Cell Biology Overview

Cell Biology

• Cell Theory

  • All living organisms are composed of cells.
  • The cell is the basic unit of life.
  • New cells arise from existing cells.

• Types of Cells

  • Prokaryotic Cells
    • Lack a nucleus and membrane-bound organelles.
    • Generally smaller (e.g., bacteria).
  • Eukaryotic Cells
    • Have a nucleus and membrane-bound organelles.
    • Larger and more complex (e.g., plant and animal cells).

• Cell Structure

  • Plasma Membrane
    • Semi-permeable barrier.
    • Composed of phospholipid bilayer and proteins.
  • Nucleus
    • Contains genetic material (DNA).
    • Controls cell activities and gene expression.
  • Cytoplasm
    • Gel-like substance within the cell.
    • Site of metabolic processes.
  • Organelles
    • Mitochondria: Powerhouse of the cell, site of ATP production.
    • Ribosomes: Protein synthesis.
    • Endoplasmic Reticulum (ER):
      • Rough ER: Studded with ribosomes; involved in protein synthesis.
      • Smooth ER: Synthesizes lipids and detoxifies substances.
    • Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.
    • Lysosomes: Contain digestive enzymes for waste processing.
    • Chloroplasts (in plants): Site of photosynthesis.

• Cell Membrane Transport

  • Passive Transport
    • No energy required; substances move down their concentration gradient.
    • Includes diffusion, osmosis, and facilitated diffusion.
  • Active Transport
    • Requires energy (ATP); substances move against their concentration gradient.
    • Involves transport proteins and pumps.

• Cell Division

  • Mitosis
    • Process of somatic cell division leading to two identical daughter cells.
    • Phases: Prophase, Metaphase, Anaphase, Telophase.
  • Meiosis
    • Division of germ cells to produce gametes (sperm and eggs).
    • Involves two rounds of division resulting in four non-identical cells.

• Cell Signaling

  • Mechanisms by which cells communicate.
  • Involves signaling molecules, receptors, and response pathways.
  • Types:
    • Autocrine: Signals act on the same cell.
    • Paracrine: Signals act on nearby cells.
    • Endocrine: Signals (hormones) travel through the bloodstream.

• Cellular Metabolism

  • Catabolism: Breakdown of molecules to release energy.
  • Anabolism: Synthesis of complex molecules from simpler ones, requiring energy.

• Cell Cycle Regulation

  • Controlled by checkpoints that ensure proper cell division.
  • Key proteins: Cyclins and cyclin-dependent kinases (CDKs).

• Stem Cells

  • Undifferentiated cells with potential to develop into various cell types.
  • Types:
    • Embryonic Stem Cells: Pluripotent; can form any cell type.
    • Adult Stem Cells: Multipotent; limited to specific lineages.

Cell Theory

• All living organisms are made up of cells, the fundamental unit of life.
• New cells arise from pre-existing cells through cell division.

Types of Cells

• Prokaryotic Cells:
  • Lack a nucleus and membrane-enclosed organelles.
  • Smaller in size compared to eukaryotic cells.
  • Examples: bacteria.
• Eukaryotic Cells:
  • Contain a nucleus and membrane-bound organelles.
  • Larger and more complex than prokaryotic cells.
  • Examples: plant and animal cells.

Cell Structure

• Plasma Membrane:
  • A semi-permeable barrier that controls the movement of substances in and out of the cell.
  • Composed of a phospholipid bilayer and embedded proteins.
• Nucleus:
  • Houses the genetic material (DNA).
  • Regulates cellular activities and gene expression.
• Cytoplasm:
  • Gel-like substance filling the cell.
  • Where many metabolic processes occur.
• Organelles: Specialized structures within the cell that perform specific functions.
  • Mitochondria: Powerhouse of the cell; responsible for ATP production (energy currency).
  • Ribosomes: Sites of protein synthesis.
  • Endoplasmic Reticulum (ER):
    • Rough ER: Studded with ribosomes, involved in protein synthesis.
    • Smooth ER: Synthesizes lipids and detoxifies substances.
  • Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.
  • Lysosomes: Contain digestive enzymes for breaking down waste materials.
  • Chloroplasts (in plants): Sites of photosynthesis, converting light energy into chemical energy.

Cell Membrane Transport

• Passive Transport:
  • Movement of substances across the cell membrane without requiring energy.
  • Substances move down their concentration gradient (from high to low concentration).
  • Examples: diffusion, osmosis, and facilitated diffusion.
• Active Transport:
  • Movement of substances against their concentration gradient (from low to high concentration).
  • Requires energy (ATP).
  • Involves transport proteins and pumps.

Cell Division

• Mitosis:
  • Division of somatic (body) cells resulting in two genetically identical daughter cells.
  • Consists of four phases: Prophase, Metaphase, Anaphase, and Telophase.
• Meiosis:
  • Division of germ cells (sperm and egg cells) resulting in four genetically distinct daughter cells.
  • Involves two rounds of division.

Cell Signaling

• Mechanisms by which cells communicate with each other.
• Involves signaling molecules, receptors, and response pathways.
• Types:
  • Autocrine: Signals act on the same cell that produced them.
  • Paracrine: Signals act on nearby cells.
  • Endocrine: Signals (hormones) travel through the bloodstream to distant target cells.

Cellular Metabolism

• Catabolism: Breakdown of complex molecules into simpler ones, releasing energy.
• Anabolism: Synthesis of complex molecules from simpler ones, requiring energy.

Cell Cycle Regulation

• Controlled by checkpoints that ensure proper cell division.
• Key proteins involved: Cyclins and cyclin-dependent kinases (CDKs).

Stem Cells

• Undifferentiated cells with the potential to develop into various cell types.
• Types:
  • Embryonic Stem Cells: Pluripotent; able to differentiate into any cell type in the body.
  • Adult Stem Cells: Multipotent; restricted to specific lineages of cells.