KAAP221 Exam 3 (Digestive System/Nutrition/Metabolism)

Metabolism

The sum of all chemical reactions in the body, including both building (anabolism) and breaking down (catabolism).

Polymer

A large molecule made of many repeating smaller units (monomers), such as proteins or carbohydrates.

Monomer

A small building-block molecule that can join with others to form a polymer.

Hydrolysis

The process that breaks polymers into monomers by adding water (used in digestion/catabolism).

Dehydration synthesis

The process that combines monomers into polymers by removing water (used in anabolism).

Energy currency of the cell

A term referring to ATP because it stores and transfers energy for cellular processes.

Oxidation

Loss of electrons (or hydrogen); releases energy.

Reduction

Gain of electrons (or hydrogen).

Redox reaction

A paired reaction where one molecule is oxidized and another is reduced.

NAD (nicotinamide adenine dinucleotide)

A coenzyme that accepts electrons and becomes NADH.

FAD (flavin adenine dinucleotide)

Another coenzyme that accepts electrons and becomes FADH₂.

NADH / FADH₂

High-energy electron carriers used to help produce ATP.
Carry Hydrogen ions and other electrons during metabolic processes e.g. glycolysis, ETC,

Beta-oxidation

Process that breaks down fatty acids to produce energy (after lipolysis). Occurs in the mitochondria to generate acetyl-CoA.

Cortisol

Stress hormone that increases blood glucose by breaking down fats and proteins

Epinephrine (adrenaline)

Increases heart rate and stimulates energy release.

Cytokines

Signaling molecules that can promote breakdown processes during immune responses.

IGF (Insulin-like Growth Factor)

Promotes muscle and bone growth and prevents cell death, produced in the liver.

Testosterone

Increases muscle mass and bone strength.

Estrogen

Supports metabolism and fat storage.

Lipolysis

Triglycerides are broken into fatty acids + glycerol (by hydrolysis).

Chylomicron

A lipoprotein that transports dietary fats through the lymphatic system and bloodstream.

Cholecystokinin (CCK)

A digestive hormone that stimulates release of bile and pancreatic lipase and helps digest fats & proteins.

Glycerol

The backbone of triglycerides; enters glycolysis to help produce ATP.

Fatty acyl CoA

An activated fatty acid molecule that can enter β-oxidation

Carnitine

A molecule that transports fatty acids into the mitochondria.

Acetyl CoA

A key molecule that enters the Krebs cycle to produce ATP.

Ketogenesis

The process of converting excess acetyl CoA into ketone bodies when glucose is low

Ketone bodies

Alternative energy molecules produced from fat (e.g., β-hydroxybutyrate)

Starvation metabolism

A metabolic state where the body relies on fat and ketones for energy.

Acetoacetate

A ketone body that is converted into acetyl CoA during energy production.

Acetoacetyl CoA

An intermediate that splits into two acetyl CoA molecules.

Ketoacidosis

A dangerous condition where excess ketones make the blood acidic.

Acetone

A byproduct of ketone breakdown that is exhaled (causes fruity breath).

Lipogenesis

The process of converting excess glucose into fatty acids and triglycerides for storage.

Adipocytes

Fat cells that store triglycerides.

Hepatocytes

Liver cells where lipogenesis also occurs

Malonyl CoA

A molecule used to build fatty acids during lipogenesis

Citrate shuttle

A process that transports acetyl CoA out of the mitochondria for fat synthesis

Fatty acid synthesis

The building of fatty acid chains from acetyl CoA.

Energy storage

The conversion of excess nutrients into fat for later use.

Alternative fuel source

Ketones used when glucose is unavailable.

Thermoregulation

The process by which the body maintains a stable internal temperature despite changes in the environment.

Hypothalamus

The part of the brain that acts as the body’s “thermostat,” regulating temperature.

Vasodilation

Widening of blood vessels near the skin to release heat.

Vasoconstriction

Narrowing of blood vessels to conserve heat.

Thyroid hormone

A hormone that increases metabolism and heat production.

Thermoneutral environment

An environment where the body does not need to expend energy to maintain temperature.

Heat exchange

The transfer of heat between the body and the environment.

Metabolic rate

The total amount of energy the body uses compared to what it consumes

Basal metabolic rate (BMR)

The amount of energy the body uses at rest to maintain basic functions.

Energy expenditure

The total amount of energy the body uses in a day.

Postabsorptive state

The state after digestion when the body is not actively absorbing nutrients.

Lean body mass

The amount of muscle in the body, which increases metabolic rate.

Nutritional calorie

A unit of energy; the amount of heat needed to raise 1 kg of water by 1°C.

Hypervitaminosis

A condition caused by excessive vitamin intake, especially fat-soluble vitamins.

Mouth

Ingests food; begins mechanical digestion (chewing) and chemical digestion (salivary enzymes).

Pharynx

Passageway that propels food from mouth to esophagus.

Esophagus

Moves food to the stomach via peristalsis

Stomach

Churns food into chyme; begins protein digestion.

Small intestine

Main site of digestion and nutrient absorption.

Large intestine

Absorbs water/electrolytes; forms and eliminates feces.

Anus

Controls defecation (elimination of waste).

Tongue

Moves food; helps form bolus; aids swallowing.

Salivary glands

Secrete saliva to begin carbohydrate digestion.

Liver

Produces bile to emulsify fats

Gallbladder

Stores and concentrates bile; releases it into small intestine.

Pancreas

Produces digestive enzymes and bicarbonate to neutralize acid

Mucosa

Inner lining of the stomach; secretes mucus, absorbs nutrients, and protects.

Submucosa

Connective tissue layer with blood vessels, glands, and nerves. (stomach)

Muscularis externa

Smooth muscle layers that enable movement in stomach (peristalsis).

Serosa

Outer layer; reduces friction and anchors organs (part of peritoneum).

Peritoneum

Serous membrane that anchors and supports digestive organs.

Mesenteries & folds

Hold organs in place and carry blood vessels, nerves, and lymphatics.

Incisors (8 total)

Front teeth; cut and bite food.

Canines/cuspids (4 total)

Next to incisors; tear food.

Premolars/bicuspids (8 total)

Behind canines; crush and mash food.

Molars (12 total)

Back teeth; grind food thoroughly (includes wisdom teeth).

Process of swallowing

• Voluntary phase (oral phase) –

  • Tongue pushes bolus to back of mouth into pharynx.

• Pharyngeal phase (involuntary) –

  • Soft palate & uvula close nasal cavity.

  • Epiglottis covers airway (trachea) to prevent choking.

  • Upper esophageal sphincter relaxes to allow food into esophagus.

• Esophageal phase (involuntary) –

  • Peristalsis moves bolus down esophagus to stomach.

Lower esophageal sphincter

Relaxes to allow entry into stomach

Cardia

Region where the esophagus connects to the stomach; entry point of food

Fundus

Dome-shaped upper portion of the stomach above the cardia

Body of the stomach

Largest central region; main site of mixing and digestion.

Pylorus

Funnel-shaped region connecting the stomach to the duodenum.

Pyloric sphincter

Ring of smooth muscle controlling the release of chyme into the duodenum

Rugae

Folds of the stomach lining that allow expansion when the stomach fills

Parietal cells

Secrete hydrochloric acid (HCl) and intrinsic factor (needed for vitamin B12 absorption).

Chief cells

Secretes pepsinogen, which is activated into pepsin for protein digestion

Mucous neck cells

Secrete acidic mucus (function not fully understood)

Enteroendocrine cells

Secrete hormones (especially gastrin) that regulate digestion

Mucosal barrier (why the stomach does not digest itself)

Protective system preventing self-digestion:

• Thick bicarbonate-rich mucus neutralizes acid.

• Tight junctions prevent acid leakage into tissues.

• Rapid cell replacement (every 3–6 days) repairs damage.

Mixing waves

Peristaltic contractions that occur every ~20 seconds to churn food.

Chyme formation

Food mixes with gastric juices to form a semi-liquid substance.

Gastric emptying

Small amounts of chyme (≈3 mL at a time) pass through the pyloric sphincter into the duodenum.

Hydrochloric acid (HCl)

• Creates acidic environment (pH 1.5–3.5)

• Kills bacteria

• Denatures proteins

Pepsin

Enzyme that begins protein digestion (activated from pepsinogen).

Gastric lipase

Begins triglyceride (fat) digestion

Chyme

Semi-liquid mixture of food and gastric juices.

Minimal absorption

Only small amounts (like alcohol and aspirin) are absorbed in the stomach.

Hepatocytes

Main liver cells; process nutrients and produce bile.

Hepatic sinusoids

Porous capillaries for blood flow and exchange.