Cell Membrane and Organelles

Definition of Osmosis: Diffusion of water across a cell's plasma membrane.
Direction of Osmosis: Determined by the concentration of the surrounding solution.
- Isotonic Solution:
- Example: Normal blood
- Characteristics: Balanced intake and output of water; cell functions correctly.
- Hypotonic Solution:
- Definition: Higher concentration of water outside the cell than inside.
- Effect on Cell: Cell swells as water flows in; can lead to bursting (lysis).
- Hypertonic Solution:
- Definition: Higher concentration of water inside the cell than outside.
- Effect on Cell: Water flows out, causing the cell to shrink (crenation).

Definition of Organelles: Specialized subunits within the cytoplasm of animal cells, each with a specific function related to cellular growth, maintenance, and reproduction.
Common Types of Organelles:
- Mitochondria: Energy production via cellular respiration.
- Lysosomes: Contain digestive enzymes for breaking down waste and cellular debris.
- Ribosomes: Protein synthesis.
- Centrosomes: Involved in cell division and organization of microtubules.
- Golgi Complex: Modifying, sorting, and packaging of proteins for secretion.

Definition of Cytoplasm: The gel-like substance that fills the cell, found between the nucleus and plasma membrane.
Components of Cytoplasm:
- Organelles: Specialized structures performing various functions.
- Cytosol: Fluid portion of the cytoplasm, primarily water containing dissolved ions, glucose, amino acids, fatty acids, and proteins.

Structure of Lysosomes: Membrane-bound organelles containing digestive enzymes, with a single membrane that protects the cytoplasm from the low pH and hydrolytic enzymes within.
Functions of Lysosomes:
- Digest food and pathogens.
- Break down and recycle worn-out cellular structures through a process called autophagy.
- Autophagy Process:
  - A lysosome engulfs an organelle.
  - Digestive enzymes break it down.
  - Recycled components are deposited into the cytosol for reuse.