Metabolism and Energetics

Metabolism

The sum of all chemical reactions in the body.

Catabolism

The breakdown of large molecules into smaller ones, generating ATP.

Anabolism

The synthesis of large molecules from smaller ones, requiring ATP.

Glycolysis location and products

Occurs in the cytosol; converts glucose into two pyruvate molecules and ATP.

Aerobic carbohydrate metabolism location

Occurs in the mitochondria via the TCA cycle and oxidative phosphorylation.

Lactic acid pathway trigger

Low oxygen levels prevent oxidative phosphorylation, converting pyruvate to lactic acid.

Glycogenesis

The synthesis of glycogen from glucose, stimulated by insulin after a meal.

Glycogenolysis

The breakdown of glycogen into glucose, stimulated by glucagon between meals.

Gluconeogenesis

The synthesis of glucose from non-carbohydrate sources like amino acids and fats.

Triglyceride structure

Three fatty acid chains linked by a single glycerol molecule.

Lipolysis

The breakdown of lipids to generate energy.

Lipogenesis

The synthesis of lipids from carbohydrate or protein pathway intermediates.

Essential fatty acids

Lipids that humans cannot synthesize and must obtain through diet.

Chylomicrons

Lipoproteins that carry absorbed lipids from the intestines into lacteals.

LDL vs. HDL

LDL delivers cholesterol to tissues ("bad"); HDL returns it to the liver ("good").

Protein catabolism waste product

Amino groups are converted to toxic ammonia, then to urea for excretion.

Kwashiorkor cause and symptom

Lack of essential amino acids reduces albumin synthesis, causing edema.

Gout cause

The crystallization of uric acid in joints, a product of nucleic acid breakdown.

Neural tissue energy source

Has no energy reserves and demands a continuous supply of glucose.

Absorptive state

0-4 hours post-meal; nutrients enter blood, insulin dominates, and reserves are stored.

Post-absorptive state

4-24 hours post-meal; nutrients stop entering blood, and glucagon mobilizes reserves.

Starvation state energy sources

Liver performs gluconeogenesis and releases ketones; muscle breaks down contractile proteins.

Type 1 Diabetes Mellitus

Autoimmune destruction of pancreatic islet cells, leading to a lack of insulin.

Type 2 Diabetes Mellitus

Insulin resistance caused by desensitized cells, often linked to diet and obesity.

Glycemic index

A measure of how quickly blood sugar levels spike after eating specific foods.

Fat-soluble vitamins

Vitamins A, D, E, and K; stored in adipose, risking toxicity (hypervitaminosis).

Water-soluble vitamins

Vitamins B and C; poorly stored, excreted easily, risking deficiency (hypovitaminosis).

Vitamin B12 absorption requirement

Requires gastric intrinsic factor for absorption in the intestines.

Leptin

A hormone secreted by adipose cells that suppresses hunger.

Heat exhaustion vs. Heat stroke

Exhaustion features profuse sweating and pale skin; stroke features hot, dry skin.

Infant hypothermia susceptibility

High surface area-to-volume ratio, inability to shiver, and reliance on brown fat.