Cell Structure and Observation

Cell Discovery

• Antonie van Leeuwenhoek discovered free living cells in pond water in 1674 using a primitive microscope.
• Robert Brown discovered the nucleus in 1831.
• Matthias Jakob Schleiden (1838) and Theodor Schwann (1839) presented the cell theory, stating that all plants and animals are composed of cells and that the cell is the basic unit of life.

Cell Structure

• Every cell has a plasma membrane, nucleus, and cytoplasm.
• The plasma membrane allows or permits the entry and exit of some materials in and out of the cell.
• The nucleus is a double-layered structure that contains chromosomes, which are visible as rod-shaped structures only when the cell is about to divide.
• Chromosomes contain information for inheritance of characters from parents to next generation in the form of DNA molecules.

Cell Organelles

• Endoplasmic reticulum (ER) serves as channels for the transport of materials between various regions of the cytoplasm or between the cytoplasm and the nucleus.
• ER also functions as a cytoplasmic framework providing a surface for some of the biochemical activities of the cell.
• Golgi apparatus consists of stacks of membrane-bound vesicles that function in the storage, modification, and packaging of substances manufactured in the cell.
• Lysosomes, mitochondria, and plastids are other important cell organelles.
• Plastids are found in plant cells and are of two types: chromoplasts and leucoplasts.
• Chromoplasts contain chlorophyll and perform photosynthesis, while leucoplasts are responsible for storage.

Cell Function

• Cells perform certain basic functions that are characteristic of all living forms, such as detoxifying poisons and drugs.
• Cells have a division of labor, meaning different parts of the body perform different functions.
• The shape and size of cells are related to the specific function they perform.