Unit 1 Cell Biology - Transport of substances

What is diffusion?

The net movement of particles from an area of higher concentration to an area of lower concentration.

What is osmosis?

The net movement of water from an dilute solution (more water) to a concentrated solution (less water)

What is active transport?

The net movement of molecules from a more dilute (more water less molecules )to more concentrated solution (the opposite), against (up) the concentration gradient.

What factors can affect rate of diffusion?

• Temperature

• Steepness of concentration gradient

• Surface Area

What is SA:V and how is it used?

SA:V is surface area to volume ratio and is used in adaptations as the higher SA:V or the higher surface area there is whilst not volume, is more efficient at exchanging substances

What factors increase the effectiveness of a gas exchange surface?

• Large surface area

• Short diffusion path

• Efficient blood supply

• Ventilation (in animals

What is an isotonic solution?

An isotonic solution is a solution that has the same concentration of solutes and water as the inside of a cell.

What is a hypertonic solution?

A hypertonic solution is a solution that has a higher concentration of solutes and a lower concentration of water than the inside of a cell.

What is a hypotonic solution?

A hypotonic solution is a solution with a lower concentration of solutes (like salt or sugar) and a higher concentration of water than the inside of a cell.

How is the small intestine adapted for exchange of materials?

• Villi help with a higher SA:V ratio

• Plenty of capillaries form a steep concentration gradient

How are fish gills adapted for exchange of materials?

• Gill filaments and lamellae hugely increase surface area

• Water flows over the gills opposite to blood flow so blood meets water with a higher oxygen concentration, meaning there is a steeper gradient

How are root hair cells adapted for exchange of materials?

• Large surface area due to shape

• Thin cell wall = shorter diffusion distance

• Larger permanent vacuole means a steeper concentration gradient

• Many mitochondria help supply energy for active transport

How are leaf cells adapted for exchange of materials?

• Leaves are broad and flat so more area to absorb light and gases

• Large air spaces let gases diffuse in and out much more easily

• Stomata control when gases diffuse in and out by opening and closing when turgid/flaccid controlled by guard cells

How do plant leaves and stems remain rigid?

Turgor pressure - water moves in by osmosis, causing the vacuole to swell and the cytoplasm to press against the cell wall.

What would happen if a plant cell was put in a very hypertonic solution?

Water moves out of the cell by osmosis and the vacuole and cytoplasm decrease in size. The cell membrane may pull away from the cell wall, causing the cell to become plasmolysed.

What would happen if an animal cell was put in a very hypertonic solution?

Water moves out of the cell, causing it to shrivel up.

What would happen if an animal cell was put in a very hypotonic solution?

Water moves into the cell, causing it to burst.

What would happen if a plant cell was put in a very hypotonic solution?

When a plant cell is placed in a hypotonic solution water moves into the cell by osmosis, causing it to swell and become flaccid.