Unit 2 Test PREP

1. What are the three postulates of the cell theory?

   • All living organisms are composed of one or more cells.

   • The cell is the basic unit of life.

   • All cells arise from pre-existing cells.

Surface Area-to-Volume Relationship

2. How does the surface-area-to-volume relationship affect cell size?

   • As a cell grows, its volume increases faster than its surface area, which limits the cell’s ability to efficiently exchange materials with its environment. This constraint keeps cells small.

Types of Microscopes

3. What is a compound microscope, and what are its benefits and trade-offs?

   • A light microscope that uses multiple lenses to magnify objects.

   • Benefits: Easy to use, allows viewing of live specimens.

   • Trade-offs: Limited magnification and resolution.

4. What is a transmission electron microscope (TEM), and what are its benefits and trade-offs?

   • Uses electrons to pass through a specimen, producing high-resolution images of internal structures.

   • Benefits: High magnification and resolution.

   • Trade-offs: Specimens must be dead and prepared in thin slices.

5. What is a scanning electron microscope (SEM), and what are its benefits and trade-offs?

   • Uses electrons to scan the surface of a specimen, creating a 3D image.

   • Benefits: High-resolution surface details.

   • Trade-offs: Specimens must be dead, expensive equipment.

6. What is a confocal microscope, and what are its benefits and trade-offs?

   • Uses lasers and fluorescent dyes to produce high-resolution images of thick specimens.

   • Benefits: Allows 3D reconstruction of cells and tissues.

   • Trade-offs: Expensive, requires fluorescent staining.

Microscopy Concepts

7. What is the difference between magnification, resolution, and contrast in microscopy?

   • Magnification: Increases the apparent size of an object.

   • Resolution: The ability to distinguish between two close objects.

   • Contrast: The ability to differentiate structures based on color or intensity differences.

Prokaryotic vs. Eukaryotic Cells

8. How do prokaryotic and eukaryotic cells differ in structure?

   • Prokaryotic cells: No nucleus, no membrane-bound organelles, smaller size.

   • Eukaryotic cells: Contain a nucleus, membrane-bound organelles, larger size.

Prokaryotic Cell Envelope

9. What are the components of the prokaryotic cell envelope, and what are their functions?

   • Plasma membrane: Regulates material transport.

   • Cell wall: Provides structure and protection.

   • Glycocalyx (capsule or slime layer): Protects against desiccation and immune response.

Prokaryotic Cell Shapes

10. What are the differences in shape between coccus, bacillus, spirillum, and spirochete prokaryotes?

• Coccus: Spherical shape.

• Bacillus: Rod-shaped.

• Spirillum: Rigid spiral shape.

• Spirochete: Flexible, corkscrew shape.

Prokaryotic Cell Components

11. What are the intracellular components of a prokaryotic cell, and what are their functions?

• Nucleoid: Contains genetic material (DNA).

• Ribosomes: Synthesize proteins.

• Plasmids: Small DNA molecules that provide additional traits (e.g., antibiotic resistance).

• Cytoplasm: Fluid inside the cell where biochemical reactions occur.

Endosymbiotic Theory

12. What is the Endosymbiotic Theory of Cellular Evolution?

• It proposes that mitochondria and chloroplasts originated as free-living prokaryotic cells that were engulfed by an ancestral eukaryotic cell, leading to a symbiotic relationship.

Cell Structures & Organelles

13. What is the function of the plasma (cell) membrane?

• Regulates the movement of substances into and out of the cell.

14. What is the function of the cell wall?

• Provides structural support and protection (found in plants, fungi, and prokaryotes).

15. What is the function of the nucleus?

• Stores genetic information (DNA) and controls cellular activities.

16. What is the function of the nuclear envelope?

• Separates the nucleus from the cytoplasm and regulates nuclear transport.

17. What is the function of the nucleolus?

• Produces ribosomal RNA (rRNA) and assembles ribosomes.

18. What is the function of the rough endoplasmic reticulum?

• Synthesizes and processes proteins.

19. What is the function of the smooth endoplasmic reticulum?

• Synthesizes lipids and detoxifies toxins.

20. What is the function of ribosomes?

• Synthesize proteins.

21. What is the function of mitochondria?

• Produce ATP (cellular energy) through aerobic respiration.

22. What is the function of chloroplasts?

• Carry out photosynthesis in plant cells.

23. What is the function of vacuoles?

• Store nutrients, waste, and other materials (large central vacuole in plant cells).

24. What is the function of the Golgi apparatus?

• Modifies, sorts, and packages proteins and lipids for transport.

25. What is the function of lysosomes?

• Break down waste, cellular debris, and foreign substances.

26. What is the function of flagella?

• Provide cell movement.

27. What is the function of cilia?

• Move substances along the cell surface or assist in movement.

28. What is the function of centrioles?

• Help organize cell division in animal cells.

29. What is the function of microtubules?

• Provide structural support and assist in intracellular transport.

30. What is the function of actin filaments?

• Involved in cell shape, movement, and division.

31. What is the function of intermediate filaments?

• Provide mechanical support to the cell.

32. What is the function of chromosomes?

• Carry genetic information in the form of DNA.

33. What is the function of chromatin?

• A complex of DNA and proteins that condenses to form chromosomes.

34. What is the function of peroxisomes?

• Break down fatty acids and detoxify harmful substances.

Molecular Biology & Cell Transport

35. What is the central dogma of molecular biology?

• DNA → RNA → Protein; genetic information flows from DNA to RNA (transcription) and then from RNA to protein (translation).

36. Why are some organelles membrane-bound?

• Membrane-bound organelles create compartments that allow for specialized functions and increased efficiency within the cell.

37. How do substances travel through vesicles between organelles and out of a cell?

• Vesicles transport materials by budding off from one organelle and fusing with another, facilitating intracellular transport and secretion.

  Plasma (Cell) Membrane Structure & Function

  1. What is the structure of the eukaryotic cell’s plasma (cell) membrane, and what are the functions of its major components?

     • Phospholipid bilayer: Forms a semi-permeable barrier.

     • Proteins: Assist in transport, signaling, and structural support.

     • Cholesterol: Maintains membrane fluidity and stability.

     • Carbohydrates: Involved in cell recognition and signaling.

  2. Why is the cell membrane described as a fluid mosaic?

     • The membrane is "fluid" because lipids and proteins can move laterally within the bilayer, and it is a "mosaic" due to the diverse embedded proteins and molecules.

  3. Why is the cell membrane described as semi-permeable/selectively permeable?

     • It allows some substances (like small, nonpolar molecules) to pass freely while restricting others based on size, charge, and polarity.

  4. How can you predict the permeability of a substance across the cell membrane?

     • Highly permeable: Small, nonpolar molecules (O₂, CO₂).

     • Moderately permeable: Small, polar molecules (H₂O, ethanol).

     • Low permeability: Large, polar molecules (glucose).

     • Very low permeability: Ions (Na⁺, K⁺, Cl⁻).

  Membrane Proteins & Their Functions

  5. What are the major types of membrane proteins, and how do they affect permeability?

     • Channel proteins: Provide a passage for specific molecules (e.g., ion channels).

     • Carrier proteins: Bind and transport molecules across the membrane.

     • Receptor proteins: Detect and respond to signals.

     • Enzymatic proteins: Catalyze reactions at the membrane.

     • Adhesion proteins: Help cells stick together.

  Signal Transduction Pathways & Cell Communication

  6. What is the general structure of a signal transduction pathway, and how does it aid in cell-cell communication?

     • Reception: A ligand (signal molecule) binds to a receptor.

     • Transduction: A series of molecular interactions relay the signal inside the cell.

     • Response: The cell produces a specific action (e.g., gene expression, enzyme activation).

  Membrane Transport Mechanisms

  7. How do passive and active transport differ?

     • Passive transport: Does not require energy, moves substances down their concentration gradient.

     • Active transport: Requires energy (ATP), moves substances against their concentration gradient.

  8. What are different types of passive and active transport, and what substances use each method?

     • Passive transport:

       • Simple diffusion: Small, nonpolar molecules (O₂, CO₂).

       • Facilitated diffusion: Large or charged molecules (glucose, ions) via carrier or channel proteins.

       • Osmosis: Water movement through aquaporins.

     • Active transport:

       • Primary active transport: Uses ATP directly (e.g., sodium-potassium pump).

       • Secondary active transport: Uses ion gradients to drive transport (e.g., glucose transport in intestines).

       • Endocytosis: Engulfing large molecules into the cell.

       • Exocytosis: Expelling large molecules from the cell.

  9. How does the sodium-potassium pump work?

     • Pumps 3 Na⁺ out and 2 K⁺ in, using ATP, maintaining the electrochemical gradient essential for nerve impulses and muscle contraction.

  10. How does water move across cell membranes?

  • Water moves by osmosis, from areas of low solute concentration to high solute concentration, either directly through the membrane or via aquaporins.

  Tonicity & Its Effects on Cells

  11. What do hypertonic, hypotonic, and isotonic mean, and how do they relate to lysis and turgor pressure?

  • Hypertonic: Higher solute concentration outside → Water leaves cell → Shrinking (crenation in animal cells, plasmolysis in plant cells).

  • Hypotonic: Lower solute concentration outside → Water enters cell → Swelling and lysis in animal cells, turgor pressure in plant cells.

  • Isotonic: Equal solute concentration → No net water movement → Cell remains stable.

  12. How can you predict the outcome of an experiment based on the tonicity of a solution?

  • If a cell is placed in a hypertonic solution, it will shrink.

  • If a cell is placed in a hypotonic solution, it will swell or burst.

  • If a cell is placed in an isotonic solution, there will be no significant change.

  Active Transport & Endocytosis

  13. How can you predict the active transport mechanism of a substance?

  • If the substance moves against its concentration gradient, ATP or ion gradients are needed.

  • Large molecules use endocytosis or exocytosis.

  14. How do neurotransmitters and drugs utilize receptor-mediated endocytosis?

  • They bind to specific receptors, triggering vesicle formation and internalization of the substance (e.g., uptake of cholesterol via LDL receptors).

  Extracellular Matrix & Cell Junctions

  15. What are the major molecules involved in the extracellular matrix?

  • Collagen: Provides strength.

  • Elastin: Provides flexibility.

  • Proteoglycans: Help with hydration and cushioning.

  • Fibronectin & Integrins: Facilitate cell adhesion and communication.

  16. What are the three major types of cell junctions in animal cells and the main type in plant cells?

  • Tight junctions: Prevent leakage between cells (e.g., in intestines).

  • Desmosomes: Provide strong adhesion between cells (e.g., in skin).

  • Gap junctions: Allow communication between cells (e.g., in cardiac muscle).

  • Plasmodesmata (plants only): Connect plant cells, allowing cytoplasm exchange.

Energy & Thermodynamics

1. What is energy, and how do kinetic and potential energy differ?

   • Energy: The ability to do work.

   • Kinetic energy: Energy of motion (e.g., heat, light, movement).

   • Potential energy: Stored energy (e.g., chemical bonds, gravitational energy).

2. How do kinetic and potential energy relate to energy flow in the universe?

   • The universe moves toward entropy (disorder), transforming potential energy (stored in bonds) into kinetic energy (motion, heat, light).

3. How do kinetic and potential energy apply to molecular bonds?

   • Chemical bonds store potential energy, and when broken, release kinetic energy in the form of heat or motion.

4. What are the First and Second Laws of Thermodynamics?

   • First Law: Energy cannot be created or destroyed, only transformed.

   • Second Law: Energy transfer increases entropy (disorder) of the universe.

5. How do the First and Second Laws of Thermodynamics apply to cell chemistry and metabolism?

   • First Law: Cells convert chemical energy (glucose) into ATP.

   • Second Law: Some energy is lost as heat, increasing disorder.

Chemical Reactions & Free Energy

6. How do you read a chemical formula?

   • Identifies elements (symbols) and number of atoms in a molecule (subscripts).

   • Example: C₆H₁₂O₆ (glucose) has 6 carbon, 12 hydrogen, and 6 oxygen atoms.

7. What is free energy (G), and how does it relate to spontaneous reactions?

   • Free energy (G): Energy available to do work.

   • Spontaneous reactions: Occur when ∆G is negative, meaning energy is released.

8. How do exergonic and endergonic reactions differ, and how do they relate to free energy (∆G)?

   • Exergonic reactions: Release energy (∆G < 0, spontaneous). Example: Cellular respiration.

   • Endergonic reactions: Require energy input (∆G > 0, non-spontaneous). Example: Photosynthesis.

9. How do the potential energies of ATP, ADP, and AMP compare?

   • ATP (adenosine triphosphate): Highest energy, 3 phosphate groups.

   • ADP (adenosine diphosphate): Medium energy, 2 phosphate groups.

   • AMP (adenosine monophosphate): Lowest energy, 1 phosphate group.

10. What is the ATP-ADP cycle?

• ATP → ADP + Pi (energy released for cellular work).

• ADP + Pi → ATP (energy stored from food breakdown).

11. What are coupled reactions, and how do they involve endergonic and exergonic reactions?

• Coupled reactions: Pair an exergonic reaction (energy-releasing) with an endergonic reaction (energy-requiring) to drive biological processes.

• Example: ATP hydrolysis (exergonic) powers muscle contraction (endergonic).

Metabolism & Enzymes

12. What is a metabolic pathway, and how do enzymes regulate it?

• Metabolic pathways: Series of enzyme-controlled chemical reactions.

• Enzymes speed up reactions by lowering activation energy.

13. What is an enzyme, and what is the active site?

• Enzyme: A biological catalyst that speeds up reactions.

• Active site: The specific region where the substrate binds.

14. What is the induced fit model of substrate binding?

• Enzyme changes shape slightly to better fit the substrate, increasing efficiency.

15. How does an enzyme’s active site determine its substrate specificity?

• Shape & charge of the active site allow only specific substrates to bind.

16. What is activation energy, and how do enzymes lower it?

• Activation energy: The energy required to start a reaction.

• Enzymes lower activation energy by stabilizing the transition state.

17. What are the components of a chemical reaction?

• Substrate: The reactant(s) an enzyme acts on.

• Enzyme: Catalyst that speeds up reaction.

• Product: The resulting molecule(s).

Factors Affecting Enzymes & Inhibition

18. How do environmental factors affect enzyme function?

• Temperature: Too high → denaturation; too low → slowed reactions.

• pH: Extreme pH can denature enzymes.

• Substrate concentration: More substrate increases activity until saturation.

• Enzyme concentration: More enzyme increases reaction rate (if substrate is available).

• Cofactors/coenzymes: Help enzymes function properly.

19. How do inhibitors affect enzyme activity?

• Competitive inhibitors: Bind to the active site, blocking the substrate.

• Noncompetitive inhibitors: Bind elsewhere, altering the enzyme’s shape.

20. What are the differences between competitive vs. noncompetitive, and reversible vs. irreversible inhibitors?

• Competitive inhibitors: Compete for active site, can be overcome by more substrate.

• Noncompetitive inhibitors: Bind to a different site, changing enzyme shape.

• Reversible inhibitors: Temporarily inhibit enzyme function.

• Irreversible inhibitors: Permanently disable enzymes (e.g., toxins).

Redox Reactions & Energy Transfer

21. What are oxidation and reduction, and how do they work together in redox reactions?

• Oxidation: Loss of electrons (LEO = Lose Electrons Oxidation).

• Reduction: Gain of electrons (GER = Gain Electrons Reduction).

• Redox reactions: One molecule is oxidized while another is reduced.

22. What are the basic chemical formulas for photosynthesis and cellular respiration?

• Photosynthesis:
  6CO2+6H2O+light→C6H12O6+6O26CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂6CO2​+6H2​O+light→C6​H12​O6​+6O2​

• Cellular respiration:
  C6H12O6+6O2→6CO2+6H2O+ATPC₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATPC6​H12​O6​+6O2​→6CO2​+6H2​O+ATP

23. How is energy transferred in photosynthesis and cellular respiration?

• Photosynthesis: Converts light energy into chemical energy (glucose).

• Cellular respiration: Converts glucose energy into ATP for cellular work.