Chapter 18 Digestion Flashcards
1
Q
What are the main purposes of the digestive system in humans?
A
The digestive system provides basic organic molecules from food to make ATP build tissues and serve as cofactors and coenzymes.
2
Q
How does digestion break down food polymers?
A
via hydrolysis reactions.
3
Q
What is the role of absorption in digestion?
A
Absorption takes the monomer building blocks resulting from digestion into the bloodstream to be used by the cells.
4
Q
Why is the digestive tract considered outside the body despite being continuous?
A
Because it is open at both ends and continuous with the environment the digestive tract is considered outside the body; materials that cannot be digested like cellulose never actually enter the body.
5
Q
How does one-way transport in the digestive tract contribute to its function?
A
One-way transport allows for specialization of function along the tract facilitating different processes at different stages of digestion.
6
Q
What types of motility are involved in moving food through the digestive tract?
A
Motility includes ingestion (taking food into the mouth) mastication (chewing and mixing food with saliva) deglutition (swallowing) peristalsis (wave-like one-way movement) and segmentation (churning and mixing while moving forward).
7
Q
What substances are secreted by the digestive tract and what is their purpose?
A
The digestive tract secretes exocrine substances such as digestive enzymes hydrochloric acid mucus water and bicarbonate and endocrine hormones that regulate digestion.
8
Q
How is digestion achieved both physically and chemically?
A
Digestion breaks food down into smaller units physically (e.g. chewing) and chemically (e.g. enzyme activity) to prepare for absorption.
9
Q
What are the functions of absorption storage elimination and the immune barrier in the digestive tract?
A
Absorption passes broken-down food into blood or lymph; storage temporarily holds food; elimination removes undigested molecules; and the immune barrier prevents swallowed pathogens from entering the body through simple columnar epithelium with tight junctions.
10
Q
What are the four layers (tunics) of the alimentary tract and their main functions?
A
- Mucosa: inner secretory and absorptive layer may be folded to increase surface area contains goblet cells; 2. Submucosa: very vascular for nutrient pickup contains glands and nerve plexuses; 3. Muscularis: smooth muscle responsible for peristalsis and segmentation; 4. Serosa: outer binding and protective layer consisting of visceral peritoneum covering organs and parietal peritoneum lining the abdominal cavity.
11
Q
How does the parasympathetic nervous system regulate the gastrointestinal (GI) tract?
A
The parasympathetic division stimulates the esophagus stomach small intestine pancreas gallbladder and proximal large intestine via the vagus nerve.
12
Q
What effects does the sympathetic nervous system have on the GI tract?
A
The sympathetic division reduces peristalsis and secretion and stimulates contraction of sphincters.
13
Q
What intrinsic mechanisms regulate the GI tract?
A
Intrinsic regulation involves intrinsic sensory neurons in the gut wall through the enteric nervous system and paracrine regulators such as histamine.
14
Q
What are the main functions of mastication in the mouth?
A
Mastication breaks food down into smaller pieces for deglutition and mixes it with saliva.
15
Q
What components does saliva contain and what are their functions?
A
Saliva contains mucus to protect an antimicrobial agent to fight microbes and salivary amylase to start digestion of starch.
16
Q
List the primary functions of the stomach.
A
The stomach stores food churns food to mix with gastric secretions begins protein digestion kills bacteria in food acid and moves food into the small intestine as chyme.
17
Q
Describe the structure of the stomach in terms of its regions and lining features.
A
Food is delivered to the cardiac region from the esophagus then passes through the upper fundus region lower body region and distal pyloric region ending at the pyloric sphincter. The lining has folds called rugae.
18
Q
What are gastric pits and what kinds of secretory cells do they contain?
A
Gastric pits at the base of rugae folds lead to gastric glands containing mucus neck cells (secrete mucus) parietal cells (secrete HCl and intrinsic factor) chief cells (secrete pepsinogen) ECL cells (secrete histamine and serotonin) G cells (secrete gastrin) D cells (secrete somatostatin) and PD1 cells (secrete ghrelin).
19
Q
Explain how parietal cells form hydrochloric acid (HCl) in the stomach.
A
Parietal cells use primary active transport via H⁺/K⁺ ATPase pumps to secrete H⁺ into the stomach lumen while bringing K⁺ into the cell. Cl⁻ is secreted by facilitated diffusion coupled to bicarbonate movement formed from CO₂ and H₂O inside the cell. HCl is secreted into gastric juice and bicarbonate is secreted into the blood.
20
Q
How is HCl secretion in the stomach stimulated?
A
Gastrin made by G cells travels in the blood to parietal cells and stimulates them and also ECL cells to make histamine. Histamine acts on H₂ histamine receptors on parietal cells. Parasympathetic neurons and acetylcholine (ACh) also stimulate parietal and ECL cells.
21
Q
What are the functions of hydrochloric acid (HCl) in the stomach?
A
HCl drops the pH to about 2 which denatures proteins to allow enzyme access converts pepsinogen to active pepsin and creates the optimal pH for pepsin activity.
22
Q
Describe the role of pepsin in protein digestion.
A
Pepsin catalyzes the hydrolysis of peptide bonds in ingested proteins breaking them into smaller peptides.
23
Q
What defenses does the stomach have to protect its lining from damage by acid and pepsin?
A
Defenses include an adherent mucus layer with alkaline bicarbonate tight junctions between epithelial cells and rapid epithelial mitosis that replaces the lining every three days.
24
Q
How does digestion proceed in the stomach in terms of proteins and starches?
A
Proteins begin digestion in the stomach through pepsin activity. Starch digestion begins in the mouth via salivary amylase but stops in the stomach because the acidic pH (around 2) inactivates salivary amylase.
25
What causes erosions of the mucosa of the stomach or duodenum leading to peptic and duodenal ulcers?
HCl and the Helicobacter pylori bacterium which reduces mucosal barriers to acid.
26
What is the common treatment approach for ulcers caused by HCl and Helicobacter pylori?
Treatment combines K H pump inhibitors and two different antibiotics.
27
What are the symptoms produced by gastroesophageal reflux disease (GERD)?
Reflux of acidic gastric chyme produces symptoms such as heartburn cough and sore throat.
28
What are some risk factors for GERD?
Obesity pregnancy and hiatal hernia (upward protrusion of the stomach through the diaphragm).
29
How is GERD commonly treated?
With H2 receptor blockers and proton pump inhibitors (PPIs).
30
What are bariatric surgeries and why are they performed?
Bariatric surgeries promote significant weight loss in obese people who are prone to insulin resistance hypertension and hyperlipidemia.
31
Describe the Roux-en-Y gastric bypass procedure.
It creates a small pouch in the gastric fundus to which the mid-jejunum is attached.
32
What happens in a vertical sleeve gastrectomy?
About 85% of the stomach (gastric fundus and body) is removed but the intestinal pathway remains unaltered.
33
What are the three sections of the small intestine and their approximate lengths?
Duodenum (first 10 inches) jejunum (middle 25 inches) and ileum (last 35 inches).
34
How is the mucosa and submucosa of the small intestine structured to increase surface area?
They are folded into plicae circulares which are folded into villi which are further folded into microvilli.
35
What are the primary functions of the small intestine?
Complete digestion of carbohydrates proteins and fats and absorption of nutrients.
36
Where are sugars lipids amino acids calcium and iron absorbed in the small intestine?
In the duodenum and jejunum.
37
Where are bile salts vitamin B12 water and electrolytes absorbed in the small intestine?
In the ileum.
38
What cell types make up the villi in the small intestine mucosa?
Simple columnar epithelium enterocytes with goblet cells that produce mucus.
39
What does the connective tissue core of each villus contain?
Lymphocytes blood capillaries and a lymphatic vessel called a lacteal.
40
What nutrients do capillaries and lacteals in the villi absorb?
Capillaries absorb monosaccharides and amino acids; lacteals absorb fats.
41
What are microvilli and where are they located?
Microvilli are brush border foldings of the apical surface of each epithelial cell of the villus.
42
What are brush border enzymes and how do they function?
They are intestinal enzymes attached to the plasma membrane with active sites exposed to chyme that hydrolyze disaccharides polypeptides and other substrates into simple nutrient molecules.
43
What role does the enzyme lactase play in the small intestine?
Lactase digests lactose into glucose and galactose enabling its absorption in the small intestine.
44
What symptoms result from lactose intolerance and why?
Lactose intolerance causes accumulation of lactose in the intestine producing symptoms such as abdominal gas bloating diarrhea and nausea.
45
How does enterokinase contribute to protein digestion?
Enterokinase activates trypsin which indirectly activates other pancreatic juice enzymes necessary for protein digestion.
46
Why is alkaline phosphatase enzyme activity important and how is it regulated?
Alkaline phosphatase removes phosphate groups from organic molecules and its enzyme activity may be regulated by vitamin D.
47
What are the main functions of the large intestine?
The large intestine absorbs water electrolytes vitamin K and some B vitamins; produces vitamin K and B vitamins via microbial organisms; and stores feces.
48
What is the importance of intestinal microbiota in the large intestine?
Intestinal microbiota produce vitamin K and some B vitamins create short-chained fatty acids from cellulose dietary fiber and support the normal function of the large intestine.
49
How is water absorbed in the large intestine?
Water absorption in the large intestine is passive following an osmotic gradient set up by active Na⁺/K⁺ pumps.
50
What is diarrhea and what is its most common cause?
Diarrhea is the excretion of excessive fluid in the feces commonly caused by viral gastroenteritis (stomach flu) which leads to intestinal inflammation and excessive fluid secretion.
51
How do certain bacteria like Salmonella and Shigella cause diarrhea?
These bacteria invade the intestinal mucosa causing damage and inflammation that result in inflammatory diarrhea.
52
What happens as material passes to the rectum in the process of defecation?
As material passes to the rectum pressure increases and the internal anal sphincter relaxes creating the need to defecate.
53
How is defecation voluntarily controlled?
The external anal sphincter controls defecation voluntarily allowing feces to remain in the rectum until the urge is satisfied.
54
Which muscles aid defecation through contraction?
Contraction of abdominal and pelvic skeletal muscles known as the Valsalva maneuver aids defecation.
55
What are key structural features of the liver?
The liver is the largest abdominal organ beneath the diaphragm mostly on the right side. It has regenerative abilities due to mitosis of hepatocytes and is composed of hepatocytes separated by capillaries called sinusoids that have fenestrae with no diaphragm or basement membrane making them very permeable.
56
What role do Kupffer cells play in the liver?
Kupffer cells are part of the reticuloendothelial system and are located in the sinusoids of the liver.
57
What causes liver fibrosis and potentially cirrhosis?
Hepatic damage due to alcohol or viral hepatitis causes liver fibrosis which can lead to cirrhosis of the liver.
58
What is the hepatic portal system and its significance?
The hepatic portal system delivers products of digestion absorbed in the intestines to the liver via the hepatic portal vein preventing nutrients from directly entering general circulation. It includes a unique pattern of capillaries veins capillaries and veins.
59
Which organs contribute veins to the hepatic portal vein?
Veins from the pancreas gallbladder stomach omentum and spleen join the hepatic portal vein.
60
How does blood leave the liver after circulating through liver capillaries?
After circulating through liver capillaries blood leaves via the hepatic vein to join regular venous circulation.
61
What is the daily production range of bile by the liver?
The liver makes 250 to 1500 ml of bile per day.
62
What are the main components of bile produced by the liver?
Bile is composed of bile pigment bilirubin bile salts phospholipids lecithin cholesterol and inorganic ions.
63
How do bile salts behave in the intestinal lumen to aid digestion?
Bile salts group together with polar groups toward water and nonpolar groups inward away from water forming micelles.
64
What role do micelles play in fat digestion?
Fats from digestion enter the micelles and are emulsified providing a greater surface area for fat digestion by lipase.
65
How does the liver contribute to detoxification of blood?
Hepatocytes Kupffer cells and dendritic cells have pathogen recognition receptors that recognize PAMPs to scavenge blood-borne bacteria and the liver removes hormones drugs and other substances by excretion into bile phagocytosis by Kupffer cells and chemical alteration by hepatocytes.
66
What are some chemical conversions performed by the liver during detoxification?
The liver converts ammonia into urea porphyrins into bilirubin and purines into uric acid.
67
How does the liver regulate blood glucose levels?
The liver balances blood glucose by removing glucose and storing it as glycogen (glycogenesis) and triglycerides (lipogenesis) or breaking down glycogen (glycogenolysis) and releasing glucose into the blood.
68
What processes allow the liver to generate glucose and ketone bodies?
The liver can make glucose from amino acids through gluconeogenesis and convert fatty acids into ketone bodies through ketogenesis.
69
List the major functional categories of the liver and their key actions.
1. Detoxication of blood: phagocytosis by Kupffer cells chemical alteration of hormones and drugs production of urea and uric acid excretion of molecules in bile.
70
2. Carbohydrate metabolism: conversion of blood glucose to glycogen and fat production of glucose from glycogen and other molecules.
71
3. Lipid metabolism: synthesis of triglycerides and cholesterol excretion of cholesterol in bile production of ketone bodies.
72
4. Protein synthesis: production of albumin plasma transport proteins clotting factors.
73
5. Secretion of bile: synthesis of bile salts conjugation and excretion of bilirubin.
74
6. Storage of molecules: storage of glycogen minerals (iron zinc magnesium copper manganese) and vitamins A and D.
75
What is nonalcoholic fatty liver disease and what factors are associated with it?
Nonalcoholic fatty liver disease is associated with obesity insulin resistance or prediabetes and type 2 diabetes and is promoted by diets high in saturated fat and fructose. It is benign unless it develops into nonalcoholic steatohepatitis (NASH).
76
What distinguishes alcoholic hepatitis from alcoholic fatty liver disease?
Alcoholic hepatitis is chronic inflammation of the liver due to alcohol use whereas alcoholic fatty liver disease is the accumulation of triglycerides in the liver.
77
What changes occur in the liver during cirrhosis?
During cirrhosis liver portal lobules are destroyed and replaced by fibrotic scar tissue and regenerative nodules of hepatocytes that lack the normal plate-like structure.
78
How does cirrhotic liver tissue affect bilirubin removal and bile excretion?
Cirrhotic tissue cannot adequately remove bilirubin and toxic molecules from the blood and excrete them into the bile canaliculi causing jaundice and harmful effects in many organs.
79
What is the consequence of disrupted blood flow through liver sinusoids in cirrhosis?
Disrupted blood flow causes portal hypertension which is high pressure in the portal vein.
80
What are the most common causes of cirrhosis?
The most common causes of cirrhosis are hepatitis B virus hepatitis C virus alcoholism and nonalcoholic steatohepatitis.
81
What is the function of the gallbladder?
The gallbladder is a sac-like organ attached to the inferior surface of the liver that stores and concentrates bile from the liver.
82
How are gallstones formed?
Gallstones form when the liver secretes enough cholesterol to create a supersaturated solution and cholesterol crystals combine with mucus secreted by the gallbladder to create a sludge that can solidify into hard mineral deposits.
83
What complications can sizable gallstones cause?
Sizable gallstones can block the hepatic cystic or common bile ducts leading to pain and nausea called biliary colic.
84
What are the endocrine and exocrine functions of the pancreas?
The endocrine function involves the Islets of Langerhans cells making insulin and glucagon; the exocrine function involves acinar cells producing pancreatic juice delivered to the duodenum.
85
What does pancreatic juice contain and how are its enzymes activated?
Pancreatic juice contains bicarbonate and about 20 digestive enzymes most of which are inactive zymogens until they reach the small intestine where they become activated.
86
Which enzymes in pancreatic juice digest starch proteins and triglycerides?
Amylase digests starch trypsin digests proteins and activates other enzymes and lipase digests triglycerides.
87
What causes acute and chronic pancreatitis and what are their characteristics?
Acute pancreatitis is usually caused by gallstones or reactions to some drugs with rapid symptom onset and typical full recovery; chronic pancreatitis is usually due to chronic alcohol abuse.
88
What are the effects of the hormone gastrin secreted by the stomach?
Gastrin stimulates parietal cells to secrete HCl and chief cells to secrete pepsinogen.
89
Which hormone stimulates appetite and eating and where is it secreted?
Ghrelin is secreted by the stomach and stimulates appetite and eating.
90
What are the main functions of secretin secreted by the small intestine?
Secretin stimulates water and bicarbonate secretion from the pancreas and liver and potentiates actions of cholecystokinin on the pancreas.
91
How does cholecystokinin (CCK) affect the digestive system?
CCK stimulates contraction of the gallbladder secretion of pancreatic juice enzymes inhibits gastric motility and secretion and maintains structure of exocrine pancreas acini.
92
What role does gastric inhibitory peptide (GIP) play in digestion?
GIP inhibits gastric motility and secretion and stimulates secretion of insulin from pancreatic islets.
93
How does PYY (polypeptide YY) influence hunger and food intake?
PYY decreases hunger and food intake.
94
What is the effect of motilin on the digestive tract?
Motilin stimulates contractions and motility of the stomach and small intestine.
95
Describe the actions of glucagon-like peptide-I (GLP-I) secreted by the ileum and colon.
GLP-I inhibits gastric motility and secretion and stimulates secretion of insulin from pancreatic islets.
96
What is the function of guanylin in the ileum and colon?
Guanylin stimulates intestinal secretion of Cl⁻ causing elimination of NaCl and water in the feces.
97
How are stomach contractions regulated intrinsically?
Contractions are stimulated spontaneously by pacesetter cells in the greater curvature of the stomach.
98
Which cells initiate and regulate secretion of HCl and pepsinogen in the stomach?
G cells secrete gastrin D cells secrete somatostatin and ECL cells secrete histamine all regulating HCl and pepsinogen secretion.
99
What occurs during the cephalic phase of extrinsic gastric regulation?
The brain controls the stomach via vagus nerves; G cells secrete gastrin entering circulation which hormonally stimulates ECL cells to secrete histamine leading parietal cells to secrete HCl; this phase lasts about the first 30 minutes of a meal.
100
What triggers the gastric phase of extrinsic gastric regulation and what happens during it?
The arrival of food into the stomach triggers the gastric phase; gastric secretion is stimulated by stomach distension and the chemical nature of chyme causing secretion of gastrin and positive feedback as protein breakdown increases secretions.
101
How does fat and glucose affect gastric secretion during the gastric phase?
Glucose has no effect while fat inhibits gastric secretion.
102
Explain the negative feedback system regulating gastric secretion related to pH changes.
As pH drops due to more HCl somatostatin is released from D cells which inhibits gastrin secretion thereby decreasing gastric secretion.
103
How do proteins and polypeptides influence gastric secretion and pH balance?
Large amounts of proteins and polypeptides buffer the pH so secretion is matched to protein concentration.
104
What is the main purpose of the intestinal phase inhibition of gastric activity when chyme enters the small intestine?
The main purpose is to slow the movement of chyme into the duodenum to allow enough time for digestion and absorption.
105
How does stretch in the duodenum affect gastric activity?
Stretch when food enters the duodenum stimulates a neural reflex that inhibits gastric stimulation via the vagus nerve.
106
What role does fat in the duodenum play in regulating gastric function?
The presence of fats stimulates the duodenum to produce enterogastrone which inhibits gastric function.
107
Describe the three phases of gastric secretion.
1. Cephalic Phase: Sight smell and taste of food stimulate vagus nuclei leading to secretion of pepsinogen histamine and gastric acid. 2. Gastric Phase: Stomach distension and amino acids/peptides stimulate acid secretion via vagus nerve and gastrin hormone; gastrin secretion is inhibited at low pH. 3. Intestinal Phase: Arrival of chyme in duodenum causes neural inhibition of gastric emptying and acid secretion and duodenal secretion of enterogastrone inhibiting gastric activity.
108
How does the cephalic phase stimulate gastric secretion?
Sight smell and taste of food stimulate vagus nuclei in the brain which stimulates chief cells to secrete pepsinogen and ECL cells to secrete histamine leading to parietal cells secreting HCl.
109
What triggers acid secretion during the gastric phase?
Distension of the stomach stimulates the vagus nerve and amino acids and peptides in the stomach lumen stimulate acid secretion both directly by parietal cells and mainly by stimulating gastrin secretion.
110
How is gastrin secretion regulated during the gastric phase?
Gastrin secretion is inhibited when the pH of gastric juice falls below 2.5.
111
What neural and hormonal mechanisms inhibit gastric emptying and acid secretion during the intestinal phase?
Neural inhibition occurs due to distension and increased osmotic pressure in the duodenum triggering a reflex inhibition and the hormone enterogastrone secreted in response to fats inhibits gastric motility and secretion.
112
What is the role of the enteric nervous system (ENS) in intestinal function regulation?
The ENS composed of enteric neurons and glial cells innervates the intestines and includes interneurons sensory neurons and autonomic motor neurons that provide local regulation and communicate with the CNS via the vagus nerve.
113
How does the arrival of chyme in the duodenum affect pancreatic juice and bile secretion?
The arrival of chyme stimulates the intestinal phase of gastric regulation and reflex secretion of pancreatic juice and bile while also slowing additional chyme arrival through neural reflexes and enterogastrone to allow efficient digestion.
114
What hormones are produced when chyme enters the duodenum and what are their functions?
Cholecystokinin (CCK) is produced in response to partially digested proteins and fats and stimulates pancreatic juice secretion and gallbladder contraction. Secretin is produced in response to a drop in pH and stimulates bicarbonate and water secretion from pancreatic ductules.
115
How is pancreatic enzyme production regulated?
Pancreatic enzyme production of trypsin lipase and amylase from acinar cells is stimulated by acetylcholine (ACh) from the vagus nerve and CCK from the duodenum.
116
Where does starch digestion begin and what enzyme is involved?
Starch digestion begins in the mouth with the enzyme salivary amylase which breaks starch into shorter polysaccharide chains.
117
Why does starch digestion not occur in the stomach?
Starch digestion does not occur in the stomach because the environment is too acidic for salivary amylase to function.
118
What enzyme continues starch digestion in the intestines and what does it produce?
Pancreatic amylase continues starch digestion in the intestines breaking starch down into short chains including short oligosaccharides maltose and maltotriose.
119
What role do brush border enzymes play in carbohydrate digestion?
Brush border enzymes finish breaking down disaccharides such as maltose sucrose and lactose into simple sugars mainly glucose.
120
How are monosaccharides absorbed across the intestinal epithelium?
Monosaccharides are absorbed via secondary active transport with sodium (1 glucose per 2 Na+) followed by facilitated diffusion through GLUT carriers into the interstitial fluid and then to the capillary blood of the villus.
121
Describe the initial steps of protein digestion in the stomach.
Protein digestion begins in the stomach with pepsin and hydrochloric acid which produce short-chain polypeptides.
122
Which enzymes complete protein digestion in the duodenum and jejunum and what are the final products?
Pancreatic enzymes trypsin chymotrypsin elastase carboxypeptidase and the brush border enzyme aminopeptidase finish protein digestion producing amino acids some dipeptides and tripeptides.
123
How are proteins absorbed across the intestinal epithelium?
Free amino acids are co-transported with Na+ while dipeptides and tripeptides use secondary active transport driven by an H+ gradient. Free amino acids then move by facilitated diffusion into interstitial fluid and blood capillaries.
124
Explain the process of fat digestion starting in the duodenum.
Fat digestion begins in the duodenum when bile emulsifies fats making them accessible to pancreatic lipase which breaks them down into fatty acids and monoglycerides.
125
How are fats absorbed into the intestinal epithelial cells?
Fatty acids and monoglycerides enter bile micelles and are transported to the brush border. They then leave the micelles diffuse into epithelial cells of the villi where they are reassembled into triglycerides cholesterol and phospholipids then combined with proteins to form chylomicrons.
126
What happens to chylomicrons after they are formed inside epithelial cells?
Chylomicrons are secreted by exocytosis into the central lacteal of the villus which is part of the lymphatic system.
127
What are the characteristics of salivary amylase regarding site of action substrate optimum pH and products?
Salivary amylase acts in the mouth is secreted in saliva acts on starch at an optimum pH of 6.7 and produces maltose.
128
What are the properties of pepsin in digestion?
Pepsin acts in the stomach is secreted by gastric glands digests proteins at an optimum pH of 1.6 to 2.4 and produces shorter polypeptides.
129
Identify the action of pancreatic amylase.
Pancreatic amylase acts in the duodenum is secreted in pancreatic juice digests starch at a pH of 6.7 to 7.0 producing maltose maltotriose and oligosaccharides.
130
What is the function of trypsin chymotrypsin and carboxypeptidase in digestion?
These pancreatic enzymes act in the small intestine digest polypeptides at an optimum pH of 8.0 producing amino acids dipeptides and tripeptides.
131
What enzyme breaks down triglycerides in the small intestine and what are the products?
Pancreatic lipase breaks down triglycerides in the small intestine producing fatty acids and monoglycerides.
132
Where is maltase located and what substrate does it act on?
Maltase is located in the brush border of epithelial cells in the small intestine and acts on maltose.
133
What are the products of maltase activity and at what pH does it function?
Maltase breaks down maltose into glucose functioning optimally at pH 5.0 to 7.0.
134
Describe the location substrate and products of sucrase activity.
Sucrase is located in the brush border of epithelial cells in the small intestine acts on sucrose and produces glucose and fructose at a pH of 5.0 to 7.0.
135
What is the substrate and products of lactase enzyme and where is it found?
Lactase is found in the brush border of epithelial cells in the small intestine; it acts on lactose and produces glucose and galactose at pH 5.8 to 6.2.
136
Explain the role of aminopeptidase in protein digestion including its location substrate products and pH.
Aminopeptidase is located in the brush border of epithelial cells in the small intestine acts on polypeptides and produces amino acids dipeptides and tripeptides functioning optimally at pH 8.0.
