Cell Structure and Function
This section delves into cell theory, membrane structure, and the differences between prokaryotic and eukaryotic cells.
The cell theory, a fundamental principle in biology, states that:
- All living things are composed of cells
- The cell is the basic unit of structure and function in living organisms
- New cells arise only from existing cells
Highlight: Understanding cell theory is crucial for grasping the organization of life at its most basic level.
The cell membrane, also known as the plasma membrane, is described as a selectively permeable phospholipid bilayer. This structure allows the cell to control what enters and exits.
Vocabulary: Selective permeability refers to the membrane's ability to allow certain substances to pass through while blocking others.
The guide provides a comprehensive comparison of prokaryotic and eukaryotic cells:
- Prokaryotes (e.g., bacteria) lack a nucleus and have simpler cellular organization
- Eukaryotes have a nucleus and more complex cellular structures, including various organelles
Example: A bacterial cell (prokaryote) has a single circular chromosome in the cytoplasm, while a human cell (eukaryote) has multiple linear chromosomes enclosed within a nuclear membrane.
The document includes detailed diagrams of both prokaryotic and eukaryotic cells, labeling key structures such as the cell wall, ribosomes, and various organelles.
Definition: Organelles are specialized structures within eukaryotic cells that perform specific functions, such as mitochondria for energy production and the Golgi apparatus for protein processing.
The concepts of diffusion and osmosis are introduced as mechanisms for cellular transport:
- Diffusion: The movement of molecules from areas of high concentration to low concentration
- Osmosis: The diffusion of water across a selectively permeable membrane
Highlight: Understanding diffusion and osmosis is essential for explaining how cells maintain homeostasis and interact with their environment.
