Digestive other are called reactants, compounds produced are called


System – Chemical Reactions

Chemical reactions involve the rearranging of the
constituent atoms to create different substances. There are 6 clues to tell if
a chemical reaction has formed. Normally chemical reactions will display
several of these qualities:  an insoluble
precipitate is formed, bubbles are formed, color change is observed, new odor
is produced, temperature change, light is produced. Compounds that react with
each other are called reactants, compounds produced are called products and
products that are solids are called precipitates. Subscripts are used to balance
a compound in a reaction, while coefficients are used to balance the entire
equation in order to satisfy the Law of Conservation of Mass. The process of
digestion is the act of converting food into chemical substances that the body
can absorb into the blood stream to be utilized by body tissue. This happens
when proteins, lipids, carbohydrates are broken down into simpler compounds for
the human body to process (“Digestive System,” n.d.). Food begins the digestive
journey as soon as it is ingested.  It is
masticated (chewed up) in the mouth then swallowed and pushed down the
esophagus with the help of peristaltic contractions. The stomach breaks up the
bolus chemically and mechanically. The nutrients in chyme is then absorbed in
the small intestine, after which it travels through the large intestine and to
the anus to be excreted. (“Enzymatic digestion,” n.d.) Digestion starts in the
mouth where food is masticated (chewed) into smaller pieces. Saliva is rich in
amylase, a salivary enzyme that break down carbohydrates turning them into
maltose, maltotriose and dextrins. (“How Is Starch Changed by the Saliva in the
Mouth?” n.d.). The enzyme coats each starch molecule, and deconstructs it
through hydrolysis to turn them into smaller, more manageable pieces. This
separation of long chained starches into sugars makes it easier to break down
later in the body. The esophagus is a muscular tube, roughly 8 inches in
length, that is lined with a layer of pink tissue called mucosa. It connects
the pharynx to the stomach and transports the bolus of food away from the
mouth.  Automated muscle contractions,
peristalsis, pushes food along the tube. There are sphincters located at both
ends of the esophagus, which open and close after swallowing, when food is
about to enter the stomach or when gas needs to be expelled. (“Normal
Function,” n.d.). The stomach is where the majority of digestion takes place.
Chemical and mechanical forces break down the bolus and prepare it for further
digestion in the small intestine. Gastric juice, comprised of hydrochloric
acid, water, electrolytes, mucus and an intrinsic factor, is responsible for
the digestion of proteins and fats. The enzymes pepsin and protease, secreted
by stomach lining, breaks down proteins, converting them to peptides which are
further digested by gastric lipase. These stomach enzymes uncoil proteins
strands as part of digestion. Trypsin breaks down protein strands into one two
or three amino acids. (“What Digests First, Protein, Carbohydrates or Fat?”
n.d.). Hydrochloric acid secreted by parietal cells converts pepsinogen into
pepsin and breaks down various nutrients in food. It also kills more bacteria
in food with its high acidity. Unlike intramolecular forces which hold a single
molecule together, intermolecular forces are responsible for the attraction
between compounds. There are 3 types of intermolecular forces; London
dispersion forces, dipole-dipole forces and hydrogen bonding (Meyers, n.d.). London
dispersion forces- a temporary force of attraction that occurs due to constant
shifting of electrons in opposite molecules. 
This force is the weakest out of the three and occurs between all
molecules, regardless of whether they are polar or not. Dipole-dipole forces- a
permanent force of attraction between the positive end of one polar molecule
and the negative end of another polar molecule. Hydrogen bonding- the strongest
force of attraction that can occur between two molecules. Hydrogen bonding
occurs between a slightly positive hydrogen on one molecule and a slightly
negative atom on another molecule. The reason this bonding type is so strong is
because the atomic radius of hydrogen is very small, allowing other atoms to
come extremely close, however this only happens when hydrogen bonds with
fluorine, oxygen or nitrogen. HCl(aq) is a polar molecular. Holding
the molecule together is London dispersion forces and dipole-dipole forces as
the positive ends of each molecule attracts the negative ends. This force is
permanent and stronger than London dispersion forces which are only temporary
attractions due to shifting (B, n.d.) Hydrochloric acid is extremely acidic
with a pH of about 2. Our stomach lining is protected by a thick layer of
mucus, however gastric acid can burn through flesh and metals. Sodium
bicarbonate (NaHCO3), secreted by the pancreas, is a weak base with a pH of
about 8.4. It neutralizes gastric acid and is found in common foods. An example
of a neutralization reaction that will occur in the stomach as a result of
gastric acid coming into contact with the bodies natural antacid is:

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HCL(aq) + NaHCO3(aq) ? NaCl(aq) + H2O(l) + CO2(g)

Hydrochloric acid plus sodium bicarbonate yields sodium
chloride, water and carbon dioxide. This double displacement and neutralization
reaction does occur as a gas and water are produced (gas, water or precipitate
must be a product of double displacement reaction for it to occur). There are 5
types of chemical reactions: synthesis, decomposition, single displacement,
double displacement and combustion. Double displacement reactions are a
chemical reaction in which the positive ions of two ionic compounds switch
places to form two new ionic compounds. They must always produce either a
solid, water or gas for a reaction to occur. Neutralization reactions are a
type of double displacement reaction in which an acid reacts with a base to
produce an ionic compound (salt) and water. Acid base reactions in the stomach
are examples of neutralization reactions such as when hydrochloric acid reacts
with sodium bicarbonate. Alongside the main GI tract, are other organs that
help to digest food and filter out nutrients from waste. The liver filters toxins
out of the blood and produces bile which is used to further digestion. The
gallbladder stores bile from the liver and holds it until it is needed. The
pancreas secrets enzymes used in the small intestine necessary for digestion.
It also makes hormones that regulate the glucose levels in the blood (“Anatomy
of the Liver, Gallbladder & Pancreas,” n.d.). The liver is a roughly
triangular organ, capable of regenerating itself.  It is divided up into 4 distinct lobes; the
left, right, caudate, and quadrate lobes. The liver plays an important role in
digestion 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 and
break them up into smaller pieces, that are easier to digest (“Liver – Anatomy
and Function of the Human Liver,” n.d.). Detoxification of blood also occurs in
the liver when blood passes through the hepatic portal. Hepatocytes
continuously monitor and eliminate toxins such as alcohol and drugs. The gallbladder
is a small, green sac located under the liver that stores bile. The absorbent
lining of the gallbladder makes it ideal for collecting excess amounts of bile
until it is needed for digestion. When food enters the small intestine a
hormone called cholecystokinin triggers the bile ducts leading out the
gallbladder to open and deliver bile. The secreted bile helps to break up fats
and drain waste products from the liver and excrete them (“Gallbladder
Function, Location & Anatomy,” 2014). The pancreas is an organ located in
the abdomen that is responsible for converting digested food into fuel for
cells. It has two main functions, aid digestion (exocrine) and regulate blood
sugar (endocrine). Exocrine function: the pancreas produces vital enzymes to
aid digestion such as trypsin and chymotrypsin to breakdown proteins, amylase
for carbohydrates and lipase to break down fats. These juices enter the first
part of the small intestine (duodenum). In addition, bile from the liver to
help digest fats, proteins and starches (“The Pancreas Center,” n.d.). Most of
the process of digestion in the gastroenterological tract occurs in the small
intestine. It is roughly 7.0 m long and is divided into three sections: the
duodenum, jejunum, and ileum. The small intestine breaks down and absorbs
various nutrients from chyme and transports it throughout the body.  Villi (finger like extensions on the small
intestine wall) absorb passing nutrients and send it off to the blood stream
and other tissues (“Digestive System,” 2014). Most digestive enzymes enter the
small intestine through the pancreatic duct. Proteolytic enzymes, including
trypsin and chymotrypsin rip apart proteins into smaller peptides. Duodenum –
This is the first part of the small intestine as well as the shortest. It deals
with partially digested chyme from the stomach and plays a vital role in
digestion. Chemical secretions from the liver, pancreas and gallbladder bring
in enzymes to facilitate chemical digestion. The muscular walls of the duodenum
are lined with mucosa and epithelial tissue and microvilli to increase surface
area for absorption.  Bile produced in
the liver and stored in the gallbladder emulsifies lipids, breaking them into
globular pieces to increase surface area (“Duodenum – Small Intestine,”
n.d.).  There are three main enzymes
secreted by the pancreas that work in the duodenum, one being trypsin. As a
proteolytic enzyme (protein digesting enzyme), trypsin’s main function is to
break the bonds of specific amino acids to produce peptides (“Trypsin,” n.d.).
It also makes the absorption of vitaminB12 an easier task. The combination of
the slightly alkaline environment of pH 8 optimizes efficiency of the enzyme. Trypsin
catalyzes the hydrolysis of peptide bonds, breaking down proteins into smaller
pieces (“Trypsin,” 2018). 


Dipeptide + H2O -> 2 Amino Acids

Hydrolysis: a double displacement reaction involving water
in which the H2O molecule cleaves in half another molecule. Consequently, one
half of the molecule gets a H+ ion while the other half has the OH- ion. In
biochemistry hydrolysis is used to break down polymers into monomers. Food
ingested takes the form of a polymer which is digested by enzymes who’s
reactions are sped up using hydrolysis. Monomers produced are small enough for
the body absorb (“Structural Biochemistry/Enzyme Catalytic
Mechanism/Hydrolysis,” n.d.). A periodic trend that describes the tendency of
an atom to attract a bonding pair of atoms. Each atom on the periodic table has
an electronegativity value (EN). The difference in EN in a bond can be used to
predict the type of bond it will form. Covalent bonds share electrons, so the
EN difference would be smaller, whereas ionic bonds that transfer electrons
should have a high EN difference. There are 3 criteria that must be meet in
order for a chemical reaction to occur. 
Reactants must: collide, collide with proper orientation, collide with
enough energy.  Things that can speed up
a reaction include: a catalyst, increase in temperature, stirring, increasing
surface area and more. H2O is a covalent compound as it has an EN of 1.5 making
it a polar covalent molecule. Water has all three types of intermolecular
forces, London dispersion, dipole-dipole and hydrogen bonding, with the
strongest and most prevalent being the latter. Water has a pH of 7 making it
safe to consume due to its unreactive nature. With the proper orientation and
speed, the collision theory allows for two oxygen molecules to bond when the
negative dipole meets the positive side. Jejunum – The middle segment of the
small intestine.  With epithelial cells
and layers of villi along folded inner walls, the jejunum is responsible for
the majority of nutrient absorption in the digestive system.  After passing through this section of the
small intestine, more than 90% of all nutritional content has been absorbed
into the body.

Ileum-  At 3.5m long,
the Ileum is the longest and final segment in the small intestine. Its primary
function is to absorb vitaminB12 and reabsorb conjugated bile salts. The inner
wall is smoother than previous sections and has slower peristaltic
contractions, 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 for
excretion. It is broken up into four parts: the ascending colon, the transverse
colon, the descending colon and the sigmoid colon. First, water and salts are
removed from the waste as it passes through the colon during a period of 36
hours. The waste makes its way to the sigmoid where it is stored until
defecation (“Large Intestine – Anatomy and Physiology,” n.d.). Like the small
intestine, the colon is made up of four layers of tissue, each coated with
villi, mucosa or epithelial cells to remove any final nutrients. A variety of
bacteria is mixed with with the chyme to begin turning it into feces. Bacterial
fermentation releases vitamins K, B1, B2, B6, B12, and biotin, as well as
creates flatulence (gas) from the methane and carbon dioxide in the bowel
(Bradford, 2016). The rectum is the last part of the digestive system right
before the anus and is about 10cm-15cm long. It’s function is to temporarily
store feces. The muscular pouch holding excrement is able to expand to
accommodate more waste. When waste is about to be expelled, the internal
sphincter relaxes and involuntary and voluntary muscle contractions begin
working (“Rectum Anatomy, Diagram & Function,” 2015). Ultrasound
Technician – An ultrasound technician operates equipment that uses high
frequency sound waves to create images of a patients internal organs. The work
done helps doctors make decisions on patient treatment, based on any
abnormalities present in the imagery. Theses technicians work directly with
patients and doctors and can specialize in fields such as obstetric and
gynecologic, abdominal, breast, vascular, or cardiac sonography (McKay, n.d.). Gastroenterologist
– A physician with dedicated training and experience who has studied in the
management of diseases of the gastrointestinal tract and liver. These doctors
can treat a variety of conditions from Hepatitis C to irritable bowel syndrome
(IBS). There are various fields of study, as some physicians may choose to
specialize in hepatology, transplantation or other (“What Is a
Gastroenterologist,” n.d.). They may perform endoscopic procedures in which
special instruments are used to view ones GI tract. Gastroenterologists do not
perform surgery however, they can work alongside a GI surgeon or provide
treatment and advice to patients.