Cell Biology Overview

Prokaryotic Cells
- Lack a nucleus and membrane-bound organelles.
- Smaller and simpler (e.g., bacteria).
- Genetic material (DNA) is circular and located in the nucleoid.
Eukaryotic Cells
- Have a nucleus and membrane-bound organelles.
- Larger and more complex (e.g., plant and animal cells).
- DNA is linear and organized into chromosomes.

Plasma Membrane:
- Semi-permeable barrier that regulates transport in and out of the cell.
Nucleus:
- Contains genetic material (DNA).
- Site of RNA synthesis and ribosome assembly.
Cytoplasm:
- Gel-like substance where cellular processes occur.
- Contains organelles and cytoskeleton.
Organelles:
- Mitochondria: Powerhouse of the cell; site of ATP (energy) production.
- Endoplasmic Reticulum (ER):
  - Rough ER: Studded with ribosomes; synthesizes proteins.
  - Smooth ER: Synthesizes lipids; detoxifies toxins.
- Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or use within cells.
- Lysosomes: Contains enzymes for digestion of waste materials and cellular debris.
- Chloroplasts (in plant cells): Site of photosynthesis; contains chlorophyll.

Cellular Respiration:
- Process of converting glucose and oxygen into ATP, carbon dioxide, and water.
- Occurs in mitochondria.
Photosynthesis (in plants):
- Process of converting sunlight, carbon dioxide, and water into glucose and oxygen.
- Occurs in chloroplasts.
Protein Synthesis:
- Transcription: DNA is transcribed to mRNA in the nucleus.
- Translation: mRNA is translated to protein at ribosomes.

Mitosis:
- Process of cell division resulting in two identical daughter cells.
- Phases: Prophase, Metaphase, Anaphase, Telophase.
Meiosis:
- Process of cell division that produces gametes (sperm and egg).
- Involves two rounds of division and results in four non-identical cells.

Signaling Molecules:
- Hormones, neurotransmitters, and other chemicals that facilitate communication between cells.
Receptors:
- Proteins on cell surfaces that bind to signaling molecules and initiate a response.

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

Prokaryotic Cells:
- Possess no nucleus or membrane-bound organelles.
- Generally smaller and simpler, exemplified by bacteria.
- Circular DNA located in the nucleoid region.
Eukaryotic Cells:
- Contain a nucleus and membrane-bound organelles.
- Larger and more complex, found in plants and animals.
- DNA is linear and arranged in chromosomes.

Plasma Membrane:
- Semi-permeable structure managing substance transport.
Nucleus:
- Houses genetic material (DNA).
- Primary site for RNA synthesis and ribosome assembly.
Cytoplasm:
- Gel-like fluid where cellular activities occur.
- Contains organelles and the cytoskeleton for structure.
Organelles:
- Mitochondria:
  - Known as the cell’s powerhouse; location of ATP production.
- Endoplasmic Reticulum (ER):
  - Rough ER: Contains ribosomes for protein synthesis.
  - Smooth ER: Responsible for lipid synthesis and detoxification.
- Golgi Apparatus:
  - Modifies, sorts, and packages proteins and lipids for cellular use or export.
- Lysosomes:
  - Enzyme-filled structures that digest waste and cellular debris.
- Chloroplasts:
  - Found in plant cells; site of photosynthesis and chlorophyll production.

Cellular Respiration:
- Converts glucose and oxygen into ATP, carbon dioxide, and water.
- Takes place in the mitochondria.
Photosynthesis (in plants):
- Transforms sunlight, carbon dioxide, and water into glucose and oxygen.
- Occurs in chloroplasts.
Protein Synthesis:
- Transcription:
  - DNA is converted to mRNA in the nucleus.
- Translation:
  - mRNA is translated into proteins by ribosomes.

Mitosis:
- Type of cell division yielding two identical daughter cells.
- Progresses through phases: Prophase, Metaphase, Anaphase, Telophase.
Meiosis:
- Specialized cell division for gamete (sperm and egg) production.
- Involves two division rounds, producing four non-identical cells.

Signaling Molecules:
- Includes hormones and neurotransmitters that enable intercellular communication.
Receptors:
- Surface proteins that bind signaling molecules to trigger cellular responses.

Passive Transport:
- Movement of substances across the membrane without energy expenditure (e.g., diffusion, osmosis).
Active Transport:
- Energy-dependent movement of substances against their concentration gradients (e.g., sodium-potassium pump).