Cell Biology All Units

Unit Overview

  • Sub-Cellular Organelles: Key differences between Prokaryotic and Eukaryotic cells.

Common Features

  1. Plasma Membrane: Similar construction between cell types.

  2. Genetic Material: Both have DNA as genetic material.

  3. Transcription and Translation: Similar mechanisms observed in both cell types.

  4. Metabolic Pathways: Same metabolic pathways such as glycolysis.

  5. ATP Production: Similar conservation of chemical energy in the form of ATP.

  6. Photosynthesis: Similar mechanism observed in green plants.

  7. Protein Synthesis: Similar mechanisms for synthesizing proteins.

Key Differences

Prokaryotic Features

  1. Genetic Material: DNA is in the form of a nucleoid, lacks a nuclear envelope.

  2. Chromosome Structure: Contains a single circular chromosome.

  3. Membrane-bound Organelles: Absent in prokaryotic cells.

  4. Transport Mechanisms: Materials move via simple diffusion rather than complex systems.

  5. Cell Division: Mitosis is absent; binary fission occurs instead.

  6. Chromosomal Compaction: Less genetic material, lacks histone proteins.

  7. Size: Typically 1-5 µm in length.

Eukaryotic Features

  1. Nucleus: Contains a membrane-bound nucleus.

  2. Genetic Material: More genetic material organized into linear chromosomes.

  3. Membrane-bound Organelles: Present in eukaryotic cells.

  4. Cell Division: Mitosis and meiosis are present with spindle apparatus in cell division.

  5. Size: Typically 10-30 µm in size.

Mitochondria Ultrastructure

  1. Shape: Sausage-shaped organelles.

  2. Membranes: Composed of an outer and inner mitochondrial membrane.

  3. Components:

    • Outer Membrane: Contains porins for transport, about 50% lipid by weight.

    • Inner Membrane: Has high protein-lipid ratio, contains ATP synthase and proteins for the ETC.

    • Matrix: Contains enzymes for aerobic respiration, ribosomes, and circular mitochondrial DNA.

    • Cristae: Folded inner membrane increasing surface area for ATP production.

Nuclear Structure

  1. Nuclear Envelope: Double membrane structure, separates nucleus from cytoplasm.

  2. Nuclear Pore Complex: Facilitates transport of materials between nucleus and cytoplasm.

  3. Nucleolus: Involved in rRNA synthesis and ribosome assembly.

Cytoskeleton Functions

  1. Structure: Provides mechanical support to the cell.

  2. Transport: Positioning and movement of organelles.

  3. Cell Movement: Involvement of actin filaments in cell motility.

  4. Cell Division: Essential for chromosome segregation during mitosis.

Membrane Structure and Functions

  1. Membrane Composition: Lipid bilayers with embedded proteins; amphipathic nature.

  2. Transport Mechanisms:

    • Passive Transport: Includes simple diffusion and facilitated diffusion.

    • Active Transport: Utilizes ATP for moving substances against their gradient.

Cell Cycle Overview

  1. Phases:

    • Interphase: Cell growth and DNA replication.

    • M Phase: Mitosis and cytokinesis.

  2. Checkpoints: Regulatory points for assessing cell cycle progression and DNA integrity.

Apoptosis and Necrosis

  1. Apoptosis: Programmed cell death, a normal cellular process.

  2. Necrosis: Uncontrolled cell death due to external factors, often harmful.

Meiosis

  1. Two Divisions: Meiosis I (reductional) and Meiosis II (equational).

  2. Significance: Genetic diversity through crossing over and independent assortment.