FOOD AND DIGESTION STUDY GUIDE

WE ARE WHAT WE EAT!

 

1. WHY DO WE EAT FOOD?

 

2. DOES IT MATTER WHAT KIND OF FOOD WE EAT?

 

3. HOW DOES THIS HOT FUDGE SUNDAE TURNED INTO SOMETHING OUR BODY CAN USE FOR ENERGY?

 

WHAT WILL I LEARN:

1. I will learn how we get the glucose molecules to make energy for our bodies

2. I will learn what food is and how it is broken down in the digestive system, 

3. I will learn the process of digestion

WHY I WILL LEARN THIS:

It is important to my understanding of why we eat and how that food is turned into the energy our bodies use.

I WILL KNOW I UNDERSTAND THIS INFORMATION WHEN:

1. I can define what an organic molecule is, and the three types of organic molecules our bodies use as food

2. I can define what the digestive system is and its basic parts

3. I can discuss the process of digestion

 

WHAT IS FOOD?

 

WHAT WE HAVE ALREADY LEARNED:

We learned in class that our cells break up the molecule glucose to make energy, for the body to do work, by a process called cellular respiration.  We learned plants make glucose by a process called photosynthesis, turning sunlight energy into chemical energy.  This brings us to the question how do WE get the glucose?  How does it get into our cells?  Why do our cells use GLUCOSE?  Do they use any other molecules for energy?

Food is defined as any nutritious substance that people or animals eat or drink, or that plants absorb, in order to maintain life and growth.  

Eating, for mammals, is to put food in the mouth chew and swallow.  We are mammals.  We love to do it!  Food tastes good because we have taste buds on our tongues.  Our body depends on us eating to have the energy to keep going!  When a human body gets hungry, the brain signals the stomach to produce acid, and the muscles of our stomach to move.  To us, we experience that as our stomach growling, or hunger pains.  We see the cheeseburger, and our brain tells glands in our mouths to make saliva.  Our bodies drive us to eat.  That is because every single action in your body, known and unknown to you, requires energy.  

 

Our bodies are energy factories.  Every movement, every blink, swallow, step, even every thought and memory require energy.  Cellular Respiration turns glucose into a molecule called ATP.  ATP is an energy carrying molecule.  It carries energy to every reaction that happens in your muscle cells for you to move, or to your nerve cells for you to taste or see, to your intestine cells so you can absorb more food.  You have millions of chemical reactions going on in your body at any moment. The process of turning the food we eat into energy is one of the most important things our body does to keep us alive. 

FOOD IS CHEMISTRY

Lets look at an apple.  There are many kinds of apples,                                  

green and red, sweet and bland, large and small,

but they all are made up of molecules called ORGANIC COMPOUNDS. 

 

ORGANIC COMPOUND- are molecules that contain carbon atoms covalently bonded to hydrogen atoms (C-H bonds).  All of the food we eat containes molecules with Carbon and Hydrogen bonded together.  

 

There are four types of organic compounds, three of which we eat:

1. Carbohydrates- fruits, vegitables, graines- these are easily broken down into glucose.  Our bodies use carbohydrates for energy. 

2. Proteins- meat and some plant matter like avacado, olives, nuts- our body uses proteins to build structures like our nose and ears and skin

3. Fats (Lipids)- oils, butter, fat on meat- our bodies store energy in fats.  They are saved for making energy when we run out of glucose. 

4. Nucleic Acids- we make our own nucleic acids from proteins and other molecules, so we don't need these as food. 

 

Our apple contains large amounts of carbohydrates.  Carbohydrates are made from simple sugars called glucose, bonded together in long chains.  Fats and proteins are broken down too, but to be used by our cells for energy, they get rearranged chemically by the liver into glucose.  

How does the food get broken down into molecules that can travel in the blood and get absorbed into our cells?

DIGESTION!!

DIGESTION

Digestive System- a tube in which food is reduced to particles, then to molecules small enough to be absorbed into the internal environment. 

digestion- the sequence by which food is broken down and chemically converted so that it can be absorbed by the cells of an organism and used to maintain vital bodily functions.

Human have a COMPLETE Digestive System- which means it has an opening for food to go in, and an opening at the other end for waste to be eliminated.  Some organisms have only one opening, where both nutrition goes in and waste goes out.  This is called an incomplete digestive system. 

The system is folded back and forth, but if it were stretched out it would measure  21 to 30 feet long. 

HOW HUMANS DIGEST THEIR FOOD

Chewing

  1. Chewing

A human has 32 teeth in upper and lower jaws.  The front teeth are called incisors shear/cut off chunks of food, canines tear off food, and premolars and molars grind and crush the food.  Digestive enzymes in saliva immediately begin to break down the food, and the saliva moistens it so it is easier to swallow. 

2. Swallowing

   The tongue muscles contract and the food begins to move down the pharynx ( top of the throat) contractions of the muscles around the esophagus contract and move the food down  to the stomach.

3. Stomach

     The stomach is a muscular stretchy sac. It mixes the food, dissolves and degrades the food, and helps control the passage of food to the small intestine.  Glands in the stomach secrete Hydrochloric acid, about 2 liters per day.  The mixture of acid and food is called CHYME.  The acid kills many microorganisms.   Heartburn is when the acid backs up into the esophagus. The stomach walls secrete mucous and bicarbonate ions that counter the acid. Contractions of the stomach muscle close a sphincter at the top of the small intestine.  Only a small amount of Chyme is allowed into the intestine before the sphincter closes again. 

4. Small Intestine

    Most of the nutrients from food are absorbed in the small intestine.  The pancreas and liver secret enzymes into the small intestine that help with this process.  Pancreatic enzymes break down carbohydrates, proteins, nucleic acids and fats.  It also secrets Bicarbonate which helps buffer the acidic chyme arriving from the stomach. The liver secretes bile that helps with fat digestion by a process called emulsification ( breaking up fat blobs). 

5. Large Intestine

     Substances not absorbed in the small intestine move into the large intestine- also called the COLON. Here the waste is concentrated and stored.  While in the large intestine, water and ions move out of the substance and back into the blood stream.  

6. Rectum

     The waste material moves into the rectum.  Distention of the rectum wall triggers a reflex pathway for rectum muscles to contract.  

7. Anus

     The opening of the rectum. A muscle we voluntarily control for expelling waste. 

 

BACK TO THE QUESTIONS!!

 

1. WHY DO WE EAT FOOD?

 

2. DOES IT MATTER WHAT KIND OF FOOD WE EAT?

 

3. HOW DOES THIS HOT FUDGE SUNDAE TURNED INTO SOMETHING OUR BODY CAN USE FOR ENERGY?