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
- Prokaryotic Cells
  - Lack a nucleus and membrane-bound organelles.
  - Examples: Bacteria and Archaea.
- Eukaryotic Cells
  - Have a nucleus and membrane-bound organelles.
  - Examples: Plant cells, animal cells, fungi, and protists.
Cell Structure
- Plasma Membrane
  - Semi-permeable barrier that controls movement in and out of the cell.
- Nucleus
  - Contains genetic material (DNA) and controls cellular activities.
- Cytoplasm
  - Gel-like substance where cell components are suspended.
- Organelles
  - Mitochondria: Powerhouse of the cell, produces ATP through respiration.
  - Ribosomes: Sites of protein synthesis.
  - Endoplasmic Reticulum (ER):
    - Rough ER: Studded with ribosomes, synthesizes proteins.
    - Smooth ER: Lacks ribosomes, involved in lipid synthesis.
  - Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.
  - Lysosomes: Contain enzymes for digestion of waste materials.
  - Chloroplasts (in plant cells): Site of photosynthesis.
Cell Division
- Mitosis
  - Process of cell division resulting in two identical daughter cells.
  - Stages: Prophase, Metaphase, Anaphase, Telophase.
- Meiosis
  - Specialized form of cell division that produces gametes.
  - Results in four non-identical daughter cells with half the chromosome number.
Cell Function
- Metabolism
  - All biochemical processes occurring within cells, including catabolism and anabolism.
- Cell Signaling
  - Mechanisms through which cells communicate with each other.
  - Involves ligands, receptors, and signal transduction pathways.
Cellular Transport
- Passive Transport
  - Movement of substances across cell membranes without energy (e.g., diffusion, osmosis).
- Active Transport
  - Movement of substances against a concentration gradient, requiring energy (e.g., sodium-potassium pump).
Cell Communication
- Direct Communication
  - Gap junctions allow direct transfer of ions and small molecules between cells.
- Chemical Signaling
  - Involves hormones and neurotransmitters acting on target cells.
Stem Cells
- Undifferentiated cells with the potential to develop into different cell types.
- Types: Embryonic stem cells and adult (somatic) stem cells.
Cell Cycle Regulation
- Controlled by checkpoints (G1, S, G2, M phases) to ensure proper division.
- Abnormal regulation can lead to cancer.

Cell Theory

All living organisms are made up of cells.
The cell is considered the basic unit of life.
Cells originate from pre-existing cells.

Types of Cells

Prokaryotic Cells
- Do not have a nucleus or membrane-bound organelles.
- Examples include Bacteria and Archaea.
Eukaryotic Cells
- Contain a nucleus and various membrane-bound organelles.
- Examples include plant cells, animal cells, fungi, and protists.

Cell Structure

Plasma Membrane
- Functions as a semi-permeable barrier regulating movement in and out of the cell.
Nucleus
- Houses genetic material (DNA) and governs cellular functions.
Cytoplasm
- Gel-like matrix that suspends cell components.
Organelles
- Mitochondria: Known as the powerhouse, it generates ATP through respiration.
- Ribosomes: Responsible for protein synthesis.
- Endoplasmic Reticulum (ER):
  - Rough ER synthesizes proteins due to the presence of ribosomes.
  - Smooth ER is involved in lipid synthesis and lacks ribosomes.
- Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for distribution.
- Lysosomes: Contain digestive enzymes for breaking down waste.
- Chloroplasts: Found in plant cells, these are the sites for photosynthesis.

Cell Division

Mitosis
- A process that results in two genetically identical daughter cells.
- Involves distinct stages: Prophase, Metaphase, Anaphase, and Telophase.
Meiosis
- A specialized division that produces gametes (sex cells).
- Results in four non-identical daughter cells, each with half the number of chromosomes.

Cell Function

Metabolism
- Encompasses all biochemical processes in cells, including catabolism (breaking down molecules) and anabolism (constructing molecules).
Cell Signaling
- Refers to how cells communicate through mechanisms including ligands and receptors.
- Involves signal transduction pathways for effective communication.

Cellular Transport

Passive Transport
- Movement of substances across membranes without energy input (examples: diffusion and osmosis).
Active Transport
- Requires energy to move substances against their concentration gradient (e.g., sodium-potassium pump).

Cell Communication

Direct Communication
- Gap junctions allow for the direct transfer of ions and small molecules between adjacent cells.
Chemical Signaling
- Involves the action of hormones and neurotransmitters on target cells.