HNES 351 Metabolic Basis of Nutrition Exam 1 Study Guide Chapters 2 and 4

Vocabulary flashcards covering major digestive organs and functions, enzymes and their sites of secretion/actions, gastric juice components, GI hormones, GI immune protection, regulation of secretion and emptying, absorption mechanisms, bile and fat digestion, gut microbiota concepts, and roles of dietary fiber in disease.

Mouth

Oral cavity where mechanical digestion (chewing) and chemical digestion begin; saliva (including salivary amylase) starts carbohydrate digestion.

Esophagus

Muscular tube that transports swallowed food to the stomach via peristaltic waves; no significant digestion occurs here.

Stomach

Sac where gastric juice (HCl, pepsinogen/pepsin, mucus) digests protein and forms chyme; acidic environment; intrinsic factor produced.

Small intestine

Primary site of digestion and absorption; receives enzymes from pancreas and brush-border enzymes; villi/microvilli maximize absorption.

Large intestine

Adds water and electrolytes, houses gut microbiota; forms feces; fermentation yields short-chain fatty acids.

Liver

Produces bile; processes and metabolizes nutrients; detoxification.

Gallbladder

Stores and concentrates bile; releases bile into the duodenum in response to CCK.

Pancreas

Produces pancreatic juice containing enzymes (amylase, proteases, lipase) and bicarbonate; released into the small intestine.

Gastric juice – HCl

Acidic environment in the stomach; denatures proteins and activates pepsinogen to pepsin; helps kill microbes.

Gastric juice – Pepsinogen/Pepsin

Pepsinogen is activated by HCl to pepsin; pepsin digests proteins into smaller peptides.

Gastric juice – Mucus

Mucus layer protects gastric mucosa from acid and enzymes and lubricates the stomach lining.

Gastric juice – Intrinsic factor

Glycoprotein essential for vitamin B12 absorption in the ileum.

Gastrin

Gastrointestinal hormone released from stomach G-cells; stimulates acid secretion by parietal cells and promotes gastric motility.

Secretin

Hormone released by the duodenum in response to acid; stimulates pancreatic bicarbonate secretion and slows gastric secretion.

Cholecystokinin (CCK)

Hormone released from the duodenum in response to fat/protein; stimulates pancreatic enzyme secretion and gallbladder contraction; slows gastric emptying.

Ghrelin

Hormone produced mainly in the stomach; stimulates hunger.

Somatostatin

Inhibitory hormone that decreases GI secretions and motility; helps regulate gastric acid production.

Gastric inhibitory peptide (GIP)

Incretin hormone from the small intestine that enhances insulin secretion in response to oral glucose.

Secretory IgA

Antibody class secreted into mucosal surfaces; neutralizes pathogens and toxins in the GI tract.

GALT (gut-associated lymphoid tissue)

Immune tissue in the GI tract (includes Peyer's patches) that provides immune defense against luminal antigens.

Tight junctions

Protein complexes between epithelial cells that limit paracellular transport and help maintain the intestinal barrier.

Endocytosis

Absorption method where cells engulf substances; used for large complexes like vitamin B12-intrinsic factor.

Brush border enzymes

Enzymes attached to microvilli (e.g., lactase, sucrase, maltase, aminopeptidases) that complete digestion at the enterocyte border.

Bile

Digestive fluid produced by the liver; emulsifies fats to aid digestion.

Bile salts

Amphipathic molecules in bile that emulsify fats and form micelles to aid fat absorption.

Micelles

Small lipid aggregates formed with bile salts that transport lipids to the enterocyte surface for absorption.

Short-chain fatty acids (SCFA)

Fatty acids (acetate, propionate, butyrate) produced by bacterial fermentation of fiber; important energy source for colonocytes.

Prebiotics

Non-digestible fibers that feed beneficial gut bacteria (e.g., inulin, fructooligosaccharides).

Probiotics

Live beneficial bacteria (e.g., Lactobacillus, Bifidobacterium) that support gut health.

Soluble fiber

Fiber that dissolves in water to form a gel; slows digestion and can lower cholesterol and improve glycemic control.

Insoluble fiber

Fiber that does not dissolve; adds bulk and speeds intestinal transit, promoting laxation.

Functional fiber

Isolated or manufactured fiber added to foods to provide health benefits (e.g., psyllium, inulin).

Cardiovascular disease and dietary fiber

Fiber lowers CVD risk partly by binding bile acids, lowering LDL cholesterol, and improving lipid metabolism.

Dietary fiber and diabetes

Soluble fiber slows glucose absorption and blunts postprandial blood glucose, aiding glycemic control.

Dietary fiber and weight control

Fiber promotes satiety and reduces energy density, supporting weight management.

Dietary fiber and colon cancer

Fiber reduces colon cancer risk by diluting carcinogens, increasing stool bulk, and producing protective butyrate.

Soluble fiber foods (examples)

Oats, barley, beans, apples; form a viscous gel that lowers cholesterol and slows glucose absorption.

Insoluble fiber foods (examples)

Wheat bran, cellulose, vegetables; adds bulk and speeds stool passage.

Functional fiber examples

Psyllium, inulin, polyols added to foods to boost fiber intake.