Concentration reactants and catalysts

Cell Size and Reactant Concentration

Cells must ensure sufficient reactant concentrations for reactions. If a cell is large, it needs enough reactants (e.g., enzymes like maltase for maltose) to ensure collisions and reactions occur.
Example: If a cell is large and contains a lot of maltose, it needs a large amount of maltase to ensure contact and reaction.
The more protein (e.g., maltase or catalase) needed to fill the cell, the bigger the cell, which makes it necessary to create more of the protein to ensure reactants come into contact.
Catalase breaks down hydrogen peroxide inside cells.
If a cell needs to make enough catalase to be present throughout the entire cell to quickly break down hydrogen peroxide, it would need to produce a significant amount of catalase.
The need to produce a lot of a certain enzyme can become rate limiting.

To overcome the limitations of cell size, cells use organelles for specialized activities. This allows high concentrations of proteins in specific locations.
Example: Catalase is mainly needed in peroxisomes, where hydrogen peroxide is found. Thus, the cell only needs to produce high concentrations of catalase in peroxisomes, reducing the total amount of catalase needed.
This compartmentalization enables cells to be larger without needing to produce as many proteins.
Proteins like catalase can be transported via vesicles and motor proteins directly to organelles like peroxisomes.

Cells share similarities in function. These include:
- Using sugar (particularly glucose) as a fuel source.
- Undergoing transcription and translation at some point in their life cycle (though mature red blood cells lose organelles and don't perform these processes).

Cells differ in function based on specialization.
- Some cells in the pancreas produce digestive enzymes, while others in the small intestine do the same. However, certain digestive enzymes are exclusively made by the pancreas.
- Pancreatic cells are uniquely responsible for making insulin.
- Muscle cells (skeletal, cardiac, smooth) are the only cells capable of contraction. No other cell type possesses this specialized function.

Cells share structural characteristics:
- All cells have organelles at some stage (except mature red blood cells).
- All cells have a cell membrane (even red blood cells).
Cells can vary in shape:
- Epithelial cells can be squamous, cuboidal, or columnar.
- Heart muscle cells are long rectangles.
- Pancreatic cells are round.
- Neurons have unique, complex structures.
The course will focus on the common characteristics of most cells, but will also discuss cell specialization and examples.