|The element present in all organic molecules is___.||Carbon|
|The large diversity of shapes of biological molecules is possible because of the extensive presence of ____ in the molecules.||Carbon|
– With four electrons to share, carbon-based molecules can be multi branching and 3D variable.
|How many electron pairs does carbon share in order to complete its valence shell.||4|
|Why are hydrocarbons insoluble in water?||The majority of their bonds are non-polar covalent carbon-to-hydrogen linkages.|
|Which of the following is a hydrocarbon?||C3H8|
-This is a typical hydrocarbon with single covalent bonds; the number of hydrogen atoms is equal to two times the number of carbon atoms plus 2.
|Molecules that have the same chemical formula (same numbers of each atom) but different 3D shapes are called_____.||isomers|
-Isomers of carbon compounds can arise in several different ways.
|How do isomers differ from one another?||Isomers differ in the arrangement or bonding of atoms.|
-Isomers may differ in the covalent arrangements of their atoms or the position of double bonds within the molecule and thus have different chemical properties.
|Which of the following best describes cis-trans isomers?||They differ in their spatial arrangement around inflexible double bonds.|
-Cis-trans isomers maintain the same covalent partnerships, but the atoms may be arranged differently.
|Variations in the reactive properties of different organic molecules are most closely associated with_____.||The presence or absence of functional groups.|
-Functional groups are the most common participants in chemical reactions.
|Citric acid makes lemons taste sour. Which of the following is a functional group that would cause a molecule such as citric acid to be acidic?||Carboxyl|
-The carboxyl group can release a hydrogen ion when in solution.
|Which statement about a methyl functional group is correct?||A methyl group consists of a carbon bonded to three hydrogen atoms.|
-A methyl group consists of a carbon covalently bonded to three hydrogen atoms.
|Most organic compounds contain carbon and ____.||Hydrogen|
-In fact, some argue that carbon dioxide should not be considered an organic molecule because it does not contain hydrogen.
|Organic chemistry is currently defined as||The study of carbon compounds.|
|Vitalism gave way to mechanism, the view that____.||Physical and chemical laws govern living systems.|
-Living things are subject to physical and chemical laws. They so not exist outside of them.
|What are the six most important chemical elements of life?||Carbon, nitrogen, oxygen, hydrogen, phosphate, sulfur.|
-All of these elements are capable of forming strong covalent bonds, important in building large, complex molecules.
|Which of the following is an organic molecule?||CH4|
-Compounds containing carbon are said to be organic.
|Which statement helps most to explain why life is based on carbon compounds?||C-C bonds are as strong as C-O bonds.|
-C is the only element that bonds with its own kind about as strongly as it bonds with other elements. That, plus C’s ability to form 4 bonds, makes it possible to build stable, varied biological molecules.
|L-dopa is used to treat____.||Parkinson’s disease|
-People with Parkinson’s disease lack dopamine.
|What kind of effect does R-dopa have on Parkinson’s disease?||None|
-R-dopa has no effect on Parkinson’s disease.
|Enantiomers are molecules that_____.||Are mirror images.|
|Geometric isomers are molecules that _____.||Differ in the arrangement of their atoms about a double bond.|
|A molecule has one carbon-carbon double bond and four monovalent atoms or group. How many different cis-trans isomers exist for this molecule?||2|
-Only 2 cis-trans isomers exist.
|Identify the functional groups.||Amino and carboxyl are functional groups.|
|Which of the following functional groups increases the solubility of organic compounds in water?||-COH|
-All of the listed functional groups are hydrophilic and thus increase the solubility of organic molecules in water.
|Which statement is true of organic molecules?||An organic molecule can have many functional groups.|
-If the molecule is large, it may have thousands of functional groups.
|Choose the pair of terms that correctly completes this sentence about functional groups in organic chemistry; Carboxyl is to ______as_______is to base.||Acid…Amino|
-A carboxyl group has acidic properties because it can donate a proton (hydrogen ion) to a solution. The amino group acts as a base because it can pick up or accept a proton (hydrogen ion) from a solution.
|Which of the following groups is capable of hydrogen bonding with an oxygen atom or another functional group?||-Hydroxyl group|
-All of the listed functional groups are polar, and thus capable of hydrogen bonding with the oxygen of another molecule.
|Covalent bonds hold atoms together because they…||-Fill shells without giving atoms much charge.|
-Bring electrons closer to protons.
-Electron-sharing brings electrons closer to nuclei and it fills shells without giving the atoms much charge. Both factors stabilize the bond.
|In molecules, C,H,O and N atoms usually make _,_,_, and _, bonds respectively.||4,1,2,3|
|An atom’s atomic number is 7. Its valence is most likely..||3|
-The neutral atom has 7 electrons. Two electrons fill the first shell, and 5 go into the second (valence) shell. The atom needs 3 more electrons to fill the valence shell.
|By making two covalent bonds, an O atom (with 8 protons) fills its valence shell. Why does the atom’s charge stay close to zero?||Shared electrons aren’t always near oxygen.|
-Oxygen keeps 6 electrons to itself. The 4 shared electrons migrate between O and the other atoms, thus contributing 4 half-charges to oxygen. This gives oxygen about 8 units of negative charge, balancing the atom’s 8 protons.
|In a double covalent bond, a carbon atom shares..||Electrons in two orbitals.|
– A double bond involves two orbitals, each with a shared pair of electrons.
|Two C atoms form a double bond. Each C is bound to two H atoms. Which statement is true?||All the atoms lie in a plane.|
-The double bond limits all the atoms to a plane.
|Partial charges occur when..||Atoms share electrons unequally.|
-Each kind of atom has a different attraction for electrons. Thus, atoms of different kinds share electrons unequally. That gives one atom a partial negative charge; the other atom a partial positive charge.
|To fill the valence shell, an electrically neutral, unbonded atom with atomic number 8 must add…||2 electrons|
– The neutral atom has 8 electrons. Two electrons fill the first shell, and 6 go into the second (valence) shell. Two more electrons would fill the valence shell.
|Which answer helps to explain why carbon atoms tend to make 4 covalent bonds?||The valence shell needs 8 electrons.|
-Without help, C can only hold 4 electrons in the valence shell. To fill the shell, 4 more electrons must be shared, making 4 covalent bonds.
|An electrically neutral molecule has the formula C3H4O2N. If the carbon atoms form the usual number of bonds, how many covalent bonds will each hydrogen atom have with other atoms in the molecule?||1|
|A(n)____refers to two or more atoms held together by covalent bonds.||Molecule|
-Two or more atoms held together by covalent bonds.
|Which of the following individuals is most likely to be a chimera?||A woman who has had children.|
|You are a geneticist interested in studying the mutation that leads to “mosaic animals.” Which of the following types of cells should you study?||Skin|
|Which of the following diseases is the result of mosaicism in specific cells?||Pancreatic cancer|
|You are a doctor studying genetic mistakes in fibroblasts. What type of tissue do you specialize in?||Connective|
|Which of the following is true?||Multiple DNA samples from the same individual may not always match|
|Ammonia reacts with water as shown below. Which statement best explains why ammonia is considered to be a base?||Bases are compounds that remove H+ from solutions.|
– In becoming NH4+, ammonia takes on H+. Removing H+ from a solution is the hallmark of a base.
|Which of the following can be considered bases?||Na2CO3, KOH|
– Both sodium carbonate and potassium hydroxide are bases.
|Compounds that release OH+ are bases because…||OH- combines with H+ and removes it from solution.|
-This behavior of OH- earns the title of “base” for compounds that release OH-.
|To determine whether a base is weak or strong,…||Look for undissociated molecules of base.|
-Strong bases dissociate completely in solution, weak bases don’t.
|Which of the following can be considered strong bases?||NaOH|
-This is the only base that dissociates completely in water.
|Water readily sticks to many other substances, a property called____.||Adhesion|
|Water striders are common insects that can skip across the surface of ponds and streams. This lifestyle is enabled by water’s ____.||Cohesion and resulting surface tension.|
|Which best describes how charges are distributed on a water molecule?||The oxygen end is negative relative to the end with the 2 hydrogen atoms.|
|Relative to other substances, water tends to resist changes in temperature. Why?||Water is highly cohesive. Its molecules tend to resist increases in their motion. When water is heated, some of the energy is used to disturb the hydrogen bonds between neighboring molecules.|
|Water is sometimes called the “universal solvent”. Is that accurate?||For the most part. Water readily dissolves most substances, but nor hydrophobic ones.|
|What feature of large biological molecules explains their great diversity?||The many ways that monomers of each class of biological molecule can be combined into polymers.|
-Biological molecules belong to four main classes, and are constructed from only 40-50 common monomers (and a few rare ones) made of only a few of the 92 naturally occurring elements. The diversity of biological molecules is due to differences in the arrangements of the monomers in each molecule.
|Select the statement that is incorrect.||All carbohydrates have the general formula Cn(H2O)n.|
-This formula only applies to simple sugars, which are equal parts carbon and water. Complex sugars, which do not have this general formula, are also carbohydrates.
|Complete the following sentences about carbohydrates.|
-A carbohydrate that yields many monosaccharides when hydrolyzed is a _____.
-A _____cannot be hydrolyzed any further.
-Lactose, the sugar in milk, is a ____, because it can be split into two monosaccharides.
-A simple sugar is composed of equal parts carbon and water, which gave rise to the general name of any sugar as a ____.
|Glycogen is _____.||A polysaccharide found in animals.|
– Animal store energy in the form of glycogen.
-Maltose is the disaccharide formed when two glucose molecules are linked by dehydration synthesis.
|Which of these is a source of lactose?||Milk|
-Lactose is the sugar found in milk.
|Which of these is a polysaccharide?||Cellulose|
-Cellulose is a carbohydrate composed of many monomers.
|______ is the most abundant organic compound on Earth.||Cellulose|
-Cellulose, a component of plant cell walls, is the most abundant organic compound found on earth.
|Humans can digest starch but not cellulose because||Humans have enzymes that can hydrolyze the α glycosidic linkages of starch but not the ß glycosidic linkages of cellulose.|
|Classify these amino acids as ,acidic, basic, neutral polar, or neutral nonpolar.||Acidic-|
Neutral polar- Glutamine
Neutral nonpolar- Alanine
|Classify these amino acids as acidic, basic, neutral polar, or neutral nonpolar.||Acidic-|
Neutral polar- Serine
Neutral nonpolar- Phenylalanine
|Classify these amino acids as acidic, basic, neutral polar, or neutral nonpolar.|
Drag each item to the appropriate bin.
|Acidic- Glutamic Acid|
Neutral polar- Theonine
Neutral nonpolar- Trytophan
|Proteins are polymers of _____.||Amino acids|
-Proteins are polymers of amino acids
|What type of bond joins the monomers in a protein’s primary structure?||Peptide|
-The amino acids of a protein are linked by peptide bonds.
|The secondary structure of a protein results from____.||Hydrogen bonds|
-Electronegative oxygen and nitrogen atoms leave hydrogen atoms with partial positive charges.
|Tertiary structure is NOT directly dependent on_____.||Peptide bonds|
-Peptide bonds link together the amino acids of a protein’s primary structure.
|Complete the following vocabulary exercise relating to the level of structure in protein.|
1.______ Structure describes the alpha-helices and beta-sheets that are formed by hydrogen bonding between backbone atoms located near each other in the polypeptide chain.
2.______Structure is the sequence of amino acids in a protein.
3._____Structure is achieved when a protein folds into a compact, 3D shape stabilized by interactions between side-chain R groups of amino acids.
4.______Structure is the result of two or more protein subunits assembling to form a larger, biologically active protein complex.
|Which polymers are composed of amino acids?||Proteins|
-Proteins are composed of amino acids joined together.
|Which of the following is not attached to the central carbon atom in an amino acid?||An oxygen|
-The central carbon atom in an amino acid is bonded to an amino functional group, a carboxyl functional group, a side chain, and hydrogen.
|Which part of an amino acid is always acidic?||Carboxyl functional group|
-The carboxyl group (COOH) contains two oxygen atoms that tend to pull electrons away from the hydrogen atom, so this group tends to lose a proton and is acidic.
|Which monomers make up RNA?||Nucleotides|
-Nucleotide monomers make up nucleic acids.
|Which of the following statements about the formation of polypeptide from amino acids is true?||A bond forms between the carboxyl functional group of one amino acid and the amino functional group of the other amino acid.|
-A hydroxyl group is removed from the carboxyl group of one amino acid and hydrogen is removed from the amino group of the other amino acid allowing a bond to form between the two groups.
|True or false? Enzymes in the digestive tract catalyze hydrolysis reactions.||True|
-Enzymes in the digestive tract break down food molecules, which is a process that occurs by hydrolysis.
|Which of the following statements concerning saturated fats is not true?||They have multiple double bonds in the carbon chains of their fatty acids.|
|Why are human sex hormones considered to be lipids?||They are not soluble in water.|
|What does cholesterol have in common with sex hormones?||Four linked rings|
-All steroids have four linked rings.
|For good health, you don’t want your body to run the LDL part of this diagram faster than the HDL part because…||LDL cholesterol is stored; HDL cholesterol is destroyed.|
-If LDL exceeds HDL, your body is probably storing excess cholesterol, which may clog the arteries and cause heart disease.
|The sex hormones estradiol and testosterone belong to which class of molecules?||Lipids|
-Steroids, such as estradiol and testosterone, are lipids based on their insolubility in water. THe molecules are characterized by a carbon skeleton consisting of four fused rings of carbon atoms.
|High cholesterol levels are considered a major risk factor for heart disease. If it is so bad for humans, why does the body make cholesterol in the first place?||Cholesterol is the precursor for many important molecules such as sex hormones.|
– Cholesterol is the basis for many steroid molecules, including sex hormones.
|Can you complete these sentences about lipids?|
1. Lipids are diverse compounds that are grouped together because they are ____.
2. A fat molecule is composed of two types of smaller molecules: ______ and fatty acids.
3. A fatty acid consists of a _____ and a long hydrocarbon chain.
4. _______ have one or more double bonds in their hydrocarbon chains and are usually found in vegetable oils.
5. The hydrocarbon chains of ______ are not kinked, and thus pack closely together, making animal fats solid at room temperature.
6. _______ are a major component of cell membranes. They form a bilayer with their hydrophobic tails mingling together and their hydrophilic heads facing the watery environment on both sides of the membrane.
7. ______ are lipids with a structure consisting of four fused rings. Many sex hormones are made from this type of lipid.
4. Unsaturated fatty acids
5. Saturated fatty acids
|How many amino acids differ between the monkey and the human sequences?||8|
|How many amino acids differ between the gibbon and the human sequences?||2|
|What percentage of monkey ß- globin amino acids are identical to the human sequence?||94.5%|
|What percentage of gibbon ß- globin amino acids are identical to the human sequence?||98.6%|
|Based on the ß- globin alignment, identify the best hypothesis about how humans are related to monkeys and gibbons.||Gibbons are more closely related to humans than monkeys because the gibbon ß- globin sequence is a closer match with the human sequence.|
|What other evidence could you use to analyze evolutionary relatedness among gibbons, monkeys, and humans?||The amino acid sequences of other proteins from gibbons, monkeys, and humans.|
|What do the three main forces that stabilize protein tertiary structure have in common?||They involve the side chains.|
– The side chains are always involved. That’s one distinction between secondary and tertiary structure.
|Among the forces that stabilize protein tertiary structure, hydrogen bonds are especially important because they are…||More numerous than the other forces.|
– Hydrogen bonds are weak individually, but they are much more numerous than the other forces.
|Which fact results from the presence of both polar and non-polar side chains in a protein.||Water has a strong effect on tertiary structure.|
– United by hydrogen bonds, water forms a cage that binds to the polar side chains while rejecting the nonpolar side chains. THis keeps the protein folded with the polar side chains at the surface and nonpolar side chains in the interior.
|The sequence of polar and nonpolar side chains has a strong effect on a protein’s folding mainly because…||Water attracts polar but not nonpolar groups.|
– The great majority of proteins reside in water. Because of the attractions, the protein folds with its polar groups on the surface and its nonpolar groups in the interior. THat makes the folding dependent on the locations of polar and nonpolar groups.
|The graph shows how the rate of action by a certain protein responds to temperature. The decrease between 43*C and 60*C probably results from…||Breaking hydrogen bonds.|
-It doesn’t take much to disrupt the weak hydrogen bonds that keep the protein folded in its functional shape.
|When a protein has been unfolded enough to lose its function, the protein has been…||Denatured|
|The amino acid lysine has an amino group in its side chain. In a protein, a scientist replaced every lysine with serine (side chain-CH2OH). THe alteration made the protein’s folding…||Less sensitive to pH.|
– Changes in pH affect the ionization of amino groups much more than -CH2OH groups.
|Which factor is most important in determining a protein’s optimum pH?||The locations of side-chain carboxyl groups.|
– The effect of pH depends on the number and locations of ionizationable side chains, including those with carboxyl groups. pH affects their ionization, which determines the balance of attractions and repulsions between side chains.
|Why don’t cells rely more on disulfide bridges to stabilize the folding of proteins?||They make the protein rigid. Many proteins change their shape as they work.|
– There may be additional reasons for the low number of disulfide bridges, but one reason is the need for changes in shape. Disulfide bridges make the folding rigid.
|To make a disulfide bridge, its necessary to…||Remove two H atoms.|
-The two cysteines start with -SH groups, they end up linked as -S-S.
|A certain protein is not very sensitive to pH. It may have many side chains with ____ groups.||-CH2OH|
-These groups don’t ionize readily, so their effects on folding don’t change much when the pH is altered.
|The helical foldings of proteins are stabilized mainly by bonds between…||CO and NH.|
– Hydrogen bonds between these groups keep the helix coiled.
|Which of the following is true of pleated sheet foldings within a polypeptide?||They depend in regular occurrence of CO and NH.|
– Occurring at regular intervals along the backbone, these groups stabilize the sheet by forming many hydrogen bonds between neighboring segments of the polypeptide.
|What will probably be the effect on a protein if you replace the amino acid proline with the amino acid glycine (side chain -H) at several points?||The altered protein will have longer helices than before.|
-Helical segments come to an end when they meet a proline residue, because proline grips the backbone in two places. Remove proline, and the helix can continue.
|The helical foldings in proteins…||Are kept folded by hydrogen bonds.|
-The hydrogen bonds form between c=O and N-H groups of the backbone.
|The helical foldings of proteins are stabilized by bonds between…||CO and NH|
-Hydrogen bonds between these groups keep the helix coiled.