End of chapter questions Ch. 2-6

Question 1

What happens when a covalent bond forms?

Answer 1

Electron in valence shells are shared between atoms

Question 2

What are the defining characteristics of a condensation reaction?

Answer 2

Two monomers are covalently bonded together and a water molecule is produced

Question 3

Which functional group is known to be used for storing large amounts of chemical energy?

Answer 3

phosphate group

Question 4

What factors determine whether a chemical reaction is spontaneous or not?

Answer 4

potential energy and entropy

Question 5

When nonpolar molecules are mixed with water, they eventually coalesce and form a separate layer. Would entropy be greater in the mixed or the separated state? Explain how entropy increases or decreases as the two layers separate.

Answer 5

Entropy would be greater in the separated state. When nonpolar molecules are mixed with water, a highly ordered cage of water molecules forms around them. As the nonpolar molecules form a separate layer, there are less ordered water molecules in the solution and entropy increases.

Question 6

From what you have learned about water, why coastal regions tend to have milder climates with cooler summers and warmer winters than do inland areas at the same latitude?

Answer 6

In hot water, water absorbs large amounts of heat due to its high specific heat and high heat of vaporization. In cold weather, water releases the large amount of heat that it has absorbed.

Question 7

What two functional groups are bound to the central carbon of every free amino acid monomer?

Answer 7

an amino group and a carboxyl group

Question 8

What type of bond is directly involved in the formation of an α-helix?

Answer 8

hydrogen bonds between amino acid residues

Question 9

What type of information is used to direct different polypeptides to fold into different shapes?

Answer 9

The information present in the order and type of amino acids that make up the polypeptide(ex. primary structure)

Question 10

Which of the following correctly describe an active site? Select T/F

Answer 10

T it is the location in an anzyme where subtrates bi d
F
F
T it is the site on an enzyme where catalysis occurs

Question 11

Explain how molecular chaperones facilitate protein folding in many different polypeptides; each with their own specific shape

Answer 11

molecule chaperones facilitate folding by keeping unfolded proteins from clumping together so that they can fold into the shapes that are determined by the information in their primary structures.

Question 12

Why are proteins not considered to be good candidate for the first living molecule?

Answer 12

They cannot serve as a template for replication

Question 13

Based on what you know of the peptide bonds that link together amino acid residue, why would proline’s side chain reduce the flexibility of the backbone?

Answer 13

Because the ability to regulate protein activity would be impaired. The proteins would be either permanently active or inactive, depending on how they are folded.

Question 14

What are the four nitrogenous bases found in RNA?

Answer 14

A, C, G, U

Question 15

What determine the primary structure of a DNA molecule?

Answer 15

deoxyribonucleotide sequence

Question 16

Evaluate the following statements related to the synthesis of nucleic acids

Answer 16

F
T, Polymerization of nucleic acids occurs by the formation of phosphodiester bonds
F
T, strands in a double helix are synthesized in an antiparallel orientation

The first response is false b/c ribonucleotides are used for RNA, not DNA sythesis. The third response is false b/s pairing occurs between nitrogenous bases, not sugars.

Question 17

Single strands of nucleic acids are directional, meaning that there are two different ends. What functional groups define the two different ends of a strand?

Answer 17

One end has free phosphate group on the 5’ carbon; the other end has a free hydroxyl group bonded to the 3’ carbon

Question 18

What is responsible for the increased stability of DNA compared to RNA?

Answer 18

DNA is a more stable molecule than RNA because it lacks a hydroxyl group on the 2’ carbon and is therefore more resistant to cleavage

Question 19

If nucleotides from DNA of a human were quantified and 30% of them contained the base adenine, what % of them would contain base guanine?

Answer 19

a. if 30% is adenine, then 30% would be thymine, since they are base-paired together. This means that 40% consists of G-C base pairs, which would be equally divided between the two bases.

Question 20

What would be the sequence of the strand of DNA that is made from the following template: 5’-GATATCGAT-3’ ?
How would the sequence be different if RNA were made from this DNA template?

Answer 20

The DNA sequence would be 5’-ATCGATATC–3’. The RNA sequence would be the same but instead each T would be a U.

Question 21

According to the RNA world model, a ribozyme would replicate by creating a stranded RNA intermediate. Would you expect the intermediate to have the same activity as the original ribozyme?

Answer 21

No. Catalytic activity in ribozymes depends on the tertiary structure generated form folding single-stranded molecules. Fully double-stranded forms of the RNA would not form the same tertiary structure

Question 22

What are three ways monosaccharides differ from one another?

Answer 22

Monosaccharides can differ from one another in the location of their carbonyl group, the number of carbon atoms they contain, and the orientations of their hydroxyl groups.

Question 23

What type of bond is formed between two sugars in a disaccharide?

Answer 23

glycosidic linkage

Question 24

What holds cellulose molecules together in bundles large enough to form fibers?

Answer 24

hydrogen bonds

Question 25

What are the primary functions of carbohydrates in cells?

Answer 25

cell identity, energy storage, raw material source for synthesis, and structure

Question 26

Which of the difference listed here could be found among molecules of the same monosaccharide?

Answer 26

T, there is a difference in the orientation of a hydroxyl group in the ring form
F
F
T, there is a difference in the overall shape of the molecule, one is a ring the other is linear

The second and third responses are false because the changes would result in different monosaccharides

Question 27

Although cellulose and starch are identical in terms of stored chemical energy, our ability to harvest the energy from these two polysaccharides differs. Why?

Answer 27

The α-1,4-glycosidic linkages in starch form independent helical structures that are easily hydrolyzed by enzymes found in most organisms. In contrast, the α-1,4-glycosidic linkages result in large fibers and sheets that exclude water, so they resist hydrolysis.

Question 28

Predict the effect of Lysozyme on bacteria and how it may be involved in human health?

Answer 28

When bacteria contact lysozyme, the peptidoglycan in their cell walls begins to degrade, leading to the death of the bacteria. Lysozyme therefore helps protect humans against bacterial infections

Question 29

If you hold a salty cracker in your mouth long enough, it will begin to taste sweet. Why?

Answer 29

Amylase breaks down the starch in the cracker into glucose monomers that taste sweet

Question 30

How do the phospholipids in archaea differ from those in other cells?

Answer 30

They have isoprenoid tails instead of fatty acids tails

Question 31

If a solution surrounding a cell is hypertonic relative to the inside of the cell, how will water move?

Answer 31

It will move out of the cell via osmosis

Question 32

What 2 conditions must be present for osmosis to occur?

Answer 32

For osmosis to occur, a concentration gradient and a membrane that allows water to pass, but not the solute, must be present.

Question 33

integral membrane proteins are anchored in lipid layers. Which of the following groups of amino acid residues would likely be found in the portion that crosses the lipid bilayer?

Answer 33

nonpolar

Question 34

Cooking oil lipids of long, unsaturated hydrocarbon chains. Would you expect these molecules to form membranes spontaneously? Why?

Answer 34

No, because they have no polar end to interact with water. Instead, these lipids would float on the surface of water, or collect in droplets suspended in water, reducing their interaction with water to a minimum

Question 35

In terms of structure, how do channel proteins differ from carrier proteins?

Answer 35

Channel proteins form pores in the membrane, some of which undergo conformational changes to shuttle molecules or ions across the membrane

Question 36

Suppose a cell is placed in a solution with a high concentration of potassium and no sodium. How would the cellular sodium-potassium pump function in this environment?

Answer 36

It would continue using ATP to pump sodium out of the cell and potassium into the cell