PhotosynthesisSection 1: Energy and Life
Botany is the study of plants.
What characteristics would define a plant?
8.1 Energy and Life
Energy – the ability to do work
All living things need chemical energy to survive.
The most important molecule cells use to store and release energy is ATP (adenosine triphosphate)
Chemical Energy and ATP• When an organism uses the energy
from ATP, the ATP is converted into ADP– ADP (Adenosine Diphosphate ) has
only 2 phosphate groups.– Cells can add a phosphate to ADP to
make ATP to store energy.(This requires energy)
– How is ATP and ADP similar to rechargeable batteries?
– Where do YOUR cells get the energy to convert ADP into ATP?
How could a small seed gain enough energy to grow into seed a giant tree?
Heterotroph – obtains energy from food it consumes
Autotroph – uses energy from the sun to produce food
Chemical Energy and ATP
Overall Photosynthesis Equation
6CO2 + 6H2O C6H12O6 + 6O2
LIGHT
Carbon Dioxide Water
Glucose Oxygen
Photosynthesis: the process where plants convert energy from the sun into chemical energy stored in the bonds of carbohydrates.
Chemical Energy and ATP
Light and Pigments
Light Speed, c = 2.9979 x 108 m/s
Or 670.6 million mph
How are the two types of light different? How are they similar?
Electromagnetic Spectrum
Wave length and energy are inversely proportional
The smaller the wave length, the more energy
Which type of light has more energy, the blue or the red? Explain.
Light and Pigments
Light and Pigments• What colors of light
are being absorbed?
• What colors of light are being reflected?
• What color would the object appear if there was no blue light?
• Why are plants usually green?
• Pigments – light absorbing molecules
• Chlorophyll – the most abundant pigment in plants, that absorbs blue and red light.– Chlorophyll a - a blue-green
pigment – Chlorophyll b - a yellow-
green pigment
Light and Pigments
• Accessory Pigments: pigments other than chlorophyll.– Carotene: orange– Xanthophyll: yellow– Anthocyanin: red
• Why do plants need accessory pigments?– They absorb light in other
regions of the spectrum
• The accessory pigments are always present in most plants but masked by the chlorophyll.
Light and Pigments
Why do leaves change color in the fall?
Answer: Shorter day lengths stop chlorophyll production, and expose accessory pigments
Light and Pigments
Photosynthesis: An Overview
• Photosynthesis takes place in the chloroplast– Thylakoids – saclike photosynthetic
membrane in the chloroplast– Grana – stacks of thylakoids– Stroma - the region outside of the
thylakoid membranes
High Energy Electrons• High energy electrons produced
by the chlorophyll are highly reactive and need a special carrier
• NADP+ accepts a pair of high energy electrons and a hydrogen ion (H+) and carriers them to a chemical reactions elsewhere in the cells.
• NADP+ NADPH
Photosynthesis: An OverviewPhotosynthesis is a complex process that can be broken
down into 2 steps:
Light-Dependent Reactions• Occurs in the thylakoid
membranes of the chloroplast.• Light energy breaks apart a
molecule of H2O– Electrons are energized and
used to convert NAD+ into NADH.
– Hydrogen ions are used to convert ADP into ATP.
– Oxygen is released as a waste product.
Light-Independent Reactions• The NADH and ATP from the
light reaction move to the stroma.
• The leaf absorbs CO2 from the atmosphere.
• The energy from the NADH and ATP is used to convert CO2 into carbohydrates.
• What is the main function of carbohydrates?
Light-Independent Reactions
• Each molecule of glucose contains enough energy to produce 36 ATP’s.
• Plants produce starch when they need to store energy.
• Starch is a long chain of glucose.
Photosynthesis and Cell Respiration• Cell Respiration is the opposite of
photosynthesis.– What is the equation for
photosynthesis?
– What is the equation for respiration.
– Respiration breaks down carbohydrates into ATP.
Photosynthesis and Cell Respiration• Plants perform both
photosynthesis and respiration.– Think: It would pointless to
make carbohydrates if you did not break them down into energy.
Factors Affecting Photosynthesis• Water– No enough water means that their will
not be enough electrons and H+ to make ATP and NADPH.
– Can too much water harm a plant?• Temperature– Too cold: photosynthesis occurs slowly– Too hot: the enzyme that control
photosynthesis break down.• Light Intensity– Light is needed to energize the electron
from the H2O molecule.– Light that is the wrong color or not
intense will slow down photosynthesis.
Short Answer Questions
• Explain how the ATP molecule functions similar to rechargeable batteries? (4 points)
• Write the overall equation for photosynthesis. (2 points)
• Explain why leaves of deciduous trees change color in the fall? (3 points)
Photosynthesis
includes bothconverts
in which in which
(b) (c)
light-excitedelectrons ofchlorophyll
CO2 is fixed toRuBP
and then
(h)reduceNADP+ to
using
to produce
sugar(G3P)
(f)
chemiosmosis
(e)
(g)
by
producing
are passeddown
(d)
and
to
chemicalenergy
H2O is split
(a)
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