Question

Pick a structure of the cell, and describe its structure and function, OR discuss a phase of cellular transportation.

Answer 1

Types of Cellular Transport - Active and passive transport

Passive Transport

• cell doesn’t use energy
• molecules move randomly
• Molecules spread out from an area of high concentration to an area of l ow concentration

Types

1. Diffusion

1. random movement of particles from an area of high concentration to an area of low concentration .
2. Diffusion continues until all molecules are evenly spaced ( equilibrium is reached)
3. Requires no energy

2.Facilitated Diffusion

1. diffusion of specific particles through transport proteins found in the membrane
2. Transport Proteins are specific – they “select” only certain molecules to cross the membrane Transports larger or charged molecules

3.Osmosis

1. diffusion of water through a selectively permeable membrane
2. Water moves from high to low concentrations
3. Water moves freely through pores.

Effects of Osmosis on Life

• Osmosis - diffusion of water through a selectively permeable membrane
• Water is so small and there is so much of it, the cell can’t control it’s movement through the cell membrane.

Hypotonic Solution :

• The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water)
• So Water moves from the solution to inside the cell: Cell Swells and bursts open ( cytolysis )

Hypertonic Solution :

• The solution has a higher concentration of solutes and a lower concentration of water than inside the cell . (High solute; Low water)
• Result : Water moves from inside the cell into the solution: Cell shrinks ( Plasmolysis )

Isotonic Solution :

• The concentration of solutes in the solution is equal to the concentration of solutes inside the cell.
• Result : Water moves equally in both directions and the cell remains same size! (Dynamic Equilibrium)

Active Transport

• cell uses energy
• actively moves molecules to where they are needed
• Movement from an area of low concentration to an area of high concentration

Types

1. Protein Pumps

1. Protein Pumps -transport proteins that require energy to do work
2. Example: Sodium / Potassium Pumps are important in nerve responses
3. Endocytosis

2. Endocytosis :

1. taking bulky material into a cell
2. Uses energy
3. Cell membrane in-folds around food particle
4. “ cell eating ”
5. forms food vacuole & digests food
6. This is how white blood cells eat bacteria

3.Exocytosis

1. Forces material out of cell in bulk
2. membrane surrounding the material fuses with cell membrane
3. Cell changes shape – requires energy
4. Eg: Hormones or wastes released from cell