B3 Flashcards
What is a tissue?
A group of cells with similar structure and function
What are organs?
Collections of tissues performing specific functions
How are organs organised?
Into organ systems which work together to from organisms
What are organ systems?
Groups of organs that perform specific functions in the body
What is the digestive system in a mammal?
An organ system where several organs work together to digest and absorb food
What are carbohydrates made up of?
Units if sugar
What are simple sugars?
Carbohydrates that contain only one or 2 sugar units
What do complex carbohydrates contain?
Long chains of simple sugar units bonded together
What do lipids consist of?
3 molecules of fatty acids bonded to a molecule of of glycerol
What are protiens made up of?
Long chains of amino acids
What is the test for starch?
Iodine
What is the test for sugar?
Benedict’s
What is the test for protien?
Biuret
What must be used during food tests?
Safety goggles
What are the steps to prepare for food tests?
- Take food sample and grind with distilled water using a mortar and pestle to make a paste
- Transfer paste to a beaker and add more distilled water, stir so the chemicals in the food dissolve in the water
- Filter the solution to remove suspended food particles.
- Then test for each food
What are the steps when testing for starch?
- Place 2mc cubes of food solution into a test tube
- Add a few drops of iodine solution that is orange
- If starch is present the iodine will turn blue-black, if their is no starch the iodine will stay orange
What are the steps when testing for sugar?
- Place 2cm cubes of food solution into a test tube
- Add 10 drops of denedict’s solution which is blue
- Place test tube into a water bath or beaker with boiled water and leave for 5 minuites
- If sugars are present the Benedict’s solution will change colour, if green then their is a small amount of sugar, if yellow then their is more sugar present but if brick red then their is a lot of sugar present
What are the steps for testing for protein?
- Put 2cm cubed of food solution and 2cm cubed of biuret solution which is blue
- If protein is present the solution will turn purple
What are the steps for testing lipids?
1.When preparing the solution, we do not filter the solution
2. Put 2cm cubed of food solution to a test tube
3. Add a few drops of distilled water and a few drops of ethanol
4. Then gently shake the solution
5. If lipids are present then a white cloudy emulsion forms
What do catalysts do?
Increase the rate of chemical reactions without changing chemically themselves
What are enzymes?
Biological catalysts
What do enzymes do?
Catalyse specific reactions in living organisms due to the shape of their active site
What are active sites?
Long chains of amino acids that are folded to produce a molecule that has a unique shape so it can bind to a specific substrate molecule
What happens when the substrate bunds to the active site?
The reaction is catalysed by the enzyme
What is metabolism?
The sum of all the reactions in a cell or the body
State 3 ways enzymes catalyse specific types of metabolic reactions
- Building large molecules from lots of smaller ones
- Changing one molecule to another
- Breaking down large molecules into smaller ones
What are the 2 ways that affect enzyme action?
Temperature and pH
How do temperatures affect the rate of enzyme action?
High temperatures denature the enzyme, changing the shape of the active site
How does pH affect the rate of enzyme action?
It either makes it work very efficiently or stop it working
What is denaturation?
When the active sites shape has changed and the substrate can no longer fit
What is digestion?
The breakdown of large insoluble molecules into soluble substances that can be absorbed into the blood across the wall of the small intestine
What are digestive enzymes produced by?
Specialised cells in glands and in the lining of the digestive system
What do carbohydrates such as amylase do?
Catalyse the breakdown of carbohydrates to simple sugars
What do proteases do?
Catalyse the breakdown of proteins to amino acids
What does catalyse mean?
Speed up
What does lipases do?
Catalyse the breakdown of lipids to fatty acids and glycerol
What does amylase break down starch into?
Simple sugars
What is the steps for testing the effect of pH on the rate of reaction of amylase?
- Place one drop of iodine solution into each well of a spotting tile
- Put 2cm cubes of starch solution into a test tube, 2cm cubed of amylase solution into another and 2cm cubed of pH 5 buffer solution into a final test tube
- Place all 3 test tubes in a water bath at 30 degrees celcuis for 10 minuites
- Combine the 3 solution into 1 test tube and mix with a stirring rod
- Put the mixture into the water bath and start a stop watch
- After 30 seconds, put 1 drop of solution to a well in the spotting tile, this is should turn blue/black
- Repeat this every 30 seconds untill the iodine remains orange
- This shows starch is no longer present
- Record the time for this in a table
- Repeat this several times but using different pH buffers eg pH 7
What is wrong with taking a measurement every 30 seconds?
It only gives a rough time eg the reaction could be complete after 121 seconds for 149
Where do protease enzymes of the stomach work best in?
Acidic/ acid conditions
How does the stomach help protease enzymes work effectively?
By producing hydrochloric acid which maintains a low pH
Enzymes of the pancreas and the small intestine work best in what conditions?
Alkaline solutions
What does bile produced by the liver and released through bile ducts do?
Neutralises acid and emulsifies fats
