The Digestive System

/ Chapter 8
√ I can describe the chemical structure of carbohydrates, lipids and proteins.
√ I can describe how enzymes work (the lock and key model), and how things like pH, temperature, and other chemicals can improve or inhibit enzymes.
· I can label the structures of the digestive system.
· I can describe how food is digested and absorbed into the blood, and I can describe the differences in how carbs, fats, and proteins are digested.

To be useful, all of the large chunks of food that we eat need to be broken down into tiny pieces can be ______. Digestion happens in two ways:

Physical Digestion:

Chemical Digestion:

8.3 The Digestive System - Ingestion

Every cell in your body needs nourishment, in the form of ______, ______, ______, ______, ______, and ______. Food must be delivered to the cells in a form that they can use, and this task is done by the ______with the assistance of the ______system.

Digestion involves both ______breakdown, through ______and other motions, and ______breakdown, through ______. The resulting substances are and by the circulatory system.

Label the parts of the digestive system, using the diagram on page 259 of your text as a guide.

Digestion occurs in 4 steps.

Use information from page 259 to fill in these boxes, in plain English (your own words).

Ingestion
Digestion
Absorption
Egestion

Mouth

· Mechanical or ______digestion begins in the mouth, with the action of ______. The ______rolls the food into a round ball called a ______and then we swallow it.

· The purpose of physical digestion is to ______, so that ______.

· Chemical digestion also begins in the mouth. The purpose of chemical digestion is ______.

Saliva

· is produced by the ______.

· The main enzymes in saliva are called ______, and their purpose is to ______.

· Saliva also ______

Esophagus

· the food tube from mouth to stomach

· Muscles in the throat squeeze the food and push it downward, like toothpaste in a tube: ______

· A flap of tissue called the ______blocks the windpipe when you swallow so that ______.

Stomach

· It is basically a J-shaped sack with a seal at the top and bottom. The top of the stomach is sealed with a ring of muscle that acts like a drawstring, called the ______, and the bottom with a ring of muscle called the ______.

· Physical digestion: ______.

· Chemical digestion: cells that line the stomach excrete ______.

o pepsinogen

o hydrochloric acid

o mucus

Pepsin = enzyme that digests protein.

This is a problem, because the stomach’s cells are muscle tissue – they are made of protein!

Solution:

1. Leave the protein inactive until it enters the stomach.

How does that happen?

2. Coat the stomach with a protective layer.

What is that layer called? What is it like?

Problems with the digestive system

Acid Reflux

Ulcers

· The partly digested food has been processed into a soupy, gunky mix called ______, and now it is passed on to the ______.

Answer page 263 # 3, 8, 12, 17, and this question:

What prevents most bacteria from surviving in the stomach?

Small Intestine

· ______enters from the stomach, through the _p______s______.

· There are three sections: ______. Most digestion occurs in the ______.

· TINY little bumps on the inside of the intestine, called ______, improve the body’s ability to move nutrients from the intestine into the blood. They do this by ______

· There are two problems with the liquid flowing from the stomach: it is ______and contains ______.

· The ______pH of the gastric juices must be ______.

· ______from gastric juices enters the small intestine and a chemical reaction converts it into ______. It enters the blood, and tells the ______to release ______. The ______is carried to the duodenum through a ______, where it ______.

· Pepsin is not a problem anymore – it ______, so it won’t ______

Digestion of Specific Nutrients

Carbohydrates

· The pancreas releases a______which continue the digestion of carbohydrates (that began in the ______). The carbohydrates are already in mid-sized chains; now they are broken into d______.

· Another set of enzymes called d______are released by the ______, and complete the digestion of carbs.

· All the carbohydrates are now in the form of m______, and they are absorbed into the ______through the ______.

Proteins

· The pancreas releases two enzymes called ______.

· ______enters the small intestine and is activated into a form called ______. It breaks ______.

· ______finishes the job by breaking ______.

· The a______a______can be absorbed into the ______through the v______.

Lipids pages 266 - 268

· Bile is a fluid from the ______. It contains ______. They act something like dish soap, by separating large ______into smaller ______. This increases the ______so that fat-digesting enzymes like the lipases can work.

· When the stomach is ______, extra bile is concentrated and stored in the ______.

· When there are fats in the small intestine, a hormone called ______is released. It is carried in the blood to the ______, and triggers the release of ______.

· ______are enzymes released from the ______that break down lipids. There are two kinds:

o ______breaks down ______into ______and ______.

o ______works upon ______.

Other functions of the liver

· breaks down ______from ______cells, and stores the products in the ______for removal

o this causes the characteristic ______of feces

· store ______(which is important for ______) and vitamins ______.

· ______harmful chemicals such as ______

When fat is emulsified into small droplets by the bile salts, is this physical digestion or chemical digestion? Justify your answer.

Liver and Gallbladder problems

· Bile contains an insoluble component called ______, which acts as a ______. Crystals of bile salt can form – large ones are called ______. They can block the ______(which runs from the gall bladder to the ______) and cause pain.

· The liver works to detoxify alcohol, but there is a limit. Excess alcohol consumption can lead to healthy liver tissue being replaced by scar tissue, a condition called ______.

Large Intestine

· By the time food reaches the large intestine, ______digestion is complete.

· The largest part of the large intestine, called the ______, has to hold waste long enough to reabsorb ______, along with ______.

· Bacteria such as ______use waste materials to make ______

What kind of relationship exists between humans and the bacteria in our gut? (Parasitism, commensalism, symbiosis, predator-prey, etc…) Justify your answer.

· The cell walls of plants are made of long-chain carbs called ______, which we cannot ______. We usually call it “dietary fiber”.

What important function is served by fiber? Explain how this works.

Add every digestive enzyme that we have learned about in class, next to the organ that produces it; beside each enzyme, make a note that describes where that enzyme is used, and what the substrate or function is

E.g. beside the salivary glands, write “Salivary amylase: break large-chain carbohydrates into medium-chain carbs.”

bicarbonate ions / bile / pepsinogen / erepsin / hydrochloric acid / salivary amylase
lipase / trypsinogen / mucus / disaccharideases / pancreatic amylase

Match the following digestive organs to the functions listed. You can use the names of the organs more than once.

mouth / pancreas / small intestine
esophagus / liver / large intestine
stomach / gallbladder / epiglottis

/5 (0.5 each)

______a. is the site of fat digestion

______b. secretes HCl

______c. secretes salivary amylase

______d. holds bile until required

______e. stores glycogen

______f. secretes sodium bicarbonate

______g. absorbs water and produces vitamins

______h. is the site of protein digestion

______i. begins starch digestion

______j. benefits from dietary fibre

Alcoholism and hepatitis C are two things that can cause cirrhosis of the liver. In a short paragraph, describe what cirrhosis is. Can it be prevented or cured? If so, describe how. What is the last-resort treatment for cirrhosis?

WEBQUEST Use all available resources to answer the following:

1. Some babies are born with a condition called jaundice.

What are the symptoms of jaundice?
Why does this condition produce a yellowing of the skin?
What treatment is given to a newborn with jaundice? Why does it work?
Adults can get jaundice – what would cause it?

2. Some people get crystals of bile salts in their gall bladders. They can be removed by surgery, or by ultrasound. If you had gall stones, which of these two techniques would you want to receive? Explain why.

3. What effect does taking aspirin have, upon a person who has ulcers?

4. “Crohn’s Disease” and “colitis” are two types of Inflammatory Bowel Disease (IBD)

What are the symptoms of IBD?
How is it treated?

Biology 20 - The Digestive System Page | 1