Q: A solution has a pH of 4. What is the hydrogen ion concentration $$[H^+] of $$this solution?

$$[H^+] = 1 \times 10$$^{-4}$$\ \mathrm{M}$$

Question 1

A pharmaceutical company is testing a new drug. In their clinical trial, neither the patients nor the researchers know who is receiving the drug or the placebo. What is this experimental design called, and why is it important?

Accepted Answer

Double-blind; it reduces both patient and researcher bias.

Question 2

Which of the following best describes the difference between an independent and a dependent variable in a scientific experiment?

Accepted Answer

The independent variable is manipulated by the researcher, and the dependent variable is what is measured as a result.

Question 3

Which of the following functional groups is found in all amino acids and is responsible for their acidic properties?

Accepted Answer

Carboxyl group ($$-COOH)$$

Question 4

A solution has a pH of 4. What is the hydrogen ion concentration $$[H^+] of $$this solution?

Accepted Answer

$$[H^+] = 1 	imes 10$$^{-4}$$\ \mathrm{M}$$

Question 5

Which type of bond is primarily responsible for holding together the two strands of DNA in a double helix?

Accepted Answer

Hydrogen bonds

Question 6

Which of the following best explains why cellulose cannot be digested by humans, while glycogen can?

Accepted Answer

Cellulose is composed of beta-glucose monomers, while glycogen is composed of alpha-glucose monomers.

Question 7

Which of the following reactions is responsible for joining two amino acids together to form a dipeptide?

Accepted Answer

Dehydration (condensation)

Question 8

A researcher adds a strong acid to a solution, causing the pH to drop from 7 to 3. By what factor has the hydrogen ion concentration increased?

Accepted Answer

10,000-fold

Question 9

Which of the following best distinguishes a phospholipid from a triglyceride?

Accepted Answer

Phospholipids contain a phosphate group and two fatty acids; triglycerides contain three fatty acids and no phosphate group.

Question 10

Which of the following statements about optical isomers of glucose is correct?

Accepted Answer

Alpha-glucose and beta-glucose are optical isomers that differ in the orientation of the hydroxyl group on carbon 1.

Question 11

Which intermolecular force is primarily responsible for the secondary structure (alpha-helix and beta-sheet) of proteins?

Accepted Answer

Hydrogen bonds

Question 12

Which of the following best describes the relationship between nucleotides and nucleic acids?

Accepted Answer

Nucleotides are the monomers that polymerize to form nucleic acids via phosphodiester bonds.

Question 13

A scientist is studying a molecule with the following structure: a central carbon, an amino group ($$-NH_2$), a carboxyl group (-$$COOH$$), a hydrogen atom, and a variable R group. What type of molecule is this?

Accepted Answer

An amino acid

Question 14

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

Accepted Answer

Water is polar and can form hydrogen bonds with solutes.

Question 15

Which of the following correctly matches a biomolecule with its primary function?

Accepted Answer

Carbohydrates: provide energy storage and structural support

Question 16

Which of the following best describes a glycosidic bond?

Accepted Answer

A bond formed between two monosaccharides during a dehydration reaction

Question 17

A patient is given a buffer solution to maintain their blood pH. Which property of buffers allows them to resist changes in pH when small amounts of acid or base are added?

Accepted Answer

Buffers contain both a weak acid and its conjugate base, allowing them to absorb excess $$H^+ or$$ $$OH^-$$ ions.

Question 18

Which of the following best explains the difference between dehydration and hydrolysis reactions in biological systems?

Accepted Answer

Dehydration reactions join monomers by removing water; hydrolysis reactions break polymers by adding water.

Question 19

Which of the following statements about van der Waals forces is correct?

Accepted Answer

They are weak interactions that occur between nonpolar molecules.

Question 20

Which functional group is found in ATP and is critical for its role in energy transfer?

Accepted Answer

Phosphate group ($$-PO_4$^{3-})$$

Key Concepts in Biological Chemistry and Biomolecules

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