Cellular Organelles and Transport Mechanisms

This page continues the exploration of eukaryotic cell organelles and introduces various cellular transport mechanisms, which are crucial concepts in AP Biology Unit 2: cell structure and function.

The page begins by detailing the structure and function of several important organelles:

1. Golgi Complex: Modifies, processes, and sorts proteins and lipids. It also produces vesicles that carry products out of the cell.

2. Mitochondria: Often referred to as the "powerhouse" of the cell, these organelles convert energy into organic molecules. The inner membrane of mitochondria forms cristae, which increase the surface area to volume ratio, enhancing the efficiency of ATP production.

3. Lysosomes: Contain digestive enzymes that break down cellular waste, worn-out organelles, and engulfed particles. They also play a role in apoptosis (programmed cell death).

4. Centrioles: Produce microtubules during cell division.

5. Vacuoles: Fluid-filled sacs that store food and other substances.

6. Peroxisomes: Detoxify substances and produce hydrogen peroxide as a byproduct. They are particularly common in liver and kidney cells.

7. Cell Wall: Present in plant cells, made of cellulose or chitin.

8. Chloroplasts: Contain chlorophyll and are responsible for photosynthesis in plant cells.

9. Central Vacuole: A large, fluid-filled organelle in plant cells, regulated by turgor pressure.

The page then transitions to discussing cellular transport mechanisms:

• The ability of molecules to move across the cell membrane depends on their size and charge.
• Facilitated transport: Required for hydrophobic molecules to pass through the lipid bilayer. This process uses specialized channels, such as aquaporins for water transport.
• Passive transport: Does not require metabolic input and occurs when substances move down their concentration gradient.
• Osmosis: The movement of water across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration.

Vocabulary: Cristae - The folded inner membrane of mitochondria that increases surface area for ATP production.

Example: Aquaporins are specialized protein channels that facilitate the rapid movement of water molecules across cell membranes.

Definition: Passive transport is the movement of substances across a cell membrane without the expenditure of cellular energy, always occurring down the concentration gradient.

Highlight: The Golgi complex plays a crucial role in modifying, sorting, and packaging proteins and lipids for secretion or use within the cell.

Quote: "Mitochondria: The 'power house' that converts energy into organic molecules."