Question 1

Which of the following statements best explains why carbon is able to form such a wide variety of organic molecules?

Accepted Answer

Carbon has four valence electrons, enabling it to form four covalent bonds with a variety of atoms.

Question 2

A radioactive isotope of carbon, $$^{14}C$$, is used in radiocarbon dating. Which of the following is true about $$^{14}C$$ compared to the most common carbon isotope, $$^{12}C$$?

Accepted Answer

$$^{14}C$$ has the same number of protons but more neutrons than $$^{12}C.$$

Question 3

Which of the following best describes a dehydration reaction in the synthesis of a polymer?

Accepted Answer

A water molecule is removed, allowing two monomers to bond together.

Question 4

A solution has a hydrogen ion concentration of $$[H^+] = 1 	imes 10$$^{-5}$$ M. What is the pH of this solution?

Accepted Answer

$$pH = 5$$

Question 5

Which of the following is a correct statement about the structure of DNA?

Accepted Answer

DNA consists of two antiparallel strands held together by hydrogen bonds between complementary bases.

Question 6

Which of the following best explains why unsaturated fats are liquid at room temperature while saturated fats are solid?

Accepted Answer

Unsaturated fats have double bonds that create kinks, preventing tight packing of molecules.

Question 7

A protein is exposed to high heat and extreme pH, causing it to lose its functional shape. What is this process called?

Accepted Answer

Denaturation

Question 8

Which of the following functional groups is most likely to act as an acid by donating a proton ($$H^+) to $$solution?

Accepted Answer

Carboxyl group ($$-COOH)$$

Question 9

Which of the following best describes the role of phospholipids in biological membranes?

Accepted Answer

They form a bilayer with hydrophobic tails facing inward and hydrophilic heads facing outward.

Question 10

Which of the following is an example of a structural polysaccharide and its biological function?

Accepted Answer

Cellulose; structural support in plant cell walls

Question 11

A molecule with the formula $$C_6H_{12}O_6$ is classified as which of the following?

Accepted Answer

A monosaccharide

Question 12

Which of the following best describes the difference between an aldose and a ketose sugar?

Accepted Answer

An aldose has a carbonyl group at the end of the carbon skeleton; a ketose has it within the skeleton.

Question 13

Which of the following statements about ATP (adenosine triphosphate) is correct?

Accepted Answer

ATP stores energy in the bonds between its phosphate groups, which is released when it reacts with water.

Question 14

Which of the following best describes the primary structure of a protein?

Accepted Answer

The unique sequence of amino acids in a polypeptide chain

Question 15

A DNA strand has the sequence 5'-AGGTTAC-3'. What is the complementary sequence on the other strand?

Accepted Answer

3'-TCCAATG-5'

Question 16

Which of the following is a correct statement about isomers?

Accepted Answer

Isomers have the same molecular formula but different structures and properties.

Question 17

Which of the following best explains why cholesterol is important in animal cell membranes?

Accepted Answer

Cholesterol helps maintain membrane fluidity and stability.

Question 18

Which of the following best describes the role of buffers in biological systems?

Accepted Answer

Buffers minimize changes in the concentrations of $$H^+$$ and $$OH^- in a $$solution.

Question 19

Which of the following is a correct description of a glycosidic linkage?

Accepted Answer

A covalent bond formed between two monosaccharides by a dehydration reaction

Question 20

Which of the following best explains why water is an effective solvent for polar and ionic substances?

Accepted Answer

Water molecules are polar, allowing them to surround and interact with charged and polar molecules.

Atoms, Water, Carbon, and the Molecular Basis of Life

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