NUSC Exam 2 Checklist: Digestion, Carbohydrates, and Lipids

Comprehensive vocabulary flashcards reviewing gastrointestinal physiology, carbohydrate structures and metabolism, and lipid biology based on the NUSC Exam 2 checklist.

Ingestion

Taking food into the body.

Digestion

Breaking food into components small enough so it can be absorbed into the body.

Absorption

Process of taking substances directly into the body.

Transit Time

The time it takes food to pass through the gastrointestinal tract, which is $24\text{--}72\text{ hours}$ in healthy adults.

Mucus

Viscous fluid secreted by the glands of the GI tract responsible for lubricating and protecting the digestive tract from harsh environments.

Enzymes

Protein molecules that speed up the rate of chemical reactions without undergoing any change, assisting with breaking down carbohydrates, protein, and fats into smaller components.

Amylase

An enzyme that breaks down starch into glucose.

Pepsin

An enzyme located in the stomach that breaks down protein into amino acids.

Trypsin

An enzyme that breaks down proteins into amino acids.

Chymotrypsin

An enzyme that breaks down proteins into amino acids.

Lipase

An enzyme that breaks down triglycerides into fatty acids and glycerol.

Hormones

Chemical messengers produced in an organ that are released directly into the blood and generate a response at other locations within the body.

Cephalic Response

A response involving signals from the nervous system where the sights, sounds, and smells of food prepare the digestive system to process food components.

Lysozyme

An enzyme present in saliva that blocks bacterial growth contributing to tooth decay.

Salivary Amylase

An enzyme produced by the salivary glands that starts the breakdown of starch.

Pharynx

The organ responsible for swallowing food contents, and the only digestive system organ shared by both the digestive and respiratory systems.

Epiglottis

A structure that blocks air passages to the lungs as food moves down the digestive tract.

Peristalsis

Muscular contractions that move food down the esophagus and propel chyme from the stomach into the small intestine.

Sphincter

A muscular ring that regulates the passage of food to the stomach.

Chyme

A semi-liquid mixture comprised of bolus and hydrochloric acid that remains in the stomach for $2\text{--}6\text{ hours}$.

Pepsinogen

The inactive precursor to the enzyme pepsin.

Gastrin

A hormone that increases gastric secretion and motility to help digest food.

Segmentation

Horizontal muscular contractions within the small intestine.

Villi

Fingerlike projections in the small intestine that participate in the digestion and absorption of nutrients.

Microvilli

Microscopic projections covering the villi that increase the surface area of the small intestine and contain digestive enzymes.

Lacteals

Small lymph vessels in the small intestine that handle the transport of lipid digestion products.

Secretin

A hormone that signals the pancreas to secrete pancreatic juice and stimulates the liver to secrete bile to the gallbladder.

Cholecystokinin (CCK)

A hormone that signals the pancreas to secrete digestive enzymes and causes the gallbladder to contract and release bile into the duodenum.

Simple Diffusion

The movement of molecules into the small intestinal cell from a high concentration gradient to a low concentration gradient without requiring a carrier protein or energy.

Osmosis

The movement of water from a low concentration of nutrients to a high concentration of nutrients inside of the intestinal cell without requiring energy or a protein carrier.

Active Transport

The movement of molecules from a low to high concentration inside of the cell requiring both a protein carrier and energy.

Facilitated Diffusion

The movement of molecules from a high to low concentration inside of the intestinal cell requiring a protein carrier but no energy.

Gut Microbiota

Microorganisms in the digestive tract that protect against pathogens via colonization resistance, drive immune system maturation, and ferment fiber into short-chain fatty acids while synthesizing vitamins.

Probiotics

Live bacteria or yeast consumed for health benefits.

Prebiotics

Non-digestible plant fibers that feed beneficial microorganisms in the gut.

Dysbiosis

An altered gut microbial environment associated with conditions such as inflammatory bowel disease, obesity, and type 2 diabetes.

Antigen

A foreign substance, such as a protein, that stimulates an immune response when introduced into the body.

Antibody

A protein produced by immune system cells that destroys or inactivates foreign substances in the body.

Lymphocyte

An immune cell that targets specific invaders and directly produces antibodies to destroy antigens.

Phagocyte

An immune cell that targets foreign invaders by engulfing and destroying them.

Gluten

A protein matrix formed by gliadin and glutenin found in wheat, rye, and barley products.

Celiac Disease

An inherited condition affecting $1\text{ in }141$ individuals in the US causing intestinal damage, abdominal pain, fatigue, diarrhea, anemia, and weight loss in response to gluten.

Non-Celiac Gluten Sensitivity

Gluten reactions causing distress within hours or days without identified allergic or autoimmune mechanisms or intestinal damage.

Heartburn

A condition caused by stomach acid leaking upward into the esophagus and eroding tissue, producing a burning sensation in the throat.

Peptic Ulcer

Open sores that develop on the esophageal, stomach, or small intestine lining, caused by Helicobacter pylori or medications like aspirin or ibuprofen.

Diarrhea

Frequent watery stools resulting when digested materials move too quickly through the colon to draw in water or from small intestine inflammation.

Constipation

Bowel movements occurring fewer than $3\text{ times per week}$ characterized by dry, hard stools that are difficult to pass.

Enteral Nutrition

Tube feeding involving the placement of a tube down the throat or through the wall of the GI tract to deliver liquid diets.

Total Parenteral Nutrition (TPN)

A feeding method in which nutrients are provided directly through the circulatory system.

Hepatic Portal System

A vascular system that transports nutrient-rich blood from the digestive organs and delivers it directly to the liver.

Capillaries

Small, thin-walled blood vessels located in the small intestine, circulatory system, and lungs that transport water-soluble nutrients.

Metabolism

The set of life-sustaining chemical reactions in organisms that convert food and oxygen into energy and building blocks for the body.

Catabolism

Metabolic processes that break down complex substances into simpler substances, releasing energy.

Anabolism

Metabolic processes that build complex substances from simpler substances, consuming energy.

Adenosine Triphosphate (ATP)

The high-energy molecule synthesized from catabolic reactions used by the body to perform energy-requiring activities.

Refined Carbohydrates

Carbohydrate foods that underwent processing, such as corn flakes, white bread, canned fruit, and French fries.

Unrefined Carbohydrates

Carbohydrate foods that remain in their natural state, such as oatmeal, whole wheat bread, whole wheat pasta, raspberries, apples, and baked potatoes.

Endosperm

The largest portion of the grain kernel containing starch, protein, and some vitamins and minerals.

Bran

The outermost layer of the grain kernel, serving as a concentrated source of dietary fiber, vitamins, and minerals.

Germ

The kernel base and embryo where sprouting takes place, serving as a source of vegetable oils and vitamin E.

Enriched Grain Products

Grain products with nutrients added back after being lost during processing.

Empty Kilocalories

Foods or beverages that provide minimal vitamins and minerals, characterized by low nutrient density.

Glucose

A monosaccharide known as blood sugar that is the main provider of energy for the body, produced by plants during photosynthesis.

Galactose

A monosaccharide that exists as a component of the disaccharide lactose.

Fructose

A monosaccharide known as fruit sugar with a sweeter taste than glucose, found in fruits, vegetables, honey, and high-fructose corn syrup.

Maltose

A disaccharide composed of glucose and glucose, formed when starch is broken down in the intestines.

Sucrose

A disaccharide composed of glucose and fructose, found in sugar cane, sugar beets, honey, and maple syrup.

Lactose

A disaccharide composed of galactose and glucose, occurring naturally in animal foods as milk sugar.

Photosynthesis

The process by which plants convert light energy into chemical energy to fuel their metabolism.

Condensation Reaction

A chemical reaction that combines smaller units into a larger one with the release of water, such as joining amino acids to form a protein.

Hydrolysis Reaction

A chemical reaction that splits a larger unit into smaller units through the addition of water, such as digesting starch into simple sugars.

Oligosaccharides

Carbohydrates composed of $3\text{--}10\text{ monosaccharides}$ that are not digested by human enzymes and act as a nutrient source for gut bacteria.

Amylose

A linear, unbranched chain form of starch found in plants.

Amylopectin

A highly branched form of plant starch that is readily broken down by enzymes.

Glycogen

A polysaccharide that functions as the storage form of carbohydrate in animals and humans, stored in the muscle and liver.

Glycogen Loading

A strategy used by athletes (also called carb maxing) to maximize muscle and liver glycogen stores before a major event.

Soluble Fiber

Fibers (such as pectins, gums, and some hemicelluloses) that dissolve in water to form viscous solutions, are broken down by intestinal microflora, and may lower cholesterol.

Insoluble Fiber

Fibers (such as cellulose, some hemicellulose, and lignin) that do not dissolve in water, form plant cell walls, and are found in wheat and rye bran.

Functional Fiber

Isolated or extracted fibers that have beneficial physiological effects in humans.

Lactose Intolerance

A condition resulting from reduced lactase activity, causing undigested lactose to draw water into the large intestine and be metabolized by bacteria into acids and gas.

Glycemic Response

The rate, magnitude, and duration of the rise in blood glucose that occurs after a particular food or meal is consumed.

Glycemic Index

A ranking of how a food affects blood glucose compared to a reference food, with values $>70$ classified as high and $<55$ classified as low.

Glycemic Load

An index of glycemic response that occurs after consuming certain foods, with values of $20\text{ or more}$ classified as high and $<11$ as low.

Insulin

A hormone released in response to high blood glucose that facilitates the uptake and storage of glucose into muscle, liver, and fat-storing cells.

Glucagon

A hormone released in response to low blood glucose that stimulates the breakdown of glycogen to glucose and stimulates gluconeogenesis.

Cellular Respiration

The process where cells convert nutrients into usable energy in the form of ATP according to $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{ATP}$.

Glycolysis

An anaerobic metabolic pathway occurring in the cytoplasm that breaks down $1\text{ glucose}$ into $2\text{ pyruvate}$, $2\text{ ATP}$, and electrons.

Gluconeogenesis

The synthesis of new glucose molecules from pyruvate or oxaloacetate, occurring in the fasting state to keep blood sugar stable.

Ketone Bodies

Molecules formed during fatty acid breakdown when the body lacks carbohydrate to make oxaloacetate in the citric acid cycle; used for energy, excreted in urine, and accumulated in blood.

Type 1 Diabetes

An autoimmune condition accounting for $5\text{--}10\%$ of diagnosed diabetes cases where the immune system destroys insulin-producing cells, typically diagnosed before age $30$.

Type 2 Diabetes

A metabolic disorder accounting for $95\%$ of diagnosed diabetes cases characterized by insulin resistance where cells do not respond properly to insulin.

Gestational Diabetes

A form of diabetes that occurs during pregnancy due to hormonal changes, increasing the risk of fetal complications and later type 2 diabetes.

Reactive Hypoglycemia

Abnormally low blood glucose occurring in response to high carbohydrate consumption due to the overproduction and rapid release of insulin.

Fasting Hypoglycemia

Abnormal insulin secretion not related to food intake, often linked to hormonal deficiencies, tumors, or excess alcohol consumption.

Acceptable Daily Intake (ADI)

An estimate of the amount of a substance that can be safely ingested daily over a human lifetime without health risk.

Aspartame

An alternative sweetener sold commercially as Equal, composed of aspartic acid and phenylalanine, which breaks down when heated.

Phenylketonuria (PKU)

An inherited condition where phenylalanine hydroxylase is unavailable, requiring affected individuals to avoid aspartame because it breaks down into phenylalanine.

Saccharin

An alternative sweetener sold commercially as Sweet'N Low, which was dropped from the list of cancer-causing substances in May 2000 after studies found no link to cancer in humans.

Sucralose

A heat-stable alternative sweetener used in baking and cooking whose chemical name is trichlorogalactosucrose.

Sugar Alcohols

Sweeteners providing minimal energy that can be labeled 'sugar free' or 'no sugar added' and carry the health claim 'does not promote tooth decay.'