B3 - Organisation and the Digestive System

What are tissues, organs and organ systems?

- A tissue is a group of cells with similar structure and function
- An organ is a collection of tissues performing specific functions
- An organ system is organs that work together. Organ systems work together to form an organism.

What is the digestive system?

An organ system where several organs work together to digest and absorb food.

What are the function of these organs?
Liver -
Stomach -
Small intestine -
Large intestine -

- Produces bile
- Breaks down large insoluble molecules into smaller soluble ones
- Breaks down large insoluble molecules into smaller soluble ones and absorbing them
- Absorbing water from undigested food

What are simple sugars and what is the test for them?

Simple sugars are carbohydrates that only contain 1 or 2 sugar units.

They turn blue benedict’s solution brick red when heated.

also boil the test tube after adding benedict’s solution for 5 min at 75 degrees

What are complex sugars and what is the test for them?

Complex sugars are long chains of simple sugar units bonded together.

Starch turns yellow-red iodine solution to blue-black.

What are lipids and what is the test for them?

Lipids are compounds made of three fatty acid molecules bonded to one molecule of glycerol.

The ethanol test checks for lipids in solutions

What are protein molecules and what are the test for them?

Protein molecules are long chains of amino acids.

Biuret solution turns from blue to purple when protein is present.

What are catalysts?

Catalysts increase the rate of chemical reactions without changing chemically themselves

What are enzymes?

Enzymes are biological catalysts that catalyse specific reactions in living organisms due to their active site shape.

Explain the lock and key theory

Substrate meets and enzyme which has a specific acitve site. Substrate binds to the active site of the enzyme. The chemical reaction occurs which causes the substrate to split into two different products which detach from the enzyme.

What is metabolism?

Metabolism is the sum of all chemical reactions in the body

What is the effect of temperature on enzyme action?

The rate of the reaction increases alongside the temperature up until it reaches the optimum temperature when the reaction works as fast as possible. As the temperature increases more, the rate fo reaction decreases until it hits 0 when the enzyme denatures.

What does the term "denatured" nean?

When the active site of the enzyme changes and can no longer fit the substrate.

How does ph affect the enzyme action?

change in ph affects the forces between the folded amino chains. Change in ph can cause the enzyme to completely stop working. Different enzymes have different optimum ph.

What is digestion?

Digestion is the breakdown of large insoluble molecules into soluble substances that can be absorbed into the blood across the wall of the small intestine.

Where are digestive enzymes made?

Stomach, small intestine and pancreas

What are carbohydrase and where are they found?

Carbohydrase such as amylase catalyse the breakdown of carbohydates into simple sugars. They are usually found in the mouth and small intestine

What are proteases and where are they found

proteases are enzymes that catalsyses the breakdown of proteins to amino acids. It takes place in the stomach and small intestine.

What are lipase and where are they found?

lipase breaks down lipids into fatty acids and glycerol. This happens in the pancreas and the small intestine.

What Ph does protease work best in?

acidic conditons

What Ph does lipase work best in?

akaline conditions

Where is bile stored,produced and released?

Bile is produced in the liver and then its stored in the gall bladder and released through the bile duct.

What is the role of bile?

Bile is a green-yellow akaline that neutralises the acidic liquid that comes from the stomach acid.

This provides the alkaline conditions needed for the enzymes to work most effectively.

it also emulsifies fat to provide a large surface area for lipase enzymes to work more effectively.

Investigation on the effect of pH on enzyme activity

Add iodine to spotting tile

add 2cm amylase with 1cm of ph7 buffer solution.

add starch solution to a different test tube

Mix and start a stopwatch. After 10 seconds, add a drop of the solution to the iodine in the spotting tile. repeat every 10 seconds till iodine remains yellow brown

repeat using different buffer solutions of different pH.

Improve experiment through controlling temperature by using a water bath or using a colorimeter to measure more accurately.