Post on 14-Feb-2018
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Biology 3
Ch 4 Photosynthesis and
Respiration
Dr. Terence Lee
Enzymes
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Why do some adults get sick when they drink milk?
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Energy Conversions
� All life depends on capturing energy from the sun and converting it into a form that living organisms can use.
� Two key processes
Take-home message 4.1
� The sun is the source of the energy that powers all living organisms and other “machines.”
What is energy?
� The capacity to do work
�Work
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Kinetic Energy
� The energy of moving objects
Potential Energy
� A capacity to do work that results from the location or position of an object
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Energy Conversions� Only ~1% of the energy released by the sun that earth receives is captured and converted by plants.
• Converted into chemical bond energy
First Law of Thermodynamics
� Energy can never be created or destroyed.
ATP Molecules
� Cells cannot use light energy directly to do work.
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Photosynthesis
• The process in green plants and certain other
organisms by which …
Photosynthesis: The Big Picture
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“Photo” and “Synthesis”
Light Energy
� Different photons carry different amounts of energy, carried as waves.
� Length of the wave = amount of energy the photon contains.
Electromagnetic Spectrum
� Range of energy that is organized into waves of different lengths.
� Shorter the wavelength, higher the energy.
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Visible Spectrum
�Range of energy humans see as light
� Pigments
Chlorophyll
� Plant pigment
� Absorbs certain wavelengths of energy (photons) from the sun
Plant Pigments
� Plant pigments can only absorb specific wavelengths of energy
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Where does oxygen come from?
An Electron Transport Chain
Connects the two photosystems
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The Second Photosystem
� Follow the electrons
The Calvin Cycle
� Series of chemical reactions
� Occurs in stroma
The Processes in the Calvin Cycle Occur in Three Steps:
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• Cellular Respiration – control the release of
chemical-bond energy from large, organic
molecules and use the energy for the many
activities to sustain life.
Cellular Respiration
� Requires (1) fuel and (2) oxygen.
� Potential energy stored in chemical bonds of sugar, protein, and fat molecules.
4.13 The first step of cellular respiration: glycolysis is the universal energy-releasing pathway.
Glycolysis:
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Glycolysis
Three of the ten steps yield energy
– quickly harnessed to make ATP.
High-energy electrons are transferred to NADH.
Net result:
�each glucose molecule broken down into two
molecules of pyruvate
The Preparatory Phase to the Krebs Cycle
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The “bag-within-a-bag”
Follow the Electrons, as We Did in Photosynthesis
#2) This proton concentration gradient represents a significant
source of potential energy!
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