Q6. The atom shown below has _______ electrons, _________ protons, and ________ neutrons.

Background

Topic: Atomic Structure

This question tests your understanding of the basic structure of an atom, including the arrangement and number of subatomic particles: electrons, protons, and neutrons.

Key Terms and Formulas

• Electron: Negatively charged particle found in electron shells surrounding the nucleus.

• Proton: Positively charged particle found in the nucleus.

• Neutron: Neutral particle found in the nucleus.

• Atomic Number: Number of protons in the nucleus.

• Mass Number: Sum of protons and neutrons in the nucleus.

Step-by-Step Guidance

1. Examine the diagram carefully. Count the number of black dots (electrons) in the electron shells.

2. Count the number of red spheres with plus signs (protons) in the nucleus.

3. Count the number of yellow spheres (neutrons) in the nucleus.

4. Recall that the atomic number equals the number of protons, and for a neutral atom, the number of electrons equals the number of protons.

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Q13. These structural variations of hydrogen are called _____________________. Which subatomic particle can vary in number among these three structural variations?

Background

Topic: Isotopes

This question is about isotopes, which are atoms of the same element with different numbers of neutrons.

Key Terms and Formulas

• Isotope: Atoms of the same element with different numbers of neutrons.

• Proton: Determines the element; does not change among isotopes.

• Neutron: Varies among isotopes, affecting mass number.

Step-by-Step Guidance

1. Observe the three diagrams: each has one proton (red sphere with plus sign) and one electron (black dot).

2. Count the number of neutrons (yellow spheres) in each diagram: hydrogen has none, deuterium has one, tritium has two.

3. Recall that isotopes are defined by their differing numbers of neutrons, while the number of protons remains the same.

4. Identify the term for these variations and the subatomic particle that changes.

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Q5. Explain why the overall reaction for cellular respiration (shown below) is never reversed in body cells.

Background

Topic: Cellular Respiration and Metabolic Reactions

This question tests your understanding of the directionality of metabolic reactions, specifically why cellular respiration is considered irreversible in living cells.

Key Terms and Formulas

• Cellular Respiration: The process by which cells break down glucose and oxygen to produce carbon dioxide, water, and ATP (energy).

• Irreversible Reaction: A reaction that cannot easily be reversed under normal physiological conditions.

• ATP: Adenosine triphosphate, the energy currency of the cell.

Step-by-Step Guidance

1. Examine the chemical equation: .

2. Consider the energy released during the breakdown of glucose; this energy is captured in ATP and lost as heat.

3. Think about the physiological conditions in cells: the products (CO2 and H2O) are removed from the cell, making reversal difficult.

4. Reflect on why the cell cannot easily convert CO2 and H2O back into glucose under normal conditions.

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Q11. The bicarbonate buffer system shown below resists changes in blood pH by shifting to the right or left in response to a rise or drop in pH.

Background

Topic: Acid-Base Balance and Buffer Systems

This question tests your understanding of how the bicarbonate buffer system maintains blood pH by shifting equilibrium in response to changes in acidity.

Key Terms and Formulas

• Buffer: A system that resists changes in pH by absorbing or releasing H+ ions.

• Bicarbonate Buffer System:

• Equilibrium Shift: Movement to the right or left depending on pH changes.

Step-by-Step Guidance

1. Examine the equation: .

2. Consider what happens when blood becomes more acidic (increase in H+ ions).

3. Think about which direction the equilibrium will shift to remove excess H+ ions.

4. Determine whether this shift results in the addition or removal of H+ ions from the blood.

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Q7. Why do phospholipids form a bilayer (shown below) when placed in a watery environment? (In your answer be sure to indicate which parts of a phospholipid are polar or nonpolar.)

Background

Topic: Cell Membrane Structure

This question tests your understanding of the amphipathic nature of phospholipids and how this leads to the formation of a bilayer in aqueous environments.

Key Terms and Formulas

• Phospholipid: A molecule with a polar (hydrophilic) head and nonpolar (hydrophobic) tails.

• Bilayer: Two layers of phospholipids with heads facing outward toward water and tails facing inward away from water.

• Hydrophilic: Water-loving, polar.

• Hydrophobic: Water-fearing, nonpolar.

Step-by-Step Guidance

1. Identify the structure of a phospholipid: a polar head and two nonpolar tails.

2. Recall that polar heads interact with water, while nonpolar tails avoid water.

3. Explain how phospholipids arrange themselves in a bilayer: heads face outward toward water, tails face inward away from water.

4. Consider why this arrangement is stable in a watery environment.

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Q5. When cooking an egg (shown below) what is the term that describes what happens to the protein albumin to cause the coagulation of egg white?

Background

Topic: Protein Structure and Denaturation

This question tests your understanding of how heat affects protein structure, specifically the process that causes proteins to lose their native shape and coagulate.

Key Terms and Formulas

• Denaturation: The process by which proteins lose their three-dimensional structure due to external stress (such as heat).

• Albumin: The main protein in egg white.

• Coagulation: The process of proteins clumping together after denaturation.

Step-by-Step Guidance

1. Consider what happens to proteins when exposed to heat: their structure unfolds.

2. Recall the term for this process: denaturation.

3. Understand that denatured proteins can aggregate, leading to coagulation.

4. Apply this concept to the cooking of egg whites, where albumin proteins denature and coagulate.

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