1. Bre’ona Fergerson and Jaelon Harris
Cellular Respiration
Bre’ona Fergerson and Jaelon Harris

2. 9.1 Catabolic pathways yield energy by oxidizing organic fuels

3. To keep working a cell must regenerate the ATP that it uses
The breakdown of glucose and other organic fuels are exergonic ( accompanied by the release of energy)
What is Cellular Respiration?
It is the process in a cell’s mitochondria when food (sugar) is broken down using oxygen to produce energy. There are two main types of cellular respiration processes, aerobic and anaerobic.

4. Aerobic respiration and Anaerobic Respiration
Aerobic respiration is the consumption of oxygen as a reactant along with organic fuel.
Just think of it like this: Aerobic means “air” so this process needs air (oxygen) in order for it to work.
Equation:
Anaerobic Respiration is when a different substance is used in replace of oxygen as a reactant to harvest chemical energy. (*Also known as fermentation)
For example, sometimes a plant or an animal doesn’t have enough oxygen to respire, but they still need energy to live so they perform respiration without oxygen to produce energy.

5. Redox Reactions
In redox reactions the cell taps the energy stored in the food molecules, which causes one substance to partially or totally shift electrons to another substance. The substance that receives the electrons is reduced (becomes more negative) and the substance losing the electrons is oxidized (becomes more positive).
During cellular respiration, glucose is oxidized to CO₂ and O₂ is reduced to H₂O.
When electrons transfer from organic compounds to oxygen they lose potential energy; Electrons from the organic compound are usually first passed to NAD+ which reduces it to NADPH; the NADPH then passes the electrons to and Electron Transport Chain that connects them to O₂ in energy releasing steps. This energy is then used to make ATP.

6. Stages of Cellular Respiration: A Preview
Glycolysis-The breakdown of enzymes by enzymes releasing energy and pyruvic acid; it produces 2 molecules of ATP.
Citric Acid Cycle (Kreb’s Cycle)- the sequence of reactions in which most living cells generate energy during the process of aerobic respiration;takes place in mitochondria, consuming O₂, producing CO₂ and H₂O as waste products and converting ADP to energy-rich ATP.
Glycolysis and the citric acid cycle supply electrons (through either NADH or FADH₂) to the electron transport chain, which drives oxidative phosphorylation ( metabolic pathway that cells use to oxidize nutrients which causes the release of energy which is used to reform ATP) . Oxidative phosphorylation then generates ATP.

7. 9.2 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate

9. 9.3 The citric acid cycle completes the energy-yielding oxidation of organic molecules

10. In eukaryotic cells, the importation of the pyruvate into the mitochondrion and its conversion to acetyl CoA links glycolysis to the citric acid cycle

11. 9.4 During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis

12. Introduction
Glycolysis (Concept 9.2) and the citric acid cycle(Concept 9.3)
Glycolysis ⇒ 2 ATP (through substrate level phosphorylation)
Citric Acid Cycle ⇒ 2 ATP (through substrate level phosphorylation)
Concept 9.4: Oxidative Phosphorylation
Oxidative Phosphorylation= Electron Transport Chain + Chemiosmosis ⇒ generating 34 ATP
The most efficient and productive way in which cell harvest the energy from glucose and other nutrient
2 parts of process
Electron Transport Chain
Chemiosmosis
NADH and FADH2 serve as electron carriers
34 ATP are produced

13. Electron Transport Chain
Location
cristae= the folded inner membrane of the mitochondria (in eukaryotes)
Plasma membrane (in prokaryotes)
Series of protein are embedded in the cristae
4 large protein complex (Complex I - IV)
Cytochrome= electron carriers between ubiquinone and oxygen
Electrons are passed down from one protein complex(less electronegative) to next protein complex(more electron negative) through the series of redox reaction
As ETC progresses, reduction potentials increase until O2
Electron Transport Chain

14. The Pathway of Electron Transport
NADH and FADH2 donate their electrons to ETC
NADH (produced from Glycolysis and Citric Acid Cycle)
FADH2 (produced from Citric Acid Cycle)
FADH2 has less energy b/c it is added later in the chain
Electrons are transferred along the ETC through the series of redox reaction ⇒ released energy
Using that energy, H+ are pumped from matrix to intermembrane space ⇒ establish Proton Motive Force
Proton Motive Force= high [H+] gradient in intermembrane space and low [H+] gradient in matrix
Stored energy which can be used to make ATP through chemiosmosis
At the end of ETC, oxygen serves as final electron acceptor by converting into water
The Pathway of Electron Transport
Cytochromes are electron carriers between ubiquinone and oxygen.

15. ATP Synthase What? Protein complex ⇒ made up of multiple polypeptides
Location
the inner membrane of the Mitochondrion
4 Components
Stator
Rotor
internal rod
Knob
How it works?
Hydrogen ions flow down between the stator and rotor and causes the rotor and rod to rotate
The spinning rod causes changes in the stationary knob, activating three catalytic sites that make up the knob
It catalyzes the addition of inorganic phosphate to ADP, generating ATP

16. Chemiosmosis: The Energy-Coupling Mechanism
Chemiosmosis = Proton Motive Force ⇒ ATP(through ATP synthase)
Chemiosmosis= energy stored in form of hydrogen ion gradient across a membrane to synthesize ATP
H+ flow from high concentration gradient (intermembrane space) to low concentration gradient (matrix) through ATP synthase
ATP synthase generates 34 ATP
In total, cellular respiration generate 38 ATP
Glycolysis⇒ 2 ATP (Substrate Level Phosphorylation)
Citric Acid Cycle⇒ 2 ATP (Substrate Level Phosphorylation)
ETC + Chemiosmosis⇒ 34 ATP (Oxidative Phosphorylation)
AB_Yc
Chemiosmosis is energy stored in form of hydrogen ion gradient across a membrane to synthesize ATP

17. 9.5 Fermintation and anaerobic respiration enables cells to produce ATP without Oxygen.

18. Fermentation
At the end of Glycolysis, pyruvate, ATP, and NADH are produced
Pyruvate can undergo 2 different pathway (depending whether or not O2 is present)
O2 is present⇒ Aerobic cellular respiration
No O2 is present⇒ Fermentation
2 Types of Fermentation
Alcohol Fermentation
Lactic Acid Fermentation
Purpose: regeneration of NAD+, which can be reused in Glycolysis

19. Types of Fermentation Alcohol Fermentation(Pyruvate⇒ ethanol) 2 Steps
Pyruvate⇒ Acetaldehyde (by releasing CO2)
Acetaldehyde⇒ Ethanol (reduced by NADH)
Final electron acceptor: Acetaldehyde
Produce 2 ATP (substrate level phosphorylation)
Ex. yeast

20. Type of Fermentation 2) Lactic Acid Fermentation One Step
Pyruvate⇒ lactate (reduced by NADH)
Final electron acceptor: Pyruvate
Produce 2 ATP (substrate level Phosphorylation)
Example
Fungi
bacteria (used to make cheese and yogurt)
human muscle cells

21. Aerobic Respiration Fermentation Environment Environment O2 is present
Final Electron Acceptor
Oxygen
Net ATP Production (38 ATP)
Glycolysis⇒ 2 ATP
Citric Acid Cycle⇒ 2 ATP
ETC + Chemiosmosis⇒ 34 ATP
Types of organism that use Aerobic Respiration
Obligate Aerobic= organism that can survive with O2
Fermentation
Environment
No O2
Final electron acceptor
Organic molecule (Pyruvate or Acetaldehyde)
Net ATP Production (4 ATP)
2 ATP (Glycolysis)
2 ATP (Fermentation)
Type of Organism that use fermentation
Obligate Anaerobe= organism that cannot survive in the presence of O2
Common pathway
Glycolysis (to oxidize glucose)
Type of Organism that can use either pathway
Facultative Anaerobe= organism that can use either use either fermentation or aerobic respiration

22. 9.6 Glycolysis and the citric acid cycle connect to many other metabolic pathways

23. Catabolic Pathway
Breakdown complex molecules into monomers(used as fuels⇒ generate ATP)
Carbohydrates
(enter) Glycolysis and Citric Acid Cycle
Proteins⇒ Amino acid ⇒ Deamination(removal of amino group) need to occur first
Converted into intermediates of Glycolysis and Citric Acid Cycle
Fat (broken down into) ⇒ Glycerol + Fatty Acid
Glycerol(converted into)⇒Glyceraldehyde-3-Phosphate (intermediate of Glycolysis)
Fatty Acid ⇒ beta oxidation(breakdown FA into acetyl CoA) ⇒ (enter) Citric Acid Cycle
(produce) NADH and FADH2⇒ generate ATP (through Oxidative Phosphorylation)

24. Anabolic Pathway Monomers⇒ Complex molecules (consume ATP)
Amino Acid⇒ Protein (build up muscle)
Pyruvate⇒ Glucose
Acetyl CoA⇒ Fatty Acid
Connection between Glycolysis and Citric Acid Cycle
Dihydroxyacetone Phosphate (from glycolysis) ⇒ (converted into) precursor of fat ⇒ used in Citric Acid Cycle

25. Feedback Mechanisms⇒ Regulation
Feedback Inhibition= end product of pathway inhibits the enzyme that is used for early reaction step
Ex. increase ATP⇒ slow down respiration; Decrease ATP⇒ speed up respiration (by regulating Enzyme activity)
Enzyme pathway regulates: Phosphofructokinase(enzyme for step 2 glycolysis)
Allosteric enzyme(has sites for specific activator and inhibitor to bind)
Activator: AMP⇒ speed up Glycolysis
Inhibitor: ATP and Citrate⇒ slow down Glycolysis

26. Chapter Question What is the reducing agent in the following reaction?
The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the?
What metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?
In mitochondria, exergonic redox reactions do what?
The final electron acceptor of the electron transport chains of mitochondria, which of the following changes occur?
When electrons flow along the electron transport chains of mitochondria, what changes occur?
Cells do not catabolize carbon dioxide because?
Which of the following is a true distinction between fermentation and cellular respiration
Most CO2 from catabolism is released during?

27. Answers
NADPH
Hᐩ concentration across the membrane holding ATP synthase
Glycolysis
Provide the energy that establishes the proton gradient.
Oxygen
The pH of the matrix increases
CO₂ is already completely oxidized
NADH is oxidized by the electron transport chain in respiration only
The citric acid cycle