1. The Digestive System 24 - Digestive System
Introductory Biology by Charles M. Zaremba © 2003, published by TEACHINGpoint

2. Function of the Digestive System
Breaks up food physically and chemically.
Stores food for a short period of time.
Absorbs the digested foods and passes them into the circulatory system.
Stores and eliminates undigested food from the body.

3. Types of Digestion
Mechanical: The physical breakdown of food by non-enzyme means.
Chemical: The use of enzymes to breakdown food.
Changes food into a NEW and smaller substance that can travel into the cells. It is chemically different.

4. Enzymes Enzymes work best Enzymes have a specific at a certain pH and
body temperature.
If the body gets too
hot or too cold, the
enzymes will not work
and we get sick or die
Enzymes have a specific
shape and can only do
one special job.
This is called the LOCK
AND KEY THEORY
because they only FIT
into one job

5. Regents Question Experiments revealed the following information
about a certain molecule:
— It can be broken down into amino acids.
— It can break down proteins into amino
acids.
— It is found in high concentrations in the
small intestine of humans.
This molecule is most likely
(1) an enzyme
(2) an inorganic compound
(3) a hormone
(4) an antigen

6. Regents Answer
(1) an enzyme

7. Parts of the Digestive System

8. Human Digestion The Mouth Esophagus Stomach Liver and Pancreas
Small Intestine
Large Intestine
Rectum
Anus

9. Mouth Both chemical and mechanical digestion occurs here.
The teeth and tongue will chop and mix the food.
The salivary glands will add enzymes to begin the chemical process.
The tongue will direct the moisten food into the gullet.

10. Esophagus The gullet is the opening to the esophagus.
It is 12 inches long and connects the mouth with the stomach.
Contains smooth muscles which contract, pulling the food downward (peristalsis).

11. Stomach Stores and digests food. pH of 1-2
Enzyme: pepsin which acts on proteins, rennin on dairy
HCl is needed to activate pepsin.
Mucus covers the inner lining to prevent the acid from eating the tissue.
The pylorus connects the stomach to the small intestine.

12. Regents Question The diagram below represents two molecules
that can interact with each other to cause a biochemical process to occur in a cell.
Molecule A╞ ╢Molecule B
Molecules A and B most likely represent
(1) a protein and a chromosome
(2) a receptor and a hormone
(3) a carbohydrate and an amino acid
(4) an antibody and a hormone

13. Regents Answer
(2) a receptor and a hormone

14. Small Intestine
It is divided into 3 parts: duodenum, jejunum, and ileum.
Most digestion takes place here
It is here that all the organic material are broken down into their monomers.
They are absorbed by structures called villi and sent into the blood.
The undigested food is passed on to the large intestine.

15. Liver, Pancreas, and Gall Bladder
These are accessory organs.
The liver produces bile which is needed to help digest fat.
The gall bladder stores the bile.
The pancreas produces enzymes need to finish digesting the main organic foods. It also produces insulin.

16. Large Intestine Also known as the colon
Absorbs excess water from the unused food.
E. coli will produce vitamin K.
Stores solid waste in the area called the rectum.

17. Absorption
The small intestine is lined with villi which increase the surface area
Nutrients are absorbed into the blood through the villi and travel the body to be used by the cells
The small intestine is longer
but thinner in diameter than
the large intestine