BIOL 103 Lecture Notes - Gastrovascular Cavity, Gastrointestinal Tract, Fluid Compartments

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Published on 22 Apr 2013
School
Queen's University
Department
Biology
Course
BIOL 103
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of 4
Biology Lecture #2 The Digestive System
Topics to be covered, fluid compartments, nutrition, digestion and absorption
Fluid Compartments
Intracellular fluid
Extracellular fluid, which includes plasma and interstitial fluid
Movement occurs between compartments
Passive diffusion
Largely non-polar molecules such as lipids
Facilitated transport
Moves down concentration gradient, but cannot pass barrier by themselves, needs aid of
transport protein
Active transport
Moves against concentration gradient via an unenergetically favourable way which is what
makes it an active process
Osmosis how water moves through membranes and is dependent on concentration of solute
Isotonic Solution when concentration of solute inside is same as outside
Hypertonic Solution lower concentration inside, fluid moves outside
Hypotonic Solution - higher concentration inside, fluid moves in
Nutrition
Divided into two main categories
Autotrophs self nutrition
Organisms that harvest energy from light or chemical energy (eg. Plants)
Heterotrophs other nutrition
Organisms that must get their nutrients from the environment such as by eating other
organisms
Nutrients organic molecules
Carbohydrates
Proteins
Lipids
Vitamins
Nucleic acids
Inorganic nutrients (not found in body)
Minerals (such as zinc)
Phases of the digestive process
Phases of digestion for an animal
Ingestion where food is consumed (eg. Mouth)
Digestion where nutrients are broken down (eg. Stomach)
Absorption ions, water and small molecules (eg. Large and small intestines)
Elimination waste excretion, anything that wasn’t absorbed (eg. Anus)
Extracellular Digestion
Allows for cells to digest organisms larger than itself (such as the bacteria hydra)
Digestive enzymes are secreted into the gastrovascular cavity, and the resulting nutrients are
absorbed by phagocytosis
Wastes are then excreted outside of the mouth
Intracellular Digestion
Phagocytosis cellular process of engulfing solid particles by cell membrane
Membrane surrounds particle, forming a small vacuole which then pinches off
Lysosomes fuse with vacuole and empty their enzymes onto the ingested material
Organisms that are more complex have an alimentary canal with openings at both ends
Anterior End (ingestion) oral cavity, salivary glands, pharynx, esophagus
Middle Portion (storage and initial digestion) stomach, small intestine and associated organs
such as liver, gallbladder and pancrease
Posterior Part (final digestion, absorption and elimination) reminder of small intestine and the
large intestine
Teeth accessory structures
Teeth of a carnivore that consumes whole pray long teeth to pull prey in and large jaw to
consume prey
Terrestrial carnivore canines and molars to mechanically break down flesh
Teeth of a terrestrial herbivore mostly flat molars where they can grind down cellulose in plant
material into fine pulp
Cropping teeth of a marine algae eater grabbing food items to get into mouth
Terrestrial omnivore balanced approach, some good for grinding whereas some others for
ripping apart muscle
Oral Cavity
Saliva has many functions, to moisten and lubricate food to help swallow, dissolve food particles
for taste and lastly to kill ingested bacteria
Also initiates chemical digestion of polysaccharides with amylase (not impotant for test, exams)
Adaptations for herbivory have ruminants such as being able to digest cellulose
Forestomach plant churns around here, and there are enzymes and bacteria which breaks
down cellulose so it can be ingested
Cellulase are able to break down cellulose and is a symbiotic relationship, it helps break down
cellulose for the organism while being able to have the necessities for being able to survive
themselves
Alimentary canal in birds
Have no teeth so they can’t grind feed
Esophagus moves feed by peristalsis
Crop, a dilation of esophagus that stores and moistens food
Two parts of stomach, Proventriculus which secretes acid and enzymes, and the Gizzard which
contains tiny pebbles which help break down food
Intestine which digests and absorbs food
Cloaca which receives undigested material for excretion
The Human Stomach
As soon as food enters the stomach, gastric juice is secreted which is a combination of HCl and
an enzyme called pepsin
Pepsin is a protease (breaks down proteins and requires water) and is active at an acidic pH
of 2
Small Intestine
Contents of the stomach, which is acid chime are passed on to here where there is a large
number of digestive enzymes that are produced by
The intestinal glands maltase and proteases
Pancreas proteases, pancreatic amylase (starch -> maltose), lipase (fats - > fatty acids and
monoglycerides), bicarbonates (acid-base buffer system)
Liver bile, acts as emulsifier (large fat dropelts -> smaller ones)
Liver - produces bile, moves to gallbladder where it is stored until needed
Pancreas secretes enzymes and HCO3-
Sphincter - regulates entry of bile and enzymes into small intestine
Villi (villus plural), which then contain microvilli increase surface area greatly to aid in digestion
Epithelial cells secrete, absorb and transport matter
Absorption
Digestion and absorption of fat
Digestion of two glucose, broken down from maltose by maltase
Absorption of Sugars
Fructose can be facilitatedly diffused
Glucose and Galactose are actively transported in by a sodium gradient that must be pumped
back through via the sodium/potassium pump
Digestion and Absorption of Fat
Fat is a non polar molecule, therefore very hydrophobic (becomes spheres of lipid)
Very difficult to break down into smaller molecules due to enzymes in aqueous solution are only
able to get at surface molecules

Document Summary

Topics to be covered, fluid compartments, nutrition, digestion and absorption. Extracellular fluid, which includes plasma and interstitial fluid. Moves down concentration gradient, but cannot pass barrier by themselves, needs aid of transport protein. Moves against concentration gradient via an unenergetically favourable way which is what makes it an active process. Osmosis how water moves through membranes and is dependent on concentration of solute. Isotonic solution when concentration of solute inside is same as outside. Hypertonic solution lower concentration inside, fluid moves outside. Hypotonic solution - higher concentration inside, fluid moves in. Organisms that harvest energy from light or chemical energy (eg. plants) Organisms that must get their nutrients from the environment such as by eating other organisms. Ingestion where food is consumed (eg. mouth) Digestion where nutrients are broken down (eg. stomach) Absorption ions, water and small molecules (eg. large and small intestines) Elimination waste excretion, anything that wasn"t absorbed (eg. anus)