digestion Flashcards
An adequate diet must supply what three needs
Chemical energy for cellular processes(ATP)
Organic building blocks for macromolecules
Essential nutrients
To meet the need for ATP, animals ingest and digest nutrients including
Carbohydrates
Proteins
Lipids
For use in cellular respiration and energy storage
what are essential nutrients
Essential amino acids, fatty acids, vitamins
Substances that an animal requires but cannot assemble from simple organic molecules
they can collect and synthesize all other forms of these compounds but the essential ones must be consumed to be obtained
All organisms require a standard ___ amino acids to make a complete set of proteins
20
Essential fatty acids
Used to regulate membrane fluidity
Synthesize a group of signaling molecules called eicosanoids
Also serve as source for ATP generation
Animals cant make double bonds → need from diet
Vitamins
Organic molecules that are required in the diet in very small amounts
Vitamin A deficiency
Night blindness → inability to see well in dim light
Regeneration of rhodopsin is incomplete
Retinal is derived from vitamin A
Maintaining homeostasis is important so that
so that glucose, amino acids, and fatty acids remain in interstitial fluid for cells to take up
Carbs, fats, and proteins are consumed via digestive tract
We can use them immediately or store the nutrients
Overall goals of the digestive tract
Take food and break it down to absorbable units
Digestion sends secretions that contain enzymes to break down big molecules in food
Move the absorbable units from the inside (lumen) of the digestive tract across the epithelial cell of the digestive tract wall and into the interstitial fluid
These are then taken up by the circulatory system for distribution
Food processing involves what steps
Ingestion, digestion, absorption, and elimination
the GI tract is lined with __ which is where nutrients and molecules must be able to pass through to get to the interstitial fluid
epithelial cells
food enters the digestive tract in
lumen of GI tract
cavity/inside of GI tract
tube
Ingestion
The act of eating or feeding
digestion
Food is broken down into molecules small enough for the body to absorb
Both mechanical and chemical processes are typically required
digestion mechanical and chemical
Mechanical→ chewing and grinding
Chemical → cleaves out large molecules into smaller components
Why is chemical digestion necessary
Animals cannot directly use the proteins, carbohydrates, nucleic acids, fats, and phospholipids in food
These molecules are too large to pass through cell membranes
When broken down into smaller components, the animal can use these products to assemble the large molecules it needs
Elimination
Undigested material passes out the digestive system
Absorbable units
Monosaccharides, amino acids, nitrogenous bases, sugars, phosphates, glycerol, fatty acids, monoglycerides → from the building blocks
Carbohydrates breakdown
steps
Start with polysaccharides
Salivary glands form salivary amylase
Turns bigger molecules smaller (smaller polysaccharides)
In small intestine pancreatic amylase breaks down larger molecules to disaccharides
intestinal epithelium enzymes turn disaccharides into monosaccharides
Protein breakdown
Start with Pepsin in the stomach that breakdown proteins to small polypeptides
In small intestine there are many enzymes from the pancreas that break down the polypeptides into small peptides
Small intestine will have dipeptides, aminopeptides, which break down to amino acids
Nucleic acid breakdown
Digestion takes place in small intestine where pancreatic nucleases break DNA and RNA into nuclleotides
Nucleotidases break nucleotides to nucleosides in small intestine
Nucleosidases and phosphatase break nucleosides to nitrogenous bases, sugars, and phosphates
Fat digestion
small intestine
take fat and break it down with pancreatic lipase to glycerol and fatty acids
Function of different parts of human digestive system
Mouth
Food is chewed and lubricated with saliva
Salivary amylase breakdown polysaccharides
what happens in the Oral cavity, pharynx, and esophagus
Swallowing causes epiglottis to block entry to the trachea, and the bolus is guided by larynx, the upper part of the respiratory tract
sphincter makeup and
sphincter movement when eating
Upper sphincter
Regulates passage of food into the esophagus and not the trachea
Lower sphincter
Opens to allow food to enter stomach
Esophageal sphincter is typically contracted to allow breathing and trachea to be open. When eating the sphincter is relaxed and the esophagus opens
Stomach
Smooth muscular bag
Stores your meal and then slowly release it into small intestine
In the stomach there is HCl that kills bacteria, denature macromolecules, and activate pepsinogen. There is also pepsin which starts the digestion of proteins
Where does HCl and pepsin in the stomach come from
Parietal cell sends HCl into your stomach
Sends hydrogen ions and chloride ions into your stomach
Chief cells secrete pepsinogen(inactive form of pepsin)
Enzyme that starts the digestion of other enzymes
why wouldn’t chief cells digest itself
it makes the inactive form of pepsin, pepsinogen and gets activated by the presence of HCl
Mucus
Secreted by the stomach’s mucous cells
Coats the walls of the stomach and protects it from being eroded and digested by HCl and pepsin
Ulcers
Mainly caused by bacteria in stomach that starts digesting stomach
Small intestine
where Digestion is completed and absorption takes place
made up of duodenum, jejunum, and ileum
duodenum
first portion of small intestine
Secretions from the gallbladder and pancreas enter the small intestine lumen here
Acid chyme from stomach and detergent-like bile from liver/gallbladder come together and enter duodenum
Pancreas
Send pancreatic juice with bicarbonate fluid to neutralize stomach acid
Also sends digestive enzymes with it to duodenum
Gallbladder
Sends detergent-like bile to aid on fat digestion; made in liver
Gallbladder stores bile because you only need it when you consume food
aid in fat digestion
Following the duodenum, the small intestine’s main job involves
the absorption of nutrients
the small intestine’s most absorption takes place in the
jejunum
jejunum
The longest section of the small intestine
Nutrients have to move across the epithelial cells that line the lumen
Small intestine is folded to increase surface area and allow for increased absorption
Last segment of the small intestine is
ileum
ileum function
Main function is to absorb vitamin B12, bile salts, and whatever products of digestion are remaining for absorption
Absorption
To absorb materials from the inside of the intestine, molecules need to travel across epithelial cells to the interstitial space and then get taken up by the capillaries for distribution throughout the body by the circulatory system
Villi and microvilli
function
Specifically looking for prticuar molecules to transfer across epithelial cekks
Villi and microvilli increase surface area to pull molecules in
Hepatic portal vein
Goes from one capillary in small intestine to the capillaries in the liver and then to the heart
Carries nutrient rich blood from the capillaries of the villi of the small intestine to the liver, then to the heart
The liver regulates nutrient distribution, interconverts many organic molecules, and detoxifies many organic molecules
how does lipase come about digsesting fat in the small intestine
When you eat fat they form fat globules
Bile salts break up large fat globules increasing exposure of triglycerides on the surface to hydrolysis
Triglycerides are broken down to fatty acids and monoglycerides by lipase
Lipase chews around the edges of fat droplets
Would take forever so bile breaks down fat globules to droplets
After diffusing into epithelial cells, monoglycerides and fatty acids reform into triglycerides
why are fats reformed into triglycerides
This is the form of fats that can be sent around the body
Triglycerides are combined with phospholipids, cholesterol, and proteins and formed into chylomicrons
Enter lacteals and are carried away by lymph
Chylomicrons are water soluble
Large intestine
Primary job is to make feces
All the secretions that were sent in the GI tract lumen in the stomach and small intestine were dissolved in water
Whatever hasn’t been taken up by small intestine
Water reabsorption takes place here
Regulation of digestion
We have periods of inactivity of our digestive system
Must be able to turn process on and off
what is it controlled by
hormones\
gastrin
CCK and secretin
gastrin
Produced by cells in the stomach wall
Sense arrival of food
Turns on gastric secretions
stimulates production of gastric juices
As stomach empties(chyme leaves), gastrin production goes down
gastrin signals digestion to begin
CCK and secretin
Presence of chyme in duodenum stimulates release of CCK which stimulates the pancreas to release HCO3- and enzymes and cause contraction of gallbladder to squeeze bile and aid in digestion of fat
Secretin reacts to drop in pH and thus neutralizes low pH from chyme that enters duodenum by secreting bicarbonate
CCK and secretin then inhibit gastric juices and stomach
Where do we store carbohydrates, fats,, abd proteins
As triglycerides in fat cells
Releases fatty acids back into circulation to feed other cells
Carbohydrates are found in the form of ___in liver and muscles
glycogen
How we maintain blood glucose
breakdown of glycogen
Insulin and Glucagon
Insulin
Beta cells in pancreas create insulin
Leads to transport of glucose from blood into body cells and storage of glucose as glycogen
lowers blood glucose concentration when the blood glucose level rises
Glucagon
Blood glucose level decreases
Glucagon is secreted by alpha cells of the pancreas
Glucagon signals the breakdown of glycogen and releases glucose into the blood
Diabetes
Elevated blood glucose, dehydration, poor circulation, acidosis
Type 1 diabetes
Doesn’t make insulin
Caused by destruction of insulin producing beta cells in the pancreas
Autoimmune disease
Type 2
Insulin is there but cells stop responding
Producing so much insulin that your cells become insensitive to insulin
Insulin is produced but target cells fail to take up glucose from the blood and the blood glucose level remains elevated
Regulating appetite
Satiety center in hypothalamus feels hunger
Ghrelin stimulates hunger between meals
Eating leads to an increase in insulin and PYY which act to decrease appetite
OB mouse was missing something that was turning off the satiety signal
Leptin
Leptin acts on your brain to decrease appetite
bolus
Mixture of saliva and food shaped into a ball
Each bolus of food is received by a throat region called the ___ which leads to what two passageways
Pharynx
Esophagus and trachea
Esophagus
Muscular tube that connects to the stomach
Trachea
Windpipe that leads to the lungs
Within the esophagus, food is pushed along by
Peristalsis
Alternating waves of smooth muscle contraction and relaxation
Upon reaching the end of the esophagus, the bolus encounters
A sphincter
A ringlike valve of muscle
Regulates passage of the ingested food into the next compartment→ stomach
The stomach, located below the diaphragm, has two major roles in digestion which are
Storage and to process food into a liquid suspension
The stomach secretes a digestive fluid called
Gastric juice
The mixture of ingested food and gastric juice is called
Chyme
What two components of gastric juice help liquefy food in the stomach
Hydrochloric acid and protease/pepsin
What two types of cells in the gastric glands of the stomach produce the components of gastric juice
Parietal cells and chief cells
How do more pepsinogen become activated
Pepsin can activate the remaining pepsinogen by clipping pepsinogen and exposing its active site → positive feedback
alimentary canal
same as GI tract
digestive tract
mouth to anus
The arrival of chyme in the duodenum triggers
Release of the hormone secretin which stimulates the pancreas to secrete bicarbonate
Bicarbonate neutralizes the acidity of chyme and acts as a buffer for chemical digestion in the small intestine
Bile production is metabolically linked to what other vital liver function
The destruction of red blood cells that are no longer fully functional
Pigments released during red blood cell disassembly are incorporated into bile pigments which are eliminated from the body with feces
In exiting the small intestine, chylomicrons first enter a
Lacteal
A vessel at the core of each villus
How is water reabsorbed
By osmosis when sodium and other ions are pumped out of the lumen of the small intestine
The alimentary canal ends with the
Large intestine which includes the colon cecum and rectum
Colon leads to the rectum and anus
Cecum
A pouch that has an important role in fermenting ingested material
The colon completes the recovery of water that began in the small intestine
leaves behind feces
The terminal portion of the large intestine is the
Rectum → where feces are stored before elimination out of the anus
