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Comprehensive Study Guide on Eukaryotic Cells, Transport Mechanisms, and Energy

Introduction

  • Discussion on unit topics (organelles, membrane transport, energy)

  • Concept map available for practice on unit exam.

Eukaryotic Cells

Organelle Overview

  • Starting point: Understanding organelles in eukaryotic cells.

  • Structure/function relationship emphasis.

  • Introduction of eukaryotic cell components and related functions.

Beginning with Structures

Cell Membrane

  • Definition: Plasma membrane surrounds all eukaryotic cells.

  • Function: Divides internal environment from external environment.

  • Additional layer in plant cells: Cell wall for structural support.

Nucleus

  • Storage of chromatin (DNA wrapped with proteins).

  • Function: Stores genetic material (nucleic acids).

  • Nuclear envelope: Protects nucleus, resembles plasma membrane; consists of double phospholipid bilayer.

  • Nuclear pores: Allow passage of materials (e.g., messenger RNA).

Nucleolus

  • Function: Synthesizes ribosomal RNA (rRNA).

Ribosomes and Protein Synthesis

  • Messenger RNA (mRNA) exits nucleus through nuclear pores into cytosol.

  • Endoplasmic Reticulum (ER): Site for protein synthesis.

    • Rough ER: Has ribosomes; synthesizes proteins for membrane integration or export.

    • Smooth ER: Lacks ribosomes; involved in lipid synthesis, calcium storage, and detoxification.

Transport Mechanisms

  • Vesicles: Membrane-enclosed compartments that bud off from the ER.

  • Motor proteins: Facilitate transport along microtubules.

    • Types: Kinesin (toward membrane), Dynein (toward nucleus), Myosin (interacts with microfilaments).

Golgi Apparatus

  • Function: Processes and sorts proteins.

  • Exocytosis: Process of vesicles fusing with the plasma membrane to release contents outside the cell.

Energy-Producing Organelles

Mitochondria

  • Found in both plant and animal cells; involved in energy conversion and respiration.

  • Contains its own DNA, semi-autonomous nature aids in inheritance and replication.

Chloroplasts

  • Found only in plants; site for photosynthesis.

  • Also semi-autonomous with DNA.

Organelles Specialized for Processing and Storage

Peroxisomes

  • Breakdown of fatty acids and toxic substances (e.g., hydrogen peroxide).

Vacuoles

  • Large storage compartments in plant cells, facilitate storage (e.g., water, nutrients).

Lysosomes

  • Contain enzymes for digestion of macromolecules and recycling of organelles.

Membrane Functions

Cell Membrane Characteristics

  • Selective permeability: Regulates what enters/exits the cell.

  • Recognition functions: Contains carbohydrate tags for cell identification.

Functions of Various Organelles

  • Nucleus: Stores genetic material; processes rRNA.

  • ER: Rough ER (protein synthesis), Smooth ER (lipids, detoxification).

  • Golgi apparatus: Sorts and modifies proteins; glycosylation.

  • Functions of vacuoles, lysosomes, and peroxisomes.

Biological Molecules Role in Cell Structure

  • Cell membrane composed of phospholipids: Forms hydrophobic barrier.

  • Transmembrane proteins: Enable transport of materials, facilitate communication.

  • Cell wall composed of cellulose (carbohydrate) for structural support.

Transport Mechanisms

Types of Membrane Transport

Passive Transport

  • Molecules move spontaneously down concentration gradient (e.g., facilitated diffusion using transport proteins).

  • Example: Glucose moving through carrier proteins with no energy required.

Active Transport

  • Requires energy to move molecules against a concentration gradient.

  • Primary active transport: Direct use of ATP (e.g., Na⁺/K⁺ pump).

  • Secondary active transport: Utilizes ion gradients established by primary active transport.

Osmosis and Tonicity in Plant and Animal Cells

Osmosis

  • Movement of water across semi-permeable membranes based on solute concentration.

  • Isotonic: Equal concentration inside and out; cell remains stable.

  • Hypertonic: Higher solute outside than inside; causes water to leave cell leading to shrinkage (plasmolysis in plants).

  • Hypotonic: Lower solute outside; water enters cell, possibly leading to lysis in animal cells but valid for plant cell structure due to cell wall.

Examples of Tonicity

  • Plant health status related to external solution concentration (isotonic, hypertonic, hypotonic).

Thermodynamics and Energy Transfers

Laws of Thermodynamics

  1. Energy cannot be created or destroyed; only transformed.

  2. Energy transfers lead to inefficiency (increased disorder or entropy).

Reaction Energetics

ATP Hydrolysis

  • Breaking down ATP to ADP releases energy: exergonic reaction.

  • Negative delta G; spontaneous process as energy is released.

Summary of Key Concepts

  • Understanding structures/functions in cellular context is critical for biological concepts.

  • Emphasis on energy, transport mechanisms, and thermodynamics vital for cellular functioning.