cell transport question

Calculate the surface area to volume ratio (SA/V) of a cube with sides that are 2cm in length

2x2x6=24 2x2x2=8 24/8=3

7. In which cell will nutrients reach all areas in the shortest amount of time: a cell with SA/V of 6:1 or a cell with a SA/V of 2:1?

6:1

Why does active transport require energy?

Active moves SMALL particles in the opposite direction of diffusion, from areas of low density to areas of high density. This is called going against the concentration gradient Transport moves large particles and it takes energy to move particle that size.

4. Are exocytosis and endocytosis examples of active or passive transport? Explain your answer.

Active transport because the cell must use energy to move large particles across the membrane.

Explain why cells are small.

Cells tend to have SA/V because they want a short distance edge to center to take advantage to "free" diffusion moving nutrients everywhere in cell + removing waste.

Most cells are microscopic. Why are chicken eggs so large?

Chicken eggs can be large because nutrients are already in the cell. They do NOT have to import nutrients from envoirment.

3. Explain how endocytosis and exocytosis are different.

Endocytosis Is the process by which a large particle is brought into the cell. Exocytosis is the process which a large particle exits the cell.

What is different about the availability of nutrients to all areas of a cell when cells are shaped like a cube versus when they are shaped like a pancake?

Pancake has a lager SA/V: shorter distance from the edge to the center. Square has larger distance edge to the center. Pancake shaped cell has high SA/v With a short distance from the edge to center, meaning nutrients reach all areas of cell efficiently. Before they were pancake shaped

How do we define SA/V in this class?

Sa/V basically refers to the distance from the edge to center. When distance to center is small SA/V is large. When distance to center is large SA/V is small. Cells want to have a high SA/V so that the distance from the edge of the cell to the center is short and nutrients can get everywhere.

Before the invention of refrigeration, some types of food were preserved by adding large amounts of salt to them. What hypothesis can you offer to explain how the addition of salt can preserve food?

Salt "draws" out water through process of osmosis. Dry cells are NOT favorable habitat for bacteria fungus.

Explain how diffusion and osmosis are different.

The diffusion of water through a semipermeable membrane. The movement of particles from regions of higher density to regions of lower density.