Stage 3 Digestion
Citric Acid Cycle Overview
Warm-up
1.
2.
3.
4.
Draw the entry level Rx of Glycolysis.
What’s the enzyme named catalyzing it?
Name the inhibitor of that enzyme.
How many ATP are made?
Pyruvate
The 3 Uses of Pyruvate
it is turned into
Product
Acetyl CoA
Ethanol
Lactic Acid
condition
Aerobic
Anaerobic
Anaerobic
organism
Any eukaryotic cell
Yeast
Muscle cells
organell
Mitochondria
Cytosol
Cytosol
purpose
Endoxidation
Making more
NADH, ATP
Regeneration of
NAD for
continued
glycolysis
Regeneration of
NAD for
continued
glycolysis
Two types of Fermentation:
A. Lactic Acid - Muscles
• Produces no CO2
• Lactic Acid is degraded in liver ≈3-5 hrs
• Does not produce post-workout muscle
pain!!!
B. Alcoholic Fermentation in Yeast
* Produces Ethanol and CO2
Endoxidation
• Needs O2 (aerobic) and Mitochondria to
completely harvest the chemical energy left
in pyruvate
• Pyruvate is converted to Acetyl CoA, loss of
1st Carbon as CO2
• Enters
Mitochondria
Mitochondria
• Eukaryotic cell organelle
• Has two membranes (like nucleus)
• Outer membrane believed to originate
from endosymbiontic theory:
mitochondria were once independent
organisms:
• Has it’s own DNA and ribosomes
• Inherited from the mother
Structure of Mitochondria
Endosymbiotic Theory
• Endosymbiosis
• animation
Citric Acid Cycle (Krebs C)
• Central pathway for metabolizing carbs, lipids
and proteins
• Location: Mitochondrial Matrix
• Has two parts: Decarboxylation and
Regeneration
• Components are natural acids: Citric-, Malic,
Oxalic-, Fumaric acid
• Acids in fruits/vegetables are metabolized in the
citric acid cycle
Warm-up
1. Where: Glycolysis or Krebs Cycle would you
find this molecule?
2. What’s its name?
3. What do all molecules in the Krebs Cycle
have in common?
Stage 4 Digestion: Electron
Transport Chain and ATP
Synthesis
Electron Transport Chain- ETC
• Interconnected proteins (Cytochromes,
Ferroproteins, CoQ…. ) labeled
• Complex I-V
• embedded in the
inner
mitochondrial
membrane
A. Unloading of NADH/FADH
• NADH and FADH (Complex II) molecules
go to Complex I – Dehydrogenase and
unload the H
• Unloaded NAD/FAD go back to Krebs
Cycle/Glycolysis
• H is separated into high energy e- and H+
B. Proton Pumps
• High energy e- passes through
complexes I,II, III, IV – proton pumps that
use e- energy to pump H+ into
mitochondrial intermembrane space
• This creates a 100 x H+ difference
between matrix and intermembrane space:
• H+ gradient: Chemiosmosis
C. The Role of Oxygen
• Complex IV: energy of e- has been used
up
• Oxygen (very e-negative) absorbs e- on
the matrix side – where it is neutralized by
H+ gradient forming water
½ O2 + 2e- + 2H+
H 2O
Oxygen is the final electron
acceptor of aerobic cellular
respiration – this is why you
breathe!!!
D. ATP Synthesis
• Harvesting energy of the H+ gradient
• Works like a water wheel
ATP Synthase: Complex V
• allows H+ gradient to rush through using
energy to make ATP
ADP + P+ ENERGY
ATP
ADP + P
ATP
•
•
•
•
•
animated ATP synthase
Electron Transport Chain
Cellular respiration all
Glycolyis
Krebs cycle
ATP Conversions
• 1 cytosolic NADH = 2 ATP
• 1 mitochondrial NADH = 3 ATP
• 1 mitochondrial FADH = 2 ATP
Net ATP from 1 Glucose
• 2 ATP (G)
• 2 NADH2 (G) = 2 FADH2 (transport)
• 2NADH2 (K prep)
• 2 x 3 NADH2 (K)
• 2 x FADH2
(K)
• 2 x 1 GTP
(K)
Total ATP
2
4
4
18
4
2__
34
Location?Location?Location?
In which cellular compartment houses
the…
a. Glycolysis
b. Citric Acid Cycle
c. Electron Transport Chain
d. Hydrogen Ion gradient
e. ATPsynthase
Warm-up
1. Write the balanced net reaction of
anaerobic cellular respiration of 1 mole of
Glucose to Lactic Acid.
2. Write the balanced net reaction of aerobic
cellular respiration of 1 mole of Glucose.
3. Give two reasons why cells convert
Pyruvate to Lactic acid during temporary
anaerobia.
Warm-up
• The enthalpy for I mole of ATP is -30 kJ.
• The enthalpy of combustion for 1 mole of
glucose is -2808 kJ.
1. Calculate the efficiency of aerobic cellular
respiration by multiplying # ATP with the enthalpy
then comparing it to the combustion enthalpy. How
much chemical energy is captured and how much
energy is lost?
2. According to the law of conservation of energy,
energy cannot be created or destroyed, only
transferred. What happened to the the energy
difference?
Lipid Metabolism
• Cytoplasm: lipase separates Glycerol and
Fatty Acids
• Glycerol (C3) is converted to Pyruvate (C3):
yields NADH
• Fatty Acids are transported into
Mitochondria for β-Oxidation
• chopped into 2 carbon molecules to make
Acetyl-CoA (Krebs Cycle)
• Yield: 1 NADH + 1 FADH/chop
Amino Acids
Liver: Removal of amino group as NH3
(ammonia)
Ammonia is toxic, reacts with CO2 to form
urea, secreted as liquid waste: kidneys
O
2NH3 + CO2
NH2-C-NH2 + H2O
Ammonia
Urea
Carbon skeleton of AA
• AA skeletons with 2 C → Acetyl
• AA skeletons with 3 C →Pyruvate
• AA skeletons with 4 C → Succinate
Fumarate, Malate, Oxaloacetate
• AA skeletons with 5 C→ α-Ketoglutarate