Fundamentals of Metabolism: Pathways, Energy, and Regulation

Insulin (Anabolic Hormone)

Promotes the synthesis of glycogen, fat, and protein while decreasing glucose production.

Glucagon/Epinephrine (Catabolic)

Hormones that stimulate the breakdown of stored energy (glycogen and fat) to increase blood glucose and available energy.

Oxidation-Reduction (Redox)

Reactions where electrons are transferred; Oxidation is the loss of electrons, and Reduction is the gain of electrons.

Metabolism

The chemical processes involved in maintaining life by releasing energy from nutrients (carbs, fat, protein) and synthesizing new substances.

Anabolic Pathways

Metabolic processes that use energy (ATP) to build complex molecules from simpler ones (e.g., building muscle).

Catabolic Pathways

Metabolic processes that break down complex molecules into simpler units, resulting in the release of energy (ATP).

ATP (Adenosine Triphosphate)

The primary energy currency of the cell; energy is released when the bond between phosphate groups is broken.

Glycolysis

The metabolic pathway that breaks down glucose into two molecules of pyruvate; it occurs in the cytosol and does not require oxygen (anaerobic).

Transition Reaction

The process of converting pyruvate into Acetyl-CoA; this step is irreversible and occurs in the mitochondria.

Citric Acid Cycle (TCA Cycle)

A series of reactions in the mitochondria that uses Acetyl-CoA to produce CO2, a small amount of ATP, and energy-carrying molecules (NADH and FADH2).

Electron Transport Chain (ETC)

The final stage of aerobic respiration where the majority of ATP is produced using oxygen as the final electron acceptor.

Lipolysis

The breakdown of triglycerides into free fatty acids and glycerol.

Beta-Oxidation

The process of breaking down fatty acids into 2-carbon fragments (Acetyl-CoA) to enter the Citric Acid Cycle. (oxygen not required) Occurs in the Mitochondria matrix

Ketone Bodies

Products formed from incomplete fatty acid oxidation, often occurring during starvation or very low carbohydrate intake.

Gluconeogenesis

The synthesis of glucose from non-carbohydrate sources, such as specific amino acids or glycerol; primarily occurs in the liver.

Urea Cycle

The process by which the liver converts toxic ammonia (a byproduct of amino acid breakdown) into urea to be excreted in urine.

High ATP Levels

A metabolic signal that decreases energy-yielding reactions and promotes anabolism (storage/building).

High ADP/AMP Levels

Signals that stimulate catabolic pathways to produce more energy.

A Metabolic Pathway

progression of biochemical reactions Reactant -> Intermediate -> Product

Deamination

Removal of amino groups from amino acids to use for fuel.

Requires Vitamin B-6

Co-Enyzmes

help the enzymes catalyze reactions

electron carriers

Co-enyzmes Reduced/ Oxidized

Niacin(B3) Oxidized: NAD+ Reduced: NADH

Riboflavin(B2) Oxidized: FAD Reduced: FADH2