Transcript Do now - MrSimonPorter

Do now!
Can you stick the target
sheets in please?
Can you then fill out the
first column of the
target sheet?
YouTube - Human ' Treeman '
begs for help as he turns into a
tree.
9c – Plants and photosynthesis
Photosynthesis
Water + carbon dioxide (+ light energy)
Reactants
•
•
•
•
glucose + oxygen
Products
Chlorophyll absorbs light energy to make photosynthesis happen
Most of the glucose is then turned into starch by the plant
Starch is an insoluble storage material
Photosynthesis only happens when it is light
YouTube - Photosynthesis Song
Plants use photosynthesis to make
their own food
Plants respire too!
glucose + oxygen
Water + carbon dioxide (+ energy)
Reactants
Products
• Aerobic respiration (uses oxygen)
• Happens all the time
• Overall plants produce more oxygen by photosynthesis than they
use by respiration
YouTube - Plant Physiology: Respiration
(Britannica.com)
Leaves
Waterproof layer protects leaf
Most photosynthesis occurs here
(lots of chloroplasts)
Carry water
vein
Carry food
Controls size of stoma (plural = stomata)
Hole that lets carbon dioxide in and
oxygen out by diffusion
Leaves
• Thin so that CO2 does not have to travel
far to palisade cells
• Photosynthesis faster in more light
• Photosynthesis faster by increasing CO2
concentration
• Less light = need for bigger leaves
Use of glucose by plants
• Glucose molecules can be joined together
(polymerisation) to make starch (a food store)
or cellulose (cell walls) or fats
Glucose molecule
Use of glucose by plants
Glucose can also be turned into amino acids
by combining with Nitrogen from nitrates.
Amino acids can be joined together to make
proteins
Roots
• Root hair cells have a large surface area to
absorb more water
Xylem
The water travels up xylem tubes to the
leaves.
The water also contains minerals salts.
Phloem tubes
These transport dissolved glucose around the
plant
Mineral salts
• Nitrates needed to make
proteins – too little = poor
growth
• Phosphates needed to
make cell membranes and
for root growth
• Potassium needed to help
enzymes for photosynthesis
and respiration – too little =
yellow leaves
Changing atmosphere
When the earth formed (around 4600
million years ago) the atmosphere was
mainly carbon dioxide (produced by
volcanoes)
Changing atmosphere
Around 3800 million years ago, algae
evolved, which used photosynthesis to
turn CO2 into glucose and oxygen.
The oxygen would have been poisonous
to other organisms living at the time.
Changing atmosphere
Today the atmosphere is
78% Nitrogen
21% oxygen
0.9% Argon
About 0.04 % CO2
Variable amounts of water vapour
Changing atmosphere
The composition of the atmosphere
continues to change……WHY?
Homework
Read pages 26 to 35 of your book AT
LEAST TWICE, due Friday 15th April
I wonder why he’s
asked us to do
that?
He must have a
very good reason.