USMLE Biochemistry Flashcards

Study Notes

Essential Amino Acids

Essential amino acids cannot be synthesized by the body and must be obtained through diet.

Ketogenic Amino Acids

Lysine and Leucine are the only ketogenic amino acids, contributing to the production of ketone bodies.

Acidic Amino Acids

Aspartic acid and Glutamic acid are the two amino acids with "acid" in their names.

Basic Amino Acids

Histidine, Lysine, and Arginine are categorized as basic amino acids due to their side chains.

Glucogenic Amino Acids

Glucogenic amino acids can be converted into glucose through gluconeogenesis.

Phenylalanine Pathway

Phenylalanine is crucial for the synthesis of tyrosine and further derivatives.

Tryptophan Pathway

Tryptophan is a precursor for serotonin and melatonin, essential for mood regulation and sleep.

Hartnup Disorder & Vitamin B3 Deficiency

Hartnup disorder results in decreased tryptophan reabsorption, leading to niacin deficiency, necessary for NAD+/NADP+ production.

Histidine Metabolism

Histidine is converted to histamine with the help of vitamin B6 (pyridoxine).

Glycine Metabolism

Glycine is converted to porphyrin and heme, utilizing vitamin B6 as a cofactor.

Glutamate Metabolism

Glutamate is converted into GABA (gamma-aminobutyric acid), a neurotransmitter, in a B6-dependent reaction.

Arginine Metabolism

Arginine can produce nitric oxide (NO), creatine, and urea, with nitric oxide synthesis requiring tetrahydrobiopterin (BH4).

Maple Syrup Urine Disease

This condition arises from branched-chain α-ketoacid dehydrogenase deficiency, impairing the breakdown of isoleucine, leucine, and valine, resulting in syrup-smelling urine, intellectual disability, and poor nutrient intake.

HMP Shunt Goal

The primary goal of the HMP shunt is to produce NADPH, crucial for biosynthetic reactions.

Functions of NADPH

NADPH is essential for glutathione reduction, fatty acid synthesis, and cholesterol synthesis.

HMP Shunt Enzyme and Location

The enzyme glucose-6-phosphate dehydrogenase (G6PD) facilitates the HMP shunt, primarily occurring in the cytoplasm of the liver, mammary glands, and adrenal cortex.

Mnemonic for HMP Shunt Location

Remember HMP as Hepatic, Mammary, and Periphery of Adrenal.

Glutathione Reductase Pathway Goal

The goal is to reduce oxidized glutathione back to its active form.

Reduction of Glutathione

NADPH and glutathione reductase are necessary for reducing glutathione.

Oxidative Stress Causes

Factors causing oxidative stress can be remembered with the acronym SPIN-F.

G6PD Deficiency Memory Tool

Specific mnemonics can be developed to remember details about G6PD deficiency.

Fructose Metabolism

Fruits, juice, and honey are primary sources of fructose, which enters metabolic pathways.

Fructose Kinase Deficiency

A rare condition characterized by a lack of fructose kinase which affects fructose metabolism.

Hereditary Fructose Deficiency

Also known as aldolase B deficiency, it hampers fructose metabolism leading to severe reactions.

Consequence of Fructose Intolerance

Fructose-1-phosphate accumulation causes ATP depletion, resulting in hypoglycemic episodes.

Mnemonic for Fructose Intolerance

"Here, you are Fruct Int-irely by that Aldolase B" serves as a reminder of the condition.

Galactokinase Deficiency

Characterized by reduced enzyme activity leading to galactosemia, galactosuria, and increased galactitol.

Mnemonic for Galactokinase Deficiency

"GALAC-tokinase Deficiency" relates to key findings: galactosemia, cataracts, and abnormal eye tracking.

Classic Galactosemia

Caused by a deficiency in galactose-1-phosphate uridyltransferase; often leads to serious health issues.

Mnemonic for Classic Galactosemia Symptoms

"CLASSIC" refers to common complications such as sepsis and developmental issues.

Treatment for Galactosemia

A strict diet avoiding lactose and galactose is vital for management.

Lactose Intolerance

The condition is associated with normal intestinal mucosa despite symptoms of discomfort.

Alkaptonuria

Caused by a deficiency in homogentisate oxidase, leading to the accumulation of homogentisic acid and dark pigment in urine.

Enzymes in Albinism

Tyrosine hydroxylase and other enzymes are affected in albinism, leading to a lack of pigmentation.

Catecholamine Synthesis Pathway Mnemonic

A mnemonic can aid in recalling the steps in catecholamine synthesis.

Phenylketonuria (PKU) Causes

Caused by deficiencies in phenylalanine hydroxylase or tetrahydrobiopterin (BH4).

PKU Symptoms Mnemonic

"MOLD-E" reminds of symptoms: musty odor, low height, dermatitis, and epilepsy.

PKU Treatment

Involves increasing dietary tyrosine and decreasing phenylalanine intake; aspartame should be avoided.

Glycolysis Location

Glycolysis occurs in the cytoplasm, converting glucose into pyruvate.

Glycolysis Products

The process yields 2 pyruvate, 2 ATP, and 2 NADH molecules.

Glucokinase vs. Hexokinase

Hexokinase has a basic role in glucose metabolism while glucokinase acts as a glucose sensor in the liver and pancreatic cells.

Description

Test your knowledge on essential and various amino acids with these USMLE Biochemistry flashcards. Understand the classifications such as essential, ketogenic, acidic, basic, and glucogenic amino acids, as well as specific metabolic pathways. Perfect for medical students preparing for the exam.

USMLE Biochemistry Flashcards

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Questions and Answers

What are essential amino acids?

Which amino acids are considered ketogenic?

What are the acidic amino acids?

Name the basic amino acids.

What is the primary goal of the HMP Shunt?

What reduces glutathione?

Hartnup disorder leads to decreased ______ reabsorption.

What are the effects of Hereditary Fructose Deficiency?

Match the following conditions with their deficiencies:

Alkaptonuria is caused by a deficiency in Tyrosine Hydroxylase.

What is the treatment for Galactosemia?

What enzyme is deficient in Phenylketonuria?