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biology - u03al3: macromolecules hw

1. which of the following makes carbohydrates unique from the other macromolecules?

a. long - term energy storage is provided by carbohydrates
b. carbohydrates contain a 1:2:1 ratio of carbon to hydrogen to oxygen.
c. the monomers in carbohydrates are held together by peptide bonds.
d. carbohydrates are polymers that always form a ring structure.

1. **which of the following is a characteristic of lipids?

a. they are composed of nitrogenous chains.
b. they are not soluble in water.
c. they are either fats or oils.
d. they are polar (charged) molecules.

1. **which of the following statements is true regarding dna structure?

a. in dna, purines pair together and pyrimidines pair together.
b. dna is single - stranded.
c. dna is composed of amino acids.
d. dna forms a double helix.

1. which of the following statements is accurate regarding protein structure?

a. in proteins, purines pair together and pyrimidines pair together.
b. proteins are single - stranded.
c. proteins are composed of amino acids.
d. proteins form a double helix.

1. *which of the following are functions of proteins? you may choose more than one.

a. catalyzing chemical reactions
b. energy storage
c. encoding genetic information
d. cell signaling

Explanation:

1. Question 1:

• Option a: Long - term energy storage is mainly provided by lipids, not carbohydrates (carbohydrates are for short - term energy).
• Option b: Carbohydrates have a general formula \(C_nH_{2n}O_n\), which gives a \(1:2:1\) ratio of carbon to hydrogen to oxygen.
• Option c: Peptide bonds are in proteins (between amino acids), not in carbohydrates (glycosidic bonds in carbohydrates).
• Option d: Not all carbohydrates form ring structures (e.g., some linear polysaccharides).

1. Question 2:

• Option a: Lipids are not composed of nitrogenous chains (proteins and nucleic acids have nitrogen - containing components).
• Option b: Lipids are non - polar and not soluble in water (hydrophobic).
• Option c: Lipids include fats, oils, phospholipids, steroids etc., not just fats and oils.
• Option d: Lipids are non - polar (except for some parts of phospholipids, but overall they are non - polar).

1. Question 3:

• Option a: In DNA, purines (A, G) pair with pyrimidines (T, C) (A - T, G - C).
• Option b: DNA is double - stranded.
• Option c: DNA is composed of nucleotides (not amino acids, which are in proteins).
• Option d: DNA forms a double - helix structure as discovered by Watson and Crick.

1. Question 4:

• Option a: Purine - pyrimidine pairing is in nucleic acids (DNA and RNA), not in proteins.
• Option b: Proteins have complex 3 - D structures (primary, secondary, tertiary, quaternary), not just single - stranded.
• Option c: Proteins are composed of amino acids linked by peptide bonds.
• Option d: Double - helix is a DNA structure.

1. Question 5:

• Option a: Enzymes (which are proteins) catalyze chemical reactions.
• Option b: Energy storage is mainly by carbohydrates (short - term) and lipids (long - term), not the main function of proteins.
• Option c: Encoding genetic information is the function of nucleic acids (DNA and RNA).
• Option d: Proteins are involved in cell signaling (e.g., receptor proteins).

Answer:

1. B. Carbohydrates contain a \(1:2:1\) ratio of carbon to hydrogen to oxygen.
2. B. They are not soluble in water.
3. D. DNA forms a double helix.
4. C. Proteins are composed of amino acids.
5. A. Catalyzing chemical reactions; D. Cell signaling.