photosynthesis
DESCRIPTION
Photosynthesis. Introduction. 6 CO 2 + 6 H 2 O + light energy → C 6 H 12 O 6 + 6 O 2 Photosynthesis consists of two independent pathways called the light-dependent reaction (light reaction) and the light-independent reaction (dark reaction). Introduction. - PowerPoint PPT PresentationTRANSCRIPT
Photosynthesis
Introduction
6 CO2 + 6 H2O +
light energy → C6H12O6 + 6 O2
Photosynthesis consists of two independent pathways called the light-dependent reaction (light reaction) and the light-independent reaction (dark reaction).
IntroductionLight Reactions: the energy in sunlight is trapped, O2 is released, and both ATP and NADPH + H+ (hydrogen-carrier molecule) are formedDark Reactions: the ATP and NADPH + H+ react with CO2 from the atmosphere and form glucoseThe entire process results in the transformation of light energy from the sun into energy stored in the bonds of the glucose molecule.
Structure of a Chloroplast
The light reactions take place in the thylakoid membrane
The dark reactions take place in the stroma
Structure of a Chloroplast
Electromagnetic Spectrum
Why are plants green?
Pigments
Pigments are light-absorbing compounds.
Pigments appear colored because they absorb light of certain wavelengths and reflect that of others.
Chlorophyll a is the primary pigment in green plants that absorbs red and blue/violet light and reflects green light.
Light Reaction
Light Reaction
Also called Light Dependent ReactionPigments that are in the chloroplasts intercept light and begin the light reactions of photosynthesis.The light reactions occur in two photosystems (located in the thylakoid membrane):
Photosystem: a unit of several hundred chlorophyll a molecules and associated acceptor molecules
-photosystem I (PSI) -photosystem II (PSII)
Photosystems
Sequence these in the order of occurrence of the light reactions:
Electrons of Photosystem II chlorophylls are excited
Electrons are transferred to NADP to form NADPH
Light strikes the leaf
Sequenced in the order of occurrence of the light reactions:
Light strikes the leaf
Electrons of Photosystem II chlorophylls are excited
Electrons are transferred to NADP to form NADPH
Excited Electrons
NADPH
NADP+ is an electron acceptor
NADP+ + 2 e- + 2 H+ NADPH + H+
PSII
PSI
Water (H2O)
Oxygen (O2)
Hydrogen Ion (H+)
Electron
Lumen
PrimaryElectronAcceptor
Proton Pump
ATP Synthase
Thylakoid
ETC
Dark Reaction
Dark ReactionThe dark reaction is also known as the Calvin Cycle, after an American scientist (Melvin Calvin) who figured out the pathway.The dark reaction is also known as the C3 Cycle because the first stable products of this pathway are molecules that contain three carbon atoms.The Calvin Cycle occurs in the stroma.
12 NADPH + H+
~
e12 ADP + P
12 ATP
12 NADP+
e-
10 PGAL
~
e6 ADP + P
6 ATP
6 CO2C
6 RuBPC C C C C
12 PGAC C C
12 PGALC C C
2 PGALC C C
GlucoseC C C C C C
C C C C C C
unstablecompound
Cells convert the storage bond energy to the phosphate bonds of ATP in the process of respiration.
Adenosine triphosphate
ATP – P = ADP
ADP + P = ATP
Adenosine Diphosphate
7.3 kcal/mole energy released
Adenosine Monophosphate
Adenosine Diphosphate
7.3 kcal/mole energy released
Adenosine Triphosphate
T/F Questions
ATP has more energy than ADP.
T/F
There are three phosphate atoms in ATP?
T/F
You are storing energy right now in your body in the phosphate bonds of ATP.
T/F
ATP is made of a sugar, the base adenine and a phosphate.
Stomata