Microscopy Techniques and Cell Size

This section delves deeper into microscopy techniques and the significance of cell size in biological processes, providing essential information for IB Biology notes and summary notes.

A detailed comparison of light microscopes, transmission electron microscopes (TEM), and scanning electron microscopes (SEM) is presented in a table format. This comparison includes factors such as maximum resolution, magnification, material preparation, and staining techniques.

Highlight: Electron microscopes (TEM and SEM) offer significantly higher magnification and resolution compared to light microscopes, but require special preparation of specimens.

The concept of magnification is explained, along with the formula for calculating it:

Magnification = Image Size / Actual Size

Example: If an image of a cell measures 5 cm and the actual cell size is 50 μm, the magnification would be 1000x.

The text then discusses the relationship between cell size and cellular functions. It explains how the volume of a cell determines its metabolic activity, while the surface area affects the rate of material exchange with the environment.

Definition: The surface area to volume ratio is crucial in determining the efficiency of cellular processes and the maximum size a cell can reach before division becomes necessary.

The transition from unicellular to multicellular organisms is explained as a result of cells reaching their expansion limit and dividing. This leads to a discussion of cell differentiation in multicellular organisms.

Vocabulary: Differentiation is the process by which less specialized cells mature to have distinct functions and forms.

Introduction to Cells

This section provides a comprehensive overview of the fundamental concepts in IB Biology Unit 1.1 Cell Theory. It covers the core principles of cell theory, unicellular organisms, and the importance of cell size in biological functions.

The cell theory is presented with its three main principles:

1. The cell is the smallest unit of life
2. All living organisms consist of one or more cells
3. All new cells arise from already existing cells

Highlight: Pasteur's experiments proved that all new cells arise from pre-existing cells, supporting the third principle of cell theory.

The text also discusses exceptions to the cell theory, such as hyphae in fungi and skeletal muscle cells.

Example: Mature blood cells do not contain nuclei, making them an exception to the typical cell structure.

Unicellular organisms are defined as those capable of carrying out all life functions within a single cell. The section then delves into the importance of cell size and magnification in biology, explaining why most cells are not visible to the naked eye and require microscopes for observation.

Vocabulary: Resolving power is the ability to separate objects better, allowing for more detailed observation.

The text compares different types of microscopes, highlighting the advantages of electron microscopes over light microscopes in terms of resolution and magnification.

Definition: TEM (transmission electron microscope) produces clear images of thin sections, while SEM (scanning electron microscope) provides detailed images of external appearances.