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Microbiology Exam 2 Study Guide – Step-by-Step Guidance

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Study Guide - Smart Notes

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Q1. How would you recognize an endergonic versus an exergonic reaction?

Background

Topic: Metabolism & Bioenergetics

This question tests your understanding of energy changes in biochemical reactions, specifically how to distinguish between reactions that require energy input (endergonic) and those that release energy (exergonic).

Key Terms and Concepts:

  • Endergonic Reaction: A reaction that absorbs free energy from its surroundings (ΔG > 0).

  • Exergonic Reaction: A reaction that releases free energy (ΔG < 0).

  • ΔG (Gibbs Free Energy): Indicates whether a reaction is spontaneous or requires energy input.

Step-by-Step Guidance

  1. Recall that the sign of ΔG determines if a reaction is endergonic or exergonic.

  2. Think about whether the reaction requires energy input (e.g., ATP hydrolysis is often coupled to endergonic reactions).

  3. Consider if the products have more or less free energy than the reactants.

  4. Check if the reaction occurs spontaneously or only when coupled to another process.

Try solving on your own before revealing the answer!

Final Answer:

An endergonic reaction has a positive ΔG (ΔG > 0), meaning it requires energy input and is not spontaneous. An exergonic reaction has a negative ΔG (ΔG < 0), meaning it releases energy and occurs spontaneously. You can recognize them by whether energy is absorbed or released and by the sign of ΔG.

Q2. How would a cell force an endergonic reaction to occur?

Background

Topic: Metabolic Pathways & Energy Coupling

This question is about how cells drive non-spontaneous (endergonic) reactions by coupling them to exergonic reactions, often involving ATP hydrolysis.

Key Terms and Concepts:

  • Energy Coupling: Using the energy released from exergonic reactions to drive endergonic reactions.

  • ATP Hydrolysis: The breakdown of ATP to ADP + Pi, which releases energy (ΔG < 0).

Step-by-Step Guidance

  1. Recall that endergonic reactions require energy input (ΔG > 0).

  2. Think about how ATP hydrolysis is commonly used to provide this energy.

  3. Consider the concept of coupling reactions so that the overall ΔG is negative.

  4. Set up the combined reaction equation, showing both the endergonic and exergonic processes.

Try solving on your own before revealing the answer!

Final Answer:

A cell forces an endergonic reaction to occur by coupling it to an exergonic reaction, such as ATP hydrolysis. The energy released from ATP hydrolysis (ΔG < 0) is used to drive the endergonic process, making the overall reaction spontaneous (overall ΔG < 0).

Q3. What is the difference between competitive and non-competitive enzyme inhibition?

Background

Topic: Enzyme Regulation

This question tests your understanding of how enzyme activity can be regulated by inhibitors that affect the active site or other sites on the enzyme.

Key Terms and Concepts:

  • Competitive Inhibition: Inhibitor binds to the active site, blocking substrate binding.

  • Non-competitive Inhibition: Inhibitor binds to a different site (allosteric site), changing enzyme shape and function.

  • Active Site: The region of the enzyme where substrate binds.

  • Allosteric Site: A site other than the active site where molecules can bind and affect enzyme activity.

Step-by-Step Guidance

  1. Recall that competitive inhibitors resemble the substrate and compete for the active site.

  2. Non-competitive inhibitors bind elsewhere, not at the active site.

  3. Think about how each type of inhibition affects enzyme kinetics (Vmax and Km).

  4. Consider how increasing substrate concentration affects each type of inhibition.

Try solving on your own before revealing the answer!

Final Answer:

Competitive inhibition occurs when the inhibitor binds to the active site, preventing substrate binding; it can be overcome by increasing substrate concentration. Non-competitive inhibition occurs when the inhibitor binds to an allosteric site, changing the enzyme's shape and reducing activity regardless of substrate concentration.

Q4. What are the three stages of cellular respiration?

Background

Topic: Cellular Respiration

This question tests your knowledge of the main stages of cellular respiration and their sequence in both prokaryotes and eukaryotes.

Key Terms and Concepts:

  • Glycolysis: The breakdown of glucose to pyruvate.

  • Krebs Cycle (Citric Acid Cycle): Oxidation of acetyl-CoA to CO2 and electron carriers.

  • Electron Transport Chain (ETC): Transfer of electrons to generate ATP via chemiosmosis.

Step-by-Step Guidance

  1. List the three main stages of cellular respiration in order.

  2. Recall where each stage occurs in prokaryotes and eukaryotes.

  3. Think about the main inputs and outputs of each stage.

  4. Consider which stages require oxygen and which do not.

Try solving on your own before revealing the answer!

Final Answer:

The three stages of cellular respiration are: (1) Glycolysis, (2) Krebs Cycle (Citric Acid Cycle), and (3) Electron Transport Chain (ETC) with chemiosmosis. Glycolysis occurs in the cytoplasm, the Krebs cycle in the mitochondrial matrix (or cytoplasm in prokaryotes), and the ETC in the inner mitochondrial membrane (or plasma membrane in prokaryotes).

Q5. What is the difference between DNA and RNA?

Background

Topic: Nucleic Acids Structure

This question tests your ability to distinguish between the two main types of nucleic acids found in cells.

Key Terms and Concepts:

  • DNA (Deoxyribonucleic Acid): Double-stranded, contains deoxyribose sugar, bases A, T, C, G.

  • RNA (Ribonucleic Acid): Single-stranded, contains ribose sugar, bases A, U, C, G.

  • Base Pairing: DNA uses thymine (T), RNA uses uracil (U).

Step-by-Step Guidance

  1. Recall the sugar component in each nucleic acid (deoxyribose vs ribose).

  2. Identify the nitrogenous bases unique to each (thymine in DNA, uracil in RNA).

  3. Consider the typical structure (double-stranded vs single-stranded).

  4. Think about the main functions of each molecule in the cell.

Try solving on your own before revealing the answer!

Final Answer:

DNA is usually double-stranded, contains deoxyribose sugar, and uses thymine as a base. RNA is usually single-stranded, contains ribose sugar, and uses uracil instead of thymine. DNA stores genetic information, while RNA is involved in protein synthesis and gene regulation.

Q6. What is PCR and what do you need to put in a tube to make PCR function?

Background

Topic: Molecular Biology Techniques

This question is about the polymerase chain reaction (PCR), a method used to amplify DNA, and the essential components required for the reaction.

Key Terms and Concepts:

  • PCR (Polymerase Chain Reaction): Technique to amplify specific DNA sequences.

  • Primers: Short DNA sequences that initiate DNA synthesis.

  • DNA Polymerase: Enzyme that synthesizes new DNA strands (e.g., Taq polymerase).

  • dNTPs: Deoxynucleotide triphosphates (building blocks for DNA synthesis).

  • Template DNA: The DNA sequence to be amplified.

  • Buffer: Maintains optimal conditions for the enzyme.

Step-by-Step Guidance

  1. Recall the main goal of PCR: to amplify a specific DNA segment.

  2. List the essential components: template DNA, primers, DNA polymerase, dNTPs, buffer.

  3. Think about the role of each component in the reaction.

  4. Consider why a thermostable polymerase (like Taq) is used.

Try solving on your own before revealing the answer!

Final Answer:

PCR requires template DNA, two primers (forward and reverse), a thermostable DNA polymerase (such as Taq), dNTPs, and a buffer solution. These components allow for repeated cycles of denaturation, annealing, and extension to amplify the target DNA sequence.

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