Section 3 Reading Guide

Question 1

What is a dehydration synthesis reaction?

Answer 1

The hydrogen of one monomer combines with a hydroxyl group of another monomer, which then releases a water molecule.
Forms bonds, requires energy

Question 2

What are hydrolysis reactions?

Answer 2

water is mostly used to break down the chemical bonds that exists between a particular substance
breaks bonds, releases energy

Question 3

1) what is a monosaccharide?
2) What is its function?
3) what functional groups are in it?
4) polar or nonpolar?
5) examples in living organisms?

Answer 3

1) 1 sugar
2) energy for cells
3) carbonyl group and hydroxyl group
4) polar
5) glucose: source of energy in humans

Question 4

1) what is a disaccharide?
2) What is its function?
3) what functional groups are in it?
4) polar or nonpolar?
5) examples in living organisms?

Answer 4

1) 2 sugars
2) breaks down simpler sugars
3) two monosaccharides connected by a glycosidic bond
4) polar
5) sucrose (table sugar): provides energy

Question 5

1) what is a polysaccharide?
2) What is its function?
3) what functional groups are in it?
4) polar or nonpolar?
5) examples in living organisms?

Answer 5

1) many sugars
2) structural support
3) hydroxyl group
4) polar
5) cellulose: makes up the cell wall in plants

Question 6

How is a disaccharide formed from monosaccharides? How is a polysaccharide formed from monosaccharides?

Answer 6

Two monosaccharides are joined together through a glycosidic bond in a disaccharide. Many monosaccharides are joined together through a glycosidic bond in a polysaccharide.

Question 7

Describe the biological functions of starch, glycogen, and cellulose

Answer 7

Starch: energy storage molecule in plants
Glycogen: energy storage molecule in animals
Cellulose: makes up the cell wall of plants

Question 8

What is a lipid? Describe the characteristics that all lipids share.

Answer 8

Lipids are hydrocarbons that are nonpolar and hydrophobic. They are used for energy storage in the form of fats. They also provide insulation from the environment for plants and animals.

Question 9

Why are fatty acids amphipathic?

Answer 9

Fatty acids are amphipathic because they are hydrophilic as well as hydrophobic. They have a head that is hydrophilic and interacts with water, and the tail is a chain of nonpolar hydrocarbons that are hydrophobic and will not interact with water.

Question 10

What is the difference between a saturated fatty acid (or fat) and an unsaturated fatty acid (or fat)? What do these terms tell you about whether a fat is liquid or solid at room temperature?

Answer 10

Saturated fatty acids only have single bonds between carbons and hydrogens. They are solid at room temperature. Unsaturated fatty acids have a double bond, bending the hydrocarbon chain. They are liquid at room temperature.

Question 11

How does a phospholipid differ structurally and functionally from a fat? In what part of a cell are phospholipids abundant?

Answer 11

Phospholipids are on the outermost layer of cell membranes. Instead of three fatty acids attached, there are two, and a modified phosphate group occupies the glycerol backbone’s third carbon. Phospholipids are abundant in the plasma membrane.

Question 12

What are steroids? Steroids have very different structures from fats and phospholipids, so why are they classified as lipids?

Answer 12

Steroids have four linked carbon rings and occur naturally in plants and animals. They are classified as lipids because they are found in the phospholipid bilayer.

Question 13

1) What molecular components or building blocks are in fat?
2) amphipathic?
3) role(s) the lipid plays in an organism

Answer 13

1) glycerol and fatty acids
2) yes
3) provides insulation

Question 14

1) What molecular components or building blocks are in phospholipids?
2) amphipathic?
3) role(s) the lipid plays in an organism

Answer 14

1) glycerol molecule, two fatty acid chains, phosphate group
2) yes
3) forms structural foundation of cell membranes

Question 15

1) What molecular components or building blocks are in steroids?
2) amphipathic?
3) role(s) the lipid plays in an organism

Answer 15

1) four fused carbon rings
2) yes
3) reproduction and growth

Question 16

What is the difference between a polypeptide and a protein? What is an enzyme?

Answer 16

A polypeptide is a linear chain of amino acids linked together, a protein has a more complex structure with one or more polypeptide chains folded into a three-dimensional shape. An enzyme is a catalyst in biochemical reactions. They break down substrates, build complex molecules, and affect the rate of reaction.

Question 17

Which group varies to give 20 different amino acids?

Answer 17

R group

Question 18

What are the ways that structural characteristics of amino acids can influence their properties?

Answer 18

If an amino acid is nonpolar, it will not interact with water. If an amino acid is polar, it will interact with water.

Question 19

What is a peptide bond? What does it link together and what reaction is used to form it?

Answer 19

A peptide bond is a covalent bond that attaches to an amino acid through a dehydration synthesis reaction. The carboxyl group on one amino acid will link together with an amino group on the second amino acid. Because it is a dehydration synthesis reaction, the linkage will get rid of a water molecule. The carboxyl group will lose one oxygen atom, and the amino group will lose two hydrogen atoms.

Question 20

1) What is the description of the primary structure of proteins?
2) structural features
3) What kinds of bonds hold it together?

Answer 20

1) sequence of amino acids
2) linear sequence of amino acids
3) disulfide bonds

Question 21

1) What is the description of the secondary structure of proteins?
2) structural features
3) What kinds of bonds hold it together?

Answer 21

1) folding of the polypeptide
2) Alpha helix: spiral shaped structure in proteins made up of amino acids
Beta sheet: multiple polypeptide chains connected by hydrogen bonds between backbones
3) hydrogen bonds

Question 22

1) What is the description of the tertiary structure of proteins?
2) structural features
3) What kinds of bonds hold it together?

Answer 22

1) three-dimensional structure of the polypeptide
2) Disulfide bridge: covalent bond between sulfur atoms of two cysteine amino acids
3) hydrogen bonds

Question 23

1) What is the description of the quaternary structure of proteins?
2) structural features
3) What kinds of bonds hold it together?

Answer 23

1) Many molecules that bind together to form a structure
2) arrangement of many polypeptide chains held together by hydrogen bonds, ionic bonds
3) hydrogen bonds, disulfide bonds ionic bonds, London dispersion forces, van der Waals forces

Question 24

Explain why 2˚, 3˚ 4˚ structure all depend on a polypeptide’s 1˚ structure.

Answer 24

The sequence of amino acids determines the types of interactions that can occur between amino acid side chains

Question 25

What happens to a protein’s structure and function when it denatures? What conditions might lead to denaturation of a protein? Which levels of structure are affected in denaturation?

Answer 25

It can lose its shape and the structure changes. High temperatures and high acidities are both able to denature proteins. The secondary and tertiary structures are affected, but the primary structure remains intact.

Question 26

What is a nucleic acid? What are the functions of DNA and RNA?

Answer 26

A nucleic acid is a polymer made up of nucleotides. DNA is the genetic material that makes up all living organisms, and it controls cellular activities. RNA is involved in protein synthesis.

Question 27

What three components make up a nucleotide?

Answer 27

a nitrogenous base, phosphate group, 5-carbon sugar

Question 28

What are the differences between the nitrogenous bases pyrimidines and purines? List the names and one-letter abbreviations for each type.

Answer 28

Purines have two carbon-nitrogen rings and are made up of adenine and guanine (A, G). Pyrimidines have a single carbon-nitrogen ring and consist of cytosine, thyine, and uracil (C, T, U).

Question 29

What are the differences between ribose and deoxyribose sugars?

Answer 29

The pentose sugar in DNA is deoxyribose, and the sugar in RNA is ribose. The difference is the presence of the hydroxyl group in the ribose’s second carbon and hydrogen in the deoxyribose’s second carbon.

Question 30

What is the sugar-phosphate backbone?

Answer 30

Sugar and phosphate lie on the outside of the helix, forming the backbone of the DNA. Nitrogenous bases are stacked inside and are bound by hydrogen bonding.

Question 31

Describe the structure of a DNA molecule, using the terms double helix and antiparallel.

Answer 31

All base pairs within the double helix are separated from each other. The strands run in opposite directions and are therefore antiparallel. The 5’ is pointing down on one strand, and the 3’ carbon is pointing down on the other. These strands run in opposite directions.
How does the sequence of nucleotides in DNA influence the amino acid sequence of a protein?
The sequence of nucleotides acts as code to specify every amino acid. mRNA is transcribed and read by ribosomes to put together amino acids.