Cell Bio Chapter 2 (Exam 1)

Which of the following monomer building blocks is necessary to assemble selectively permeable boundaries around and inside cells? amino acids sugars nucleotides oligosaccharides fatty acids

fatty acids

Match each term related to the structure of nucleic acids (A-I) with one of the descriptions provided. deoxyribose

five carbon sugar found in DNA

Match each term related to the structure of nucleic acids (A-I) with one of the descriptions provided. ribose

five-carbon sugar found in RNA

Hydrogen bonds provide water with unique properties that include:

high surface tension cohesiveness high specific heat of vaporization

Match each term related to the structure of nucleic acids (A-I) with one of the descriptions provided. glycosidic bond

linkage between the sugar and the base

A protein chain folds into its stable and unique three-dimensional structure, or conformation, by making many noncovalent bonds between different parts of the chain. Such noncovalent bonds are also critical for interactions with other proteins and cellular molecules. From the list provided, choose the class(es) of amino acids that are most important for the interactions detailed below. localizing an ―integral membrane‖ protein that spans a lipid bilayer

nonpolar

Match each term related to the structure of nucleic acids (A-I) with one of the descriptions provided. nucleotide

sugar linked to a base and a phosphate

Match each term related to the structure of nucleic acids (A-I) with one of the descriptions provided. nucleoside

sugar unit linked to a base

Match each term related to the structure of nucleic acids (A-I) with one of the descriptions provided. phosphoester bond

the linkage between the 5' sugar hydroxyl and a phosphate group

Match each term related to the structure of nucleic acids (A-I) with one of the descriptions provided. phosphodiester bond

the linkage between two nucleotides

A protein chain folds into its stable and unique three-dimensional structure, or conformation, by making many noncovalent bonds between different parts of the chain. Such noncovalent bonds are also critical for interactions with other proteins and cellular molecules. From the list provided, choose the class(es) of amino acids that are most important for the interactions detailed below. tightly packing the hydrophobic interior core of a globular protein

nonpolar

Unlike other electrostatic attractions (such as those that involve ions), hydrogen bonds are unique because:

they require specific distance AND orientation

A protein chain folds into its stable and unique three-dimensional structure, or conformation, by making many noncovalent bonds between different parts of the chain. Such noncovalent bonds are also critical for interactions with other proteins and cellular molecules. From the list provided, choose the class(es) of amino acids that are most important for the interactions detailed below. forming ionic bonds with negatively charged DNA

basic

Single sugar molecules, or monosaccharides, can form disaccharides or oligosaccharides:

by undergoing condensation reactions between monosaccharidwes

A molecule is composed of chemical groups that are ALL non-polar. The following characteristics would be expected from this molecule EXCEPT: There could be a large number of C-H bonds There could be a large number of C-C bonds There could be a large number of O-H bonds It is hydrophobic

there could be a large number of O-H bonds

A protein chain folds into its stable and unique three-dimensional structure, or conformation, by making many noncovalent bonds between different parts of the chain. Such noncovalent bonds are also critical for interactions with other proteins and cellular molecules. From the list provided, choose the class(es) of amino acids that are most important for the interactions detailed below. binding to another water-soluble protein

uncharged polar, basic, and acidic

____________ are characterized as a form of electrical attraction caused by fluctuating electric charges that arise whenever two atoms come within a very short distance of each other.

van der Waals attractions

Polar covalent bonds are formed when the electrons in the bond are not shared equally between the two nuclei. Which one of these molecules contains polar bonds? methane water propane molecular oxygen

water

A protein chain folds into its stable and unique three-dimensional structure, or conformation, by making many noncovalent bonds between different parts of the chain. Such noncovalent bonds are also critical for interactions with other proteins and cellular molecules. From the list provided, choose the class(es) of amino acids that are most important for the interactions detailed below. forming hydrogen bonds to aid solubility in water

uncharged polar

What is the difference between a monosaccharide, a disaccharide, an oligosaccharide, and a polysaccharide? How do these sugars function in the cell?

A monosaccharide is the simplest sugar and has the general formula (CH2O)n. A disaccharide consists of two monosaccharides linked by a covalent bond. An oligosaccharide is a chain of monosaccharides, usually between 3 and 10 subunits long. A polysaccharide is sugar that contains hundreds or thousands of subunits. Simple sugars, such as the monosaccharide glucose, are used as a source of energy in the cell. Simple polysaccharides, such glycogen in animals and starch in plants, are used as long-term stores of glucose. More complex sugars, such as cellulose in plants and chitin in insects, can be used as mechanical supports.

The molecular weight of ethanol (CH3CH2OH) is 46 and its density is 0.789 g/cm3. A. How many 12-oz (355-mL) bottles of 5% beer could a 70-kg person drink and remain under the legal limit? A 70-kg person contains about 40 liters of water. Ignore the metabolism of ethanol, and assume that the water content of the person remains constant.

A. At the legal limit (17.4 mM), ethanol in 5% beer (0.86 M) has been diluted 49.4-fold (860 mM/17.4 mM). This dilution represents 809 mL in 40 L of body water (40 L/49.4). At 355 mL per beer, this equals 2.3 beers (809 mL/355 mL).

The molecular weight of ethanol (CH3CH2OH) is 46 and its density is 0.789 g/cm3. B. Ethanol is metabolized at a constant rate of about 120 mg per hour per kg body weight, regardless of its concentration. If a 70-kg person were at twice the legal limit (160 mg/100 mL), how long would it take for their blood alcohol level to fall below the legal limit?

B. It would take nearly 4 hours. At twice the legal limit the person would contain 64 g of ethanol [(0.16 g/0.1 L) x (40 L)]. The person would metabolize 8.4 g/hr [(0.12 g/hr kg) x (70 kg)]. Thus, to metabolize 32 g of ethanol (the amount in excess of the legal limit) would require 3.8 hours [(32 g) x (hr/8.4 g)].

Indicate whether the statements below are true or false. If a statement is false, explain why it is false. A strong base is defined as a molecule that can readily remove protons from water.

True

Indicate whether the statements below are true or false. If a statement is false, explain why it is false. Protons are constantly moving between water molecules, which means there is an overall equilibrium between hydroxyl ions and hydronium ions in aqueous solutions.

True

Match each term related to the structure of nucleic acids (A-I) with one of the descriptions provided. phosphoanhydride bond

Linkages between phosphate groups

Equal sharing of electrons yields a(n) __________________ covalent bond.

NONPOLAR

Indicate whether the statements below are true or false. If a statement is false, explain why it is false. Any contently bonded H atom can participate in a hydrogen bond if it comes in close proximity with an oxygen atom that forms part of a water molecule

False. Hydrogen atoms that are covalently bonded to carbon atoms do not participate in hydrogen bonds because these hydrogens have almost no net positive charge.

The covalent bonds that connect the different nucleotides of a DNA strand:

Form between the adenine bases and the 5' and 3' carbons of the deoxyribose sugar molecules Form between the adenine bases and the 1' and 3' carbons of the ribose sugar molecules Form between the phosphate group and the 2' and 3' carbons of the deoxyribose sugar molecules Form between the phosphate group and the 5' and 3' carbons of the ribose sugar molecules

Which functional groups/atoms of an amino acid form the peptide bond between two amino acids? COOH group and the R group (side chain) H2N group and the alpha carbon Alpha carbon and the R group (side chain) H2N group and the COOH group Alpha carbon and the COOH group

H2N group and the COOH group

The amino acids glutamine and glutamic acid are shown in Figure Q2-46. They differ only in the structure of their side chains (circled). At pH 7, glutamic acid can participate in molecular interactions that are not possible for glutamine. What types of interactions are these? *****Figure Q2-46 (a) ionic bonds (b) hydrogen bonds (c) van der Waals interactions (d) covalent bond

(a) ionic bonds

Both DNA and RNA are synthesized by covalently linking a nucleoside triphosphate to the previous nucleotide, constantly adding to a growing chain. In the case of DNA, the new strand becomes part of a stable helix. The two strands are complementary in sequence and antiparallel in directionality. What is the principal force that holds these two strands together? (a) ionic interactions (b) hydrogen bonds (c) covalent bonds (d) van der Waals interactions

(b) hydrogen bonds

DNA and RNA are different types of nucleic acid polymer. Which of the following is true of DNA but not true of RNA? (a) It contains uracil (b) it contains thymine (c) It is single stranded (d) it has 5' to 3' directionality

(b) it contains thymine

The variety and arrangement of chemical groups on monomer subunits contribute to the conformation, reactivity, and surface of the macromolecule into which they become incorporated. What type of chemical group is circled on the nucleotide shown in Figure Q2-45? ******Figure Q2-45 (a) pyrophosphate (b) phosphoryl (c) carbonyl (d) carboxyl

(b) phosphoryl

Larger molecules have hydrogen-bonding networks that contribute to specific, high-affinity binding. Smaller molecules such as urea can also form these networks. How many hydrogen bonds can urea (Figure Q2-36) form if dissolved in water? *********INSERT PIC (a) (b) (c) (d) 6 5 3 4

(a) Urea can form at least six hydrogen bonds in water: two from the oxygen atom and one from each hydrogen atom.

Each nucleotide in DNA and RNA has an aromatic base. What is the principal force that keeps the bases in a polymer from interacting with water? (a) hydrophobic interactions (b) hydrogen bonds (c) covalent bonds (d) van der Waals interactions

(a) hydrophobic interactions

A saturated fatty acid would have the following bonds or functional groups present in the non-polar chain EXCEPT for: C=C bonds C-C bonds C-H bonds CH3 (at the end of the chain)

C=C bonds

Describe the key features of the following chemical interactions: ionic bonds, covalent bonds, hydrogen bonds, van der Waals attractions, electrostatic attractions. Which are the strongest?

Ionic bonds are formed when electrons are donated by one atom to another. Covalent bonds occur when two atoms share a pair of electrons. Hydrogen bonds are noncovalent interactions between a positively charged hydrogen atom and a negatively charged atom, usually oxygen or nitrogen. Hydrogen bonds can form between two molecules or between different parts of a single large molecule. Van der Waals attractions are noncovalent interactions due to fluctuating electrical charges between two atoms that are very close together. Electrostatic attractions are noncovalent interactions that draw together oppositely charged atoms. Covalent bonds are the strongest, and ionic bonds are stronger than hydrogen bonds, which are the strongest of the noncovalent interactions. Although noncovalent interactions--such as ionic bonds, hydrogen bonds, van der Waals attractions, and electrostatic changes--are individually weak, when present in large numbers, they can promote strong and specific binding.

These covalent bonds have a characteristic bond __________________ and become stronger and more rigid when two electrons are shared in a(n) __________________.

LENGTH DOUBLE BOND

As a protein is made, the polypeptide is in an extended conformation, with every amino acid exposed to the aqueous environment. Although both polar and charged side chains can mix readily with water, this is not the case for nonpolar side chains. Explain how hydrophobic interactions may play a role in the early stages of protein folding, and have an influence on the final protein conformation.

One reason that nonpolar groups are excluded from an aqueous environment is that a hydrophobic surface would organize water into a highly structured network of hydrogen bonds, which is energetically unfavorable. So, you would expect that nonpolar amino acids would group together early, forming ―hydrophobic pockets, a‖ while the polar and charged side chains remain at the interface of the surrounding solution. In the final, folded protein, most of the nonpolar amino acids will remain buried inside the protein. This fold is more stable because nonpolar atoms are prevented from contact with water and remain in contact with each other.

When a protein is made, amino acids are linked together through _______________, which are formed by condensation reactions between the carboxyl end of the last amino acid and the ___________________ end of the next amino acid to be added to the growing chain.

PEPTIDE BONDS AMINO

If one atom participating in the bond has a stronger affinity for the electron, this produces a partial negative charge on one atom and a partial positive charge on the other. These __________________ covalent bonds should not be confused with the weaker __________________ bonds that are critical for the three-dimensional structure of biological molecules and for interactions between these molecules.

POLAR NONCOVALENT

Proteins are ______________ built from amino acids, which each have an amino group and a _____________ group attached to the central _______________.

POLYPEPTIDES CARBOXYL α-carbon

Whereas ionic bonds form a(n) __________________, covalent bonds between atoms form a(n) __________________.

SALT MOLECULE

There are twenty possible _______________ that differ in structure and are generally referred to as ―R.‖ In solutions of neutral pH, amino acids are _______________, carrying both a positive and negative charge.

SIDE CHAINS IONIZED

Match each term related to the structure of nucleic acids (A-I) with one of the descriptions provided. Base

The nitrogen-containing aromatic ring

The relative strengths of covalent bonds and van der Waals interactions remain the same when tested in a vacuum or in water. However, this is not true of hydrogen bonds or ionic bonds, whose bond strengths are lowered considerably in the presence of water. Explain these observations.

We estimate bond strengths by measuring the amount of energy needed to break them. As explained in Panel 2-7 (p.78-79) In an aqueous solution, water can form hydrogen bonds with any polar molecules that are capably of forming hydrogen bonds with each other. This formation of bonds with water takes away from the net energy that would be gained from the molecules forming hydrogen bonds with each other, as they would in a vacuum. Similarly, water forms favorable electrostatic interactions with ions, thereby greatly weakening the ionic bonds that form between positive and negative ions in a vacuum (see Panel 2-7). Thus, for example, solid table salt (NaCl) readily dissociates in water, producing separate Na+ and Cl- ions as it dissolves. In contrast, covalent bonds and van der Waals attractions have an intrinsic bond strength that is independent of the aqueous environment, because changes in water molecule associations are not involved in the formation of these two types of bonds.