Digestion (Biology 20) Flashcards
4 steps in the digestive process
1) ingestion
2) digestions
3) absorption
4) egestion
4 main macromolecules needed to be broken down to micromolecules
1) carbohydrates – broken down to monosaccharides
2) proteins – broken down to amino acids
3) lipids – broken down to fatty acids and glycerol
4) nucleic acids – broken down to sugar, nitrogen bases, and phosphate group.
After the dashmarks are the sub units/building blocks. The body uses them to create its OWN macromolecules.
2 types of digestion used in actual digestion of food
(1) mechanical – chewing, as well as muscular contractions to grind food.
(2) chemical – enzymes, acids, and other chemicals.
4 things affecting enzyme’s work
1) Temperature ~ 37 degrees
2) pH ~ each enzyme functions best at a specific pH
3) concentration of substrates ~ chewing things increases surface area by breaking down large pieces into small pieces, letting enzymes work faster.
4) the use and removal of inhibitors on proteins.
Chemical digestion of carboydrates in mouth
salivary amylase turns polysaccharides into disaccharides.
Chemical digestion of carbohydrates in stomach
n/a
Chemical digestion of carbohydrates in small intestine
pancreatic amylase turns polysaccharides into disaccharides, and carbohydrases turn disaccharides into monosaccharides. (absorbed into capillaries in the villi)
Common macromolecules
1) carbohydrates
2) lipids
3) proteins
4) nucleic acids
Dehydration synthesis
Joining two smaller subunits (molecules) with the removal of water. You remove an OH- group from one subunit, and H+ group from another, resulting in the macromolecule and H2O. The process relies on special enzymes.
Hydrolysis
Used to break these macromolecules. It is done by adding an H2O molecule and breaking the covalent bond formed during dehydration. Also requires special enzymes.
How are simple carbohydrates used?
they are taken to the liver where they are converted to glucose or stored as glycogen.
How are amino acids used?
they are used by cells to build protein molecules for your body, or can be sent to the liver for deamination.
How are lipids used?
they are broken down to glycerol and fatty acids.
Monosaccharide
made from single, simple sugar.
Ex: glucose, fructose.
Disaccharide
made from two simple sugars bonded together.
Ex: sucrose (glucose + fructose), lactose (glucose + galactose)
What happens to excess glucose/glycogen in the liver?
it is converted and stored as fat.
Triglycerides
made of 1 glycerol and 3 fatty acids. (in animals called fat and in plants called oil)
- fats (animal) are classified as:
a) saturated - single bonds between carbon in molecules {bonds are difficult to break} - oils (plants)
b) unsaturated - have one or more double bonds between carbon (polyunsaturated – many double bonds) {double bonds are easily broken}
Phospholipids
made of 1 glycerol, 2 fatty acids, and 1 phosphate molecule
- phosphate molecules are soluble in water, so this makes one end of the lipid chain soluble in water and the other insoluble
- since blood is 90% water, phospholipids allow the cells in the blood (RBC, WBC, platelets) to mix and move freely. The insoluble middle layer acts as a barrier so that organelles in the cell do not move outside and to control what moves inside the cell.
Waxes
- insoluble to water
- coating on leave, fur, and animal feathers
How much more energy do fats contain over carbohydrates or proteins?
2x the amount
Why is saturated fat worse for your health?
they are difficult to break down, so they remain in your cells for longer.
Ingestion
taking in of nutrients
Digestion
breaking down of nutrients ingested into their component molecules
Absorption
absorption and transport of digestive nutrients to body tissues.
Egestion
removal of waste
What taste buds are in which parts of the tongue?
bitter = back sour = back corners (left+right) sweet = right mid-front salty = left mid-front
How long does food remain in the stomach?
2-4 hours
How long does digestion take?
up to 24-33 hours
How much saliva can an adult produce in a day?
as much as 2L of saliva a day!
Salivary glands
produce saliva
Epiglottis
a sphincter that covers your trachea when swallowing
Plyoric sphincter
a sphincter between the stomach and the duodenum.
Esophogeal sphincter
a sphincter preventing gastric contents to come back up to the esophagus.
Anal sphincter
a sphincter that controls the release of stool.
Appendix
a pack like tissue that holds bacteria used to recolonize the intestines after illness that wipes away bacterial colony (like diarrhea)
Liver
- The liver’s main job is to filter the blood coming from the digestive tract, before passing it to the rest of the body.
- The liver also detoxifies chemicals and metabolizes drugs.
- As it does so, the liver secretes bile that ends up back in the intestines.
Gallbladder
stores bile produced by the liver
Large intestine/colon/large bowel
it mainly removes as much water and electrolytes as possible, forming stool.
Rectum
The rectum is a straight, 8-inch chamber that connects the colon to the anus. The rectum’s job is to receive stool from the colon, let you know that there is stool to be evacuated (pooped out) and to hold the stool until evacuation happens
Esophagus
transports material from the mouth to the stomach
Stomach
stores and digests food through HCl and muscle contractions.
Pancreas
Enzymes, or digestive juices, are secreted by the pancreas into the small intestine. There, it continues breaking down food that has left the stomach. The pancreas also produces the hormone insulin and secretes it into the bloodstream, where it regulates the body’s glucose or sugar level.
Small intestine/small bowel
absorb most of the nutrients from the chyme. Divided into three parts, duodenum, jejunum, ileum.
Peristalsis
Peristalsis is a series of wave-like muscle contractions that moves food to different processing stations in the digestive tract.
Chyme
the pulpy acidic fluid which passes from the stomach to the small intestine, consisting of gastric juices and partly digested food.
Bolus
ball-like mixture of food and saliva that forms in the mouth during the process of chewing
Spleen
Your spleen’s main function is to act as a filter for your blood. It recognizes and removes old, malformed, or damaged red blood cells. When blood flows into your spleen, your spleen performs “quality control”; your red blood cells must pass through a maze of narrow passages.
Why are feces reddish brown?
Because the RBC’s at the end of their life cycle are sent there from the spleen where their iron is salvaged, and the pigment from the ingested food coming in contact with the RBC’s stays until the end of digestion. The RBC’s don’t get digested, though.
What percent of nutrient absorption happens in the small intestine?
90%
Villi
Hair like projections in the small intestine that increase surface area to increase nutrient absorption.
Microvilli
Hair like projections on the villi that increase surface area to increase nutrient absorption.
Where is most water absorbed in the digestive system?
The large intestine/colon.
How are nutrients absorbed in the villi?
Each villus is supplied with a capillary network that is intertwined with lymph vessels called lacteals. Absorption is mostly done by active transport, although some nutrients can move into the blood by simple diffusion.
Enzymes
Protein catalysts.
Substrates
molecules that enzymes work on. Only select enzymes work on select substrates.
Chemical digestion/enzymes in the mouth
salivary amylase turns polysaccharides to disaccharides
Chemical digestion/enzymes in the stomach
n/a
Chemical digestion/enzymes in the small intestine (general)
pancreatic amylase turns polysaccharides to disaccharides. Carbohydrases turn disaccharides to monosaccharides. (absorbed into capillaries in the villi)
Protein digestion process/enzymes
- no chemical digestion until stomach (mouth is mechanical)
- in the stomach, an inactive enzyme is stored in the gastric pits
- gastric juices are secreted when the bolus reaches the stomach
- contains HCl, mucous, and pepsinogen
Pepsinogen + HCl = pepsin -> pepsin turns polypeptides to peptones.
Small intestine digestion process/enzymes (duodenum)
trypsinogen + chemotrypsinogen + enterokinase = trypsin + chemotrypsin.
(trypsinogen and chemotrypsinogen created in pancreas, and enterokinase created in small intestine)
the trypsin and chemotrypsin turn peptides into amino acids with the help of an enzyme called peptidase. The amino acids are absorbed into capillaries.
Lipid digestion process/enzymes
- chemical digestion starts at small intestine
- bile is secreted into small intestine from gallbladder
- the bile emulsifies lipids (breaks down large lipid molecules into small droplets to increase surface area)
- pancreatic lipase turns lipids into glycerol and fatty acids, which are absorbed by lacteals (lymphatic vessels in the villi)
Nucleic acid digestion process/enzymes
-don’t get worked on until small intestine
- nucleases break nucleic acid into…
sugar, phosphate group, and nitrogenous bases.
These are absorbed in capillaries.
Duodenum
- First part of small intestine
- enzymes are release here.
- The majority of chemical digestion occurs here.
Jejunum
- second part of small intestine
- some chemical digestion
- mostly absorption
Ileum
- third part of small intestine
- last chance to absorb nutrients
Carbohydrases
digest carbohydrates (poly and disaccharides to monosaccharides)
Lipases
digest lipids to glycerol and fatty acids
Proteases
digest proteins to amino acids
Nucelases
digest nucelic acids
What is the stomach’s pH?
Because of the gastric juices, it begins at 1 - 2, but the pancreas also produces sodium bicarbonate to neutrialize the acid of stomach to make fluid alkaline. That gives the small intestine a pH of 9 - 8.
What enzymes that we have talked about, does the Pancreas create
In total, it makes around 28 different enzymes in its pancreatic juice. These include pancreatic lipase, pancreatic amylase, trypsinogen, chymostrysinogen, peptidases, carbohydrases, nucleases.
Enterokinase (creation location and purpose)
Used to convert and get active trypsin and chymotrypsin, and is created in the microvilli of the intestine.
Three control mechanisms of digestion
Sensors, mechanical, and hormonal.
Gastrin (control hormone)
- hormone released into blood when partially digested food enters the stomach
Enterogastrone (control hormone)
- released when fats enter small intestine.
- slows down peristalsis so there is more time to digest fats, as they are difficult to digest
Secretin (control hormone)
- release of bile salts is under control of secretin.
- secretin is released by the duodenum to protect it from acidic chyme by stimulating the release of a buffering agent.
- it is released through the bloodstream when chyme enters the small intestine.
- it is then carried the the pancreas, which is then signalled by to release bicarbonate ions to buffer the HCl in chyme (pH raised from <2,5 to 9.0)
- pepsin is made inactive in the alkaline fluid of small intestine.
Rennin (control hormone)
- slows movement of milk through the digestive tract so that nutrients can be absorbed
- works in alkaline environment, so combines with milk in the stomach and produces its effect in the small intestine.
CCK (cholecystokinin) (control hormone)
- released by cells in small intestine mucosal membrane into the duodenum
- causes the release of digestive enzymes from pancreas and bile from the gallbladder
- inhibits stomach movements and secretions with the presence of fatty foods to allow food to stay in system longer and be digested.
