Topic 4 Flashcards
(20 cards)
What chemical elements are present in carbohydrates?
Carbon, hydrogen, oxygen (C,H,O)
What chemical elements are present in lipids?
Carbon, hydrogen and oxygen (C,H,O)
What chemical elements are present in proteins?
Carbon, hydrogen, oxygen, nitrogen and sulfur (C,H,O,N,S)
What smaller molecules are starch and glycogen made from?
Glucose
What smaller molecule is cellulose made from?
Glucose
What smaller molecules are proteins made of?
Amino acids
What smaller molecules are fats and oils made from?
Fatty acids and glycerol
How do you test for starch?
Add iodine to the sample
What will you observe in a positive test for starch?
The yellow/brown solution turns blue/black
How do you test for reducing sugars e.g. glucose?
Add a few drops of Benedict’s solution, warm in a water bath for 3 minutes at about 80 degrees
What will you observe in a positive test for reducing sugars?
The more reducing sugar present, the closer to red the colour is
How do you test for proteins?
Add equal volumes of Biuret A (copper sulfate) and Biuret B (sodium hydroxide) to the sample and shake
What will you observe in a positive test for protein?
The solutions turns from blue to purple
How do you test for lipids?
Add 2cm3 of ethanol to the sample
Leave to dissolve
Add 2cm3 of distilled water to the sample
What will you observe in a positive test for lipids?
A cloudy white emulsion will form
How do you test for Vitamin C?
Add DCPIP to the solution drop by drop until the solution permanently changes colour
What will you observe in a positive test for Vitamin C?
The solution will turn the DCPIP from dark blue to colourless permanently
Describe the structure of DNA
It is a polymer made of many nucleotide monomers
It is made of 2 strands in the shape of a double helix
Each strand contains bases (A, T, C, G)
The 2 strands are linked between the bases
Give the 4 bases in DNA
A, T, G, C
How do the bases in DNA pair up
A always pairs with T
C always pairs with G
