1.
2.
ENERGY, PHOTOSYNTHESIS
PHOTOSYNTHESIS IS LIGHT ENERGY CONVERTED TO CHEMICAL ENERGY.
3.
ENERGY
a. DEFINITION OF ENERGY: THE CAPACITY TO DO WORK.
b. TWO TYPES OF ENERGY: POTENTIAL AND KINETIC
4.
ENERGY REVIEW
a. Kinetic Energy – the energy of movement which includes light energy (the movement of
photons), heat energy (the movement of molecules), electricity (the movement of
electrically charged particles) and movement of large objects.
b. Potential Energy – Stored energy; includes chemical energy stored in the bonds that
hold atoms together in molecules, electrical energy stored in a battery and positional
energy like a bow and arrow.
5.
DIVING PICTURE
6.
ENERGY REVIEW
a. FIRST LAW OF THERMODYNAMICS: the principle of physics that states that within
any isolated system (in influx of energy), energy can be neither created nor destroyed
but can be converted from one form to another.
b. SECOND LAW OF THERMODYNAMICS: the principle of physics that states that any
change in an isolated system causes the quantity of concentrated, useful energy to
decrease and the amount of randomness and disorder (entropy) to increase.
7.
ENERGY TRANSFERS
a. Energy transfers are never entirely efficient. (Think second law of thermo).
b. With every transfer, some energy dissipates, and become less useful for doing work.
8.
OVERALL, ENERGY FLOWS IN ONE DIRECTION
a. NUCLEAR REACTIONS IN THE SUN PRODUCE ENERGY IN THE FORM OF
SUNLIGHT.
b. LIVING THINGS ON EARTH USE A CONTINUOUS INPUT OF SOLAR ENERGY TO
SYNTHESIZE COMPLEX MOLECULES AND MAINTAIN ORDERLY STRUCTURES
TO BATTLE ENTROPY.
9.
HOW DOES ENERGY FLOW IN CHEMICAL REACTIONS?
a. DEFINE: Chemical reaction: a process that forms or breaks the chemical bonds that
hold atoms together.
b. Chemical reactions convert one set of chemical substances, the reactants, into another
set, the products.
c. Reactants 
Products
d. Chemical reactions are exergonic or endergonic.
10.
EXERGONIC REACTION
a. Greek for energy out.
b. When a reaction is exergonic the reactants contain more energy than the products.
c. Example: Sugar in a marathon runners body during cellular respiration; Sugar is fuel
that contains more energy than the carbon dioxide and water that are produced when
that sugar breaks down.
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11.
ENDERGONIC REACTION
a. Greek for “energy in”
b. When a reaction is endergonic the products contain more energy than the reactants.
c. This will require an influx of energy from an outside source.
d. Many reactions in living systems contain more energy than the reactants.
e. Sugar, produced by a photosynthetic organism, contains far more energy than the
carbon dioxide and water from which it was formed.
12.
EXERGONIC REACTIONS ARE DOWNHILL REACTIONS
a. The reaction runs downhill from high energy to low energy. HOW DOES IT GET
STARTED?
b. ACTIVATION ENERGY: In a chemical reaction, the energy needed to force the electron
shells of reactants together, prior to the formation of the products.
i. Examples of Activation Energy:
ii. Giving a rock a push to go down a hill.
iii. Spark plug to ignite gasoline.
iv. Kinetic Energy is usual source for molecules.
13.
EXERGONIC REACTION – graph slide
14.
ENDERGONIC REACTIONS ARE UPHILL REACTIONS
a. Protein in a muscle cell contains more energy than the individual amino acids that were
joined together to synthesize it.
b. SYNTHESIZING COMPLEX MOLECULES REQUIRES AN INPUT OF ENERGY.
15.
COUPLED REACTIONS
a. Exergonic plus endergonic reactions equal COUPLED REACTIONS.
b. Coupled reaction: a pair of reactions, one exergonic and one endergonic, that are linked
together such that the energy produced by the exergonic reaction provides the energy
needed to drive the endergonic reaction.
c. Photosynthesis is a coupled reaction. The exergonic reaction (energy released) occurs
in the sun, the endergonic reaction (products contain more energy than reactants)
occurs in the plant.
16.
COUPLED REACTIONS IN THE HUMAN BODY
17.
ATP: Cellular Currency and ENERGY
a. ATP is an energy carrying molecule.
b. ENERGY-CARRIER MOLECULE: (like a rechargeable battery) a molecule that stores
energy in “high-energy” chemical bonds and releases the energy to drive coupled
reactions.
c. In cells, ATP is the most common energy-carrier molecule.
18.
ATP: ADENOSINE TRIPHOSPHATE
a. ATP: Adenosine triphosphate is a molecule composed of the sugar ribose, the base
adenine, and three phosphate groups; the major energy carrier in cells. The last two
phosphate groups are attached by “high energy” bonds.
b. ATP is the money of energy transfer, called the “energy currency of living cells”.
19.
ADP: Adenosine Diphosphate
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a. Energy released in cells during glucose breakdown is used to synthesize ATP from ADP
and phosphate.
b. ADP has low energy content.
c. ADP is ATP with the loss of one phosphate (adenosine DI phosphate).
20.
ATP BROKEN DOWN
a. The bonds joining the last two phosphate groups of ATP to the rest of the molecule
require a large amount of energy to form, so large amounts of energy are trapped there.
i. Marathon runners may use a pound of ATP every minute!
ii. Not a long term storage
iii. ADP is quickly converted back to ATP or it would be a short run!
21.
ENERGY CARRIERS, REDOX
a. In some exergonic reactions, some energy is transferred to electrons.
b. In oxidation-reduction reactions, or REDOX reactions, one molecule gives up electrons
(becomes oxidized) TO ANOTHER
c. Those energetic electrons are captured by ELECTRON CARRIERS: A molecule that
can reversibly gain or lose electrons.
22.
COMMON ELECTRON CARRIERS
i. NAD+ : Nicotinamide adenine dinucleotide
ii. FAD: Flavin adenine dinucleotide
iii. Molecule picks up electrons generated by exergonic reactions and holds them in
high-energy outer valence shell to offer to drive an endergonic reaction.
23.
MAKING REACTIONS OCCUR FASTER
a. CATALYST: A substance (often an enzyme) that speeds up a chemical reaction without
itself being permanently changed in the process; a catalyst lowers the activation energy
of a reaction.
24.
PHOTOSYNTHESIS:
a. The complete series of chemical reactions in which the energy of light is used to
synthesize high-energy organic molecules, normally carbohydrates, from low-energy
inorganic molecules, normally carbon dioxide and water.
b. LIGHT ENERGY CONVERTED TO CHEMICAL ENERGY!
25.
FORMS OF LIFE ON EARTH DEPEND ON THE SUGAR PRODUCED BY
PHOTOSYNTHETIC ORGANISMS AS AN ENERGY SOURCE AND RELEASE THE
ENERGY FROM THAT SUGAR THROUGH CELLULAR RESPIRATION, USING THE
PHOTOSYNTHETIC BY-PRODUCT OXYGEN.
26.
PHOTOSYNTHESIS
a. ENERGY OF SUNLIGHT CONVERTED INTO CHEMICAL ENERGY STORED IN THE
BONDS OF GLUCOSE USING CARBON DIOXIDE AND WATER AND RELEASING
OXYGEN AS A BY-PRODUCT.
b. PHOTOSYNTHESIS Chemical Reaction:
i. 6 CO2 + 6 H2O + ☼ = C6H12O6 + 6 O2
27.
PHOTOSYNTHESIS:
a. OCCURS IN EUKARYOTIC PLANTS, ALGAE, AND CERTAIN TYPES OF
PROKARYOTES
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b. ORGANISMS THAT PHOTOSYNTHESIZE ARE CALLED AUTOTROPHS (selffeeders).
28.
LEAVES ARE PERFECT!
a. Flat shape exposes large surface area to sun.
b. Thinness ensures sunlight can penetrate and reach chloroplasts.
c. CO2 from air received into cell through stomata.
29.
Inside the leaf are a few layers of cells called mesophyll (“middle of leaf”).
a. Mesophyll cells contain most of the leaf’s chloroplasts.
b. Photosynthesis occurs primarily there.
c. Vascular bundles supply water and minerals to the mesophyll cells and carry the sugars
they produce to other parts of the plant.
30.
Chloroplasts: the organelle in plants and plantlike protists that is the site of photosynthesis;
surrounded by a double membrane and containing an extensive internal membrane system
that bears chlorophyll.
31.
CHLOROPLASTS
a. STROMA: (NOT stoma as in stomata) is the semi-fluid material inside chloroplasts in
which the grana are embedded.
b. GRANA: stacks of thylakoids inside the chloroplast. (sing. Granum)
c. THYLAKOID: A disc-shaped membranous sac found in chloroplasts, the membranes of
which contain the photosystems and ATP-synthesizing enzymes used in the lightdependent reactions of photosynthesis.
32.
HOW IS LIGHT ENERGY CONVERTED INTO CHEMICAL ENERGY?
a. TO UNDERSTAND PHOTOSYNTHESIS, YOU NEED TO UNDERSTAND SOME
PROPERTIES OF SUNLIGHT ENERGY.
b. The sun emits energy in a broad spectrum of electromagnetic radiation.
c. Radiation is “radiant energy”, energy traveling in waves.
i. The electromagnetic spectrum ranges from short-wavelength gamma rays to
very long-wavelength radio waves.
ii. MEET ROY G. BIV
33.
ELECTROMAGNETIC ENERGY
a. LIGHT AND OTHER TYPES OF RADIATION ARE COMPOSED OF INDIVIDUAL
PACKETS OF ENERGY CALLED PHOTONS.
b. PHOTON: The smallest unit of light energy. The energy of a photon corresponds to its
wavelength.
c. Short wavelength photons are very energetic whereas longer wavelength photons have
lower energies.
d. Photosynthesizers use photons with wavelengths between 380 and 750 nanometers.
34.
ABSORBANCE OF PIGMENTS
a. Chloroplasts also contain other accessory pigments that absorb additional wavelengths
of light energy and transfer it to chlorophyll a.
b. CHLOROPHYLL a IS THE MAIN LIGHT CAPTURING PIGMENT IN LAND PLANTS.
35.
CHLOROPHYLL: a pigment found in chloroplasts that captures light energy during
photosynthesis; absorbs violet, blue and red light but reflects green light.
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i. Chlorophyll “a”: the main light capturing pigment in land plants.
ii. Chlorophyll “b”: accessory pigment-absorb additional wavelengths of light.
Reflects yellow green light, and therefore, is yellow-green.
iii. Carotenoids are accessory pigments found in all chloroplasts. They absorb blue
and green light, and thus appear mostly yellow, orange, or red.
36.
PHOTOSYNTHESIS
a. The chemical reactions of photosynthesis that depend on light (light-dependent
reactions) occur within the membranes of the thylakoids.
b. Photosynthetic reactions that can continue for a time in darkness (light-Independent
reactions) occur in the surrounding stroma.
37.
PHOTOSYNTHESIS:
a. Our simple chemical equation (earlier) for photosynthesis summarizes DOZENS of
individual reactions.
b. These reactions are classified as light-dependent reactions or light-independent
reactions (also known as the Calvin cycle, Calvin-Benson cycle or the Dark Cycle).
38.
SUNLIGHT DRIVES ATP FORMATION IN LIGHT DEPENDENT REACTIONS.
a. Light-dependent reactions: chlorophyll and other molecules embedded in the
membranes of the thylakoids capture sunlight energy and covert some of it into the
chemical energy stored in energy carrier molecules ATP and NADPH. Oxygen gas is
released.
39.
THE CHLOROPLAST IS A SUGAR FACTORY
a. Light-INDEPENDENT reactions: the enzymes in the stroma use the chemical energy of
the carrier molecules to drive the synthesis of glucose or other organic molecules.
40.
PHOTOSYNTHESIS FACTS
a. Photosynthesis occurs in the mesophyll of a leaf.
b. Light harvesting complexes surround the photosystems in the thylakoid membranes that
contain pigments.
c. Carbon dioxide enters through the stomata to participate in the Calvin cycle.
d. Oxygen exits through the stomata as a byproduct of the light cycle.
e. The chloroplast is the site of photosynthesis.
41.
The chlorophyll molecule
a. Chlorophyll “a”, the pigment that participates directly in the light reactions of
photosynthesis has a “head” called a porphyrin ring with a magnesium atom at its
center. Attached is a hydrocarbon tail – where have we seen this structure before?
42.
DIFFERENT PLANTS THAT PHOTOSYNTHESIZE
43.
PHOTOSYNTHESIS OVERVIEW
44.
DRAWING
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