Chapter 8 PowerPoint

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Transcript Chapter 8 PowerPoint

8-1 Energy & Life
• All living things require energy
• But what is it and where does it
come from?
Chemical Energy & ATP
• Cells use adenosine
triphosphate to store &
release energy
• Is like a fully charged battery
• A phosphate can be + or - to
store or release energy
• It provides energy to work the
sodium (Na) potassium (K) pump
• It provides energy for movement
• It powers the production of
proteins and other molecules
• It even helps fireflies glow!
8-2 Photosynthesis: An
• Plants use energy from the
sun to convert water and
carbon dioxide into
carbohydrates (sugars &
starches) and release
oxygen as a waste product
When a tiny
seed grows
into a tall
where does
its mass
• In addition to water and carbon dioxide,
photosynthesis requires light and
chlorophyll, a molecule in chloroplasts.
• Sunlight, which you perceive as white
light, is actually a mixture of different
wavelengths of light.
• Your eyes see the different wavelengths of
the spectrum as colors.
• Chlorophyll does not
absorb light well in the
green region of the
• Green light is reflected
by leaves, which is
why plants look green.
• Some of the light
absorbed is converted
directly to electrons in
chlorophyll, raising the
energy for
Inside a chloroplast
Light Dependant Reactions
• Reactions requiring light produce O2 and
convert ADP and NADP+ into the energy
carriers ATP & NADPH.
• This reaction requires light.
• It occurs in the thylakoid of a chloroplast.
• Pigments in photosystem II absorbs light.
• The absorbed light increases the energy of
• Water is broken up into H+ and O2.
• Oxygen is released into the air.
• NADP+ picks up high energy electrons
and H+ ions to produce NADPH.
• The inside of the membrane fills with H+,
making the outside negative.
• The difference of charge provides energy
to make ATP.
The Calvin Cycle
• ATP and NADPH are used from the light
dependant reactions to produce highenergy sugars.
• Melvin Calvin worked
out the details for this
light independent
Occurs in stroma.
• A. CO2 molecules combine with carbon
molecules. The result is 12-3 carbon
• Carbon molecules are converted into
higher energy forms.
• Where do you think this energy came
• Some Carbon molecules are removed &
used to produce sugars & other
Factors affecting photosynthesis
• Shortage of water can slow or stop the
• Temperature should be between 0’c – 35’c
since enzymes work best at those
• Light intensity
can speed up
the process up
until a certain