The document discusses cell size and how diffusion relates to it. The largest cell is an unfertilized ostrich egg at 120mm, while the smallest is a Mycoplasma bacteria at 0.0001mm. Diffusion is the movement of molecules from high to low concentration areas without energy. All nutrients enter and wastes exit cells by diffusion, with steeper gradients allowing faster movement. Smaller cell sizes allow for more efficient diffusion, as materials have shorter distances to travel across the cell.

1. Largest cell in human body Egg cell 0.1mm Smallest cell in human body Sperm cell 0.06mm Smallest cell in nature Mycoplasma bacteria 0.0001mm Largest cell in nature Unfertilized ostrich egg 120mm

2. Why are cells so small? What limits cell size?

3. Diffusion Movement of molecules from areas of high concentration to areas of low concentration across a membrane Movement continues until equilibrium is reached! Then there is no more NET movement of molecules.

4. Diffusion occurs as molecules move down a concentration gradient. No energy is needed for this to happen. *The steeper the concentration gradient, the faster the movement of molecules.

5. Why is this so important? -All important nutrients enter the cell by diffusion. -All wastes exit the cell by diffusion. EXAMPLE Oxygen diffuses from lungs into blood arteries

6. How does this relate to cell size? CELL SIZE LAB Homework must be complete to perform the lab. You will receive a zero for the lab if homework is not complete. Homework: Prelab assignment: 1. read Lab 6 Design a Cell Introduction 2. complete pre-lab questions 3. design two cells