Cell Biology Study Notes

Prokaryotic Cells:
- Simple structure, no nucleus.
- Examples: Bacteria and Archaea.
Eukaryotic Cells:
- Complex structure with a nucleus.
- Examples: Plant cells, animal cells, fungal cells, and protists.

Plasma Membrane:
- Semi-permeable barrier that controls the movement of substances in and out of the cell.
Nucleus:
- Contains genetic material (DNA).
- Site of transcription.
Cytoplasm:
- Gel-like substance where organelles are suspended.
- Site of metabolic processes.
Organelles:
- Mitochondria: Powerhouse of the cell, site of ATP production.
- Endoplasmic Reticulum (ER):
  - Rough ER: Studded with ribosomes; synthesizes proteins.
  - Smooth ER: Synthesizes lipids and detoxifies.
- Golgi Apparatus: Modifies, sorts and packages proteins and lipids.
- Lysosomes: Contain enzymes to digest waste materials.
- Ribosomes: Protein synthesis (found free in cytoplasm or on Rough ER).
- Chloroplasts: (Plant cells only) Site of photosynthesis.

Mitosis:
- Process of cell division resulting in two identical daughter cells.
- Stages: Prophase, Metaphase, Anaphase, and Telophase.
Meiosis:
- Process of cell division that produces gametes (sperm and eggs).
- Involves two divisions leading to four non-identical cells.

Metabolism: Sum of all biochemical reactions in the cell (including catabolism and anabolism).
Energy Production: ATP generated from cellular respiration, primarily in mitochondria.
Signal Transduction: Communication within and between cells using signaling molecules.

Cells communicate with each other via chemical signals (hormones, neurotransmitters).
Types of signaling:
- Autocrine (self-signaling)
- Paracrine (signal to nearby cells)
- Endocrine (hormones via the bloodstream)

Passive Transport: Movement without energy input (e.g., diffusion, osmosis).
Active Transport: Movement requiring energy (ATP) to transport molecules against their concentration gradient.

Cells are the fundamental building blocks of all living organisms.
All living things, from single-celled bacteria to complex multicellular animals, are made up of cells.

Prokaryotic cells are simple cells lacking a nucleus and other membrane-bound organelles.
- Examples include bacteria and archaea.
Eukaryotic cells are more complex, possessing a nucleus and other membrane-bound organelles.
- Examples include plant cells, animal cells, fungal cells, and protists.

Plasma Membrane:
- A selectively permeable barrier that regulates the movement of substances into and out of the cell.
- Acts as a protective layer and maintains cellular homeostasis.
Nucleus:
- The control center of the cell, containing the genetic material (DNA).
- Responsible for transcription, the process of copying DNA into RNA.
Cytoplasm:
- A gel-like substance filling the cell, suspending organelles and providing a medium for cellular processes.
- Site of various metabolic reactions.
Organelles:
- Mitochondria: Powerhouse of the cell, responsible for ATP production through cellular respiration.
- Endoplasmic Reticulum (ER):
  - Rough ER: Studded with ribosomes, involved in protein synthesis.
  - Smooth ER: Synthesizes lipids and detoxifies harmful substances.
- Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.
- Lysosomes: Contain enzymes that break down waste materials, cellular debris, and engulfed pathogens.
- Ribosomes: Sites of protein synthesis, found free in the cytoplasm or attached to the Rough ER.
- Chloroplasts: Found only in plant cells, sites of photosynthesis, the process of converting light energy into chemical energy.

Mitosis:
- A process of cell division that results in two genetically identical daughter cells.
- Essential for growth, repair, and development.
- Occurs in four stages: prophase, metaphase, anaphase, and telophase.
Meiosis:
- A cell division process that produces gametes (sperm and eggs) with half the number of chromosomes as the parent cell.
- Involves two divisions, resulting in four non-identical cells.
- Crucial for sexual reproduction and genetic diversity.

Metabolism:
- The sum of all chemical reactions that occur within a cell.
- Includes catabolism, the breakdown of complex molecules into simpler ones, and anabolism, the synthesis of complex molecules from simpler ones.
Energy Production:
- Cells obtain energy primarily through cellular respiration, which occurs in mitochondria.
- The process converts glucose into ATP, the cell's energy currency.
Signal Transduction:
- Cells communicate with each other through signaling molecules, such as hormones and neurotransmitters.
- This communication allows cells to coordinate activities and respond to changes in their environment.

Autocrine signaling: Cells signal themselves.
Paracrine signaling: Cells signal nearby cells.
Endocrine signaling: Cells signal distant cells via hormones released into the bloodstream.

Passive transport: Movement of substances across the cell membrane without requiring energy input.
- Examples include diffusion (movement from high to low concentration) and osmosis (movement of water across a semi-permeable membrane).
Active Transport: Movement of substances across the cell membrane requiring energy (ATP).
- This allows cells to transport substances against their concentration gradients.

All living things are composed of cells.
The cell is the basic unit of life.
All cells arise from pre-existing cells.
- This principle highlights the continuous line of descent from the first cells to all living organisms today.