Cell Biology Overview

Cell Biology

Cell Theory
- All living organisms are composed of one or more cells.
- The cell is the basic unit of life.
- All cells arise from pre-existing cells.
Types of Cells
- Prokaryotic Cells
  - Lack a nucleus and membrane-bound organelles.
  - Generally smaller and simpler (e.g., bacteria).
- Eukaryotic Cells
  - Contain a nucleus and membrane-bound organelles.
  - Larger and more complex (e.g., plant and animal cells).
Cell Structure
- Cell Membrane
  - Phospholipid bilayer that regulates what enters and exits the cell.
  - Contains proteins, cholesterol, and carbohydrates.
- Cytoplasm
  - Gel-like substance inside the cell, where organelles are located.
- Nucleus
  - Contains genetic material (DNA).
  - Controls cellular activities and reproduction.
- Organelles
  - Mitochondria: Powerhouse of the cell, site of ATP (energy) production.
  - Ribosomes: Sites of protein synthesis.
  - Endoplasmic Reticulum (ER):
    - Rough ER: Studded with ribosomes, involved in protein synthesis.
    - Smooth ER: Lacks ribosomes, involved in lipid synthesis and detoxification.
  - Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or use within the cell.
  - Lysosomes: Contain enzymes for digestion of cellular waste and macromolecules.
  - Chloroplasts (in plant cells): Site of photosynthesis, contain chlorophyll.
Cell Division
- Mitosis: Process of cell division that results in two identical daughter cells; involved in growth and repair.
  - Stages: Prophase, Metaphase, Anaphase, Telophase.
- Meiosis: Specialized form of cell division that produces gametes (sex cells).
  - Results in four genetically diverse cells; crucial for sexual reproduction.
Cell Communication
- Cells communicate through chemical signals (hormones, neurotransmitters).
- Receptors on cell membranes receive signals and trigger responses (signal transduction).
Metabolism
- Anabolism: Building up of molecules (e.g., synthesis of proteins).
- Catabolism: Breaking down of molecules (e.g., cellular respiration).
Transport Mechanisms
- Passive Transport: Movement of substances across a cell membrane without energy (e.g., diffusion, osmosis).
- Active Transport: Movement of substances against a concentration gradient; requires energy (e.g., sodium-potassium pump).
Cell Specialization
- Cells differentiate to perform specific functions (e.g., muscle cells, nerve cells).
- Stem cells retain the ability to differentiate into various cell types.
Cell Cycle Regulation
- Controlled by proteins called cyclins and cyclin-dependent kinases (CDKs).
- Checkpoints ensure proper division and function; dysregulation can lead to cancer.

Cell Theory

All organisms are made of one or more cells, the basic unit of life.
New cells originate from existing cells through cell division.

Types of Cells

Prokaryotic Cells
- Do not contain a nucleus or membrane-bound organelles.
- Smaller and simpler in structure, commonly represented by bacteria.
Eukaryotic Cells
- Possess a nucleus and various membrane-bound organelles.
- Larger and more complex, include plant and animal cells.

Cell Structure

Cell Membrane
- Composed of a phospholipid bilayer that monitors the entry and exit of substances.
- Contains proteins, cholesterol, and carbohydrates for functionality.
Cytoplasm
- Gel-like medium within the cell housing the organelles.
Nucleus
- Houses genetic material in the form of DNA.
- Regulates cellular activities and reproduction.
Organelles
- Mitochondria: Known as the powerhouse of the cell; primary site for ATP production.
- Ribosomes: Responsible for protein synthesis.
- Endoplasmic Reticulum (ER):
  - Rough ER has ribosomes on its surface, plays a role in protein synthesis.
  - Smooth ER lacks ribosomes, involved in lipid synthesis and detoxification.
- Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for further use or secretion.
- Lysosomes: Contain enzymes to digest waste materials and cellular debris.
- Chloroplasts (located in plant cells): Sites for photosynthesis, containing chlorophyll for capturing light energy.

Cell Division

Mitosis
- Leads to two genetically identical daughter cells; essential for growth and repair.
- Includes stages: Prophase, Metaphase, Anaphase, Telophase.
Meiosis
- Special type of cell division producing gametes (sex cells).
- Results in four genetically diverse cells; vital for sexual reproduction.

Cell Communication

Cells utilize chemical signals, including hormones and neurotransmitters, to communicate.
Cell membrane receptors detect these signals, initiating internal responses via signal transduction pathways.

Metabolism

Anabolism
- The synthesis of complex molecules from simpler ones, such as protein formation.
Catabolism
- The breakdown of complex molecules into simpler ones, exemplified by cellular respiration.

Transport Mechanisms

Passive Transport
- Involves the movement of substances across cell membranes without requiring energy, examples include diffusion and osmosis.
Active Transport
- Requires energy to move substances against their concentration gradient (e.g., sodium-potassium pump).

Cell Specialization

Cells differentiate to perform distinct functions, e.g., muscle and nerve cells.
Stem cells have the capability to evolve into various cell types.

Cell Cycle Regulation

Controlled by cyclins and cyclin-dependent kinases (CDKs).
Checkpoints monitor the cell cycle for errors; dysregulation may result in cancer development.