Transcript Calvin Cycle Reactions

The Great Life Processes
Photosynthesis and Aerobic
Respiration
Photosynthesis
Outline
Flowering Plants
Photosynthetic Pigments
Photosynthesis
– Light Reactions
Noncyclic
Cyclic
– Calvin Cycle Reactions
– C4
– CAM
Photosynthetic Organisms
Photosynthesis transforms
solar energy into the chemical
energy of a carbohydrate.
–All organisms use organic
molecules produced by
photosynthesizers as a
source of chemical energy.
Flowering Plants
The green portions of plants,
particularly leaves, carry on
photosynthesis.
–Leaf of flowering plant contains
mesophyll tissue.
Contains cells specialized to
carry on photosynthesis.
Flowering Plants
CO2 enters leaf through stomata.
CO2 and water diffuse into
chloroplasts.
–Double membrane surrounds fluid
(stroma).
Inner membrane system within
stroma form flattened sacs
(thylakoids).
–Often stacked to form grana.
–Chlorophyll and other
pigments within thylakoid
membranes are capable of
absorbing solar energy.
Photosynthetic Pigments
Most pigments absorb only
some wavelengths of light and
reflect or transmit the other
wavelengths.
Absorption Spectra
–Organic molecules and
processes within
organisms are chemically
adapted to visible light.
Photosynthetic Pigments and
Photosynthesis
Photosynthetic Reaction
Light Reaction - Chlorophyll
absorbs solar energy and
energizes electrons.
–Electrons move down electron
transport chain.
Solar energy  ATP,
NADPH
Calvin Cycle Reaction - CO2 is
taken up and reduced to a
carbohydrate.
–Reduction requires ATP and
NADPH.
ATP, NADPH 
Carbohydrate
Photosynthesis Overview
Light Reactions
Light reactions consist of
two electron pathways:
–Noncyclic electron
pathway
–Cyclic electron pathway
Both pathways produce
ATP, but only the noncyclic
pathway also produces
NADPH.
Noncyclic Electron
Pathway
Electron flow can
be traced from
water to a
molecule of
NADPH.
Uses two photosystems, PS I
and PS II.
–Photosystem consists of
pigment complex and
electron acceptor molecules
in the thylakoid membrane.
Pigment complex helps
gather solar energy.
Cyclic Electron Pathway
Cyclic pathway begins when PS I
pigment complex absorbs solar
energy and is passed from one
pigment to another until it is
concentrated in a reaction center.
–Pathway only results in ATP
production.
Thylakoid Organization
Calvin Cycle Reactions
Calvin cycle is a series of
reactions that produce
carbohydrates before
returning to the starting point
again.
–Utilizes atmospheric
carbon dioxide to produce
carbohydrates. Includes:
Carbon dioxide fixation
Carbon dioxide
reduction
RuBP Regeneration
Calvin Cycle Reactions
Carbon Dioxide Fixation
–CO2 is attached to RuBP.
The result is a 6-carbon
molecule which splits into two
3-carbon molecules.
Rubisco speeds up this
reaction.
Calvin Cycle Reactions
Reduction of Carbon Dioxide
Calvin Cycle Reactions
Regeneration of RuBP
Importance of Calvin Cycle
PGAL (glyceraldehyde-3phosphate) is the product of
the Calvin cycle that can be
converted to a variety of
organic molecules.
–A plant can utilize the
hydrocarbon skeleton of
PGAL to form fatty acids and
glycerol, which are combined
in plant oils.
C4 Photosynthesis
In C4 leaf, bundle sheath cells
and mesophyll cells contain
chloroplasts.
Mesophyll cells are arranged
concentrically around the
bundle sheath cells.
In hot, dry
climates, net
photosynthetic
rate of C4 plants is
about 2-3 times
that of C3 plants.
–Avoid
photorespiration
C3 vs C4
Carbon Dioxide Fixation in C3
and C4 Plants
CAM Photosynthesis
Crassulacean-Acid Metabolism
–C4 plants partition carbon
fixation in space, while CAM
partitions by time.
During the night, CAM
plants fix CO2, forming C4
molecules, which are stored
in large vacuoles.
–C4 molecules release CO2
to Calvin cycle when
NADPH and ATP are
available.
Water Conservation
Review
Flowering Plants
Photosynthetic Pigments
Photosynthesis
– Light Reactions
Noncyclic
Cyclic
– Calvin Cycle Reactions
– C4
– CAM
Aerobic Respiration
Outline
Glycolysis
Transition Reaction
Citric Acid Cycle
Electron Transport System
Fermentation
Metabolic Pool
–Catabolism
–Anabolism
Cellular Respiration
A cellular process that
requires oxygen and gives off
carbon dioxide.
–Most often involves
complete breakdown of
glucose to carbon dioxide
and water.
Energy within a glucose
molecule is released
slowly so that ATP can
be produced gradually.
NAD+ and FAD are
oxidation-reduction
enzymes active during
cellular respiration.
Glucose Breakdown
During glycolysis, glucose is
broken down in cytoplasm to
two molecules of pyruvate.
During transition reaction,
pyruvate is oxidized, NADH
is formed, and waste carbon
dioxide is removed.
Citric acid cycle results in
NADH and FADH2, release
of carbon dioxide, and
production of additional
ATP.
Electron transport chain
produces 32 or 34
molecules of ATP.
Glucose Breakdown
Glycolysis
Two ATP are used to initiate the
breakdown of glucose, which
during the reaction splits into
two 3-carbon molecules of
PGAL. PGAL carries a
phosphate group.
Phosphorylation
Oxidation of PGAL occurs by
removal of electrons
accompanied by hydrogen
ions. Hydrogen atoms (e2 and
H2) are picked up by
+
coenzyme NAD (nicotinamide
adenine dinucleotide).
+
+
2NAD + 4H  2 NADH + 2H
Glycolysis
Oxidation of PGAL and
subsequent substrates results
in four high-energy phosphate
groups, which synthesize four
ATP.
Substrate-level phosphorylation
involves an enzyme passing a
high-energy phosphate to ADP,
and ATP results.
NOTE: Since starting this
process requires 2 ATP,
and since 4 ATP are
harvested, the net gain for
glycolysis is 2 ATP.
This process occurs
OUTSIDE the
mitochondrion.
Oxygen is the key!
In times when oxygen is not
available, energy processes
don’t proceed beyond this
point. This process is then
called anaerobic respiration, or
fermentation.
Various types of fermentation
are identified by their products.
Types of fermentation:
Lactic acid fermentation occurs in
muscle cells when oxygen levels
are low. Lactic acid builds up in
muscles; if athletes don’t stretch
and walk after heavy exercise
(which reduces lactic acid
buildup), soreness and stiffness
results due to muscle damage.
Alcoholic fermentation occurs
when yeasts break down
sugars and other material into
alcoholic substances.
Examples: beer, wine. Bread
rising.
All of the following reactions
occur inside the mitochondrion
(within its membranes.) This
begins the AEROBIC portion
of respiration because it
uses…. OXYGEN!
The Transition Reaction
This is an exciting process, the
transition of respiration from
anaerobic to aerobic.
Yes, you SHOULD be excited! If it
weren’t for this process, your level
of organization would be similar to
that of a bacterium!
The transition reaction
connects glycolysis to the citric
acid cycle.
Pyruvate (PGAL) is converted
to a 2-carbon acetyl group
(active acetate) attached to
coenzyme A, or CoA, and CO2
is given off as a waste product.
The transition reaction is an
oxidation reaction in which
electrons are removed from
pyruvate to NAD+, and NAD+
goes to NADH + H+ as acetylCoA forms.
This reaction occurs twice per
glucose molecule, since
glycolysis results in production
of two molecules of pyruvate.
The Citric Acid (Krebs) Cycle
Active acetate enters the citric
acid cycle. Every rotation of
the cycle gives off CO2 and
produces one ATP molecule.
Since two molecules of active
acetate enter the cycle, a total
of 2 ATP are produced.
Electron Transport Chain
Hydrogen atoms or
electrons harvested earlier
from the breakdown of
glucose are passed down a
series of molecules until
they are finally received by
oxygen and reduced to
water.
NADH and FADH2 bring
electrons to the electron
transport system, also known
as the respiratory chain or
the cytochrome system.
For every pair of electrons
that enters by way of NADH,
3 ATP result.
For every pair of electrons
that enters by way of FADH2,
2 ATP result.
As the electrons move down the
system, carried down a series of
energy-extracting enzymes by
carrier molecules,
NADH, FADH
32-34 ATP
energy is
captured and
used to form
ATP.
H +O
2
2
Oxygen, the final acceptor
of the electrons, becomes a
part of water, the second
waste product.
As electrons pass from one
molecule to the next along
the chain, oxidation occurs
and releases the energy
needed for ATP buildup—
enough to form up to 34
molecules of ATP.
Energy Production
Total maximum energy
production for aerobic
respiration, on average:
2 ATP (glycolysis)
+ 2 ATP (citric acid cycle)
+34 ATP (aerobic respiration)
TOTAL: 38 ATP