BIO MIDTERM
On food packages, to what does the term ʺinsoluble fiberʺ refer? A) cellulose B) polypeptides C) starch D) amylopectin E) chitin
A
The bonding of two amino acid molecules to form a larger molecule requires A) the release of a water molecule. B) the release of a carbon dioxide molecule. C) the addition of a nitrogen atom. D) the addition of a water molecule. E) both B and C
A
The enzyme amylase can break glycosidic linkages between glucose monomers only if the monomers are the α form. Which of the following could amylase break down? A) glycogen B) cellulose C) chitin D) A and B only E) A, B, and C
A
The enzyme amylase can break glycosidic linkages between glucose monomers only if the monomers are the α form. Which of the following could amylase break down? A) glycogen, starch, and amylopectin B) glycogen and cellulose C) cellulose and chitin D) starch and chitin E) starch, amylopectin, and cellulose
A
The structural level of a protein least affected by a disruption in hydrogen bonding is the A) primary level. B) secondary level. C) tertiary level. D) quaternary level. E) All structural levels are equally affected.
A
Which of the following best describes the flow of information in eukaryotic cells? A) DNA → RNA → proteins B) RNA → proteins → DNA C) proteins → DNA → RNA D) RNA → DNA → proteins E) DNA → proteins → RNA
A
Which of the following is not a polymer? A) glucose B) starch C) cellulose D) chitin E) DNA
A
Which of the following is true of both starch and cellulose? A) They are both polymers of glucose. B) They are geometric isomers of each other. C) They can both be digested by humans. D) They are both used for energy storage in plants. E) They are both structural components of the plant cell wall.
A
Which of the following statements is false for the class of biological molecules known as lipids? A) They are soluble in water. B) They are an important constituent of cell membranes. C) They contain more energy than proteins and carbohydrates. D) They are not true polymers. E) They contain waxes and steroids.
A
ll of the following are polysaccharides except A) glycogen B) starch C) chitin D) cellulose E) amylopectin
A
covalent
A chemical bond that involves sharing a pair of electrons between atoms in a molecule -where the energy is stored ****very important -there is a small diff. of electronegativity in bonds -important in macromolec. func. & interaction (ex: protein & DNA (hydrogen bonds), makes more strands )
methyl group
A chemical group consisting of a carbon atom bonded to three hydrogen atoms.
phosphate group
A chemical group consisting of a phosphorus atom bonded to four oxygen atoms; important in energy transfer.
hydroxyl group
A chemical group consisting of an oxygen atom bonded to a hydrogen atom.
dehydration reaction
A chemical reaction in which molecules combine by removing water -synthesizing a polymer (Dehydration removes H2O molecule, forming a new bond, similar to condensation)
Disaccharide
A double sugar, consisting of two monosaccharides joined by dehydration synthesis.
saturated fatty acid
A fatty acid in which all carbons in the hydrocarbon tail are connected by single bonds, thus maximizing the number of hydrogen atoms that can attach to the carbon skeleton. -linear structure (stearic acid, solid (butter), fats), more organized
chemical energy
A form of potential energy that is stored in chemical bonds between atoms.
carboxyl group
A functional group present in organic acids and consisting of a single carbon atom double-bonded to an oxygen atom and also bonded to a hydroxyl group.
Solution
A homogeneous mixture of two or more substances
Which of the following can be attributed to water's high specific heat?
A lake heats up more slowly than the air around it.
cholesterol
A lipid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids.
surface tension
A measure of how difficult it is to stretch or break the surface of a liquid
amphipathic
A molecule that has both a hydrophilic region and a hydrophobic region. -both hydrophilic & phobic
Phospholipids
A molecule that is a constituent of the inner bilayer of biological membranes, having a polar, hydrophilic head and a nonpolar, hydrophobic tail. -imp. for cell membranes (choline, phosphate, glycerol) -two chains, kinky & straight -diversity in polar head group -the fatty acid tails turn into a phospholipid bilayer —> hydrophilic head break off
endergonic reaction
A non-spontaneous chemical reaction in which free energy is absorbed from the surroundings.
catabolic
A process in which large molecules are broken down ---> useful for energy
anabolic
A process in which large molecules are built from small molecules
spontaneous process
A process that occurs without an overall input of energy; a process that is energetically favorable.
unsaturated fatty acid
A solution that contains less than the maximum amount of dissolved solute in a concentration. -kinky structure (oleic acid, oily), hydrophobic interactions -double bonds in its skeleton
exergonic reaction
A spontaneous chemical reaction in which there is a net release of free energy.
disulfide bridge
A strong covalent bond formed when the sulfur of one cysteine monomer bonds to the sulfur of another cysteine monomer. -conformation relys on amino acid sequence & protein's lowest energy state -this provides the max. # of Hbonds b/n neighboring amino acid
cellulose
A substance (made of sugars) that is common in the cell walls of many organisms -a major component of the tough wall of plant cells -Like starch, cellulose is a polymer of glucose, but the glycosidic linkages differ -The difference is based on two ring forms for glucose: alpha and beta -straight & unbranched structure
compound
A substance made up of atoms of two or more different elements joined by chemical bonds
element
A substance that cannot be broken down into simpler substances
noncompetitive inhibitor
A substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing its conformation so that it no longer binds to the substrate.
homeostasis
A tendency to maintain a balanced or constant internal state; the regulation of any aspect of body chemistry, such as blood glucose, around a particular level
glycerol
A three-carbon alcohol to which fatty acids are covalently bonded to make fats and oils.
indeterminate growth
A type of growth characteristic of plants, in which the organism continues to grow as long as it lives.
enzyme
A type of protein that speeds up a chemical reaction in a living thing
joule
A unit of work equal to one newton-meter
ATP
(adenosine triphosphate) main energy source that cells use for most of their work -also used for biosynthesis: body growth & repair, synthesis of storage material (fat & gamete production) -generates heat -phosphoanhydride bonds store the energy, have high energy -phosphoanhydride bonds break down w another phosphate group during energy transfer ATP + H2O ⇌ ADP + Pi
Diversity of sugars is achieved how?
-# of carbons -isomers -derivatives —> addition of side groups
The compound CaSO4 ionizes into a calcium ion and a sulfate ion (SO4). Calcium has two electrons in its outer shell. Upon ionization, what would you expect the charge on the sulfate ion to be?
-2
How to make or break a polysaccharide
-2 monosaccharides-> w a reactive b/n disaccharides -condensation: water expelled (breaks it) -hydrolisis: water consumed (makes it)
polypeptide bond
-20^n = # of amino acids in polypeptide -natural selection selects more favorable amino acid sequences that benefit organism -amino acid sequences also determine conformation & folding of protein
starch
-A storage polysaccharide in plants consisting entirely of glucose. -Plants store surplus starch as granules within chloroplasts and other plastids -The simplest form of starch is amylose -largely helical
ATP hydrolysis
-ATP is converted to ADP & phosphate energized myosin heads (removal of phosphate) need energy ATP + H2O ⇌ ADP + Pi
Free Energy, Stability, and Equilibrium
-Organisms live at the expense of free energy -During a spontaneous change -Free energy decreases and the stability of a system increases -ΔG= Gfinal -Ginitial
Can cows & other herbivores digest cellulose?
-Some microbes use enzymes to digest cellulose -Many herbivores, from cows to termites, have symbiotic relationships with these microbes
Why can't humans digest cellulose?
-can't break beta 1, 4 linkage; don't have cellulase -The cellulose in human food passes through the digestive tract as "insoluble fiber"
∆g
-change in Gibbs free energy during a reaction = Gproducts - Greactants -G > 0 ; reaction isn't spontaneous -G < 0 ; reaction is spontaneous -standard Gibbs free energy change (pH 7.0) not under cellular conditions -Gibbs free energy change is dependent of (products)/(reactants), determines how far equilibrium is from reaction Gibbs free energy change determines a reaction's direction coupling of reactions Energy is released from ATP when it breaks off the terminal phosphate bond
Triacylglycerols
-composed of 3 fatty acids bonded by ester linkages to glycerol - nonpolar and hydrophobic -used for energy storage -more reduced than carbohydrates --> oxidation of TAG yields twice more energy -stored as fat globules in adipose tissue
fitness
-contribution an individual makes (# of offspring) to the next generation relative to every other individual in the population. -Ability of an organism to survive and reproduce in its environment
REDOX
-coupled reactions w transfer of pair of e-s b/n molecules -Oxydation & Reduction
diversity in sugars is achieved how?
-diff. spatial arrangement of atoms -sugar derivatives -these small diffs. make only minor changes in the chemical properties of the sugars. But they are recongnized by enzymes and other imp. protiens & can have special biological effects
non-covalent bond
-does not involve the sharing of electrons, but rather involves more dispersed variations of electromagnetic interactions between molecules or within a molecule -electrostatic bonds (ionic), hydrogen bonds, van der Waals attractions (specific distance & time)
fatty acids & lipids
-glycerol & fatty acids linked to each other -chemical nature of FAs: how they form lipids, sources of diversity -MOST ENERGY RICH
entropy
-measure of disorder in a system, tendency for ^ in entropy (2nd law thermodynamics) -inc. disorder continues w equilibrium in environment -cells are open systems => no equilibrium
factors affecting total energy intake
-organism size -environmental conditions -food/prey abundance -predators present -food's nutritional value
resource allocation
-organisms must acquire energy from environment & allocate it to various life processes -affects their evolutionary fitness (size of organism, environmental cons., gen. abundance of food/prey, presence of predators, nutritional value of food)
affinity constant
-probability the enzime will find to substrate & reaction will go forward
foraging strategy
-specialist (eat a specific type of food) vs. generalist (eats many types of food)
carbohydrates
-sugars, monosaccharides: the building blocks -The simplest carbohydrates are monosaccharides, or simple sugars -Carbohydrate macromolecules are polysaccharides, polymers composed of many sugar building blocks
enzyme-substrate complex
-temporary complex formed when an enzyme binds to its substrate molecule(s) -enzyme binds to its substrate and forms this
Four Ways that Carbon Skeletons Can Vary:
1. length 2. branching 3. double bond position 4. presence of rings
How many electrons are involved in a single covalent bond?
2
Phosphorus-32 (radioactive) has __________ than phosphorus-35 (normal)
3 fewer neutrons
How many electrons would be present in the valence shell of a sulfur atom (atomic number 16, mass number 32)?
6 electrons
A neutral atom of chlorine has an atomic number of 17. It has __________ electrons in its third shell.
7
An atom that normally has __________ in its outer shell would NOT tend to form chemical bonds with other atoms
8 electrons
A particular carbon isotope has an atomic number of 6 and an atomic mass of 14. The respective number of neutrons, protons, and electrons that this carbon isotope has is __________.
8,6,6
energy in regards to heat loss & surface area/volume
<—heat loss surface area/volume ——>
Which of the following statements about allosteric proteins is/are true?
All of the first three listed responses are correct.
Which of the following four statements, if any, is true regarding essential elements and living organisms?
Although all forms of life require iron, other elements are required only by certain species.
What is the role of van der Waals interactions in biological molecules?
Although they are weak bonds, van der Waals interactions help to reinforce the three-dimensional shapes of large molecules.
calorie
Amount of energy needed to raise temperature 1 gram of water 1 degree C
adhesion
An attraction between molecules of different substances
Which of the following statements about enzymes is INCORRECT?
An enzyme is consumed during the reaction it catalyzes. Correct. If enzymes were consumed during the reaction they catalyzed, they would not be able to act as a catalyst. This statement is incorrect.
glycogen
An extensively branched glucose storage polysaccharide found in the liver and muscle of animals; the animal equivalent of starch.
hemoglobin
An iron-containing protein in red blood cells that reversibly binds oxygen.
mitochondria
An organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur. -phospholipids help w its impermeability
myoglobin
An oxygen-storing, pigmented protein in muscle cells. -70% amino acids in alpha helices
BIOLOGY CHAPTER 8 PRACTICE TEST Introduction to Metabolism Which of the following correctly states the relationship between anabolic and catabolic pathways?
Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways. Correct. The synthesis of complex molecules in anabolic pathways requires an input of energy from catabolic pathways.
matter
Anything that has mass and takes up space
All of the following contain amino acids except A) hemoglobin. B) cholesterol. C) antibodies. D) enzymes. E) insulin.
B
All of the following statements concerning saturated fats are true except A) They are more common in animals than in plants. B) They have multiple double bonds in the carbon chains of their fatty acids. C) They generally solidify at room temperature. D) They contain more hydrogen than saturated fats having the same number of carbon atoms. E) They are one of several factors that contribute to atherosclerosis.
B
Enzymes that break down DNA catalyze the hydrolysis of the covalent bonds that join nucleotides together. What would happen to DNA molecules treated with these enzymes? A) The two strands of the double helix would separate. B) The phosphodiester linkages between deoxyribose sugars would be broken. C) The purines would be separated from the deoxyribose sugars. D) The pyrimidines would be separated from the deoxyribose sugars. E) All bases would be separated from the deoxyribose sugars.
B
If one strand of a DNA molecule has the sequence of bases 5ʹATTGCA3ʹ, the other complementary strand would have the sequence A) 5ʹTAACGT3ʹ. B) 3ʹTAACGT5ʹ. C) 5ʹUAACGU3ʹ. D) 3ʹUAACGU5ʹ. E) 5ʹUGCAAU3ʹ.
B
Of the following functions, the major purpose of RNA is to A) transmit genetic information to offspring. B) function in the synthesis of protein. C) make a copy of itself, thus ensuring genetic continuity. D) act as a pattern or blueprint to form DNA. E) form the genes of higher organisms.
B
Polysaccharides, lipids, and proteins are similar in that they A) are synthesized from monomers by the process of hydrolysis. B) are synthesized from monomers by dehydration reactions. C) are synthesized as a result of peptide bond formation between monomers. D) are decomposed into their subunits by dehydration reactions. E) all contain nitrogen in their monomer building blocks.
B
Which of the following are nitrogenous bases of the purine type? A) cytosine and guanine B) guanine and adenine C) adenine and thymine D) thymine and uracil E) uracil and cytosine
B
Which of the following are nitrogenous bases of the pyrimidine type? A) guanine and adenine B) cytosine and uracil C) thymine and guanine D) ribose and deoxyribose E) adenine and thymine
B
Which of the following is a diverse group of hydrophobic molecules? A) carbohydrates B) lipids C) proteins D) nucleic acids
B
Which of the following statements concerning unsaturated fats is true? A) They are more common in animals than in plants. B) They have double bonds in the carbon chains of their fatty acids. C) They generally solidify at room temperature. D) They contain more hydrogen than saturated fats having the same number of carbon atoms. E) They have fewer fatty acid molecules per fat molecule.
B
Why are human sex hormones considered to be lipids? A) They are essential components of cell membranes. B) They are steroids, which are not soluble in water. C) They are made of fatty acids. D) They are hydrophilic compounds. E) They contribute to atherosclerosis.
B
cells
Basic unit of life
induced fit
Brings chemical groups of the active site into positions that enhance their ability to catalyze the chemical reaction.
Enzymes are A) carbohydrates. B) lipids. C) proteins. D) nucleic acids.
C
Humans can digest starch but not cellulose because A) the monomer of starch is glucose, while the monomer of cellulose is galactose. B) humans have enzymes that can hydrolyze the beta (β) glycosidic linkages of starch but not the alpha (α) glycosidic linkages of cellulose. C) humans have enzymes that can hydrolyze the alpha (α) glycosidic linkages of starch but not the beta (β) glycosidic linkages of cellulose. D) humans harbor starch-digesting bacteria in the digestive tract. E) the monomer of starch is glucose, while the monomer of cellulose is maltose.
C
The molecular formula for glucose is C6H12O6. What would be the molecular formula for a polymer made by linking ten glucose molecules together by dehydration reactions? A) C60H120O60 B) C6H12O6 C) C60H102O51 D) C60H100O50 E) C60H111O51
C
What is the chemical mechanism by which cells make polymers from monomers? A) phosphodiester linkages B) hydrolysis C) dehydration reactions D) ionic bonding of monomers E) the formation of disulfide bridges between monomers
C
Which of the following is true regarding saturated fatty acids? A) They are the predominant fatty acid in corn oil. B) They have double bonds between carbon atoms of the fatty acids. C) They are the principal molecules in lard and butter. D) They are usually liquid at room temperature. E) They are usually produced by plants.
C
Which of the following hydrocarbons has a double bond in its carbon skeleton?
C2H4
Lactose, a sugar in milk, is composed of one glucose molecule joined by a glycosidic linkage to one galactose molecule. How is lactose classified? A) as a pentose B) as a hexose C) as a monosaccharide D) as a disaccharide E) as a polysaccharide
D
Misfolding of polypeptides is a serious problem in cells. Which of the following diseases are associated with an accumulation of misfolded proteins? A) Alzheimerʹs B) Parkinsonʹs C) diabetes D) A and B only E) A, B, and C
D
Which of the following is an example of hydrolysis? A) the reaction of two monosaccharides, forming a disaccharide with the release of water B) the synthesis of two amino acids, forming a peptide with the release of water C) the reaction of a fat, forming glycerol and fatty acids with the release of water D) the reaction of a fat, forming glycerol and fatty acids with the utilization of water E) the synthesis of a nucleotide from a phosphate, a pentose sugar, and a nitrogenous base with the production of a molecule of water
D
Which of the following is true of cellulose? A) It is a polymer composed of sucrose monomers. B) It is a storage polysaccharide for energy in plant cells. C) It is a storage polysaccharide for energy in animal cells. D) It is a major structural component of plant cell walls. E) It is a major structural component of animal cell plasma membranes.
D
Which of the following pairs of base sequences could form a short stretch of a normal double helix of DNA? A) 5ʹ-purine-pyrimidine-purine-pyrimidine-3ʹ with 3ʹ-purine-pyrimidine-purine-pyrimidine-5ʹ B) 5ʹ-A-G-C-T-3ʹ with 5ʹ-T-C-G-A-3ʹ C) 5ʹ-G-C-G-C-3ʹ with 5ʹ-T-A-T-A-3ʹ D) 5ʹ-A-T-G-C-3ʹ with 5ʹ-G-C-A-T-3ʹ E) All of these pairs are correct.
D
Which term includes all others in the list? A) monosaccharide B) disaccharide C) starch D) carbohydrate E) polysaccharide
D
Which part of the equation Delta G = Delta H - T Delta S tells you if a process is spontaneous?
Delta G Correct. In any spontaneous process, the free energy of a system decreases. The change in free energy equals the change in total energy minus the change in entropy times the temperature.
If, during a process, the system becomes more ordered, then
Delta S is negative Correct. In an endergonic reaction, in which order is increased, the change in entropy, symbolized by Delta S, is negative.
When one molecule is broken down into six component molecules, which of the following will always be true?
Delta S is positive. Correct. The large increase in disorder associated with this reaction means that entropy Delta S increases.
In the double helix structure of nucleic acids, cytosine hydrogen bonds to A) deoxyribose. B) ribose. C) adenine. D) thymine. E) guanine.
E
The element nitrogen is present in all of the following except A) proteins. B) nucleic acids. C) amino acids. D) DNA. E) monosaccharides.
E
The function of each protein is a consequence of its specific shape. What is the term used for a change in a proteinʹs three-dimensional shape or conformation due to disruption of hydrogen bonds, disulfide bridges, or ionic bonds? A) hydrolysis B) stabilization C) destabilization D) renaturation E) denaturation
E
The hydrogenation of vegetable oil results in which of the following? A) saturated fats and unsaturated fats with trans double bonds B) an increased contribution to artherosclerosis C) the oil (fat) being a solid at room temperature D) A and C only E) A, B, and C
E
Which of the following best summarizes the relationship between dehydration reactions and hydrolysis? A) Dehydration reactions assemble polymers, and hydrolysis reactions break down polymers. B) Macromolecular synthesis occurs through the removal of water and digestion occurs through the addition of water. C) Dehydration reactions can occur only after hydrolysis. D) Hydrolysis creates monomers, and dehydration reactions break down polymers. E) A and B are correct.
E
behavioral fever
Ectotherms (like lizards) choose warmer microhabitats when they have an infection
valence
Electrons on the outermost energy level of an atom
Which of the following states the relevance of the first law of thermodynamics to biology?
Energy can be freely transformed among different forms as long as the total energy is conserved. Correct. The first law of thermodynamics states that energy can be transformed but can be neither created nor destroyed.
If the entropy of a living organism is decreasing, which of the following is most likely to be occurring simultaneously?
Energy input into the organism must be occurring to drive the decrease in entropy. Correct. If the entropy is decreasing, this would tend to make the free energy change associated with this positive. Thus, an input of energy would be required to make this decrease in entropy occur.
activation energy
Energy needed to get a reaction started
Which of the following statements about enzyme function is correct?
Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output. Correct. Enzymes lower the activation energy barrier of a reaction but do not change the free energy of the products.
Which of the following statements about enzymes is/are true?
Enzymes speed up the rate of the reaction without changing the DG for the reaction. Correct. Enzymes speed up reactions by lowering the activation energy barrier for the reaction. Enzymes cannot change the DG for the reaction.
second law of thermodynamics
Every energy transfer or transformation increases the entropy of the universe.
Consider this statement: Oxygen is not a greenhouse gas; therefore, gases containing oxygen—such as ozone, nitrous oxide, and carbon dioxide—are not greenhouse gases either. Which of the following is a valid response to this statement?
False. Compounds can have emergent properties that are very different from those of the elements that form them.
Consider this statement: Concentrations of trace elements in an environment above what is required by organisms generally have no effect on those organisms. Which of the following is a valid response to this statement?
False. Elevated concentrations of some trace elements such as cobalt and chromium can be toxic.
bioenergetics
Flow of energy through an animal. Limits its behavior, growth, reproduction.
ionic
Formed when one or more electrons are transferred from one atom to another -a big diff. in degree of electronegativity -electrostatic bonds (ionic), hydrogen bonds, van der Waals attractions (specific distance & time) -are important in macromolecular structure and molecular interactions
thermal energy
Heat energy
Under most conditions, the supply of energy by catabolic pathways is regulated by the demand for energy by anabolic pathways. Considering the role of ATP formation and hydrolysis in energy coupling of anabolic and catabolic pathways, which of the following statements is most likely to be true?
High levels of ADP result in allosteric activation of catabolic pathways. Correct. In this case, high demand for energy by anabolic pathways uses ATP, increasing the level of ADP, which in turn increases the supply of ATP from catabolic pathways. -Glutamate + NH3
coenzyme
If the cofactor is an organic molecule.
When 1 mole of ATP is hydrolyzed in a test tube without an enzyme, about twice as much heat is given off as when 1 mole of ATP is hydrolyzed in a cell. Which of the following best explains these observations?
In the cell, the hydrolysis of ATP is coupled to other endergonic reactions. Correct. The coupling of ATP to other endergonic processes in cells means that less of the free energy is released as heat. When ATP is hydrolyzed without this coupling, all of the energy is released as heat.
free energy
Measures the portion of a system's energy that can perform work when temperature and pressure are uniform throughout the system, as in a living cell. -catabolic pathway release reactions from free energy ADP + Pi -> ATP -equation: ΔG = ΔH - TΔS -Glutamate change
unfolded protein response
Molecular program triggered by the accumulation of misfolded proteins in the endoplasmic reticulum. Allows cells to expand the endoplasmic reticulum and produce more of the molecular machinery needed to restore proper protein folding and processing.
What do the sign and magnitude of the Delta G of a reaction tell us about the speed of the reaction?
Neither the sign nor the magnitude of Delta G has anything to do with the speed of a reaction. Correct. The speed of a reaction is determined by the activation energy barrier of the reaction and the temperature, which determines how many reactants have the energy to overcome the barrier.
Which of the following environments or actions would NOT affect the rate of an enzyme reaction?
None of the listed responses is correct. Correct. Changes in temperature, substrate concentration, and pH are all likely to affect enzyme activity.
structural isomer
One of several compounds that have the same molecular formula but differ in the covalent arrangements of their atoms.
Organisms are described as thermodynamically open systems. Which of the following statements is consistent with this description?
Organisms acquire energy from, and lose energy to, their surroundings. Correct. Open systems are those in which energy and materials can be exchanged between the system and its surroundings.
competitive inhibitors
Reduce the productivity of enzymes by blocking substrates from entering active sites.
Choose the term that correctly describes the relationship between these two sugar molecules
Structural isomers
Succinylcholine is structurally almost identical to acetylcholine. If succinylcholine is added to a mixture that contains acetylcholine and the enzyme that hydrolyzes acetylcholine (but not succinylcholine), the rate of acetylcholine hydrolysis is decreased. Subsequent addition of more acetylcholine restores the original rate of acetylcholine hydrolysis. Which of the following correctly explains this observation?
Succinylcholine must be a competitive inhibitor with acetylcholine. Correct. Competitive inhibition occurs when a molecule mimics the substrate by competing with it at the active site.
biologically prevalent atoms (SPONCH)
Sulphur, Phosphorus, Oxygen, Nitrogen, Carbon, Hydrogen
Which of these statements about enzyme inhibitors is true?
The action of competitive inhibitors may be reversible or irreversible. Correct. Competitive inhibitors that bind covalently to the enzyme would be irreversible, and those that bind weakly would be reversible.
Which of the following statements about the active site of an enzyme is correct?
The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits. Correct. Only a restricted region of an enzyme molecule (the active site) binds to the substrate. Usually, the active site is formed by only a few of the amino acids, with the rest of the protein molecule providing a framework that reinforces the configuration of the active site.
Which of the following is an example of the second law of thermodynamics as it applies to biological reactions?
The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water. Correct. The second law of thermodynamics states that every energy transformation makes the universe more disordered—carbon dioxide and water are more disordered than glucose.
The binding of an allosteric inhibitor to an enzyme causes the rate of product formation by the enzyme to decrease. Which of the following best explains why this decrease occurs?
The allosteric inhibitor causes a structural change in the enzyme that prevents the substrate from binding at the active site. Correct. In general, any allosteric regulator functions by changing the structure of the enzyme to change the ability of the active site to bind the substrate.
heat of vaporization
The amount of energy required for the liquid at its boiling point to become a gas
specific heat
The amount of energy required to raise the temperature of 1 gram of a substance by 1 degree celcius
Consider a hypothetical atom with an atomic number of 4 and a net charge of +1. How many neutrons does this ion have?
The answer cannot be determined from the information provided. Correct. All the atoms of an element have the same number of protons, but some atoms have different numbers of neutrons than other atoms of the same element; therefore, the atoms have different mass numbers. Without the mass number (number of protons + neutrons), it is not possible to determine the number of neutrons.
Which statement is true of all atoms that are anions?
The atom has more electrons than protons.
Copper has an atomic number of 29 and a mass number of 64. What would result if an uncharged copper atom lost two electrons?
The atomic number would remain 29, the mass number would remain 64, and the atom would be a cation with a +2 charge.
peptide bonds
The bonds connecting amino acids together to form polypeptide chains. -polymer of amino acids (dipeptide, tripeptide, oligopeptide (short), polypeptide (long)), carboxyl groups, they form links to create polypeptides -formed by dehydration reactions -each have unique amino acid sequences, w a carboxyl group (C terminus) & amino end (N terminus; its first group is free) -read from N'—-> C' (see where there are bonds or not)
According to the second law of thermodynamics, which of the following is true?
The decrease in entropy associated with life must be compensated for by increased entropy in the environment in which life exists. Correct. The second law of thermodynamics demands that total entropy increase with any reaction.
heat
The energy transferred between objects that are at different temperatures
What is meant by the "induced fit" of an enzyme?
The enzyme changes its shape slightly as the substrate binds to it. Correct. The enzyme changes slightly to bind to the substrate and catalyze the reaction.
Which of the following statements correctly describe(s) the role or roles of heat in biological reactions?
The first and second choices are correct. Correct. As the heat energy in a system increases, so does the kinetic energy of the reactants. As the kinetic energy of the reactants increases, the reactants are more likely to interact, with each other directly, or with the active site of an enzyme. Subsequently, the reaction rate would increase.
Above a certain substrate concentration, the rate of an enzyme-catalyzed reaction drops as the enzymes become saturated. Which of the following would lead to a faster conversion of substrate into product under these saturated conditions?
The first and second listed responses are correct. Correct. Either increasing the enzyme concentration or slightly increasing the temperature will increase the rate of product formation.
Metabolic pathways in cells are typically far from equilibrium. Which of the following processes tend(s) to keep these pathways away from equilibrium?
The first and second listed responses are correct. Correct. Pathways can be displaced from equilibrium either by adding free energy or by removal of the products of the pathway by other reactions.
quarternary structure
The fourth level of protein structure; the shape resulting from the association of two or more polypeptide subunits. -identical or nonidentical subunits, or covalent or non-covalent bonds
Which of the following best characterizes the role of ATP in cellular metabolism?
The free energy released by ATP hydrolysis may be coupled to an endergonic process via the formation of a phosphorylated intermediate. Correct. This is one way a cell can use an exergonic reaction to drive an endergonic reaction.
rubisco
The most abundant protein on earth. Performs Carbon Fixation in the Calvin Cycle.
The cities of Portland, Oregon, and Minneapolis, Minnesota, are at about the same latitude, but Minneapolis has much hotter summers and much colder winters than Portland. Why?
The ocean near Portland moderates the temperature.
active site
The part of an enzyme or antibody where the chemical reaction occurs.
1st law thermodynamics
The principle of conservation of energy. Energy can be transferred and transformed, but it cannot be created or destroyed.
evaporative cooling
The process in which the surface of an object becomes cooler during evaporation, a result of the molecules with the greatest kinetic energy changing from the liquid to the gaseous state.
Which of the following statements correctly describes any chemical reaction that has reached equilibrium?
The rates of the forward and reverse reactions are equal.
Molecules A and B contain 110 kcal/mol of free energy, and molecules B and C contain 150 kcal/mol of energy. A and B are converted to C and D. What can be concluded?
The reaction that proceeds to convert A and B to C and D is endergonic; the products are more organized than the reactants. Correct. C and D contain more energy than do A and B; therefore they are more organized and their construction required an input of energy.
Which action could produce a carbonyl group?
The replacement of the -OH of a carboxyl group with a hydrogen
Organic chemistry is currently defined as
The study of carbon compunds
molecular mass
The sum of the masses of all the atoms in a molecule
tertiary structure
The third level of protein structure; the overall, three-dimensional shape of a polypeptide due to interactions of the R groups of the amino acids making up the chain.
energy coupling
The use of an exergonic process to drive an endergonic one.
Which of the following statements is true about chemical reactions?
They involve the making and breaking of chemical bonds.
Which of the following statements correctly describes some aspect of ATP hydrolysis being used to drive the active transport of an ion into the cell AGAINST the ion's concentration gradient?
This is an example of energy coupling. Correct. The free energy released from the hydrolysis of ATP is coupled to the energy-requiring active transport of the ion across a membrane.
Consider the growth of a farmer's crop over a season. Which of the following correctly states a limitation imposed by the first or second law of thermodynamics?
To obey the first law, the crops must represent an open system. Correct. The first law states that energy cannot be created. The growth of plants stores much energy in the body of the plant. That energy must have been obtained from the plant's environment; thus, the plant must be an open system.
isomers
Two different molecules that have the same chemical formula
hydrolisis reaction
When a water molecule is added to a substance -(adding a H2O molecule, breaking a bond)
Can ectotherms have stable body temperatures? Explain.
Yes, ectotherms in the deep sea and in constant-temperature freshwater springs have constant body temperatures. And terrestrial ectotherms can maintain relatively constant body temperatures by behavioral means.
carbonyl group
a chemical group consisting of a carbon atom linked by a double bond to an oxygen atom
amino group
a chemical group consisting of a nitrogen atom bonded to two hydrogen atoms
When one or more pairs of valence electrons are shared by two neutral atoms, what type of bond is formed?
a covalent bond
From the equation Delta G = Delta H - T Delta S it is clear that
a decrease in the system's total energy will increase the probability of spontaneous change, increasing the entropy of a system will increase the probability of spontaneous change, and increasing the temperature of a system will increase the probability of spontaneous change Correct. This is the best response.
sickle cell anemia
a genetic disorder that causes abnormal hemoglobin, resulting in some red blood cells assuming an abnormal sickle shape
metabolic pathways
a series of enzymatic reactions that converts one biological material to another. -oxidative metabolism
aqueous solution
a solution in which water is the solvent
Which of the following has the most free energy per molecule?
a starch molecule Correct. Starch is a large polymer of sugar and thus contains many covalent bonds.
polar covalent
a type of bond that forms when electrons are not shared equally -H20 & O2
hydrophobic interaction
a type of weak chemical interaction caused when molecules that do not mix with water coalesce to exclude water -instead the other substance with form together
Consider the energy budgets for a human, an elephant, a penguin, a mouse, and a snake. The ________ would have the highest total annual energy expenditure, and the ________ would have the highest energy expenditure per unit mass. a. elephant; mouse b. elephant; human c. mouse; snake d. penguin; mouse
a. elephant; mouse
Lipid bilayers are created from: a.phospholipids b.triglycerides c.fatty acids d.glycerol e.proteins
a.phospholipids
The process of stabilizing the structure of an enzyme in its active form by the binding of a molecule outside the active site is an example of
allosteric activation Correct. The molecule in this example would be termed an allosteric activator.
Which chemical group is most likely to be responsible for an organic molecule behaving as a base?
amino
The most common form of calcium has 20 protons, 20 neutrons, and 20 electrons. Which of the following elements would be an isotope of calcium?
an atom with 20 protons, 21 neutrons, and 20 electrons
If you change the number of neutrons in an atom, you create _____.
an isotope
Autotroph
an organism that is able to form nutritional organic substances from simple inorganic substances such as carbon dioxide. -plants use starch to store energy (macromolecules also), they are photoautotrophs
In which of the following will isotopes of an element always differ?
atomic mass
Ionic bonds form as a result of __________.
attraction between ions that have opposite charges
hydrogen bonds
attractive forces in which a hydrogen covalently bonded to a very electronegative atom is also weakly bonded to an unshared electron pair of another electronegative atom - stabilize macromolecules (Ammonia), gives water its shape, non covalent
You are studying a large tropical reptile that has a high and relatively stable body temperature. How would you determine whether this animal is an endotherm or an ectotherm? a. You must know from its high & stable body temp. that it must be an endotherm b. You subject this reptile to various temps. in the lab & find that its body temp. & metabolic rate change w/ the ambient temperature. You conclude its an ectotherm. c. You subject this reptile to various temperatures in the lab and find that its body temperature and metabolic rate change with the ambient temperature. You conclude that it is an ectotherm. d. You know from its high and stable body temperature that it must be an endotherm.
b. You subject this reptile to various temps. in the lab & find that its body temp. & metabolic rate change w/ the ambient temperature. You conclude its an ectotherm.
The level of polypeptide folding in which the primary sequence coils around itself, stabilized by regularly spaced hydrogen bonds, is called: a.primary structure b.alpha helix c.beta sheet d.tertiary structure e.quaternary structure
b.alpha helix
The monomers used to synthesize proteins are called: a.nucleotides b.amino acids c.fatty acids d.sugars e.glycerol
b.amino acids
What kind of molecule is represented by the structure below? CH3CH2CH2CH2CH=CHCH2CH2CH2CH2CH2CH2CH2COOH a.a sugar b.an unsaturated fatty acid c.a saturated fatty acid d.a disaccharide e.a phospholipid
b.an unsaturated fatty acid
Why are radioactive isotopes useful in scientific research?
because they can be used as tracers to follow particular atoms and molecules through metabolic pathways
How do enzymes lower activation energy?
by locally concentrating the reactants Correct. One of the ways enzymes work is to increase the concentrations of reactants at a single place.
An animai's input of energy & materials would exceed its outputs a. if the animal is an endotherm, which must always take more energy bc of its high metabolic rate b. if it is actively foraging for food c. if it is growing and inc. in mass d. never; due to homeostasis, these energy & material budgets always balance
c. if it is growing and inc. in mass
Which of the following would increase the rate of heat exchange between an animal & its environment? a. feathers or fur b. vasoconstriction c. wind browning across the body surface d. countercurrent heat exchange
c. wind browning across the body surface
glycosidic bonds
carbons on adjacent sugar units are bonded to the same oxygen atom like links in a chain -alpha bonds help make structure flexible
alpha helices
clockwise coils around a central axis secondary structure form -held by H bonds b/n a peptide bond's amino group w another pep. bond's carboxyl group 4 amino acids away
Which of the following animals uses the largest percentage of its energy budget for homeostatic regulation? a. a snake in a temperate forest b. a desert bird c. a hydra d. a desert insect e. a marine jelly (an invertebrate)
d. a desert insect
how are disaccharides formed?
dehydration synthesis -alpha and beta glycosidic bonds
A nucleoside contains: a.a pentose sugar b.a purine or pyrimidine base c.one or more phosphate group d.all of these e.a and b, but not c
e.a and b, but not c
Which of the following items is a polymer of glucose? a.starch b.glycogen c.cellulose d.lactose e.a, b, and c, but not d
e.a, b, and c, but not d
Which of the following levels of protein structure is often stabilized by S-S bonds? a.primary structure b.secondary structure c.tertiary structure d.quaternary structure e.both c and d
e.both c and d
Which of the following functions is not associated with proteins? a.contraction b.providing structural material c.enzymes d.specific binding e.information storage
e.information storage
Sulfur is found in: a.DNA b.RNA c.sugars d.lipids e.proteins
e.proteins
Which of the following has negligible mass?
electron
what aspect of atoms are involved in energy?
electrons
in a spontaneous change =>
free energy v & system stability ^
Which of the following reactions would be endergonic?
glucose + fructose → sucrose Correct. In this case, the product is more complex, lower entropy, than the reactants, and like many anabolic reactions, this one requires an input of energy.
types of sugar molecules
glucose, ribose (for cell), fructose (fruit), sucrose (table sugar), lactose (milk)
Which of the following statements describes a reversible reaction that has reached chemical equilibrium?
he rate of the reverse reaction equals the rate of the forward reaction.
What mode of heat exchange is involved in "wind chill", when moving air feels colder than still air at the same temperature? Explain.
heat loss through retention
Enzyme activity is affected by pH because
high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site Correct. Each enzyme has an optimal pH at which it is most active, and variations in pH can alter the enzyme's structure, changing activity.
folded protein
hydrophobic core has non polar, hydrophilic has non polar & is on outside
When the proton number and electron number are unequal, the atom or molecule __________.
is an ion
Why is glucose important?
is the source of all energy for the cell's activities in the body
Flowers differ in how much sunlight they absorb. Why might this matter to a humingbird seeking nectar on a cool morning?
it might be hard to find flowers w alot of nutrients since it was dark during night so the flowers werent doing much photosynthesis
Which macromolecule is not a polymer?
lipids
steroids
lipids characterized by a carbon skeleton consisting of four fused rings
maintenance
metabolic rate, homeostasis, digestion, predator avoidance/defense, immune defense, foraging, tradeoffs, cost/benefit analysis
Which of the following molecules has the shape of a completed tetrahedron?
methane (CH4)
more broken down a molecule is —->
more energy there is w the electrons
Which of the following subatomic particles has appreciable mass and lacks a charge?
neutron
cofactors
nonprotein enzyme helpers
building blocks of cells
nucleic acids, proteins, carbohydrates, lipids
The chemical characteristics or reactivity of an element depend mostly on the __________.
number of electrons in its outermost shell
Some groups of elements react chemically in similar ways. For example, the chemistry of sodium and the chemistry of lithium are similar. The chemistry of chlorine and the chemistry of iodine are also similar. These similarities in chemistry result when different elements have similar __________.
numbers of outer-shell electrons
secondary protein structure
occurs when the sequence of amino acids are linked by hydrogen bonds -regular & irregular folds
A covalent bond is likely to be polar if __________.
one of the atoms sharing electrons is much more electronegative than the other
hydrocarbons
organic molecules consisting of only carbon and hydrogen
Heterotroph
organism that obtains energy from the foods it consumes; also called a consumer -use chemical energy harvested from food to fuel metabolism too -animals use fat & glycogen to store carbs.
In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by _____.
polar covalent bond
larger units of cell
polysaccharides fats, lipids, membranes proteins nucleic acids
protein
primary, secondary, tertiary, quaternary
The free energy derived from the hydrolysis of ATP can be used to perform many kinds of cellular work. Which of the following is an example of the cellular work involved in the production of electrochemical gradients?
proton movement against a gradient of protons Correct. Protein pumps that hydrolyze ATP can generate electrochemical gradients.
An exergonic (spontaneous) reaction is a chemical reaction that
releases energy when proceeding in the forward direction Correct. Exergonic reactions proceed with a net release of free energy, and they occur spontaneously.
In general, the hydrolysis of ATP drives cellular work by
releasing free energy that can be coupled to other reactions Correct. With the help of specific enzymes, the cell can couple the energy of ATP hydrolysis directly to endergonic processes.
A hydrogen bond __________.
s a weak chemical bond
primary protein structure
sequence of a chain of amino acids
An uncharged atom of nitrogen (atomic number = 7) has __________.
seven protons and seven electrons
collagen
structural protein found in the skin and connective tissue
Thermodynamics
study of the flow and transformation of energy in the universe
catalyst
substance that speeds up the rate of a chemical reaction
Molecules and Macromolecules
sugar —> polysaccharides nucleotides —> nucleic acids amino acids —> proteins fatty acids —> lipids
mole
the SI base unit used to measure the amount of a substance
energy
the ability to do work
catalysis
the acceleration of a chemical reaction by a catalyst
Which of the following is changed by the presence of an enzyme in a reaction?
the activation energy Correct. An enzyme lowers the amount of energy required to get the reactants to the transition state.
energy budget
the amount of energy available to heat the earth's land, water, and air -heat is the weakest one
energy intake
the amount of food a person eats; in other words, it is the number of kilocalories consumed -organisms should max. energy intake
functional groups
the components of organic molecules that are most commonly involved in chemical reactions
In the term trace element, the adjective trace means that
the element is required in very small amounts.
kinetic energy
the energy an object has due to its motion
The reactivity of an atom arises from
the existence of unpaired electrons in the valence shell.
Which of the following determines the sign of Delta G for a reaction?
the free energy of the reactants and the free energy of the products Correct. By subtracting the free energy of the reactants from the free energy of the products, the Delta G can be calculated and the difference in these values determines the sign of the difference.
The formation of glucose-6-phosphate from glucose is an endergonic reaction and is coupled to which of the following reactions or pathways?
the hydrolysis of ATP Correct. With the help of specific enzymes, the cell is able to couple the energy of ATP hydrolysis directly to endergonic processes by transferring a phosphate group from ATP to some other molecule, such as glucose.
Pharmaceutical researchers are often interested in blocking particular receptor proteins on cell surfaces. What chemical property of a molecule would be most important for this type of application?
the molecule's shape
Much of the suitability of ATP as an energy intermediary is related to the instability of the bonds between the phosphate groups. These bonds are unstable because
the negatively charged phosphate groups vigorously repel one another and the terminal phosphate group is more stable in water than it is in ATP Correct. Negative charges repel each other. Loss of the terminal phosphate removes some of the repulsion.
molarity
the number of moles of solute per liter of solution
what makes atoms reactive?
the outer shell has an incomplete set of electrons, they will get more atoms to complete it
A chemical reaction is designated as exergonic rather than endergonic when
the potential energy of the products is less than the potential energy of the reactants Correct. If a reaction is exergonic, the formation of new bonds releases more energy than was invested in breaking the old bonds.
enzymatic hydrolysis
the process in digestion that splits macromolecules from food by the enzymatic addition of water
energy surplus
the quantity of energy gained by a process or activity minus the energy used by that process or activity
phosphorylated intermediate
the recipient with the phosphate group covalently bonded to it
hydration shell
the sphere of water molecules around each dissolved ion
solvent
the substance in which the solute dissolves
solute
the substance that is dissolved
at body temp. below the normal range
the thermostat inhibits heat loss mechanisms saving heat (constriction in vessels) or generate heat (shivering).
A plot of reaction rate, velocity, against temperature for an enzyme indicates little activity at 10°C and 45°C, with peak activity at 35°C. The most reasonable explanation for the low velocity at 10°C is that
there is too little activation energy available Correct. The environment usually supplies activation energy in the form of heat. The lower the temperature, the less energy that is available to overcome the activation energy barrier.
response to elevated body temp.
thermostat shuts down heat retention mechanisms & promotes body colina by dilation of skin vessels, sweating, or panting
photosynthesis & respiration
they are complementary -photosynthesis —> organic molec. —> ATP —-> CO2 & H20 —-> photosynthesis
zwitterionic
this form of amino acid has a charge on both the amino and carboxyl group, but has a net charge of zero
molecule
two or more atoms held together by covalent bonds
Which of the following is a hydrophobic material? 1) paper 2) table salt 3) wax 4) sugar 5) pasta
wax
terminate growth
when hit level of maturity = stop growing
When do hydrogen bonds occur?
when partial opposite charges on molecules come close enough to attract each other
For most atoms, when is a stable configuration of electrons attained?
when the atom has eight electrons in its outermost shell
