Digestion Flashcards
What is digestion
The chemical and physical breakdown of food into small soluble molecules
What is absorption
The taking into the body of specific compounds
What is elimination
The expulsion of materials not absorbed into the body. Excretion, not including urine
What is the 10 step pathway of food
1) oral cavity
2) pharynx
3) epiglottis
4) esophagus
5) stomach
6) duodenum
7) small intestine
8) large intestine (+ appendix)
9) rectum
10) anus
What are the 3 main accessory organs and their main function
1) liver, makes bile
2) gall bladder, stores bile
3) pancreas, makes some enzymes
What do the substances made in the accessory organs drain through
The common bile duct
What is salivary amylase
A neutral enzyme produced by the salivary glands that dissolves starch into maltose (disaccharide)
What is pepsin
An acidic enzyme produced by the stomach that digests proteins into peptides
Secreted as inactive pepsinogen, turned to pepsin by low pH
What is pancreatic Amylase
A basic enzyme produced by the pancreas that digests starch into maltose
What is trypsin
A basic enzyme produced by the pancreas that digests peptides into smaller peptides
What is lipase
A basic enzyme produced by the pancreas that digests fat into glycerol and fatty acids
What are the peptidases
Multiple basic enzymes that are produced by the small intestine that digest peptides into amino acids
What is maltase
A basic enzyme produced by the small intestine that digests maltose into glucose
What is nuclease
A basic enzyme produced by the small intestine and pancreas that digests nucleic acids into nucleotides
What is Diomedea exulans
The wandering Albatross
What needs to be formed in the mouth prior to swallowing
A bolus (food ball) made by mouth, teeth, tongue, and saliva
While swallowing how does the esophagus move the bolus to the stomach
Through peristalsis, a rhythmic contraction of the esophagus and intestine which runs along the tube and pushes food material in one direction
What is saliva
A mixture of water, mucus, and enzymes like salivary amylase
What are the three functions of saliva
Lubricates food
Forms the bolus
Salivary amylase digests starch
What controls the digestive juice
The nervous system and endocrine system (hormones)
What are gastric juices made of
Water, pepsinogen (inactive enzyme pepsin), and hydrochloric acid (HCl)
What cells secrete pepsinogen
Chief cells
What cells secrete HCl
Parietal cells
What are the 4 functions of gastric juices
Lowers pH
Pepsin (activated by low pH) digests large proteins to small amino acid chains (peptides)
Food becomes semi-liquid acid chyme
Kills bacteria
What hormone causes the stomach to release juices
Gastric
What can excess acid lead to
Ulcers
What does the pancreas release into the duodenum
Pancreatic juices
Sodium bicarbonate
4 main enzymes
What does sodium bicarbonate do in the small intestine
It acts like a buffer to neutralize the stomach acid bringing the ph to around 7.5 (slightly basic)
What are the four enzymes release by the pancreas + functions
- pancreatic amylase (digests starch)
- trypsin (digests peptides)
- lipase (digests lipids)
- nuclease (digests DNA + RNA to nucleotides)
What 2 hormones control the pancreatic juices
CCK (Cholecystokinin)
Secretin
How long does it take the stomach to empty
2-6 hours
What is absorbed directly by the stomach
Alcohol
Aspirin
Candy
Etc
How long is the small intestine
Roughly 6 m
What is the duodenum
The first 20-25 cm of the small intestine
What 4 main enzymes are produced in the small intestine + functions
Maltase (maltose -> glucose)
Peptidases (Small peptides -> amino acids)
Nucleases (DNA/RNA -> nucleotides)
Lactase (lactose -> glucose)
What happens to the monomers after enzymatic digestion in the small intestine
They are absorbed into the blood
What are trophic levels
Essentially levels of consumption in an ecosystem
Ex producers
Primary consumers
Secondary consumers
Etc
What is bile
A product produced by the liver, stored in gall bladder that enters the duodenum
A chemical with salts that digests fats making it easier for lipase to work on them
What cells produce insulin
Islets of langerhans
What does insulin do
Acts on the cell membranes opening the protein gates In the membrane to slow glucose to enter from the blood
What are the effects of insulin
Lowers blood sugar
Stimulates liver and muscles to convert glucose to glycogen and promotes formation of fats and proteins
What other hormone is produced by the islets of langerhans
Glucagon which increases blood glucose levels
What connects the intestine to the liver
The hepatic portal vein
What does the hepatic portal vein do
Carries blood rich in food to the liver, which gate keeps circulation to keep levels of food constant
What does bile do
Breaks down fluid of hemoglobin
Emulsifies fats
Breaks down fat drops into tiny homogenous droplets
Stay in suspension
Increases surface area of fat drops for lipase to work on
What is the 1st function of the liver
Removes poisonous substances to detoxify blood
What is the 2nd function of the liver (related to glucose)
Stores glucose in the form of glycogen, which is converted back to glucose when blood sugar is low
What is the 3rd function of the liver (related to RBC)
Destroys old red blood cells (removes bilirubin + excretes into bile)
Converts hemoglobin to bile
What is bilirubin
A breakdown product of hemoglobin
High amounts can cause jaundice
Due to RBC breakdown
What does the liver do with amino acids
Produces urea from breakdown of amino acid. Urea is nitrogenous waste that is remove in urin
What is the 5th function of the liver (related to proteins)
Make blood proteins like albumins and fibrinogen from deamination (breakdown of amino acids)
What is gluconeogensis
when the liver Converts amino acids to glucose if necessary (gluconeogenesis)
What is the 7th function of the liver (related to cholesterol)
Regulates blood cholesterol levels, converts to bile salts
What is the 8th function of the liver
Stores iron and vitamins A,D,E,K, + B12
What is the 9th function of the liver
The wandering albatross
How long is the small intestine
6m
What are the 3 parts of the small intestine
Duodenum
Jejenum
Ileum
How long is the duodenum
20-25cm
How long is the jejenum
The wandering albatross
What are the two notable parts of the stomach
Cardiac sphincter (start gate)
Pyloric sphincter (end gate)
What is the most important function of the small intestine
It absorbs the monomers created by digestion
What is the secondary function of the small intestine
It uses enzymes to complete the digestion of macromolecules
How is the intestinal wall evolved to increase surface
It is highly convoluted and covered in villi that give it a huge surface area
What are villi
Tiny finger like projections that give the intestine a large surface area for absorption
Take in the monomers from digestion and pass them into circulation
What is the structure of villi
Outer area made of columnar and goblet cells, has blood venules and arterials (part of circulation), and lymphatic vessels which have branches called lacteals which reach into the projections, also lymph nodes
What do goblet cells do
Produce mucus
What do columnar cells do
Absorb monomers into villi, active transport
Where are sugar and amino acids absorbed to
Capillaries
Where are glycerol and fatty acids absorbed to
Lymph lacteals
What does the Hepatic Portal Vein do
Transport nutrients to the liver then back to the circulatory system at the subclavian vein: fats and cholesterol have direct route to the heart
What does the large intestine include
Appendix, colon, rectum, and anus
What are the three parts of the colon
Ascending colon, transverse colon, and descending colon
What is the colon
4/5 of the large intestine, reabsorbs water and some salts, holds a population of E.coli which digests indigestible material to produce gas, amino acids, vitamins, and growth factors (proteins that stimulate cell growth)
What is diabetes
When the liver cells are unable to take up or metabolise glucose
What is type 1 diabetes
Insulin dependant
Pancreas not producing insulin
May be caused by a virus causing cytotoxic T cells to destroy the pancreatic cells (islets of langerhans)
How can you control Type 1 diabetes
Daily insulin injections control the symptoms of hyperglycemia
Sugar cubes or fruit juices can help resolve diabetic attacks
What is type 2 diabetes
Non-insulin dependant
Can occur at any age due, obesity and inactivity can contribute
Pancreas produces insulin but liver and muscles cells do not respond in usual manner
May be do to lack of protein receptors to bind to insulin
How can you control type 2 diabetes
Low fat, low sugar diet, regular exercise or oral drugs to stimulate the pancreas to up insulin production
What are enzymes
Proteins that speed up chemical reactions
Essential for al reactions on cells
What is metabolism
The total rate of all chemical reactions in a cell body
What are substrates
The starting chemicals the enzyme works on, starting compounds, reactants, specific to an enzyme
What are the two types of substrates
Those that release energy: Exergonic
Those that absorb energy: Endergonic
What do enzymes lower
The activation energy (Ea)
Energy needed to begin a chemical reaction
What is the Ea with an enzyme of most human reactions
37 degrees Celsius
What is thyroxin
A hormone that is produced by the thyroid gland (neck) that controls the metabolic rate of all the cells in the body. more thyroxin = higher rate of metabolism
What does more thyroxin do
Increase metabolic rate along with consumption of oxygen and sugar.
It attaches to proteins on nuclear membrane cause activation of genes which produce metabolic enzymes
What factors affect thyroxin production
Iodine consumption: more = more
Age: more = less
What are the two main types of reaction an enzyme helps with
Synthesis and degradation
What is the induced fit model
Enzymes have an active area the substrate enters
The enzyme changes shape slightly to bind to substrate
Substrate is converted to products before released
What is a coenzyme
A smaller non protein that activates n’a enzyme (usually a vitamin)
Some like pepsinogen need a certain pH or temp to activate, pepsin is activated by pH 1-2
What role do vitamins play
They usually act as co-enzymes to activate enzymes and make them more effective. Deficiencies of vitamins stop vital pathways and cause diseases
What are competitive inhibitors
A molecule that mimics a substrate and fits into the active site to stop the enzymes ability
Compete with active site with substrate
What are some example of inhibitors
Carbon monoxide
Hydrogen cyanide
Nerve gas
What do competitive inhibitors do
Some are temporary and control the enzymes function. Pause button
Others are just poisons
What are allosteric sites
Secondary sites non competitive inhibitors can bind to to regulate metabolic pathways
What can happen if temp and pH are too high
The enzymes R group bonds can break and the enzyme can denature, and lose its activity and function
How does pH affect enzymes
Certain enzymes work best at a specific pH. Changes from that level can denature
How does temp affect enzymes
37 is ideal for human enzymes, above 40 causes them to denature. At low temp the substrate and enzymes move slower and collide less, reduce rate of reaction
What can exposure to heavy metals do to enzymes
Denature them
How does substrate concentration affect enzymes
Increases reaction as long as enough enzyme is present, once it’s too high the enzyme will be overwhelmed and the reaction level will level off. At this point more enzyme is needed
What is hypothyroidism
Secretion of low amounts of thyroxine
Don’t burn glucose as effectively
Causes symptoms like low energy, intolerance to cold, dry skin, and weight gain
What is hyperthyroidism
Too much thyroxine produced
Sugar oxidizes faster
Symptoms include eating a lot but no weight gain
