Biochemistry Notes

Question 1

What is the specific makeup of nucleosome?

Answer 1

The nucleosome is composed of an octamer of histone proteins, designated as H2A, H2B, H3 and H4

Question 2

How many histone proteins make up nucleosome?

Answer 2

4

Question 3

What is the mnemonic for chromatin types?

Answer 3

Eu = true, “truly transcribed” HeteroChromatin = Highly Condensed

Question 4

What is the general mechanism of action of methylation in Prokaryotes?

Answer 4

Template strand cytosine and adenine are methylated in DNA replication, which allows mismatch repair enzymes to distinguish between old and new strands in prokaryotes.

Question 5

What does DNA methylation at CpG islands do?

Answer 5

DNA methylation at CpG islands prevent transcription

Question 6

Why is DNA condensed in chromatin form?

Answer 6

DNA is condensed in chromatin form to fit into the nucleus

Question 7

What makes up the nucleosome?

Answer 7

An octamer composed of four histone proteins

Question 8

What is the secondary structure of a nucleosome molecule?

Answer 8

A negatively-coiled DNA structure wrapped around a positively coiled octamer protein

Question 9

What is the common name for nucleosomes?

Answer 9

Beads on a string

Question 10

How is chromatin stabilized?

Answer 10

The H1 histone protein binds to linker DNA and to the nucleosome

Question 11

Histones are rich in what amino acids?

Answer 11

Lysine and Arginine

Question 12

During Mitosis, what is the form of DNA? How does it take this form?

Answer 12

DNA condenses during mitosis to form chromsomes

Question 13

When does DNA synthesis take place during the life cycle of a cell?

Answer 13

S phase

Question 14

When does Histone synthesis take place during the life cycle of a cell?

Answer 14

S phase

Question 15

What is the mechanism of action of histone acetylation?

Answer 15

Histone acetylation facilites transcription by relaxing the coiling of DNA molecules.

Question 16

How many ring structures in Purines?

Answer 16

2

Question 17

How many ring structures for pyrimidines?

Answer 17

1

Question 18

Purines can be utilized to produce what nitrogenous base?

Answer 18

Adenine and Guanine

Question 19

Pyrimidines can be utilized to produce what nitrogenous base?

Answer 19

Cytosine, Uracil and Thymine

Question 20

What is a mnemonic to remember purines?

Answer 20

PURe As Gold

Question 21

What is a mnemonic to remember pyrimidines?

Answer 21

CUT the PY(pie)

Question 22

What is a nemonic to remember the chemical group attached to thymine?

Answer 22

THYmine has a meTHYl

Question 23

What is the reactant, general chemical reaction for the production of uracil?

Answer 23

Deamination of cytosine creates uracil

Question 24

What is the difference between RNA and DNA when you consider the nitrogenous bases?

Answer 24

DNA has thymine and RNA has uracil

Question 25

What bond is stronger, G-C bond or A-T bond? Why?

Answer 25

G-C bond, 3 H-bonds is strong than A-T bond, 2 H-bonds

Question 26

How can you change the type of nitrogenous bases to increase the melting point of a DNA molecule?

Answer 26

Increase the number of G-C bonds

Question 27

What amino acids are needed for Purine synthesis?**(3 points)**

Answer 27

Glycine, Aspartate and Glutamine

Question 28

What is the nemonic used to remember the amino acids needed for purine synthesis?

Answer 28

Glycine Aspartate Glutamine or GAG

Question 29

What are the general chemical components of a nucleoside?

Answer 29

base + (deoxy)ribose (Sugar)

Question 30

What are the general chemical components of a nucleotide?

Answer 30

base + (deoxy)ribose + phosphaTe; lined by 3'-5' phosphodiester bind

Question 31

What is the first difference between purine and pyrimidine synthesis?

Answer 31

Orotic acid is a temporary base for pyrimindines

Question 32

What is the first step in purine synthesis?

Answer 32

Starts with sugar and phosphate

Question 33

What is the first step in pyrimindine synthesis?

Answer 33

Start with temporary base: orotic acid

Question 34

What is the second step of pyrimindine synthesis?

Answer 34

Add sugar and phosphate to Orotic acid

Question 35

What is the second step of purine synthesis?

Answer 35

Add base to sugar and phosphate

Question 36

What is the third general step of pyrimidine synthesis?

Answer 36

Modify the base

Question 37

What substances are created first with purine and pyrimidine synthesis?

Answer 37

Ribonucleotides are synthesized first

Question 38

During purine and pyrimidine synthesis, ribonucleotides are converted to what? What enzyme catalyzes this step?

Answer 38

Ribonucleotides are converted to deoxyribonucleotides by ribonucleotide reductase

Question 39

What substance is involved in de novo pyrimidine synthesis and the urea cycle?

Answer 39

Carbomyl phosphate

Question 40

What drug blocks dihydroorotate dehydrogenase?

Answer 40

Lefunomide

Question 41

What drug inhibits ribonucleotide reductase?

Answer 41

Hydroxyurea

Question 42

What drug inhibits dihydrofolate reductase in humans?

Answer 42

Methotrexate

Question 43

What drug inhibits dihydrofolate reductase in bacteria?

Answer 43

trimethoprim

Question 44

What drug inhibits dihydrofolate reductase in protozoa?

Answer 44

pyrimethamine

Question 45

What is the first step in the purine salvage pathway?

Answer 45

HGPRT + PRPP