Biology 1107 Chapter 8
3) Which of the following involves a decrease in entropy? A) condensation reactions B) reactions that separate monomers C) depolymerization reactions D) hydrolysis reactions
A) condensation reactions
ATP (adenosine triphosphate)
ATP (adenosine triphosphate) is the cell's energy shuttle ATP is composed of ribose (a sugar), adenine (a nitrogenous base), and three phosphate groups
phosphorylated intermediate
ATP drives endergonic reactions by phosphorylation, transferring a phosphate group to some other molecule, such as a reactant The recipient molecule is now called a phosphorylated intermediate
The regeneration of ATP
ATP is a renewable resource that is regenerated by addition of a phosphate group to ADP The energy to phosphorylate ADP comes from catabolic reactions in the cell The ATP cycle is a revolving door through which energy passes during its transfer from catabolic to anabolic pathways
First law of thermodynamics
According to the first law of thermodynamics, the energy of the universe is constant Energy can be transferred and transformed, but it cannot be created or destroyed The first law is also called the principle of conservation of energy
Allosteric regulation
Allosteric regulation may either inhibit or stimulate an enzyme's activity Allosteric regulation occurs when a regulatory molecule binds to a protein at one site and affects the protein's function at another site
endergonic reaction (energy required, non spontaneous)
An energetic reactionabsorbs free energy from its surrounding and is non-spontaneous
exergonic reaction (energy released, spontaneous)
An exergonic reaction proceeds with a net release of free energy and is spontaneous
Anabolic pathways
Anabolic pathways consume energy to build complex molecules from simpler ones The synthesis of protein from amino acids is an example of anabolism
4)Which term most precisely describes the cellular process of breaking down large molecules into smaller ones? A) catabolism (catabolic pathways) B) metabolism C) anabolism (anabolic pathways) D) dehydration
A) catabolism (catabolic pathways)
2)Which of the following is an example of potential rather than kinetic energy? A) water rushing over Niagara Falls B) light flashes emitted by a firefly C) a molecule of glucose D) a crawling beetle foraging for food
C) a molecule of glucose
13) Allosteric enzyme regulation is usually associated with _____. A) feedback inhibition B) activating activity C) an enzyme with more than one subunit D) the need for cofactors
C) an enzyme with more than one subunit
active site
The active site is the region on the enzyme where the substrate binds
energy in ATP
The bonds between the phosphate groups of ATP's tail can be broken by hydrolysis Energy is released from ATP when the terminal phosphate bond is broken This release of energy comes from the chemical change to a state of lower free energy, not from the phosphate bonds themselves Transport and mechanical work in the cell are also powered by ATP hydrolysis ATP hydrolysis leads to a change in protein shape and binding ability
A cell does three main kinds of work:
chemical transport mechanical
catalyst
A catalyst is a chemical agent that speeds up a reaction without being consumed by the reaction
free energy
A living system's free energy is energy that can do work when temperature and pressure are uniform, as in a living cell The change in free energy (∆G) during a process is related to the change in enthalpy, or change in total energy (∆H), change in entropy (∆S), and temperature in Kelvin units (T) ∆G = ∆H - T∆S Only processes with a negative ∆G are spontaneous Spontaneous processes can be harnessed to perform work
metabolic pathway
A metabolic pathway begins with a specific molecule and ends with a product Each step is catalyzed by a specific enzyme
6)Which of the following is a statement of the first law of thermodynamics? A) Energy cannot be created or destroyed. B) The entropy of the universe is decreasing. C) The entropy of the universe is constant. D) Energy cannot be transferred or transformed.
A) Energy cannot be created or destroyed.
14) During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a ∆G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the ∆G for the new reaction? A) -40 kcal/mol B) -20 kcal/mol C) 0 kcal/mol D) +20 kcal/mol
B) -20 kcal/mol
10) The lock-and-key analogy for enzymes applies to the specificity of enzymes _____. A) as they form their tertiary and quaternary structure B) binding to their substrate C) interacting with water D) interacting with ions
B) binding to their substrate
12) A noncompetitive inhibitor decreases the rate of an enzyme reaction by _____. A) binding at the active site of the enzyme B) changing the shape of the enzyme's active site C) changing the free energy change of the reaction D) acting as a coenzyme for the reaction
B) changing the shape of the enzyme's active site
5)Anabolic pathways _____. A) are usually highly spontaneous chemical reactions B) consume energy to build up polymers from monomers C) release energy as they degrade polymers to monomers D) consume energy to decrease the entropy of the organism and its environment
B) consume energy to build up polymers from monomers
8)Catabolic pathways _____. A) combine molecules into more energy-rich molecules B) supply energy, primarily in the form of ATP, for the cell's work C) are endergonic D) are spontaneous and do not need enzyme catalysis
B) supply energy, primarily in the form of ATP, for the cell's work
Bioenergetics
Bioenergetics is the study of how energy flows through living organisms
7)Which of the following statements is a logical consequence of the second law of thermodynamics? A) If the entropy of a system increases, there must be a corresponding decrease in the entropy of the universe. B) If there is an increase in the energy of a system, there must be a corresponding decrease in the energy of the rest of the universe. C) Every chemical reaction must increase the total entropy of the universe. D) Energy can be transferred or transformed, but it cannot be created or destroyed.
C) Every chemical reaction must increase the total entropy of the universe.
9) Which of the following is true of enzymes? A) Enzyme function is increased if the 3- D structure or conformation of an enzyme is altered. B) Enzyme function is independent of physical and chemical environmental factors such as pH and temperature. C) Enzymes increase the rate of chemical reaction by lowering activation energy barriers. D) Enzymes increase the rate of chemical reaction by providing activation energy to the substrate.
C) Enzymes increase the rate of chemical reaction by lowering activation energy barriers.
1)Which of the following is true of metabolism in its entirety in all organisms? A) Metabolism depends on a constant supply of energy from food. B) Metabolism uses all of an organism's resources. C) Metabolism consists of all the energy transformation reactions in an organism. D) Metabolism manages the increase of entropy in an organism.
C) Metabolism consists of all the energy transformation reactions in an organism.
catabolic pathways
Catabolic pathways release energy by breaking down complex molecules into simpler compounds Cellular respiration, the breakdown of glucose in the presence of oxygen, is an example of a pathway of catabolism A catabolic pathway in a cell releases free energy in a series of reactions Catabolism is exergonic, energy-releasing process
Cofactors
Cofactors are nonprotein enzyme helpers Cofactors may be inorganic (such as a metal in ionic form) or organic An organic cofactor is called a coenzyme Coenzymes include vitamins
competitive inhibitors
Competitive inhibitors bind to the active site of an enzyme, competing with the substrate
cooperatively
Cooperativity is a form of allosteric regulation that can amplify enzyme activity One substrate molecule primes an enzyme to act on additional substrate molecules more readily Cooperativity is allosteric because binding by a substrate to one active site affects catalysis in a different active site
11) You have discovered an enzyme that can catalyze two different chemical reactions. Which of the following is most likely to be correct? A) The enzyme contains α-helices and β-pleated sheets. B) The enzyme is subject to competitive inhibition and allosteric regulation. C) Two types of allosteric regulation occur: The binding of one molecule activates the enzyme, while the binding of a different molecule inhibits it. D) Either the enzyme has two distinct active sites or the reactants involved in the two reactions are very similar in size and shape.
D) Either the enzyme has two distinct active sites or the reactants involved in the two reactions are very similar in size and shape.
Second law of thermodynamics
During every energy transfer or transformation, some energy is unusable, and is often lost as heat According to the second law of thermodynamics Every energy transfer or transformation increases the entropy (disorder) of the universe
Energy
Energy is the capacity to cause change Energy exists in various forms, some of which can perform work
how enzymes speed up reactions
Enzymes catalyze reactions by lowering the EA barrier Enzymes do not affect the change in free energy (∆G); instead, they hasten reactions that would occur eventually
enzyme
Enzymes speed up metabolic reactions by lowering energy barriers. An enzyme is a catalytic protein. Hydrolysis of sucrose by the enzyme sucrase is an example of an enzyme-catalyzed reaction
activation energy
Every chemical reaction between molecules involves bond breaking and bond forming The initial energy needed to start a chemical reaction is called the free energy of activation, or activation energy (EA) Activation energy is often supplied in the form of thermal energy that the reactant molecules absorb from their surroundings
Free Energy, Stability, and Equilibrium
Free energy is a measure of a system's instability, its tendency to change to a more stable state During a spontaneous change, free energy decreases and the stability of a system increases Equilibrium is a state of maximum stability A process is spontaneous and can perform work only when it is moving toward equilibrium
Catalysis in the Enzyme's active site
In an enzymatic reaction, the substrate binds to the active site of the enzyme The active site can lower an EA barrier by Orienting substrates correctly Straining substrate bonds Providing a favorable microenvironment Covalently bonding to the substrate
feedback inhibition
In feedback inhibition, the end product of a metabolic pathway shuts down the pathway Feedback inhibition prevents a cell from wasting chemical resources by synthesizing more product than is needed
induced fit
Induced fit of a substrate brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction
Forms of energy
Kinetic energy is energy associated with motion Heat (thermal energy) is kinetic energy associated with random movement of atoms or molecules Potential energy is energy that matter possesses because of its location or structure Chemical energy is potential energy available for release in a chemical reaction Energy can be converted from one form to another
Metabolism (transforms matter and energy)
Metabolism is the totality of an organism's chemical reactions Metabolism is an emergent property of life that arises from orderly interactions between molecules
noncompetitive inhibitors
Noncompetitive inhibitors bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective Examples of any inhibitors include toxins, poisons, pesticides, and antibiotics
Spontaneous processes
Spontaneous processes occur without energy input; they can happen quickly or slowly For a process to occur without energy input, it must increase the entropy of the universe
enzyme-substrate complex
The enzyme binds to its substrate, forming an enzyme-substrate complex The reaction catalyzed by each enzyme is very specific
substrate
The reactant that an enzyme acts on is called the enzyme's substrate
Thermodynamics
Thermodynamics is the study of energy transformations An isolated system, such as that approximated by liquid in a thermos, is unable to exchange energy or matter with its surroundings In an open system, energy and matter can be transferred between the system and its surroundings Organisms are open systems
energy coupling
To do work, cells manage energy resources by energy coupling, the use of an exergonic process to drive an endergonic one Most energy coupling in cells is mediated by ATP