뒤로General Biology Study Guide: Cell Structure, Metabolism, and Cellular Respiration
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Q1. What are the components of the modern cell theory?
Background
Topic: Cell Theory
This question tests your understanding of the foundational principles that define what a cell is and how cells relate to living organisms.
Key Terms:
Cell theory
Organism
Basic unit of life
Step-by-Step Guidance
Recall the three main tenets of the modern cell theory. Think about what the theory says about the structure and function of cells in all living things.
Consider how the cell theory has been updated with modern discoveries (e.g., hereditary information, energy flow).
Write out each component in your own words, making sure to address both the structural and functional aspects.
Try solving on your own before revealing the answer!
Final Answer:
All living things are composed of one or more cells.
The cell is the basic unit of structure and function in living organisms.
All cells arise from pre-existing cells.
Modern additions: Cells contain hereditary information (DNA) that is passed from cell to cell during division, and all energy flow (metabolism and biochemistry) occurs within cells.
These principles form the foundation for understanding biology at the cellular level.
Q2. Describe in detail the major differences between prokaryotic and eukaryotic cells.
Background
Topic: Cell Types
This question is about distinguishing the two main categories of cells based on their structural and functional characteristics.
Key Terms:
Prokaryote
Eukaryote
Organelle
Nucleus
Step-by-Step Guidance
List the defining features of prokaryotic cells (think about nucleus, organelles, size, and complexity).
List the defining features of eukaryotic cells (focus on nucleus, organelles, and examples of organisms).
Compare and contrast the two types, noting at least three major differences.
Consider examples of each type (e.g., bacteria vs. plant/animal cells).
Try solving on your own before revealing the answer!
Final Answer:
Prokaryotic cells lack a true nucleus and membrane-bound organelles; their DNA is found in a nucleoid region. Examples: Bacteria and Archaea.
Eukaryotic cells have a true nucleus surrounded by a nuclear envelope and contain membrane-bound organelles (e.g., mitochondria, ER, Golgi). Examples: Plants, animals, fungi, and protists.
Eukaryotic cells are generally larger and more complex than prokaryotic cells.
These differences are fundamental to understanding cell structure and function.
Q3. Describe the structure and function of the following organelles: cytoplasm, mitochondria, nucleus, smooth ER, rough ER, Golgi apparatus, endomembrane system, ribosomes, vacuoles, lysosomes, phagosomes, chloroplasts, cytoskeleton, and cell-to-cell junctions.
Background
Topic: Cell Organelles and Their Functions
This question asks you to identify and describe the structure and function of key organelles found in eukaryotic cells, and how they interact.
Key Terms:
Organelle
Membrane-bound
Cell compartmentalization
Step-by-Step Guidance
For each organelle, write a brief description of its structure (e.g., membrane-bound, shape, location).
Describe the main function(s) of each organelle (e.g., energy production, protein synthesis, storage).
Note any relationships or interactions between organelles (e.g., how the ER and Golgi work together).
For plant-specific organelles (e.g., chloroplasts), highlight their unique roles.
Try solving on your own before revealing the answer!
Final Answer:
Cytoplasm: Gel-like fluid inside the cell where organelles are suspended; site of many metabolic reactions.
Mitochondria: Double-membraned organelle; site of cellular respiration and ATP production.
Nucleus: Contains genetic material (DNA); controls cell activities.
Smooth ER: Lacks ribosomes; synthesizes lipids and detoxifies substances.
Rough ER: Studded with ribosomes; synthesizes and processes proteins.
Golgi apparatus: Modifies, sorts, and packages proteins and lipids for transport.
Endomembrane system: Includes ER, Golgi, lysosomes, and vesicles; coordinates synthesis and transport of cellular products.
Ribosomes: Sites of protein synthesis; can be free or attached to ER.
Vacuoles: Storage organelles; large central vacuole in plants stores water and nutrients.
Lysosomes: Contain digestive enzymes; break down waste and cellular debris.
Phagosomes: Vesicles formed around particles engulfed by phagocytosis; fuse with lysosomes for digestion.
Chloroplasts: Found in plants; site of photosynthesis; contain chlorophyll.
Cytoskeleton: Network of protein fibers; provides structural support, cell shape, and movement.
Cell-to-cell junctions: Structures that connect cells (e.g., tight junctions, gap junctions, plasmodesmata).
Understanding these organelles is key to grasping cell function and organization.
Q4. Can you describe the concept of Gibbs' Free Energy? How is it expressed?
Background
Topic: Bioenergetics
This question is about understanding how energy changes are measured in biological systems and how they predict the direction of chemical reactions.
Key Terms and Formula:
Gibbs Free Energy ()
Enthalpy ()
Entropy ()
Temperature ()
Key formula:
Step-by-Step Guidance
Define Gibbs Free Energy and explain what it measures in a biological context.
Identify the variables in the formula and what each represents (enthalpy, entropy, temperature).
Explain how changes in predict whether a reaction is spontaneous or requires energy input.
Try solving on your own before revealing the answer!
Final Answer:
Gibbs Free Energy () is a measure of the usable energy in a system that can do work at constant temperature and pressure. It is expressed as:
Where is the change in enthalpy (total energy), is the absolute temperature in Kelvin, and is the change in entropy (disorder). A negative indicates a spontaneous (exergonic) reaction, while a positive $\Delta G$ indicates a non-spontaneous (endergonic) reaction.
Q5. What are endergonic and exergonic reactions? Do they affect the free energy of a cell or system?
Background
Topic: Chemical Reactions and Energy
This question is about understanding how energy is absorbed or released during chemical reactions and how this relates to changes in free energy.
Key Terms:
Endergonic (energy-absorbing)
Exergonic (energy-releasing)
Free energy ()
Step-by-Step Guidance
Define endergonic and exergonic reactions in terms of energy flow.
Relate these definitions to changes in Gibbs Free Energy ().
Explain how these reactions impact the free energy of a cell or system.
Try solving on your own before revealing the answer!
Final Answer:
Exergonic reactions release energy and have a negative , decreasing the free energy of the system. Endergonic reactions absorb energy and have a positive $\Delta G$, increasing the system's free energy. These changes in free energy determine whether a reaction can occur spontaneously.
Q6. How do catabolism and anabolism differ? What is the difference between catabolic/exergonic and anabolic/endergonic?
Background
Topic: Metabolic Pathways
This question is about distinguishing the two main types of metabolic processes and how they relate to energy changes in the cell.
Key Terms:
Catabolism
Anabolism
Exergonic
Endergonic
Step-by-Step Guidance
Define catabolism and anabolism in terms of the types of reactions and their purposes in the cell.
Explain how catabolic reactions are generally exergonic and anabolic reactions are generally endergonic.
Provide examples of each type of reaction (e.g., cellular respiration vs. protein synthesis).
Try solving on your own before revealing the answer!
Final Answer:
Catabolism involves breaking down molecules and releasing energy (exergonic), such as in cellular respiration. Anabolism involves building complex molecules and requires energy input (endergonic), such as in protein synthesis. Catabolic = exergonic; anabolic = endergonic.
Q7. What is ATP and why is it important? How does ATP transfer energy to other substances or reactions?
Background
Topic: ATP and Energy Transfer
This question is about the structure and function of ATP as the main energy currency of the cell and how it powers cellular processes.
Key Terms:
ATP (adenosine triphosphate)
Phosphorylation
Hydrolysis
Step-by-Step Guidance
Describe the structure of ATP and why it stores energy.
Explain how ATP is used to transfer energy to other molecules (phosphorylation).
Discuss the role of ATP hydrolysis in driving endergonic reactions.
Try solving on your own before revealing the answer!
Final Answer:
ATP is a nucleotide with three phosphate groups; it stores energy in the bonds between these phosphates. When ATP is hydrolyzed (loses a phosphate), it releases energy that can be used by the cell. ATP transfers energy by phosphorylating other molecules, making them more reactive.
Q8. What is a coenzyme and what is its role in metabolism?
Background
Topic: Enzyme Function and Metabolism
This question is about understanding the role of coenzymes in facilitating metabolic reactions, often by carrying electrons or functional groups.
Key Terms:
Coenzyme
Enzyme
Metabolism
Step-by-Step Guidance
Define what a coenzyme is and how it differs from an enzyme.
Explain the role of coenzymes in metabolic reactions (e.g., electron carriers).
Give examples of common coenzymes (e.g., NAD+, FAD).
Try solving on your own before revealing the answer!
Final Answer:
Coenzymes are organic molecules that assist enzymes in catalyzing reactions, often by carrying electrons, atoms, or functional groups. Examples include NAD+ and FAD, which are essential for cellular respiration and other metabolic pathways.
Q9. What are reduction and oxidation, and how are they coupled in biological systems?
Background
Topic: Redox Reactions in Biology
This question is about understanding how electrons are transferred in metabolic reactions and why these processes are always linked.
Key Terms:
Oxidation
Reduction
Redox reaction
Step-by-Step Guidance
Define oxidation and reduction in terms of electron transfer.
Explain why these processes always occur together (one molecule loses electrons, another gains them).
Provide an example from cellular respiration (e.g., NAD+ to NADH).
Try solving on your own before revealing the answer!
Final Answer:
Oxidation is the loss of electrons, while reduction is the gain of electrons. In biological systems, these reactions are coupled (redox reactions) because electrons lost by one molecule are gained by another. For example, in cellular respiration, NAD+ is reduced to NADH as it gains electrons.
Q10. What class of biological molecules are enzymes? How do enzymes and substrates interact?
Background
Topic: Enzyme Structure and Function
This question is about the molecular nature of enzymes and how they catalyze reactions by interacting with substrates.
Key Terms:
Enzyme
Protein
Substrate
Active site
Step-by-Step Guidance
Identify the class of macromolecules to which most enzymes belong.
Describe how enzymes bind to substrates at the active site.
Explain the specificity of enzyme-substrate interactions (lock-and-key or induced fit models).
Try solving on your own before revealing the answer!
Final Answer:
Most enzymes are proteins. They interact with substrates by binding them at their active site, forming an enzyme-substrate complex. This interaction is highly specific, often described by the lock-and-key or induced fit models.
Q11. How do enzymes increase the rate of chemical reactions? What is activation energy, and how do enzymes lower it?
Background
Topic: Enzyme Catalysis
This question is about the mechanism by which enzymes speed up reactions and the concept of activation energy.
Key Terms:
Activation energy ()
Catalyst
Transition state
Step-by-Step Guidance
Define activation energy and its role in chemical reactions.
Explain how enzymes act as catalysts to lower the activation energy.
Describe how this increases the rate of reaction without being consumed.
Try solving on your own before revealing the answer!
Final Answer:
Activation energy is the energy required to start a reaction. Enzymes lower the activation energy by stabilizing the transition state, making it easier for reactants to convert to products. This increases the reaction rate without the enzyme being used up.
Q12. How is enzyme activity regulated? What is feedback inhibition, and what are the two mechanisms discussed in class?
Background
Topic: Enzyme Regulation
This question is about the ways cells control enzyme activity to maintain homeostasis, including feedback inhibition mechanisms.
Key Terms:
Feedback inhibition
Allosteric regulation
Competitive inhibition
Step-by-Step Guidance
Define feedback inhibition and why it is important for metabolic pathways.
Describe the two main mechanisms: allosteric (noncompetitive) and competitive inhibition.
Explain how each mechanism affects enzyme activity.
Try solving on your own before revealing the answer!
Final Answer:
Feedback inhibition is when the end product of a pathway inhibits an earlier enzyme, preventing overproduction. The two mechanisms are competitive inhibition (inhibitor binds active site) and allosteric (noncompetitive) inhibition (inhibitor binds elsewhere, changing enzyme shape). Both regulate enzyme activity but in different ways.
Q13. What is the purpose of cellular respiration? How does the 'crude oil vs. gasoline' analogy apply?
Background
Topic: Cellular Respiration
This question is about understanding why cells perform respiration and how energy is transformed into a usable form (ATP).
Key Terms:
Cellular respiration
ATP
Energy conversion
Step-by-Step Guidance
State the main purpose of cellular respiration in cells.
Explain the analogy: crude oil (glucose) vs. gasoline (ATP).
Describe how glucose is converted into ATP through respiration.
Try solving on your own before revealing the answer!
Final Answer:
The purpose of cellular respiration is to convert the chemical energy in glucose into ATP, which cells can use directly. The analogy compares glucose to crude oil (energy-rich but not directly usable) and ATP to gasoline (refined, usable energy for cellular work).
Q14. What are the three major pathways of aerobic respiration? What is the goal and net gain of each part?
Background
Topic: Aerobic Respiration Pathways
This question is about identifying the stages of aerobic respiration and understanding their individual contributions to ATP and electron carrier production.
Key Terms:
Glycolysis
Krebs cycle (Citric Acid Cycle)
Electron Transport System (ETS)
ATP, NADH, FADH2
Step-by-Step Guidance
Name the three main stages of aerobic respiration.
For each stage, state its main goal (e.g., breakdown of glucose, production of electron carriers, ATP synthesis).
List the net gain of ATP and electron carriers (NADH, FADH2) for each stage.
Try solving on your own before revealing the answer!
Final Answer:
Glycolysis: Breaks down glucose into pyruvate; net gain: 2 ATP, 2 NADH.
Krebs Cycle: Processes pyruvate to CO2; net gain: 2 ATP, 6 NADH, 2 FADH2 (per glucose).
Electron Transport System (ETS): Uses NADH/FADH2 to produce ATP via chemiosmosis; net gain: about 28 ATP.
Total ATP yield per glucose is about 32 ATP in eukaryotes.
Q15. What happens to the six original carbons in glucose during aerobic and anaerobic respiration?
Background
Topic: Fate of Glucose Carbons
This question is about tracking the carbon atoms from glucose as they are processed during respiration.
Key Terms:
Glucose
CO2
Aerobic vs. anaerobic respiration
Step-by-Step Guidance
Recall the chemical formula for glucose ().
Describe how glucose is broken down during glycolysis and the Krebs cycle.
Explain what happens to the carbon atoms in aerobic respiration (conversion to CO2).
Contrast with what happens in anaerobic respiration (e.g., fermentation products).
Try solving on your own before revealing the answer!
Final Answer:
In aerobic respiration, all six carbons from glucose are released as CO2. In anaerobic respiration (fermentation), some carbons remain in end products like lactate or ethanol, so not all are released as CO2.
Q16. How do the Electron Transport System (ETS) and chemiosmosis work to produce ATP in mitochondria?
Background
Topic: Oxidative Phosphorylation
This question is about the final stage of aerobic respiration, where most ATP is produced via the ETS and chemiosmosis.
Key Terms:
Electron Transport Chain (ETC/ETS)
Chemiosmosis
ATP synthase
Proton gradient
Step-by-Step Guidance
Describe how electrons from NADH and FADH2 are transferred through the ETS.
Explain how this transfer pumps protons (H+) across the inner mitochondrial membrane, creating a gradient.
Discuss how the flow of protons back through ATP synthase drives ATP production (chemiosmosis).
Try solving on your own before revealing the answer!
Final Answer:
Electrons from NADH/FADH2 pass through the ETS, powering proton pumps that create a proton gradient. Protons flow back through ATP synthase, which uses this energy to synthesize ATP from ADP and Pi. This process is called chemiosmosis.
Q17. What is the role of oxygen in aerobic cellular respiration?
Background
Topic: Final Electron Acceptor
This question is about why oxygen is essential for aerobic respiration and what happens in its absence.
Key Terms:
Oxygen
Electron acceptor
Water formation
Step-by-Step Guidance
Explain what happens to electrons at the end of the ETS.
Describe the role of oxygen as the final electron acceptor.
Discuss what is formed when oxygen accepts electrons and protons.
Try solving on your own before revealing the answer!
Final Answer:
Oxygen acts as the final electron acceptor in the ETS, combining with electrons and protons to form water. Without oxygen, the ETS cannot function, and ATP production stops.
Q18. Be able to discuss ATP output from the entire respiratory system.
Background
Topic: ATP Yield in Cellular Respiration
This question is about calculating the total ATP produced from one molecule of glucose during aerobic respiration.
Key Terms:
ATP yield
Glycolysis
Krebs cycle
Electron Transport System
Step-by-Step Guidance
List the ATP produced at each stage: glycolysis, Krebs cycle, and ETS.
Add up the net ATP from substrate-level phosphorylation and oxidative phosphorylation.
Consider the efficiency and possible variations in ATP yield (e.g., shuttle systems, cell type).
Try solving on your own before revealing the answer!
Final Answer:
From one glucose molecule, about 2 ATP are produced in glycolysis, 2 ATP in the Krebs cycle, and about 28 ATP from the ETS, totaling approximately 32 ATP in eukaryotic cells. Actual yield may vary depending on cell conditions.
