1. Digestion

2. Main Ideas Several digestive organs work together to break down food
Digestion begins in the mouth and continues in the stomach
Digestion is completed in part of the small intestine where absorption begins

3. Do Now Finish the remaining sections in your digestion packet.
How does the digestive system help maintain homeostasis?
**Digestion Test – THURSDAY
**Homework Worksheet – Due Wednesday
**Movie on nutrients / Friday (12/19) (in-class asignment)

4. Digestion How does the digestive system help maintain homeostasis?
Breakdown of food from complex to simple substances so the nutrients may pass through the cell/plasma membrane of cells.

5. What is going on in your mouth?
Group 1 (chew and let sit in mouth) Group 2 (no chewing, let sit in mouth) Keep in mind: Mechanical digestion? Chemical digestion?

6. Do Now Describe an enzyme:
**Digestion Test – THURSDAY
**Homework Worksheet – Due Wednesday
**Movie on nutrients / Friday (12/19) (in-class asignment)
Do Now
Describe an enzyme:
What is the difference between hydrolysis and dehydration synthesis?
Where does digestion begin?
What type of digestion can happen in your mouth?

7. How is food digested? Mechanical Digestion: Chemical Digestion:
Food is physically cut, ground and torn into smaller pieces
Benefit:
Chemical Digestion:
Food, large organic molecules, is broken down into small, simple molecules by hydrolysis

8. What will chemically digest faster?
Large sugar cube
Crushed up sugar
Explain why:

9. Break-down steak and potatoes -Mechanically-
What macromolecules would you find in this meal?
Macromolecule
Mechanically broken down by
Broken down into
Advantage

10. Break-down steak and potatoes -Chemically-
What macromolecules would you find in this meal?
Macromolecule
Chemically broken down by
Broken down into these Small Pieces
Advantage

11. DO NOW(4,6) Could this happen?
Could French fries be chemically or physically digested in your mouth? Explain
Could a piece of Steak be chemically or physically digested in your mouth? Explain

12. Ingestion
Taking food into the body (mouth). This begins the digestion process.

13. Mouth Mechanical Digestion Chemical Digestion
Chewing – breaks food into smaller
pieces to increase surface area for
enzyme activity
How?
Chemical Digestion
Saliva – wets food and coats it for swallowing
Salivary Amylase – In saliva, this enzyme begins the breakdown of starch (polysaccharide)
pH is neutral – This is the optimal pH for amylase functioning

14. After ingestion in the mouth
Pharynx
Back of throat
Connects the nasal passages, mouth, esophagus & trachea
Esophagus
About 12 inches in length
Surrounded by smooth muscle (involuntary control)
How does food get down this tube?

15. How does food go down the esophagus
Peristalsis
Begins when you swallow with your tongue
Muscle contraction (wavelike motion) that pushes food through the digestive system
How can this be demonstrate?

16. Swallowing & NOT Choking
Epiglottis
Flap of cartilage
Closes trachea (windpipe) when swallowing
Food travels down esophagus

17. Next stop: Stomach Thick walled muscular organ that may stretch
Contains gastric juice (Hydrochloric acid; HCL acid) that has a low pH of 1.5 to 2.5
Purpose of acid & low pH:
Kill bacteria in food
Activate enzymes in the
stomach (optimum pH)

18. Stomach Mechanical Digestion
Movement of muscles assists in movement & breaking apart of food.
Chemical Digestion
Gastric juice contains the enzyme: Protease (pepsin)
Pepsin
Enzyme used to breakdown proteins into:
Complete the equation:
Protein + __________ amino acids
Pepsin

19. Do Now(2,6,8) How does food get from the mouth to the stomach?
What type of digestion happens in the mouth? What begins to be digested in the mouth? Why?
What type of digestion happens in the stomach? What is digested in the stomach? Why?

20. How are the walls of the stomach protected from the low pH (1.5-2.5)?
Mucous
Coats the stomach to prevent contact between walls and acid.
Where else is mucous found?
**Food is now moving to the small intestines and ACCESSORY ORGANS will continue the digestion process
Accessory Organs
Not part of the digestive tube but are connected and aid in digestion
Include salivary glands, liver, gall bladder & pancreas

21. Review
Mouth to Stomach Regents Questions:

22. The road so far… Ingestion Food moves down esophagus
Through the mouth
Chemical digestion of carbohydrates (by salivary amylase)
Mechanical digestion of food (by teeth)
Food moves down esophagus
Moves by peristalsis (muscle contractions)
Mucus in esophagus to help food slide down
Food moves to stomach
Stomach is acidic; activates certain low pH enzymes
Chemical digestion = Enzymes (pepsin) digest proteins
Mechanical digestion = churning and grinding of stomach

23. Beginning of Small Intestine
Liver
Secretes Bile
Helps in the mechanical breakdown of fats
Process called emulsification
Emulsification
Process where bile turns fat into tiny droplets to increase the surface area of fat for enzyme action
Gallbladder 
Temporarily STORES the BILE, produced by the Liver, until food enters the SMALL INTESTINES

24. Do Now (7) Loose leaf / notebook
Describe where the following macromolecules are digested:
Protein
Carbohydrates
Fats
Why is the pancreas important?

25. Do Now (1,5) Loose leaf / notebook
In a sentence, explain what each enzyme breaks down and where they are mainly located:
Protease (pepsin)
Amylase
Lipase

26. Beginning of Small Intestine
Pancreas
Secretes Pancreatic Juice
Used to neutralize the low pH of food from the stomach
Supplies enzymes needed for FINAL chemical digestion of food
Pancreatic Juice Contains
Amylase :
Lipase :
Protease (a.k.a. trypsin) :

27. How would enzyme activity be different for the enzyme pepsin if placed in an environment with a pH of 5 instead of a pH of 2?
Are enzymes specific for the substrates they work on? Why?
What is the optimal pH for Amylase? When salivary amylase I exposed to this optimal pH, describe the rate of reaction for amylase.

28. Small Intestines Overall Functions:
Complete the chemical digestion of food
(Carbs, proteins, fats)
Absorb the nutrients
Absorbs simple sugars, amino acids, fatty acids & glycerol into the bloodstream
Where does glucose go after it is absorbed into the bloodstream?

29. Small Intestines
How do the end products of digestion enter the bloodstream?
Villi – fingerlike projections that line the inside of the small intestines to absorb the nutrients and increase the surface area.

30. Capillaries:
Thin walled blood vessels (one cell thick) that carry nutrients from the small intestines to all parts of the body

31. Large Intestines Functions: Absorption of water Absorption of vitamins
Elimination of undigestable material, known as egestion

32. Large Intestine, large problems
What happens when water is not being reabsorbed in the small intestines?
What happens when too much water is absorbed in the large intestines?

33. Disorders of the Digestive System:
Constipation:
- when too much water has been removed from
undigested food
- feces is too hard to be released easily
Diarrhea:
when TOO LITTLE water is removed from waste
Ulcer:
when the lining of the stomach is exposed to the acid creating a sore

34. Anorexia Nervosa (anorexia) –
severe weight loss due to lack
of food taken into the body
(starvation).
- believed to be psychological
Bulimia – when an individual vomits
after meals

35. Do Now
Why is the small intestine important for maintaining homeostasis?
How are nutrients absorbed into the blood stream?