Cell Biology: Basic Unit of Life

Cell Biology

Basic Unit of Life

• Cells are the fundamental units of structure and function in living organisms.
• Two main types: Prokaryotic (no nucleus, simpler) and Eukaryotic (nucleus, complex).

Cell Structure

1. Cell Membrane

   • Semi-permeable barrier.
   • Composed of a phospholipid bilayer with embedded proteins.

2. Nucleus

   • Contains genetic material (DNA).
   • Controls cellular activities and gene expression.

3. Cytoplasm

   • Gel-like substance where cellular processes occur.
   • Contains organelles.

4. Organelles

   • Mitochondria: Powerhouse of the cell, site of ATP (energy) production.
   • Ribosomes: Sites of protein synthesis.
   • Endoplasmic Reticulum (ER):
     • Rough ER: Studded with ribosomes, synthesizes proteins.
     • Smooth ER: Synthesizes lipids and detoxifies.
   • Golgi Apparatus: Modifies, sorts, and packages proteins for secretion.
   • Lysosomes: Contain enzymes for digestion of waste materials.
   • Peroxisomes: Break down fatty acids and detoxify harmful substances.

Cell Division

• Mitosis: Process of cell division resulting in two identical daughter cells. Key phases:
  1. Prophase
  2. Metaphase
  3. Anaphase
  4. Telophase
• Meiosis: Specialized cell division that produces gametes (sperms and eggs), resulting in four genetically diverse cells.

Cellular Metabolism

• Anabolism: Building up molecules (e.g., protein synthesis).
• Catabolism: Breaking down molecules (e.g., cellular respiration).

Cell Communication

• Cells communicate through signaling molecules (e.g., hormones).
• Types of signaling:
  • Autocrine: Signals act on the same cell.
  • Paracrine: Signals act on nearby cells.
  • Endocrine: Signals travel through the bloodstream to distant cells.

Transport Mechanisms

1. Passive Transport: Movement of molecules across the membrane without energy (e.g., diffusion, osmosis).
2. Active Transport: Requires energy to move molecules against a concentration gradient (e.g., sodium-potassium pump).

Cell Theory

• All living things are made of cells.
• Cells are the basic units of life.
• All cells arise from pre-existing cells.

Stem Cells

• Undifferentiated cells that can develop into various cell types.
• Types include:
  • Embryonic Stem Cells: Can differentiate into any cell type.
  • Adult Stem Cells: More limited differentiation potential.

Apoptosis

• Programmed cell death, a normal part of development and homeostasis.
• Distinct from necrosis (uncontrolled cell death).

Basic Unit of Life

• Cells serve as the basic structural and functional units in all living organisms.
• Two primary types of cells:
  • Prokaryotic cells lack a nucleus and have a simpler structure.
  • Eukaryotic cells possess a nucleus and are more complex.

Cell Structure

• Cell Membrane:

  • Acts as a semi-permeable barrier around the cell.
  • Made up of a phospholipid bilayer with proteins embedded for various functions.

• Nucleus:

  • Houses the cell's genetic material, DNA.
  • Regulates cellular functions and gene expression.

• Cytoplasm:

  • Gel-like medium where metabolic activities take place.
  • Contains various organelles that perform specific functions.

• Organelles:

  • Mitochondria: Known as the powerhouse of the cell, responsible for ATP production.
  • Ribosomes: Key sites for protein synthesis.
  • Endoplasmic Reticulum (ER):
    • Rough ER: Covered with ribosomes, synthesizes proteins.
    • Smooth ER: Produces lipids and detoxifies harmful substances.
  • Golgi Apparatus: Modifies, sorts, and packages proteins for secretion outside the cell.
  • Lysosomes: Contain digestive enzymes for breaking down waste materials.
  • Peroxisomes: Function in fatty acid breakdown and detoxifying harmful compounds.

Cell Division

• Mitosis:

  • Leads to two genetically identical daughter cells.
  • Key phases include prophase, metaphase, anaphase, and telophase.

• Meiosis:

  • A specialized form of cell division generating four genetically diverse gametes (sperm and eggs).

Cellular Metabolism

• Anabolism: Process of building complex molecules from simpler ones (e.g., protein synthesis).
• Catabolism: Involves breaking down molecules for energy (e.g., cellular respiration).

Cell Communication

• Cells communicate via signaling molecules like hormones.
• Types of signaling mechanisms include:
  • Autocrine: Signals affect the same cell.
  • Paracrine: Signals influence nearby cells.
  • Endocrine: Signals are distributed through the bloodstream to distant targets.

Transport Mechanisms

• Passive Transport: Involves the movement of molecules across cell membranes without energy, such as through diffusion and osmosis.
• Active Transport: Requires energy to move molecules against their concentration gradient, exemplified by the sodium-potassium pump.

Cell Theory

• Asserts that all living organisms are composed of cells.
• Cells are recognized as the basic units of life.
• New cells arise only from existing cells.

Stem Cells

• Undifferentiated cells with the potential to differentiate into multiple cell types.
• Types of stem cells include:
  • Embryonic Stem Cells: Can develop into any cell type.
  • Adult Stem Cells: Have a limited capacity for differentiation.

Apoptosis

• Refers to programmed cell death, an essential process in development and maintaining homeostasis.
• Distinguishable from necrosis, which is an uncontrolled form of cell death.