COMPLETING THE CELLULAR
RESPIRATION PICTURE
The ETC
LEARNING GOALS
• I will be able to explain how electrons aid in the synthesis of ATP.
• I will understand the final products of aerobic respiration.
3. ETC
• Purpose: to use the energy stored in the H+ ions to
resynthesize ATP
• at this point, all the carbon from the original glucose
molecule has been expelled as CO2 (2 during conversion
to acetyl-CoA, 4 during Kreb’s)
• thus, the only remaining part of glucose are the H’s that
have been removed along the way and carried (by NAD
and FAD) to the mitochondria
BACKGROUND INFO: MITOCHONDRIAL
STRUCTURE
• to understand the ETC,
we need to understand
the unique structure of
the mitochondria:
• 2 membranes (inner &
outer) separate the
MATRIX from the “inter
membrane space”)
DEFINITIONS:
OXIDATION VS. REDUCTION
• oxidization - when a molecule
loses hydrogens or electrons (and
the E! they carry)
• reduction - when a molecule
gains hydrogens or electrons (and
the E! they carry)
• example: NAD and FAD are
reduced during the Krebs, citrate
is oxidized
OIL RIG
HYDROGEN CARRIERS VS. ELECTRON
CARRIERS
• hydrogen carriers - transport
H’s (which contain energy in
the form of electrons) e.g.
NAD & FAD
• electron carriers/protein
complexes - transport
electrons (removed from
the H atoms)
STEPS OF THE ETC
1. NADH+H and FADH2 lose their H atoms inside the mitochondrial
matrix (i.e., NADH+H & FADH2 become “oxidized”)
2. The electrons from the H atoms are removed and passed to the first of
3 electron carriers. The 3 electron carriers have slightly different E!
levels (1st has the highest)
3. As the electrons are passed from one electron carrier to the next, the
‘extra’ E! is released. This energy is used to ‘pump’ the remaining H+
protons across the inner membrane.
as e-’s are passed down
the chain, the E! released
moves H+ ions across
the inner membrane
NOTE: FAD doesn’t
drop off its e-’s until
2nd carrier, which explains
why it’s not quite as good
at making ATP
4. The H+ protons start to build up between the inner & outer
membrane, creating an H+ gradient (i.e., H+ protons want
to move from area of high concentration to low)
5. Since inner membrane is impermeable, H+ protons can
only pass through a specialized channel, called ATP
synthase
6. As the H+ protons pass, they provide the E! required to fuse
ADP and Pi back together
H+ gradient forms, so
H+ ions want to move to
area of lower
concentration
as H+ pass through
ATP Synthase, it
spins, forcing ADP &
phosphate back
together
7. Once back in the matrix, the H+ protons recombine with their electrons
and are eventually combined with oxygen (to make water) (i.e., oxygen
becomes “reduced”)
•
this explains why we need to breathe in oxygen when we exercise (no oxygen =
no H+ ‘pick up’ = no gradient = no ETC)
H+ combines with oxygen
to make water
PROCESS
NADH+H
FADH2
(3 ATP per) (2 ATP/per)
ATP
GLYCOLYSIS
2
-
2
ACETYL-COA
CONVERSION
2
-
0
KREBS
CYCLE
6
2
2
TOTAL
10 X 3 ATP
2 X 2 ATP
TOTAL ATP
PER
GLUCOSE
30
4
4
LEARNING GOALS
• I will be able to explain how electrons aid in the synthesis of ATP.
• I will understand the final products of aerobic respiration.