Biological Molecules and Food Tests Flashcards
What chemicals is the human body made up of?
65% oxygen
18% carbon
10% hydrogen
7% other elements
These elements combine to form all the compounds in the body
What 3 groups do most molecules found in living organisms fall into?
Carbohydrates
Proteins
Lipids
What are carbohydrates made up of?
Simple sugars
Formed from carbon, oxygen and hydrogen
Give an example of a simple sugar carbohydrate.
Glucose
Sucrose
Give an example of a larger moleculed carbohydrate.
Starch
Glycogen
What are proteins made up of?
Chains of amino acids linked together.
What are lipids?
What we often call fats.
Made up from fatty acids and glycerol
There are 3 fatty acids and glycerol in each lipid
Lipids contain carbon, hydrogen and oxygen atoms
What is the test for glucose (and other reducing sugars)?
Benedict’s reagent test
Blue Benedict’s reagent is added to samples and heated.
Green = small amount of reducing sugars
Yellow = medium amount of reducing sugars
Orange/red = large amount of reducing sugars
What is the test for starch?
Iodine solution is added to food sample.
If it changes from brown to blue black starch is present.
What is a catalyst?
A substance that helps to speed up a reaction.
What are catalysts that cause metabolic reactions inside cells in living organisms called?
Enzymes or biological enzymes
What would happen if we did not have enzymes?
Metabolic reactions would happen too slowly for life to carry on.
What are biological enzymes made of?
Proteins
Are enzymes general or specific?
Specific - they only work with one substance- substrate
What is amylase?
Type of carbohydrase enzyme
Produced in the mouth
Starts the digestion of starch in food into simple sugars
What is protease?
Digestive enzymes that break proteins into smaller units.
What is lipase?
Digestive enzyme that breaks down lipids in food.
What temperature do enzymes work best at?
At a particular temperature known as their optimum temperature
35-40*c for human enzymes
At a lower temperature they work more slowly as the molecules have less energy.
At temperatures that are too high the structure of the enzyme changes so will not work - it has become denatured.
How can pH affect enzymes?
Very high or very low can slow down the rate of reaction and can in some case denature them.
What is a test for protein?
Biuret Test
Prepare a sample of food and transfer 2cm3 to a test tube.
Add 2cm3 of biuret solution and gently shake.
If protein present solution changes colour from blue to pink/purple. If not present then remains blue.
What is a test for lipids?
Sudan III test
Prepare a sample of food.
Transfer 5cm3 into a test tube
use a pipette to add 3 drops of Sudan III stain solution and gently shake
Sudan III stain solution stains lipids. If the sample has lipids it will separate into 2 layers. The top layer will be bright red. If there are no lipids then no separate red layer will form.
