Transport in plants

Aims Recap on osmosis as a

special type of diffusion of water.

Understand the function of xylem and phloem

Understand how water acts against gravity

Know how plants get minerals against concentration gradients.

Transpiration Active transport Xylem Phloem

Remember diffusion???

Osmosis is very similar to diffusion but ONLY talks about the movement of water particles

Osmosis is the diffusion of water molecules from an area of high concentration to an area of low concentration across a partially permeable membrane

http://www.youtube.com/watch?v=0c8acUE9Itw

Watch the video and you must explain why the egg changes using what you understand of osmosis

Write two explanations. One for the corn syrup, the other for pure water.

Watch the egg - starter

Peer marking – 6 marks

In the corn syrup In the pure water

Water moves from the higher concentration in the egg yolk to the lower water concentration in the corn syrup. (1)

Across a partially permeable membrane (1).

The partially permeable membrane has pores that allow the movement of water but not the sugar molecules (1).

Water moves from the higher concentration of water to the lower concentration of water in the egg yolk (1).

Across a partially permeable membrane (1).

Quality of written communication (1)

The cell membrane separates the contents of the cell from the outside

It has tiny holes in it

This allows small molecules to pass through it but not large molecules

It is PARTIALLY PERMEABLE

Osmosis occurs across a semi permeable membrane which has tiny holes in it.

These holes are small enough for water molecules to pass through but larger molecules cannot pass through

Water molecules =Squash molecules =

What is Osmosis?The movement of water from high to low concentration through a partially permeable membrane

What is a partially permeable membrane A membrane that has small holes in it & only lets small water molecules move through it. It

does not let large solute molecules through.

What is the partially permeable membrane in the

cell?

The cell membrane

Osmosis and Plant cells

Flaccid (plasmolysed) Turgid

Wilting plant upright plant

Plasmolysis in onion cells

Turgid onion cells

Osmosis and animal cells

Animal cells don’t have a cell wall

This means they either:◦ Swell and burst if water osmoses in◦ Shrink if too much leaves

Why might water leave or enter the cell in each case??

Can no longer carry around body

cell wall cytoplasm and cell membrane

vacuole

The cell absorbs waterby osmosis .... ....but the cell wall stops the

cell expanding any more

Plant cells

Plenary-Match the word & definition

Osmosis When water enters a plant cell and pushes on the cell wall causing the cell to swell

Turgid A membrane that allows some substances to pass through and others cannot.

Plasmolysed The movement of particles from an area of high concentration to an area of low concentration

Partially permeable

The movement of water molecules from an area of their high concentration to an area of their low concentration

Diffusion When water leaves a plant cell, the cell contents shrink and the cell membrane pulls away from the cell wall

Xylem & Phloem

Xylem Phloem

Dead tissue Transports water and

dissolved minerals

Living tissue. Transports sucrose

(glucose from photosynthesis is converted into sucrose)

Xylem tissue is found in the vascular bundle in the stem. It is also found throughout the plant.

Phloem tissue is found in the vascular bundle in the stem. It is also found throughout the plant.

Transpiration why is this bag full of water?

http://www.youtube.com/watch?v=At1BJJDcXhk

What causes water molecules to stick together and what is this force called?

What happens when a water molecule evaporates?

Why does water not just fall down the xylem?

What conditions increase transpiration and why?

Why do plants wilt?

What is transpiration

Active transport

Active transport, why? Most minerals in the soil are in low

concentration. Active transport pumps are proteins that

use some of the plants energy to bring mineral ions into the root.

Explain using the term osmosis why active tranport is needed to draw in some minerals.

Exam Question - plenary