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.