Q: A solution has a pH of 4. What is the concentration of hydrogen ions ($$[H^+]) in $$this solution, and how does it compare to a solution with pH 7?

The concentration of $$[H^+] is$$ $$1 \times 10$$^{-4}$$ M, which is 1,000 times higher than a solution with pH 7.

Question 1

Which of the following best explains why ice floats on liquid water, and why this property is crucial for aquatic life in cold climates?

Accepted Answer

Ice is less dense than liquid water because stable hydrogen bonds hold water molecules apart, creating a crystalline structure with fewer molecules per volume.

Question 2

A solution has a pH of 4. What is the concentration of hydrogen ions ($$[H^+]) in $$this solution, and how does it compare to a solution with pH 7?

Accepted Answer

The concentration of $$[H^+] is$$ $$1 	imes 10$$^{-4}$$ M, which is 1,000 times higher than a solution with pH 7.

Question 3

Which type of chemical bond is responsible for the formation of table salt (NaCl), and what is the process by which this bond forms?

Accepted Answer

Ionic bond; sodium transfers an electron to chlorine, resulting in oppositely charged ions that attract each other.

Question 4

Which property of water allows it to moderate Earth's climate and regulate temperature in living organisms?

Accepted Answer

Water's high heat capacity due to hydrogen bonding, which allows it to absorb and release large amounts of heat with minimal temperature change.

Question 5

A patient is diagnosed with acidosis, meaning their blood pH has dropped below normal. Which biological mechanism helps minimize changes in blood pH?

Accepted Answer

Buffers, which accept excess $$H^+$$ ions to minimize changes in pH.

Question 6

Which of the following statements about carbon is TRUE and explains why life on Earth is carbon-based?

Accepted Answer

Carbon can form up to four covalent bonds, allowing for large, branched, and diverse molecules.

Question 7

Which process is responsible for breaking down polymers into monomers during digestion, and what molecule is required for this reaction?

Accepted Answer

Hydrolysis; water is added to break bonds between monomers.

Question 8

Which class of organic molecules is the most diverse in structure and function, and what determines their specific function?

Accepted Answer

Proteins; their function is determined by the precise amino acid sequence and three-dimensional shape.

Question 9

A person chews a starchy cracker and notices it tastes sweet after a few minutes. Which biological process explains this change?

Accepted Answer

Enzymes in saliva (amylase) break down starch (a polysaccharide) into simple sugars (monosaccharides) through hydrolysis.

Question 10

Which of the following best describes the difference between saturated and unsaturated fats?

Accepted Answer

Saturated fats have single bonds and straight chains, making them solid at room temperature; unsaturated fats have double bonds and bent chains, making them liquid at room temperature.

Question 11

Which of the following is a function of cholesterol in animal cells?

Accepted Answer

Maintaining membrane fluidity and serving as a precursor for steroid hormones.

Question 12

Which of the following statements about enzymes is correct?

Accepted Answer

Enzymes lower the activation energy required for chemical reactions, allowing them to proceed faster.

Question 13

A competitive inhibitor affects enzyme activity by:

Accepted Answer

Binding to the enzyme's active site, preventing the substrate from binding.

Question 14

Which of the following is TRUE about the structure of phospholipids in cell membranes?

Accepted Answer

Phospholipids have hydrophilic heads and hydrophobic tails, forming a bilayer that separates the cell from its environment.

Question 15

Which of the following is a real-world consequence of increased atmospheric $$CO_2$$ and ocean acidification?

Accepted Answer

Lower pH impairs the ability of marine organisms to build skeletons or shells, threatening ecosystem health.

Question 16

Which equation correctly represents the relationship between pH and hydrogen ion concentration?

Accepted Answer

$$pH = -\log_{10} [H^+]$$

Question 17

Which of the following is a polymer made by joining many glucose monomers in animals?

Accepted Answer

Glycogen

Question 18

Which process is used by cells to build new macromolecules from monomers, and what is removed during this reaction?

Accepted Answer

Dehydration synthesis; a molecule of water is removed to link monomers together.

The Chemistry of Life: Foundations for General Biology

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