Download notes howard chpt 9 respiration

CHAPTER 9 CELLULAR
RESPIRATION: HARVESTING
CHEMICAL ENERGY
Section A: The Principles of Energy Harvest
1. Cellular respiration and fermentation are catabolic, energy-yielding
pathways
2. Cells recycle the ATP they use for work
3. Redox reactions release energy when electrons move closer to
electronegative atoms
4. Electrons “fall” from organic molecules to oxygen during cellular
respiration
5. The “fall” of electrons during respiration is stepwise, via NAD+ and an
electron transport chain
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
I. Introduction to cellular respiration
Living is work.
• A. Function of Cellular Resp?
• To produce ATP from glucose for cellular
functions
Fig. 9.1
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Metabolic pathways that release the energy
stored in complex organic molecules are
catabolic (break down of complex mlcls)
• B. Types of catabolic pathways
– 1. fermentation, anaerobic respiration (w/out
oxygen) creates only a small amt of ATP, but
purpose is to allow resp. to continue with limited
O2
• a. alcohol - produced by bacteria & yeast & some
plants
• b. lactic acid – produced by animals in low oxygen
situation – removed from cells to liver (can then be
removed from body or recycled back into glucose is
enough ATP is present
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

2. A more efficient and widespread catabolic process, cellular
respiration, uses oxygen as a reactant to complete the
breakdown of a variety of organic molecules. Produces much
ATP
C. E flow in the ecosystem
Light E > photosynthesis<> respiration> heat
• D. Cellular Resp Equation (combustion rxn)
– C6H12O6 + 6O2 -> 6CO2 + 6H2O + Energy (ATP + heat)
– (can be other org cmpds besides glucose)
• Carbohydrates, fats, and proteins can all be used
as the fuel, but it is traditional to start learning
with glucose.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• An electron looses energy as it shifts from a less
electronegative atom to a more electronegative
one.
• A redox reaction that relocates electrons closer
to oxygen releases chemical energy that can do
work.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
E. The process of cellular respiration
creates ATP molecules. They are
created by the overal “fall” of
electrons!
• In cellular respiration, glucose and other fuel
molecules are oxidized, releasing energy.
• Glucose is oxidized, oxygen is reduced, and
electrons loose potential energy. that can be
used elsewhere.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
II. Where does cellular respiration
occur? cytoplasm & mitochondria
•
•
•
•
A. 3 metabolic stages of cell resp
1. glycolysis -- cytoplasm
2. the Krebs cycle– mitochondrial matrix
3. electron transport chain - ETC – mitochondrial
cristae
Fig. 9.6
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• p.160
III. Mitochondria Review
• A. Mitochondria has 2 layers of membranes
• B. endosymbiotic theory – mito. (&
chloroplasts) have their own DNA ergo they
must have been prokaryotic endosymbionts
(living w/in another organism) both (mito &
cell) became dependent on each other
….evolution p.549-550
• C. mitochondrial structure
– 1. cristae – inner membrane foldings
– 2. matrix – area enclosed by cristae
• 3. the inner membrane is highly folded to
increase surface area
• 4. increased area allows for an ion gradient
– a. ions (H+) are pumped back & forth across the
membrane to create ion gradients – these
gradients are used to phosphorylate (add a
phosphate to) ADP mlcls
– (change ADP into ATP)
IV. Glycolysis – the 1st step of cell resp
• A. Quick over view of glycolysis
– 1. start with: glucose
– 2. end with: 2 pyruvates
B. Glycolysis = sugar splitting
• 1. glucose starts as a 6-Carbon sugar
• 2. & is split into 2 3-Carbon sugars
– a. the new sugars are oxidized (LEO goes GER) & rearranged to form
2 mlcls of pyruvate – in the process several e- are released an
harvested by:
1) NAD+ = nicotinamide adenine dinucleotide– this gets electrons
from food & is thus reduced to
2) NADH – oxidized from of NAD -- this is what carries the e- for
the ETC
– LEO goes GER = lose e- oxidized & gain e- reduced
• 3. 10 steps in glycolysis each w/it’s own
enzyme
• 4. this phase of cell resp requires ATP (2 of
them)
• 5. impt stuff produced during glycolysis
– a. ATPs – 4
– b. NADHs – 2
– c. H2O (waste)- 2
• 6. oxygen not required (anaerobic) for
glycolysis (this indicates this process probably
evolved before the ETC & kreb’s cycle).
However, if there is no oxygen present at all
then the cell cannot go into the next stip of
cell resp.
– a. if no O2 --- process is fermentation (lactic acid
production in animals)
– b. at end of fermentation cell will produce alcohol
or lactic acid
• c. if oxygen is present 2 molecules of pyruvate
move into the mitochondria & begin the
Kreb’s cycle
• (the NADH mlcls will be saved for the ETC)
V. Krebs Cycle (aka citric acid cycle –
because citrate is the 1st product formed)
• A. O2 must be present
• B. 2 pyruvate mlcls move into the mitochondrial
matrix
• C. Krebs has 8 steps each w/ its own enzymes
• D. 2 pyruvates enter cycle & are rearranged
• E. output of 1 turn of the Krebs cycle
(remember there are 2 mlcls of pyruvate for
each mlcl of glucose)
– 1. CO2 = 2 (x2)
– 2. NADH = 3 (x2)
– 3. ATP = 1 (x2)
– 4. FADH2 = 1 (x2)
(flavin adenine dinucleotide – another e- carrier)
• F. NADH & FADH2 (stores the E from breaking
down glucose so far) –will move into the 3rd
stage of cell resp.
VI. Electron Transport Chain
• A. found in cristae membrane of mito.
• B. It’s an actual chain of protein mlcls!!!!
• C. NADH will “drop off” its electrons to the 1st
mlcls in the chain FMN (flavin mononucleotide)
– 1. e- is passed on from protein to protein
– 2. it’s finally passed on to an oxygen which bonds toa
couple of hydrogen ions to make water
– 3. for every 1NADH you make 2 mlcls of water
– 4. for every 1 NADH you make 3 mlcls of ATP
• D. FADH – follows a similar pattern but drops
its e- at a “lower” part of the chain thus
transferring less energy (1/3 less)
– 1. for every 1 FADH2 you get 2 ATPs
E. No ATP is made directly by the ETC – its job
is to move electrons to oxygen slowly to
release E in manageable amts
Remember, you’re basically
carrying out a combustion rxn
INSIDE of a cell --- the E has to be
controlled so you don’t damage or
kill the cell in the process!
• F. Then how do we make ATP? chemiosmosis
VII. Chemiosmosis
• A. occurs during ETC!!!
• B. ATP synthase- enzyme used to catalyze
ADP + Pi
ATP
• C. ATP synthase uses the E of an ion gradient
to make ATP mlcls
• D. How does the
mitochondrial membrane
generate & maintain a H+
gradient?
– 1. function of the ETC
• a. as e- fall down the ETC, H+
ions are pumped into the space
between the membranes
(towards the outer membrane)
of the mitochondria
• b. the H+ ions naturally diffuse (osmosis) back
to the matrix and the ONLY way back in is
through the ATP synthase protein
• c. the ATP synthase can use the movement of
H+ ions to fuel oxidative phosphorylation of
ADP into ATP
• converting KE to PE (chemical energy)
• d. the coupling of the ETC & oxidative
phosphorylation is called chemiosmosis
• 2. In general, chemiosmosis is an energycoupling mechanism that uses energy stored
in the form of an H+ gradient across a
membrane to drive cellular work
• 3. chemiosmosis occurs in other locations!
– a. plants – photosynthesis
– b. bacteria - fermentation