Download Reactions of Photosynthesis (continued)

Reactions of
Photosynthesis
(continued)
(and you thought it was over…)
Also, the Beginning to
Cellular Respiration
2. Calvin Cycle
(aka Light-Independent Reaction)
What goes in:
•CO2
•NADPH
•ATP
What comes
out:
•Sugar
• Occurs in stroma of
chloroplast
• Plants use the ATP and
NADPH from the Light
Reactions to build highenergy sugars for longterm energy storage
• Need CO2 here…
Steps in Calvin Cycle
• 1) An enzyme adds CO2 from the air to a
five-carbon sugar called RuBP. The
resulting molecule breaks into two threecarbon molecules.
Steps in Calvin Cycle
(continued)
• 2) Using energy from ATP and NADPH
produced by the Light Reactions, enzymes
convert each three-carbon molecule to the
three-carbon sugar G3P.
Steps in Calvin Cycle
(continued)
• 3) For every three molecules of CO2 that
enter the cycle, the net output is one G3P
sugar that can be used to make glucose.
The other G3P sugars continue in the
cycle.
Steps in Calvin Cycle
(continued)
•
4) Using energy from ATP, enzymes
rearrange the remaining G3P sugars to
regenerate RuBP to keep the cycle
going.
CO2 (from air)
1
P
RuBP sugar
Three-carbon molecule
P
P
Calvin
cycle
CO2 (from air)
1
P
RuBP sugar
Three-carbon molecule
ATP
P
P
ADP  P
Calvin
cycle
– –
NADPH
NADP
G3P sugar
P
2
CO2 (from air)
1
P
RuBP sugar
Three-carbon molecule
ATP
P
P
ADP  P
Calvin
cycle
– –
NADPH
NADP
G3P sugar
3
G3P sugar
P
P
G3P sugar
P
2
Glucose
(and other
organic
compounds)
CO2 (from air)
1
P
RuBP sugar
Three-carbon molecule
4
ATP
P
P
ADP  P
ADP  P
Calvin
cycle
– –
NADPH
ATP
NADP
G3P sugar
3
G3P sugar
P
P
G3P sugar
P
2
Glucose
(and other
organic
compounds)
C3 Plants vs C4 Plants vs CAM
Plants
• C3 plants use CO2 directly from the air – soybeans, oats, wheat, rice
– These plants reduce water loss during the day, but this also
reduces plant growth by decreasing the amount of sugar
produced
• C4 plants incorporate CO2 into a four-carbon compound first – corn,
sugarcane
– These plants reduce water loss, but use the compound
containing CO2 to keep making sugars = easier to grow in dry
climates
• CAM Plants also incorporate CO2 into a four-carbon compound –
cacti, pineapple, aloe
– These plants allow CO2 at night, thus reducing water loss during
the day, but they can still perform photosynthesis during the day
Calvin Cycle
• The ultimate result from the Calvin Cycle
is to make sugars/food for the plant.
Plants then use that sugar/food for Cellular
Respiration…
Photosynthesis Review
Chemical Energy and Food
• Food provides energy for organisms
• One gram of glucose (C6H12O6) can
release 3811 calories of heat. A calorie is
the amount of energy needed to raise the
temperature of 1 gram of water 1 degree
Celsius
Equation for Cellular Respiration
6O2 + C6H12O6
oxygen
+
glucose
6CO2 + 6H2O + Energy
carbon dioxide +
water
+ energy (ATP)
Cellular respiration takes place in steps to release energy gradually
Cellular Respiration With
Oxygen Present
Glucose
(C6H1206)
Glycolysis
Citric Acid
Cycle
+
Oxygen
(02)
Electron
Transport
Chain
Carbon
Dioxide
(CO2)
+
Water
(H2O)
Mitochondrion
Cytoplasm
Cytoplasm
Animal cell
Plant cell
Cytoplasm
Mitochondrion
High-energy
electrons
via carrier
molecules
Glycolysis
2
Pyruvic
acid
Glucose
ATP
Citric
Acid
Cycle
ATP
Electron
Transport
ATP
Chemical Pathways
Aerobic –
O2 Present
Glucose
Glycolysis
Citric
Acid
cycle
Electron
transport
Anaerobic – O2 Absent
Fermentation
(without oxygen)
Alcohol or
lactic acid
Overview of Cellular Respiration
• Both plants and animals perform cellular
respiration!
• In the presence of oxygen, glycolysis is
followed by the Citric Acid Cycle (aka
Krebs Cycle) and electron transport chain
= cellular respiration – releases energy by
breaking down food in the presence of
oxygen
Cellular Respiration – Stage 1:
Glycolysis
• Cells gradually release energy from
glucose through several pathways,
beginning with glycolysis
• Glycolysis releases only a small amount of
energy. If oxygen is present, glycolysis
leads to two other pathways that release
more energy. If oxygen is not present, a
different pathway is followed
Glycolysis
What goes in:
•Glucose
•2 ATPs
What comes
out:
•2 pyruvic
acids
•Net gain of
2 ATPs
(makes 4,
but uses 2
ATPs to
work
•NADH
• Occurs in cytoplasm
• Process in which one
molecule of glucose is broken
in half to produce two
molecules of pyruvic acid (a 3carbon compound)
• Doesn’t require oxygen!!
ATP Production in Glycolysis
• Cell needs to put in a little energy to get things
going
• 2 molecules of ATP are used up during glycolysis
• At the end, 4 ATP molecules are produced – net
gain of 2 ATP molecules
• Glycolysis occurs so fast, that thousands of ATP
molecules are made in milliseconds
NADH Production
– Removes 4 high-energy electrons and passes
them to an electron carrier (NAD+)
– Each NAD+ accepts a pair of electrons =
NADH – holds electrons until they can be
transferred to other molecules – passes
energy from glucose to other pathways in the
cell
Section 9-1
Glucose
Glycolysis
2 Pyruvic acid
To the electron
transport chain
Section 9-1
Glucose
Glycolysis
2 Pyruvic acid
To the electron
transport chain
Section 9-1
Glucose
Glycolysis
2 Pyruvic acid
To the electron
transport chain
Next…
• IF oxygen is PRESENT Citric Acid
Cycle (aka Krebs Cycle) and Electron
Transport Chain (aerobic respiration)
• IF oxygen is ABSENT
(anaerobic respiration)
Fermentation