Cell Biology Study Notes

Cell Theory:
- All living organisms are composed of cells.
- Cells are the basic unit of life.
- All cells arise from pre-existing cells.
Types of Cells:
- Prokaryotic:
  - Lack a nucleus.
  - Smaller and simpler (e.g., bacteria).
- Eukaryotic:
  - Contain a nucleus and organelles.
  - Larger and more complex (e.g., plant and animal cells).

Nucleus:
- Contains genetic material (DNA).
- Controls cell activities.
Mitochondria:
- Powerhouse of the cell.
- Produce ATP through cellular respiration.
Ribosomes:
- Site of protein synthesis.
- Can be free-floating or attached 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 use within the cell.
Lysosomes:
- Contain digestive enzymes to break down waste and cellular debris.
Chloroplasts (in plant cells):
- Site of photosynthesis.
- Contain chlorophyll.
Cell Membrane:
- Semi-permeable barrier.
- Regulates the movement of substances in and out of the cell.

Mitosis:
- Process of cell division that results in two identical daughter cells.
- Stages: Prophase, Metaphase, Anaphase, Telophase.
Meiosis:
- Specialized form of cell division for producing gametes (sperm and egg).
- Results in four non-identical daughter cells with half the chromosome number.

Anabolism:
- Constructive processes where small molecules combine to form larger ones (e.g., protein synthesis).
Catabolism:
- Deconstructive processes breaking down larger molecules into smaller ones (e.g., digestion).

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

Signal Transduction:
- Process by which a cell responds to external signals.
- Involves receptors, second messengers, and effectors.

Differentiation:
- Process by which stem cells develop into specialized cell types.
- Essential for multicellular organisms to perform various functions.

Programmed Cell Death:
- Controlled process for eliminating damaged or unnecessary cells.
- Plays a crucial role in development and homeostasis.

Cell Theory: Fundamental principle that all living organisms are made of cells, which function as the basic unit of life, and all cells originate from pre-existing cells.
Types of Cells:
- Prokaryotic: Simpler organisms without a nucleus; typically smaller and include bacteria.
- Eukaryotic: More complex organisms with a nucleus and organelles; examples include plant and animal cells.

Nucleus: Houses DNA, directing cell activities and heredity.
Mitochondria: Known as the cell’s powerhouse; generates ATP through cellular respiration, vital for energy.
Ribosomes: Protein synthesis takes place here; they can be found free in the cytoplasm or bound to the endoplasmic reticulum.
Endoplasmic Reticulum (ER):
- Rough ER: Studded with ribosomes; primarily responsible for protein synthesis.
- Smooth ER: Lacks ribosomes; involved in lipid synthesis and detoxification processes.
Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for distribution or use within the cell.
Lysosomes: Contain enzymes for digestion; crucial for breaking down waste and cellular debris.
Chloroplasts: Unique to plant cells; site of photosynthesis, containing chlorophyll for capturing light energy.
Cell Membrane: Semi-permeable, selectively regulating the entry and exit of substances in and out of the cell.

Mitosis: A type of cell division producing two genetically identical daughter cells, consisting of phases: Prophase, Metaphase, Anaphase, and Telophase.
Meiosis: Specialized division producing gametes (sperm and egg); results in four genetically diverse daughter cells with half the original chromosome number.

Anabolism: Biosynthetic pathways where small molecules join to form larger, complex molecules, such as proteins.
Catabolism: Degradative pathways breaking down larger molecules into smaller units, playing a key role in digestion.

Passive Transport: Movement of substances across cell membranes without the expenditure of energy; includes processes like diffusion and osmosis.
Active Transport: Energy-requiring process that moves substances against their concentration gradient, exemplified by the sodium-potassium pump.

Signal Transduction: Mechanism enabling cells to respond to external stimuli through a series of molecular interactions involving receptors, second messengers, and effectors.

Differentiation: The process whereby stem cells develop into specialized cell types, essential for multicellular organisms to execute diverse functions.