GI Biochemistry Part II Flashcards
1
Q
Argininine
A
Semi-essential (can be synthesized from glucose and N pool ]e.g. urea cycle] but not in sufficient quantities) Glucogenic (α-ketoglutarate via glutamate)
2
Q
Histidine
A
Essential Glucogenic (α-ketoglutarate via glutamate)
3
Q
Isoleucine
A
Essential Glucogenic (succinyl-CoA) and ketogenic (acetyl CoA)
4
Q
Leucine
A
Essential Ketogenic (acetoacetate)
5
Q
Lysine
A
Essential Ketogenic (acetoacetate)
6
Q
Methionine
A
Essential Precursor for cysteine Glucogenic (succinyl-CoA)
7
Q
Phenylalanine
A
Essential Precursor for tyrosine Glucogenic (fumarate) and ketogenic (acetoacetate)
8
Q
Threonine
A
Essential Glucogenic (succinyl-CoA, pyruvate)
9
Q
Tryptophan
A
Essential Glucogenic (pyruvate) and ketogenic (acetoacetate)
10
Q
Valine
A
Essential Glucogenic (succinyl-CoA)
11
Q
Alanine
A
Nonessential Glucogenic (pyruvate)
12
Q
Asparagine
A
Nonessential Glucogenic (oxaloacetate via aspartate)
13
Q
Aspartate
A
Nonessential Glucogenic (oxaloacetate)
14
Q
Cysteine
A
Nonessential with sufficient methionine Glucogenic (pyruvate)
15
Q
Glutamate
A
Nonessential Glucogenic (α-ketoglutarate)
16
Q
Glutamine
A
Nonessential Glucogenic (α-ketoglutarate via gluamate)
17
Q
Glycine
A
Nonessential Glucogenic (pyruvate)
18
Q
Hydroxyproline
A
Nonessential for post-translational processing of collagen
19
Q
Hydroxylysine
A
Nonessential for post-translational processing of collagen
20
Q
Proline
A
Nonessential Glucogenic (α-ketoglutarate via gluamate)
21
Q
Serine
A
Nonessential Glucogenic (pyruvate)
22
Q
Tyrosine
A
Nonessential with sufficient phenylalanine Glucogenic (fumarate) and ketogenic (acetoacetate)
23
Q
Which amino acid doesn’t undergo transamination?
A
Lysine
24
Q
What are the important cofactors for transaminations?
A
Pyridoxal phosphate (PLP)/vitamin B6 (pyridoxine)
25
Vitamin B6 deficiency
Caused by poor diet or drug interaction (isoniazid for TB) Decreased synthesis of neurotransmitters, NAD, heme --\> neurologic and pellagra-like symptoms and anemia (sideroblastic)
26
What are the sources of the two nitrogens in urea?
NH4+ (from alanine or glutamine) and aspartate
27
How does the body get rid of excess nitrogen?
Urea (90%), NH4+, creatinine, uric acid (from purine catabolism)
28
What causes build-up or orotic acid and what are the symptoms?
Inborn error of ornithine transcarbamoylase or pyrimidine synthesis pathway dysfunction (OPRT, OMPDC) Congenitally, causes lethargy, hypothermia, and respiratory alkalosis 24-48 hours after birth and later vomiting, encephalopathy, cerebral edema Causes megaloblastic anemia that isn't cured with folate or vitamin B12 supplementation
29
What are the symptoms of ornithine transcarbamoylase deficiency?
Low BUN, blood arginine Undetectable blood citrulline Elevate blood ammonia, glutamine, orotic acid
30
How would you treat dysfunctions in the urea cycle?
Low protein diet (minimize waste nitrogen) and drugs (benzoate, phenylacetate) that eliminate waste nitrogen (conjugates and excretes glycine and glutamine)
31
Name transaminase pairs
α-ketoglutarate/glutarate alanine/pyruvate aspartate/oxaloacetate
32
What is Acute Intermittent Porphyria?
Autosomal dominant mutation of PBG deaminase Increase in urinary ALA and PBG Acute, recurrent attacks of severe abdominal pain, tachycardia, agitation, and psychiatric symptoms
33
What is Porphyria Cutanea Tarda?
Autosomal dominant decrease in uroporphyrinogen decarboxylase Increased urinary uroporphyrin III Chronic blistering lesions on sun-exposed areas of skin
34
What is Congenital Erythropoietic Porphyria?
Autosomal recessive mutation in URO III cosynthase (in bone marrow) that results in severe photomutilation and hypertrichosis (abnormal amount of hair growth)
35
What is the rate-limiting reaction of heme synthesis in bone marrow?
Ferrochelatase reaction
36
Describe the synthesis of nonessential amino acids?
Aspartate + Glutamine --\> Asparagine Oxaloacetate --\> Aspartate Serine --\> Glycine Phosphoglycerate --\> Serine Serine + Methionine --\> Cysteine Pyruvate --\> Alanine Phenyalanine --\> Tyrosine Glutamate Glutamine
37
What is phenylketonuria?
Autosomal recessive defect in phenylalanine hydroxylase Results in build-up of phenylalanine and low tyrosine --\> vomiting, hyperactivity, purposeless movement, athetosis, musty odor, mental retardation Treat by restricting phenylalanine in the diet
38
Which amino acid are branch-chained?
Valine, leucine, and isoleucine
39
What is Maple Syrup Urine Disease?
Autosomal recessive mutation in branched chain α-ketoacid dehydrogenase (oxidative decarboxylation) Urine smells like maple syrup Enzyme subunit E1 requires thiamine (vitmain B1); complex also requires vitamins B3 (NAD+) and B2 (riboflavin)
40
What is tyrosinemia?
Autosomal recessive error of tyrosine metabolism (fumarylacetoacetate hydrolase) Liver (cirrhosis, HCC) and kidney (Fanconi syndrome) distubances, mental retardation Treat with a low protein diet
41
What is Lesch-Nyhan Syndrome?
X-linked deficiency of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) Results in build-up of uric acid, gout, mental retardation, hypotonia, self-mutilating behavior Causes poor utilization of vitamin B12 --\> megaloblastic anemia
42
What is albinism?
Autosomal recessive defect in tyrosinase that results in lack of production of melanin (albino vs. albinoid) Lots of eye problems
43
What is α-1 antitrypsin deficiency
Autosomal recessive disorder with low or no α-1 antitrypsin which inhibits neutrophil elastase Causes liver disease in children and panacinar emphysema in adults MM, MZ, ZZ genotypes
44
What is Gaucher disease?
Autosomal recessive deficiency of glucocerebrosidase that results in a build-up of sphingolipids in lysosomes Symptoms include hepatosplenomegaly and pancytopenia
45
What is cystic fibrosis?
Autosomal recessive mutation in CFTR gene CFTR protein has iron conductance defect which lead to thickened fluid secretions 2/3 of cases have a deletion of phenylalanine in position 508 which causes the protein to misfold and increases degradation in the cell Diagnose with sweat test (will have more NaCl) Complications include lung diseases, nasal polyps, pancreatic insufficiency and malabsorption, liver disease
46
How do branched chain amino acids produce energy?
Isoleucine and leucine can produce acetyl CoA Isoleucine and valine can produce succinyl CoA
47
How is hyperammonemia produce neurotoxicity?
1) Excess NH3 inhibits glutaminase resulting in less glutamate to produce neurotransmitters 2) Glutamine enters mitochondria and hydrolysed to glutamate and NH3; NH3 increases pore permeability ad production of ROS 3) NH3 increases cell permeability to Ca2+ Symptoms include seizures, somnolence, apnea, coma, cerebral edema
48
What happens to insulin and glucagon after a high carbohydrate meal?
Insulin increases Glucagon decreases
49
What happens to insulin and glucagon after a high protein meal (with no or low carbs)?
Insulin increases --\> increased protein synthesis in muscle Glucagon increases --\> gluconeogenesis in liver
50
What do glucocorticoids (e.g. cortisol) do?
1) Stimulates lipolysis in adipose tissue 2) Stimulates muscle protein break-down 3) Stimulates gluconeogensis and glycogen breakdown 4) Makes tissues more sensitive to catecholamines
51
What are the seven amphibolic intermediates of amino acids?
Pyruvate, acetyl CoA, acetoacetate, α-ketoglutarate, succinyl CoA, fumarate, oxaloacetate
52
What are the ketogenic amino acids (e.g. carbons converted to acetyl CoA or acetoacetate)?
Leucine, isoleucine, lysine, phenylalanine, tryptophan, tyrosine
53
What is gout?
A disease characterized by hyperuricemia Uric acid causes sodium urate crystal deposition in joints Treat with NSAIDs and colchicine (acute) and allopurinol (chronic)
54
What are the origins of the atoms on the purine ring?
CO2, aspartate, glutamine, glycine, and 2 N10-FH4
55
What is Severe Combined Immunodeficiency Disease (SCID)?
Deficiency in adenosine deaminase that results in defective B and T cells
56
What are the origins of the atoms on the pyrimidine ring?
Glutamine, CO2, aspartate
