Lab 4 and 5 Flashcards
(17 cards)
Carbohydrates
Simple sugar (glucose)
Organic compounds made of carbon (C), hydrogen (H), and oxygen (O), usually in a 1:2:1 ratio.
(simple sugar), like glucose. This is also called a monomer.
Two monosaccharides form a disaccharide (e.g., sucrose). Many joined together make polysaccharides (complex carbs) like starch, cellulose, and glycogen.
Monomers are the building blocks, and polymers are the larger molecules they form.
How do you test for reducing sugars?
Benedict’s reagent test is used to test for reducing sugars. This test is based on the ability of reducing sugars to reduce copper ions in the Benedict’s reagent from its oxidized cupric ion form to cuprous ion. This reduction of copper ion is accompanied by a color change from blue (cupric ion) to green, orange or reddish brown (cuprous ion).
Benedicts reagent test: Testing for reduced sugars
Lipids
Organic compounds that are water haters (HYDROPHOBIC).
Lipids are soluble in organic solvents like acetone.
Lipids are made of fatty acids and glycerol.
Lipids are also a source of energy; long term energy storage molecules!
How do you test for lipids?
Oil red dye test is used to detect lipids. Oil red dye is a lipid soluble dye and when added to lipids, lipids selectively absorb the red pigment in the dye and appear as a red colored layer on the top, separated from the bottom layer of water
If there are 23 peptide bonds in a polypeptide, how many amino acids does this polypeptide contain?
24 amino acids
Nucleic Acids
Two types of nucleic acids are DNA and RNA. DNA is a double strand molecule and RNA is a single strand.
Nucleic acids are made of nucleotides.
Each nucleotide is made of a sugar, a nitrogenous base, and a phosphate group. Therefore nucleotide is a monomer of nucleic acids that form polymers of nucleic acids like DNA and RNA.
Amino Acid is monomer of what?
Protein
How do you test for Proteins?
Biuret test helps detect proteins. Biuret reagent contains copper ions (Blue) that interact with the peptide bonds in proteins to give a violet color. Therefore if you add Biuret reagent to free amino acids that don’t have a peptide bond, you will get a negative result.
Monomers and Polymers relationship to energy
Monomers are instant source of energy while Polymers are storage for long term energy
Benedict’s Reagent
(Blue to Brown)
This test is based on the ability of reducing sugars to reduce copper ions in the Benedict’s reagent from its oxidized cupric ion form to cuprous ion. This reduction of copper ion is accompanied by a color change from blue (cupric ion) to green, orange or reddish brown (cuprous ion). Therefore a sugar or a carbohydrate has to be a reducing sugar in order to give a positive test for Benedict’s reagent test.
How do you perform Benedict’s test?
Add the substance to be tested in a tube. Add 2 ml of Benedict’s solution to the substance already in the tube. Heat the tube in a boiling water bath for 3 minutes and observe the color change.
Result: A positive test will vary between green to reddish brown
If the color stays blue then the test for reducing sugar is negative!
How do you test for a complex carbohydrate like starch?
Iodine test is used to test for starch. Iodine interacts with the complex structure of starch to give a bluish-black color. Therefore only starch will give a positive test for Iodine test.
How many amino acids in our body?
20 amino acids in the body
Amino acids and Biuret reagent
if you add Biuret reagent to free amino acids that don’t have a peptide bond, you will get a negative result.
More about Nucleic Acids
Therefore nucleotide is a monomer of nucleic acids that join together to form polymers of nucleic acids like DNA and RNA.
Nucleic acids are made of nucleotides. Each nucleotide is made of a sugar, a nitrogenous base, and a phosphate group.
Lipids- Triglycerides - Saturated and unsaturated
Saturated
Fatty acid chains have no double bonds between carbon atoms.
Chains are straight and pack tightly — usually solid at room temperature.
EXAMPLES: Animal fats (butter, lard), some tropical oils (coconut oil).
✅ Unsaturated
Fatty acid chains have one or more double bonds.
Monounsaturated: One double bond
Polyunsaturated: Two or more double bonds
Chains have kinks (due to double bonds), so they pack loosely — usually liquid at room temperature.
EXAMPLES: Olive oil (monounsaturated), fish oil and sunflower oil (polyunsaturated)
Nucleotides subunits
Phosphate, nitrogen and sugar
