Niyogi Lectures 8-11 Flashcards
Macro vs micro nutrients
Macro-nutrients are required in large amounts
Micro-nutrients are required in small amounts
Define essential nutrients
nutrients animals cannot synthesize themselves and must acquire from food
e.g. essential amino acids, essential fatty acids, vitamins and minerals
What are the essential amino acids, fatty acids and vitamins in humans?
Of the following vitamins, which are water soluble and which are fat soluble?
A, B1, B2, B12, Biotin, C, D, E, Folic acid, K, Niacin, and Pantothenic acid
Carbohydrates can be categorized into monosaccharides, disaccharides, and polysaccharides. What sugars are defined under each?
Mono:
Glucose, fructose, and galactose
Di:
Sucrose, Trehalose, Maltose, Lactose
Poly:
Chains of interconnected monosaccharides (starch from plants and glycogen in animals)
Cellulose
Define proteins
Consists of various combinations of amino acids held together by peptide bonds
Bulk of dietary lipids are ____________, but also contain phospholipds, cholesterol, and fat-soluble vitamins.
Triglycerides (glycerol + fatty acids)
What is a calorie (cal)?
A unit of energy defined as the amount of energy needed to raise the temperature of one gram of water by one degree C at a pressure of one atmosphere
How are bonds broken down in the digestive system?
enzymatic hydrolysis, which is the addition of H+ and OH- from water
Digestion is driven by specific enzymes. What do each enzyme react with?
Amylases
Lipases
Proteases
Nucleases
Amylases: starch
Lipases: fats and other lipids
Proteases: proteins
Nucleases: nucleic acids
Is digestion in the digestive tract intracellular or extracellular?
extracellular
What is an animal that uses intracellular digestion?
What is the difference between a gastrovascular cavity and a gastrointestinal tract?
The main difference between these two is that the gastrovascular cavity has only one opening, and a complete digestive system has two openings (one starts from the mouth and ends at the anus).
What is the evolutionary significance of extracellular digestive systems?
A one-way digestive system allows the evolved animal to digest food more efficiently.
Extracellular digestion overcomes the limitations of intracellular digestion by breaking up larger pieces of food into smaller particles. Its evolution has thus allowed animals to feed on large organisms and has widely expanded available food resources.
Intracellular digestion is limited by lysosome availability and can only digest small particles.
Define each and give examples.
Fluid feeders
Suspension feeders
Deposit feeders
Bulk feeders
Fluid feeders: ingest liquids containing organic molecules (tape worms, mosquitos, insects, birds, bats)
Suspension feeders: eat small particles or organic matter or small organisms in suspension in fluids (mussels, whales)
Deposit feeders: ingest small organic particles from solid matter that feeders live in or on (earthworm, fiddler crab, polychaete worm)
Bulk feeders: consume large pieces of organisms, or entire large organisms (most animals)
Why must tapeworms eat food that has already been digested by another animal?
Tapeworms have no digestive tract, as they are fluid feeders. As a parasite inside animals intestines, they absorb nutrients directly by diffusion across their skin (cuticle).
Describe the digestive system of the deposit feeder earthworm.
The digestive system is divided into many different regions, each with a certain function. The digestive system consists of the mouth, esophagus, the crop, the intestine and the gizzard. The gizzard uses stones that the earthworm eats to grind the food completely.
Describe the digestive system of a grasshopper using the terms foregut, midgut, and hindgut.
Foregut: mouth and salivary glands, esophagus, crop, gizzard
Midgut: chemical digestion takes place in the stomach and 6 pairs of gastric ceca extending from stomach, digestion aided by bacteria
Hindgut: coiled structure consisting of anterior ileum, middle colon and posterior rectum, and anus
Describe the digestive system of a pigeon.
The ‘canal’ includes the oral cavity, esophagus (which includes crop in some birds), stomach (proventriculus, glandular portion of the stomach, and gizzard), small intestine and large intestine.
It has also important accessory structures including the beak, salivary glands, liver, and pancreas.
How are carnivore’s digestive systems adapted to their diets?
Carnivores have greatly enlarged stomachs, which secrete powerful digestive enzymes along with 10 times more HCl than a herbivore
How are herbivore’s digestive systems adapted to their diets?
Herbivores have long digestive tracts because it takes a long time to absorb nutrients from the plant material which they eat. They also have a large caecum (a pouch connected to the junction of the small and large intestines) which helps along with enzymes to breakdown the plant material and cellulose.
Mammals can be classified by the type of stomach they have. Define monogastrics and ruminants.
Monogastrics: non-ruminants have simple, single-chambered stomachs such as humans, swine, rabbits and horses
Ruminants: have four-chambered complex stomachs– such as a cow, goat, or sheep
Describe the structure of the stomach in monogastrics.
Glands in the stomach wall secrete gastric juices with 0.2-0.5 HCl. The stomach muscles mix and squeeze the food and forces the chyme to go into the small intestine.
Describe the structure of the stomach in ruminants.
Has 4 chambers (rumen, reticulum, omasum, and abomasum)
Ferments food prior to digestion through microbial actions that digest cellulose. Note this uses A LOT of water.
What are the five stages of digestion in animals with a GI tract?
(1) Mechanical processing
(2) Secretion of enzymes and other digestive aids into the digestive tract
(3) Enzymatic hydrolysis of food molecules into molecular subunits
(4) Absorption of molecular subunits across cell membranes
(5) Elimination of undigested matter
Define alimentary canal.
the whole passage along which food passes through the body from mouth to anus. It includes the esophagus, stomach, and intestines
Mouth, pharynx, esophagus, stomach, small intestine, and large intestine
What are the accessory digestive organs used in mechanical and chemical digestion?
Teeth, tongue, salivary glands, liver, gallbladder, and pancreas
The gastrointestinal tract is comprised of four layers. Name these layers from the deepest to the most superficial and their functions.
(1) Mucosa: the innermost layer that is surrounding the lumen. It is responsible for protection, secretion, and absorption.
(2) Submucosa: areolar connective tissue that binds mucosa to muscularis
(3) Muscularis: skeletal muscle (involved in voluntary swallowing and voluntary control of defecation) and smooth muscle (involved in the break down of food and mixing it with digestive secretions)
(4) Serosa: serous membrane of areolar connective tissue and simple squamous epithelium
The Mucosa consists of…
the epithelium, lamina propia (connective tissue), and muscularis mucosae (a thin layer of smooth muscle)
Salivary amylase, secreted from the salivary glands in the mouth, digest…
starch
Saliva is a specialized mucus. What is it’s function?
acts as a softener or lubricant
Salivary lipases aid in
triglyceride digestion
List the events that occur with the swallowing reflex using the following terms:
bolus, pharynx, esophagus, stomach, epiglottis, pharyngeal and esophangeal
Food mass (bolus) is swallowed through the pharynx and esophagus to the stomach. In this process the epiglottis blocks the trachea
Swallowing involves both voluntary (oral) and involuntary (pharyngeal and esophageal) phases
What is peristalsis?
Involuntary contraction and relaxation of the muscles of the GI tract.
Coordinated contractions of circular and longitudinal muscles produces peristaltic waves that move digestive contents from mouth to anus
What is chyme
combination of food and acid/enzymes in the stomach
What fluids does the stomach release to aid digestion? GPIG
(1) Gastric juice that contains HCl, which causes the stomach to have a high acidity with a pH of about 2. This kills most bacteria present in food.
(2) Pepsin: begins the digestion of proteins
(3) Intrinsic factor: aids in absorption of Vitamin B12
(4) gastric lipases (acidic lipase): aids in digestion of triglycerides
True or false? HCl digests food.
False. Although HCl does not digest food, it does break down the connective tissue of meat and activates pepsin.
Smell and taste of the food stimulate the autonomic nervous system, and thus…
stimulating the secretions in the stomach lining
Mechanical and chemical receptors indirectly trigger stomach secretions.
How long is the small intestine?
6 metres
True or false? The small intestine has a large diameter to pass more food.
False; small diameter
The intestine is slightly basic/acidic.
basic
Describe the structure of the small intestine.
In the small intestine there are projections that increase the surface area for nutrient absorption. Describe the structure of said projections.
The wall of the intestine contains projections called villi (or a villus).
The outer layer of each cell of each villus has thousands of microvillus.
Villi contain blood and lymphatic capillaries.
The surface area of the small intestine is about that of a __________
tennis court
The small intestine also secrete fluids to aid digestion. What is it called? What are they composed of? How much is secreted?
The slightly alkaline Intestinal juice is composed of: water and mucus, as well as brush-border (microvilli) enzymes that digest carbohydrates or proteins.
In the duodenum, digestive juices from the pancreas and liver add enzymes and digestive aids to the food mass. What are they called and what do they break down?
Pancreatic juice contains:
- Digestive enzymes (amylase, proteases, lipase)
- HCO3- ions to neutralize acidity
Liver secretion (bile) emulsifies fat with:
- Bile salts
- cholesterol
- Bilirubin
- additional bicarbonate ions
What is the purpose of the gallbladder in digestion?
stores bile which is eventually secreted in the duodenum to break down fat
The lumen and epithelial cells of the small intestine each secrete enzymes for digesting carbohydrates, proteins, fats, and nucleic acids. Using the key terms match the enzyme to the secretory tissue and function.
Keywords: pancreatic amylase, pancreatic nucleases, trypsin, chymotrypsin, carboxypeptidase, disaccharidases, amino peptidase, dipeptidase, lipase, nucleotidases, nucleosidases, phosphatases
How are water-soluble nutrients absorbed in the small intestine?
How are fat-soluble nutrients absorbed in the small intestine?
Micelles (fats coated with bile salts) are digested to monoglycerides and fatty acids, which penetrate into cells and are assembled into fats. The fats are coated with protein to form chylomicrons, which are released by exocytosis to extracellular fluids, where they are picked up by lymph vessels.
How are fat-soluble vitamins and cholesterol absorbed in the small intestine?
When a micelle contacts the plasma membrane of a mucosal cell, the hydrophobic molecules within the droplet fuse and penetrate the membrane and enter the cytoplasm
In mucosal cells, fatty acids and monoglycerides are recombined into tryglycerides and packaged into chylomicrons. Cholesterol absorbed in the small intestine is also packed into the chylomicrons. What are chylomicrons?
small droplets covered by a protein coat, which is a hyrdophilic surface that keeps the droplets suspended in the cytosol
After monoglycerides, fatty acids are packed into chylomicrons and cholesterol is absorbed in the mucosal cells, what happens to them?
After travelling across the mucosal cells, the chylomicrons are secreted into the interstitial fluid of the submucosa where they are taken up by the lymph vessels and transferred into the blood stream
Many nutrients that are absorbed by the small intestines are processed by the liver. How does this occur?
Some nutrients leave the blood stream and enter the liver cells for chemical processing
Describe the hepatic portal system.
Capillaries absorbing nutrients in the small intestine collect into veins that join to form the hepatic portal vein.
From here the blood is transfered to arterioles and then arteries or
to a larger blood vessel that leads to capillary networks in the liver
Describe the structure of the large intestine using the following terms:
cecum, appendix, colon, and rectum.
What is the function of the large intestine and what are its secretions?
Secretes mucus (protection and lubrication) and HCO3- ions (main protective mechanism for the intestinal mucosal barrier)
Absorbs water and other ions (mainly Na+ and Cl-)
At the end of the large intestine, undigested remnants (feces) are expelled from the anus
As many as 500 species of bacteria live in the intestine and make up 30-50% of the dry matter of feces. Escherichia coli is the most common in humans and other mammals.
What are two products of these bacteria?
Produce useful fatty acids and vitamins such as vitamin K, the B group vitamins (folic acid and biotin) some of which are absorbed in the large intestine.
Produces large quantities of gases including CO2, methane, and hydrogen sulfide
