Cell Biology Overview

Cell Biology

Cell Theory

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

Types of Cells

1. Prokaryotic Cells

   • Lack a nucleus and membrane-bound organelles.
   • Smaller and simpler (e.g., bacteria).
   • Genetic material (DNA) is circular and located in the nucleoid.

2. Eukaryotic Cells

   • Have a nucleus and membrane-bound organelles.
   • Larger and more complex (e.g., plant and animal cells).
   • DNA is linear and organized into chromosomes.

Cell Structure

• Plasma Membrane:

  • Semi-permeable barrier that regulates transport in and out of the cell.

• Nucleus:

  • Contains genetic material (DNA).
  • Site of RNA synthesis and ribosome assembly.

• Cytoplasm:

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

• Organelles:

  • Mitochondria: Powerhouse of the cell; site of ATP (energy) production.
  • Endoplasmic Reticulum (ER):
    • Rough ER: Studded with ribosomes; synthesizes proteins.
    • Smooth ER: Synthesizes lipids; detoxifies toxins.
  • Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or use within cells.
  • Lysosomes: Contains enzymes for digestion of waste materials and cellular debris.
  • Chloroplasts (in plant cells): Site of photosynthesis; contains chlorophyll.

Cellular Processes

• Cellular Respiration:

  • Process of converting glucose and oxygen into ATP, carbon dioxide, and water.
  • Occurs in mitochondria.

• Photosynthesis (in plants):

  • Process of converting sunlight, carbon dioxide, and water into glucose and oxygen.
  • Occurs in chloroplasts.

• Protein Synthesis:

  • Transcription: DNA is transcribed to mRNA in the nucleus.
  • Translation: mRNA is translated to protein at ribosomes.

Cell Division

• Mitosis:

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

• Meiosis:

  • Process of cell division that produces gametes (sperm and egg).
  • Involves two rounds of division and results in four non-identical cells.

Cell Communication

• Signaling Molecules:

  • Hormones, neurotransmitters, and other chemicals that facilitate communication between cells.

• Receptors:

  • Proteins on cell surfaces that bind to signaling molecules and initiate a response.

Membrane Transport

• Passive Transport:

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

• Active Transport:

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

Cell Cycle

• Sequence of stages that a cell goes through to divide and replicate.
• Phases: Interphase (G1, S, G2) and M phase (mitosis and cytokinesis).

Cell Biology

Cell Theory

• Living organisms are made entirely of cells.
• Cells serve as the fundamental units of life.
• All cells originate from pre-existing cells.

Types of Cells

• Prokaryotic Cells:

  • Possess no nucleus or membrane-bound organelles.
  • Generally smaller and simpler, exemplified by bacteria.
  • Circular DNA located in the nucleoid region.

• Eukaryotic Cells:

  • Contain a nucleus and membrane-bound organelles.
  • Larger and more complex, found in plants and animals.
  • DNA is linear and arranged in chromosomes.

Cell Structure

• Plasma Membrane:

  • Semi-permeable structure managing substance transport.

• Nucleus:

  • Houses genetic material (DNA).
  • Primary site for RNA synthesis and ribosome assembly.

• Cytoplasm:

  • Gel-like fluid where cellular activities occur.
  • Contains organelles and the cytoskeleton for structure.

• Organelles:

  • Mitochondria:
    • Known as the cell’s powerhouse; location of ATP production.
  • Endoplasmic Reticulum (ER):
    • Rough ER: Contains ribosomes for protein synthesis.
    • Smooth ER: Responsible for lipid synthesis and detoxification.
  • Golgi Apparatus:
    • Modifies, sorts, and packages proteins and lipids for cellular use or export.
  • Lysosomes:
    • Enzyme-filled structures that digest waste and cellular debris.
  • Chloroplasts:
    • Found in plant cells; site of photosynthesis and chlorophyll production.

Cellular Processes

• Cellular Respiration:

  • Converts glucose and oxygen into ATP, carbon dioxide, and water.
  • Takes place in the mitochondria.

• Photosynthesis (in plants):

  • Transforms sunlight, carbon dioxide, and water into glucose and oxygen.
  • Occurs in chloroplasts.

• Protein Synthesis:

  • Transcription:
    • DNA is converted to mRNA in the nucleus.
  • Translation:
    • mRNA is translated into proteins by ribosomes.

Cell Division

• Mitosis:

  • Type of cell division yielding two identical daughter cells.
  • Progresses through phases: Prophase, Metaphase, Anaphase, Telophase.

• Meiosis:

  • Specialized cell division for gamete (sperm and egg) production.
  • Involves two division rounds, producing four non-identical cells.

Cell Communication

• Signaling Molecules:

  • Includes hormones and neurotransmitters that enable intercellular communication.

• Receptors:

  • Surface proteins that bind signaling molecules to trigger cellular responses.

Membrane Transport

• Passive Transport:

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

• Active Transport:

  • Energy-dependent movement of substances against their concentration gradients (e.g., sodium-potassium pump).

Cell Cycle

• Series of phases a cell undergoes for division and replication.
• Comprises Interphase (G1, S, G2) and the M phase (mitosis and cytokinesis).