THE SUN: MAIN SOURCE OF ENERGY FOR LIFE ON EARTH

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THE SUN MAIN SOURCE OF ENERGY FOR LIFE ON EARTH
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THE BASICS OF PHOTOSYNTHESIS

• Almost all plants are photosynthetic autotrophs,
  as are some bacteria and protists

• Autotrophs generate their own organic matter
  through photosynthesis
• Sunlight energy is transformed to energy stored
  in the form of chemical bonds

(c) Euglena
(d) Cyanobacteria
(b) Kelp

• (a) Mosses, ferns, and
• flowering plants

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synthesis BUILD
photo LIGHT
Photosynthesis means building with Light
carbon dioxide CO2
water H2O

glucose C6H12O6
oxygen O2

chlorophyll
? Green plants can make their own food from ..
and .. ? using energy in the form of
. ? which is absorbed by chlorophyll in
the ... ? The end products of
photosynthesis are . and .
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WHY ARE PLANTS GREEN?
It's not that easy bein' green Having to spend
each day the color of the leaves When I think it
could be nicer being red or yellow or gold Or
something much more colorful like
that Kermit the Frog
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WHY ARE PLANTS GREEN?
Different wavelengths of visible light are seen
by the human eye as different colors.
Gammarays
Micro-waves
Radio waves
X-rays
UV
Infrared
Visible light
Wavelength (nm)
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THE COLOR OF LIGHT SEEN IS THE COLOR NOT ABSORBED

• Chloroplasts absorb light energy and convert it
  to chemical energy

Reflected light
Light
Absorbed light
Transmitted light
Chloroplast
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AN OVERVIEW OF PHOTOSYNTHESIS

• Photosynthesis is the process by which
  autotrophic organisms use light energy to make
  sugar and oxygen gas from carbon dioxide and
  water

Carbondioxide
Water
Glucose
Oxygengas
PHOTOSYNTHESIS
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AN OVERVIEW OF PHOTOSYNTHESIS

• The light reactions convert solar energy to
  chemical energy
• Produce ATP NADPH

Light
Chloroplast
NADP?
ADP P
Calvin cycle

• The Calvin cycle makes sugar from carbon dioxide
• ATP generated by the light reactions provides the
  energy for sugar synthesis
• The NADPH produced by the light reactions
  provides the electrons for the reduction of
  carbon dioxide to glucose

Light reactions
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Chloroplasts Sites of Photosynthesis

• Photosynthesis

• Occurs in chloroplasts, organelles in certain
  plants
• All green plant parts have chloroplasts and carry
  out photosynthesis
• The leaves have the most chloroplasts
• The green color comes from chlorophyll in the
  chloroplasts
• The pigments absorb light energy

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• The location and structure of chloroplasts

Chloroplast
LEAF CROSS SECTION
MESOPHYLL CELL
LEAF
Mesophyll
Intermembrane space
CHLOROPLAST
Outer membrane
Granum
Innermembrane
Stroma
Grana
Thylakoidcompartment
Stroma
Thylakoid
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Chloroplast Pigments

• Chloroplasts contain several pigments

• Chlorophyll a
• Chlorophyll b
• Carotenoids

Figure 7.7
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Plants produce O2 gas by splitting H2O

• The O2 liberated by photosynthesis is made from
  the oxygen in water (H and e-)

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It's not that easy bein' green but it is
essential for life on earth!
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The glucose is very useful for the plant
Can be converted to fructose for the fruit
Can be used in respiration to release energy
Can be converted into fats and oils for the seeds
glucose
Can be joined together to make cellulose for the
cell walls
can be joined together to make starch for storage
Can be combined with nutrients from the soil to
make proteins for the new growth