Human digestive systems

Enzymes, organisation principles and required practicles

What is a tissue ?

a group of cells with similar structure and function

What are organs?

Aggregations of tissues performing specific funstions

What is an organ system?

organs are organised in an organ system which work together to form organisms

What is a cell

Basic building blocks of all living organisms

a group of organells working tgether to perform a common function

What is the function of a digestive enzyme?

Digestive enzymes converts food into small soluable molecules which can be absrobed by the blood stream.

What is an enzyme?

a biological catalyst . They catlyse specific reactions in living organisms due to the shape of their active site.

What does carbohydrase do?

Carbohyrases breaks down carbohysdrates to simple sugars.

amylase is a carbohydrase which breaks down starch.

What does lipases do?

They break down lipids to glycerol and fatty acids

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describe the lock and key theory

Enzymes bind to the specific substrate because they are complimentary shapes

so substrate is broken don into products

and products are released.

Explain how the enzymes work by lock and key theory

• Substrate binds into the active site of the enzyme

• Substrate and active sites are complementary in shape

• substrate acts as the key and the enzyme acts like the lock

• enzymes catalyse a reaction to give a product

• the substrate is broken down into products

• after the enzymes have catalysed the reaction, the product is released from the active site.

• the enzyme is then free to act on more substrate molecules.

How do you test for glucose/sugar?

* add Benedict’s (solution/reagent to the liquid)
* boil / heat
* (if glucose is present) the **blue color changes to yellow/green / orange/brown / (brick)red**

How do you test for starch?

* add **iodine** solution/reagent (to the liquid)
* (if starch is present) it **changes color to blue/black (from yellow / orange / brown)**

How do you test for protien?

* Add food to a test tube
* add a few drops of **biuret** solution and shake it gently
* (if protein is present) colour will go from **blue to lilac-purple**

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What is bile and what is its function?

Bile is made in the liver and stored in the gall bladder.

It is alkaline to neutrilise hydrochloric acid from the stomach.

It also emulsifies fat to form small droplets which increase the surface area.

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The alkaline conditions and large surface area increases the rate of fat breakdown by lipase.

What happens to enzymes when there is an increase in the temperature?

* Increasing temperature means there is more successful collisions
* enzymes + substrates have more kinetic energy which means more substrate is turned into products
* however, when the temperature is above optimum temperature (the number of collisions still increases) the active site becomes deformed meaning the substrate and the active site is no longer complementary so the number of successful colloions decrease

what is the effect of pH in enzymes?

* If the pH is too high or too low, the bonds that hold the amino acid chain together to make up the protein can be destroyed

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* This will change the shape of the active site, so the substrate can no longer fit into it, reducing the rate of activity

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* Moving too far away from the optimum pH will cause the enzyme to denature and activity will stop

A method for testing the pH of enzymes

* Place single drops of iodine solution in rows on the tile
* Label a test tube with the pH to be tested
* Use the syringe to place 2cm3 of amylase in the test tube
* Add 1cm3 of buffer solution to the test tube using a syringe
* Use another test tube to add 2cm3 of starch solution to the amylase and buffer solution, start the stopwatch whilst mixing using a pipette
* After 10 seconds, use a pipette to place one drop of the mixture on the first drop of iodine, which should turn blue-black
* Wait another 10 seconds and place another drop of the mixture on the second drop of iodine
* Repeat every 10 seconds until iodine solution remains orange-brown
* Repeat experiment at different pH values – the less time the iodine solution takes to remain orange-brown, the quicker all the starch has been digested and so the better the enzyme works at that pH

Where is bile produced ?

In the small intestine and pancrease

Where is protease produced?

Stomach, small intestine and pancrease

Where is amylase produced?

Salivary glands and pancrease