Bio 104 5/16/96
Bio 104 5/16/96
These notes not yet reviewed by Dr. Barstow
Process of digestion:
Animals are heterotrophs, they need organic molecules for:
- energy
- formation of new cells
The digestive system works in connection with the excretory
system, circulatory, and respiratory systems.
The digestive system breaks down molecules into monomers and
circulates them through the body.
- breaking down food so it can be taken up by the
circulatory system
- then eliminates unabsorbed waste from the body
- provides blood with nutrients
Things that are digested/broken down
- Carbohydrates
- polysaccharide
- starch = forms disaccharides or double sugars (maltose)
- maltose
- sucrose
- lactose
- The double sugars are then broken down further
into simple sugars such as glucose; this is what
is absorbed
- Main function is energy.
- Protein
- polymer of amino acids is broken down into peptide
then broken down once more into amino acids
- protease is the enzyme that breaks down proteins.
- Nucleic Acids
- broken down into nucleotides, which are furthered
to become ribose sugars and nitrogenous bases.
- Lipids
- elmusified fats are broken down into:
- fatty acids
- glycerol
Human digestive System. See figure 38.4
The human digestive system. Figure 38.4
- Starts in the mouth which contains salivary glands, then
the canal goes down the esophagus into the digestive tract.
- Food taken in and mechanically broken down and mixed with
saliva, the enzyme salivary amylase, then the food travels
down the esophagus to the stomach.
- In the stomach hydrochloric acid mixes with the food and
begins to break it down.
- From the stomach the contents enter the small intestine,
where secretions from the gall bladder and pancreas mix
with the food.
- gall bladder secretes bile
- used for elmusification of fats
- pancreas secretes many different enzymes
- Large intestine meets the small intestine, and begin the
recovery of water.
- stores undigested food in the colon.
SEE THE CHART ON ENZYMES IN CHAPTER 38
Most food absorbed into the tissues of small intestine
- amino acids and sugars go into capillaries and lipids
go into lymph vessels
Large intestine gets rid of bacteria, insoluble plant fiber,
and other undigested food products.
Control of the digestive process is done by hormones.
- Gastrin
- in the stomach
- triggered by the entry of food into the stomach
- secretion of Hydrochloric acid
- CCK
- in duodenum
- triggered by arrival of food into the small
intestine
- stimulate release of bile and pancreatic enzymes
- Secretin
- HCL in duodenum
- secretes bicarbonate
The mouth
- consists of mechanical devices for breaking down food
four type of teeth
- incisors (8)
- canine (4)
- premolar (8)
- molar (12)
Once food is broken down by the teeth, food is pushed
back into the esophagus.
- bolus of food goes down the esophagus by the
contraction of circular muscles See figure 38.6 and 38.7
How humans swallow. Figure 38.6.
The stomach. Figure 38.7.
The stomach
- a lot of mucus and surface area
- can stretch
- actually churns
- Food then put into the s. intestine by a sphincter
muscle and the enters the duodenum. See Figure 38.8
Organization of the vertebrate digestive tract. Figure 38.8
Small Intestine
- a lot of muscle
- covered by villi
- capillary bed and lymph vessels
- on each villi there are microvilli
- The end result of taking up food by villi is the
transporting of food, via the blood, to the liver.
Calorie:amount of heat it takes to raise 1 gram of water 1
degree.
- 3.1 cal. per gram of protein
- 9.5 cal. per gram of fat
All illistrations from Understanding Biology, 3d ed.,
by Raven & Johnson, © 1995 Times Mirror Higher Education Group, Inc.
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