Biochem Flashcards
When are microsatellite repeats generated in the cell cycle?
S phase
During catabolism of proteins, amino acids are transferred to ______ to form glutamate.
α-ketoglutarate
If a patient’s sibling has an autosomal recessive disease and the patient is not affected (neither are the parents), what is the chance that the patient is a carrier?
2/3
If a mother and father have a 1/40 and 1/300 chance of being a carrier for a recessive disease, respectively, what is the chance the child will have the disease?
(1/40 x 1/2) x (1/300 x 1/2) = 1/48,000
What components are needed for PCR?
- DNA template (must be pretty short, ≤ 10 kb)
- Two primers (25-35 bases) complementary to regions flanking template
- DNA polymerase
- Deoxynucleotide triphosphates
What is the Kozak consensus sequence?
a sequence near the AUG codon in eurkaryotes that plays a role in initiation - note that a purine (A or G) residue three bases upstream is particularly important
What are the cause and symptoms of Beriberi?
cause: thiamine deficiency Infantile (2-3 mo.): cardiac syndrome with cardiomegaly, tachycardia, cyanosis, dyspnea, and vomiting Adult: - wet: neuropathy + cardiac involvement - dry: symmetrical peripheral neuropathy
What is the genetic error that causes most cases of down syndrome?
maternal meiotic nondisjunction
What non-essential AA becomes essential in homocysteinuria?
cysteine
What is another name for Lynch syndrome? Mode of inheritance? Defect?
hereditary nonpolyposis colon cancer; AD inheritance; 90% of cases have mutations in MSH2 and MLH1 → no MutS or MutL human homologs → defective mismatch repair
How is classical galactosemia inherited? How about Lesch-Nyhan and Hemophilia B?
autosomal recessive; x-linked recessive
What is the HMP shunt (pentose phosphate pathway) useful for?
- provides NADPH from abundant G-6-P, which is needed for reductive reactions:
a. glutathione reduction inside RBCs
b. FA and cholesterol biosynthesis - also yields ribose for NT synth and glycolytic intermediates
Describe the breakdown of branched glycogen to an unbranched chain of G-1-P residues
- G-1-P’s are removed until there are 4 residues left on the main chain and branch (by glycogen phosphorylase)
- 3 G-1-P’s are taken from the branch to the main chain (by debranching enzyme 1 aka 4-α-D-glucanotransferase)
- the last G-1-P is cleaved from the branch (by debranching enzyme 2 aka α-1,6,-glucosidase)
Describe the synthesis of glycogen from G-6-P
- converted to G-1-P by UDP-glucose pyrophosphorylase
- linked together to form a glycogen chain by glycogen synthase
- branches are created by branching enzyme
What enzyme is deficient in Von Gierke disease (type I)? What is its function? What are the consequences?
glucose-6-phophatase deficiency; converts G-6-P to glucose (this only happens in the liver); → severe fasting hypoglycemia, ↑↑ glycogen in the liver, hepatomegaly, and ↑ blood lactate (because ↑ glycolysis)
What is the mode of inheritance of Von Gierke disease? How is it treated?
AR; frequent oral glucose/cornstarch; avoid fructose and galactose
What enzyme deficiency leads to Pompe disease (type II)? What is its function? Consequences of dysfunction?
Lysosomal α-1,4-glucosidase (acid maltase; aka acid α-glucosidase); breaks down a small amount of glycogen within lysosomes; leads to glycogen accumulation within lysosomes, hepatomegaly, cardiomegaly, macroglossia, and if severe, mental retardation
How are all glycogen storage diseases inherited?
autosomal recessive
What enzyme is deficient in Cori diseae (type III; aka Forbes disease)? What is its function? What are the consequences?
Debranching enzyme (α-1,6-glucosidase); removes the last G-1-P from a branch;→ hypoglycemia, hepatomegaly, hyperlipidemia, growth retardation, muscle weakness
What enzyme is deficient in McArdle disease? What is its function? What are the consequences?
skeletal muscle glycogen phosphorylase (myophosphorylase); cleaves G-1-P residues from glycogen until limit dextran is formed; → ↑ glycogen in mm. which can’t be broken down → painful mm. cramps, myoglobinuria with strenuous exercise, arrhythmia (from electrolyte abnormalities)
What is carnitine important for? What happens when you have a carnitine deficiency?
transport of long chain fatty acids into the mitochondria for degradation; deficiency → toxic accumulation → weakness, hypotonia, and hypoketotic hypoglycemia
What are the TATA box and CAAT boxes?
sequences in the promoter region of genes where RNA pol II and TFs bind to initiate transcription
What is an important allosteric activator of gluconeogenesis that acts by ↑ pyruvate carboxylase (converts pyruvate to oxaloacetate)?
acetyl-CoA
What is the 16S rRNA sequence?
It is a component of the the 30S ribosomal subunit in prokaryotes that contains a sequence complementary to the Shine-Dalgarno sequence on mRNA; binding b/w these sites is necessary for initiation of translation
What is c-Jun?
a transcription factor that can become an oncogene w/ a mutation/ overexpression
Which enzyme is most commonly deficient in β-oxidation?
Acyl-CoA dehydrogenase (catalyzes the first step)
What two substrates are normally involved in transamination reactions? What vitamin is needed?
amino acid and α-keto acid (e.g. oxaloacetate)
What are P bodies?
cytoplasmic foci that contain proteins important in mRNA translation regulation and mRNA degradation
