Brain Energy Metabolism - Vocabulary Flashcards (Video Notes)

Vocabulary flashcards covering key terms from the lecture on brain energy metabolism, lipid droplets in neurons, transporters, shuttles, imaging methods, and broader context.

Glycolysis

Cytosolic pathway that converts glucose to pyruvate; yields ATP and NADH; can operate aerobically or anaerobically.

Pyruvate Dehydrogenase Complex (PDH)

Mitochondrial enzyme complex that converts pyruvate to acetyl-CoA, linking glycolysis to the TCA cycle.

Pyruvate Carboxylase

Anaplerotic enzyme that converts pyruvate to oxaloacetate to replenish TCA cycle intermediates.

TCA Cycle (Krebs Cycle)

Mitochondrial cycle oxidizing acetyl-CoA to CO2, generating NADH, FADH2, and ATP.

Electron Transport Chain (ETC)

Mitochondrial protein complexes that transfer electrons to oxygen, creating a proton gradient for ATP synthesis.

Oxidative Phosphorylation

ATP production via ATP synthase driven by the ETC proton gradient.

Beta-Oxidation

Fatty acid catabolism in mitochondria producing acetyl-CoA for the TCA cycle.

CPT1 (Carnitine Palmitoyltransferase 1)

Rate-limiting transporter that shuttles long-chain fatty acids into mitochondria for oxidation.

Ketone Bodies

Acetoacetate, beta-hydroxybutyrate, and acetone; produced in liver and used by brain when glucose is scarce.

Monocarboxylate Transporters (MCTs)

Transporters that move lactate, ketone bodies, and other monocarboxylates across membranes.

Malate–Aspartate Shuttle

Redox shuttle transferring cytosolic NADH electrons into mitochondria via malate and aspartate exchanges.

Glutamate–Glutamine Shuttle

Astrocyte–neuron cycle: glutamate to glutamine in astrocytes, then back to neurons for neurotransmission.

GABA–Glutamate Shuttle

Interconnected metabolism of GABA and glutamate involving transamination and cycling.

Glutamine Synthetase

Astrocytic enzyme that converts glutamate to glutamine, aiding ammonia buffering and neurotransmitter cycling.

Glutaminase

Enzyme that converts glutamine to glutamate, enabling neurotransmitter synthesis and cycling.

Ammonia Buffering by Glutamate

Glutamate helps buffer ammonia in the brain via transamination and related reactions.

Lipid Droplets in Neurons

Intracellular lipid storage that can co-localize with synapses and mitochondria under lipid metabolic conditions.

DDHD2

Brain-enriched lipase linked to lipid metabolism and lipid droplet dynamics at synapses.

Etomoxir

CPT1 inhibitor used to block fatty acid transport into mitochondria and alter lipid oxidation.

APOE (Apolipoprotein E)

Brain lipid transport protein; associated with Alzheimer's disease risk and brain lipid metabolism.

2-Deoxyglucose (2-DG)

Glucose analog used to trace glucose uptake in PET imaging; becomes trapped after phosphorylation.

FDG-PET

Positron emission tomography using fluorodeoxyglucose to measure regional glucose metabolism.

BOLD fMRI

Imaging modality based on blood-oxygen-level-dependent signal to infer neural activity.

Cerebral Metabolic Rate of Oxygen (CMRO2)

Rate of oxygen consumption by the brain; index of oxidative metabolism.

Cerebral Metabolic Rate of Glucose (CMRGlc)

Rate of glucose utilization by the brain; often compared with CMRO2.

Respiratory Quotient (RQ)

Ratio of CO2 produced to O2 consumed; indicates predominant fuel (near 1 with glucose).

NMR Isotopomer Tracing

Use of labeled isotopes (e.g., 13C) to track metabolic fluxes via NMR.

13C MRS

Magnetic resonance spectroscopy using 13C labeling to follow carbon flow in metabolic networks.

Glutamate Decarboxylase (GAD)

Enzyme that converts glutamate to GABA in neurons, a key step in GABAergic transmission.

Glutamine Synthetase vs Glutaminase (enzyme pair)

GS converts glutamate to glutamine in astrocytes; glutaminase converts glutamine to glutamate in neurons.

Glutamate–Glutamine Cycle

Neurotransmitter cycling between neurons and astrocytes to maintain neurotransmitter pools.

Glutamate as Neurotransmitter Cycle Carrier

Core concept of how glutamate and its metabolites cycle between cells to sustain signaling.

Lactate Shuttle Controversy (ANLS)

Debate whether astrocyte-produced lactate is a primary neuronal fuel; alternative glycogen-based models exist.