Chapter 3: Digestion, Absorbtion, and Metabolism

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Class

Atoms

Smallest unit of an element

Element

Cannot be broken down into products with different properties.

GI tract

Mouth, pharynx, esophagus, stomach, small and large intestines,

Transit time

The time between the ingestion and elimination of food waste.

Enzymes

Protein molecules that a accelerate the rate of specific chemical reactions without being changed themselves.

Pepsin (stomach)

Breaks proteins into polypeptides and AA. Secreted in gastric juice in inactive form and activated by acid in stomach.

Trypsin and chymotrypsin (pancreas)

Breaks proteins and polypeptides into shorter polypeptides.

Carboxypeptidase

Breaks polypeptides into AA.

Sucrase

Breaks sucrose into glucose and fructose

Lactase

Breaks lactose into glucose and galactose

Maltase

Breaks maltose into glucose

Antigen

A foreign substance that simulates an immune response:

Antibodies

Proteins produced by cells that destroy or inactivate foreign substances.

Saliva

Secreted by salivary glands.

Salivary amylase

Enzyme that breaks down starch.

Lysozyme

Enzyme in salvia, tears, and sweat that destroys certain types of bacteria.

Epiglottis

Piece of elastic connective tissue at the back of throat that covers the openings of passageway to the lungs during swallowing.

Esophagus

Extends from the pharynx to the stomach.

Peristalsis

Muscular contractions that move food through the GI tract.

Sphincter

Muscular valve that controls the flow of materials in the GI tract

Chyme

Mixture of partially digested food and stomach secretions.

Gastric juice

Composed partly of hydrochloric acid

Parietal cells

Cells in the stomach lining in gastric pits, makes hydrochloric acid and intrinsic factor in response to nervous or hormonal stimulation.

Pepsinogen

An inactive protein-digesting enzyme produced by gastric glands and activated to pepsin by acid in the stomach.

Pepic ulcer

Open sore in lining of stomach, esophagus, or small intestine. Leading cause of ulcer is Helicobacter pylori bacteria.

Gastrin

Hormone secreted by stomach mucosa that stimulates the secretion of gastric juice.

Pyloric phincter

Helps regulate the rate at which food empties the stomach.

Villi (villus)

Finger-like protrusions of he lining of he small intestine that participate in absorption of nutrients. Each contains a lacteal.

Microvilli or brushborder

Increase the absorptive surface area in the small intestine.

Lacteal

A lymph vessel in intestine that absorbs and transports the products of fat digestion.

Segmentation

Rhythmic local constrictions of he intestine that mix food and digestive juices and speeds absorption by moving food mass over intestine wall.

Pancreas

Secretes digestive enzymes and bicarbonate ions into small intestine during digestion. The bicarbonate ions neutralize chyme making the environment in small intestine less acidic then stomach.

Gallbladder

Organ that stores bile, which is produced by liver.

Lipases

Fat-digesting enzymes

Bile

Made by liver and stored by gallbladder. Emulsifies fat allowing lipases to be more effective on fat.

Secretin

Hormone released by the duodenum that signals the release of pancreatic juice rich in bicarbonate ions and stimulates the liver to secrete bile into gallbladder

Cholecystokinin (CCK)

Hormone released by the duodenum that stimulates the release of pancreatic juice rich in digestive enzymes and causes the gallbladder to contract and release bile into duodenum.

Colon

Largest portion of large intestine.

Rectum

Connects colon to anus.

Intestinal microflora

Microorganisms that inhabit the large intestine.

Gastroesophageal reflux disease (GERD)

Chronic condition in which acidic acid stomach contents leak back up into the esophagus damaging it and causing pain.

Enteral

Method of liquid feeding by placing tube down I stomach or intestines.

Total parenteral nutrition (TPN)

Providing nutrients directly into circulatory system.

Atrophic gastritis

Inflammation on stomach lining that may decrease absorption of vitamins and minerals and may allow bacterial growth.

Hepatic portal circulation

System of blood vessels that collect nutrient-laden from digestive organs and delivers it to liver.

Lymphatic system

System that drains excess fluids from spaces between cells, transports fat-soluble substances from digestive tract.

Capillaries

Where exchange of gases and nutrients between blood and cells occur.

Veins

Carry blood towards the heart.

Arteries

Carry blood away from the heart.

Metabolic pathway

Series of chemical reactions inside of an organism that results in the transformation of one molecule into another.

Coenzyme

A molecule (not protein but sometimes a vitamin) that is necessary for the proper functioning of many enzymes.

Cellular respiration

The reactions that break down glucose, fatty acids, and amino acids in the presence of oxygen to produce carbon dioxide,water, and energy in the form of ATP.

Aceyl CoA

Metabolic intermediate formed during the breakdown of glucose, fatty acids, and AA. It is a 2-carbon compound attached to a molecule of CoA.

Citric acid cycle (krebs cycle or tricarboxylic acid cycle)

Stage in cellular respiration where 2 carbons from acetyl-CoA are oxidized. Producing 2 molecules of carbon dioxide.

Oxidized

Lost an electron

Reduced

Substance gained an electron.

Glycogen

Storage form of carbohydrate.

Nephron

Functional unit of kidney. Performs the job of filtering blood and maintaining fluid balance.

Glomerulus

Ball of capillaries in nephron that filters blood during urine formation.

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