Biol 216 Topic 12: The Digestive System

Flashcards covering key vocabulary terms from the digestive system lecture.

Metabolism

The biochemical reactions that allow a cell or organism to extract energy from its surroundings and use that energy for homeostasis, growth, and reproduction.

Organic Molecule

A molecule based on carbon that provides energy and building blocks for complex biological molecules.

Carbohydrate

A biological molecule consisting of simple single monomer sugars (monosaccharides), two-monomer sugars (disaccharides), and other multi-unit sugars (polysaccharides).

Monosaccharide

The smallest kind of sugar molecule, a simple sugar, and a single unit sugar that is a building block of more complex sugars.

Disaccharide

Comprises two monosaccharides linked via a dehydration reaction (e.g., Sucrose, Lactose, Maltose).

Polysaccharide

Polymers of monosaccharides, long chains of sugar units (e.g., Starch, Glycogen, Cellulose).

Lipid

Organic compound consisting mainly of carbon and hydrogen atoms linked by non-polar, covalent bonds, making it mostly hydrophobic and insoluble in water; includes fats, phospholipids, and steroids.

Fat

A type of lipid molecule, dietary fat is mostly triglycerides made from glycerol and three fatty acids; functions include energy storage, cushioning, and insulation.

Unsaturated Fat

Fewer than the maximum number of hydrogens bonded to the carbon resulting in a double bond (which creates a “bend” in the fatty acid chain); tends to be liquid at room temperature.

Saturated Fat

All carbons of the fatty acid backbone are bonded to the maximum number of hydrogens (no “bend”); tend to be solid at room temperature.

Essential Nutrients

Substances animals require in their diets that they cannot make for themselves, including essential amino acids, essential fatty acids, minerals, and vitamins.

Vitamins

Organic molecules required in small quantities that an animal cannot synthesize for itself.

Minerals

Ions required for neuron excitability, cardiac muscle contraction, structural material, and parts of other molecules.

Sphincters

Rings of smooth muscle that form valves between major regions of the digestive tract.

Mucosa

The layer that lines the inside of the gut; its epithelial cells absorb nutrients and seal off digestive contents, while glandular cells secrete enzymes, mucus, and regulate pH.

Submucosa

A layer of elastic connective tissue that contains a neuron network of blood and lymph vessels. This neural network controls local digestive activity.

Muscularis

Formed by circular and longitudinal muscle layers that push contents through the gut via peristalsis; the stomach also has an oblique layer.

Serosa

The outermost gut layer made of connective tissue that is continuous with mesentery and secretes a lubricating fluid.

Peristalsis

Coordinated contractions of circular and smooth muscles produce peristaltic waves that move digestive contents from mouth to anus.

Salivary Amylase

An enzyme secreted by salivary glands that digests starch in the mouth.

Gastric Juice

Secreted by the stomach; contains hydrochloric acid and the protein-digesting enzyme pepsin.

Pepsinogen

The precursor for pepsin, secreted by chief cells in the stomach.

Chyme

Acidic stomach contents.

Gastrin

A major hormone that regulates acid secretion in the stomach, stimulated by stomach distension and digested proteins.

Intestinal Villi

Folds in lining of small intestine that increase the surface area for absorption.

Microvilli

Projections of plasma membrane of epithelial cells that greatly increase the surface area of the intestine.

Bile

A substance secreted by the liver and stored in the gallbladder, it emulsifies fats in the small intestine.

Bicarbonate Ions

Secreted by the pancreas; that neutralize acidity of Chyme.

Proteolytic Enzymes

Trypsin, chymotrypsin, and carboxypeptidase which are secreted by the pancreas.

Lipase

Pancreatic enzyme that hydrolyzes triglycerides.

Amylase

Pancreatic Enzyme that hydrolyzes polysaccharides.

Nucleases

Pancreatic enzyme that hydrolyzes Nucleic acids (DNase, RNase).

Glucagon

Hormone from the pancreas (alpha cells) released when blood glucose levels are low, causing the liver to convert glycogen into glucose.

Insulin

Hormone from the pancreas (beta cells) that causes cells to take up glucose from the blood, storing it as glycogen.

Micelle

Structure in aqueous solution with molecules aggregated with hydrophilic “head” regions in contact with solvent, sequestering hydrophobic tail regions in the center.

Chylomicrons

Lipoprotein particles comprising triglycerides, phospholipids, cholesterol, and proteins that transport lipids from the intestine to tissues.

Hepatic Portal Vein

Nutrient molecules absorbed from the small intestine are carried by capillaries that collect into veins. Veins join to form the Hepatic portal vein.

Enteric Nervous System (ENS)

A subdivision of the peripheral nervous system (PNS) that directly controls the gastrointestinal system.

Secretin

Released when acidic chyme enters duodenum, prevents further acid from entering the duodenum until the chyme is neutralized.

Cholecystokinin (CCK)

Inhibits gastric activity, allows time for nutrients in duodenum to be digested, absorbed. Stimulates release of pancreatic enzymes and bile from the gallbladder.

GIP

Glucose-dependent insulinotropic peptide, secreted when a meal enters the digestive tract, stimulates insulin release.

Leptin

Hormone secreted by adipose cells that binds receptors in the hypothalamus to reduce appetite and increase metabolic rate.

Ghrelin

Hormone that triggers hunger.

PYY (Peptide YY)

Secreted by the small intestine after meals to suppress appetite.