Chapter 7

Question 1

Nucleic Acids

Answer 1

Large molecules composed of a chain of smaller nucleotide molecules

Question 2

Nucleotide

Answer 2

Composed of one phosphate group (PO3), one 5-carbon, ringed sugar, and one of five nitrogenous base molecules

Question 3

RNA

Answer 3

• Ribose Sugar
• Adenine, Uracil, Cytosine, and Guanine base molecules
• 100-50000 nucleotides in nucleic acid strand
• single stranded; linear
• variety of functions related to protein synthesis

Question 4

DNA

Answer 4

• Deoxyribose sugar
• Adenine, Thymine, Cytosine, and Guanine base molecules
• Chromosomes have about 45 million nucleotides in nucleic acid strand
• Double stranded helix; bases bonded by weak hydrogen bonds
• Stores genetic information (genes) that direct RNA to perform protein synthesis

Question 5

Complementary Base Pairs

Answer 5

Certain bases will form weak hydrogen bonds between them; no exchange of electrons; allow two long strands of DNA to stick together; the second strand is complementary to the first

Question 6

Central Dogma

Answer 6

DNA replication
Protein Synthesis
- DNA –transcription–> mRNA –translation–> protein

Question 7

DNA Replication

Answer 7

A process that allows two identical copies of DNA for the bacterial chromosome occurring prior to cell division:

• Helicase unwinds and “unzips” the double stranded helix at the origin of replication (begins process)
• Bacteria have one origin of replication; eukaryotic cells have many (several thousand)
• Unwinds and unzips in both directions (5’ to 3’)
• Complementary base pairing of new nucleotides to the original strands (adenine — thymine; cytosine – guanine)

Question 8

Chromosome

Answer 8

Short, thick strand of DNA and protein; regulate cellular activity by controlling which genes are expressed to produce proteins

Question 9

DNA Polymerase

Answer 9

• Proof reads the new complementary nucleotide base pairs
• Joins the new complementary base pairs together
• This proceeds until two identical strands are made; strands will eventually separate
• 500-1000 base pairs in a second
• E. coli has 4,639,221 base pairs

Question 10

Lead Strand

Answer 10

DNA replication occurs towards the replication fork; nucleotides are added continuously in the 3’ direction

Question 11

Lagging Strand

Answer 11

DNA replication occurs away from the replicating fork; nucleotides are added in segments in the 5’ direction (Okazaki fragments)

Question 12

Semiconservative Replication

Answer 12

Type of DNA replication in which half of the original strand of the DNA molecule is conserved in each new DNA molecule produced

Question 13

Organization of the Chromosome

Answer 13

Circular; made of DNA and protein; divided into genes, each of which is a sequence of DNA nucleotides; Bacterial cells will:

• code for the production of a single protein (coding region
• regulate the expression of genes (regulatory region)

Question 14

Promotor

Answer 14

An area where RNA polymerase will bind to a chromosome (always unzipped)

Question 15

Operator

Answer 15

A gene can be turned off by placing a protein here

Question 16

Triplets

Answer 16

How genes are divided; composed of a sequence of three nucleotides found within the same gene; if the gene codes for a protein, this will code for one specific amino acid found within the protein that will be produced; 64 possible combinations but only 20 different amino acids (more than one for each amino acid)

Question 17

Stop Triplets

Answer 17

Found at the end of the coding region, they stop the reading of a gene

Question 18

Protein Synthesis

Answer 18

The joining of amino acids to produce proteins; occurs in two distinct phases: transcription and translation

Question 19

Transcription

Answer 19

Steps used to convert a segment of DNA (template) into mRNA

Question 20

mRNA (messenger)

Answer 20

A sequence of codons that is a complementary copy of a single gene; carries the information from the DNA to the ribosome; must be present for translation to occur

Question 21

Phases of Transcription

Answer 21

• Initiation: The enzyme RNA polymerase attaches to the promotor region of a gene
• Elongation: The enzyme unzips the DNA molecule and moves along the template of DNA, synthesizing a single stranded mRNA strand one nucleotide at a time
• Termination: The enzyme encounters a “stop signal” and terminates the construction of mRNA
• A typical gene is composed of 1000 nucleotides and it takes about 30 seconds to make a copy

Question 22

Translation

Answer 22

The synthesis of an amino acid strand (protein) from codons found on mRNA

Question 23

Ribosome

Answer 23

Made of rRNA and protein; mRNA binds here; must be present for translation to occur

Question 24

tRNA (transfer)

Answer 24

Brings a specific amino acid to the mRNA and ribosome; must be present for translation to occur:

• three nucleotides (anti-codon) which is complementary to the codon found on the mRNA
• charged when a specific amino acid is attached to it
• uncharged, it will not have specific amino acid attached, but will eventually find and attach to become charged

Question 25

Phases of Translation

Answer 25

- Initiation: mRNA binds to the 30S portion of the ribosome - Elongation: A protein is constructed, one amino acid at a time - Termination: The ribosome reaches a "stop codon" which will terminate production of the protein, and the protein is released

Question 26

Stop Codons

Answer 26

Found at the end of a mRNA strand that signal the termination of protein synthesis; UAA, UAG, and UGA

Question 27

Erythromycin

Answer 27

An antibiotic that binds to the 50S subunit, inhibiting protein synthesis

Question 28

The Elongation Phase of Translation

Answer 28

- P site: first tRNA will bind here, it is complementary to the first mRNA codon - A site: second tRNA will bind here, it is complementary to the second mRNA codon - the two charged tRNA will release their amino acid which form peptide bonds between them, forming a short polypeptide - the mRNA shifts over one codon and the process continues one amino acid at a time, until a stop codon is reached

Question 29

Environmental Effects on Anabolic Chemical Reactions

Answer 29

Bacteria live in environments that are changing rapidly; their energy supply or supply of essential nutrients may "dry up"; they must be able to control their biochemical pathways in order to conserve energy (90% of energy used goes to protein synthesis) and spare materials

Question 30

How Bacteria Conserve Energy and Spare Materials

Answer 30

- Will utilize any and all molecules found within the environment instead of producing them themselves; genes that control the production of certain molecules will be turned off during periods of plenty: energy is conserved and can be used in cell division - When molecules dry up, the macromolecule must be produced by the machinery of the cell; genes must be able to turn on when needed: energy reserves are used up inside the cell and cell division occurs slowly

Question 31

End Product Repression

Answer 31

The end product of a series of chemical reactions will inhibit the expression of a gene and prevent further synthesis of all those enzymes necessary to produce the end product (turns genes on or off); e.g., production of the five enzymes responsible for the production of tryptophan

Question 32

Production of Tyrptophan

Answer 32

- Five genes (one of each enzyme) are located side by side and controlled by the same promotor and operator region (operons); if RNA polymerase attaches to the promotor and no inhibitor exists, then all five genes will be expressed - Another gene is responsible for the production of an inactive inhibitor protein; it will not bind to the operator region unless this end product is very abundant - If so, then it will bind to the inhibitor protein, changing its shape, and allowing it to bind to the operator region; the synthesis of all the enzymes are inhibited; once the enzymes within the cell are used up, synthesis of this product will cease

Question 33

Feedback Inhibition

Answer 33

The end product will inhibit the function of one enzyme (of a series of enzymes) responsible for the synthesis of the end product

Question 34

Non-Competitive Inhibition

Answer 34

An inhibitor molecule binds to the allosteric site of an enzyme and permanently changes the shape of the enzyme, preventing the substrate from binding to the enzyme

Question 35

Competitive Inhibition

Answer 35

An inhibitor molecule binds to the active site of an enzyme and prevents the substrate from binding to the enzyme