Biochemistry week 14

Question 1

What are nucleotides essential for + WHY

Answer 1

-DNA + RNA synthesis: Without nucleotides DNA or RNA cant be produced
-Protein synthesis: No nucleic acids= no proteins
-Cell proliferation - Nucleotides are necessary for cell division and growth

Question 2

Name the components of a nucleotide

Answer 2

• Phosphate group
  -Pentose sugar
  -Nitrogenous base

Question 3

Name the purines

Answer 3

• Adenine Guanine

Question 4

Name the pyrimidines

Answer 4

Cytosine and thymine

Question 5

What is the name of :
-1 phosphate grp
-2 phosphate grp
-3 phosphate gro

Answer 5

1. Monophosphate
   2.Diphosphate
   3.Triphosphate

Question 6

What do 2nd and 3rd phosphates form

Answer 6

High enery bonds

Question 7

What does a nucleoside contain

Answer 7

• Base + sugar

Question 8

What bond does nucleosides contain

Answer 8

N-glycosidic bond

Question 9

Give examples of nucleosides

Answer 9

-Adenosine
-Guanosine

Question 10

Give 4 examples of nucleotides

Answer 10

• AMP
  -ADP
  -ATP
  GMP

Question 11

Give purines in DNA + RNA

Answer 11

A,G- DNA
A,G- RNA

Question 12

Give the pyrimidines in DNA + RNA

Answer 12

• C, T- DNA
  -C,U- RNA

Question 13

What are the 5 functions of Nucleotides:

Answer 13

• DNA + RNA synthesis
  -Serve as energy carriers, actiated intermediates
  -Components of coenzymes
  -Second messengers

Question 14

Name the components of coenzymes that Nucleotides may serve as

Answer 14

• CoA
  -FAD
  -NAD
  NADPH

Question 15

Name the seconf messengers nucleotides may srve as

Answer 15

• cAMP
  -cGMP

Question 16

Where does purine nucleotide synthesis occur

Answer 16

It occurs mainly in the liver

Question 17

How is the purine ring built

Answer 17

Built step by step onto ribose-5-phosphate

Question 18

Where does the ribose-5-phosphate starting purine synthesis come from

Answer 18

Pentose phosphate pathway

Question 19

What is the final product of purine synthesis

Answer 19

• Inosine Monophosphate- IMP, which is percursors for both AMP and GMP

Question 20

In the purine ring explain where the :
-N1 atom is derived from
-C2&C8-
-N3&N9
-C4,C5,N7
-C6

Answer 20

N1 – Aspartate

C2 & C8 – Formate (from tetrahydrofolate)

N3 & N9 – Glutamine

C4, C5, N7 – Glycine

C6 – CO₂

Question 21

Explain purine synthesis

Answer 21

-Ribose-5-phosphate converted to PRPP via PRPP synthetase

-PRPP is then coverted into 5-Phosphoribosylamine ( Commited step ) via enzyme glutamine: phosphoribosylpyrophosphate(GPAT)
-5-Phosphoribosylamine converted into IMP ( parent compund for AMP + GMP

Question 22

What is the committed and higly regulates step in purine synthesis

Answer 22

• Conversion of PRPP + glutamine into 5-phosphoribosylamin
  -via enzyme Glutamine: PRPP amidotransferase(GPAT)

Question 23

What is the purine base of IMP

Answer 23

Hypoxanthine

Question 24

What does AMP and GMP stand for

Answer 24

AMP- Adenosine monophosphate
GMP-Guanosine monophosphate

Question 25

Explain what AMP + GMP inhibits -Explain what happens if both AMP + GMP are sufficient

Answer 25

- AMP- inhibits AMP synthesis -GMP inhibits GMP synthesis -If both are sufficient, synthesis is inhibited at the GPAT step

Question 26

What are nucleotide diphosphates( ADP + GDP) made from + using what + what phosphate donor

Answer 26

Monophosphates - AMP and GMP using : -base specific nucleoside monophosphate kinases -ATP is phopshate donor

Question 27

Where does deoxyribonucleotide synthesis occur

Answer 27

It occurs at the diphosphate level

Question 28

Explain how deoxyribonucleotides are formed via what enzyme+ what as a cofactor

Answer 28

- Ribonucleoides are converted into deoxyribonucleotides -Via enzyme ribonucleotide reductase -Requires thioredoxin as a cofactor

Question 29

What happens in salvage pathways: -The reuse of what? -What is cinverted

Answer 29

- Reuse of free purine bases, nucleosides and nucleotides -Purine bases into nucleotides

Question 30

What pathway is a important energy saving pathway

Answer 30

Slavage pathways

Question 31

Give 3 examples of purine bases

Answer 31

- Hypoxanthine -Guanine adenine

Question 32

What is the purpose of the purine salvage pathway

Answer 32

- Recycles free purine bases from: -Turnover of cellular nucleic acids -Dietary purines

Question 33

How does the purine salvage pathway conserve energy -What are salvaged puriens converted into

Answer 33

-By reusing purine bases - Converted into nucleoside triphosphates

Question 34

In the purine salvage pathway what is : -Adenine converted to , via what enzyme -What is hypoxanthine converted into via what enzyme -What is Adenosine phosphorylated to via what enzyme

Answer 34

- Adenine converted to AMP via APRT -Hypoxanthine converted to IMP and guanaine then to GMP via HGPRT -Adenosine phosphorylated into AMP via adenosine kinases

Question 35

What is Lesch -Nyhan syndrome + caused by

Answer 35

A severe X linked recessive disorder caused by almost complete deficiency of HGPRT

Question 36

What are the biochemical consequences of Lesch- nYHAN- Syndrome

Answer 36

↓ IMP & GMP levels → ↓ feedback inhibition of GPAT ↑ PRPP availability ↑ De novo purine synthesis → ↑ purine degradation ↑ Uric acid production → hyperuricemia

Question 37

Give clinical symptoms of Lesch-Nyhan syndrome

Answer 37

- Uric acid kidneys tones -Gouty arthritis -Motor dysfunction

Question 38

What is the purpose of purine nucleotide degredation

Answer 38

-To Break down purine nucleotides into utric acid

Question 39

Where are dietary nucleic acids degraded

Answer 39

In small intestine

Question 40

Where are endogenous (cellular) purines degraded

Answer 40

lIVER

Question 41

What are free purine bases degraded to or exported to for what

Answer 41

- Degraded to Utric acid or exported to peripheral tissues for salvage

Question 42

What is the name of elevate uric acid

Answer 42

- Hyperuricemia

Question 43

What can hyperuricemia(elevated uric aicd) lead to

Answer 43

- Gout -Uric acid kidney stonex

Question 44

What is Gout+ what it results from

Answer 44

Disorder caused by high levels of uric acid in the blood -Overproduction of uric acid -Underexcretion of uric acid

Question 45

Give clinical features of Gout

Answer 45

uric acid Kidney stones -Monosodium urate (MSU) crystal deposit in joints -Tophi

Question 46

What are the causes of hyperuricemia

Answer 46

-Underecretion of uric acid -Overproduction of uric acid

Question 47

What are the primary and secondary causes of underexcretion of uric acid

Answer 47

Primary-Inherited defect in renal excretion mechanism Secondary- Lactic acidosis

Question 48

What is the primary cases of overproduction of uric acid

Answer 48

- Idiopathic

Question 49

What increases the risl of Gout

Answer 49

- Red meat, organ meat -Seafood -Alchohol

Question 50

How can Acute Goat be treated

Answer 50

- NSAIDs -Colchicine -Corticosteroids