What are the four steps of obtaining energy from food?
4. Waste Elimination
What is the difference between an incomplete and complete digestive system?
incomplete digestive system: food comes out same place it went in
complete digestive system: one full continuous tube
Why have human's teeth gotten smaller over time?
use of fire and tools to cut up meet and make it smaller
What is special about cichlids?
they have undergone adaptive radiation because of variations in pharyngeal jaws and ability to eat different things
In terms of teeth, humans and mammals are ________.
generalists (have incisors, canines, premolars, molars)
Describe the jaws of a carnivore.
bite force is driven by a fulcrum (allows for full force, like scissors)
Describe the jaws of an herbivore.
since herbivores don't need a substantial bite force, they're chewing is driven by a lever force that allows for grinding
What are the benefits of a complete digestive tract?
one-way flow allows for continuous digestion, specialization of various organs, efficiency
What are the two types of muscles in the Esophagus?
skeletal muscles at top, smooth muscles at bottom
What happens in the mouth?
increase size of surface area of food particles; saliva begins to break down carbohydrates and lipids; salivary glands supply lubricating mucus
What are the muscles called that seal off the stomach from esophagus and small intestine?
What do parietal cells do?
have a membrane spanning proton-ATPase that pumps out protons, in combination with Cl ions that have diffused out, these cells make Hydrochloric (stomach) acid
What do chief cells do?
chief cells secrete zymogen granules containing pepsinogen, the inactive form of the pepsin
How does pepsinogen turn into pepsin?
acid conditions in stomach convert it into pepsin (it prefers a pH of 1.5-2)
The small intestine cannot handle low pH conditions, so how does the lumen neutralize the pH?
the pancreas secretes tons of bicarbonate buffer
What is the lumen of the small intestine similar to? (think water regulation)
rectal gland of a shark
How does the lumen of the small intestine work?
it pumps sodium into blood so that water and glucose will be pulled out of lumen (via sodium re-entry)
What are essential amino acids?
8 (out of 20) amino acids that are required to manufacture proteins, but that cannot be synthesized by humans (we can synthesize the other 12)
What are electrolytes?
form ions in solution, influence osmotic balance and are required for normal membrane function
What are essential elements?
cannot be synthesized by the body, but they serve a wide variety of functions