Biochemistry

Question 1

What cell CANNOT utilize ketones as an energy source? Why?

Answer 1

RBCs because they lack mitochondria to convert it into acetyl CoA

Question 2

Fabry’s disease

What is it? how is it inherited What are characteristics?

Answer 2

lysosomal storage disease

X-linked recessive deficeincy in alpha-galactosidase

accumulation of globotriaosylceramide

kidney disease, angiokeratoma, cardiac disease, peripheral neuropathy

Question 3

what enzyme is defective in Lesch-Nyhan? If this enzyme is defective, what enzyme activity is increased?

Answer 3

Hypoxanthine-Guanine Phosphoribosyltransferase (defective)

phosphoribosyl pyrophosphate aminotransferase (increased purine de novo synthesis)

Question 4

What is a silent mutation? What are its consequences?

Answer 4

change in nucleotide (often wobble base aka 3rd) but amino acid stays the same

Question 5

What is a missense mutation? what are its consequences?

Answer 5

nucleotide substitution resulting in a changed amino acid

e.g. sickle cell (glutamic acid –> valine)

Question 6

What is a nonsense mutation? What are its consequences?

Answer 6

nucleotide substitution resulting in an early stop codon

Usually results in a nonfunctional protein

Question 7

What is a frameshift mutation? what are its consequences?

Answer 7

deletion OR insertion of a number of nucleotides NOT divisible by 3

Protein may be shorter OR longer and its function may be disrupted or altered

Question 8

What type of connections allow osteocytes to communicate?

Answer 8

gap juncitons

Question 9

What is the most common cause for down syndrome? (default in what process)

Answer 9

meiotic nondisjucntion

Question 10

Through what mechanism does ionizing radiation kill cells?

Answer 10

1) double stranded DNA breaks
2) free radical formation

Question 11

What is the inheritance of CF?

Answer 11

autosomal recessive

Question 12

What is the most common mutation in CF? What does this mutation do?

Answer 12

3-base pair deletion at phenylalanine at amino acid position 508 (delta-F508)

causes misfolding of the CFTR channel which results in proteasomal degradation, preventing it from reaching the cell surface

Question 13

What are the steps of elestin sythesis

Answer 13

mRNA – tropoelastin –> microfibrillar scaffold –> desmosine cross-links via lysyl oxidase

Question 14

True or False: The lagging strand in DNA synthesis is unique because it must synthesize mutliple, short DNA fragments

Answer 14

true

Question 15

What is the mnemonic for the familial dyslipidemias?

Answer 15

1 LP, 2 LD, 3 with E, 4 gets more

Question 16

What is deficient in type I familial dyslipidemia? What is elevated? what are the clinical findings?

Answer 16

LPL

TGs (chylomicrons)

can present with: acute pancreatitis, eruptive xanthomas, creamy layer in supernatant

Question 17

What is deficient in type II familial dyslipidemia? What is elevated? what are the clinical findings?

Answer 17

LDL receptor

cholesterol (LDL)

tendon xanthoma (achilles)

Question 18

What is deficient in type III familial dyslipidemia? What is elevated? what are the clinical findings?

Answer 18

apoE

chylomicron and VLDL remnants (products after LDL and VLDLs get hydrolized via LPL)

palmar xanthomas

Question 19

What is deficient in type IV familial dyslipidemia? What is elevated? what are the clinical findings?

Answer 19

ApoA-V

VLDL

increased risk for pancreatitis

Question 20

What is the role of DNA polymerase III?

Answer 20

5’ to 3’ DNA synthesis and 3’ to 5’ exonuclease activity (this means it also proofreads the growing DNA strand and can fix an error should it occur)

Question 21

What is the role of DNA polymerase I?

Answer 21

5’ to 3’ DNA synthesis and 3’ to 5’ exonuclease activity

degrades RNA primer and replaces it with DNA

Question 22

What is the role of ligase?

Answer 22

joining of okazaki fragments in the lagging strand

Question 23

What is the function of primase?

Answer 23

synthesis of an RNA primer

Question 24

What is the MELAS syndrome of mitochondrial myopathies? What does muscle biopsy show?

Answer 24

MELAS = mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes

biospy shows ragged red fibers (due to accumulation of diseased mitochondria)