Lab 4: The Cell – Structure and Types

Lab 4: The Cell

Introduction to Cells

Cells are the fundamental units of life, forming the basic structural and functional components of all living organisms. This lab focuses on the observation and comparison of different cell types, their structures, and key organelles.

• Cell Theory: All living things are composed of cells; cells are the basic units of structure and function in organisms; all cells arise from pre-existing cells.

• Microscopy: Cells are typically observed using light or electron microscopes to reveal their internal structures.

Types of Cells

Animal Cells

Animal cells are eukaryotic cells characterized by the absence of a cell wall and the presence of a flexible plasma membrane. They contain various organelles that perform specialized functions.

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

• Plasma Membrane: A selectively permeable barrier that surrounds the cell, regulating the movement of substances in and out.

• Cytoplasm: The jelly-like substance within the cell where organelles are suspended.

• Organelles: Specialized structures such as mitochondria, endoplasmic reticulum, and Golgi apparatus.

• Shape: Animal cells often have irregular or rounded shapes, as seen in the provided microscope image.

Example: The image shows elongated animal cells with visible nuclei stained in red.

Plant Cells

Plant cells are eukaryotic cells distinguished by the presence of a rigid cell wall, large central vacuole, and chloroplasts. These features enable plants to maintain structure and perform photosynthesis.

• Cell Wall: A rigid outer layer composed of cellulose that provides structural support.

• Chloroplasts: Green, circular organelles responsible for photosynthesis, containing the pigment chlorophyll.

• Central Vacuole: A large, fluid-filled organelle that maintains cell turgor and stores nutrients.

• Shape: Plant cells are typically rectangular or box-like due to the rigid cell wall.

Example: The image shows plant cells with numerous green chloroplasts distributed throughout the cytoplasm.

Cellular Organelles

Key Organelles and Their Functions

Both animal and plant cells contain several organelles, each with specific roles essential for cell survival and function.

• Nucleus: Stores genetic information and coordinates cell activities.

• Mitochondria: The site of cellular respiration, producing energy in the form of ATP.

• Endoplasmic Reticulum (ER): Involved in protein and lipid synthesis; rough ER has ribosomes, smooth ER does not.

• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or use within the cell.

• Chloroplasts (plant cells only): Conduct photosynthesis, converting light energy into chemical energy.

• Cell Wall (plant cells only): Provides structural support and protection.

Comparison of Animal and Plant Cells

Structural Differences

The following table summarizes the main differences between animal and plant cells:

Feature	Animal Cell	Plant Cell
Cell Wall	Absent	Present (cellulose)
Chloroplasts	Absent	Present
Shape	Irregular, rounded	Rectangular, box-like
Central Vacuole	Small or absent	Large, central
Nucleus	Present	Present

Microscopy in Cell Biology

Observing Cells

Microscopes are essential tools for studying cell structure. Light microscopes are commonly used in teaching labs to observe stained animal and plant cells, while electron microscopes provide higher resolution images of cellular details.

• Light Microscopy: Allows visualization of cell shape, nucleus, and some organelles.

• Electron Microscopy: Used for detailed study of organelles and cell ultrastructure.

Example: The provided images show stained animal and plant cells under a light microscope, highlighting nuclei and chloroplasts.

Summary

Understanding the structure and function of animal and plant cells is fundamental in biology. Key differences include the presence of cell walls and chloroplasts in plant cells, and the unique organelles found in both cell types. Microscopy enables the observation of these features, providing insight into cellular organization and function.

Additional info: Some content was inferred from standard biology curriculum and typical lab activities, as the original notes were fragmented and partially illegible.