Chapter 7: Energy Metabolism

Vocabulary flashcards covering cellular sites of metabolism, anabolism, catabolism, carbohydrate and lipid breakdown, protein deamination, ATP generation, fasting states, and the metabolic impact of alcohol.

Photosynthesis

The biological process by which green plants synthesize simple sugars from carbon dioxide and capture solar energy in the chemical bonds of those sugars.

Cytoplasm

A lattice-like internal cellular structure that supports and regulates the movements of organelles and cell components.

Cytosol

A protein-rich, jelly-like fluid that fills the spaces within the cytoplasm lattice and contains the specific enzymes required for glycolysis.

Mitochondria

Intricately folded cellular organelles known as the "powerhouses" of the cell that house enzymes for pyruvate conversion to acetyl CoA, fatty acid oxidation, the TCA cycle, and the electron transport chain.

Smooth Endoplasmic Reticulum

An intracellular network of membranes that serves specifically as the site of lipid synthesis.

Rough Endoplasmic Reticulum

An intracellular membrane network dotted with ribosomes that functions as the site of protein synthesis.

Anabolism

Metabolic reactions in which smaller, simpler molecules are assembled to build larger body compounds, a process that requires energy.

Catabolism

Metabolic reactions in which complex body compounds are broken down into simpler molecules, releasing energy in the process.

Adenosine Triphosphate (ATP)

A high-energy nucleotide compound composed of adenosine and three phosphate groups that captures and stores chemical energy released from nutrient breakdown.

Coupled Reactions

A metabolic event where the energy-releasing hydrolysis of ATP occurs simultaneously with and drives an energy-requiring reaction.

Coenzymes

Complex organic molecules, often derived from B vitamins, that work closely with enzymes to facilitate metabolic reactions without being proteins themselves.

Glycolysis

The metabolic pathway in the cytosol that splits a $6$-carbon glucose molecule into two $3$-carbon pyruvate molecules, releasing energy and hydrogens to coenzymes.

Pyruvate

A $3$-carbon compound generated at the end of glycolysis that can either be converted to acetyl CoA aerobically or lactate anaerobically, or used to resynthesize glucose.

Acetyl CoA

A $2$-carbon compound with a coenzyme A attached that enters the TCA cycle to generate ATP or serves as a building block for synthesized fatty acids, but cannot make glucose.

Cori Cycle

The inter-organ metabolic pathway in which lactate generated by working muscles under anaerobic conditions travels to the liver, is converted to glucose via gluconeogenesis, and returns to the muscles.

Gluconeogenesis

The synthesis of glucose from noncarbohydrate precursors, such as amino acids and the glycerol portion of triglycerides, occurring primarily in the liver and kidneys during starvation.

Fatty Acid Oxidation

The metabolic process of breaking down fatty acid chains into $2$-carbon fragments of acetyl CoA inside the mitochondria.

Ketone Bodies

Acidic, water-soluble compounds (such as acetoacetate, acetone, and beta-hydroxybutyrate) synthesized by the liver from condensed acetyl CoA units during carbohydrate depletion or prolonged fasting.

Ketosis

An altered metabolic state marked by high concentrations of ketone bodies (keto acids) circulating in the blood, which lowers blood pH.

Deamination

The initial biochemical removal of the nitrogen-containing amino group ($\text{NH}_2$) from an amino acid, resulting in the production of ammonia ($\text{NH}_3$).

Glucogenic Amino Acids

Amino acids that can be converted into pyruvate or enter the TCA cycle directly as intermediates, thereby possessing the ability to yield new glucose.

Ketogenic Amino Acids

Amino acids degraded directly into acetyl CoA, which can yield energy, ketone bodies, or fat stores, but cannot be converted into glucose.

Oxaloacetate

A $4$-carbon intermediate carbohydrate derivative needed in the first reaction of the TCA cycle to condense with acetyl CoA, and regenerated in the cycle's final step.

TCA Cycle

The final common circular metabolic pathway located in the inner mitochondrial compartment that oxidizes acetyl CoA to carbon dioxide ($\text{CO}_2$), releasing electrons to coenzymes.

Electron Transport Chain

A series of sequential electron-carrier proteins embedded in the inner mitochondrial membrane that harness electron energy to pump hydrogen ions ($\text{H}^+$) and drive ATP synthesis.

Ketogenic Diet

A dietary regimen that restricts daily carbohydrate intake to less than $30\,\text{g}$ while providing $1.2$ to $1.5\,\text{g/kg}$ body weight of protein, forcing the body to rely on fat oxidation and ketone production.

Alcohol (Ethanol)

The intoxicating compound found in alcoholic beverages; clinically, one standard drink provides $\frac{1}{2}\,\text{ounce}$ of pure ethanol.

Alcohol Dehydrogenase

An enzyme produced in the stomach and liver that catalyzes the initial oxidation of ethanol to acetaldehyde.

Acetaldehyde

A reactive, toxic intermediate compound formed when alcohol dehydrogenase oxidizes ethanol by removing hydrogen atoms.

Steatosis

An early, reversible stage of alcohol-related liver disease (fatty liver) characterized by abnormal accumulation of fat droplets in more than $5\%$ of hepatocytes.

Cirrhosis

The advanced, irreversible stage of liver disease characterized by permanent scar tissue formation (fibrosis) and loss of normal liver function.

Wernicke-Korsakoff Syndrome

A severe neurological disorder caused by alcohol-induced thiamin (vitamin B1) deficiency and characterized by eye movement abnormalities, loss of coordination, and memory impairment.