BIO 1150 Exam 2 Study Guide – Step-by-Step Guidance

Q1. What components are shared between prokaryotic and eukaryotic cells?

Background

Topic: Cell Structure and Function

This question tests your understanding of the basic similarities and differences between prokaryotic and eukaryotic cells, which is foundational for cell biology.

Key Terms:

• Prokaryotic cells: Cells without a nucleus or membrane-bound organelles (e.g., bacteria).

• Eukaryotic cells: Cells with a nucleus and membrane-bound organelles (e.g., plant and animal cells).

Step-by-Step Guidance

1. Recall the basic structures that all cells must have to survive and function, regardless of type.

2. Think about the essential processes that both prokaryotic and eukaryotic cells must perform (e.g., storing genetic information, synthesizing proteins, maintaining a boundary with the environment).

3. List the cellular components that are present in both cell types, focusing on those involved in these universal processes.

4. Consider which structures are unique to eukaryotes (like the nucleus and organelles) and exclude those from your list.

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Q2. What are the limiting factors on cell size, both on the small and large ends of the spectrum?

Background

Topic: Cell Size and Surface Area-to-Volume Ratio

This question examines your understanding of why cells are limited in how small or large they can be, which relates to their ability to exchange materials with their environment and contain necessary components.

Key Terms:

• Surface area-to-volume ratio: The relationship between the surface area of a cell and its volume, which affects the rate of exchange of materials.

• Diffusion: The movement of molecules from high to low concentration, important for nutrient and waste exchange.

Step-by-Step Guidance

1. Consider what a cell needs to survive: it must house all necessary biomolecules and structures, and it must exchange materials efficiently with its environment.

2. Think about why a cell cannot be too small—what essential components must fit inside?

3. Now, consider why a cell cannot be too large—how does increasing size affect the surface area-to-volume ratio, and why does this matter for transport?

4. Relate your reasoning to the efficiency of diffusion and the ability of the cell to support its metabolic needs.

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Q3. What are the advantages of having organelles within a cell?

Background

Topic: Compartmentalization in Eukaryotic Cells

This question focuses on the benefits of internal membranes and organelles in eukaryotic cells, which allow for specialized functions and increased efficiency.

Key Terms:

• Organelle: A membrane-bound compartment within a eukaryotic cell that performs a specific function.

• Compartmentalization: The separation of different cellular processes into distinct areas within the cell.

Step-by-Step Guidance

1. Recall the main functions of organelles (e.g., energy production, protein synthesis, waste breakdown).

2. Think about how separating these functions into different compartments could benefit the cell.

3. Consider how compartmentalization might affect the efficiency of chemical reactions and the protection of the cell from potentially harmful processes.

4. Reflect on how organelles can help keep incompatible reactions separate and allow for specialized environments within the cell.

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Q4. Describe the flow of material through the endomembrane system. For example, how would a protein that is secreted from the cell move through the different organelles and eventually be released into the extracellular fluid?

Background

Topic: Endomembrane System and Protein Trafficking

This question tests your understanding of how proteins are synthesized, processed, and transported within eukaryotic cells, especially those destined for secretion.

Key Terms:

• Endomembrane system: A group of membranes and organelles in eukaryotic cells that work together to modify, package, and transport lipids and proteins.

• Rough ER, Golgi apparatus, vesicles, plasma membrane: Key components involved in protein secretion.

Step-by-Step Guidance

1. Start with the synthesis of the protein: Where does the information for the protein come from, and where is it first made?

2. Describe how the protein enters the endomembrane system (e.g., entry into the rough ER).

3. Explain the role of the Golgi apparatus in modifying and sorting the protein.

4. Discuss how the protein is packaged and transported to the plasma membrane for secretion.

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Q5. What evidence supports the endosymbiosis theory?

Background

Topic: Origin of Mitochondria and Chloroplasts

This question asks you to recall the main lines of evidence that support the idea that mitochondria and chloroplasts originated from free-living prokaryotes.

Key Terms:

• Endosymbiosis theory: The hypothesis that certain organelles (mitochondria and chloroplasts) originated as free-living bacteria that were engulfed by ancestral eukaryotic cells.

• Circular DNA, ribosomes, independent replication: Features shared with prokaryotes.

Step-by-Step Guidance

1. Recall the structural and genetic similarities between mitochondria/chloroplasts and prokaryotes.

2. Think about the type of DNA found in these organelles and how it compares to nuclear DNA.

3. Consider the characteristics of ribosomes in mitochondria and chloroplasts.

4. Reflect on how these organelles replicate and whether this process is independent of the host cell's cycle.

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Q6. How does an enzyme increase the rate of a reaction?

Background

Topic: Enzyme Function and Catalysis

This question tests your understanding of how enzymes act as biological catalysts to speed up chemical reactions by lowering activation energy.

Key Terms and Formulas:

• Enzyme: A protein that speeds up a chemical reaction without being consumed.

• Activation energy ($E_a$): The energy barrier that must be overcome for a reaction to proceed.

Step-by-Step Guidance

1. Recall what activation energy is and why it matters for chemical reactions.

2. Think about the ways an enzyme can lower the activation energy (e.g., by orienting substrates, straining bonds, providing a favorable environment).

3. Consider the role of the active site in facilitating the reaction.

4. Reflect on how these mechanisms increase the rate of product formation without being consumed in the process.

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Q7. In a cell with a mutated gene for Protein A, the protein moves from the rough ER to the Golgi apparatus, but instead of going to the plasma membrane, it ends up in lysosomes. Why is the cell shuttling the mutated protein to the lysosomes?

Background

Topic: Protein Sorting and Quality Control

This question examines your understanding of how cells recognize and deal with defective or misfolded proteins, particularly through the lysosomal degradation pathway.

Key Terms:

• Lysosome: Organelle responsible for breaking down waste and defective cellular components.

• Protein quality control: Cellular mechanisms that detect and remove misfolded or damaged proteins.

Step-by-Step Guidance

1. Recall the normal pathway for a secreted protein (rough ER → Golgi → plasma membrane).

2. Think about what might cause a protein to be diverted from this pathway.

3. Consider the role of the lysosome in degrading and recycling cellular materials.

4. Reflect on how the cell might recognize a mutated or misfolded protein and target it for destruction.

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Q8. What forces maintain the structure of membranes?

Background

Topic: Membrane Structure and Stability

This question tests your knowledge of the molecular interactions that stabilize biological membranes, including the phospholipid bilayer and associated proteins.

Key Terms:

• Phospholipid bilayer: The fundamental structure of cell membranes, composed of hydrophilic heads and hydrophobic tails.

• Hydrogen bonds, Van der Waals interactions: Types of non-covalent forces that stabilize the membrane.

Step-by-Step Guidance

1. Identify the main components of the membrane (phospholipids, proteins, carbohydrates).

2. Describe how the hydrophilic heads and hydrophobic tails of phospholipids interact with their environment and with each other.

3. Consider the types of non-covalent interactions that stabilize these arrangements (e.g., hydrogen bonds, Van der Waals forces).

4. Think about the role of proteins and the cytoskeleton in maintaining membrane structure.

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Q9. Cholera causes massive fluid loss through diarrhea. The bacterium's toxin leads to large amounts of chloride (Cl-) and sodium (Na+) ions being secreted into the intestinal fluid. Explain why this causes massive fluid loss, using the terms hypertonic or hypotonic.

Background

Topic: Osmosis and Tonicity

This question tests your understanding of how solute concentration differences across membranes drive water movement, and how this relates to disease symptoms.

Key Terms and Concepts:

• Osmosis: The movement of water across a semipermeable membrane from low to high solute concentration.

• Hypertonic: A solution with a higher solute concentration compared to another solution.

• Hypotonic: A solution with a lower solute concentration compared to another solution.

Step-by-Step Guidance

1. Recall what happens to water movement when there is a difference in solute concentration across a membrane.

2. Think about what happens to the tonicity of the intestinal fluid when large amounts of Na+ and Cl- are secreted into it.

3. Determine whether the intestinal fluid becomes hypertonic or hypotonic relative to the cells lining the intestine.

4. Explain how this change in tonicity causes water to move out of the cells and into the intestinal lumen, leading to diarrhea.

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