38 Questions
What is the term used to describe the four classes of biological molecules?
Biomolecules
Which type of molecules are composed of nucleotides?
Nucleic acids
What is the purpose of the Benedict's Test?
To detect the presence of reducing sugars
What is the result of the reaction between cupric ions and certain sugars in the Benedict's Test?
The formation of an insoluble reddish precipitate
What are the main components of lipids?
Fatty acids and glycerol
What is the term used to describe the building blocks of carbohydrates?
Monosaccharides
Which of the following is an example of a nucleic acid?
RNA
What is the color of the Benedict's solution?
Blue
What is the result of heating the Benedict's solution with certain sugars?
The solution changes from blue to green to reddish brown
What is the primary source of carbohydrate in our diets?
Starch
What is the result of a positive starch test?
A bluish-black color
What is the function of copper sulfate in the Biuret reagent?
To react with peptide bonds
What is the minimum number of linked amino acids required for a positive Biuret test?
4
What is the result of a negative Biuret test?
A blue color
What is the purpose of the Sudan IV test?
To detect the presence of lipids
What is the characteristic of lipids in an aqueous solution?
They have a lower density than water
What is the result of a positive Sudan IV test?
A dark red-orange color
Why are positive and negative controls important in the Sudan IV test?
Because the test is the most challenging of the four
What happens to the Sudan reagent in a solution with lipids?
It stains the oil droplets a darker red-orange color
Lipids are made up of chains of amino acids.
False
All carbohydrates are reducing sugars.
False
Nucleic acids are composed of amino acids.
False
Benedict's solution is colorless.
False
A positive Benedict's test is indicated by a blue color.
False
Copper (I) oxide is formed when cupric ions react with certain sugars.
True
Macromolecules have the same structure and function in the body.
False
Glycerol is a type of carbohydrate.
False
A reddish precipitate of copper (I) oxide is formed when cuprous ions react with certain sugars.
False
Disaccharides always react with Benedict's reagent.
False
Starch is a type of protein.
False
Iodine is used to detect the presence of protein.
False
Biuret reagent reacts with peptide bonds to produce a yellowish-brown color.
False
Free amino acids will react with Biuret reagent.
False
Sudan IV is soluble in water.
False
A negative Sudan IV test result is indicated by a slightly darker red-orange color.
False
Lipids have a higher density than water.
False
A positive control is not necessary in the Sudan IV test.
False
The iodine test is used to detect the presence of protein in a solution.
False
Study Notes
Biological Molecules
- Living organisms are composed of molecules with diverse shapes and forms.
- The four main classes of biological molecules are carbohydrates, proteins, lipids, and nucleic acids.
Carbohydrates
- Complex carbohydrates are made up of monosaccharides.
- Some sugars, known as reducing sugars, contain free aldehyde or ketone groups.
- Reducing sugars can be detected using Benedict's Test.
Benedict's Test
- Benedict's solution is blue and contains cupric ions.
- When heated, cupric ions react with certain sugars, forming an insoluble reddish precipitate of copper (I) oxide.
- The solution changes color from blue to green to reddish brown depending on the amount of sugar present.
Starch
- Starch is a polysaccharide produced by plants to store sugars for later energy needs.
- Starch is a primary source of carbohydrate in our diets.
- Starch interacts with iodine to produce a bluish-black color.
Proteins
- Proteins are made up of chains of amino acids.
- Biuret reagent is used to test for the presence of protein.
- Biuret reagent contains copper sulfate, which reacts with peptide bonds, resulting in a violet/lavender color.
- Only proteins with four to six linked amino acids will react with Biuret reagent.
Lipids
- Lipids vary in composition, but main components include fatty acids and glycerol.
- Sudan IV test is used to detect the presence of lipids.
- Sudan IV is not soluble in water but is soluble in lipids.
- If lipids are present, the Sudan reagent will stain the oil droplets a slightly darker red-orange color.
Biological Molecules
- Living organisms are composed of molecules with diverse shapes and forms.
- The four main classes of biological molecules are carbohydrates, proteins, lipids, and nucleic acids.
Carbohydrates
- Complex carbohydrates are made up of monosaccharides.
- Some sugars, known as reducing sugars, contain free aldehyde or ketone groups.
- Reducing sugars can be detected using Benedict's Test.
Benedict's Test
- Benedict's solution is blue and contains cupric ions.
- When heated, cupric ions react with certain sugars, forming an insoluble reddish precipitate of copper (I) oxide.
- The solution changes color from blue to green to reddish brown depending on the amount of sugar present.
Starch
- Starch is a polysaccharide produced by plants to store sugars for later energy needs.
- Starch is a primary source of carbohydrate in our diets.
- Starch interacts with iodine to produce a bluish-black color.
Proteins
- Proteins are made up of chains of amino acids.
- Biuret reagent is used to test for the presence of protein.
- Biuret reagent contains copper sulfate, which reacts with peptide bonds, resulting in a violet/lavender color.
- Only proteins with four to six linked amino acids will react with Biuret reagent.
Lipids
- Lipids vary in composition, but main components include fatty acids and glycerol.
- Sudan IV test is used to detect the presence of lipids.
- Sudan IV is not soluble in water but is soluble in lipids.
- If lipids are present, the Sudan reagent will stain the oil droplets a slightly darker red-orange color.
This quiz covers the four major classes of biological molecules, including carbohydrates, proteins, lipids, and nucleic acids, and their building blocks.
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