Explain why digestion of large food molecules is essential.

What sort/size of food do we normally eat?

Normally the biggest thing we can fit is a mouth-full!

http://www.noticiascadadia.com/uploads/pics/burger_king.jpg

Where does our food that we eat get used up?

In order to get into here it has to pass through a membrane.

http://www.answersingenesis.org/assets/images/articles/nab/human-cell.jpg

Making the food go from this big…… …To molecules able to pass through a plasma membrane is called Digestion.

http://www.noticiascadadia.com/uploads/pics/burger_king.jpg

Lipid molecule Amino acid molecule http://www.reactivereports.com/8/images/nand.jpg

http://www.ncl.ac.uk/bmsu/assets/photos/glucose-molecule.jpg

http://www.solvias.com/documents/Grafiken/images_services/molecule_weiss.jpg

Explain the need for enzymes in digestion.

Digestion can be split into 2 types: Mechanical Digestion – The physical breaking of the food.

Chemical digestion – the chemical break down of the food into its constituent parts.

Can you think of where mechanical digestion takes place?

Biting the food Chewing the food Churning in the stomach

But even that doesn’t get the food small enough to pass through a phospholipid bilayer and into a cell!

If we were to wait till the food naturally fell apart into small enough pieces it would take more than 2 months!

Look at this animation of fruit decaying…….

http://www.youtube.com/watch?v=FgKZp18jJnA&featu re=related Or we could always cook it……..

Because our body works best at 36 o C we can’t cook it and we cant hold it inside us for 2 months so instead….

We use something that speeds up reactions and reduces the temperatures that are needed for reactions…….

Enzymes

State the source, substrate, products and optimum pH conditions for one amylase, one protease and one lipase.

Type of enzyme Name of enzyme (pH) What it works on Amylase Protease Lipase What it produces Where Salivary Amylase pH 7 Pepsin pH 1.5-3 Starch Proteins (Poly Peptide) Maltose Dipeptides Pancreatic Lipase pH 7 Lipids (fats and oils) Fatty acid and Glycerol Mouth Stomach Duodenum

Some of these reactions need very specific conditions. What keeps the mouth from becoming acid?

What does the stomach produce to get a pH of 1.5 – 3? Won’t this damage the stomach? How does the stomach normally defend against this damage?

When this defense goes wrong…….

http://www.helico.com/images/du_gu_1.jpg

What does bile do?

This is called emulsification. Why is it important to the speed at which Lipase works?

How are the different regions of the gut kept separate?

There are 2 other sphincters in the gut where are they?

http://www.sjhsyr.org/sjhhc/hidc07/graphics/images/en/19223.jpg

Diagram of the digestive system.

Learn these labels: Mouth Oesophagus Duodenum Small intestine Anus Stomach Large Intestine Rectum http://www.gutenberg.org/files/18559/18559-h/images/figure10.png

Now test yourself Mouth Oesophagus Duodenum Small intestine Anus Stomach Large Intestine Rectum http://www.gutenberg.org/files/18559/18559-h/images/figure10.png

Outline the function of the stomach, small intestine and large intestine.

There are several processes you need to know about; what they are and where they happen.

Ingestion: Taking food into the digestive system.

Normally happens in the mouth.

Digestion: Breaking the food down to soluble bits Happens between the mouth and the start of the small intestine.

http://urbanext.illinois.edu/diabetes/images/food_digestion.gif

Distinguish between

absorption

and

assimilation

.

Absorbtion: This is when the soluble food particles which have been digested get passed from the intestines into the blood stream.

Assimilation: is when the soluble substances are taken from the blood stream and used in the body cells.

Egestion: Is the removal of the bits of food that have not been digested. It normally occurs at the anus!

So what happens where? Fill in the following table: Organ Mouth Stomach What process happens there?

Ingestion and Digestion Digestion What makes the organ good at its job?

Teeth, saliva, biting and chewing Acid, protease, gastric pits, churning Duodenum Digestion Pancreatic duct, bile duct.

Small Intestine Large intestine Anus Absorption of digested products.

Villus, microvillus, length, blood supply, Absorption of water and minerals Egestion

Explain how the structure of the villus is related to its role in absorption and transport of the products of digestion.

http://www.jpp.krakow.pl/journal/archive/0605_s3/gfx/rys0506_9.jpg

http://www.biog1105-1106.org/demos/105/unit6/media/villus.structure.jpg

What makes a villus so good at its job?

Think about Surface Area . What is the effect of surface area on rate of diffusion? How is the surface area of the gut increased with villi? How is the surface area of the villus increased with microvilli? Think about the distance over which products must diffuse. How does a villus ensure the distance is small?

Think about how the absorbed products of digestion are taken away from the gut. What is it in a villus that allows this?

The villus is very active. What cellular processes are occurring across the cell membranes that would require lots of energy. What supplies this energy? Find out about a lacteal.