The Cell: Structure and Function (Anatomy & Physiology Study Notes)

The Cell

Basic Processes of Cells

Cells are the fundamental units of life, carrying out essential processes to maintain homeostasis and support the functions of the body.

• Metabolism: The sum of all chemical reactions in a cell, including anabolic (building up), catabolic (breaking down), and oxidation-reduction reactions.

• Substance Transport: Movement of compounds into, out of, or within the cell.

• Communication: Cells communicate with themselves, their environment, and other cells.

• Reproduction: Many cells undergo cell division to reproduce.

Overview of Cell Structure

Main Components of Animal Cells

Animal cells have three primary components, each with specialized functions:

• Plasma Membrane: The outer boundary of the cell.

• Cytoplasm: The region between the plasma membrane and the nucleus, containing:

  • Cytosol: The intracellular fluid.

  • Organelles: Specialized structures performing specific functions.

  • Cytoskeleton: A network of protein filaments providing structural support.

• Nucleus: The control center of the cell, containing genetic material.

Functions of the Plasma Membrane

The plasma membrane is a dynamic structure that:

• Physically isolates the cell from its surroundings, providing a barrier.

• Provides structural support and communicates with other cells.

• Regulates transport into and out of the cell.

• Identifies the cell to other cells.

It also defines and regulates fluid compartments:

• Intracellular Space: Contains intracellular fluid (cytosol).

• Extracellular Space: Contains extracellular fluid (ECF).

Components of the Cytoplasm

• Cytosol (Intracellular Fluid, ICF): A watery gel with proteins, dissolved solutes, and various forms of RNA. Some cells contain inclusions (storage bodies). The cytosol is the site of many critical cellular processes.

• Organelles: Molecular machines that perform and compartmentalize specific cellular functions (e.g., mitochondria, endoplasmic reticulum).

• Cytoskeleton: A network of protein filaments that supports the cell, maintains its shape, holds organelles in place, and provides transportation for substances within the cell.

The Nucleus

The nucleus is present in most cells and is surrounded by a double membrane called the nuclear envelope. It contains most of the cell's deoxyribonucleic acid (DNA) and is the site for the production of ribonucleic acid (RNA). DNA and RNA control cellular functions by coding for and creating proteins.

Cell Size and Diversity

Cells vary greatly in size and shape, allowing them to perform specialized functions. This diversity is essential for the complex activities of multicellular organisms.

Key Terms

• Metabolism: All chemical reactions in a cell.

• Cytosol: The fluid portion of the cytoplasm.

• Organelles: Specialized structures within the cell.

• Cytoskeleton: Protein network for support and movement.

• Nucleus: Organelle containing genetic material.

• Plasma Membrane: Cell boundary regulating entry and exit.

Example: Muscle cells contain many mitochondria to meet high energy demands, while red blood cells lack a nucleus to maximize space for oxygen transport.