Glucose Metabolism 9.10
*
*
1. The point is to make ATP
2. Moving H-atoms…..moves energy from one
molecule to another
3. Oxidation/Reduction
OIL RIG
*Coupled Reactions
LEO GER
Oxidized?
Glucose
Reduced?
Oxygen
Redox reactions
RESPIRATION:
Process by which cells generate ATP through a series of
redox reactions. Converting food energy* (C6H12O6) into
ATP. *Need ATP for some coupled reactions…
(*Proteins, Lipids, Nucleic acids, Other Carbohydrates).
GLUCOSE: -686kcal 36-38 ATP
1.
2.
3.
4.
GLUCOSE is Broken down
5.
Occurs CONSTANTLY
Occurs in steps
Bond energy is released as ATP + HEAT
Small amounts of energy released at each step…controlled by
enzymes (reaction rate)
WHY IN STEPS?
*
Aerobic; Anaerobic
FOUR STAGES (notes)
* GLYCOLYSIS
* (FORMATION OF
ACETYL CoA)
* CITRIC ACID (KREBS)
CYCLE
* ELECTRON
TRANSPORT CHAIN
Cellular Respiration
Mitochondria/ETC
Fermentation
Cytosol/Cytoplasm
90% of ATP
*
Does it Require O2?
* Does NOT require
oxygen (Can be aerobic
or anaerobic)
Requirements?
* Requires: ATP, ADP, NAD+
* TWO PHASES:
Endergonic & Exergonic
“Investment - Capture”
* 1 Glucose
2 pyruvate (2-3C)
NET 2 ATP, 2 NADH
(2 G3P)
2 more steps: Split, Isomerase
One Step: Gain of H (NAD+ to NADH)
Powers Gain of Pi (Inorganic Phosphate)
*Inorganic phosphate in cytoplasm
*REDUCTION of NAD+ to NADH
Last 4 Steps:
Kinase…
Substrate Level Phosphorylation *
ADP to ATP
*NAD+
+ 2H
H =
e-
p+
H =
e-
p+
NAD+ + e-
=
*
Powering the Electrochemical gradient
NAD + H (e- and p+) = NADH
“Energy on Hold”
*
ATP is formed by the direct
transfer of a phosphate group
from a high-energy substrate
(Glycolysis) in an exergonic
catabolic pathway to ADP
***GLYCOLYSIS
***LATER…..
Available O 2
Purpose: Regenerates NAD+ for glycolysis
CR
*
* Muscle
Cells
* Bacteria
sugar in
milk to
Lactic acid
(*Flavors,
yogurt)
*enzyme?
*
*
Formation of Acetyl CoA from Pyruvate (3C)
Inside the Mitochondria Matrix
1.
2.
3.
“The Escort”
“The Link Reaction”
STEPS:
Remove a carboxyl group COOH (Decarboxylation, as CO2 and H)
Oxidize the 2C fragment, 2NAD+ is reduced to 2NADH- - - -
ETC
Coenzyme A ‘transport molecule’ is attached to the acetyl group
The S-C bond can be broken, Acetyl group (2C X 2) enters Krebs)
*
* TOTAL ENERGY SO FAR:
4 NADH (2 Glycolysis, 2 formation of TWO acetyl CoA)
2 ATP (From Glycolysis)
*
CITRIC ACID CYCLE
(TRICARBOXYLIC-TCA)
*
*
*
*
Mitochondrial Matrix
5 steps
TWO Cycles/Glucose
YIELD: (per Glucose)
4 CO2
2 ATP
6 NADH
2 FADH2
2. 2 CO2 removed/cycle
(4/glucose) Decarboxylation
1.
4C + 2C = 6C
Oxaloacetic
+ Acetyl =
Citric Acid
KREBS
STEPS/YIELD
4. OA4C > 6C > 5C
> 4C > 4C > OA4C
Per Glucose: 4 CO2, 2 ATP
6 NADH, 2 FADH2
“Energy On Hold”
3. Substrate level
Phosphorylation,
2 ATP/Glucose
• Protons (H+) move across I, III and IV (Each electron moves 1 H out).
• One NADH…2 e- From I to IV…6 H+ out of matrix (At V- can get 1 ATP/2 H+)
(Inner membrane NOT permeable to NADH; glycolysis count is different)
• One FADH2…2e- from II to IV…4 H+ out of matrix……eventually 2 ATP
• Electrons fall to successively lower energy levels as carriers are reduced/
oxidized…moving H+ and resulting in the oxidative phosphorylation of ATP
• Protons re-enter the matrix at V with ATP synthase enzyme; chemiosmosis
• Final electron acceptor is Oxygen, + 2P, produces H2O
(No O2, No ETC)
*
*
*NADH from Glycolysis: In Liver, Kidney, Heart- 3ATP; Skeletal muscle, brain- 2 ATP
1 mol glucose burned- 686kcal released as heat.
36-38 ATP G is ~274kcal 274/686 40% efficient
*NADH From
Glycolysis
*High
Energy;
1g fats
~2x ATP
than
1g carb.