Digestion

1. Several digestive organs work together to break down food

2. Digestion begins in the mouth and continues in the stomach

3. Digestion is completed in part of the small intestine where absorption begins

Main Ideas

1. Finish the remaining sections in your digestion packet.

2. How does the digestive system help maintain homeostasis?

**Digestion Test – THURSDAY **Homework Worksheet – Due Wednesday **Movie on nutrients / Friday (12/19) (in-class asignment)

Do Now

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.

Digestion

Group 1 (chew and let sit in mouth)

Group 2 (no chewing, let sit in mouth)

Keep in mind:Mechanical digestion?Chemical digestion?

What is going on in your mouth?

1. Describe an enzyme:

2. What is the difference between hydrolysis and dehydration synthesis?

3. Where does digestion begin?

4. What type of digestion can happen in your mouth?

Do Now**Digestion Test – THURSDAY **Homework Worksheet – Due Wednesday **Movie on nutrients / Friday (12/19) (in-class asignment)

Mechanical 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

◦Benefit:

How is food digested?

1. Large sugar cube

2. Crushed up sugar

Explain why:

What will chemically digest faster?

What macromolecules would you find in this meal?

Break-down steak and potatoes-Mechanically-

Macromolecule Mechanicall

y broken down by

Broken down into Advantage

What macromolecules would you find in this meal?

Break-down steak and potatoes-Chemically-

Macromolecule

Chemically broken

down by

Broken down into these Small

Pieces Advantage

1. Could French fries be chemically or physically digested in your mouth? Explain

2. Could a piece of Steak be chemically or physically digested in your mouth? Explain

DO NOW(4,6)

Could this happen?

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

Ingestion

Mechanical 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

Mouth

Pharynx◦ Back of throat◦ Connects the nasal passages, mouth, esophagus & trachea

After ingestion in the mouth

Esophagus◦ About 12 inches in length ◦ Surrounded by smooth muscle (involuntary

control)

How does food get down this tube?

Peristalsis◦ Begins when you swallow with your tongue

◦ Muscle contraction (wavelike motion) that pushes food through the digestive system

How can this be demonstrate?

How does food go down the esophagus

Swallowing & NOT Choking

Epiglottis◦ Flap of cartilage ◦ Closes trachea (windpipe) when swallowing◦ Food travels down esophagus

Thick walled muscular organ that may stretch

Next stop: Stomach

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)

Mechanical Digestion◦ Movement of muscles assists in

movement & breaking apart of food.

Stomach

Chemical Digestion◦ Gastric juice contains the enzyme: Protease (pepsin)

Pepsin ◦ Enzyme used to breakdown proteins into:

Complete the equation: ◦ Protein + __________ amino acids

Pepsin

1. How does food get from the mouth to the stomach?

2. What type of digestion happens in the mouth? What begins to be digested in the mouth? Why?

3. What type of digestion happens in the stomach? What is digested in the stomach? Why?

Do Now(2,6,8)

Mucous◦ Coats the stomach to prevent

contact between walls and acid.

◦ Where else is mucous found?

How are the walls of the stomach protected from the low pH (1.5-2.5)?

**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

Mouth to Stomach Regents Questions:

Review

Ingestion◦ 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

The road so far…

LiverSecretes 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

Beginning of Small Intestine

Temporarily STORES the BILE, produced by the Liver, until food enters the SMALL INTESTINES

1. Describe where the following macromolecules are digested:

Protein

Carbohydrates

Fats

2. Why is the pancreas important?

Do Now (7) Loose leaf / notebook

In a sentence, explain what each enzyme breaks down and where they are mainly located:

◦ Protease (pepsin)

◦ Amylase

◦ Lipase

Do Now (1,5) Loose leaf / notebook

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) :

Beginning of Small Intestine

1. 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?

2. What is the optimal pH for Amylase? When salivary amylase I exposed to this optimal pH, describe the rate of reaction for amylase.

3. Are enzymes specific for the substrates they work on? Why?

Overall Functions:

1. Complete the chemical digestion of food(Carbs, proteins, fats)

2. Absorb the nutrients◦ Absorbs simple sugars, amino acids,

fatty acids & glycerol into the bloodstream

Small Intestines

Where does glucose go after it is absorbed into the bloodstream?

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.

Small Intestines

Capillaries:◦ Thin walled blood vessels (one cell thick) that carry

nutrients from the small intestines to all parts of the body

Functions:

1. Absorption of water

2. Absorption of vitamins

3. Elimination of undigestable material, known as egestion

Large Intestines

Large Intestine, large problems

1. What happens when water is not being reabsorbed in the small intestines?

2. What happens when too much water is absorbed in the large intestines?

Disorders of the Digestive System:

Constipation:

Diarrhea:

- when too much water has been removed from undigested food- feces is too hard to be released easily

when TOO LITTLE water is removed from waste

Ulcer:

when the lining of the stomach is exposed to the acid creating a sore

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

1. Why is the small intestine important for maintaining homeostasis?

2. How are nutrients absorbed into the blood stream?

Do Now