Human Digestion Flashcards
Where does protein digestion begin?
Protein digestion begins in the stomach ( pepsinogen/pepsin )
What are the steps of digestion?
Ingestion, digestion, absorption, transport, assimilation, egestion
Why do human’s need to digest food?
Food molecules ingested are typically large insoluble macromolecules that must be hydrolyzed to be absorbed, to pass through cell membranes
What is the macromolecule of a protein?
Protein
What is the form of a protein after digestion?
Amino Acid
What is the macromolecule of a lipid?
Triglyceride
What is the form of a lipid after digestion?
Glycerol and fatty acids
What is the macromolecule of a carbohydrate?
monosaccharides
What is the form of a carbohydrate after digestion?
Monosaccharides
What is the macromolecule of nucleic acids?
DNA and RNA
What is the form of nucleic acid after digestion?
Nucleotides
Describe the alimentary canal
long, muscular, digestive tube
What composes accessory digestive organs?
liver, pancreas, and gall bladder
What composes the alimentary canal?
esophagus, stomach, small and large
Which canal does food pass through?
Alimentary canal
Where does food not pass through
liver, pancreas, gall bladder
What do accessory digestive organs do?
Aid in digestion
Where does chemical digestion occur?
Small intestine
Mechanical digestion
physically breaking large molecules into smaller “chunks” ( chewing, mixing, churning of food )
What is the inner portion of the esophagus called?
The hollow inner portion of the esophagus is called the lumen
Chemical digestion
Hydrolysis ( enzymes ), macromolecules hydrolyzed into smaller and smaller molecules through enzyme-catalyzed reactions
Hydrolysis
catabolic reactions that dominate the digestive process
Enzymes
enzymes are globular proteins that lower the activation energy needed to start a chemical reaction and speed up the rate of chemical reactions
Where are digestive enzymes released into?
The gut from the exocrine glands and pancreas
What do exocrine glands have?
ducts and secrete substances to an epithelial surface
Where is salivary amylase produced?
Salivary glands
Where is the site of action for salivary amylase?
Mouth/ esophagus
Where is pepsin/protease produced?
Gastric glands and stomach cells
Where is the site of action for pepsin/protease?
Stomach
Where is amylase produced?
Pancreas and salivary glands
Where is the site of action for amylase?
Lumen of the small intestine
Where is endopeptidase/protease produced?
Pancreas
Where is the site of action for protease/ endopeptidase?
Lumen of the small intestine
Where is lipase produced?
Pancrease
Where is the site of action for lipase?
Lumen of the small intestine
Where is nuclease produced?
Pancreas
Where is the site of action for nuclease?
Lumen of the small intestine
What are the three main parts of the alimentary canal?
Stomach, Small Intestine, Large Intestine
What do nervous and hormonal mechanisms control?
the section of digestive juices and control the volume of content of the gastric secretions
What do HCl conditions in the stomach do?
HCL conditions in the stomach favor some hydrolysis reactions and help to control pathogens in ingested good
Pepsinogen
a protease that hydrolyzes peptide bonds in proteins
How is pepsinogen activated?
Pepsinogen is activated into pepsin in the stomach by HCl
What does HCl in the stomach help?
HCl in the stomach helps to initially denature proteins and kill pathogenic bacteria and fungi in ingested foods
How are acidic conditions in the stomach maintained?
Acidic conditions of the stomach are tainted by proton pumps in parietal cells in the gastric pits
How are acidic conditions in the stomach maintained?
Acidic conditions of the stomach are tainted by proton pumps in parietal cells in the gastric pits
Stomach uvlers
inflamed/ damaged areas of open sores in the stomach wall
What causes stomach ulcers?
caused by exposure of stomach cells to stomach acid
How does helicobacter pylori survive acidic conditions in the stomach?
Penetrates mucus lining ( mucosa )
What additional factors can cause ulcers?
Stress/diet/ overuse of aspirin, ibuprofen, NSAIDS
Where do exocrine glands do?
Exocrine glands secrete to the surface of the body or lumen of the gut
Exocrine glands in the digestive system
liver, gall bladder, pancreas, salivary glands, intestinal lands, gastric glands
Describe exocrine glands
Exocrine glands have ducts ( tube-like structures ) through which their products are secreted
Which ducts secrete digestive juices?
Salivary glands, gastric glands, pancreas, glands in the wall of the small intestine
What is similar to all digestive juices?
all contain water, mucous, and salts
What are the digestive juices?
saliva, gastric juice, and pancreatic juice
Where is saliva found?
mouth/throat
What is the function of saliva
convert starch into maltose
Where is gastric juice found?
stomach
What is the function of gastric juice?
Convert proteins into polypeptides
Where is pancreatic juice found?
Small intestine/ duodenum
What is the function of pancreatic juice?
Convert proteins into polypeptides, convert triglycerides into glycerol + fatty acids, and convert starch into maltose
What do most enzymes digest?
Enzymes digest most macromolecules in food into monomers in the small intestine
What does the pancreas secrete?
The pancreas secretes enzymes into the lumen of the small intestine
Where are enzymes secreted>
Enzymes are secreted by the pancreas through a duct into the lumen of the small intestine
Serosa
Protective outer covering
Longitudinal muscles
Peristalsis (move food along gut/ mix with enzymes)
Circular muscles
Segmentation (prevent backward movement of food/ mix with enzymes)
Submucosa
Separates innermost mucosa from muscles
Mucosa
Highly folded inner epithelial layer (villi and microvilli) to increase the surface area for absorption of monomers from the intestinal lumen
Mucosa
Highly folded inner epithelial layer (villi and microvilli) to increase the surface area for absorption of monomers from the intestinal lumen
Lumen
The lumen (inner-most, hollow tube) of the small intestine is lined with folded/ finger-like (increased surface area) projections of the mucosa called villi
What do microvilli increase?
Microvilli increase the surface area for
absorption
What do microvilli increase?
Microvilli increase the surface area for
absorption
What do microvilli increase?
Microvilli increase the surface area for
absorption
What are the different methods of membrane transport?
Diffusion, osmosis, facilitated diffusion, active transport, exocytosis
Diffusion
Fatty acids and other small,
non-polar substances
easily pass through the hydrophobic cell
membranes of epithelial cells through simple diffusion
Osmosis
Water diffuses across epithelial cell membranes in response to movement of
ions and other hydrophilic monomers (occurs in small intestine and large intestine)
Facilitated Diffusion
Protein channels within epithelial cell membranes (of villi and microvilli) allow passage of hydrophilic food molecules (water-soluble/ polar molecules like fructose, vitamins, glucose, amino acids, and minerals)
Active transport
Glucose and amino acids are pumped (membrane proteins) against their concentration gradients, or they are transported with Na+ ions (co-transport) as Na+ ions are actively pumped across the membrane (secondary active transport)
Endocytosis
Invagination of the cell membrane to form a vesicle around bulk fluids/ large molecules that must remain intact in the intestinal lumen and bring them into the cell (pinocytosis: “cell drinking”)
Endocytosis
Invagination of the cell membrane to form a vesicle around bulk fluids/ large molecules that must remain intact in the intestinal lumen and bring them into the cell (pinocytosis: “cell drinking”)
What is the main function of the large intestine?
Absorbs water/minerals/vitamins/ions
Egestion
Materials not absorbed are egested= BELCH
Rate of transit is correlated with what…
he RATE of transit of materials through the large intestine is positively correlated with their fiber content (More fiber = faster rate of transit = less exposure to undesirable food chemicals etc./ decreases contact time between intestinal wall and food)
Why is fiber in the diet important?
helps “clean out” old/ damaged intestinal cells and unabsorbed materials, it provides bulk to keep materials moving, it absorbs water to keep faeces soft and easy to pass, “works out” the body’s normal microflora, reduces frequency of constipation, lowers risk of colon and rectal cancers, lowers blood cholesterol, regulates blood sugar levels (slows absorption rate of glucose), and decreases hunger (aids in weight management/ prevention of obesity)
Chlorea toxin causes
Dehydration
Vibrio cholerae
bacterial pathogen that infects intestines
Why does cholera toxin cause dehydration?
V. cholerae releases a toxin that binds to a receptor on the epithelial cells in the intestine.
