Human Biology
Cells and Tissues
Cells and Tissues: Cell Structures
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Cells and Tissues: Cell Structures
Overview of Cells
- A cell is the smallest unit of life.
- Cells are the basic building blocks from which all living organisms are formed.
- There are two broad categories of cells: prokaryotic (bacteria and archaea) and eukaryotic (plants, animals, fungi, and protists).
Cell Structures and Functions
- The nucleus controls cell activity and contains DNA, which carries genetic information.
- Mitochondria provide the cell with energy through respiration.
- The cytoplasm is a gel-like substance where most of the cell's activities occur.
- The membrane-bound organelles carry out specific functions within the cell.
- The cell membrane, also known as the plasma membrane, controls the passage of substances in and out of the cell.
Eukaryotic and Prokaryotic Cells
- Eukaryotic cells are typically more complex and include organelles such as the nucleus and mitochondria.
- Prokaryotic cells are generally simpler and smaller than eukaryotic cells, lacking a nucleus and most organelles.
- Bacterial cells are prokaryotic cells. They have a cell wall, cell membrane, cytoplasm and plasmids, but no nucleus.
Plant Cell Structures
- Plant cells have a cell wall made of cellulose, which provides support and maintains the shape.
- They contain chloroplasts, which are used in photosynthesis to produce food for the plant.
- The vacuole stores water and other substances in plant cells.
Animal Cell Structures
- Animal cells do not have a cell wall or chloroplasts but contain other structures including the mitochondria and nucleus.
- The lysosomes in an animal cell contain enzymes for digestion.
Tissue Structures
- A tissue is a group of similar cells that work together to perform a specific function.
- Examples of tissues include muscle tissue, connective tissue, and neural tissue.
The Role of the Cell
- Cells combine to form tissues, tissues combine to form organs, and organs combine to form organ systems.
- Each specific type of cell has a specific role in the functioning of the human body.
- Faults or damage in cell structure can lead to diseases and disorders.
