BackThe Cell: Structure and Function – A Survey of Cellular Components
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Chapter 4: The Cell
Introduction to Cellular Structure and Function
This chapter provides an overview of the structure and function of major cellular components. Understanding the cell is fundamental to biology, as all living organisms are composed of cells, which are the basic units of life. The structure of cellular components is determined by the macromolecules discussed in previous chapters, and these components work together to perform various functions necessary for life.
Key Point: Cellular components are constructed from macromolecules (proteins, lipids, carbohydrates, nucleic acids).
Key Point: These macromolecules form composite structures that enable diverse cellular functions.
Example: The plasma membrane is a composite structure made primarily of phospholipids and proteins, providing both a barrier and a means of communication with the environment.
Overview: The Fundamental Units of Life
Definition and Diversity of Cells
The cell is the indivisible unit of life. While all cells share certain features, they can vary greatly in size, shape, and function. This diversity is often related to the specific roles cells play in an organism.
Key Point: All living things are made of cells, but cell types can be very different depending on their function.
Key Point: Despite differences, all cells are related by their descent from earlier cells (common ancestry).
Example: Muscle cells are specialized for contraction, while nerve cells are specialized for signal transmission.
Cell Types: Prokaryotic vs. Eukaryotic
Cells are classified into two main types based on their structural characteristics: prokaryotic and eukaryotic cells.
Prokaryotic Cells: Found in the domains Bacteria and Archaea. They lack a nucleus and membrane-bound organelles.
Eukaryotic Cells: Found in protists, fungi, plants, and animals. They have a nucleus and various membrane-bound organelles.
Key Point: Both cell types have a plasma membrane, cytosol, chromosomes (DNA), and ribosomes.
Example: Bacterial cells are prokaryotic, while plant and animal cells are eukaryotic.
Cell Structure and Function Relationship
The structure of a cell is closely related to its function. For example, cells involved in absorption (like intestinal cells) have structures that increase surface area, while cells involved in movement (like sperm cells) have flagella.
Key Point: Cell morphology (shape and structure) is adapted to the cell's specific function.
Example: Red blood cells are biconcave to maximize surface area for gas exchange.
Additional info:
Cells are the smallest units capable of independent life and reproduction.
All cells arise from pre-existing cells by cell division.
