Cell Theory, Cell Structure, and Organelles - VOCABULARY Flashcards
Cell Theory and Core Concepts
Outline the cell theory
- All organisms are composed of one or more cells
- Cells are the smallest units of life
- All cells come from pre-existing cells
Evidence for the cell theory
- Hooke (1665): first description of cells
- Leeuwenhoek: observed living cells
- Schleiden (1838): plants are made of cells
- Schwann (1839): animals also built from cells
- Pasteur (1860s): sterilization experiments show no spontaneous generation
Core Concepts (Educational Key Concepts)
E.K. 1.B.1: Conserved core processes across organisms; relatedness of all domains; structural evidence supports similarity
- Prokaryotic vs Eukaryotic similarities and differences include cytoskeleton, membrane-bound organelles, linear chromosomes, endomembrane systems
E.K. 2.B.3: Eukaryotic cells maintain internal membranes that partition the cell
- Archaea and Bacteria generally lack internal membranes and organelles; have cell walls
E.K. 2.A.3: Organisms exchange matter with environment
- Surface area-to-volume ratio affects resource exchange and waste removal
- Examples where exchange is critical: root hairs, alveoli, villi, microvilli
- Explanation: smaller cells have a more favorable SA:V for exchange
E.K. 4.A.2: Subcellular components drive essential cellular processes
- Ribosomes: rRNA + protein; site of protein synthesis
- Endoplasmic reticulum (ER): rough (protein synthesis, transport) vs smooth (lipid synthesis)
- Golgi apparatus: synthesis/packaging for transport; lysosome production
Size, Structure, and Organization
- Relative sizes (for quick recall):
- Cells: up to 100\,\mu\mathrm{m}
- Organelles: up to 10\,\mu\mathrm{m}
- Bacteria: up to 1\,\mu\mathrm{m}
- Viruses: up to 100\,\mathrm{nm}
- Membranes: up to 10\,\mathrm{nm}
- Molecules: near 1\,\mathrm{nm}
Prokaryotic vs Eukaryotic Cells
- DNA and chromosomes
- Prokaryotes: DNA in a ring, no membrane-bound chromosomes
- Eukaryotes: DNA with proteins as chromosomes
- DNA localization
- Prokaryotes: DNA in the cytoplasm (nucleoid region)
- Eukaryotes: DNA housed within a nucleus
- Ribosomes
- Prokaryotes: 70S
- Eukaryotes: 80S
- Internal organization
- Prokaryotes: no internal compartments
- Eukaryotes: internal membranes and organelles
- Size
- Prokaryotes: < 10\,\mu\mathrm{m}
- Eukaryotes: > 10\,\mu\mathrm{m}
Endomembrane System and Organelles
- Membranes and organelles localize intracellular metabolic processes and reactions
- Key components
- Nuclear envelope
- Endoplasmic reticulum (ER): rough and smooth
- Golgi apparatus
- Mitochondria; Chloroplasts (in plants)
The Ribosome and Protein Synthesis
- Ribosomes: small, universal structures composed of rRNA and protein
- Translation: synthesis of polypeptides from genetic instructions
Endomembrane System Details
- Rough ER: site of protein synthesis with membrane-bound ribosomes; intracellular transport
- Smooth ER: lipid synthesis
- Golgi: cisternae stack; modifies, sorts, and packages proteins and lipids; produces lysosomes
Organelles and Increased Cellular Complexity
- Organelle specialization enables compartmentalized metabolism and complex functions
- Endomembrane system functions: synthesis, modification, sorting, and transport of proteins and lipids
What Do Organelles Do? Quick Diagram Knowledge
- Typical eukaryotic cell diagram: label and recall functions
- Nucleus: houses genetic material; controls cellular activities
- Ribosomes: protein synthesis (free and bound)
- Rough ER: protein synthesis and quality control
- Smooth ER: lipid synthesis
- Golgi apparatus: packaging and distribution
- Vesicles: transport between organelles
Plant vs Animal Cells
- Plant cells
- Cell wall present; chloroplasts; large central vacuole; fixed, angular shape
- Animal cells
- No cell wall; no chloroplasts; small or no large vacuoles; centrioles; flexible, rounded shape
Ultrastructure of Prokaryotes (Example: E. coli)
- Diagram elements to identify
- Cell wall
- Plasma membrane
- Flagella
- Ribosomes
- Nucleoid (region with free DNA)
- Functions
- Cell wall: protects and maintains shape
- Plasma membrane: selective transport; site of metabolism and binary fission
- Flagella: motility
- Ribosomes: protein synthesis
- Nucleoid: contains circular DNA
Not All Cells Are Equal: Organelles and Function
- Concept: different cellular demands lead to varying organelle abundances
- Example focus areas (for thought):
- Ribosome abundance → protein synthesis capacity
- Mitochondria abundance → energy production
- Lysosome abundance → digestion and recycling
- Smooth ER abundance → lipid synthesis and detoxification
- Golgi abundance → packaging and transport
- Vacuole abundance → storage and osmotic balance
Consequences of Organellar Dysfunction (short prompts)
- If ribosomes fail to function: reduced protein synthesis
- If mitochondria fail: reduced ATP production
- If lysosomes fail: impaired digestion and recycling
- If smooth ER fails: lipid synthesis disruption
- If Golgi fails: improper processing/packaging of proteins and lipids
- If nucleus fails: altered gene expression and cell cycle control
Quick Takeaways
- The cell theory explains the common features and origins of cells across all life
- Prokaryotic and eukaryotic cells differ in nucleus presence, internal membranes, ribosome type, and size
- Eukaryotic cells use an endomembrane system to compartmentalize processes
- SA:V limits cell size; smaller cells exchange materials more efficiently
- Plant and animal cells share many organelles but differ in cell wall, chloroplasts, vacuoles, centrioles, and shape