Cell Biology Overview

Study Notes

Cell Biology

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.

Cell Membrane

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.

Cell Biology

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.

Types of Cells

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

Cell Organelles

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.

Cell Division

Mitosis:
- Type of somatic cell division aimed at growth and tissue repair.
Meiosis:
- Process producing gametes for sexual reproduction.

Cell Membrane

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

Functions of the Cell Membrane

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.

Permeability

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

Membrane Proteins

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.

Description

Explore the fascinating world of cell biology, covering the definition and significance of cells, cell theory, and the different types of cells. Delve into the various organelles and their unique functions within prokaryotic and eukaryotic cells.