recap on osmosis as a special type of diffusion of water. understand the function of xylem and...
TRANSCRIPT
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