DigestiveSystem – Chemical ReactionsChemical reactions involve the rearranging of theconstituent atoms to create different substances. There are 6 clues to tell ifa chemical reaction has formed. Normally chemical reactions will displayseveral of these qualities: an insolubleprecipitate is formed, bubbles are formed, color change is observed, new odoris produced, temperature change, light is produced. Compounds that react witheach other are called reactants, compounds produced are called products andproducts that are solids are called precipitates. Subscripts are used to balancea compound in a reaction, while coefficients are used to balance the entireequation in order to satisfy the Law of Conservation of Mass. The process ofdigestion is the act of converting food into chemical substances that the bodycan absorb into the blood stream to be utilized by body tissue.
This happenswhen proteins, lipids, carbohydrates are broken down into simpler compounds forthe human body to process (“Digestive System,” n.d.). Food begins the digestivejourney as soon as it is ingested. It ismasticated (chewed up) in the mouth then swallowed and pushed down theesophagus with the help of peristaltic contractions.
The stomach breaks up thebolus chemically and mechanically. The nutrients in chyme is then absorbed inthe small intestine, after which it travels through the large intestine and tothe anus to be excreted. (“Enzymatic digestion,” n.d.) Digestion starts in themouth where food is masticated (chewed) into smaller pieces.
Saliva is rich inamylase, a salivary enzyme that break down carbohydrates turning them intomaltose, maltotriose and dextrins. (“How Is Starch Changed by the Saliva in theMouth?” n.d.). The enzyme coats each starch molecule, and deconstructs itthrough hydrolysis to turn them into smaller, more manageable pieces. Thisseparation of long chained starches into sugars makes it easier to break downlater in the body. The esophagus is a muscular tube, roughly 8 inches inlength, that is lined with a layer of pink tissue called mucosa. It connectsthe pharynx to the stomach and transports the bolus of food away from themouth.
Automated muscle contractions,peristalsis, pushes food along the tube. There are sphincters located at bothends of the esophagus, which open and close after swallowing, when food isabout to enter the stomach or when gas needs to be expelled. (“NormalFunction,” n.d.).
The stomach is where the majority of digestion takes place.Chemical and mechanical forces break down the bolus and prepare it for furtherdigestion in the small intestine. Gastric juice, comprised of hydrochloricacid, water, electrolytes, mucus and an intrinsic factor, is responsible forthe digestion of proteins and fats. The enzymes pepsin and protease, secretedby stomach lining, breaks down proteins, converting them to peptides which arefurther digested by gastric lipase. These stomach enzymes uncoil proteinsstrands as part of digestion. Trypsin breaks down protein strands into one twoor three amino acids. (“What Digests First, Protein, Carbohydrates or Fat?”n.d.
). Hydrochloric acid secreted by parietal cells converts pepsinogen intopepsin and breaks down various nutrients in food. It also kills more bacteriain food with its high acidity.
Unlike intramolecular forces which hold a singlemolecule together, intermolecular forces are responsible for the attractionbetween compounds. There are 3 types of intermolecular forces; Londondispersion forces, dipole-dipole forces and hydrogen bonding (Meyers, n.d.).
Londondispersion forces- a temporary force of attraction that occurs due to constantshifting of electrons in opposite molecules. This force is the weakest out of the three and occurs between allmolecules, regardless of whether they are polar or not. Dipole-dipole forces- apermanent force of attraction between the positive end of one polar moleculeand the negative end of another polar molecule. Hydrogen bonding- the strongestforce of attraction that can occur between two molecules. Hydrogen bondingoccurs between a slightly positive hydrogen on one molecule and a slightlynegative atom on another molecule. The reason this bonding type is so strong isbecause the atomic radius of hydrogen is very small, allowing other atoms tocome extremely close, however this only happens when hydrogen bonds withfluorine, oxygen or nitrogen. HCl(aq) is a polar molecular.
Holdingthe molecule together is London dispersion forces and dipole-dipole forces asthe positive ends of each molecule attracts the negative ends. This force ispermanent and stronger than London dispersion forces which are only temporaryattractions due to shifting (B, n.d.) Hydrochloric acid is extremely acidicwith a pH of about 2. Our stomach lining is protected by a thick layer ofmucus, however gastric acid can burn through flesh and metals. Sodiumbicarbonate (NaHCO3), secreted by the pancreas, is a weak base with a pH ofabout 8.4. It neutralizes gastric acid and is found in common foods.
An exampleof a neutralization reaction that will occur in the stomach as a result ofgastric acid coming into contact with the bodies natural antacid is: HCL(aq) + NaHCO3(aq) ? NaCl(aq) + H2O(l) + CO2(g)Hydrochloric acid plus sodium bicarbonate yields sodiumchloride, water and carbon dioxide. This double displacement and neutralizationreaction does occur as a gas and water are produced (gas, water or precipitatemust be a product of double displacement reaction for it to occur). There are 5types of chemical reactions: synthesis, decomposition, single displacement,double displacement and combustion. Double displacement reactions are achemical reaction in which the positive ions of two ionic compounds switchplaces to form two new ionic compounds. They must always produce either asolid, water or gas for a reaction to occur. Neutralization reactions are atype of double displacement reaction in which an acid reacts with a base toproduce an ionic compound (salt) and water. Acid base reactions in the stomachare examples of neutralization reactions such as when hydrochloric acid reactswith sodium bicarbonate.
Alongside the main GI tract, are other organs thathelp to digest food and filter out nutrients from waste. The liver filters toxinsout of the blood and produces bile which is used to further digestion. Thegallbladder stores bile from the liver and holds it until it is needed. Thepancreas secrets enzymes used in the small intestine necessary for digestion.It also makes hormones that regulate the glucose levels in the blood (“Anatomyof the Liver, Gallbladder & Pancreas,” n.d.
). The liver is a roughlytriangular organ, capable of regenerating itself. It is divided up into 4 distinct lobes; theleft, right, caudate, and quadrate lobes. The liver plays an important role indigestion with the production of bile. Bile is a mixture of water, bile salts,cholesterol and bilirubin. It is able to emulsify large quantities of fat andbreak them up into smaller pieces, that are easier to digest (“Liver – Anatomyand Function of the Human Liver,” n.d.
). Detoxification of blood also occurs inthe liver when blood passes through the hepatic portal. Hepatocytescontinuously monitor and eliminate toxins such as alcohol and drugs. The gallbladderis a small, green sac located under the liver that stores bile.
The absorbentlining of the gallbladder makes it ideal for collecting excess amounts of bileuntil it is needed for digestion. When food enters the small intestine ahormone called cholecystokinin triggers the bile ducts leading out thegallbladder to open and deliver bile. The secreted bile helps to break up fatsand drain waste products from the liver and excrete them (“GallbladderFunction, Location & Anatomy,” 2014). The pancreas is an organ located inthe abdomen that is responsible for converting digested food into fuel forcells. It has two main functions, aid digestion (exocrine) and regulate bloodsugar (endocrine). Exocrine function: the pancreas produces vital enzymes toaid digestion such as trypsin and chymotrypsin to breakdown proteins, amylasefor carbohydrates and lipase to break down fats.
These juices enter the firstpart of the small intestine (duodenum). In addition, bile from the liver tohelp digest fats, proteins and starches (“The Pancreas Center,” n.d.
). Most ofthe process of digestion in the gastroenterological tract occurs in the smallintestine. It is roughly 7.0 m long and is divided into three sections: theduodenum, jejunum, and ileum.
The small intestine breaks down and absorbsvarious nutrients from chyme and transports it throughout the body. Villi (finger like extensions on the smallintestine wall) absorb passing nutrients and send it off to the blood streamand other tissues (“Digestive System,” 2014). Most digestive enzymes enter thesmall intestine through the pancreatic duct. Proteolytic enzymes, includingtrypsin and chymotrypsin rip apart proteins into smaller peptides. Duodenum –This is the first part of the small intestine as well as the shortest. It dealswith partially digested chyme from the stomach and plays a vital role indigestion. Chemical secretions from the liver, pancreas and gallbladder bringin enzymes to facilitate chemical digestion. The muscular walls of the duodenumare lined with mucosa and epithelial tissue and microvilli to increase surfacearea for absorption.
Bile produced inthe liver and stored in the gallbladder emulsifies lipids, breaking them intoglobular pieces to increase surface area (“Duodenum – Small Intestine,”n.d.). There are three main enzymessecreted by the pancreas that work in the duodenum, one being trypsin. As aproteolytic enzyme (protein digesting enzyme), trypsin’s main function is tobreak the bonds of specific amino acids to produce peptides (“Trypsin,” n.d.).
It also makes the absorption of vitaminB12 an easier task. The combination ofthe slightly alkaline environment of pH 8 optimizes efficiency of the enzyme. Trypsincatalyzes the hydrolysis of peptide bonds, breaking down proteins into smallerpieces (“Trypsin,” 2018). Dipeptide + H2O -> 2 Amino AcidsHydrolysis: a double displacement reaction involving waterin which the H2O molecule cleaves in half another molecule. Consequently, onehalf of the molecule gets a H+ ion while the other half has the OH- ion. Inbiochemistry hydrolysis is used to break down polymers into monomers. Foodingested takes the form of a polymer which is digested by enzymes who’sreactions are sped up using hydrolysis.
Monomers produced are small enough forthe body absorb (“Structural Biochemistry/Enzyme CatalyticMechanism/Hydrolysis,” n.d.).
A periodic trend that describes the tendency ofan atom to attract a bonding pair of atoms. Each atom on the periodic table hasan electronegativity value (EN). The difference in EN in a bond can be used topredict the type of bond it will form. Covalent bonds share electrons, so theEN difference would be smaller, whereas ionic bonds that transfer electronsshould have a high EN difference. There are 3 criteria that must be meet inorder for a chemical reaction to occur.
Reactants must: collide, collide with proper orientation, collide withenough energy. Things that can speed upa reaction include: a catalyst, increase in temperature, stirring, increasingsurface area and more. H2O is a covalent compound as it has an EN of 1.5 makingit a polar covalent molecule. Water has all three types of intermolecularforces, London dispersion, dipole-dipole and hydrogen bonding, with thestrongest and most prevalent being the latter. Water has a pH of 7 making itsafe to consume due to its unreactive nature.
With the proper orientation andspeed, the collision theory allows for two oxygen molecules to bond when thenegative dipole meets the positive side. Jejunum – The middle segment of thesmall intestine. With epithelial cellsand layers of villi along folded inner walls, the jejunum is responsible forthe majority of nutrient absorption in the digestive system. After passing through this section of thesmall intestine, more than 90% of all nutritional content has been absorbedinto the body. Ileum- At 3.
5m long,the Ileum is the longest and final segment in the small intestine. Its primaryfunction is to absorb vitaminB12 and reabsorb conjugated bile salts. The innerwall is smoother than previous sections and has slower peristalticcontractions, in addition to being less permeable. To prepare food for excretion,there are patches of lymphatic tissue designed to detect and extract vitaminB12(“Ileum,” 2015). The large intestine is a 1.8m long tube that prepares food forexcretion. It is broken up into four parts: the ascending colon, the transversecolon, the descending colon and the sigmoid colon. First, water and salts areremoved from the waste as it passes through the colon during a period of 36hours.
The waste makes its way to the sigmoid where it is stored untildefecation (“Large Intestine – Anatomy and Physiology,” n.d.).
Like the smallintestine, the colon is made up of four layers of tissue, each coated withvilli, mucosa or epithelial cells to remove any final nutrients. A variety ofbacteria is mixed with with the chyme to begin turning it into feces. Bacterialfermentation releases vitamins K, B1, B2, B6, B12, and biotin, as well ascreates flatulence (gas) from the methane and carbon dioxide in the bowel(Bradford, 2016).
The rectum is the last part of the digestive system rightbefore the anus and is about 10cm-15cm long. It’s function is to temporarilystore feces. The muscular pouch holding excrement is able to expand toaccommodate more waste.
When waste is about to be expelled, the internalsphincter relaxes and involuntary and voluntary muscle contractions beginworking (“Rectum Anatomy, Diagram & Function,” 2015). UltrasoundTechnician – An ultrasound technician operates equipment that uses highfrequency sound waves to create images of a patients internal organs. The workdone helps doctors make decisions on patient treatment, based on anyabnormalities present in the imagery. Theses technicians work directly withpatients and doctors and can specialize in fields such as obstetric andgynecologic, abdominal, breast, vascular, or cardiac sonography (McKay, n.d.).
Gastroenterologist– A physician with dedicated training and experience who has studied in themanagement of diseases of the gastrointestinal tract and liver. These doctorscan treat a variety of conditions from Hepatitis C to irritable bowel syndrome(IBS). There are various fields of study, as some physicians may choose tospecialize in hepatology, transplantation or other (“What Is aGastroenterologist,” n.d.
). They may perform endoscopic procedures in whichspecial instruments are used to view ones GI tract. Gastroenterologists do notperform surgery however, they can work alongside a GI surgeon or providetreatment and advice to patients.