Overview of Cell Biology

Overview of Cell Biology

• Study of cells, their physiological properties, structure, organelles, interactions, and behavior.
• Fundamental unit of life; all living organisms are composed of one or more cells.

Types of Cells

1. Prokaryotic Cells

   • Lack a nucleus and membrane-bound organelles.
   • DNA is circular and located in the nucleoid region.
   • Example: Bacteria and Archaea.

2. Eukaryotic Cells

   • Have a nucleus and membrane-bound organelles.
   • DNA is linear and organized into chromosomes.
   • Example: Plants, animals, fungi, and protists.

Cell Structure and Organelles

• Cell Membrane

  • Semi-permeable barrier; regulates entry and exit of substances.
  • Composed of a phospholipid bilayer with embedded proteins.

• Nucleus

  • Contains genetic material (DNA).
  • Site of transcription and RNA processing.

• Mitochondria

  • Powerhouse of the cell; produces ATP through cellular respiration.
  • Has its own DNA and double membrane.

• Ribosomes

  • Sites of protein synthesis; can be free in cytoplasm or bound to the endoplasmic reticulum.

• Endoplasmic Reticulum (ER)

  • Rough ER: Studded with ribosomes; synthesizes proteins.
  • Smooth ER: Lacks ribosomes; synthesizes lipids and detoxifies.

• Golgi Apparatus

  • Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

• Lysosomes

  • Contains digestive enzymes; breaks down waste materials and cellular debris.

• Cytoskeleton

  • Provides structural support; composed of microfilaments, intermediate filaments, and microtubules.

• Plasma Membrane

  • Responsible for cell signaling and communication.

Cell Division

• Mitosis

  • Process of cell division that results in two identical daughter cells.
  • Phases: Prophase, Metaphase, Anaphase, Telophase.

• Meiosis

  • Type of cell division that produces gametes (sperm and eggs).
  • Involves two rounds of division; reduces chromosome number by half.

Cellular Metabolism

• Catabolism

  • Breakdown of molecules to obtain energy (e.g., glycolysis, Krebs cycle).

• Anabolism

  • Synthesis of complex molecules from simpler ones, requiring energy (e.g., protein synthesis).

Cell Communication

• Signal Transduction
  • Process by which a cell responds to external signals (hormones, neurotransmitters).
  • Involves receptors, second messengers, and cellular responses.

Cellular Transport Mechanisms

• Passive Transport

  • Movement of substances across the membrane without energy (e.g., diffusion, osmosis).

• Active Transport

  • Movement of substances against their concentration gradient, requiring energy (e.g., sodium-potassium pump).

Cell Theory

1. All living organisms are composed of cells.
2. The cell is the basic unit of life.
3. All cells arise from pre-existing cells.

Overview of Cell Biology

• Cell biology examines the properties, structure, organelles, and interactions of cells, which are the fundamental units of life.
• All living organisms consist of one or more cells.

Types of Cells

• Prokaryotic Cells

  • Characterized by the absence of a nucleus and membrane-bound organelles.
  • Contain circular DNA located in a nucleoid region.
  • Examples include Bacteria and Archaea.

• Eukaryotic Cells

  • Feature a defined nucleus and membrane-bound organelles.
  • DNA is linear and organized into chromosomes.
  • Include plants, animals, fungi, and protists as examples.

Cell Structure and Organelles

• Cell Membrane

  • Acts as a semi-permeable barrier, regulating substance entry and exit.
  • Composed of a phospholipid bilayer with embedded proteins.

• Nucleus

  • Houses genetic material (DNA) and is the site of transcription and RNA processing.

• Mitochondria

  • Known as the powerhouse of the cell, they produce ATP through cellular respiration.
  • Possess their own DNA and double membranes.

• Ribosomes

  • Sites for protein synthesis, found free in the cytoplasm or bound to the endoplasmic reticulum.

• Endoplasmic Reticulum (ER)

  • Rough ER contains ribosomes and synthesizes proteins.
  • Smooth ER lacks ribosomes and is involved in lipid synthesis and detoxification.

• Golgi Apparatus

  • Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

• Lysosomes

  • Contain digestive enzymes to break down waste materials and cellular debris.

• Cytoskeleton

  • Provides structural support and is composed of microfilaments, intermediate filaments, and microtubules.

• Plasma Membrane

  • Facilitates cell signaling and communication.

Cell Division

• Mitosis

  • A process resulting in two identical daughter cells.
  • Comprises four phases: Prophase, Metaphase, Anaphase, and Telophase.

• Meiosis

  • Produces gametes (sperm and eggs) and involves two rounds of division, reducing the chromosome number by half.

Cellular Metabolism

• Catabolism

  • Involves the breakdown of molecules to release energy, exemplified by glycolysis and the Krebs cycle.

• Anabolism

  • The process of synthesizing complex molecules from simpler ones, which requires energy, such as in protein synthesis.

Cell Communication

• Signal Transduction
  • Describes how cells respond to external signals like hormones and neurotransmitters.
  • Involves receptors, second messengers, and subsequent cellular responses.

Cellular Transport Mechanisms

• Passive Transport

  • Movement of substances across the membrane without energy expenditure; includes processes like diffusion and osmosis.

• Active Transport

  • Movement of substances against their concentration gradient, which requires energy, e.g., the sodium-potassium pump.

Cell Theory

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