Biology Chapter 5 6 7 8 checkouts
A series of enzymes catalyze the reactions illustrated in the following metabolic pathway: X →→ Y →→ Z →→ A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding of A decreases the activity of the enzyme that converts X to Y. The product A functions as which of the following in terms of its effect on the enzyme that converts X to Y? - a metabolic intermediate - a competitive inhibitor - an allosteric inhibitor - a coenzyme - a substrate
an allosteric inhibitor
Energy transformations in organisms are always associated with - an increase in the entropy of the organism. - an increase in the free energy of the universe. - an increase in the entropy of the universe. - a decrease in the free energy of the organism.
an increase in the entropy of the universe.
The fluid mosaic model of membrane structure suggests that membranes - are composed of a single fluid layer of phospholipids and proteins. - are composed of a fluid phospholipid bilayer sandwiched between two layers of hydrophilic proteins. - are composed of protein molecules embedded in a fluid bilayer of phospholipids. - are composed of a fluid bilayer of fatty acids with proteins associated on the outer and inner surfaces.
are composed of protein molecules embedded in a fluid bilayer of phospholipids.
The active site of an enzyme is the region that - binds noncompetitive inhibitors of the enzyme. - binds allosteric regulators of the enzyme. - is blocked by the presence of a coenzyme or a cofactor. - binds substrates for the enzyme.
binds substrates for the enzyme.
Signal transduction pathways that include a phosphorylation cascade - cause a structural change in each phosphorylated protein. - are generally inactivated by a kinase enzyme. - are propagated by steroid hormone receptors. - are generally initiated by a phosphorylase enzyme.
cause a structural change in each phosphorylated protein.
A noncompetitive inhibitor decreases the rate of an enzymatic reaction by - binding to the active site of the enzyme. - decreasing the activation energy required for the reaction. - changing the shape of the enzyme active site. - changing the ΔG for the reaction.
changing the shape of the enzyme active site.
Proteins that allow the diffusion of ions across membranes in the direction of their concentration gradients are most likely - carrier proteins - active transport pumps - channel proteins - aquaporins
channel proteins
Zinc, an essential trace element for most organisms, is required in the active site of the enzyme carboxypeptidase in order for the enzyme to function properly. The zinc most likely functions as a(n) - coenzyme derived from a vitamin. - cofactor necessary for enzyme activity. - competitive inhibitor of the enzyme. - allosteric activator of the enzyme. - noncompetitive inhibitor of the enzyme.
cofactor necessary for enzyme activity.
Which of the following reactions tend to require an input of energy? - dehydration - hydrolysis - exergonic - catabolic
dehydration
A chemical reaction that has a positive ΔG is best described as - endergonic - exergonic - spontaneous - at equilibrium.
endergonic
In chemiosmosis, what is the most direct source of energy that is used to convert ADP + Pi to ATP? - energy released as electrons flow through the electron transport system - energy released from substrate-level phosphorylation - energy released from ATP hydrolysis - energy released from movement of protons down their electrochemical gradient through ATP synthase
energy released from movement of protons down their electrochemical gradient through ATP synthase
CAM plants keep stomata closed in daytime, thus reducing loss of water. They can do this because they - fix CO2 into organic acids in the mesophyll cells, which do not rely on stomata. - fix CO2 into by combining it with RuBP in the Calvin cycle. - fix CO2 into organic acids in the bundle-sheath cells, which do not rely on stomata. - obtain CO2 through their roots during the day. - fix CO2 into organic acids during the night when temperatures are cooler.
fix CO2 into organic acids during the night when temperatures are cooler. Submit
In mitochondria, the electron transport chain pumps protons from the matrix into the intermembrane space. In what direction are protons pumped by the electron transport chain in chloroplasts? - from the stroma to the cytosol - from the matrix to the stroma - from the thylakoid space to the stroma - from the intermembrane space to the stroma - from the stroma to the thylakoid space
from the stroma to the thylakoid space
Which of the following metabolic processes in eukaryotic cells will proceed normally whether oxygen (O2) is present or absent? - glycolysis - the citric acid cycle - electron transport - oxidative phosphorylation - chemiosmosis
glycolysis
Which of the following metabolic pathways occur(s) in the cytosol of eukaryotic cells? - glycolysis and fermentation - fermentation and chemiosmosis - citric acid cycle - oxidation of pyruvate to acetyl CoA - oxidative phosphorylation
glycolysis and fermentation
Under a particular set of conditions in the lab, the enzyme in a chemical reaction is saturated. Which of the following alterations to the reaction will increase the rate at which substrate is converted to product? - increasing the concentration of substrate in the reaction - increasing the volume of the reaction without increasing the amount of substrate or enzyme - decreasing the temperature of the reaction - increasing the amount of enzyme in the reaction
increasing the amount of enzyme in the reaction
Cell membranes in plants that thrive in extreme cold are able to remain fluid by - increasing the percentage of unsaturated phospholipids in the membrane. - decreasing the number of hydrophobic proteins in the membrane. - increasing the average length of the fatty acid tails in the membrane. - decreasing the percentage of cholesterol molecules in the membrane.
increasing the percentage of unsaturated phospholipids in the membrane.
Energy released by the electron transport chain is used to pump H+ into which location in eukaryotic cells? - inner mitochondrial membrane - outer mitochondrial membrane - mitochondrial intermembrane space - mitochondrial matrix - cytosol
mitochondrial intermembrane space
The complete reactions of cellular respiration in the presence of oxygen (C6H12O6 + 6 O2 →→ 6 CO2 + 6 H2O + energy) result in which of the following? - reduction of C6H12O6 and oxidation of CO2 - oxidation of C6H12O6 and reduction of O2 - oxidation of O2 and reduction of H2O - reduction of CO2 and oxidation of O2
oxidation of C6H12O6 and reduction of O2
An early step in the process of carbon fixation combines three molecules of CO2 with three molecules of RuBP to produce three 6-carbon molecules, which are immediately converted to six 3-carbon molecules. These six molecules are phosphorylated and reduced to produce glyceraldehyde 3-phosphate (G3P). What additional events occur to complete the Calvin cycle? - release of one G3P to make sugars and regeneration of RuBP - release of one G3P to make sugars and regeneration of NADPH from NADP+ - release of two G3P to make sugars and regeneration of ATP from ADP - release of one G3P to make sugars and regeneration of citrate
release of one G3P to make sugars and regeneration of RuBP
When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway? - molecule protein - signal molecule - transducer - receptor - relay molecule
signal molecule
Which of the following reactions produces the oxygen released by photosynthesis? - electron transfer in photosystem I - chemiosmosis - reduction of NADP+ - splitting of water molecules
splitting of water molecules
Where does the Calvin cycle take place? - outer membrane of the chloroplast - interior of the thylakoid (thylakoid space) - thylakoid membrane - stroma of the chloroplast
stroma of the chloroplast
Which chemical process generates the ATP produced in glycolysis? - chemiosmosis - photophosphorylation - substrate-level phosphorylation - electron transport - oxidative phosphorylation
substrate-level phosphorylation
Which of the following descriptions would be an example of potential energy? - flood water rushing through a breach in a dam - the chemical bonds in a molecule of sucrose - a spark emitted by explosion of a firework - the movement of a bicycle coasting down a hill
the chemical bonds in a molecule of sucrose
Carrot slices placed in a 0.2 M salt solution for several hours become flaccid (limp). Carrot slices placed in fresh water for several hours become turgid (stiff). From this we can deduce that - the fresh water is hypertonic and the salt solution is hypotonic to the cells of the carrot slices - the fresh water and the salt solution are both hypotonic to the cells of the carrot slices.the fresh water and the salt solution are both hypertonic to the cells of the carrot slices - the fresh water is hypotonic and the salt solution is hypertonic to the cells of the carrot slices - the fresh water is isotonic and the salt solution is hypertonic to the cells of the carrot slices.
the fresh water is hypotonic and the salt solution is hypertonic to the cells of the carrot slices
What is the primary function of cyclic electron flow? - to produce additional carbon dioxide - to produce additional ATP - to produce additional oxygen - to produce additional NADPH
to produce additional ATP
Which of the following statements describes a primary function of both alcohol fermentation and lactic acid fermentation? - to oxidize FADH2 to FAD - to reduce NAD+ to NADH - to oxidize NADH to NAD+ - to reduce FAD+ to FADH2
to reduce NAD+ to NADH
What is the primary function of the pigment molecules in a light-harvesting complex? - to transfer light energy to the reaction-center chlorophyll - to split water and release oxygen to the reaction-center chlorophyll - to synthesize ATP from ADP and Pi - to transfer electrons to the primary electron acceptor
to transfer light energy to the reaction-center chlorophyll
Which of the following correctly lists all of the energy-containing molecules produced by the catabolism of one molecule of glucose in glycolysis? - 6 CO2, 2 pyruvate, and 30 ATP - 2 FADH2, 2 pyruvate, and 4 ATP - 6 CO2, 2 pyruvate, and 2 ATP - 2 NAD+, 2 pyruvate, and 2 ATP - 2 NADH, 2 pyruvate, and 2 ATP
2 NADH, 2 pyruvate, and 2 ATP
For each mole of glucose (C6H12O6) completely oxidized by cellular respiration, how many moles of CO2 are released in the citric acid cycle ? - 6 - 2 - 3 - 12 - 4
4
Thinking about the environments where plant and animal cells typically exist, which of the following statements is correct? - Animal cells are generally in an isotonic solution, and plant cells are generally in a hypotonic solution. - Animal cells are generally in an isotonic solution, and plant cells are generally in a hypertonic solution. - Animal cells are generally in a hypotonic solution, and plant cells are generally in an isotonic solution. - Animal cells are generally in a hypertonic solution, and plant cells are generally in a hypotonic solution. - Animal cell are generally in a hypertonic solution, and plant cells are generally in an isotonic solution.
Animal cells are generally in an isotonic solution, and plant cells are generally in a hypotonic solution.
The enzyme rubisco plays a critical role in carbon fixation in which of the following types of plants? - C3, C4, and CAM plants - C3 and C4 plants only - C4 plants only - C4 and CAM plants only - C3 plants only
C3 plants only
Which of the following statements correctly summarizes a redox reaction that occurs in photosynthesis? - CO2 is reduced to form glucose. - Glucose is oxidized to form CO2. - CO2 is oxidized to form glucose. - Water is reduced to form O2. - O2 is oxidized to form water.
CO2 is reduced to form glucose.
Why is glycolysis described as having an energy investment phase and an energy payoff phase? - Early steps consume energy from ATP and NADH, and later steps store an increased amount of energy in ATP. - Early steps consume energy from ATP and NADH, and later steps store an equal amount of energy in ATP and NAD+. - Early steps consume energy from ATP and NADH, and later steps store an increased amount of energy in ATP and NADH. - Early steps consume energy from ATP, and later steps store an increased amount of energy in ATP and NADH. - Early steps consume energy from NADH, and later steps store an increased amount of energy in ATP and NADH.
Early steps consume energy from ATP, and later steps store an increased amount of energy in ATP and NADH.
Which of the following statements correctly describes a reaction associated with photosystem II? - The P680 chlorophyll donates a pair of electrons directly to NADP+, producing NADPH. - Light energy excites electrons in the thylakoid membrane electron transport chain. - Electrons are passed from the P680 chlorophyll to oxygen (O2). - Electrons released from the P680 chlorophyll are replaced by electrons derived from water.
Electrons released from the P680 chlorophyll are replaced by electrons derived from water. Submit
Which of the following is a statement of the first law of thermodynamics? - The entropy of the universe is constant. - The entropy of the universe is decreasing. - Energy cannot be created or destroyed. - Energy cannot be transferred or transformed.
Energy cannot be created or destroyed.
Which of the following statements regarding enzymes is true? - Enzymes increase the rate of a reaction by making the reaction more exergonic. - Enzymes increase the rate of a reaction by lowering the activation energy barrier. - Enzymes change the equilibrium point of the reactions they catalyze. - Enzymes increase the rate of a reaction by reducing the rate of reverse reactions.
Enzymes increase the rate of a reaction by lowering the activation energy barrier.
Which of the following statements about diffusion is correct? - It is very rapid over long distances. - It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration. - It is a passive process in which molecules move from a region of lower concentration to a region of higher concentration. - It requires an expenditure of energy by the cell. - It is an active process in which molecules move from a region of lower concentration to one of higher concentration.
It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.
Why might a severe fever result in death if it is not brought under control? - It may destroy the primary structure of cellular enzymes. - It may increase the rate of cellular chemical reactions. - It may alter the tertiary and quaternary structures of cellular enzymes. - It may result in consumption of excess ATP.
It may alter the tertiary and quaternary structures of cellular enzymes.
Which of the following statements correctly describes an activity directly associated with photosystem I? - It produces ATP by substrate-level phosphorylation. - It extracts hydrogen electrons released by the splitting of water. - It receives electrons from the electron transport chain associated with thylakoid membranes. - It produces O2.
It receives electrons from the electron transport chain associated with thylakoid membranes.
What compound provides the reducing power for the Calvin cycle reactions? - FAD - NADPH - CO2 - ATP - FADH2
NADPH
Photorespiration occurs when rubisco combines RuBP with which of the following molecules? - CO2 - H2O - glyceraldehyde 3-phosphate - O2
O2
Which of the following statements best represents the relationships between the light reactions and the Calvin cycle? - The light reactions provide ATP and NADPH to the Calvin cycle, and the Calvin cycle returns ADP, Pi, and NADP+ to the light reactions. - The light reactions provide ATP and NADPH to the carbon fixation step of the Calvin cycle, and the Calvin cycle provides water and electrons to the light reactions. - The light reactions provide the Calvin cycle with oxygen for carbon fixation, and the Calvin cycle provides the light reactions with sugars to produce ATP. - The light reactions supply the Calvin cycle with CO2 to produce sugars, and the Calvin cycle supplies the light reactions with sugars to produce ATP.
The light reactions provide ATP and NADPH to the Calvin cycle, and the Calvin cycle returns ADP, Pi, and NADP+ to the light reactions.
Which of the following is true of integral membrane proteins? - They are loosely bound to the surface of the bilayer. - They serve only a structural role in membranes. - They are not mobile within the bilayer. - They are usually transmembrane proteins.
They are usually transmembrane proteins.
Which of the following is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal? - Following transport of sodium ions into the cell, the cotransporter can also transport potassium ions out of the cell. - Transport of glucose against its concentration gradient provides energy for uptake of sodium ions against the electrochemical gradient. - Transport of sodium ions down their electrochemical gradient facilitates the transport of glucose against its concentration gradient. - Sodium and glucose bind to the same site on the cotransporter.
Transport of sodium ions down their electrochemical gradient facilitates the transport of glucose against its concentration gradient.
A reduction in the amount of NADP+ available in plant cells in the light will ultimately result in which of the following effects? - a decrease in the rate of linear electron flow - a decrease in the rate of cyclic electron flow - an increase in the rate of oxygen production - an increase in the rate of the Calvin cycle
a decrease in the rate of linear electron flow
