Homework 2
ATP is an unstable, high-energy molecule that provides body cells with a form of energy that is immediately usable. 1)true 2)false
1 ATP is the primary energy-transferring molecule in cells, and it provides a form of energy that is immediately usable by all body cells. Chemically, the triphosphate tail of ATP can be compared to a tightly coiled spring ready to uncoil with tremendous energy when the catch is released. Actually, ATP is a very unstable high-energy molecule because its three negatively charged phosphate groups are closely packed and repel each other.
Water ________. 1)can form hydrogen bonds 2)has a low heat capacity 3)is a poor solvent since few things dissolve in it 4)is non-polar
1 Due to its polar nature, water is able to form hydrogen bonds. In fact, many of the special properties of water derive from its extensive hydrogen bonding capacity. In addition, water has a high heat capacity and is considered a universal solvent since it dissolves more substances than any other known solvent.
After the transfer of the electron, sodium will form an ion with ______. 1)a charge of +1 2)an atomic number of 18 3)a charge of -1 4)an atomic number of 10
1 If sodium loses an electron, it will be positively charged. Although not shown explicitly in the figure, the element sodium contains 11 protons within its nucleus. If sodium forms a cation containing 10 electrons, it will have a charge of +1.
Bonds between carbon and hydrogen atoms (as depicted on the right side of the figure) are generally __________. 1)nonpolar covalent bonds 2)polar covalent bonds 3) hydrogen bonds 4)ionic bonds
1 Neither carbon nor hydrogen is considered an electronegative atom. Therefore, neither atom has an overly strong pull on shared electrons, and those electrons are shared equally within a nonpolar covalent bond
Which organic molecules form the major structural materials of the body? 1)proteins 2)calcium salts in bones 3)carbohydrates 4)lipids
1 Proteins form the major structural materials of the body. Because fibrous proteins are the chief building materials of the body, they are also known as structural proteins.
The major function of RNA is to carry out the genetic instructions for protein synthesis. 1)true 2)false
1 The major function of RNA is to carry out the genetic instructions (provided by DNA) for protein synthesis.
All amino acids (such as the four represented in the figure) contain ______. 1)an amine group and a carboxyl group 2)an amine group and a fatty acid 3)a nitrogen-containing base and a pentose sugar 4)phosphorous and nitrogen
1 The oval area shown in each of the amino acids highlights the amino group, carboxyl group, and central carbon found in all amino acids.
What is the primary energy-transferring molecule in cells? 1)ATP 2)TACT 3)RNA 4)DNA
1 When broken (cleaved), the high-energy phosphate bonds in the ATP molecule release the energy used to do cellular work.
The structure indicated by A is a ______. 1)enzyme 2)substrate 3)active site 4)catalyst
2 A substrate is a reactant in an enzyme-catalyzed reaction.
If the molecules indicated by (A) are amino acids, then the line in the figure indicated by (D) is a(n) ______ 1)active site 2)peptide bond 3)R group 4)hydrogen bond
2 Amino acids are linked by peptide bonds to form polypeptides.
Which of the following statements is true regarding reactions A and B? 1)Reaction A is exergonic and reaction B is endergonic 2)Both reaction A and reaction B are exergonic reactions 3)Reaction A is endergonic and reaction B is exergonic 4)Both reaction A and reaction B are endergonic reactions.
2 Both of the illustrated reactions are exergonic and release the same amount of energy during product formation. The difference is the amount of energy input (activation energy) required to initiate the reactions depending on the presence or absence of enzyme.
Except for elements 1 and 2, all other elements are stable with how many electrons in their outermost (valence) energy level? 1)2 2)8 3)18 4)32
2 Elements 1 and 2 are stable with a maximum of two electrons in their outermost (valence) energy level (electron shell). All other elements are stable with eight electrons in their valence shell.
Which of the following statements is true regarding the enzyme-catalyzed reaction compared to the uncatalyzed reaction? 1)The reaction in the presence of enzyme releases more energy. 2)Less energy input is required to start the reaction in the presence of enzyme. 3)The reaction in the presence of enzyme will form a larger proportion of product 4)All of the listed responses are true
2 Enzyme-catalyzed reactions require less activation energy and therefore are initiated with a lower input of energy. This activation energy represents the energy necessary for driving the early stages of the reaction: creating contact between properly oriented substrates, breaking original bonds, and so on
What is the difference between kinetic and potential energy? 1)Kinetic energy and potential energy are synonymous; they are defined as the capacity to do work, actively putting matter into motion 2)Kinetic energy is energy in action, while potential energy is stored energy. 3)Kinetic energy may eventually become potential energy, but potential energy cannot become kinetic energy 4)Kinetic energy is stored energy and has the capacity to do work; potential energy is expressed through motion
2 Kinetic energy is energy in action. We see evidence of kinetic energy in the constant movement of the tiniest particles of matter, as well as in larger objects. Potential energy is stored energy, which has the capacity to do work, but is not presently doing so
Which of the following is NOT a difference between a compound and a mixture? 1)Mixtures can be separated by physical means, such as straining, filtering, or evaporation. Compounds can only be separated into their constituent atoms by chemically breaking bonds. 2)Mixtures are homogeneous while compounds are heterogeneous. 3)Some mixtures are homogenous, while others are heterogeneous. All compounds are homogeneous. 4)No chemical bonding occurs between the components of a mixture. The properties of atoms and molecules are not changed when they become part of a mixture
2 Mixtures differ from compounds in several important ways. (1) The chief difference between mixtures and compounds is that no chemical bonding occurs between the components of a mixture. The properties of atoms and molecules are not changed when they become part of a mixture. (2) Depending on the mixture, its components can be separated by physical means--straining, filtering, evaporation, and so on. Compounds, by contrast, can be separated into their constituent atoms only by chemical means (breaking bonds). (3) Some mixtures are homogenous, while others are heterogeneous. All compounds are homogeneous.
Which of the following is formed once the ions in the salt crystal have completely dissociated from one another? 1)a suspension 2) a solution 3) a buffer 4)a colloid
2 Once dissociated, the sodium and chloride ions would be expected to disperse uniformly amongst the surrounding water molecules. This homogenous mixture is called a solution.
Which of the following molecular features is found in molecule A, but NOT in molecule B? 1)two amino acids 2)a polar group 3)a glycerol molecule 4)three fatty acid chains
2 Only the phospholipid contains a phosphorous-containing polar "head" group
Which organic molecules form the major structural materials of the body? 1)nucleic acids 2)proteins 3)carbohydrates 4)lipids
2 Proteins form the major structural materials of the body. Because fibrous proteins are the chief building materials of the body, they are also known as "structural" proteins.
Sodium has one valence electron, while chlorine has seven. What type of chemical bond is most likely to occur between sodium and chlorine? 1)polar covalent 2)ionic 3)covalent 4)hydrogen
2 Sodium and chlorine are joined by an ionic bond. Sodium gives up its valence shell electron (becoming a cation) to drop back to a stable energy level, and chlorine gains one electron (becoming an anion) to fill its valence shell and become stable.
One carbon atom can combine with two oxygen atoms to form carbon dioxide. Use the diagram to predict the type of bond that would be necessary to join the oxygens to the carbon to form a stable molecule. 1)single bonds 2)two double bonds 3)triple bonds
2 The formation of a double bond (the sharing of two electron pairs) between each oxygen and the carbon would result in each of the three atoms achieving a full valence shell.
What is the mass number of the helium atom? 1)2 amu 2)4 amu 3)6 amu 4)It cannot be determined from this image.
2 The helium atom shown contains two protons and two neutrons, which contribute to a total mass number of 4 amu
Which of the following is a primary function of molecule B? 1)formation of cell membranes 2)energy storage 3)storage of genetic information 4) act as biological catalyst
2 The hydrocarbon groups that dominate the structure of triglycerides are the basis for the efficient and compact energy storage by fat
Which of the following is a primary function of molecule B? 1)act as biological catalyst 2)energy storage 3)formation of cell membranes 4)storage of genetic information
2 The hydrocarbon groups that dominate the structure of triglycerides are the basis for the efficient and compact energy storage by fat.
Atomic weight is equal to the number of protons and neutrons in the nucleus. 1)True 2)False
2 The number of protons and neutrons in the nucleus is the mass number, or atomic mass
The three atoms shown represent three unique __________. 1)isotopes 2)elements 3)cells 4)molecules
2 The three atoms each contain different numbers of protons and are therefore unique elements.
What do these four elements have in common? 1)They all have the same number of protons in their nuclei. 2) They all have an incomplete valence electron shell. 3)They would all be likely to form positive ions. 4)They are all generally unreactive elements.
2 The valence shell is the outermost electron energy level. Valence shell electrons determine the reactivity of an element
Which of the following statements is true concerning the differences between compounds and mixtures? 1)Mixtures are all heterogeneous. 2)Compounds are all homogeneous. 3)Mixtures consist of chemical bonds between the components 4)Compounds can be separated by physical means.
2 because of the bonding evident in compounds. All compounds bond identically and are homogenous.
Which of the following statements is true regarding the enzyme-catalyzed reaction (B) compared to the uncatalyzed reaction (A)? 1)The reaction in the presence of enzyme will form larger products. 2)The products of the reaction with enzyme contain more chemical potential energy. 3)Less energy input is required to start the reaction in the presence of enzyme. 4)The reaction in the presence of enzyme releases more energy. 5)All of the listed responses are true.
3 Enzyme-catalyzed reactions require less activation energy and therefore are initiated with a lower input of energy. This activation energy represents the energy necessary for driving the early stages of the reaction: creating contact between properly oriented substrates, breaking original bonds, and so on.
Which of the following is true of protein structure? 1)Peptide bonds join the amine group on one amino acid with the R group of another amino acid. 2)Tertiary protein structure emerges when there is more than one peptide chain in a protein. 3)Secondary protein structures are caused by hydrogen bonding between adjacent amine and carboxyl groups. 4)Peptide bonds are formed by hydrolysis.
3 Hydrogen bonding between amine and carboxyl groups creates alpha helices and beta-pleated sheets.
Would water still be a polar molecule if it were NOT in the form of a V but rather were linear like carbon dioxide? 1)Yes, because the electronegativity difference between hydrogen and oxygen would still be present. 2)No, because there would no longer be a difference in electronegativity between the oxygen and hydrogen atoms. 3)No, because the difference in the pull of oxygen on the bonding electrons would be neutralized 4)Yes, because the oxygen would not bond equally to the two hydrogen atoms
3 Like in carbon dioxide, the difference in electronegativity of the oxygen and hydrogen atoms would be neutralized by being in a straight line
Which of the following is NOT a difference between a compound and a mixture? 1)No chemical bonding occurs between the components of a mixture. The properties of atoms and molecules are not changed when they become part of a mixture 2)Some mixtures are homogenous, while others are heterogeneous. All compounds are homogeneous 3)Mixtures are homogeneous while compounds are heterogeneous. 4)Mixtures can be separated by physical means, for example, straining, filtering, or evaporation. Compounds can only be separated into their constituent atoms by chemically breaking bonds.
3 Mixtures differ from compounds in several important ways. (1) The chief difference between mixtures and compounds is that no chemical bonding occurs between the components of a mixture. The properties of atoms and molecules are not changed when they become part of a mixture. (2) Depending on the mixture, its components can be separated by physical means, straining, filtering, evaporation, and so on. Compounds, by contrast, can be separated into their constituent atoms only by chemical means (breaking bonds). (3) Some mixtures are homogenous, while others are heterogeneous. All compounds are homogeneous.
Based on the information in this figure, what is the atomic number of chlorine? 1)7 2)10 3)17 4)18
3 Prior to this reaction, the chlorine atom had 17 electrons. Therefore, chlorine must have 17 protons and an atomic number of 17.
Each specific amino acid has a unique ______. 1)phosphate group 2)carboxyl group 3)R group 4)amino group
3 The identity of each unique amino acid is determined by the structure of its R group (note differences within the green rectangular area in amino acids (b) through (e)).
The chloride ion (Cl-) indicated by the arrow is interacting most closely with which of the following? 1)another chloride ion 2)a sodium ion 3)a hydrogen atom within a water molecule 4) an oxygen atom within a water molecule
3 The negatively charged chloride anion has dissociated from the salt crystal and formed an interaction with the positively charged hydrogen atoms of several water molecules
The pH scale __________. 1)is based on the salinity of a solution 2)ranges from 1 to 7 3)is based on the concentration of hydrogen ions in a solution 4)is linear
3 The pH scale, which ranges from 0 to 14, is a logarithmic scale based on the concentration of hydrogen ions in a solution.
The chemical reaction shown at step C is an ______. 1)exergonic dehydration synthesis 2)endergonic hydrolysis 3)endergonic dehydration synthesis 4)exergonic hydrolysis
3 This figure shows a dehydration synthesis reaction between two monomers forming, resulting in a larger molecule. Building larger molecules (an anabolic reaction) typically requires energy input (as indicated by the red arrow in the figure). Energy-requiring (as opposed to energy-releasing) reactions are termed endergonic.
Blood loss due to a moderate hemorrhage has several adverse effects on patient wellbeing. Why would administering IV fluids alone not be sufficient to return a patient to health? 1)Potential risk for over-hydration due to excess fluid infusion is too great to give IV fluids alone. 2)IV saline administration does not greatly alter blood sodium chemistry regardless of the amount of blood loss. 3)Giving hypertonic IV fluids such as lactated ringers may cause more harm than good 4)Oxygen-carrying red blood cells lost along with the fluid component must also be replaced.
4
What is the classification of a solution with a pH of 8.3? 1)buffered solution 2)neutral solution 3)acidic solution 4)alkaline solution
4 A pH between 0.0 and 7.0 is acidic. A pH between 7.0 and 14.0 is basic. Therefore, a solution with a pH of 8.3 is an alkaline (or basic) solution
If the molecules indicated by (A) are amino acids, then the line in the figure indicated by (D) is __________. 1)a hydrogen bond 2)an active site 3)an R group 4)a peptide bond
4 Amino acids are linked by peptide bonds to form peptides.
Which of the following is NOT one of the three basic steps involved in enzyme activity? 1)The enzyme's active site binds to the substrate(s) on which it acts, temporarily forming an enzyme-substrate complex. 2)The enzyme-substrate complex undergoes internal rearrangements that form the product(s). 3)The enzyme releases the product(s) of the reaction 4)The substrate absorbs chemical energy from the enzyme after binding to its active site
4 Enzymes do not provide energy to their substrates. In fact, enzymes are completely unchanged by their catalytic role and can act again and again
Which particle is indicated by the arrow? 1)atom 2)neutron 3)electron 4)proton
4 Note how the number of the indicated particles in each of the three atoms defines each as a unique element
Which of the following is a FALSE statement about carbohydrates? 1)Glycogen is a complex carbohydrate formed by dehydration synthesis of glucose molecules 2)Carbohydrates consist of monomers called simple sugars. 3)Dietary glucose is primarily used to drive our metabolic pathways that produce energy. 4)The chemical composition of carbohydrates includes two oxygens and one hydrogen for every carbon present.
4 The correct ratio is two hydrogens and one oxygen for every carbon.
The presence of what group differentiates most amino acids from each other? 1)a phosphate group 2)an amino group 3)an acid group 4)an R group
4 The identity of each unique amino acid is determined by the structure of its R group--note differences within the green rectangular area in amino acids (b) through (e).
What is represented by the chemicals at A? 1)enzymes 2)catalysts 3)active sites 4)substrates
4 The substrate is a reactant in an enzyme-catalyzed reaction.
Both molecule A and molecule B are classified as __________. 1)carbohydrates 2)proteins 3)nucleic acids 4)lipids
4 Triglycerides and phospholipids are two of the three major types of lipids.
In a solution, the solute is the substance present in the greatest amount.... 1)true 2)false
False In a solution, the solute is the substance present in lesser amounts. There may be many solutes.
Nonpolar molecules are the result of unequal electron pair sharing..true/false
False Polar molecules are the result of unequal electron pair sharing. Nonpolar molecules are electrically balanced because of the equal sharing of electrons between the atoms of the molecules
Why can dehydration be such a life-threating event?
It significantly alters the ratio of body water (solvent) to dissolved substances (solutes), such as sodium ions.
Buffers help to stabilize blood pH. True. False.
True Buffers are essential for stabilizing the pH of body fluids (such as blood). Note: buffers cannot prevent a change in pH, they can only resist or minimize the change (if acids or bases are added to the buffered solution).
The major function of DNA is to store the genetic instructions that are used during protein synthesis....true/false
True DNA serves as the blueprint to make the proteins your body needs