Test Review – Exam 2 Chapter 2

Test Review – Exam 2 Chapter 2

Terms to Know Mixture Suspensions Solutions Colloids Chemical energy
Molecule Atom Element Neutron Cation Nonpolar covalent bond Hydrogen bond Ionic bond Polar covalent bond Compound Mixture Suspensions Solutions Colloids Chemical energy Radiant energy Electrical energy Mechanical energy

Anything that has mass and occupies space
Matter Anything that has mass and occupies space States of matter: Solid—definite shape and volume Liquid—definite volume, changeable shape Gas—changeable shape and volume

Mass and Weight the mass of an object is a fundamental property of the object a numerical measure of its inertia measure of the amount of matter in the object. definitions of mass often seem circular because it is such a fundamental quantity that it is hard to define in terms of something else the usual symbol for mass is m and its SI unit is the kilogram the weight of an object is the force of gravity on the object (w = mg)

Weight Matter Mass Energy Can be measured only by its effects on matter. Anything that occupies space and has mass. Although a man who weighs 175 pounds on Earth would be lighter on the moon and heavier on Jupiter, his ________ would not be different. Is a function of and varies with gravity.

Energy Concepts What is energy?
The capacity to perform work What is the difference between potential and kinetic energy? Stored vs. motion Energy is neither created nor destroyed but… Converted from one form to another This property is called the conservation of energy What is the usual way in which energy is “lost?” Through heat What type of energy is heat? Kinetic due to random motion of atoms Heat is generated by friction (in this example between atoms and air) Heat is highly __________ energy and highest amount of _________. Disordered, entropy Chemical energy is a form of ____________ energy. Potential What is the primary form of chemical energy in living organisms? ATP What is cellular respiration? What are the byproducts? Conversion of glucose into ATP through reduction of oxygen forming water and carbon dioxide

Forms of Energy Chemical energy — stored in bonds of chemical substances Electrical energy — results from movement of charged particles Mechanical energy — directly involved in moving matter Radiant or electromagnetic energy — exhibits wavelike properties (i.e., visible light, ultraviolet light, and X-rays)

Composition of Matter Elements
Cannot be broken down by ordinary chemical means Each has unique properties: Physical properties Are detectable with our senses or are measurable Chemical properties How atoms interact (bond) with one another

Atomic symbol: one- or two-letter chemical shorthand for each element
Composition of Matter Atoms Unique building blocks for each element Atomic symbol: one- or two-letter chemical shorthand for each element

Atomic Structure Neutrons Protons No charge
Mass = 1 atomic mass unit (amu) Protons Positive charge Mass = 1 amu

Atomic Structure Determined by numbers of subatomic particles Nucleus consists of neutrons and protons

Atomic Structure Electrons Orbit nucleus
Equal in number to protons in atom Negative charge 1/2000 the mass of a proton (0 amu)

Identifying Elements Atoms of different elements contain different numbers of subatomic particles Compare hydrogen, helium and lithium (next slide)

Hydrogen (H) (1p+; 0n0; 1e–) Helium (He) (2p+; 2n0; 2e–) Lithium (Li)
Proton Neutron Electron Hydrogen (H) (1p+; 0n0; 1e–) Helium (He) (2p+; 2n0; 2e–) Lithium (Li) (3p+; 4n0; 3e–) Figure 2.2

Identifying Elements Atomic number = number of protons in nucleus

Mass number = mass of the protons and neutrons
Identifying Elements Mass number = mass of the protons and neutrons Mass numbers of atoms of an element are not all identical Isotopes are structural variations of elements that differ in the number of neutrons they contain

Valuable tools for biological research and medicine
Radioisotopes Valuable tools for biological research and medicine Cause damage to living tissue: Useful against localized cancers Radon from uranium decay causes lung cancer

Hydrogen (1H) (1p+; 0n0; 1e–) Deuterium (2H) (1p+; 1n0; 1e–)
Proton Neutron Electron Hydrogen (1H) (1p+; 0n0; 1e–) Deuterium (2H) (1p+; 1n0; 1e–) Tritium (3H) (1p+; 2n0; 1e–) Figure 2.3

Chemically Inert Elements
Stable and unreactive Outermost energy level fully occupied or contains eight electrons

(a) Chemically inert elements
Outermost energy level (valence shell) complete 8e 2e 2e Helium (He) (2p+; 2n0; 2e–) Neon (Ne) (10p+; 10n0; 10e–) Figure 2.5a

Chemically Reactive Elements
Outermost energy level not fully occupied by electrons Tend to gain, lose, or share electrons (form bonds) with other atoms to achieve stability

(b) Chemically reactive elements
Outermost energy level (valence shell) incomplete 4e 1e 2e Hydrogen (H) (1p+; 0n0; 1e–) Carbon (C) (6p+; 6n0; 6e–) 1e 6e 8e 2e 2e Oxygen (O) (8p+; 8n0; 8e–) Sodium (Na) (11p+; 12n0; 11e–) Figure 2.5b

Molecules and Compounds
Most atoms combine chemically with other atoms to form molecules and compounds Molecule — two or more atoms bonded together (e.g., H2 or C6H12O6) Compound — two or more different kinds of elements bonded together (e.g., C6H12O6)

Mixtures vs. Compounds Mixtures Compounds
No chemical bonding between components Can be separated physically, such as by straining or filtering Heterogeneous or homogeneous Compounds Can be separated only by breaking bonds All are homogeneous

Most matter exists as mixtures
Two or more components physically intermixed Three types of mixtures Solutions Colloids Suspensions

Usually transparent, e.g., atmospheric air or seawater
Solutions Homogeneous mixtures Usually transparent, e.g., atmospheric air or seawater Solvent Present in greatest amount, usually a liquid Solute(s) Present in smaller amounts

Colloids and Suspensions
Colloids (emulsions) Heterogeneous translucent mixtures, e.g., cytosol Large solute particles that do not settle out Undergo sol-gel transformations Suspensions: Heterogeneous mixtures (blood) Large visible solutes tend to settle out

Solution Colloid Suspension Solute particles are very
tiny, do not settle out or scatter light. Solute particles are larger than in a solution and scatter light; do not settle out. Solute particles are very large, settle out, and may scatter light. Solute particles Solute particles Solute particles Example Mineral water Example Gelatin Example Blood Figure 2.4

Mixtures vs. Compounds Mixtures Compounds
No chemical bonding between components Can be separated physically, such as by straining or filtering Heterogeneous or homogeneous Compounds Can be separated only by breaking bonds All are homogeneous

Heterogeneous, will not settle.
Heterogeneous, will settle. Homogeneous, will not settle. Will not scatter light. A)Suspensions B) Solutions C) Colloids

Nonpolar covalent bond
Hydrogen bond Ionic bond Polar covalent bond

Chemical Bonds Electrons occupy up to seven electron shells (energy levels) around nucleus Octet rule: Except for the first shell which is full with two electrons, atoms interact in a manner to have eight electrons in their outermost energy level (valence shell)

Figure 2.9

Ions are formed by transfer of valence shell electrons between atoms
Ionic Bonds Ions are formed by transfer of valence shell electrons between atoms Anions (– charge) have gained one or more electrons Cations (+ charge) have lost one or more electrons Attraction of opposite charges results in an ionic bond

Formation of an Ionic Bond
Ionic compounds form crystals instead of individual molecules NaCl (sodium chloride)

+ – Figure 2.6a-b Sodium atom (Na) (11p+; 12n0; 11e–)
Chlorine atom (Cl) (17p+; 18n0; 17e–) Sodium ion (Na+) Chloride ion (Cl–) Sodium chloride (NaCl) (a) Sodium gains stability by losing one electron, and chlorine becomes stable by gaining one electron. (b) After electron transfer, the oppositely charged ions formed attract each other. Figure 2.6a-b

(c) Large numbers of Na+ and Cl– ions
CI– Na+ (c) Large numbers of Na+ and Cl– ions associate to form salt (NaCl) crystals. Figure 2.6c

Covalent Bonds Formed by sharing of two or more valence shell electrons Allows each atom to fill its valence shell at least part of the time

+ Reacting atoms Resulting molecules or Structural formula shows
single bonds. Hydrogen atoms Carbon atom Molecule of methane gas (CH4) (a) Formation of four single covalent bonds: carbon shares four electron pairs with four hydrogen atoms. Figure 2.7a

Sharing of electrons may be equal or unequal
Covalent Bonds Sharing of electrons may be equal or unequal Equal sharing produces electrically balanced nonpolar molecules CO2

+ Reacting atoms Resulting molecules or Structural formula shows
double bond. Oxygen atom Oxygen atom Molecule of oxygen gas (O2) (b) Formation of a double covalent bond: Two oxygen atoms share two electron pairs. Figure 2.7b

Figure 2.8a

Covalent Bonds Unequal sharing by atoms with different electron-attracting abilities produces polar molecules H2O Atoms with six or seven valence shell electrons are electronegative, e.g., oxygen Atoms with one or two valence shell electrons are electropositive, e.g., sodium

Figure 2.8b

Hydrogen bonds The bonds of a water molecule represent ________ _______ type of bond. Also known as a ________. Polar covalent, dipole Oxygen has a greater affinity for the electrons and is therefore more _____________. Whereas, hydrogen has a lesser attraction for electrons is more _____________. Electronegative, electropositive The oxygen end of the molecule is therefore slightly more _________ and the hydrogen ends are slightly more _________. Negative, positive The attraction between the negative oxygen end of one water compound to the positive hydrogen end of another water represents a ___________ bond. Hydrogen Hydrogen bonds are strong bonds. (T/F) False They are easily broken Hydrogen bonds may inter- or intramolecular. (T/F) True The unique properties of water are attributable to hydrogen bonds. Some of the properties include…. Cohesion, high boiling point, why ice floats, high heat of vaporization, high heat capacity

Hydrogen bond (indicated by dotted line)
+ – Hydrogen bond (indicated by dotted line) + + – – – + + + – (a) The slightly positive ends (+) of the water molecules become aligned with the slightly negative ends (–) of other water molecules. Figure 2.10a

Occur when chemical bonds are formed, rearranged, or broken
Chemical Reactions Occur when chemical bonds are formed, rearranged, or broken Represented as chemical equations Chemical equations contain: Molecular formula for each reactant and product Relative amounts of reactants and products, which should balance

Patterns of Chemical Reactions
Synthesis (combination) reactions Decomposition reactions Exchange reactions

Synthesis Reactions A + B  AB Always involve bond formation Anabolic

Dehydration Synthesis and Hydrolysis
What is dehydration synthesis? Removal of a water molecule to form a new covalent bond What is hydrolysis? The addition of a water molecule to break a covalent bond What is anabolism? Forming new bonds to build something bigger. Requires energy (endergonic) What is catabolism? Breaking bonds to make something smaller. Large molecules down to subunits. Releases energy (exergonic).

Decomposition Reactions
AB  A + B Reverse synthesis reactions Involve breaking of bonds Catabolic

Oxidation-Reduction (Redox) Reactions
Decomposition reactions: Reactions in which fuel is broken down for energy Also called exchange reactions because electrons are exchanged or shared differently Electron donors lose electrons and are oxidized Electron acceptors receive electrons and become reduced

All chemical reactions are either exergonic or endergonic
Exergonic reactions — release energy Catabolic reactions Endergonic reactions — products contain more potential energy than did reactants Anabolic reactions

Chemical Reactions All chemical reactions are theoretically reversible
A + B  AB AB  A + B Chemical equilibrium occurs if neither a forward nor reverse reaction is dominant Many biological reactions are essentially irreversible due to Energy requirements Removal of products

Rate of Chemical Reactions
Rate of reaction is influenced by:  temperature   rate  particle size   rate  concentration of reactant   rate Catalysts:  rate without being chemically changed Enzymes are biological catalysts

Classes of Compounds Inorganic compounds Organic compounds
Water, salts, and many acids and bases Do not contain carbon Organic compounds Carbohydrates, fats, proteins, and nucleic acids Contain carbon, usually large, and are covalently bonded

Water 60%–80% of the volume of living cells Most important inorganic compound in living organisms because of its properties

High heat of vaporization
Properties of Water High heat capacity Absorbs and releases heat with little temperature change Prevents sudden changes in temperature High heat of vaporization Evaporation requires large amounts of heat Useful cooling mechanism

Polar solvent properties
Properties of Water Polar solvent properties Dissolves and dissociates ionic substances Forms hydration layers around large charged molecules, e.g., proteins (colloid formation) Body’s major transport medium

Water molecule Salt crystal Ions in solution
+ – + Water molecule Salt crystal Ions in solution Figure 2.12

Properties of Water Reactivity Cushioning
A necessary part of hydrolysis and dehydration synthesis reactions Cushioning Protects certain organs from physical trauma, e.g., cerebrospinal fluid

Salts Ionic compounds that dissociate in water Contain cations other than H+ and anions other than OH– Ions (electrolytes) conduct electrical currents in solution Ions play specialized roles in body functions (e.g., sodium, potassium, calcium, and iron)

Acids and Bases Both are electrolytes
Acids are proton (hydrogen ion) donors (release H+ in solution) HCl  H+ + Cl–

Bases are proton acceptors (take up H+ from solution)
Acids and Bases Bases are proton acceptors (take up H+ from solution) NaOH  Na+ + OH– OH– accepts an available proton (H+) OH– + H+  H2O Bicarbonate ion (HCO3–) and ammonia (NH3) are important bases in the body because of buffering properties

Acid-Base Concentration
Acid solutions contain [H+] As [H+] increases, acidity increases, pH decreases Alkaline solutions contain bases (e.g., OH–) As [H+] decreases (or as [OH–] increases), alkalinity increases, pH increases

pH: Acid-Base Concentration
pH = the negative logarithm of [H+] in moles per liter Neutral solutions: Pure water is pH neutral (contains equal numbers of H+ and OH–) pH of pure water = pH 7: [H+] = 10 –7 M All neutral solutions are pH 7

pH: Acid-Base Concentration
Acidic solutions  [H+],  pH Acidic pH: 0–6.99 pH scale is logarithmic: a pH 5 solution has 10 times more H+ than a pH 6 solution Alkaline solutions  [H+],  pH Alkaline (basic) pH: 7.01–14

Figure 2.13 Neutral Concentration (moles/liter) Examples [OH–] [H+] pH
1M Sodium hydroxide (pH=14) 100 10–14 14 Oven cleaner, lye (pH=13.5) 10–1 10–13 13 10–2 10–12 12 Household ammonia (pH=10.5–11.5) 10–3 10–11 11 10–4 10–10 10 Household bleach (pH=9.5) 10–5 10–9 9 Egg white (pH=8) 10–6 10–8 8 Blood (pH=7.4) 10–7 10–7 7 Neutral Milk (pH=6.3–6.6) 10–8 10–6 6 10–9 10–5 5 Black coffee (pH=5) 10–10 10–4 4 Wine (pH=2.5–3.5) 10–11 10–3 3 Lemon juice; gastric juice (pH=2) 10–12 10–2 2 10–13 10–1 1 1M Hydrochloric acid (pH=0) 10–14 100 Figure 2.13

Acid-Base Homeostasis
pH change interferes with cell function and may damage living tissue Slight change in pH can be fatal pH is regulated by kidneys, lungs, and buffers

Mixture of compounds that resist pH changes
Buffers Mixture of compounds that resist pH changes Convert strong (completely dissociated) acids or bases into weak (slightly dissociated) ones Carbonic acid-bicarbonate system

Organic Compounds Contain carbon (except CO2 and CO, which are inorganic) Unique to living systems Include carbohydrates, lipids, proteins, and nucleic acids

Organic Compounds Many are polymers — chains of similar units (monomers or building blocks) Synthesized by dehydration synthesis Broken down by hydrolysis reactions How are polymers formed? By dehydration synthesis What reactions break down polymers into monomers? By hydrolysis What molecule is essential to this process? H2O

Monomers linked by covalent bond Monomers linked by covalent bond
(a) Dehydration synthesis Monomers are joined by removal of OH from one monomer and removal of H from the other at the site of bond formation. + Monomer 1 Monomer 2 Monomers linked by covalent bond (b) Hydrolysis Monomers are released by the addition of a water molecule, adding OH to one monomer and H to the other. + Monomer 1 Monomer 2 Monomers linked by covalent bond (c) Example reactions Dehydration synthesis of sucrose and its breakdown by hydrolysis Water is released + Water is consumed Glucose Fructose Sucrose Figure 2.14

Contain C, H, and O [(CH20)n] Three classes
Carbohydrates Sugars and starches Contain C, H, and O [(CH20)n] Three classes Monosaccharides Disaccharides Polysaccharides

Carbohydrates Functions Major source of cellular fuel (e.g., glucose)
Structural molecules (e.g., ribose sugar in RNA)

Monosaccharides Simple sugars containing three to seven C atoms (CH20)n n = 3 – 7 C3H6O3 C6H12O6

Hexose sugars (the hexoses shown
(a) Monosaccharides Monomers of carbohydrates Example Hexose sugars (the hexoses shown here are isomers) Example Pentose sugars Glucose Fructose Galactose Deoxyribose Ribose Figure 2.15a

Long branching chains (polymers) of linked monosaccharides Example
Glycogen is animals main storage form of glucose. Found in high concentrations in the liver and muscles. Starch is plants main storage form of glucose. Cellulose is a key structural molecule in plants. Not digestible by humans. (c) Polysaccharides Long branching chains (polymers) of linked monosaccharides Example This polysaccharide is a simplified representation of glycogen, a polysaccharide formed from glucose units. Glycogen Figure 2.15c

Contain C, H, O (less than in carbohydrates), and sometimes P
Lipids Contain C, H, O (less than in carbohydrates), and sometimes P Insoluble in water Main types: Neutral fats or triglycerides Phospholipids Steroids Eicosanoids

Neutral fats — solid fats and liquid oils
Triglycerides Neutral fats — solid fats and liquid oils Composed of three fatty acids bonded to a glycerol molecule Main functions Energy storage Insulation Protection

(a) Triglyceride formation
Three fatty acid chains are bound to glycerol by dehydration synthesis + Glycerol 3 fatty acid chains Triglyceride, or neutral fat 3 water molecules Figure 2.16a

Saturation of Fatty Acids
Saturated fatty acids Single bonds between C atoms; maximum number of H Solid animal fats, e.g., butter Unsaturated fatty acids One or more double bonds between C atoms Reduced number of H atoms Plant oils, e.g., olive oil

Modified triglycerides:
Phospholipids Modified triglycerides: Glycerol + two fatty acids and a phosphorus (P)-containing group “Head” and “tail” regions have different properties (amphipathic) Hydrophilic head Hydrophobic tail Important in cell membrane structure

(b) “Typical” structure of a phospholipid molecule
Two fatty acid chains and a phosphorus-containing group are attached to the glycerol backbone. Example Phosphatidylcholine Polar “head” Nonpolar “tail” (schematic phospholipid) Phosphorus- containing group (polar “head”) Glycerol backbone 2 fatty acid chains (nonpolar “tail”) Figure 2.16b

Steroids Steroids — interlocking four-ring structure Cholesterol, vitamin D, steroid hormones, and bile salts

Simplified structure of a steroid
Four interlocking hydrocarbon rings form a steroid. Example Cholesterol (cholesterol is the basis for all steroids formed in the body) Figure 2.16c

Other Lipids in the Body
Other fat-soluble vitamins Vitamins A, D, E, and K Lipoproteins Transport fats in the blood

Polymers of amino acids (20 types)
Proteins Polymers of amino acids (20 types) Joined by peptide bonds Contain C, H, O, N, and sometimes S and P

this amino acid is likely intramolecular bonding.
Amine group Acid group (a) Generalized structure of all amino acids. (b) Glycine is the simplest amino acid. (c) Aspartic acid (an acidic amino acid) has an acid group (—COOH) in the R group. (d) Lysine (a basic amino acid) has an amine group (–NH2) in the R group. (e) Cysteine (a basic amino acid) has a sulfhydryl (–SH) group in the R group, which suggests that this amino acid is likely to participate in intramolecular bonding. Figure 2.17

next, with loss of a water
Dehydration synthesis: The acid group of one amino acid is bonded to the amine group of the next, with loss of a water molecule. Peptide bond + Amino acid Amino acid Dipeptide Hydrolysis: Peptide bonds linking amino acids together are broken when water is added to the bond. Figure 2.18

The sequence of amino acids forms the polypeptide chain.
(a) Primary structure: The sequence of amino acids forms the polypeptide chain. Figure 2.19a

a-Helix: The primary chain is coiled
to form a spiral structure, which is stabilized by hydrogen bonds. b-Sheet: The primary chain “zig-zags” back and forth forming a “pleated” sheet. Adjacent strands are held together by hydrogen bonds. (b) Secondary structure: The primary chain forms spirals (a-helices) and sheets (b-sheets). Figure 2.19b

Tertiary structure of prealbumin (transthyretin), a protein that
transports the thyroid hormone thyroxine in serum and cerebrospinal fluid. (c) Tertiary structure: Superimposed on secondary structure. a-Helices and/or b-sheets are folded up to form a compact globular molecule held together by intramolecular bonds. Figure 2.19c

Quaternary structure of a functional prealbumin
molecule. Two identical prealbumin subunits join head to tail to form the dimer. (d) Quaternary structure: Two or more polypeptide chains, each with its own tertiary structure, combine to form a functional protein. Figure 2.19d

Fibrous and Globular Proteins
Fibrous (structural) proteins Strandlike, water insoluble, and stable Examples: keratin, elastin, collagen, and certain contractile fibers

Fibrous and Globular Proteins
Globular (functional) proteins Compact, spherical, water-soluble and sensitive to environmental changes Specific functional regions (active sites) Examples: antibodies, hormones, molecular chaperones, and enzymes

Protein Denaturation Shape change and disruption of active sites due to environmental changes (e.g., decreased pH or increased temperature) Reversible in most cases, if normal conditions are restored Irreversible if extreme changes damage the structure beyond repair (e.g., cooking an egg)

Enzymes WITHOUT ENZYME WITH ENZYME Activation energy required
Less activation energy required Reactants Reactants Product Product Figure 2.20

Product (P) e.g., dipeptide
Substrates (S) e.g., amino acids Energy is absorbed; bond is formed. Water is released. Peptide bond + H2O Active site Enzyme-substrate complex (E-S) Enzyme (E) Enzyme (E) 1 Substrates bind at active site. Enzyme changes shape to hold substrates in proper position. Internal rearrangements leading to catalysis occur. 2 3 Product is released. Enzyme returns to original shape and is available to catalyze another reaction. Figure 2.21, step 3

Enzymes What is an enzyme? What is a catalyst What is Ea?
Protein Biologic catalyst What is a catalyst Substance that speeds up a reaction What is Ea? Energy of activation Enzymes do what to a reaction? Lower energy of activation (heat, mechanical, chemical, etc) Speeds up rxn On what does an enzyme act? Its substrate Enzymes are __________ for their substrates? Specific

Nucleic Acids DNA and RNA Contain C, O, H, N, and P
Largest molecules in the body Contain C, O, H, N, and P Building block = nucleotide, composed of N-containing base, a pentose sugar, and a phosphate group

Deoxyribonucleic Acid (DNA)
Four bases: adenine (A), guanine (G), cytosine (C), and thymine (T) Double-stranded helical molecule in the cell nucleus Provides instructions for protein synthesis Replicates before cell division, ensuring genetic continuity

(c) Computer-generated image of a DNA molecule
Sugar: Deoxyribose Base: Adenine (A) Phosphate Thymine (T) Sugar Phosphate Adenine nucleotide Thymine nucleotide Hydrogen bond (a) Deoxyribose sugar Sugar-phosphate backbone Phosphate Adenine (A) Thymine (T) Cytosine (C) Guanine (G) (b) (c) Computer-generated image of a DNA molecule Figure 2.22

Ribonucleic Acid (RNA)
Four bases: adenine (A), guanine (G), cytosine (C), and uracil (U) Single-stranded molecule mostly active outside the nucleus Three varieties of RNA carry out the DNA orders for protein synthesis messenger RNA, transfer RNA, and ribosomal RNA

True / False Chemical properties are determined primarily by neutrons.
No chemical bonding occurs between the components of a mixture. Buffers resist abrupt and large changes in the pH of the body by releasing or binding ions. All organic compounds contain carbon. A dipeptide can be broken into two amino acids by dehydration synthesis. The lower the pH, the higher the hydrogen ion concentration. Covalent bonds are generally less stable than ionic bonds. Hydrogen bonds are comparatively strong bonds. The fact that no chemical bonding occurs between the components of a mixture is the chief difference between mixtures and compounds.

True / False The pH of body fluids must remain fairly constant for the body to maintain homeostasis A charged particle is generally called an ion. Isotopes differ from each other only in the number of electrons contained. About 60% to 80% of the volume of most living cells consists of organic compounds. Lipids are a poor source of stored energy. Current information theorizes that omega-3 fatty acids decrease the risk of heart disease. Glucose is an example of a monosaccharide. A molecule consisting of one carbon atom and two oxygen atoms is correctly written as CO2.

Multiple Choice Choose the statement that is false or incorrect.
A) In chemical reactions, breaking old bonds requires energy and forming new bonds releases energy. B) Exergonic reactions release more energy than they absorb. C) A key feature of the body’s metabolism is the almost exclusive use of exergonic reactions by the body. D) Endergonic reactions absorb more energy than they release. A chemical reaction in which bonds are broken is usually associated with ________. A) a synthesis B) the consumption of energy C) the release of energy D) forming a larger molecule What happens in redox reactions? the reaction is always easily reversible B) the electron acceptor is oxidized both decomposition and electron exchange occur D) the electron donor is reduced Choose the answer that best describes fibrous proteins A) are usually called enzymes B) are very stable and insoluble in water C) rarely exhibit secondary structure D) are cellular catalysts

Multiple Choice In liquid XYZ, you notice that light is scattered as it passes through. There is no precipitant in the bottom of the beaker, though it has been sitting for several days. What type of liquid is this? A) suspension B) solution C) mixture D) colloid Atom X has 17 protons. How many electrons are in its valence shell? A) 10 B) 5 C) 3 D) 7 Which protein types are vitally important to cell function in all types of stressful circumstances? A) catalytic proteins B) molecular chaperones C) regulatory proteins D) structural proteins If atom X has an atomic number of 74 it would have which of the following? A) 37 protons and 37 neutrons B) 37 protons and 37 electrons C) 74 protons D) 37 electrons What does the formula C6H12O6 mean? A) There are 6 calcium, 12 hydrogen, and 6 oxygen atoms. B) There are 12 hydrogen, 6 carbon, and 6 oxygen atoms. C) The substance is a colloid. D) The molecular weight is 24. Two good examples of a colloid would be Jell-O® and ________. A) cytosol B) blood C) urine D) toenails

Multiple Choice An atom with a valence of 3 may have a total of ________ electrons. A) 3 B) 8 C) 17 D) 13 The chemical symbol O=O means ________. A) zero equals zero B) the atoms are double bonded C) both atoms are bonded and have zero electrons in the outer orbit D) this is an ionic bond with two shared electrons What is a dipole? A) a type of reaction B) a type of bond C) an organic molecule D) a polar molecule Amino acids joining together to make a peptide is a good example of a(n) ________ reaction. A) decomposition B) reversible C) exchange D) synthesis Which of the following is not considered a factor in influencing a reaction? A) time B) concentration C) particle size D) temperature Which of the following is not an electrolyte? A) NaOH B) HCl C) H2O D) Ca2CO3

Test Review – Exam 2 Chapter 2

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