Aerobic Metabolism in Skeletal Muscle

Vocabulary practice flashcards covering all numbered components, enzymes, substrates, and pathways in the skeletal muscle aerobic metabolism diagram and answer key.

Aerobic Metabolism Scheme

The comprehensive pathway schematic of skeletal muscle illustrating the integrated steps of Slow Glycolysis, $\beta\text{-oxidation}$, the TCA cycle, and the electron transport chain (ETC) across the plasma membrane, cytosol, and mitochondrial membranes.

Free fatty acid(s)

Circulating lipids in the blood (Label 1) that enter skeletal muscle through a membrane transporter protein to bind FABP in the cytosol.

GLUT

The glucose transporter protein (Label 2) in the skeletal muscle plasma membrane that transports extracellular blood glucose into the cytosol.

Stored glycogen

The cytosolic carbohydrate storage form (Label 3) that is cleaved by phosphorylase into G-1-P to enter Slow Glycolysis.

F-6-P

Fructose-6-phosphate (Label 4), a glycolytic intermediate generated from G-6-P and converted into F-1,6-bisP by phosphofructokinase.

Stored triglyceride

Intracellular lipid storage (Label 5) broken down in the cytosol by LIPASE to yield free fatty acids bound to FABP (FFA-FABP).

Glycerol phosphate SS

The glycerol phosphate shuttle system (Label 6) that transports reducing equivalents from cytosolic NADH across the outer and inner mitochondrial membranes into the matrix and electron transport chain.

Pyruvate

The three-carbon end product of Slow Glycolysis (Label 7) transported across the mitochondrial membranes to be converted into Acetyl CoA.

Myosin (cross bridge)

The thick filament contractile element (Label 8) that interacts with actin and utilizes ATP via mATPase to power muscle contraction.

Actin

The thin filament protein (Label 9) that binds with myosin cross bridges during skeletal muscle cross-bridge cycling.

Carnitine SS

The carnitine shuttle system (Label 10) spanning the mitochondrial outer membrane (OM) and inner membrane (IM) to transport fatty acyl-CoA into the mitochondrial matrix.

Fatty acyl-CoA

The activated fatty acid molecule (Label 11) formed in the cytosol from FFA-FABP and transported into the mitochondrial matrix for $\beta\text{-oxidation}$.

Acetyl CoA

The central two-carbon metabolic intermediate (Label 12) produced from pyruvate by PDH or from fatty acyl-CoA by $\beta\text{-oxidation}$ that enters the TCA cycle.

ATP-ADP antiporter

The transport protein (Label 13) located in the inner mitochondrial membrane that exports newly synthesized matrix ATP to the cytosol in exchange for cytosolic ADP.

Hexokinase

The cytosolic enzyme (Label 14) that catalyzes the first phosphorylation step of glycolysis, converting Glucose into G-6-P.

Phosphorylase

The enzyme (Label 15) responsible for glycogenolysis in the cytosol, converting stored glycogen into G-1-P.

Phosphofructokinase

The rate-limiting glycolytic enzyme (Label 16) that phosphorylates F-6-P into F-1,6-bisP, consuming ATP.

Fatty acyl-CoA synthase

The cytosolic enzyme (Label 17) that converts FFA-FABP into fatty acyl-CoA, requiring CoA and the hydrolysis of ATP.

3-HAD

The enzyme 3-hydroxyacyl-CoA dehydrogenase (Label 18) operating in mitochondrial $\beta\text{-oxidation}$ to generate Acetyl CoA, NADH, and $\text{FADH}_2$.

PDH

Pyruvate dehydrogenase (Label 19), the mitochondrial matrix enzyme complex that converts pyruvate to Acetyl CoA, producing NADH and $CO_2$.

Citrate synthase

The initial TCA cycle enzyme (Label 20) in the mitochondrial matrix that condenses Acetyl CoA with oxaloacetate.

ICDH

Isocitrate dehydrogenase (Label 21), a regulatory enzyme in the TCA cycle that catalyzes oxidative decarboxylation, yielding NADH and $CO_2$.

KGDH

Alpha-ketoglutarate dehydrogenase (Label 22), an enzyme complex in the mitochondrial TCA cycle that produces NADH and $CO_2$.

ATP synthase

The inner mitochondrial membrane multi-subunit enzyme (Label 23) that harnesses the electrochemical $H^+$ gradient from the ETC to phosphorylate ADP and Pi into ATP.

mATPase

Myosin ATPase (Label 24), the contractile enzyme that hydrolyzes ATP into ADP + Pi to energize cross-bridge cycling between myosin and actin.

Phosphate translocase

The inner mitochondrial membrane transport protein (Label 25) that facilitates the symport of inorganic phosphate (Pi) and $H^+$ into the matrix for ATP synthesis.