BI102 Lecture 10

Chapter 46

Heterotrophs

Organisms that cannot produce their own food and must obtain energy and nutrients by consuming other organisms.

Nutrient

Any substance taken in by an organism that is needed for survival, growth, development, tissue repair, or reproduction.

Essential nutrients

Certain compounds that cannot be synthesized from any ingested or stored precursor molecule and must be obtained from the diet.

Intracellular digestion

A digestion process that occurs within cells, using phagocytosis to bring food particles directly into a cell.

Extracellular digestion

Occurs in most animals, allowing for the consumption of large food items and protecting cells from hydrolytic enzymes.

Alimentary canal

A single elongated tube with an opening at both ends, containing specialized regions that perform different digestive functions.

Digestion stages

The processes of ingestion, digestion, absorption, assimilation, and elimination of waste products.

Mechanical digestion

The physical breakdown of food into smaller pieces, such as chewing.

Chemical digestion

The enzymatic breakdown of food into simple nutrients.

Peristalsis

A wave of contraction in the smooth muscle that propels food through the digestive tract.

Gastric glands

Cells in the gastric epithelium that secrete mucus, pepsinogen, and hydrochloric acid.

Chyme

A solution that contains water, ions, protein fragments, nucleic acids, carbohydrates, fat droplets, and other small molecules, formed in the stomach.

Ruminants

Herbivores, such as cows and sheep, that have a specialized forestomach allowing for the regurgitation and fermentation of cellulose.

Mucosa

The innermost layer of the stomach lining that secretes digestive enzymes and mucus.

Sphincters

Muscles that regulate the passage of food and waste through the digestive system.

Nucleic acids

Biomolecules that provide sugars, bases, and phosphates for the synthesis of DNA, RNA, and ATP.