Podcast Deep Dive #1

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Podcast – Deep Dive - #1

Amino Acids

Essential Amino Acids

PVT – phenylalanine, valine, threonine

TIM – Tryptophan, isoleucine, methionine (start codon)

HaLL – Histidine, Leucine, Lysine

These AA need to be taken up in the diet by intestinal absorption and proximal tubule.

Hartnup disease – Inability to absorb neutral aminoacids in the brush border of intestines and in proximal collecting duct. Symptoms are mainly due to lack of tryptophan which depletes niacin and gives pellagra like symptoms. Auto recessive.

Branched chain – Leucine, isoleucine, valine

MSUD – auto recessive defect in catabolism of branched chain amino acids. Specific deficiency of branched chain ketoacid dehydrogenase complex. Causes encephalopathy and developmental problems. Tx with glucose, branched chain free protein, liver transplant. Leucine causes brain problems, isoleucine is responsible for the smell. More common in the Mennonites.

Conditional – Arginine, cysteine, glycine, glutamate, proline, tyrosine

(essential only when in severe starvation states – ie normaly tyrosine can be converted from phenylalanine – if none in diet such as pku then youll have a deficiency)

PKU – Auto – recessive lack of phenylalanine hydroxylase. Cant oxidize to tyrosine to make catecholamine, pigments. Transaminiated in to toxic product one of which is a ketone. (transamination requires B6). Need phenylalanine free foods and drink or they develop seizures, hypoglycemia (early) -> mousy/musty order, learning disabilities, microcephaly.

Transamination – Process by which an amino acid takes a amino group and transfers it to a-ketoglutarate. The AA changes and AKG changes to glutamate.

For that reason PKU patients need B6 supplemented as well.

Dispensible – Alanine, aspartic acid, glutamic acid, serine

(Can pretty much always make these)

Acidic – (negative) glutamic acid, aspartic acid

Basic – (positive) – histidine, arginine, lysine

Sickle cell disease – in disease states valine instead of a glutamic acid at position 6http://imgur.com/gallery/rX5FGVI. Glutamic acid sticks to water. Hydrophobic valine likes to stick to itself and other hydrophobic things. That promotes sickling and causes the vasocclusive crises.

Protein Energy Malnutrition

½ of deaths less than 5 years old some sort of PEM in developing countries

Marasmus – decrease in overall calorie balance. Symptoms are due to a childs adaptation to the low energy stores. Kiddos will have decreased physical activity, slow growth, and weight loss. Fat stores are low and water stores increase. This throw off drug metabolism and distribution. Arm measurements are used to evaluate the extent of malnutrition. As starvation increases gluconeogenesis will eventually stop to preserve muscle tissue and ketones from fatty acid metabolism becomes the primary fuel of the brain. Pre-albumin can be used as a sensitive indicator of overall nutritional status. Refeeding can be associated with life-threatening hypoglycemia – feed with small frequent meals. May have hypokalemia.

Kwashiorkor – sufficient calories but low protein intake. Often at risk in individuals weened off breast milk going to a diet high in carbs. Features of the disease include pitting edema which may be due to a decrease in glycosaminoglycans. Also have characteristic fatty swollen livers. They also have immune deficiencies because they cant make antibodies and have reduced responses to vaccines.

On the USMLE patients with any of the malnutrition symptoms will likely be an immigrant, anorexic, or demented elderly with “tea and toast” diet


AMINO ACIDS MNEMONIC: The most stupid way to remember the amino acids classification ever made. My Notes for USMLE. Available at: http://mynotes4usmle.tumblr.com/post/55745595622/amino-acids-mnemonic-the-most-stupid-way-to#.VjqMHPlViko. Accessed November 4, 2015.

Hartnup Disease. : Practice Essentials, Background, Pathophysiology. Available at: http://emedicine.medscape.com/article/1115549-overview. Accessed November 4, 2015.

Le, T, Krause, K, Eby, E. First aid for the basic sciences. New York: McGraw-Hill Medical; 2009.

Maple Syrup Urine Disease. : Background, Pathophysiology, Epidemiology. Available at: http://emedicine.medscape.com/article/946234-overview. Accessed November 4, 2015.

Phenylketonuria. : Practice Essentials, Background, Pathophysiology. Available at: http://emedicine.medscape.com/article/947781-overview. Accessed November 4, 2015.

Protein-Energy Malnutrition. : Background, Pathophysiology, Epidemiology. Available at: http://emedicine.medscape.com/article/1104623-overview. Accessed November 4, 2015.

Sickle Cell Anemia. SciVee. doi:10.4016/14996.03.
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