Digestive Enzymes & Cell Types ...& random enzymes because why not, it's not like you're gonna pass this, B [Bio MCAT Prep]
Which enzyme is involved in carbohydrate digestion? Pepsin Salivary amylase Chyme Nucleases Bile
The salivary enzyme amylase begins the breakdown of food STARCHES into maltose, a disaccharide
Hydrolase enzymes
These break chemical bonds by using water. Examples include esterases, proteases, glycosidases, nucleosidases, and lipases.
Which pancreatic enzyme is activated first, then proceeds to activate other enzymes such as pancreatic amylase and pancreatic deoxyribonuclease? Lipase Chymotrypsin Trypsin Ribonuclease
Trypsin All pancreatic enzymes are secreted into the duodenum in zymogen form in order to prevent autodigestion of the small intestine. Trypsinogen is autoactivated to trypsin, which then proceeds to activate the other enzymes released from the pancreas, such as chymotrypsin, amylase, lipase, and the enzymes that break down digested DNA and RNA.
Which of these enzymes would result in the biggest loss of digestion, if absent from the small intestine? Pancreatic amylase Pancreatic lipase Trypsin Chymotrypsin
Trypsin Trypsin is created by the pancreas, and is responsible for the degradation of proteins in the lumen of the small intestine. More importantly, activated trypsin activates all of the other enzymes present in the small intestine. If trypsin is absent, virtually no digestion would take place.
bile
a bitter greenish-brown alkaline fluid that aids digestion and is secreted by the liver and stored in the gallbladder.
Goblet cell
a column-shaped cell found in the respiratory and intestinal tracts, which secretes the main component of mucus
Intrinsic Factor (IF)
a glycoprotein secreted by the stomach that results in the absorption of vitamin B12. Made by parietal cells.
Teichoic acid
a phosphorylated polyalcohol found in the cell wall of some gram-positive Bacteria Teichoic acids are an important part of a Gram positive organism's cell wall and serve an integral function in the organism's adherence and penetrative properties.
Oxyntic glands
a. Acid-secreting region in fundus and body of stomach. b. Contains four types of cells: Parietal, Mucus, Chief and Entroendocrine cells.
Mucous cell
cell type found in the stomach lining; secretes protective mucous
Kinase etymology
kinein = to move -ase = enzyme that degrades Therefore: Kinase is an enzyme that catalyzes the transfer of a phosphate group from ATP (or another high energy carrier) to a specified molecule
Acetylcholine (ACh)
parasympathetic neurotransmitter; the physiologic effects of parasympathetic activity can reasonably be simplified to the aphorism "rest and digest". NOTE: Also a neurotransmitter that enables learning and memory and also triggers muscle contraction)
ECL (enterochromaffin-like cells)
secrete histamine
G cell
secretes hormone gastrin stimulates parietal cells stimulates parietal cell maturation and growth
Parietal cell
secretes hydrochloric acid (gastric acid) and intrinsic factor
Chief cell
secretes pepsinogen and gastric lipase NOT gastric acid (function of parietal cells)
Protease
A hydrolase enzyme that helps proteolysis: protein catabolism by hydrolysis of peptide bonds.
Phosphatase
A type of hydrolase that removes a phosphate group (OPPOSITE to kinase and phosphorylase)
Carbohydrate digestion begins in the mouth with what enzyme? Pepsin Lipase Trypsin Alpha-amylase
Alpha-amylase is a component of saliva and is responsible for the initial digestion of carbohydrate and starch molecules. Chewing food increases the surface area over which alpha-amylase can act on ingested starches, preparing them for further digestion by the stomach. Trypsin and pepsin break down proteins, while lipase breaks down fats. Pepsin becomes active in the stomach, while trypsin and lipase are mostly active in the small intestine.
Phosphorylase
An enzyme which catalyzes phosphorylation by means of inorganic phosphates
Phosphotransferase
Any of a class of enzymes, including the kinases, that catalyze the transfer of phosphorus-containing groups from one compound to another. Also called transphosphatase.
Which of the following is not a component of bile? Proteases Bilirubin Phospholipids Cholesterol
Bile is released from the gall bladder into the small intestine, where it helps with the emulsification of fats. Bile salts and phospholipids are crucial amphipathic compounds that allow lipids to associate while in the aqueous environment of the small intestine. Cholesterol promotes fluidity and prevents the lipids from becoming tightly packed. Bilirubin is a byproduct produced in the liver and secreted in bile; it is later reabsorbed in the ileum and returned to the liver in a cyclic pattern. Proteases are secreted from the pancreas and assist in protein cleavage in the small intestine. They are not involved in bile or lipid digestion.
Chief cells in the body of the stomach are responsible for secreting which substance? Pepsin Trypsinogen Pepsinogen Trypsin
Chief cells are responsible for secreting the zymogen pepsinogen into the lumen of the stomach. Once pepsinogen enters the acidic environment of the stomach, it auto-catalyzes its conversion into the fully functional enzyme pepsin, which serves to breakdown proteins into smaller amino acid units by cleaving peptide bonds. The reason that chief cells secrete the zymogen, rather than active pepsin, is to prevent the active enzyme from degrading the walls of the stomach. Trypsin and trypsinogen are released from the pancreas and also help to break down proteins in the small intestine.
Which enzyme, when released from the duodenum of the small intestine, stimulates the gallbladder to contract? Secretin Gastrin Cholecystokinin Chymotrypsin
Cholecystokinin (CCK), made by the I cells of the small intestine and secreted into the duodenum, serves to stimulate contraction of the muscular layer of the gallbladder. CCK is generally released within two to three minutes of ingesting food, especially foods that are high in fats and triglycerides. As the gallbladder contracts, it releases bile salts into the duodenum that help solubilize ingested fat for absorption in the jejunum of the small intestine. Secretin stimulates release of bicarbonate from the pancreas, gastrin stimulates release of acid in the stomach, and chymotrypsin cleaves peptide bonds of ingested proteins.
Methylmalonic aciduria
Deficiency of methylmalonyl CoA mutaseor mutation in vit B12 metabolism/transport. nutritional deficiency of vitamin B12 can also cause methylmalonic acidemia. Buildup of methylmalonyl CoA. Metabolic acidosis, neurological manifestatoins (seizures, encephalopathy). Cobalamin (B12) supplementation can help if enzyme has low affinity for B12.
Which enzyme is involved in protein digestion? Pepsin Salivary amylase Chyme Nucleases Bile
Digestion of proteins begins in the stomach. The low pH of the stomach converts pepsinogen into pepsin, which is then used to break down proteins.
Which cell in the body of the stomach releases histamine to promote the breakdown of food? Chief cells G cells Parietal cells Enterochromaffin-like (ECL) cells
Enterochromaffin-like (ECL) cells are neuroendocrine cells in the body of the stomach that release histamine to stimulate the secretion of acid by parietal cells. They function in an indirect manner to decrease the pH of the stomach. Chief cells release pepsinogen, which is activated to become pepsin by the acidic pH of the stomach and promotes protein breakdown. G cells release gastrin from the antrum of the stomach to encourage acid secretion by parietal cells.
Urease
Enzyme that changes urea into ammonia and carbon dioxide
"-ase" suffix
Enzyme that participates in degrading the root word [EX: urea- and -ase = degreades urea]
Lipase, produced by the pancreas, is responsible for breaking down which macromolecule?
Fat Lipase is produced by the pancreas in response to the ingestion of meals high in fat, and is responsible for cleaving fats into monoglycerides and triglycerides. Proteins are broken down by pepsin and trypsin, nucleotides are broken down primarily by high acid content, and starches and carbohydrates are broken down by amylase.
Which of the following cell types is known to secrete the peptide hormone that stimulates parietal cells to secrete hydrochloric acid? Parietal cells G cells Mucous cells Chief cells
G cells secrete the large peptide hormone gastrin, which travels through blood to stimulate parietal cells to secrete hydrochloric acid. Mucous cells produce mucus to protect the epithelial lining of the stomach from the harsh acidic environment. Chief cells are found in the exocrine glands and secrete pepsinogen, which is activated by the low pH of the stomach to become pepsin. Pepsin catalyzes the breakdown of protein into peptides.
Autodigestion of the stomach mucosal lining is prevented by which type of stomach cells? G cells Goblet cells D cells Enterochromaffin-like (ECL) cells
Goblet cells secrete a thick layer of mucous to prevent autodigestion of the stomach wall by enzymes secreted into the lumen, such as pepsin, and the low pH of the stomach contents. D cells secrete somatostatin to prevent gastric acid secretion, G cells secrete gastrin to promote acid secretion into the gastric lumen, and enterochromaffin-like (ECL) cells secrete histamine to promote acidification of the gastric lumen.
Somatostatin
INHIBITORY HORMONE: hormone that inhibits release of growth hormone and insulin Affects neurotransmission and cell proliferation via interaction with G protein-coupled somatostatin receptors and inhibition of the release of numerous secondary hormones Released in pyloric antum Does NOT have any autocrine activity, i.e. it does not feedback inhibit itself.
Which of the following cell types in the stomach is not necessary for digestive purposes? G cells Mucous cells Parietal cells Chief cells
In order to stimulate digestion in the stomach G cells secrete gastrin, which stimulates parietal cells. Pepsinogen is released by chief cells. The parietal cells release hydrochloric acid into the stomach lumen. The lowered acidity cleaves pepsinogen and creates pepsin, which begins to degrade proteins. Mucous cells have the nondigestive role of lubricating the stomach lumen and protecting the stomach epithelium from degradation by the highly acidic gastric juices.
Which of the following stomach cells releases pepsinogen? Goblet cells Chief cells Parietal cells Pepsinogen is not released in the stomach; pepsin is released and converted to pepsinogen
In the stomach, food is broken down using a host of different cells and enzymatic processes. Chief cells release pepsinogen, making it the correct answer. Parietel cells, which release HCl, allow the conversion of pepsinogen (a zymogen) into pepsin. Pepsin actively digests proteins in the highly acidic environment of the stomach. Goblet cells release mucus which lines the stomach for protection.
Differences between kinase and phosphorylase
KINASE: > Transfers Pi from ATP to substance > Adds Pi to organic substrates like proteins, lipids, simple carbohydrates, and nucleic acids > Adds Pi to existing organic molecules > Regulated by phosphorylation > [EX: protein kinases, lipid kinases, and carbohydrate kinase] PHOSPHORYLASE: > Adds Pi to organic molecules (EX: glucose) > Uses inorganic Pi groups > Regulated by phosphorylation OR allosteric regulation > [EX: glycogen phosphorylase, starch phosphorylase, and polynucleotide phosphorylase]
Under normal conditions, what stimulates the release of somatostatin from Antral D-cells? Low fat content in gastric chyme Acetylcholine Low gastric pH Distention of the stomach
Low gastric pH stimulates the release of somatostatin from Antral D-cells
Which of the following enzymes would function best at a pH of 2? Carboxypeptidase Chymotrypsin Pepsin Sucrase
Only one of the enzymes listed functions in the stomach, where high acidity results in a low pH. That enzyme is pepsin. Other enzymes listed function in the small intestine, and will be denatured by high acidity.
The parietal cells of the stomach fundus are responsible for secreting which component of the gastric juices? Hydrochloric acid Trypsin Mucous Histamine
Parietal cells are located in the body of the stomach, and are responsible for secreting acid when stimulated by a variety of hormones, including gastrin (from G cells) and histamine (from enterochromaffin-like (ECL) cells). The release of acid allows food particles to be broken down in the stomach before they are transported through the antrum to the small intestine. Chief cells produce pepsinogen, trypsin is released from the pancreas into the small intestine, and ECL cells release histamine to stimulate parietal cells to secrete acid.
In addition to making acid for secretion into the stomach lumen, parietal cells also make which additional molecule? Pepsinogen Intrinsic factor Amylase Trypsin
Parietal cells, in addition to secreting hydrochloric acid into the stomach lumen, also make intrinsic factor (IF) that serves to scavenge vitamin B-12 in the stomach and chaperone it to the ileum for absorption. IF is important because a lack of B-12 is implicated in numerous metabolic diseases and anemia. The other enzymes listed are produced by different cells. Pepsinogen is released by chief cells of the stomach, and trypsin and amylase by the acinar cells of the pancreas.
chyme
Partially digested, semiliquid food mixed with digestive enzymes and acids in the stomach.
Peptidase vs protease ?
Peptidases- cleaves peptide bonds between amino acids Proteases- cleaves peptide bonds between amino acids within a complete protein chain No difference really, its just a naming distinction
Where does protein digestion begin? Stomach Oral cavity Large intestine Small intestine
Protein digestion begins in the stomach, where it is exposed to the protein pepsin. Pepsin only serves preliminary digestive processes. Protein fragments are further broken down by proteases in the small intestine, allowing amino acids and small protein fragments to be absorbed into the bloodstream. Carbohydrate digestion begins in the mouth with salivary amylase. Lipid digestion and nucleic acid digestion begin in the small intestine.
Mutase
Relocates a functional group within a molecule; is an enzyme of the isomerase class that catalyzes the movement of a functional group from one position to another within the same molecule. In other words, mutases catalyze intramolecular group transfers. (e.g., vitamin B12-dependent enzyme Methylmalonyl-CoA mutase (MCM) catalyzes the isomerization of methylmalonyl-CoA to succinyl-CoA in humans)
Aerophilic organisms
Requires air to properly grow Ex: Aerophilic organisms, such as H. pylori, are capable of utilizing oxygen for their survival (contrast to anaerobic).
Which of the following enzymes can break complex carbohydrates into simple sugars? Salivary amylase Mucin Carbonic anhydrase Lingual lipase
Salivary amylase is produced by the salivary glands in the mouth. Its primary role is to break carbohydrates into simple sugars so that they can be digested further after passing through the oral cavity. Lingual lipase is responsible for the digestion of lipids (fats), not carbohydrates. Carbonic anhydrase proteins are responsible for reacting gaseous carbon dioxide to form bicarbonate or carbonic acid. Salivary carbonic anhydrase removes the gas from ingested carbonated drinks; it does not participate in the digestion of food. Mucin is a protein found in saliva and mucous linings, and is designed to add viscosity to these secretions. It serves no enzymatic function.
Endocrine cells of gastric epithelium
Secrete somatostatin
Which of the following secrete hydrochloric acid (HCl) in the stomach lumen? Chief cells Pepsinogen cells Parietal cells Pepsin cells G cells
The correct answer is parietal cells. Parietal cells are responsible for HCl secretion in the stomach, which lowers the overall pH of the stomach. Chief cells secrete pepsinogen, which is converted to pepsin and is responsible for digesting proteins. G cells secrete gastrin, which stimulates parietal cells.
The pancreas is responsible for secreting which enzyme? Pepsinogen Gastrin Lipase Pepsin
The pancreas is responsible for secreting both lipase and amylase, which are needed to break down fats and starches, respectively. The pancreas is stimulated to release its respective enzymes about two to three hours after a fatty or carbohydrate-rich meal. These enzymes enter the duodenum through the ampulla of vater. In the duodenum, ingested fats and sugars are broken down to be absorbed later in the jejunum. Gastrin is released by G cells and stimulates the release of hydrochloric acid in the stomach. Chief cells release pepsinogen into the acidic environment, allowing the conversion of pepsinogen to pepsin.
