to the enzyme
- a competitive inhibitor can outcompete the substrate for the active site
- the binding of the substrate changes the shape of the enzymes active site
- the active site creates a microenvironment ideal for the reaction
When you have a severe fever, what grave consequence may occur if the fever is not controlled?
- destruction of your enzymes' primary structure
- removal of amine groups from your proteins
- change in the tertiary structure of your enzymes
- removal of the amino aids in active sites of your enzymes
- binding of your enzymes to inappropriate substrates
The mechanisms in which the end product of a metabolic pathway inhibits an earlier step in the pathway is most precisely described as
- metabolic inhibition
- feedback inhibition
- allosteric inhibition
- noncooperative inhibition
- reversible inhibition
Which of the following is true of enzymes?
- nonprotein cofactors alter the substrate specificity of enzymes
- enzyme function is increased if the 3D structure or conformation of an enzyme is altered
- enzyme function is independent of physical and chemical environmental factors such as pH and temperature
- enzymes increase the rate of chemical reaction by lowering activation energy barriers
- enzymes increase the rate of chemical reaction by providing activation energy to the substrate
Which curve(s) on the graphs above may represent the temperature and pH profiles of an enzyme taken from a bacterium that lives in a mildly alkaline hot springs at temperatures of 70C or higher?
- curves 1 and 5
- curves 2 and 4
- curves 2 and 5
- curves 3 and 4
- curves 3 and 5
The following question is based on the reaction A+B <--> C+D shown in Figure 8.1 Which of the following represents the activation energy required for the enzyme-catalyzed reaction in Figure 8.1?
Some bacteria are metabolically active in hot springs because
- they are able to maintain a lower internal temperature
- high temperatures make catalysis unnecessary
- their enzymes have high optimal temperatures
- their enzymes are completely insensitive to temperature
- they use molecules other than proteins or RNAs as their main catalysts
Which of the following statements describes the results of this reaction? C6H1206 --> 6CO2 + 6H20 + Energy
- C6H12O6 is oxidized and O2 is reduced
- O2 is oxidized and H2O is reduced
- CO2 is reduced and O2 is oxidized
- C6H12O6 is reduced and CO2 is oxidized
- O2 is reduced and CO2 is oxidized
During aerobic respiration, electrons travel downhill in which sequence?
- food --> citric acid cycle --> ATP --> NAD+
- food --> NADH --> electron transport chain --> oxygen
- glucose --> pyruvate --> ATP --> oxygen
- glucose --> ATP --> electron transport chain --> NADH
- food --> glycolysis --> citric acid cycle --> NADH --> ATP
The ATP made during glycolysis is generated by
- substrate-level phosphorylation
- electron transport
- oxidation of NADH to NAD+
Which process in eukaryotic cells will proceed normally whether oxygen (O2) is present or absent?
- electron transport
- the citric acid cycle
- oxidative phosphorylation
The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is
Where are the proteins of the electron transport chain located?
- mitochondrial outer membrane
- mitochondrial inner membrane
- mitochondrial intermembrane space
- mitochondrial matrix
What is the oxidizing agent in the following reaction? Pyruvate + NADH + H+ --> Lactate + Nad+
How many carbon dioxide molecules are released during cellular respiration as a result of the oxidation of one molecule of glucose?
Why are carbohydrates and fats considered high energy foods?
- they have a lot of oxygen atoms
- they have no nitrogen in their makeup
- they can have very long carbon skeletons
- they have a lot of electrons associated with hydrogen
- they are easily reduced
Which of the following intermediary metabolites enters the citric acid cycle and is formed, in part, by the removal of a carbon (CO2) from one molecule of pyruvate?
- acetyl CoA
Which of the following is characterized by a cell releasing a signal molecule into the environment followed by a number of cells in the immediate vicinity responding?
- hormonal signaling
- autocrine signaling
- paracrine signaling
- endocrine signaling
- synaptic signaling
Testosterone functions inside a cell by
- acting as a signal receptor that activates tyrosine kinases
- binding with a receptor protein that enters the nucleus and activates specific genes
- acting as a steroid signal receptor that activates ion channel proteins
- becoming a second messenger that inhibits adenylyl cyclase
- coordinating a phosphorylation cascade that increases spermatogenesis
Which of the following is true of transcription factors?
- they regulate the synthesis of DNA in response to a signal
- they transcribe ATP into cAMP
- they initiate the epinephrine response in animal cells
- they control gene expression
- they regulate the synthesis of lipids in the cytoplasm
In the formation of biofilms, such as those forming on unbrushed teeth, cell signaling serves which function?
- formation of mating complexes
- secretion of apoptotic signals
- aggregation of bacteria that can cause cavities
- secretion of substances that inhibit foreign bacteria
- digestion of unwanted parasite populations
Which of the following statements about quorum sensing is FALSE? Quorum sensing
- is cell-cell communication in eukaryotes
- is species specific
- may result in biofilm formation
- is particularly well studied because of its medical importance
In general, a signal transmitted via phosphorylation of a series of proteins
- brings a conformational change to each protein
- requires binding of a hormone to a cytosol receptor
- cannot occur in yeasts because they lack protein phosphatases
- requires phosphorylase activity
In the figure, the dots in the space between the two structures represent which of the following?
- receptor molecules
- signal transducers
What explains the increased concentration of Ca++ in the ER?
- calcium ions are actively imported from the cytoplasm into the ER
- calcium concentration is kept low in the cytoplasm because of its high usage level
- calcium cannot enter the plasma membrane through ion channels
- calcium levels in the blood or other body fluids are extremely low
- the Ca ions are recycled from other molecules in the ER
Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because
- only target cells retain the appropriate DNA segments
- intracellular receptors are present only in target cells
- most cells lack the Y chromosome required
- only target cells possess the cytosolic enzymes that transduce the testosterone
- only in target cells in testosterone able to initiate the phosphorylation cascade leading to activated transcription factor
Which of the following describes the events of apoptosis?
- the cell dies, it is lysed, its organelles are phagocytized, and its contents are recycled
- its DNA and organelles become fragmented, it dies, and it is phagocytized
- the cell dies and the presence of its fragmented contents stimulates nearby cells to divide
- its DNA and organelles are fragmented, the cell shrinks and forms blebs, and the cell debris is digested
- its nucleus and organelles are lysed, then the cell enlarges and bursts
The centromere is a region in which
- chromatids remain attached to one another until anaphase
- metaphase chromosomes become aligned at the metaphase plate
- chromosomes are grouped during telophase
- the nucleus is located prior to mitosis
- new spindle microtubules form at either end
If cells in the process of dividing are subjected to colchicine, a drug that interferes with the formation of the spindle apparatus, at which stage will mitosis be arrested?
Regarding mitosis and cytokinesis, one difference between higher plants and animals is that in plants
- the spindles contain microfibrils in addition to microtubules, whereas animal spindles do not contain microfibrils
- sister chromatids are identical, but they differ from one another in animals
- a cell plate begins to form at telophase, whereas animals a cleavage furrow is initiated at that stage
- chromosomes become attached to the spindle at prophase, whereas in animals chromosomes do not become attached until anaphase
- spindle poles contain centrioles, whereas spindle poles in animals do not
During which phase of mitosis do the chromatids become chromosomes?
Which of the following is true concerning cancer cells?
- they do not exhibit density-dependent inhibition when growing in culture
- when they stop dividing, they do so at random points in the cell cycle
- they are not subject to cell cycle controls
- when they stop dividing, they do so at random points in the cell cycle, and they are not subject to cell cycle controls
- when they stop dividing, they do so at random points in the cell cycle; they are not subject to cell cycle controls; and they do not exhibit density-dependent inhibition when growing in culture.
After telophase I of meiosis, the chromosomal makeup of each daughter cell is
- diploid, and the chromosomes are each composed of a single chromatid
- diploid, and the chromosomes are each composed of two chromatids
- haploid, and the chromosomes are each composed of a single chromatid
- haploid, and the chromosomes are each composed of two chromatids
- tetraploid, and the chromosomes are each composed of two chromatids
Which of the following occurs in meiosis but not in mitosis?
- chromosome replication
- production of daughter cells
- alignment of tetrads at metaphase plate
- both B and D
Figure 13.2 of a single pair of homologous chromosomes as they might appear during various stages of either mitosis or meiosis, and answer the following question.
Which diagram represents prophase I of meiosis?
Which of the following is true of the process of meiosis?
- two diploid cells result
- four diploid cells result
- four haploid cells result
- four autosomes result
- four chiasmata result