ATP

1. How Cells make ATP:
Energy-Releasing Pathways
Chapter 8

2. How cells make Energy (ATP)?
• By cellular aerobic respiration (Catabolism/
degradation process):

3. Cellular Aerobic Respiration
• A catabolic process
• fuel (glucose) broken down to carbon dioxide and
water
• Redox reactions
• transfer electrons from glucose (oxidized) to
oxygen (reduced) to produce
• Energy released
• produces 36 to 38 ATP per glucose

4. 4 Stages of
Aerobic Respiration
• Glycolysis
• Formation of acetyl CoA
• Citric acid cycle (Krebs cycle)
• Electron transport chain (ETC) and
chemiosmosis

5. Stage 1: Glycolysis.
• Occurs in the cytosol after the glucose enters the cells through
the transporter (Carrier protein, GLUT-1)
• 1 molecule of glucose (6 atoms of carbon) is catabolised
(degraded/ spitted) into 2 molecules of Pyruvate ( with 3
Carbon each).
• Glycolysis include the energy investment and energy capture
phase
• This glycolysis step allows the net yield of 2ATPs and 2 NADH.

12. Stage 2: Formation of Acetyl CoA
• Occurs in the mitochondria after the 2 pyruvate enters the mitochondria.
• Each of the 2 pyruvate (3 carbon) will be catabolised into one acetyl coenzyme A (
2 carbon)..
• This step allows the net yield of 2 NADH and 2 CO2
• No ATP production during this phase

15. Stage 3: Citric Acid Cycle (Krebs Cycle)
• Each Acetyl coenzyme A ( 2 carbon) will
enter the Citric acid cycle, undergoing a
series of chemical reactions (using
different enzymes) with net yield of:
3 NADH, 1 FADH2, 1 ATP and 2 CO2 .
• Since 2 Acetyl coenzyme A are obtained
from 2 pyruvate, thus 2 citric acid cycle
will have a net yield of : 6 NADH, 2
FADH2, 2 ATP and 4 CO2 .

16. Nicole Ishac - LIU - Fall 2017/2018

17. Nicole Ishac - LIU - Fall 2017/2018

19. At the end of citric acid cycle:
1 Glucose has been catabolized (degraded)
into:
4 ATP ( substrate level phosphorylation), 10
NADH and 2 FADH2

20. Stage 4: Electron Transport Chain
and Chemiosmosis (oxidative
phosphorylation)
Fig. 8-10a, p. 184
Intermembrane
space
Cytosol
Outer
mitochondrial
membrane
Matrix of
mitochondrion
Inner
mitochondrial
membrane
Complex I
NADH
NAD+
FADH2
Complex
II
Complex
III
Complex
IV
1
2
ADP Pi
ATP
Complex V:
ATP
synthase
FAD+

21. Electron Transport Chain and
Chemiosmosis (oxidative phosphorylation):
• Electron Transport Chain: is a group of complexes in the inner membrane of
the mitochondria that will transport H atoms (or electrons) from NADH/
FADH2 to reduce molecular oxygen O2 ( final acceptor of electrons) forming
water.
• Chemiosmosis: protons (H+) leave the matrix to the intermembrane space
then diffuse down their gradient, back to the matrix, through the ATP
synthase forming ATP (ADP + Pi)
• Through oxidative phosphorylation:
each NADH will allow the production of 3 ATPs ( 10 NADH will produce 30
ATPs)
each FADH2 will allow the production of 2 ATPs (2 FADH2 will produce 4
ATPs)
In total, from oxidative phosphorylation, 34 ATPs are produce per each
molecule of Glucose.

23. Energy Transfer
• Electron transport chain (ETC) and chemiosmosis transfer energy
from 10 NADH and 2 FADH2 to produce 32 to 34 ATP: oxidative
phosphorylation
• 1 glucose molecule yields 36 to 38 ATP

27. Energy Transfer
• Electron transport chain (ETC) and chemiosmosis transfer energy
from 10 NADH and 2 FADH2 to produce 32 to 34 ATP: oxidative
phosphorylation
• 1 glucose molecule yields 36 to 38 ATP

28. Summary 1: Energy from Glucose

29. Summary 2: Energy from Glucose