What to know for Human Digestion Quiz Flashcards
Where does protein digestion begin?
stomach
What is the role of Hydrochloric acid in the stomach?
HCl conditions in the stomach favor some hydrolysis reactions and help to control pathogens in ingested food
Where does chemical digestion occur?
The small intestine
Why is fiber important in a human diet?
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)
Why can cellulose and lignin not be digested?
Cellulose and lignin are not digested because humans do NOT possess enzymes (cellulase) or gut bacteria to break them down
What is the rate of material movement positively correlated with?
fiber content
What are waste products egested from the body? ( Hint BILE )
bile pigments, epithelial cells, lignin, cellulose, human microflora/ bacteria
What is the main role of the large intestine?
MAIN FUNCTION: Absorption of water (and minerals/ vitamins/ ions)
Highly folded – maximizes surface area for absorption of water into the blood
What else does the large intestine do?
Secretes mucus-
Lubricates passing feces
Movement of undigested/ undigestable food products- Peristalsis
Egestion- (Understand that materials not absorbed are
egested = BELCH)
What is the general function of villi
absorb nutrients ( The inside of the small intestine is lined with villi that absorb nutrients from the liquid mixture called chyme produced in the stomach from the food we eat )
villi increase available surface area for material absorption
What do villi increase?
Villi increase the surface area of epithelium over which absorption is carried out.
What do villi absorb?
Villi absorb monomers formed by digestion as well as mineral ions and vitamins
What is the structure of cells of the epithelium adapted for?
the structure of cells of the epithelium of the villi is adapted to the absorption of food
What is the role of the pancreas in digestion?
The pancreas secretes enzymes into the lumen of the small intestine
What is the role of the pancreas in digestion?
The pancreas regulates the uptake of glucose
* Insulin increases glucose uptake by cells
* Glucagon decreases glucose uptake by cells
What are the digestive enzymes the pancreas secretes?
Salivary amylase, pepsin/protease, amylase, lipase, trypsin/ endopeptidase, nuclease
Nervous mechanism
The sight and smell of food trigger an immediate response by which gastric juice is secreted by the stomach during pre-ingestion
When food enters the stomach it causes distention, which is detected by stretch receptors in the stomach lining
Signals are sent to the brain, which triggers the release of digestive hormones to achieve sustained gastric stimulation
Hormonal Mechanism
Gastrin is secreted into the bloodstream from the gastric pits of the stomach and stimulates the release of stomach acids
If stomach pH drops too low (becomes too acidic), gastrin secretion is inhibited by gut hormones (secretin and somatostatin)
When digested food (chyme) passes into the small intestine, the duodenum also releases digestive hormones:
Secretin and cholecystokinin (CCK) stimulate the pancreas and liver to release digestive juices
Pancreatic juices contain bicarbonate ions which neutralise stomach acids, while the liver produces bile to emulsify fats
What are some of adaptations of villi?
Microvilli, rich blood supply, single layer epithelium, lacteals, intestinal glands, membrane proteins
Microvilli
Ruffling of epithelial membrane further increases surface area
Rich blood supply
Dense capillary network rapidly transports absorbed products
Single layer epithelium
Minimises diffusion distance between lumen and blood
Lacteals
Absorbs lipids from the intestine into the lymphatic system
Intestinal glands
Exocrine pits (crypts of Lieberkuhn) release digestive juices
Membrane proteins
Facilitates transport of digested materials into epithelial cells
What are the digestive enzymes?
Salivary amylase, protein/ protease, amylase, lipase, trypsin/ endopeptidase, nuclease
Where is the site of production for salivary amylase?
Salivary glands
Where is the site of action for salivary amylase?
Mouth/ esophagus
What are the substrates of salivary amylase?
Starch ( mauls )
What is the product of salivary amylase
Maltose
Where is the site of product for pepsin/ protease?
Stomach
Where is the site of action for pepsin/ protease?
Stomach
What is the substrate for pepsin/ protease?
Proteins
What is the product of pepsin/protease?
Peptides
Where is the site of production for amylase?
Pancrease
Where is the site of action for amylase?
Lumen of small intestine
What is the substrate of amylase?
starch
What are the products of amylase?
maltose
Where is the site of production for trypsin/ endopeptidase
Pancrease
Where is the site of action for Trypsin/ Endopeptidase?
lumen of the small intestine
What are the substrates of Trypsin/ Endopeptidase?
proteins/ peptides
What are the products of Trypsin/ Endopeptidase?
amino acids
Where is the site of production for lipase?
pancreas
Where is the site of action for lipase?
lumen of the small intestine
What are the substrates of lipase?
trigycerides
What are the products of lipase?
Monoglycerides/ fatty acids/ glycerol
Where is the site of production for nuclease?
Pancreas
Where is the site of action for nuclease?
lumen of small intestine
What are the substrates of nuclease?
nucleic acids
Simple Diffusion
Hydrophobic materials (e.g. lipids) are capable of freely
diffusing across the epithelial membrane
Facilitated Diffusion
Certain monosaccharides, vitamins and some minerals
may be transported by epithelial channel proteins
Secondary Active Transport
Glucose and amino acids are co-transported across the
epithelial membrane with sodium ions (Na+)
Endocytosis
Dissolved materials may be rapidly absorbed en masse via the process of pinocytosis (cell ‘drinking’)
How are amino acids digested?
Facilitated diffusion and active transport
Spell the bacteria that causes stomach ulcers
Helicobacter pylori
Proton Pumps
Proton pump inhibitors (PPIs) are drugs that irreversibly bind to the proton pumps and prevent H+ ion secretion
This effectively raises the pH in the stomach to prevent gastric discomfort caused by high acidity (e.g. acid reflux)
Individuals taking PPIs may have increased susceptibility to gastric infections due to the reduction of acid secretion
