Anatomy & Physiology II - Unit 4: Digestion and Metabolism

Comprehensive vocabulary flashcards covering nutrition, metabolic pathways, energy balance, and the anatomy and physiology of the digestive system.

Nutrient

A substance in food used for growth, maintenance, and repair.

Essential Nutrients

Nutrients the body cannot synthesize and must be obtained from the diet.

Macronutrients

Carbohydrates, proteins, and lipids; needed in large amounts.

Micronutrients

Vitamins and minerals; needed in small amounts.

Monosaccharides

Simple sugars that are water-soluble; examples include glucose, fructose, and galactose ($C_6H_{12}O_6$).

Glycosylation

The process where carbohydrates bind to proteins and lipids to form glycoproteins and glycolipids, crucial for cell surface recognition and protein structure.

Roughage (Fiber)

Undigestible cellulose that adds bulk to feces, aiding digestion.

Essential Fatty Acids

Fatty acids that cannot be synthesized by the body and must be obtained from the diet, such as alpha-linolenic acid (omega-3) and linoleic acid (omega-6).

Cholesterol

A key component of cell membranes and a precursor for steroid hormones (estrogen, progesterone, testosterone), bile salts, and other steroids.

HDL (High-density lipoproteins)

Often referred to as "good cholesterol"; efficiently transports fats throughout the body.

LDL (Low-density lipoproteins)

Often referred to as "bad cholesterol"; can form plaque deposits in blood vessels.

Essential Amino Acids

The nine amino acids that must be obtained from the diet: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Complete Proteins

Proteins that contain all essential amino acids, such as those found in meat, fish, and eggs.

Negative Nitrogen Balance

A state occurring during starvation or inadequate protein intake where the body breaks down protein tissues.

Provitamins

Precursors that the body can convert into functional vitamins, such as beta-carotene being converted to vitamin A.

Metabolism

All chemical processes in the body, consisting of catabolism and anabolism.

Catabolism

The breakdown of complex molecules into simpler ones, usually via hydrolysis.

Anabolism

The building of complex molecules from simpler ones, usually via dehydration synthesis.

Substrate-Level Phosphorylation

The direct transfer of a high-energy phosphate group from a substrate to ADP to form ATP; occurs anaerobically in glycolysis and the citric acid cycle.

Oxidative Phosphorylation

An aerobic process in the mitochondria where energy from nutrient oxidation is used to pump protons ($H^+$) to create a concentration gradient used by ATP synthase to produce ATP.

Glycolysis

The anaerobic breakdown of glucose (6 carbons) into 2 molecules of pyruvic acid (3 carbons each) in the cytosol, yielding a net of 2 ATP and 2 NADH + $H^+$.

Citric Acid Cycle (Krebs Cycle)

A series of reactions in the mitochondrial matrix where acetyl-CoA combines with oxaloacetate to produce $CO_2$, ATP, and reduced coenzymes (NADH and $FADH_2$).

Glycogenesis

The process stimulated by insulin where glucose molecules are linked to form glycogen for storage in the liver and muscles.

Gluconeogenesis

The synthesis of new glucose from non-carbohydrate sources, such as glycerol from fats or amino acids from proteins.

Beta-Oxidation

A mitochondrial process where fatty acid chains are broken down into 2-carbon acetyl groups that attach to Coenzyme A to form acetyl-CoA.

Ketosis

A condition of elevated ketone bodies in the blood often caused by starvation or untreated diabetes, which can leads to metabolic acidosis.

Transamination

The transfer of an amine group ($NH_2$) from an amino acid to a keto acid, essential for synthesizing nonessential amino acids.

Absorptive State

The metabolic state occurring for about 4 hours after a meal where anabolism and storage of excess nutrients are emphasized, using glucose as the primary fuel.

Postabsorptive State

The metabolic state occurring when the GI tract is empty, emphasizing glucose sparing and the mobilization of energy reserves like glycogen and fat.

Basal Metabolic Rate (BMR)

The rate of energy expenditure at rest, which can be increased by hormones such as thyroxine and epinephrine.

Enteric Nervous System (ENS)

A network of neurons in the submucosa and muscularis externa that provides local control of GI tract motility and secretion.

Mesenteries

Folds of peritoneum that suspend organs and attach them to the posterior abdominal wall while housing blood vessels, lymphatics, and nerves.

Rugae

Folds of the stomach mucosa and submucosa that allow the organ to expand when food is ingested.

Parietal Cells

Stomach cells that secrete $HCl$ (which activates pepsinogen and denatures proteins) and intrinsic factor (necessary for vitamin $B_{12}$ absorption).

Chief Cells

Stomach cells that secrete pepsinogen (the inactive precursor to pepsin) and gastric lipase.

Chyme

The semifluid mass of partially digested food and gastric secretions formed in the stomach.

Bile

A substance produced by the liver and stored in the gallbladder that serves to emulsify lipids.

Micelles

Clusters of fatty acids and monoglycerides surrounded by bile salts that allow lipids to diffuse into intestinal epithelial cells.

Chylomicrons

Lipoprotein packages formed within intestinal cells that transport reassembled triglycerides into the lymphatic system.

Secretin

A hormone that stimulates pancreatic and bile secretion rich in bicarbonate and decreases gastric motility.

Cholecystokinin (CCK)

A hormone that stimulates pancreatic enzyme secretion, gallbladder contraction, and the relaxation of the hepatopancreatic sphincter.