The diagrams show four molecules. C represents carbon, H represents hydrogen, O represents oxygen and N represents nitrogen. Which structure is an amino acid?
▶️ Answer/Explanation
Ans: B
An amino acid has a central carbon bonded to an amino group (\(\text{NH}_2\)), a carboxyl group (\(\text{COOH}\)), a hydrogen atom, and a variable R-group. Structure B matches this configuration, while the others lack either the amino or carboxyl group. Thus, the correct answer is B.
Which statement about biological molecules is correct?
A) DNA molecules contain pairs of bases: A pairs with G and C pairs with T.
B) Fatty acids and glycerol molecules can be joined together to form proteins.
C) Glucose molecules can be joined together to make cellulose and glycogen.
D) Starch molecules are made of maltase.
▶️ Answer/Explanation
Ans: C
Option C is correct because glucose monomers polymerize to form polysaccharides like cellulose (plant cell walls) and glycogen (energy storage in animals).
Option A is incorrect as DNA base pairing follows Chargaff’s rules (A-T, C-G). Option B is wrong because fatty acids and glycerol form lipids, not proteins. Option D is false since starch is made of amylose/amylopectin, not maltase (an enzyme).