Cell Biology Study Notes

Prokaryotic Cells:
- Lack a nucleus and membrane-bound organelles.
- Examples: Bacteria and Archaea.
Eukaryotic Cells:
- Contain a nucleus and membrane-bound organelles.
- Examples: Animal cells, plant cells, fungi, and protists.

Cell Membrane:
- Semi-permeable barrier that regulates movement in and out of the cell.
- Composed of a phospholipid bilayer with embedded proteins.
Nucleus:
- Contains genetic material (DNA).
- Surrounded by a nuclear envelope with pores for substance exchange.
Organelles:
- Mitochondria: Energy production through cellular respiration.
- Ribosomes: Protein synthesis; can be free in cytoplasm or attached to the endoplasmic reticulum.
- Endoplasmic Reticulum (ER):
  - Rough ER: Studded with ribosomes; synthesizes proteins.
  - Smooth ER: Synthesizes lipids and detoxifies drugs.
- Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or delivery.
- Lysosomes: Contain enzymes for digestion of cellular waste and macromolecules.
- Chloroplasts (in plant cells): Site of photosynthesis.

Fluid Mosaic Model: Describes the cell membrane as a mosaic of diverse protein molecules floating in or on the fluid lipid bilayer.
Transport Mechanisms:
- Passive Transport: Movement of molecules without energy input (e.g., diffusion, osmosis).
- Active Transport: Movement of molecules against the concentration gradient using energy (e.g., sodium-potassium pump).

Mitosis: Process of cell division resulting in two identical daughter cells; essential for growth and repair.
- Phases: Prophase, Metaphase, Anaphase, Telophase.
Meiosis: Specialized cell division producing gametes (sperm and eggs) with half the chromosome number; essential for sexual reproduction.
- Involves two rounds of division: Meiosis I and Meiosis II.

Signal Transduction: Process by which a cell responds to external signals through receptors and intracellular pathways.
Types of Signaling:
- Autocrine: Cell signals itself.
- Paracrine: Signals to nearby cells.
- Endocrine: Hormones released into the bloodstream affecting distant cells.

Catabolism: Breakdown of molecules to obtain energy.
Anabolism: Synthesis of complex molecules from simpler ones, requiring energy.

Cells can differentiate into specialized types to perform specific functions; influenced by genetic and environmental factors.

Types:
- Embryonic Stem Cells: Pluripotent, can differentiate into any cell type.
- Adult Stem Cells: Multipotent, limited to specific cell types.
Potential applications in regenerative medicine and research.

Cells can adapt to changes in their environment through various mechanisms, including hypertrophy (increase in size), hyperplasia (increase in number), and atrophy (decrease in size).

These notes provide a concise overview of key concepts in cell biology, serving as a quick reference for study and review.

Prokaryotic Cells:
- No nucleus or membrane-bound organelles.
- Examples include Bacteria and Archaea.
Eukaryotic Cells:
- Contain a nucleus and defined organelles.
- Include animal cells, plant cells, fungi, and protists.

Cell Membrane:
- Acts as a semi-permeable barrier, controlling entry and exit of substances.
- Composed of a phospholipid bilayer with integrated proteins.
Nucleus:
- Houses genetic information (DNA).
- Encased by a nuclear envelope with pores facilitating material exchange.
Organelles:
- Mitochondria: Generate energy via cellular respiration.
- Ribosomes: Responsible for protein synthesis; found free or on the endoplasmic reticulum (ER).
- Endoplasmic Reticulum (ER):
  - Rough ER: Ribosome-studded, involved in protein synthesis.
  - Smooth ER: Functions in lipid synthesis and drug detoxification.
- Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for transport.
- Lysosomes: Digest cellular waste and macromolecules through enzymatic action.
- Chloroplasts: Present in plant cells, serve as the site for photosynthesis.

Fluid Mosaic Model:
- Describes the cell membrane as a dynamic structure with proteins dispersed in a fluid lipid layer.
Transport Mechanisms:
- Passive Transport: Movement of molecules without energy (e.g., diffusion and osmosis).
- Active Transport: Requires energy to move molecules against their concentration gradient (e.g., sodium-potassium pump).

Mitosis:
- Results in two identical daughter cells; crucial for organism growth and tissue repair.
- Involves phases: Prophase, Metaphase, Anaphase, Telophase.
Meiosis:
- Produces gametes (sperm and eggs) with half the chromosome count; critical for sexual reproduction.
- Comprises two halves of division: Meiosis I and Meiosis II.

Signal Transduction:
- Mechanism for cellular response to external signals via receptors and signaling pathways.
Types of Signaling:
- Autocrine: Cell signals itself, regulating its own functions.
- Paracrine: Cell signals nearby cells, facilitating local communication.
- Endocrine: Hormonal signals released into the bloodstream, affecting distant target cells.

Catabolism:
- Involves the breakdown of complex molecules to release energy.
Anabolism:
- Encompasses the synthesis of complex molecules from simpler ones, requiring energy input.

Cells can specialize into distinct types to carry out specific roles, influenced by genetics and environmental factors.

Types:
- Embryonic Stem Cells: Pluripotent, capable of differentiating into any cell type.
- Adult Stem Cells: Multipotent, restricted to specific cell types.
Possess potential for applications in regenerative medicine and scientific research.

Cells adapt to environmental changes through mechanisms such as:
- Hypertrophy: Increase in cell size.
- Hyperplasia: Increase in cell number.
- Atrophy: Decrease in cell size.