exam_2_study_guide_

Chapter 7: Prokaryotic and Eukaryotic Cells

Prokaryotic Cells

  • Structure: Lack a nucleus, single cellular structure made of DNA and proteins.

  • Organelles: Rarely contains membrane-bound organelles.

  • Genetics: Contains genes (DNA segments coding for proteins) and plasmids (small circular DNA).

  • Cellular Components:

    • Cytoplasm: All components inside the cell.

    • Ribosomes: Protein manufacturing centers, translating RNA into proteins.

    • Cytoskeleton: Made of protein filaments, maintains cell structure.

    • Cell Membrane/Cell Wall: Protects and supports the cell.

Eukaryotic Cells

  • Structure: Contains a nucleus and is generally larger than prokaryotic cells.

  • Organelles: Compartmentalized cytoplasm with various organelles enhancing efficiency.

  • Key Components:

    • Nucleus Envelope: Double membrane structure with four lipid layers.

    • Nucleolus: Ribosomal RNA synthesis and ribosome assembly.

    • Ribosomes: Free and bound forms for cytosolic and secreted proteins respectively.

    • Rough ER: Involved in protein synthesis.

    • Smooth ER: Involved in synthesis of macronutrients.

    • Lysosomes: Contains enzymes to break down macromolecules; optimized at pH 5.

    • Vacuoles: Storage centers in plants and fungi.

    • Peroxisomes: Involved in detoxification and oxidation/reduction reactions.

    • Mitochondria: ATP production, contains its own DNA and ribosomes.

    • Chloroplasts: Site of photosynthesis, also has its own DNA and ribosomes.

    • Cytoskeleton: Composed of three filaments (microtubules, microfilaments, intermediate filaments).

Comparison: Prokaryotic vs. Eukaryotic Cells

  • Size: Eukaryotic cells are larger and contain a nucleus.

  • Cytoplasm: Organized into membrane-bound organelles in eukaryotic cells.

  • Efficiency: Multiple organelles increase the efficiency of chemical reactions.

Comparison: Plant Cells vs. Animal Cells

  • Plant Cells: Contain cellulose cell walls, chloroplasts, and large vacuoles.

  • Animal Cells: Contain centrioles and lysosomes; lack cell walls and chloroplasts.

Protein Import and Export

Import into the Nucleus

  • Regulated by nuclear pore complex (NPC).

  • Proteins have a nuclear localization sequence (NLS) at the C-terminus.

Export from the Cell

  • Synthesized in ribosomes, enter Rough ER, packaged into vesicles, sorted in Golgi, and secreted via plasma membrane.

Targeting to the ER

  • ER signal sequence synthesized at N-terminus, binds to signal recognition particle (SRP) that directs it to receptors on the ER.

Sorting in the Golgi Apparatus

  • Proteins have destination tags, transported by vesicle budding and membrane fusion.

Cell Junctions (Chapter 11)

  • Tight Junctions: Water-tight seals between cells.

  • Desmosomes: Strong adhesions anchoring the cytoskeleton for structural support.

  • Gap Junctions: Protein channels allowing communication between adjacent cells, facilitating ion and small molecule passage.

  • Plasmodesmata: Gaps in plant cell walls for communication without proteins.

Cell-Cell Signaling

Steps in Signal Transduction

  1. Signal Reception: Binding of a signal molecule changes a receptor's activity.

  2. Signal Transduction: Uses second messengers (e.g., cAMP) for intracellular signal transmission.

  3. Signal Response: Triggers cellular actions like growth or metabolism changes.

  4. Signal Deactivation: Rapid responses to deactivate signals; methods vary by type.

Types of Molecules in Cell Signaling

Lipid-Soluble Molecules

  • Diffuse through the cell membrane, bind to cytosolic receptors, and affect transcription in the nucleus.

Lipid-Insoluble Molecules

  • Bind to transmembrane receptors resulting in a signaling pathway without crossing the membrane.

Chemical Reactions and Energetics (Chapter 8)

Reaction Favorability

  • Negative delta H: Products have less potential energy than reactants.

  • Positive delta H: Products possess more potential energy.

Spontaneity of Reactions

  • A reaction is spontaneous if delta H is negative and delta S is positive.

Factors Influencing Reaction Rates

  • Affecting factors: Temperature and concentration.

Oxidation and Reduction

Definitions

  • Oxidation: Loss of electrons.

  • Reduction: Gain of electrons.

  • Oxidizing Agent: Substance that causes oxidation, typically oxygen unless a stronger agent (like fluorine) is present.

Enzyme-Catalyzed Reactions

  1. Initiation: Substrates bind to enzyme.

  2. Lowering Activation Energy: Enzymes stabilize transition states to lower energy barriers.

  3. Release: Products released, enzyme returns to original form.

Cellular Respiration Inputs and Outputs (Chapter 9)

  • Glycolysis: Inputs - glucose, outputs - 2 ATP, 2 NADH.

  • Pyruvate Oxidation: Connects glycolysis to citric acid cycle.

  • Citric Acid Cycle: Outputs include ATP, NADH, FADH2.

  • Oxidative Phosphorylation: Major ATP production occurring in mitochondria.

  • Fermentation: ATP production in absence of oxygen, regenerates NAD+.

Photosynthesis Inputs and Outputs

  • Light Reactions: Inputs - water and light; Outputs - oxygen, ATP, NADPH.

  • Calvin Cycle: Utilizes ATP and NADPH from light reactions to synthesize glucose.

Comparison of Photosystems

  • Photosystem II: Occurs first; oxidizes water.

  • Photosystem I: Received electrons from ETC to reduce NADP+ into NADPH.

Electron Flow in Photosynthesis

  • Noncyclic Flow: Involves both photosystems, producing ATP and NADPH.

  • Cyclic Flow: Generates additional ATP when NADPH production is not sufficient.

Rubisco and Photorespiration

  • Rubisco converts CO2 into sugars; also erroneously binds O2, leading to inefficiency in plants.

C3, C4, and CAM Plants

  • C3 Plants: Normal Calvin cycle.

  • C4 Plants: CO2 fixed into 4C compounds, improving efficiency.

  • CAM Plants: Fix CO2 at night and perform the Calvin cycle during the day.