Biology I Chapter 3

What are the 4 sub-classes of lipids?

Fats, phospholipids, steroids and waxes

Name two polysaccharides that function inenergy storage. Name one carbohydrate that functions as a strong structural material. How is the structure of energy storage carbohydrates and structural carbohydrates related to function (i.e., what structure do energy storage carbohydrates have and why, and what structure do structural carbohydrates have and why)?

Glucose is broken down to release energy. Glycogen and starch are used to store glucose and they are formed from many glucose monomers joined together. Glycogen and starch have branched chains with many ends from which glucose monomers can be released when energy is needed. The more branches, the more glucose can be released at any time. If there were only 2 ends as in a straight chain then glucose could not be released as quickly. Glycogen (in animals) is more branched than starch (in plants) because animals typically have greater energy demands than plants. Cellulose serves a structural role. It has long, straight chains. The chains can pack together tightly to form a strong, rigid structure.

What is the genome? Do different cells of the same organism have the same genome or different genomes? What is the proteome? Do different cells of the same organism have the same proteome or different proteomes?

The genome refers to allthe DNA in a cell ororganism. All cells of amulticellularorganism have the same genome because they all contain the same DNA. The proteome refers to allthe proteins made by a cell or organism. Different cell types (i.e.,skin cell, muscle cell, etc.) within a multicellular organism have different proteomes. All cells have the same genome (i.e., DNA), but different cell types switch on different combinations of genes (sections of DNA) to make different combinations of proteins.

Below is an amino acid. The central carbon is connected to 4 groups. Which groups are the same in all amino acids? Which groups make each amino acid unique? (refer to image)

The hydrogen group, amino group and carboxylic acid group are the same in all amino acids. The side group is different in each amino acid and makes each amino acid unique.

Nucleotides are linked together to form polymers called nucleic acids. What type of bond (indicated with an arrow in the figure in Q17) links nucleotides together? What are the two classes of nucleic acid and what is their function?

-Two nucleotides are linked together by a phosphodiester bond. -The 2 classes of nucleicacid are DNA and RNA. -DNA stores the genetic information. -There areseveral different types of RNA that have different functions, but generally they are involved in the process of getting from DNA to polypeptide. (Some RNA molecules that we will discuss in future classes are mRNA, rRNA and tRNA. mRNA is copied from DNA and carries the information to link together amino acids to form a protein. rRNA and tRNA are involved in translating the sequence of nucleotides in mRNA to a sequence of amino acids in protein).

Most lipids are very nonpolar, but phospholipids are amphipathicdue to the presence of the polar head group. What structure do phospholipids form in water?

A bilayer structure(we will see in chapter 5 that the phospholipid bilayer forms the cell membrane that surrounds all cells).

There are 3 classes of carbohydrate, classed according to their size and structure. For molecules A-C below, is it a monosaccharide, disaccharide, or polysaccharide? Give an example of each type of molecule. (refer to image)

A.It is a monosaccharide. An example of a monosaccharide is glucose. B.It is a polysaccharide. Examples of a polysaccharides are glycogen, starch and cellulose. C.It is a disaccharide. An example of a disaccharide is sucrose (table sugar), which is composed of a monomer of glucose and a monomer of fructose.

Many amino acids are joined together to form polymers called .................., such as the one below. What type of bond, indicated by the arrows, links the amino acids? What group is at the N terminus? What group is at the C terminus? What level of protein structure is illustrated below? (refer to image)

Amino acids are linked by peptide bonds.The amino group is at the N terminus.The carboxyl group is at the C terminus. The primary structure is illustrated below.

What are the 4 major classesor organic molecules in living organisms?

Carbohydrates, lipids, proteins and nucleic acids.

Which atom forms the backbone of organic macromolecules?

Carbon

Give an example of a steroid.

Cholesterol, estrogen and testosterone were the steroids mentioned in class.

In a dehydration reaction, are 2 molecules joined together or broken apart, and what type of molecule is released in the process? In a hydrolysis reaction are 2 molecules joined or broken apart, and what molecule is added in the process?

In a dehydration reaction 2 molecules are joined together with the loss of a water molecule. In a hydrolysis reaction, a large molecule is broken into 2 smaller molecules with the addition of a water molecule.

What type of chemical bond is indicated by the letter X in figure C above? What type of reaction formed this bond? (i.e., a hydrolysis or a dehydration reaction)? (refer to image)

It is a glycosydic bond, and it was formed by a dehydration reaction(i.e.,a molecule of water was lost)

What chemical properties are shared by lipids (i.e., are they polar or non-polar)?

Lipids are generally nonpolar and therefore hydrophobic and insoluble in water (withthe exception of phospholipids, which are amphipathic and form the bilayer in water).

Molecules A and B below are fats. Are they saturated fats or unsaturated fats? Would a fat containing a high proportion of molecule A be solid or liquid at room temperature? Explain your answer. Would a fat containing a high proportion of molecule B be solid or liquid at room temperature? Explain your answer. (refer to image)

Molecule A is an unsaturated fat, and it would be a liquid at room temperature because it is unsaturated; the kink in the fatty acid chain means that thechainspack together less tightly andtherefore have weaker intermolecular interactions(van der Waals forces)anda lower melting temperature. Molecule B is a saturated fat, and it would be a solid at room temperature because it is saturated. The straight fatty acid chains pack together tightly,and therefore have strong intermolecular interactions (primarily van der Waals interactions) and ahigh melting temperature.

What is an organic molecule?

Molecules that are found in living organisms that contain carbon bonded to hydrogen.

Which molecules in the list below are monomers (building blocks) that can be joined to form larger polymers? Which molecules in the list below are polymers? Match the correct monomers with the correct polymers, e.g., ____ are linked to form _____. A. Amino acids F. Glycerol + 3 fatty acids B.Nucleic acids G. Polysaccharides C.Fats. H. Polypeptides D. Nucleotides. I. Phospholipids E.Monosaccharides J. Glycerol + 2 fatty acids + phosphate group

Monomers: amino acids, monosaccharides, nucleotides, glycerol+3 fatty acids, glycerol+3 fatty acids+phosphate group Polymers: Nucleic acids, phospholipids, polypeptides(form proteins), fats, polysaccharides Amino acidsare linkedto form polypeptides(which fold to form proteins). Monosaccharides are linked to form polysaccharides. Nucleotides are linked to form nucleic acids Glycerol is linked to 3 fatty acids to form a fat Glycerol is linked to 2 fatty acids and a phosphate group to forma phospholipid

What type of macromolecule is shown below? (refer to image)

Nucleic acid (formed from the linking together of many nucleotides).

How would molecule B above have to be modified to make a phospholipid? (refer to image)

One of the fatty acid chains would have to be replaced by a phosphate group.

Polypeptides fold to form functional proteins. Briefly describe (one or two sentences) each level of protein structure shown below. Primary structure has been done for you as an example: Primary structure: linear sequence of amino acids that make up the polypeptide (refer to image)

Primary structure: Sequence of amino acids. Secondary structure: Folding withinlocal regions of the polypeptide chain. Common secondary structures are the alpha helix and beta sheet. Tertiary structure: Overall 3D folded shape of a polypeptide. This is the final level of structure for a protein composed of a single polypeptide. Quaternary structure: The association of two or more polypeptides to form a multi-subunit protein.

What type of lipid is shown below? It will be formed by bonding together molecule X with 3 of molecule Y. What is the name of molecules X and Y? What type of bond, indicated by the arrow, will join molecules X and Y? (refer to image)

The lipid is a fat (specifically, a saturated fat). Molecule X is glycerol and molecules Y are fatty acids. Each fatty acid is bonded to glycerol through an ester bond.

Figure A below shows a phospholipid. Phospholipids are amphipathic. What part of the phospholipid is hydrophilic and what part is hydrophobic? (refer to image)

The phosphate group (which may be bonded to another charged molecule) forms the hydrophilic part of the phospholipid because it has a charge, and the fatty acid tails form the hydrophobic part of the molecule because they are very nonpolar. Don't worry about glycerol, I have sometimes seen it said that it belongs to the hydrophilic portion and sometimes seen it said that it belongs to the hydrophobic portion.

Below is a nucleotide. Name the parts of the nucleotide labeled X-Z(i.e., phosphate, sugar or base). Is this nucleotide a DNA or an RNA nucleotide? (refer to image)

X-phosphate group Y -sugar group (deoxyribose sugar) Z -base The nucleotide is a DNA nucleotide because it contains a deoxyribose sugar. An RNA nucleotide would contain a ribose sugar.