Download Outline -- cellular respiration, chap 9

Respiration
Biology 520 Notes
preview:
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all organisms need energy for life
plants convert sunlight to chemical energy, and store it as food
animals get food (energy) by eating.
in all organisms energy is released and made
available for work by respiration
I. ATP - the cellular "energy currency" (fig. 8-1, p. 226)
A. All creatures need energy
1. what is energy? – 1st and 2nd law
2. plants get energy by converting sunlight to chemical energy.
3. animals get energy by eating.
4. all creatures must break down energy into small packets that
can be used a little bit at a time. They break down food first to
sugar; then they break down sugar into ATP
consider the following analogy:
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if you had to pay for everything with $100 bills, and no change was available, what
problem would you encounter?
what if you had to buy small pieces of candy with $10 bills?
The cell has this sort of problem. Food contains energy in large amounts – like $100 bills. It must
be broken up into smaller "bills" so that it can be used a little bit at a time.
In our analogy, use the following comparisons:
molecule
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starch/glycogen
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money
$100 (large amount)
sugar (glucose)
$10 (medium amount)
ATP
$1 (small amount)
(there are hundreds of glucose molecules in one starch or glycogen chain. One sugar molecule
can be turned into 38 ATP molecules)
II. Respiration | Overview fig 9-2 p. 252
A. Glycolysis – see fig. 9-4, p. 255 | animation
a. sugar is broken into 2 3-carbon molecules in 10 steps
b. happens in the cytoplasm
c. net production of 2 ATP (4 are made but 2 are used up)
d. some sugar energy is transferred to NADH
B. Krebs cycle (citric acid cycle) – see fig. 9-5, p. 257 | animation
a. happens in the mitochondria
b. a cycle of 9 reactions (compare to Calvin cycle); runs twice for
each glucose molecule that started glycolysis
c. in a step prior to Krebs, one CO2 is removed and one NADH
produced
d. the other 2 carbons (a 2-carbon molecule) enter the Krebs cycle.
e. 2 CO2 are removed for each cycle
f. 2 ATP are produced
g. 3 NADH and 1 FADH2 (similar molecule) are produced for
each cycle.
C. electron transport (oxidative phosphorylation) – see fig. 9-6, p. 259 | animation
a. happens in the mitochondria inner membrane.
b. energy from NADH and FADH used to establish a proton
gradient - i.e., to concentrate protons (H+) on one side of the
mitochondrial inner membrane.
c. protons cannot cross the membrane on their own (charged). As
they cross back toward lesser concentration, the energy released is
used to make ATP
d. electrons are passed along a chain of molecules (similar to
photosynthesis). The final electron acceptor is O2, which combines
with hydrogen to form water. This is why you need to breathe
oxygen!
D. summary of ATP production totals - see also fig. 9-7, p. 260
1. 3 ATP for each NADH and 2 for each FADH. This gives us:
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22 ATP from Krebs (6x3 + 2x2)
6 ATP from glycolysis
6 from step between glycolysis and Krebs
2. 2 ATP made directly in glycolysis
3. 2 ATP made directly in Krebs
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total = 38 ATP per glucose molecule. In eukaryotic cells 2 ATP are also
used to transport the products of glycolysis into the mitochondria; this
gives us a total of 36 ATP.
D. Anaerobic respiration (p. 262-265, fig. 9-8)
1. anaerobic respiration can have two by-products: alcohol or lactic
acid
2. fermentation takes place in yeast and similar organisms
3. anaerobic respiration can also happen in animal muscle cells
4. in anaerobic respiration, there is no Krebs cycle or electron
transport; as a result, only 2 ATP are produced per sugar molecule.
The by-product is made in the process of changing NADH back to
NAD+, which would otherwise be used up
F. Getting energy from other molecules
1. Other sugars can be turned into glucose or intermediate
compounds of glycolysis
2. Fats and amino acids can be modified and then enter the Krebs
cycle
G. Creatine supplements - p. 261
*to review, check out this comparison of photosynthesis and respiration
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