1. Biol 105 Lecture 6 Read Chapter 3 (pages 63 – 69)
Cellular Metabolism
Biol 105
Lecture 6
Read Chapter 3 (pages 63 – 69)

2. Metabolism
Consists of all of the chemical reactions that take place in a cell

3. Metabolism Animation—Breaking Down Glucose For Energy

4. Cellular Metabolism
Aerobic cellular respiration – requires oxygen, produces carbon dioxide
Anaerobic Fermentation – does not require oxygen

5. Summary of Cellular Respiration
Electrons
transferred
by NADH
Cytoplasm
Blood
vessel
Electrons
transferred
by NADH
Glucose
Plasma
membrane
Electrons
transferred
by NADH
and FADH2
Carrier
protein
Citric
Acid
Cycle
Electron
Transport
Chain
Glycolysis
Transition
Reaction
glucose pyruvate
Oxygen
Mitochondrion
Extracellular fluid
+2 ATP
+2 ATP
+32 ATP 
36 ATP
Figure 3.27

6. Aerobic Cellular respiration
In aerobic cellular respiration cells take in sugar (glucose) and breaks it down to into carbon dioxide and water, this requires oxygen.
This process produces energy in the form of ATP
C6H12O6 + 6O2 → 6CO2 +6H2O + Energy

7. Aerobic Cellular respiration
There are four steps of aerobic cellular respiration:
Glycolysis
Transition Reaction
Citric Acid Cycle (Krebs Cycle)
Electron Transport Chain

9. Figure: 07-04
Title: Overview of Energy Harvesting
Caption: (a) In metaphorical terms. (b) In schematic terms.

10. NADH and FADH2 are important carriers of electrons
Figure: 07-03
Title: The Electron Carrier NAD+
Caption: In its unloaded form (NAD+) and its loaded form (NADH), this molecule is a critical player in energy transfer, picking up energetic electrons from food and transferring them to later stages of respiration.
NADH and FADH2 are important carriers of electrons

11. Cellular Respiration - Glycolysis
Phase 1: Glycolysis
Occurs in the cytoplasm
Splits one glucose into two pyruvate molecules
Generates a net gain of 2 ATP and 2 NADH molecules
Does not require oxygen

12. Cellular Respiration - Glycolysis
Starts with glucose
Ends with 2 ATP, 2 NADH, 2 pyruvate

13. Glycolysis Figure 3.23 Glycolysis (in cytoplasm) Cytoplasm
During the first steps,
two molecules of ATP are
consumed in preparing
glucose for splitting.
Glucose
2 ATP
During the remaining
steps, four molecules
of ATP are produced.
Energy-
investment
phase
2 ADP
4 ADP
4 ATP
The two molecules of
pyruvate then diffuse
from the cytoplasm into
the inner compartment
of the mitochondrion,
where they pass through
a few preparatory steps
(the transition reaction)
before entering the citric
acid cycle.
Energy-
yielding
phase
2 NAD+
2 NADH
Two molecules of nicotine
adenine dinucleotide
(NADH), a carrier of
high-energy electrons,
also are produced.
2 Pyruvate
Figure 3.23

14. In Cytosol

15. Cellular Respiration – Transition Reaction
Phase 2: Transition reaction
Occurs within the mitochondria
Coenzyme A combines with pyruvate and CO2 is removed from each pyruvate
Forms 2 acetyl CoA molecules
Produces 2 NADH

16. Transition Reaction Start with: End with:
2 pyruvate (3 carbon molecules)
2 Coenzyme A
End with:
2 CO2
2 NADH
2 Acetyl CoA (2 carbon molecule)

17. Transition Reaction Figure 3.24 Transition Reaction (in mitochondrion)
Pyruvate (from glycolysis)
One carbon (in the form
of CO2) is removed
from pyruvate.
A molecule of NADH is
formed when NAD+
gains two electrons
and one proton.
CO2
NAD+
NADH
Coenzyme A
(electron passes
to electron
transport chain)
The two-carbon
molecule, called
an acetyl group,
binds to
coenzyme A
(CoA), forming
acetyl CoA,
which enters the
citric acid cycle.
CoA
Acetyl CoA
Citric Acid Cycle
Figure 3.24

18. Cellular Respiration – Citric acid cycle
Phase 3: Citric acid cycle
Occurs in the mitochondria
Acetyl CoA enters the citric acid cycle
Releases 2 ATP, 2 FADH2 and 6 NADH, 4 CO2 molecules
Requires oxygen

19. Citric Acid Cycle Also called the Krebs Cycle Start with 2 Acetyl CoA
End with:
4 CO2
2 ATP
6 NADH and 2 FADH2

20. Citric Acid Cycle Figure 3.25 Citric Acid Cycle (in mitochondrion)
Acetyl CoA, the
two-carbon compound
formed during the
transition reaction,
enters the citric acid
cycle.
The citric acid cycle also
yields several molecules of
FADH2 and NADH, carriers of
high-energy electrons that
enter the electron transport
chain.
Acetyl CoA
CoA
CoA
Oxaloacetate
Citrate
NADH
CO2
leaves
cycle
NAD+
NAD+
Malate
Citric Acid Cycle
FADH2
NADH
ATP
ADP + Pi
FAD
-Ketoglutarate
Succinate
CO2 leaves cycle
NAD+
NADH
The citric acid cycle yields
One ATP from each acetyl
CoA that enters the cycle,
for a net gain of two ATP.
Figure 3.25

21. Cellular Respiration Phase 4: Electron transport chain
Electrons of FADH2 and NADH are transferred from one protein to another, until they reach oxygen
Releases energy that results in 32 ATP
Requires oxygen

22. The Big Pay Off – Electron Transport Chain
NADH and FADH2 are important carriers of electrons
They donate electrons to the electron transport chain
At the end of the chain oxygen accepts the electrons.

23. The Big Pay Off – Electron Transport Chain
Electron Transport Chain produces ATP using the ATP synthase protein molecule
The Electron Transport Chain produces 32 ATP

24. Electron Transport Chain
Electron Transport Chain (inner membrane of mitochondrion)
The molecules of NADH and
FADH2 produced by earlier phases
of cellular respiration pass their
electrons to a series of protein
molecules embedded in the inner
membrane of the mitochondrion.
High
NADH
NAD+
As the electrons are transferred
from one protein to the next,
energy is released and used to
make ATP.
2e–
FADH2
2e–
Membrane
proteins
Potential energy
FAD
Eventually, the
electrons are
passed to oxygen,
which combines
with two hydrogens
to form water.
2e–
2e–
2e–
H2O
Low
2 H+ + 1 2 O2
Energy released is used
for synthesis of ATP
Figure 3.26

25. Figure: 07-09
Title: The Electron Transport Chain (ETC)
Caption: The movement of electrons through the ETC powers the process that provides the bulk of the ATP yield in respiration. The electrons carried by NADH and FADH2 are released into the ETC and transported along its chain of molecules. The movement of electrons along the chain releases enough energy to power the pumping of hydrogen ions (H+) across the membrane into the outer compartment of the mitochondrion. It is the subsequent energetic “fall” of the H+ ions back into the inner compartment that drives the synthesis of ATP molecules by the enzyme ATP synthase.

26. Figure: 07-09
Title: The Electron Transport Chain (ETC)
Caption: The movement of electrons through the ETC powers the process that provides the bulk of the ATP yield in respiration. The electrons carried by NADH and FADH2 are released into the ETC and transported along its chain of molecules. The movement of electrons along the chain releases enough energy to power the pumping of hydrogen ions (H+) across the membrane into the outer compartment of the mitochondrion. It is the subsequent energetic “fall” of the H+ ions back into the inner compartment that drives the synthesis of ATP molecules by the enzyme ATP synthase.

27. How is ATP made using the ETC
In the mitochondria, the NADH and FADH donate electrons to the electron transport chain (ETC)
Oxygen is the final electron acceptor from the ETC
The ETC uses the energy from the electrons to transport H+ against the concentration gradient, transporting them from the lumen of the mitochondria to the intermembrane space.

28. How is ATP made using the ETC
The ATPsynthase transports the H+ back to the lumen of the mitochondria.
The H+ falling through the ATPsynthase provides the energy for the ATPsynthase to catalyze the reaction of ADP + P →ATP

29. Summary of Cellular Respiration
TABLE 3.5
REVIEW OF CELLULAR RESPIRATION
Table 3.5

30. Summary of Cellular Respiration
One molecule of glucose is broken down and 36 ATP are generated.
Oxygen is used by the electron transport chain – it accepts electrons from the ETC
Carbon dioxide is produced by the Transition Reaction and the Citric acid cycle

31. Summary of Cellular Respiration
Glycolysis: Starts the process by taking in glucose. Produces 2 ATP
The Transition Reaction produces CO2 and NADH
The Citric acid cycle: Produces 2 ATP but also produces lots of NADH and FADH2. Produces CO2.

32. Summary of Cellular Respiration
Electron transport chain
Takes electrons from NADH and FADH2 and uses them to produce ATP using the ATP synthase molecule.
Requires oxygen. Oxygen is the final electron acceptor on the electron transport chain
One glucose can produce a total of 36 ATP

33. Fats and proteins enter the process at different steps
Complex Carbohydrates must first be broken down into glucose before entering glycolysis
Fats and proteins enter the process at different steps
Figure: 07-10
Title: Many Respiratory Pathways
Caption: Glucose is not the only starting material for cellular respiration. Other carbohydrates, proteins, and fats can also be used as fuel for cellular respiration. These reactants enter the process at different stages.

34. Oxygen
Cellular respiration requires oxygen – this is aerobic cellular respiration
Sometimes organisms, including humans, need to produce energy without using oxygen
When you need energy quick, or if there is not enough O2 then the cell will use only glycolysis

35. Anaerobic Fermentation
Breakdown of glucose without oxygen
Takes place entirely in the cytoplasm
It is very inefficient - results in only two ATP

36. Anaerobic Fermentation
Anaerobic Fermentation: Anaerobic pathway to produce ATP from glycolysis without the Krebs and ETC

37. Fermentation in Animals
When cells need energy quick they will use this pathway for a short time
2 pyruvic acid + 2 NADH → 2 lactate and 2 NAD+
End result = lactate and 2 ATP produced (from glycolysis) and NAD+ is regenerated

38. Figure: 03-32
Title:
Two types of fermentation.
Caption:
Fermentation occurs in the cytoplasm, does not require oxygen, and yields only 2 molecules of ATP per molecule of glucose.

39. What is the starting molecule of glycolysis?
Acetyl CoA
Protein
Glucose
Pyruvate (pyruvic acid)

40. Which stage produces CO2
Glycolysis
Electron Transport Chain
Transition
Citric acid Cycle
Both 3 and 4

41. Which stage uses O2
Glycolysis
Krebs Cycle
Electron Transport Chain

42. Which stage produces the most NADHs
Glycolysis
Krebs Cycle
Electron Transport Chain

43. Which stage produces the most ATP
Glycolysis
Krebs Cycle
Electron Transport Chain

44. Important Concepts Read Ch 4
What is Cellular respiration and Anaerobic Fermentation and what are the differences between them.
What are the four steps of aerobic cellular respiration, what happens in each step, what are the starting molecules, what comes out of each step, where in the cell does each step occur, how many ATP and NADH/FADH2 are produced in each step.

45. Important Concepts
Describe in detail how is ATP made using the electron transport chain
What is the role of ATPsynthase, H+, O2, NADH and FADH2 and the electron transport chain in ATP production?
Know the overall picture of cellular respiration (summary slides)

46. Important Concepts
What is the role of oxygen in cellular respiration, what steps produce carbon dioxide
What is anaerobic fermentation, what steps are involved in fermentation, what end products are produced in humans, is oxygen required? when is it used.

47. Definitions
Aerobic cellular respiration, anaerobic fermentation , ATP synthase, metabolism