How many carbons in prostaglandins?

In cholesterol?

20C - prostaglandins

27C - cholesterol

What is the dietary precursor to prostaglandin synthesis?

linoleic acid

 arachidonic acid

What are the 2 isoforms of cyclo-oxygenase? Which produce prostaglandins?

COX-1, COX-2

both produce prostaglandins

Which COX isoform is not increased by cytokines such as IL-1?

COX-1

- constituitive

- used in cell signaling

- not influenced by steroid administration

PGI2 opposes the action of what closely related eicosanoid through the prevention of blood clots?

thromboxane

Which COX enzymes do Aspirin and Tylenol inhibit, respectively?

Aspirin - COX-1 and COX-2

Tylenol - COX-3

(COX-3 an alternatively spliced form of COX-1)

What is the substrate for COX-1 and COX-2?

arachidonic acid

- oxidative cyclization of arachidonic acid by COX enzymes yields PGH2

What side effect of NSAIDS were COX-2 inhibitors designed to avoid?

upset stomach, ulcers, GI problems

(prostaglandins normally inhibit GI acid secretion)

ACC

(Acetyl CoA Carboxylase)

- catalyzes the formation of Malonyl CoA from Acetyl CoA

-occurs in cytosol

Substrate - Acetyl CoA

Enzyme - ACC (+ citrate for activation)

Energy Requirements - 1 ATP

Coenzyme - Biotin

CO2 for carboxylation of Acetyl CoA

In the presence of ____ ACC is phosphorylated, and thereby _______.

In the presence of ______ ACC is dephosphorylated, and thereby ______.

In the presence of Epinephrine ACC is phosphorylated, and thereby inactivated.

In the presence of Insulin ACC is dephosphorylated, and thereby activated.

- so high insulin stimulated fa synthesis!

malonyl CoA (product of regulated step)

palmitoyl CoA (16:0) (end-product)

What is the primary source of acetyl CoA used in fatty acid synthesis?

of NADPH?

acetyl CoA from the pyruvate formed in glycolysis

NADPH from hexose monophosphate shunt

-also comes from conversion of malate to pyruvate in cytosol

What are two important features that distinguish prostaglandins from hormones?

What is the commited step of purine de novo biosynthesis?

How is it regulated?

the synthesis of 5'-phosphoribosylamine from PRPP and glutamine

(via glutamine:phosphoribsyl pyrophosphate amidotransferase)

this step is inhibited by end-products AMP, GMP, and IMP

True or False:

AMP is the precursor for IMP and GMP.

False -  IMP is the precursor for AMP and GMP.

- If both AMP and GMP are present in adequate amounts, the de novo pathway of purine synthesis is turned off at the amidotransferase.

- Synthesis of AMP requires GTP, whereas synthesis of GMP requires ATP

Which of the following amino acids is not used in purine de novo biosynthesis?

A. glutamine

B. cysteine

C. glycine

D. Aspartate

Which are also required for pyrimidine synthesis?

B. Cysteine

- Glycine contributes 2Cs and 1N to purine ring

- Asparatate contributes 1N

- Glutamine contributes 2N

- Glutamine and aspartate used in pyr. synthesis

Mycophenolic Acid is a reversible inhibitor of what step in GMP formation?

How is it used pharmacologically?

Reversibly inhibits the conversion of IMP to Xanthosine monophosphate by

IMP dehydrogenase

- used to prevent graft rejection by depriving  proliferating T and B cells of nucleic acid components

What is the N source in the conversion of hypoxanthine to Adenine?

What is the N source in the conversion of xanthine to Guanine?

Hypoxanthine + Aspartate --> Adenine

Xanthine + Glutamine --> Guanine

inosine - hypoxanthine

guanosine - guanine

adenosine - adenine

- purine bases lack the (deoxy)ribose sugar and Phosphates of nucleotides

- nucleosides lack the phosphates

- Adenine is converted to AMP by Adenine phosphoribosyltransferase (APRT)

- Guanine is converted to GMP by Hypoxanthine-guanine phosphoribosyltransferase (HGPRT)

- both use PRPP as the source of the ribose 5-phosphate group

Negative regulation of PRPP synthetase (1st step in purine de novo synthesis)

and PRPP amidotransferase (2nd commited step)

- results in overproduction of PRPP --> purines

--> urate = buildup of uric acid crystals in joints and hyperuricemia

- Allopurinol inhibits Xanthine oxidase - the enzyme that converts hypoxanthine into xanthine and also xanthine into uric acid.

- Accumulation of upstream products xanthine and hypoxanthine is ok b/c they are more soluble than uric acid.

ADA  (Adenosine deaminase)

- normally converts Adenosine to Inosine

- deficiency leads to buildup of dATP, an inhibitor of ribonucleotide reductase, and therefore of DNA synthesis

- disfunctional T and B cells

Lesch-Nyhan syndrome

- In addition to hyperuricemia, symptoms include self-mutilation and mental retardation

What step in pyrimidine synthesis is catalyzed by CPS II?

Where in the cell does it take place?

The synthesis of carbamoyl phosphate from glutamine and CO2. Occurs in cytosol.

- first step

- committed step

- inhibited by UTP

- activated by ATP and PRPP

What are the 3 classes of RNA polymerases?

What does each synthesize?

Which one is especially sensitive to a-amanitin?

RNA polymerase I - rRNAs

RNA polymerase II - mRNAs

RNA polymerase III - tRNAs (& other small RNAs)

RNA polymerase II is extremely sensitive to inhibition by a-amanitin

Introns are excised and exons are ligated in the processing of eukaryotic mRNA.

(Intervening introns)

(Expressed exons)

Which is not associated with eukaryotic mRNA?

A. 3' poly A tail

B. ligation of exons

C. 5'-7-methyl guanosine "cap"

D. polycistronic

D. polycistronic

- describes the feature of prokaryotic mRNA that allows a single strand to code for multiple proteins

What type of RNA makes up the highest percentage of total cellular RNA?

The lowest?

rRNA (ribosomal) is the highest at 80%

U1-U6 (small RNAs) are the smallest at <1%

Which DNA polymerase elongates the RNA primer on the lagging strand?

Which DNA polymerase excises the RNA primers?

DNA polymerase III :

- 5' --> 3' polymerase activity for synthesizing DNA, thereby elongating RNA primer

- 3'-->5' exonuclease activity "proofreads" DNA

DNA polymerase I:

- 5' --> 3" exonuclease activity that removes RNA primer and fills the gap (FEN-1 in eukaryotes)

 Multiple origins of replication is characteristic of

A. Eukaryotic DNA replication

B. Prokaryotic DNA replication

C. neither

D. both

A. Eukaryotic DNA replication

List the functions of the following Eukaryotic DNA polymerases:

a

b

g

d

e

a - repair and replication and primase function

b - repair

g - mitochondiral DNA polymerase

d - replication with PCNA (sliding clamp or processivity factor)

e - replication

glutamate

aspartate

glycine

a-ketoglutarate --> Glutamate

oxaloacetate --> Aspartate

The first step in the catabolism of all amino acids involves the removal of the _____.

a-amino group

carbamoyl phosphate

-combined with HCO3- by CPS1 in the mitochondria of the liver

Which enzyme of the urea cycle is the regulatory enzyme?

What is its required allosteric activator?

CPS-1

- catalyzes the first step

- fixes NH4+ as carbamoyl phosphate

- requires N-acetylglutamate

What are the 5 enzymes of the urea cycle, in order?

Which are found in the mitochondria?

mitochondria:

CPS-1

Ornithine transcarbamylase

cytosol:

Arginosuccinate synthase

Arginosuccinate lyase

Arginase

Hyperammonemia affects what part of the body the most?

Is caused by a buildup of what?

What diseases can cause hyperammonemia?

- CNS most severely affected

- caused by buildup of glutamine

- associated with liver failure, HI/HA syndrome (gain of function mutation in GLUD-1), and mutations in any of 5 urea cycle enzymes

GDH

Glutamate Dehydrogenase

-gain of function leads to overproduction of ammonia (& insulin)

What reaction does Glutamate Dehydrogenase catalyze?

glutamate --> NH3 + alpha-ketoglutarate

- glutamate the only aa to undergo oxidative deamination by GDH--> releases free NH3

- can use either NAD+ or NADP+ as coenzyme

How many carbons in cholesterol?

progesterone?

testosterone?

estradiol?

Cholesterol- C27

progesterone - C21

testosterone - C19

estradiol - C18

17 hydroxylase

Which corticosteroid has an aldehyde at C18?

Aldosterone

-acts on kidney to promote Na+ retention and

K+ loss

Which is not a characteristic of steroid hormones?

A. act within hours

B. derived from cholesterol (~300mw)

C. affect cAMP levels

D. nuclear receptors

C. affect cAMP levels

-in general they do not

- Peptide hormones do!

NGF (neurotrophic growth factor) is a "classic" example of what type of hormone signaling?

a dimer made up of two monomers that each have 7 different enzymatic activities plus an acyl carrier protein (ACP) domain.

glycerol 3-phospate

--> yields a phosphatidic acid

diacylglycerol with a phosphate group on the 3rd Carbon

-forms the base for phosphatidyl compounds

Where does triacylglycerol (triglyceride) synthesis mainly take place?

Phospholipid synthesis?

Triglyceride - mainly synthesized in liver

phospholipid - synthesized in all cells except mature RBCs

Paper contains glucose oxidase enzyme.

Glucose + O2 àglucose oxidase à gluconic acid + H202

H202 + ortho-toluidine àperoxidaseà oxidized orthotoluidine (color)

Specific for beta D glucose