Biological Molecules Flashcards
What molecules are present in living organisms?
Carbohydrates
Protiens
Lipids
What are the chemical elements in the three molecules?
Carbohydrates: Carbon, Oxygen and Hydrogen.
Protein: Same as carbs but includes Hydrogen, Nitrogen and small amounts of other elements like Sulphur.
Lipid: Same as Carbs
What is the structure of Carbohydrates?
Basic unit of all carbohydrates are simple sugars
Glucose is a simple sugar ( a monosaccharide)
When 2 glucose molecules join together maltose is formed (a disaccharide)
When lots of glucose molecules join together starch or glycogen is formed (polysaccharides).
What is the structure of Proteins?
The basic unit of all protein molecules is the amino acid
There are about 20 different amino acids
They all contain the same basic structure but the ‘R’ group is different for each one
When amino acids are joined together a protein is formed
The amino acids can be arranged in any order, resulting in hundreds of thousands of different proteins
Even a small difference in the order of the amino acids results in a different protein being formed.
What is the structure of Lipids?
Most lipids in the body are made up of triglycerides
Their basic unit is 1 glycerol molecule and 3 fatty acid chains
The fatty acids vary in size and structure
Lipids are divided into fats (solids at room temperature) and oils (liquids at room temperature).
What is the food test for Glucose?
Add Benedict’s solution into sample solution in test tube
Heat at 60 – 70 °c in water bath for 5 minutes
Take test tube out of water bath and observe the color
A positive test will show a color change from blue to orange or brick red.
What is the test for Starch?
Add drops of iodine solution to the food sample
A positive test will show a color change from brown to blue-black
What is the food test for Protein?
Add drops of Biuret solution to the food sample
A positive test will show a color change from blue to violet / purple.
What is the food test for Lipids?
Food sample is mixed with 2cm3 of ethanol and shaken
The ethanol is added to an equal volume of cold water
A positive test will show a cloudy emulsion forming.
What are enzymes?
Are proteins
Are biological catalysts (biological because they are made in living cells, catalysts because they speed up the rate of chemical reactions)
Are specific to one particular substrate as the active site of the enzyme, where the substrate attaches, is a complementary shape to the substrate – known as the lock and key hypothesis
Are affected by changes in temperature and pH
Are not used up in the reaction they catalyze.
What is the effect of temperature on enzymes?
Enzymes are proteins and have a specific shape, held in place by bonds. This is extremely important around the active site area as the specific shape is what ensures the substrate will fit into the active site and enable the reaction to proceed.
Enzymes work fastest at their ‘optimum temperature’ – in the human body, the optimum temperature is 37⁰C.
Heating to high temperatures (beyond the optimum) will break the bonds that hold the enzyme together and it will lose its shape. This is known as denaturation. Substrates cannot fit into denatured enzymes as the shape of their active site has been lost.
Denaturation is irreversible – once enzymes are denatured they cannot regain their proper shape and activity will stop.
Increasing the temperature from 0⁰C to the optimum increases the activity of enzymes as the more energy the molecules have the faster they move and the number of collisions with the substrate molecules increases, leading to a faster rate of reaction.
This means that low temperatures do not denature enzymes, they just make them work more slowly.
What is the practical effect of temperature on enzymes?
The starch solution is heated to a set temperature
Iodine is added to wells of a spotting tile
Amylase is added to the starch solution and mixed well
Every minute, droplets of solution are added to a new well of iodine solution
This is continued until the iodine stops turning blue-black (this means there is no more starch left in the solution as the amylase has broken it all down)
Time taken for the reaction to be completed is recorded
The experiment is repeated at different temperatures
The quicker the reaction is completed, the faster the enzyme is working.
What is the effect of PH on enzymes?
The optimum pH for most enzymes is 7 but some that are produced in acidic conditions, such as the stomach, have a lower optimum pH (pH 2) and some that are produced in alkaline conditions, such as the duodenum, have a higher optimum pH (pH 8 or 9)
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
This will change the shape of the active site, so the substrate can no longer fit in
The enzyme will denature and activity will stop.
Practical: Effect on PH
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.
