Digestive System, Macromolecules, and Biomass Rearrangement

Comprehensive vocabulary flashcards covering digestive system anatomy, enzyme function, mechanical and chemical digestion, feeding niches, macromolecule biochemistry, and nitrogen cycling.

Digestion

The biological process by which the digestive system breaks food down into simpler, useful nutrients.

Absorption

The physiological process by which digested nutrient molecules pass through the walls of the digestive tract and enter the bloodstream or lymphatic system.

Elimination

The process by which leftover, compacted digestive waste that cannot be used by the body is expelled from the digestive tract.

Mechanical Digestion

The physical breakdown of food chunks into smaller pieces by the teeth in the mouth and the muscular churning of the stomach walls.

Chemical Digestion

The breakdown of complex food molecules into simpler nutrients through the action of digestive enzymes and acidic secretions.

Peristalsis

Rhythmic, wave-like muscular contractions of the digestive tract walls that propel food through the digestive organs.

Food Calorie (Calorie)

A unit of dietary energy supplied by food nutrients (carbohydrates, proteins, and fats), where each Calorie is equivalent to $4,184\text{ joules}$ of energy.

Chyme

A thick, semi-liquid mixture of partially digested food chunks and gastric secretions produced by the mechanical churning of the stomach walls.

Amylase

A digestive enzyme produced by salivary glands and the pancreas that breaks down complex carbohydrates (starches) into simple sugars.

Trypsin

A digestive enzyme secreted by the pancreas that breaks down proteins into individual amino acid building blocks.

Lipase

A digestive enzyme produced by the pancreas that hydrolyzes dietary fats into fatty acids and monoglycerides.

Bile

A chemical fluid stored in the gallbladder that emulsifies large fat droplets into tiny droplets, allowing water-based lipase enzymes to digest them efficiently.

Pepsin

A protein-digesting enzyme produced in the stomach that initiates the breakdown of proteins and functions optimally in a highly acidic environment.

Gastric Chief Cells

Specialized secretory cells in the stomach lining that produce and release the digestive enzyme pepsin.

Parietal Cells

Specialized epithelial cells in the stomach lining that secrete hydrochloric acid ($HCl$) to create the acidic conditions necessary for pepsin activity.

Duodenum

The uppermost section of the small intestine directly connected to the stomach, where chyme mixes with bile and pancreatic digestive enzymes.

Villus

A microscopic, fingerlike projection extending from the inner mucosal wall of the small intestine that increases surface area for nutrient and water absorption.

Lacteal

A specialized lymphatic capillary located in the core of an intestinal villus that absorbs digested fatty acids and transports them to the bloodstream.

Capillaries

Microscopic blood vessels situated within intestinal villi that absorb water, simple sugars, and amino acids and transport them into the circulatory system.

Fiber

A complex, indigestible plant carbohydrate that human enzymes cannot break down, though large-intestine bacteria ferment portions of it into absorbable sugars.

Large Intestine

The final section of the gastrointestinal tract responsible for reabsorbing water, absorbing vitamin K, and compacting waste into feces.

Carnivore

An organism specialized in consuming animal tissue (meat), characterized by sharp teeth, a short digestive tract, and the absence of a functional cecum.

Herbivore

An organism specialized in consuming plant material, characterized by flat grinding teeth, a long digestive tract, and a large cecum to break down tough plant cell walls.

Omnivore

An animal whose dietary niche incorporates both plant material and animal meat, possessing physical adaptations for processing both food types.

Cecum

A specialized pouch branching off the digestive tract that houses symbiotic microorganisms capable of fermenting and breaking down tough plant cellulose.

Cellulose

A rigid, large complex carbohydrate ($CHO$) composing plant cell walls that contains difficult-to-break chemical bonds requiring prolonged microbial digestion.

Hydrolysis

A chemical reaction occurring during digestion that cleaves large biological polymers into smaller absorbable monomers through the addition of water ($H_2O$) molecules.

Dehydration Synthesis

A biochemical reaction that connects monomers together into new bodily polymers and tissue structures by removing water ($H_2O$) molecules.

Cellular Respiration

The metabolic process carried out in the mitochondria wherein cells break Carbon-Carbon ($C-C$) bonds from digested nutrients to synthesize usable ATP energy.

Adenosine Triphosphate (ATP)

The primary usable chemical energy currency synthesized by mitochondria during cellular respiration to fuel biological cellular work.

Lipids

Biological macromolecules composed of Carbon, Hydrogen, and Oxygen ($C, H, O$ with few $O$ atoms) that yield the most energy per gram due to their dense Carbon-Carbon ($C-C$) bonds.

Proteins

Macromolecules composed of Carbon, Hydrogen, Oxygen, Nitrogen ($C, H, O, N$, and sometimes sulfur $S$) that form structural tissues, skin, muscles, enzymes, and cellular communication molecules.

Biomass

The total mass or weight of living biological organisms in a specific area, synthesized through food consumption and molecular rebuilding.

Nitrogen Gas ($N_2$)

An inert atmospheric gas comprising $78\%$ of Earth's atmosphere that is completely unusable by plants until converted into nitrates by soil bacteria.

Nitrates ($NO_3^-$)

Usable nitrogen-containing chemical compounds produced by soil bacteria that are absorbed by plant roots to construct amino acids and plant proteins.