final for nutrition

Nutrient density

Measurement of the nutrients in a food compared with the kilocalorie content; nutrient-dense foods are high in nutrients and low in kilocalories.

Energy density

Measurement of the kilocalories in a food compared with the weight (grams) of the food.Energy-dense foods are high in kilocalories but may be low in nutrients.

Estimated Average Requirement (EAR)

Measurement of the kilocalories in a food compared with the weight (grams) of the food.

Recommended Dietary Allowance (RDA)

Recommended daily amount of a nutrient that meets the needs of nearly all individuals (97–98 percent) in a similar age and gender group. The RDA is set higher than the EAR.

Tolerable Upper Limit (UL)

Maximum daily amount of a nutrient considered safe in a group of similar individuals

Adequate Intake (AI)

Approximate daily amount of a nutrient that is sufficient to meet the needs of similar individuals within a population group. The Food and Nutrition Board uses AIs for nutrients that do not have enough scientific evidence to calculate an RDA.

Acceptable Macronutrient Distribution Range (AMDR)

Healthy range of intakes for the energy-containing nutrients—carbohydrates, proteins, and fats—expressed as a percentage of total daily energy. The AMDRs for adults are 45–65 percent carbohydrates, 10–35 percent protein, and 20–35 percent fat

Duodenum

the first and shortest segment of the small intestine, located between the stomach and the jejunum

Jejunum

The middle section of the small intestine, located between the duodenum and ileum, measures about 2.5 meters in adults. Its primary function is the absorption of amino acids, sugars, and fatty acids through specialized villi. It is characterized by its thick, vascular wall and highly active nutrient absorption

Ileum

the final, longest section of the small intestine, roughly 11.5 feet (3.5 meters) long, located in the lower central and right abdominal cavity. It connects the jejunum to the large intestine via the ileocecal valve. Its primary functions are absorbing vitamin \(B_{12}\) and bile salts, and processing remaining nutrients

Cecum

Pouch at the beginning of the large intestine that receives waste from the small intestine.

Ileocecal valve

Sphincter that separates the small intestine from the large intestine

Ascending colon

the first segment of the large intestine, running upward along the right abdomen from the cecum to the right colic flexure. It absorbs water and electrolytes, solidifying waste, and acts as a reservoir before the transverse colon. Key conditions include cancer, colitis, and Crohn’s disease, often diagnosed via colonoscopy and treated through resection.

Transverse colon

is the longest and most movable segment of the large intestine, extending horizontally across the upper abdomen. It absorbs water, salts, and nutrients from waste. Key issues include cancer, Crohn’s disease, and colitis, often causing abdominal pain, constipation/diarrhea, and bloating. Treatment includes surgery, chemotherapy, and lifestyle changes

Descending colon

the part of the large intestine on the left side, extending from the left colic flexure to the iliac crest, where it transitions into the sigmoid colon. It stores and compacts fecal waste, absorbing remaining water and electrolytes. Common diseases like diverticulitis, cancer, and IBD cause symptoms like left-sided pain, diarrhea, and bloody stool, typically diagnosed via colonoscopy or imaging and treated with medication or surgery

Rectum

Final 8-inch portion of the large intestine

Digestion (as distinct from metabolism)

the process that breaks down food into individual molecules small enough to be absorbed through the intestinal wall. it involves both mechanical and chemical processes that occue thought the GI tract

Chemical digestion

Breaking down food through enzymatic reactions.

Mechanical digestion

Breaking down food by chewing, grinding, squeezing, and moving it through the GI tract by peristalsis and segmentation.

Hydrolysis reaction

Chemical reaction that breaks the bond between two molecules with water. A hydroxyl group is added to one molecule and a hydrogen ion is added to the other molecule.

Bolus

soft mass of chewed food

Chyme

Semiliquid, partially digested food mass that leaves the stomach and enters the small intestine.

Pyloric sphincter

a strong, smooth muscle ring at the base of the stomach that acts as a valve, regulating the passage of partially digested food (chyme) into the small intestine (duodenum) while preventing backflow. It ensures food is properly broken down before entering the intestine, with dysfunction causing conditions like constipation, weight loss, and vomiting

Chief cells

Specialized cells in the stomach that secrete pepsinogen, an inactive form of the protein-digesting enzyme pepsin.

Parietal cells

Specialized cells in the stomach that secrete the gastric juices hydrochloric acid and intrinsic factor

Pepsinogen

Inactive protease secreted by the chief cells in the stomach; it is converted to the active enzyme pepsin in the presence of HCl.

Intrinsic factor

Glycoprotein secreted by the stomach that facilitates the absorption of vitamin B12

Bile

Secretion produced by the liver, stored in the gallbladder, and released into the duodenum to emulsify dietary fat, facilitating their digestion and absorption

Hydrochloric acid (HCl)

Strong acid produced in the stomach that aids in digestion

Circular folds

are permanent, deep ridges in the mucosa and submucosa of the small intestine. They increase surface area for nutrient absorption, slow the movement of chyme, and force it to spiral through the intestine

Villi

Small, fingerlike projections that line the lumen of the small intestine, playing a crucial role in nutrient absorption

Microvilli

Tiny projections on the villi in the small intestine

Enterocyte

specialized absorptive epithelial cells that line the lumen of the small intestine playing a crucial role in nutrient absorption

Enzymes:

are proteins that act as catalysts in living cells, facilitating and speeding up chemical reactions without being consumed in the process

Salivary amylase

Digestive enzyme that begins breaking down carbohydrate (starch) in the mouth; other important enzymes during carbohydrate digestion include pancreatic amylase, maltase, sucrase, and lactase

Gastric lipase

an acidic enzyme secreted by the chief cells in the stomach fundus, encoded by the LIPF gene. It initiates fat digestion by breaking down 10%–30% of triglycerides into fatty acids and diglycerides, working optimally at an acidic pH, which aids in processing human milk fat in infants.

Pepsinogen

Inactive protease secreted by the chief cells in the stomach; it is converted to the active enzyme pepsin in the presence of HCl.

Pepsin

Active protease that begins the digestion of proteins in the stomach.

Trypsinogen

an inactive proenzyme (zymogen) produced in the pancreas and secreted into the small intestine, where it is activated by enteropeptidase to form trypsin, a protease crucial for protein digestion. It acts as a safety mechanism, preventing autodigestion of the pancreas; premature activation inside the pancreas can cause pancreatitis

Trypsin

a serine protease enzyme, produced as inactive trypsinogen in the pancreas and activated in the small intestine, that functions to break down proteins by cleaving peptide chains at lysine and arginine residues. It is crucial for digestion, protein analysis in research, and clinical applications as an anti-inflammatory agent and in wound care

Chymotrypsinogen

an inactive proenzyme (zymogen) synthesized in the pancreatic acinar cells and secreted into the small intestine, where it is activated by trypsin into chymotrypsin. It consists of 245 amino acid residues and acts as a protease that breaks down dietary proteins into smaller peptides

Chymotrypsin

a serine endopeptidase enzyme produced in the pancreas that breaks down proteins in the small intestine, specifically cleaving peptide bonds on the carboxyl side of aromatic amino acids (tyrosine, phenylalanine, tryptophan). It is used medically as an anti-inflammatory agent, to treat wounds, and for eye surgery

Procarboxypeptidase

the inactive, zymogen precursor of the digestive enzyme carboxypeptidase, secreted by the pancreatic acinar cells. Activated in the small intestine, primarily by trypsin, it is crucial for protein digestion by removing carboxyl-terminal amino acids. It exists in forms A and B and is also crucial in managing inflammation and fibrinolysis.

Carboxypeptidase

enzymes (specifically metallo-exopeptidases) that catalyze the hydrolysis of peptide bonds, releasing single amino acids from the C-terminal end of proteins and peptides. Produced primarily in the pancreas as proenzymes (procarboxypeptidases A and B), they are activated in the small intestine to complete protein digestion. They play crucial roles in protein degradation, regulatory processes, and blood pressure control

Pancreatic amylase

a digestive enzyme produced by the pancreas to break down complex carbohydrates into simple sugars. Elevated serum amylase typically indicates acute pancreatitis, often accompanied by severe abdominal pain, nausea, and vomiting. Normal serum amylase generally ranges from 30 to 110 U/L, though ranges vary by laboratory

Pancreatic lipase

a crucial digestive enzyme secreted by the pancreas into the small intestine, where it acts alongside bile salts to break down dietary fats (triglycerides) into monoglycerides and fatty acids. It is essential for fat digestion and absorption, with its deficiency causing malabsorption. Elevated serum levels often indicate pancreatic conditions like acute pancreatitis

Sucrase

is a crucial digestive enzyme, primarily found on the intestinal villi (brush border), that hydrolyzes sucrose (table sugar) into the simple sugars glucose and fructose for absorption. It acts as part of the sucrase-isomaltase complex, with deficiency causing severe gastrointestinal symptoms. It is often called invertase

Maltase

is an essential enzyme that breaks down the disaccharide maltose into two glucose molecules, facilitating carbohydrate digestion and energy production. It is found primarily in the small intestine (maltase-glucoamylase) and within cells (acid alpha-glucosidase), playing a key role in breaking down starches and glycogen

Lactase

is an enzyme produced in the small intestine that breaks down milk sugar (lactose) into simple sugars (glucose and galactose) for digestion. It is used to treat lactase deficiency (lactose intolerance), reducing symptoms like gas, bloating, and diarrhea. Lactase supplements (capsules/tablets) are taken with the first bite of dairy

Dipeptidase

is an enzyme, specifically a brush border enzyme in the small intestine, that catalyzes the hydrolysis of dipeptides into two individual amino acids. It plays a crucial role in final protein digestion, converting small peptides into absorbable nutrients.

Tripeptidase

an enzyme that catalyzes the hydrolysis of tripeptides, specifically breaking them into a dipeptide and a single amino acid. It acts as a metalloenzyme, often removing the N-terminal amino acid from tripeptide substrates, playing a crucial role in protein catabolism and nutrient absorption, particularly in bacteria and the small intestine

Salivary glands

Cluster of glands located underneath and behind the tongue that release saliva in response to the sight, smell, and taste of food.

Liver

Accessory organ of digestion located in the upper abdomen and responsible for the synthesis of bile, the processing of nutrients, the metabolism of alcohol, and other functions.

Gallbladder

Pear-shaped organ that stores and concentrates bile produced by the liver and secretes it through the common bile duct into the small intestine.

Pancreas

Large gland located behind the stomach that releases digestive enzymes and bicarbonate after a meal. Also secretes the hormones insulin and glucagon, which control blood glucose.

Disaccharides

Simple sugar that consists of two sugar units combined. The three most common disaccharides are sucrose, lactose, and maltose.

Sucrose

glucose and fructose

Maltose

glucose and glucose

Lactose

glucose and galactose

Monosaccharides

Simple sugar that consists of a single sugar unit. The three most common monosaccharides are glucose, fructose, and galactose, which are crucuail roles in energy metabolism and are absorbed directly into the bloodstream during digestion

Glucose

primary monosaccharide and primary energy source for the body.playing a crucial role in various meatbolic processes

Galactose

Monosaccharide that links with glucose to create the disaccharide found in dairy foods.

Fructose

Sweetest of all the monosaccharides; also known as fruit sugar or levulose

Starch

Storage form of glucose in plants.

Amylose

Straight chain of polysaccharides found in starch.

Amylopectin

Branched chain of polysaccharides found in starch

Glycogen

Storage form of glucose in animals, including humans, primary found in the liver and muscle cells. it plays a crucial role in energy metabolism providing a source of glucose when needed

Insoluble fiber

Type of fiber that isn’t dissolved in water or fermented by intestinal bacteria

Soluble fiber

Type of fiber that dissolves in water and is fermented by intestinal bacteria. Many soluble fibers are viscous and have thickening properties

Whole grains

Grain foods that are made with the entire edible grain kernel: the bran, the endosperm, and the germ

Bran

Indigestible outer shell of the grain kernel

Germ

Vitamin-rich embryo, or seed, of a grain

Endosperm

Starchy inner portion of a cereal grain

Glycemic index

Rating scale of the likelihood of foods to increase the levels of blood glucose and insulin.

Amino acids

Fundamental units of proteins; composed of carbon, hydrogen, oxygen, and nitrogen.

Triglycerides

Type of lipid commonly found in foods and the body; also known as fat. Triglycerides consist of three fatty acids attached to a glycerol backbone

Phospholipids

Category of lipids that consists of two fatty acids and a phosphate group attached to a glycerol backbone. Lecithin is an example of a phospholipid found in food and in the body

Fatty acids

Most basic unit of triglycerides and phospholipids; fatty acids consist of carbon chains ranging from 2 to 80 carbons in length

Saturated fatty acid

Fatty acid in which all of the carbons are bound with hydrogen.

Monounsaturated (MUFA)

Fatty acid that has one double bond.

Polyunsaturated (PUFA)

Fatty acid with two or more double bonds

Omega-3 fatty acids

Family of polyunsaturated fatty acids with the first double bond located at the third carbon from the omega end

Omega-6 fatty acids

Family of polyunsaturated fatty acids with the first double bond located at the sixth carbon from the omega end

cis fatty acids

Configuration of a fatty acid in which the carbon atoms on each side of the double bond are on the same side

trans fatty acids

Configuration of a fatty acid in which the carbon atoms are on opposite sides of the double bond

Sterols

Category of lipids that contains four connecting rings of carbon and hydrogen. Cholesterol is the most common sterol

ATP

High-energy molecule composed of adenine, ribose, and three phosphate molecules; used by cells to fuel all biological processes.

Glycogenesis

Process of assembling excess glucose into glycogen in the liver and muscle cells

Insulin

Hormone secreted from the beta cells of the pancreas that stimulates the uptake of glucose from the blood into the cells

Glucagon

Hormone secreted from the alpha cells of the pancreas that stimulates glycogenolysis and gluconeogenesis to increase blood levels of glucose

Lipogenesis

Process that converts excess glucose into fat for storage

Lipolysis

the metabolic process of breaking down stored triglycerides into free fatty acids and glycerol for energy, primarily triggered by hormones like epinephrine and low insulin during fasting or exercise. It is also a non-surgical cosmetic procedure designed to contour the body by reducing small, localized fat deposits using methods like cold, laser, or injection

Glycogenolysis

Hydrolysis of glycogen to release glucose

Gluconeogenesis

Creation of glucose from noncarbohydrate sources, predominantly protein

Glycolysis

Breakdown of glucose; for each molecule of glucose, two molecules of pyruvate and two ATP molecules are produced.

Dysbiosis

a microbial imbalance in the body—often the gut—characterized by a loss of beneficial bacteria, an increase in harmful bacteria, or reduced microbial diversity. Common symptoms include bloating, abdominal pain, and diarrhea. It is primarily caused by poor diet, antibiotic overuse, and chronic stress. Treatment involves dietary changes, probiotics, and addressing underlying causes

Probiotics

Live microorganisms that, when consumed in adequate amounts, confer a health benefit on the host

Prebiotics

Nondigestible starch found in plant foods that promotes the growth and health of your GI flora

Insulin resistance

Inability of the cells to respond to insulin

Peptide

Chain of amino acids