Water Properties
Water molecules form hydrogen bonds because oxygen is more electronegative than hydrogen. Identify the molecular property that results from this unequal sharing of electrons.
Answer: What is polarity?
Identify the monomer from which polysaccharides are constructed.
What is a monosaccharide?
Identify the monomers that are joined to form a polypeptide.
What are amino acids?
Identify the general property of lipids that causes them to interact poorly with water.
What is nonpolar/hydrophobic?
Identify the monomer that contains a five-carbon sugar, phosphate group, and nitrogenous base.
What is a nucleotide?
Carbon can form many different biological molecules because each carbon atom can form this many covalent bonds.
What is four covalent bonds?
Describe the difference between cohesion and adhesion in water.
What is cohesion = attraction among water molecules, while adhesion = attraction between water and other polar surfaces?
Describe how monosaccharides are related to polysaccharides.
What is monosaccharides are covalently joined to form polysaccharides, which may be linear or branched?
Identify the covalent bond formed between the carboxyl group of one amino acid and the amino group of another.
What is a peptide bond?
Distinguish a saturated fatty acid from an unsaturated fatty acid based on carbon-carbon bonding.
What is saturated fatty acids have only single C-C bonds, while unsaturated fatty acids have at least one C=C double bond?
Identify the sugar found in DNA and the sugar found in RNA.
What are deoxyribose in DNA and ribose in RNA?
Identify the functional group -OH and describe a property it can contribute to a molecule.
What is the hydroxyl group; it can increase polarity and interaction with water?
Explain why water has a relatively high specific heat capacity.
What is hydrogen bonds absorb energy before water molecules increase substantially in kinetic energy, resisting rapid temperature change?
A polymer is broken into smaller carbohydrate units by adding water across a covalent bond. Identify the reaction.
What is hydrolysis?
An amino acid contains a central carbon, H, amino group, carboxyl group, and a variable group. Identify the component that differs among amino acids.
What is the R group?
Predict which fatty acid is more likely to be liquid at room temperature: one with no C=C double bonds or one with several C=C double bonds.
What is the fatty acid with several double bonds, because greater unsaturation is associated with greater fluidity?
State the complementary DNA base pairs and identify the type of interaction that holds paired bases together.
What are A-T and C-G, held together by hydrogen bonds?
Identify the functional group C=O and name the two common molecular arrangements in which it occurs.
What is the carbonyl group; it occurs in aldehydes and ketones?
Explain how water's high heat of vaporization contributes to temperature regulation in an organism.
What is evaporation removes relatively high-energy water molecules, producing evaporative cooling and helping stabilize body temperature?
Two monosaccharides become covalently linked while H is removed from one and OH from the other. Identify the process and its product besides the larger molecule.
What is dehydration synthesis, which releases the equivalent of a water molecule?
Explain how the chemical properties of amino-acid R groups influence protein structure.
What is hydrophobic/nonpolar, hydrophilic/polar, and ionic R groups form different interactions that influence folding and function?
Explain why a cis C=C double bond can change the physical properties of a lipid.
What is the double bond creates a kink that reduces tight packing of fatty acid tails, increasing fluidity?
Explain what it means for the two strands of DNA to be antiparallel.
What is the strands run in opposite orientations, with one oriented 5' to 3' relative to the other?
Identify the -COOH functional group and explain why it can behave as an acid.
What is the carboxyl group; it can donate H+, leaving a negatively charged form?
A plant transports water upward through narrow xylem. Explain how cohesion and adhesion together contribute to this movement.
What is cohesion maintains a continuous water column and adhesion attracts water to xylem walls, supporting capillary action?
A carbohydrate polymer can be linear or highly branched. Explain how differences in covalent linkages can produce these different structures.
What is different positions/types of covalent linkages among monosaccharides produce different polymer arrangements and branching patterns?
Identify the level of protein structure represented by alpha-helices and beta-pleated sheets and explain what stabilizes these structures.
What is secondary structure, stabilized primarily by hydrogen bonds between atoms of the polypeptide backbone?
Explain why fats can function effectively in long-term energy storage and insulation in organisms.
What is fats store chemical energy and, when accumulated in tissues, reduce heat loss and provide insulation?
During nucleic acid synthesis, identify the end to which new nucleotides are added.
What is the 3' end of the growing strand?
Identify the -NH2 functional group and explain how its ability to accept H+ affects its chemical behavior.
What is the amino group; accepting H+ allows it to act as a base and become positively charged?
A large lake warms and cools more slowly than nearby land. Explain this observation using water's molecular interactions.
What is extensive hydrogen bonding gives water high specific heat, so substantial energy is required to change its temperature?
Predict what happens to the number of covalent bonds between monomers during hydrolysis of a polysaccharide, and justify your prediction.
What is the number decreases because water is added to cleave covalent bonds between monomers?
Explain how a change in the amino-acid sequence can alter a protein's tertiary structure.
What is a sequence change can alter R-group interactions such as hydrogen bonds, ionic interactions, hydrophobic interactions, or disulfide bridges, changing folding?
Compare a fat rich in saturated fatty acids with an oil rich in unsaturated fatty acids and explain their likely states at room temperature.
What is the saturated fat is more likely solid, while the unsaturated oil is more likely liquid because double-bond kinks reduce packing?
Compare DNA and RNA with respect to sugar, one nitrogenous base, and typical number of strands.
What is DNA has deoxyribose, thymine, and is typically double stranded; RNA has ribose, uracil, and is typically single stranded?
Identify the -SH functional group and explain how it can contribute to protein structure.
What is the sulfhydryl group; two sulfhydryl-containing side chains can form a disulfide bridge that stabilizes protein structure?
Ice is less dense than liquid water. Explain how hydrogen bonding produces this property and predict one biological consequence for an aquatic ecosystem.
What is hydrogen bonds hold water molecules farther apart in an ordered solid lattice; floating ice can insulate liquid water below and reduce complete freezing?
A cell must rapidly mobilize glucose from a carbohydrate storage polymer. Predict how a highly branched polymer could facilitate this process compared with a strictly linear polymer.
What is branching provides more accessible ends where enzymes can remove glucose units, allowing faster mobilization?
A protein loses its tertiary structure after disruption of ionic and hydrogen-bond interactions but its peptide bonds remain intact. Predict which level of structure is most directly preserved.
What is primary structure, because the amino-acid sequence linked by peptide bonds remains intact?
A membrane contains phospholipids with hydrophilic heads and hydrophobic tails. Explain why these molecules spontaneously organize into a bilayer in water.
What is polar heads interact with water while nonpolar tails avoid water and associate inward, producing a bilayer?
A DNA segment contains 30% adenine. Using base-pairing relationships, predict the percentages of thymine, cytosine, and guanine.
What are 30% thymine, 20% cytosine, and 20% guanine?
Distinguish the phosphate and methyl functional groups in terms of charge/polarity and one biological role.
What is phosphate is negatively charged/polar and occurs in nucleotides and phospholipids; methyl is nonpolar and can alter molecular shape or regulation when attached to biological molecules?
A mutation changes a membrane protein so that several nonpolar amino-acid side chains exposed to water are replaced by charged side chains. Predict how this could alter interactions with the surrounding water and justify your prediction.
What is water interactions would likely increase because charged/polar groups interact favorably with polar water through electrostatic interactions and hydrogen bonding?
An enzyme hydrolyzes a branched polysaccharide. Predict the direct molecular products of each bond-cleavage event and explain the role of water in the reaction.
What is smaller carbohydrate units form; water is split so H is added to one product and OH to the other as the covalent bond is cleaved?
A single amino-acid substitution replaces a hydrophobic R group buried inside a globular protein with an ionic R group. Predict a likely effect on protein function and justify it structurally.
What is function may change because the substitution can disrupt hydrophobic packing and introduce new ionic/water interactions, altering tertiary structure and therefore protein shape?
Researchers lower the proportion of unsaturated fatty acids in a cell membrane. Predict the effect on membrane fluidity at the same temperature and justify your prediction.
What is membrane fluidity would decrease because fewer double-bond kinks allow fatty acid tails to pack more tightly?
A mutation changes a nucleotide sequence but does not alter the sugar-phosphate backbone. Explain which molecular feature stores the changed genetic information and why the backbone can remain structurally intact.
What is the sequence of nitrogenous bases stores the information; nucleotides can differ in base identity while the covalently linked sugar-phosphate backbone remains continuous?
A molecule contains hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, phosphate, and methyl groups in different regions. Predict why changing one functional group could alter the molecule's biological activity.
What is each functional group contributes characteristic polarity, charge, reactivity, or intermolecular interactions; changing one can alter molecular shape, solubility, binding, or chemical reactivity and therefore function?