Overview of Cell Biology

Study of cells, their physiological properties, structure, organelles, interactions, and behavior.
Fundamental unit of life; all living organisms are composed of one or more cells.

Prokaryotic Cells
- Lack a nucleus and membrane-bound organelles.
- DNA is circular and located in the nucleoid region.
- Example: Bacteria and Archaea.
Eukaryotic Cells
- Have a nucleus and membrane-bound organelles.
- DNA is linear and organized into chromosomes.
- Example: Plants, animals, fungi, and protists.

Cell Membrane
- Semi-permeable barrier; regulates entry and exit of substances.
- Composed of a phospholipid bilayer with embedded proteins.
Nucleus
- Contains genetic material (DNA).
- Site of transcription and RNA processing.
Mitochondria
- Powerhouse of the cell; produces ATP through cellular respiration.
- Has its own DNA and double membrane.
Ribosomes
- Sites of protein synthesis; can be free in cytoplasm or bound to the endoplasmic reticulum.
Endoplasmic Reticulum (ER)
- Rough ER: Studded with ribosomes; synthesizes proteins.
- Smooth ER: Lacks ribosomes; synthesizes lipids and detoxifies.
Golgi Apparatus
- Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.
Lysosomes
- Contains digestive enzymes; breaks down waste materials and cellular debris.
Cytoskeleton
- Provides structural support; composed of microfilaments, intermediate filaments, and microtubules.
Plasma Membrane
- Responsible for cell signaling and communication.

Mitosis
- Process of cell division that results in two identical daughter cells.
- Phases: Prophase, Metaphase, Anaphase, Telophase.
Meiosis
- Type of cell division that produces gametes (sperm and eggs).
- Involves two rounds of division; reduces chromosome number by half.

Catabolism
- Breakdown of molecules to obtain energy (e.g., glycolysis, Krebs cycle).
Anabolism
- Synthesis of complex molecules from simpler ones, requiring energy (e.g., protein synthesis).

Signal Transduction
- Process by which a cell responds to external signals (hormones, neurotransmitters).
- Involves receptors, second messengers, and cellular responses.

Passive Transport
- Movement of substances across the membrane without energy (e.g., diffusion, osmosis).
Active Transport
- Movement of substances against their concentration gradient, requiring energy (e.g., sodium-potassium pump).

Cell biology examines the properties, structure, organelles, and interactions of cells, which are the fundamental units of life.
All living organisms consist of one or more cells.

Prokaryotic Cells
- Characterized by the absence of a nucleus and membrane-bound organelles.
- Contain circular DNA located in a nucleoid region.
- Examples include Bacteria and Archaea.
Eukaryotic Cells
- Feature a defined nucleus and membrane-bound organelles.
- DNA is linear and organized into chromosomes.
- Include plants, animals, fungi, and protists as examples.

Cell Membrane
- Acts as a semi-permeable barrier, regulating substance entry and exit.
- Composed of a phospholipid bilayer with embedded proteins.
Nucleus
- Houses genetic material (DNA) and is the site of transcription and RNA processing.
Mitochondria
- Known as the powerhouse of the cell, they produce ATP through cellular respiration.
- Possess their own DNA and double membranes.
Ribosomes
- Sites for protein synthesis, found free in the cytoplasm or bound to the endoplasmic reticulum.
Endoplasmic Reticulum (ER)
- Rough ER contains ribosomes and synthesizes proteins.
- Smooth ER lacks ribosomes and is involved in lipid synthesis and detoxification.
Golgi Apparatus
- Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.
Lysosomes
- Contain digestive enzymes to break down waste materials and cellular debris.
Cytoskeleton
- Provides structural support and is composed of microfilaments, intermediate filaments, and microtubules.
Plasma Membrane
- Facilitates cell signaling and communication.

Mitosis
- A process resulting in two identical daughter cells.
- Comprises four phases: Prophase, Metaphase, Anaphase, and Telophase.
Meiosis
- Produces gametes (sperm and eggs) and involves two rounds of division, reducing the chromosome number by half.

Catabolism
- Involves the breakdown of molecules to release energy, exemplified by glycolysis and the Krebs cycle.
Anabolism
- The process of synthesizing complex molecules from simpler ones, which requires energy, such as in protein synthesis.

Signal Transduction
- Describes how cells respond to external signals like hormones and neurotransmitters.
- Involves receptors, second messengers, and subsequent cellular responses.

Passive Transport
- Movement of substances across the membrane without energy expenditure; includes processes like diffusion and osmosis.
Active Transport
- Movement of substances against their concentration gradient, which requires energy, e.g., the sodium-potassium pump.