Amino ASSid Metabolism
This vitamin derivative serves as the essential cofactor required by all aminotransferase enzymes during transamination reactions
What is pyridoxal phosphate (PLP/Vitamin B6)?
Beta-oxidation of fatty acids takes place within this specific subcellular compartment
What is the mitochondrial matrix?
In skeletal muscle, a triad junction is composed of one transverse (T) tubule flanked on either side by these sarcoplasmic reticulum structures
What are terminal cisternae?
A nucleotide differs structurally from a nucleoside because it contains at least one of these attached to the ribose sugar
What is a phosphate group?
Slow-twitch (Type I) muscle fibers rely primarily on aerobic metabolism and fatty acid oxidation due to high densities of mitochondria and this oxygen-storing protein
What is myoglobin?
A fall on an outstretched hand (FOOSH) causing a distal radius fracture with posterior displacement of the distal fragment results in this characteristic physical deformity
What is a dinner fork deformity (Colles' fracture)?
Fracture at the fibular neck typically damages the common fibular (peroneal) nerve, resulting in loss of eversion, loss of dorsiflexion, and this characteristic gait pattern
What is a steppage gait (foot drop)?
Muscle-type nicotinic receptors (Nm) located on the motor endplate are ligand-gated ion channels that require the binding of this exact number of acetylcholine molecules to open
What is two?
During transamination, the transfer of an amino group to alpha-ketoglutarate generates this key amino acid
What is glutamate?
Lipolysis in adipose tissue is primarily stimulated by epinephrine through the activation of this enzyme
What is hormone sensitive lipase?
Binding of acetylcholine to nicotinic receptors on the junctional folds of the motor endplate triggers an influx of this cation to depolarize the membrane
What is sodium?
The first committed step of purine de novo biosynthesis is catalyzed by glutamine:PRPP amidotransferase, which is allosterically activated by PRPP and inhibited by these end products
What are AMP and GMP (purine nucleotides)?
Skeletal muscle internalizes blood glucose in response to insulin through the translocation of this specific glucose transporter to the plasma membrane
What is GLUT-4?
A patient with tenderness upon palpation of the anatomical snuffbox after a FOOSH injury most likely sustained a fracture of this carpal bone
What is the scaphoid bone?
An adolescent athlete presenting with severe anterior knee pain and point tenderness over a swollen, prominent tibial tuberosity is suffering from this self-limited growth plate condition
What is Osgood-Schlatter disease?
Succinylcholine is the prototype depolarizing neuromuscular blocker that produces muscle fasciculations followed by flaccid paralysis through this specific receptor mechanism
What is persistent depolarization?
Alanine aminotransferase (ALT) transfers an amino group from alanine to alpha-ketoglutarate, yielding glutamate and this 3-carbon metabolic intermediate
What is pyruvate?
Long-chain fatty acids require this specialized transport mechanism to cross the inner mitochondrial membrane into the matrix
What is the carnitine shuttle?
Depolarization along the T-tubule membrane senses a voltage change via the dihydropyridine receptor (DHPR), which physically pulls open this calcium release channel on the sarcoplasmic reticulum
What is the ryanodine receptor type 1 (RyR1)?
In mammalian cells, the key regulated enzyme of pyrimidine de novo synthesis is carbamoyl phosphate synthetase II (CPS II), which is inhibited by this pyrimidine nucleotide
What is UTP?
Unlike the liver and kidney, skeletal muscle cannot export free glucose into the bloodstream during a fast because it lacks this essential enzyme
What is glucose-6-phosphate?
A midshaft fracture of the humerus at the radial groove typically damages the radial nerve and profunda brachii artery, leading to this classic motor deficit
What is a wrist drop?
Rupture of the calcaneal (Achilles) tendon during sudden plantarflexion prevents the patient from performing this physical movement
What is standing on tiptoes (plantarflexion against resistance)?
Non-depolarizing neuromuscular blocking agents like rocuronium act at the motor endplate through this pharmacological mechanism of action
What is competitive antagonism at Nm receptors?
Aspartate aminotransferase (AST) converts glutamate and oxaloacetate into alpha-ketoglutarate and this specific amino acid
What is aspartate?
he rate-limiting enzyme of fatty acid transport into the mitochondria, Carnitine Palmitoyltransferase I (CPT-I), is negatively regulated by this molecule
What is malonyl-CoA?
Cytosolic calcium initiates skeletal muscle contraction by binding directly to this specific subunit of the troponin complex
What is troponin C (TnC)?
Methotrexate inhibits dihydrofolate reductase (DHFR), depriving cells of tetrahydrofolate (THF) and preventing the synthesis of this single-carbon donor required for purine ring assembly
What is N10-formyltetrahydrofolate (N10-formyl-THF)?
During intense muscle contraction, elevated intracellular levels of AMP allosterically activate glycogen phosphorylase b without requiring this chemical modification
What is phosphorylation?
An anterior dislocation of the shoulder joint flattens the deltoid contour and risks injury to this nerve, causing weakness in arm abduction beyond 15 degrees and sensory loss over the lateral shoulder
What is the axillary nerve?
A positive anterior drawer test of the knee indicates a tear of this stabilizing intra-articular ligament
What is the anterior cruciate ligament (ACL)?
Cisatracurium is the non-depolarizing neuromuscular blocker of choice in patients with liver or kidney failure because it undergoes inactivation via this spontaneous, non-enzymatic pathway
What is Hofmann elimination?
Tissues transport nitrogen to the liver primarily as glutamine rather than glutamate, which upon entry into hepatocytes is cleaved by this liver enzyme to release free ammonia and glutamate
What is glutaminase?
Each round of beta-oxidation shortens a fatty acyl CoA by two carbons and directly releases one molecule of acetyl CoA along with these two reduced electron carriers
What are NADH and FADH2?
Muscle relaxation relies primarily on this sarcoplasmic reticulum pump to actively transport calcium out of the cytoplasm and back into the SR
What is SERCA?
The primary purine salvage enzyme HGPRT catalyzes the transfer of a ribose 5-phosphate group from PRPP to hypoxanthine or guanine, generating pyrophosphate and these two purine monophosphates
What are IMP and GMP?
Unlike the liver isoenzyme, skeletal muscle PFK-2 is not inactivated by phosphorylation during a fast, allowing this metabolic pathway to remain active in muscle
What is glycolysis?
Compression of the median nerve beneath the flexor retinaculum results in numbness in the lateral 3.5 digits and weakness of these hand muscles
What are the thenar muscles?
Weakness of the gluteus medius and minimus muscles leads to a pelvic tilt toward the uninjured side when standing on the affected leg, a physical exam finding known by this name
What is a positive Trendelnburg sign (test)?
Neostigmine is routinely co-administered with glycopyrrolate during neuromuscular blockade reversal to prevent unwanted parasympathetic side effects caused by stimulation of these receptors
What are muscarinic ACh receptors?
hese two specific amino acids are strictly ketogenic because their carbon skeletons degrade directly into acetyl CoA or acetoacetate and cannot yield glucose
What are leucine and lysine?
The complete oxidation of one molecule of palmitate (16 carbons) yields a net total of 129 ATP after subtracting 2 ATP equivalents utilized during this initial activation reaction
What is fatty acid activation (acyl-CoA synthetase step)?
During cross-bridge cycling, the binding of a new molecule of ATP to the myosin head is required to trigger this crucial mechanical step
What is detachment of the myosin head from actin?
Sulfonamides act as structural analogs of para-aminobenzoic acid (PABA) to competitively inhibit folic acid synthesis in bacteria without affecting human cells
What are PABA analogs (sulfonamids/sulfa drugs)?
During anaerobic exercise, fast-twitch muscle generates lactate, which travels to the liver for gluconeogenesis to resupply glucose back to the muscle in this cyclical pathway
What is the Cori cycle?
Lesion of the anterior interosseous nerve (AIN), a pure motor branch of the median nerve in the forearm, prevents a patient from making this specific hand gesture
What is the OK sign?
Inadvertent intramuscular injection into the inferomedial quadrant of the gluteal region risks damaging this major nerve, causing paralysis of all muscles below the knee
What is the sciatic nerve?
Sugammadex rapidly reverses neuromuscular blockade induced by rocuronium or vecuronium through this selective mechanism
What is selective encapsulation (binding/trapping in cyclodextrin ring)?
In skeletal muscle during fasting, amino acid breakdown transfers nitrogen to pyruvate to form alanine, which travels to the liver for gluconeogenesis in this metabolic pathway
What is the glucose-alanine cycle (shuttle)?
During periods of fasting, the liver converts excess acetyl CoA produced by high rates of beta-oxidation into these alternative soluble energy substrates for peripheral tissues like muscle
What are ketone bodies (3-hydroxybutyrate, acetoacetate, acetone)?
During sarcomere shortening and muscle contraction, the length of the A band remains constant while these two regions shorten
What are the H zone and I band?
Lesch-Nyhan syndrome is an X-linked recessive disorder characterized by severe hyperuricemia, gout, and self-mutilation caused by a deficiency of this purine salvage enzyme
What is HGPRT?
During fasting or exercise, epinephrine increases lipoprotein lipase (LPL) activity in skeletal muscle while simultaneously decreasing LPL activity in this tissue
What is adipose tissue?
Injury to the long thoracic nerve leads to paralysis of the serratus anterior muscle and results in this visible anatomical deformity
What is medial scapular winging?
A 14-year-old basketball player with gradually worsening hip pain that radiates to the knee and limited internal rotation on X-ray shows displacement of the femoral head relative to the neck through the growth plate, diagnosing this condition
What is slipped capital femoral epiphysis (SCFE)?
During Train-of-Four (TOF) stimulation, non-depolarizing neuromuscular blockers display a progressive reduction in twitch height known by this characteristic pattern
What is fade (progressive fade pattern)?
This severe inborn error of metabolism is caused by a deficiency in branched-chain alpha-keto acid dehydrogenase, leading to the toxic accumulation of leucine, isoleucine, and valine metabolites
What is Maple Syrup Urine Disease (MSUD)?
The rate-limiting enzyme in hepatic ketone body synthesis is mitochondrial HMG-CoA synthase, whereas peripheral utilization of acetoacetate requires this specific enzyme absent in the liver
What is thiophorase?
The optimal sarcomere length for maximum active isometric tension generation occurs when thick and thin filament overlap allows maximum cross-bridge formation, corresponding to this length range
What is 2.0 to 2.2 micrometers?
In HGPRT deficiency, unutilized PRPP accumulates in cells, directly accelerating purine de novo synthesis and resulting in the massive overproduction and excretion of this degradation end product
What is urate (uric acid)?
In skeletal muscle during fasting, active AMPK phosphorylates and inactivates Acetyl-CoA Carboxylase-2 (ACC-2), causing a decrease in this CPT-I inhibitor and accelerating beta-oxidation
What is malonyl CoA?
A supracondylar fracture of the humerus risks injury to the brachial artery and this nerve, impairing flexion of the index and middle fingers when trying to make a fist
What is the median nerve?
Injury to the proximal tibial nerve in the popliteal fossa causes loss of toe flexion, loss of foot inversion, and sensory loss over this specific region of the foot
What is the sole of the foot?
Succinylcholine administration is strictly contraindicated in patients with extensive burns, major trauma, or denervation injuries due to the severe risk of triggering this life-threatening electrolyte abnormality
What is hyperkalemia?