Cell Biology Overview

Definition: Study of cells, their physiological properties, structures, organelles, interactions, and behavior.
Cell Theory:
1. All living organisms are composed of one or more cells.
2. The cell is the basic unit of life.
3. All cells arise from pre-existing cells.
Types of Cells:
- Prokaryotic Cells: Simple, no nucleus (e.g., bacteria).
- Eukaryotic Cells: Complex, with a nucleus (e.g., animal and plant cells).
Cell Organelles:
- Nucleus: Contains genetic material (DNA).
- Mitochondria: Powerhouse, produces ATP through respiration.
- Ribosomes: Site of protein synthesis.
- 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.
- Lysosomes: Contains digestive enzymes to break down waste.
- Chloroplasts (in plants): Site of photosynthesis.
Cell Division:
- Mitosis: Somatic cell division for growth and repair.
- Meiosis: Produces gametes for sexual reproduction.

Structure:
- Composed of a phospholipid bilayer with embedded proteins.
- Fluid mosaic model: Membrane is flexible and proteins can move within the layer.
Functions:
- Barrier: Separates the interior of the cell from the external environment.
- Transport: Regulates the movement of substances in and out of the cell.
  - Passive Transport: Movement without energy (e.g., diffusion, osmosis).
  - Active Transport: Requires energy (e.g., sodium-potassium pump).
- Communication: Contains receptors for signaling molecules (hormones).
- Cell Recognition: Glycoproteins and glycolipids help cells recognize each other.
Permeability:
- Semi-permeable: Allows certain molecules to pass while blocking others (e.g., small nonpolar molecules pass easily).
Membrane Proteins:
- Integral Proteins: Span the membrane, involved in transport and communication.
- Peripheral Proteins: Attached to the membrane surface, play roles in signaling and maintaining cell shape.

Studies the physiological properties, structures, organelles, interactions, and behavior of cells.
Cell Theory posits that:
- All living organisms consist of one or more cells.
- The cell is the fundamental unit of life.
- New cells arise only from pre-existing cells.

Prokaryotic Cells:
- Simple structure, lacking a nucleus.
- Example: Bacteria.
Eukaryotic Cells:
- More complex structure, containing a nucleus.
- Examples: Animal and plant cells.

Nucleus:
- Houses genetic material (DNA).
Mitochondria:
- Known as the powerhouse of the cell; responsible for ATP production through respiration.
Ribosomes:
- Sites where protein synthesis occurs.
Endoplasmic Reticulum (ER):
- Rough ER: Studded with ribosomes, primarily synthesizes proteins.
- Smooth ER: Lacks ribosomes; involved in lipid synthesis and detoxification processes.
Golgi Apparatus:
- Modifies, sorts, and packages proteins and lipids for secretion or use within the cell.
Lysosomes:
- Contain digestive enzymes for breaking down waste materials.
Chloroplasts (found in plants):
- Sites of photosynthesis.

Structure:
- Composed of a phospholipid bilayer with embedded proteins.
- Described by the fluid mosaic model, highlighting flexibility and protein mobility.

Barrier:
- Distinguishes the internal environment of the cell from the external surroundings.
Transport:
- Regulates the ingress and egress of substances.
Passive Transport:
- Movement of molecules without energy (e.g., diffusion, osmosis).
Active Transport:
- Requires energy input for substance movement (e.g., sodium-potassium pump).
Communication:
- Contains receptors for signaling molecules such as hormones.
Cell Recognition:
- Glycoproteins and glycolipids facilitate inter-cell recognition.

Semi-permeable:
- Allows select molecules to permeate while restricting others, notably enabling small nonpolar molecules to pass easily.

Integral Proteins:
- Span the membrane; critical for transport and communication functions.
Peripheral Proteins:
- Attach to the membrane's surface; involved in signaling and structural support of the cell.