Cell Structure and Division

Cell Structure

• The basic structural and functional unit of life
• Composed of:
  • Plasma membrane (cell membrane)
  • Cytoplasm
  • Genetic material (DNA or RNA)
  • Various organelles

Cell Division

• Process by which a cell divides into two daughter cells
• Types:
  1. Mitosis: somatic cells (body cells) divide to produce two identical daughter cells
  2. Meiosis: reproductive cells (gametes) divide to produce four non-identical daughter cells
• Phases:
  1. Interphase: cell growth, replication of DNA, and preparation for cell division
  2. Prophase: chromatin condenses, nuclear envelope breaks down, and spindle fibers form
  3. Metaphase: chromosomes line up at the center of the cell
  4. Anaphase: sister chromatids separate and move to opposite poles
  5. Telophase: nuclear envelope reforms, and chromatin uncoils
  6. Cytokinesis: cytoplasm divides, and cell splits into two daughter cells

Cell Membrane

• Thin, semi-permeable membrane surrounding the cell
• Composed of:
  • Phospholipid bilayer (hydrophobic tails and hydrophilic heads)
  • Proteins ( integral and peripheral)
  • Cholesterol (stabilizes the membrane)
• Functions:
  • Regulates what enters and leaves the cell
  • Maintains cell shape and structure
  • Acts as a barrier against external environment

Cell Organelles

• Specialized structures within the cell that perform specific functions
• Types:
  • Nucleus: contains genetic material (DNA) and controls cell growth and division
  • Mitochondria: generates energy for the cell through cellular respiration
  • Endoplasmic Reticulum (ER): synthesizes and transports proteins and lipids
  • Golgi Apparatus: modifies and packages proteins and lipids for transport
  • Lysosomes: contains digestive enzymes and breaks down cellular waste and foreign substances
  • Ribosomes: site of protein synthesis

Cell Transport

• Movement of molecules and ions across the cell membrane
• Types:
  • Passive Transport:
    • Diffusion: movement of molecules from high to low concentration
    • Osmosis: movement of water molecules from high to low concentration
  • Active Transport: movement of molecules against their concentration gradient using energy
  • Facilitated Diffusion: movement of molecules through transport proteins
  • Vesicular Transport: movement of molecules using vesicles (e.g., exocytosis and endocytosis)

Cell Structure

• Cell is the basic structural and functional unit of life
• Composed of plasma membrane, cytoplasm, genetic material, and various organelles
• Plasma membrane is semi-permeable, regulating what enters and leaves the cell
• Cytoplasm is a jelly-like substance where metabolic processes occur
• Genetic material is made up of DNA or RNA

Cell Division

• Cell division is the process by which a cell divides into two daughter cells
• Mitosis occurs in somatic cells, producing two identical daughter cells
• Meiosis occurs in reproductive cells, producing four non-identical daughter cells
• Interphase involves cell growth, DNA replication, and preparation for cell division
• Prophase involves chromatin condensation, nuclear envelope breakdown, and spindle fiber formation
• Metaphase involves chromosomal alignment at the center of the cell
• Anaphase involves sister chromatid separation and movement to opposite poles
• Telophase involves nuclear envelope reformation and chromatin uncoiling
• Cytokinesis involves cytoplasmic division and cell splitting into two daughter cells

Cell Membrane

• Cell membrane is a thin, semi-permeable membrane surrounding the cell
• Composed of phospholipid bilayer, proteins, and cholesterol
• Phospholipid bilayer has hydrophobic tails and hydrophilic heads
• Proteins are integral and peripheral, and cholesterol stabilizes the membrane
• Cell membrane regulates what enters and leaves the cell, maintains cell shape, and acts as a barrier

Cell Organelles

• Cell organelles are specialized structures within the cell that perform specific functions
• Nucleus contains genetic material and controls cell growth and division
• Mitochondria generates energy for the cell through cellular respiration
• Endoplasmic Reticulum (ER) synthesizes and transports proteins and lipids
• Golgi Apparatus modifies and packages proteins and lipids for transport
• Lysosomes contain digestive enzymes and break down cellular waste and foreign substances
• Ribosomes are the site of protein synthesis

Cell Transport

• Cell transport involves the movement of molecules and ions across the cell membrane
• Passive transport involves movement of molecules from high to low concentration
• Diffusion involves the movement of molecules from high to low concentration
• Osmosis involves the movement of water molecules from high to low concentration
• Active transport involves movement of molecules against their concentration gradient using energy
• Facilitated diffusion involves movement of molecules through transport proteins
• Vesicular transport involves movement of molecules using vesicles, such as exocytosis and endocytosis