Download Cellular Respiration

Cellular Respiration
AP Biology
Photosynthesis….then
• Photosynthesis captures
the sun’s energy and
converts it to glucose
• Cellular respiration is the
breakdown of glucose to
produce ATP
• ATP is useable energy
• This process is carried
out by plants and every
other organism in the
various trophic levels
Cellular Respiration
C6H12O6
+
6O2
6CO2 +6 H2O
This is the summary: showing
beginning and end
There are three stages in between
Cellular Respiration
• Occurs in three
stages:
• Glycolysis
• Kreb’s Cycle
• Electron Transfer
Phosphorylation
• Net ATP yield
depends on whether
oxygen is present
ATP Yield
• Anaerobic respiration
yields two ATP
• Aerobic respiration
yields 36 ATP
• Bacteria do not need
much ATP
• You depend on the
aerobic pathway
Glycolysis
• This is the first stage
for both aerobic and
anaerobic respiration
• The first energy
releasing pathways to
evolve were
anaerobic
• Glucose is converted
to pyruvate
Glycolysis
Many steps:
to convert
glucose into
pyruvate
2 ATP
invested; 4
produced
Glycolysis
• Occurs in the cytoplasm
• First step requires 2 ATP
• The next steps form 4
ATP by substrate level
phosphorylation
• This is the direct transfer
of a phosphate group
from a substrate to some
other molecule (in this
case ADP)
• Meanwhile , NAD picks
up electrons and H
liberated from the PGAL
Glycolysis
• Pyruvate and NADH
are used in the next
stage of aerobic
respiration
• If no oxygen is
present, the
pyruvate goes into
a fermentation
pathway
• Produces either
lactic acid or
alcohol (ethanol)
2nd stage ( Krebs Cycle)
• Pyruvate molecules enter
the inner compartment
of the mitochondria
• Electrons and hydrogen
carried by NADH are transferred to many
coenzymes
• A carbon is removed from each pyruvate and
joins Coenzyme A, becoming Acetyl-CoA.
• This molecule enters the Krebs cycle
Krebs Cycle
• Three functions:
• Loads electrons and hydrogen onto NAD+
and FAD, making 6NADH2 and 2FADH2
• (This is important for ATP production in the 3rd stage)
• Forms 2 ATP
• Cycles back to oxaloacetate, which is the
molecule that acetyl CoA reacts with to
start the Krebs cycle
Phosphorylation
• Substrate level: production of ATP by
transferring a phosphate group from an
intermediate directly to an ADP
• Oxidative: production of ATP from the
reactions of an electron transport chain
• Includes chemiosmosis H+ conc gradient
Substrate level phosphorylation
• An enzyme catalyses
the joining of P to
ADP
• Happens during
glycolysis and Krebs
cycle
Oxidative phosphorylation
• (Each NADH
molecule represents
stored energy that
can “fall” down the
energy gradient with
oxygen as the final
acceptor)
• Controlled release of
energy
• The ETC creates the
H+ gradient
3rd stage
• ATP formation kicks into high gear
• Uses electron transfer chains and the
enzyme ATP synthase
• NADH2 and FADH2 give up electrons and
hydrogen into the chains
• H+ is pumped out to create a
concentration gradient. When the H+ is
released, ATP is formed
Glycolysis
In the Glycolysis stage 4 ATP molecules are produced ,but 2 ATP's are used in the
process so the net yield is 2 ATP's.
In this stage 2 NAD's become NADH's.
Krebs Cycle
BEFORE the cycle 2 NADH's are created in the creation of Acetyl Coenzyme A.
IN the cycle 2 GTP's are created.
6 NADH's are created, & 2 FADH2's too.
Electron Chain
Every NADH produces 3 ATP's. We have 10 NADH's, therefore 30 ATP's are
created.
Every FADH2 produces 2 ATP's. We have 2 FADH2's, therefore 4 ATP's are
created.
Total Balance 2 ATP + 2GTP +34 ATP :38 ATP Glycolysis Krebs Cycle Electron
Chain Total
Alternative Energy Sources
• Proteins, broken down into amino acids,
can also be broken down into pyruvate
and therefore enter the Krebs cycle
• Fats, broken down into fatty acids and
glycerol, can also enter the cycle at two
different points, resulting in the same end
result