7.

Phosphoglycerate Kinase: 1,3-

Glycolysis Reviewer Bisphosphoglycerate → 3-Phosphoglycerate
(produces 1 ATP)
Introduction to Energy 8. Phosphoglycerate Mutase: 3-Phosphoglycerate →
- Energy Source: Originates from the sun, transferred 2-Phosphoglycerate
to Earth via photosynthesis in plants. 9. Enolase: 2-Phosphoglycerate →
- Photosynthesis: Plants convert sunlight, carbon Phosphoenolpyruvate
dioxide, and water into glucose. 10. Pyruvate Kinase: Phosphoenolpyruvate →
- Glucose Utilization: Our bodies use glucose from Pyruvate (produces 1 ATP)
plants as a primary energy source through cellular
respiration. Key Points to Remember
- Initial Investment: 2 ATP molecules are used in the
Cellular Respiration preparatory phase.
- Definition: The process of breaking down glucose to - ATP Production: 4 ATP molecules are produced in
generate energy, carbon dioxide, and water. the payoff phase (net gain of 2 ATP).
- Main Pathways: - NADH Production: NAD+ is reduced to NADH
1. Glycolysis during the conversion of GADP to 1,3-
2. Citric Acid Cycle (Krebs Cycle) bisphosphoglycerate.
3. Oxidative Phosphorylation
- Importance: Facilitates the production of ATP, the Summary
energy currency of the cell. - End Product: Glycolysis results in 2 molecules of
pyruvate.
Glycolysis Overview - Next Steps: Pyruvate enters the citric acid cycle if
- Location: Occurs in the cytoplasm of the cell. oxygen is present.
- Nature: Anaerobic process (does not require
oxygen). Aerobic and Anaerobic Respiration
- Output: Converts one molecule of glucose into two
molecules of pyruvate. Introduction
- Net ATP Gain: 2 ATP molecules per glucose - Energy Production: Critical for cellular functions like
molecule. movement and breathing.
- ATP Generation: Primary molecule for storing and
Glycolysis Steps transferring energy in cells.

Preparatory Phase Aerobic Respiration

1. Hexokinase Reaction: Glucose → Glucose-6- - Definition: Process by which cells generate ATP
phosphate (uses 1 ATP) using oxygen.
2. Phosphoglucoisomerase Glucose-6-phosphate → - Steps Involved:
Fructose-6-phosphate 1. Glycolysis: Breaks down glucose into pyruvate in
3. Phosphofructokinase 1: Fructose-6-phosphate → the cytoplasm.
Fructose-1,6-bisphosphate (uses 1 ATP) 2. Citric Acid Cycle: Pyruvate is further broken
4. Aldolase: Fructose-1,6-bisphosphate → down in the mitochondria.
Glyceraldehyde-3-phosphate (GADP) + 3. Oxidative Phosphorylation: Major ATP
Dihydroxyacetone phosphate (DHAP) production phase; relies on oxygen as the final
5. Triosephosphate Isomerase: Converts DHAP to electron acceptor in the electron transport chain.
another GADP - Requirement: Molecular oxygen (O₂) is essential
for the electron transport chain.
Payoff Phase - ATP Yield: High, around 30-32 ATP per glucose
6. Glyceraldehyde Phosphate Dehydrogenase: molecule.
GADP → 1,3-Bisphosphoglycerate (uses NAD+ and
inorganic phosphate) Anaerobic Respiration and Fermentation
- Anaerobic Respiration: Uses an electron transport
chain but with a final electron acceptor other than
oxygen (e.g., sulfate ions producing hydrogen
sulfide). ---
- Fermentation: Does not involve respiration or
electron transport chains. It allows ATP production in Introduction
the absence of oxygen, mainly through glycolysis.
- Topic: Citric Acid Cycle
Types of Fermentation - Context: Building on glycolysis, which is an
1. Alcohol Fermentation: anaerobic process (does not require oxygen)
- Process: - Key Point: Glycolysis provided early organisms with
- Glycolysis produces pyruvate and 2 ATP. energy, but higher organisms needed more energy,
- Pyruvate undergoes decarboxylation to produce made possible by oxygen-dependent aerobic
acetaldehyde. respiration from photosynthesis.
- Acetaldehyde is reduced by NADH to produce
ethanol, regenerating NAD+ for glycolysis. Mitochondria
- Applications: Used by yeast to produce alcoholic
beverages and by bakers to make bread rise. - Location: Mitochondria (eukaryotic cell organelles)
- Theory: Endosymbiotic theory suggests
2. Lactic Acid Fermentation: mitochondria were once separate organisms
- Process: incorporated into eukaryotes for their respiratory
- Glycolysis produces pyruvate. abilities.
- Pyruvate is reduced by NADH to produce lactate,
regenerating NAD+ for glycolysis. Citric Acid Cycle Overview
- Applications: Used by certain fungi and bacteria
to produce cheese and yogurt. Also used by human - Starting Point: Pyruvate molecules from glycolysis
muscle cells during strenuous exercise when oxygen enter the mitochondrial matrix.
is scarce. - Key Steps:
- Formation of Acetyl CoA:
Summary - Pyruvate undergoes decarboxylation, oxidation
- All forms of energy production begin with by NAD+, and attachment to Coenzyme A, forming
glycolysis, making it the most evolutionarily ancient acetyl CoA.
method of ATP production. - Eight-Step Pathway:
- Pyruvate can be further processed through lactic - Step 1: Citrate synthase enzyme attaches acetyl
acid fermentation, alcohol fermentation, the citric group to oxaloacetate to form citrate.
acid cycle, or anaerobic respiration, depending on - Step 2” Aconitase removes a water molecule and
the presence of oxygen and the organism. adds another to form isocitrate.
- The main difference between these processes is - Step 3: Isocitrate dehydrogenase oxidizes
that oxidative phosphorylation (part of aerobic isocitrate by NAD+ and decarboxylates it to form
respiration) produces the majority of ATP, while alpha-ketoglutarate.
fermentation produces only 2 ATP per glucose - Step 4: Alpha-ketoglutarate loses another CO2,
molecule. is oxidized by NAD+ with ketoglutarate
- The regeneration of NAD+ from NADH is crucial for dehydrogenase, and joins Coenzyme A to form
glycolysis to continue, either through fermentation succinyl-CoA.
reactions or the electron transport chain during - Step 5: Succinyl-CoA synthetase displaces CoA
respiration. with a phosphate group to form succinate,
producing one GTP (which can be used to make one
--- ATP).
- Step 6: Succinate dehydrogenase oxidizes
Reviewer: The Citric Acid Cycle succinate by FAD to form fumarate and FADH2.
- Step 7: Fumarase catalyzes hydration to form
--- malate.
- Step 8: Malate dehydrogenase oxidizes malate
### Citric Acid Cycle Reviewer by NAD+ to form oxaloacetate, restarting the cycle.
Energy Yield
- Electrons from NADH enter the first component of
- For Each Acetyl CoA: Produces 3 NADH, 1 FADH2, Complex I
and 1 ATP - Series of redox reactions shuttle electrons downhill
- For Each Glucose: Since one glucose produces two from one component to another
pyruvates (and thus two acetyl CoAs), double the - Each structure down the chain has a higher affinity
numbers to 6 NADH, 2 FADH2, and 2 ATP. for electrons
- Does not directly generate ATP
Summary - Byproduct: Proton gradient across the inner
mitochondrial membrane
- Citric Acid Cycle Steps with Enzymes/
- Formation of citrate (citrate synthase) Chemiosmosis and ATP Synthesis
- Formation of isocitrate (aconitase)
- Formation of alpha-ketoglutarate (isocitrate - Proton Gradient: Protons accumulate outside the
dehydrogenase) inner mitochondrial membrane
- Formation of succinyl-CoA (ketoglutarate - ATP Synthase: Protein complex that synthesizes
dehydrogenase) ATP
- Formation of succinate (succinyl-CoA synthetase) - Proton concentration is higher in the
- Formation of fumarate (succinate dehydrogenase) intermembrane space than inside the mitochondrial
- Formation of malate (fumarase) matrix
- Formation of oxaloacetate (malate - Protons move with the gradient back into the
dehydrogenase) mitochondrial matrix through ATP synthase
- Next Steps: Products (NADH and FADH2) move to - This process is called chemiosmosis
oxidative phosphorylation, generating the majority - The gradient is also known as the proton-motive
of ATP in aerobic respiration. force
- Protons power ATP synthase to phosphorylate
--- ADP, generating ATP

Oxidative Phosphorylation Reviewer \ ATP Synthase Structure

--- - Resembles a rotor

- Protons bind and cause it to spin
Introduction - Catalyzes the phosphorylation of ADP, similar to a
waterwheel turning
- Topic: Oxidative Phosphorylation
- Context: Continuation from glycolysis and the citric Energy Yield
acid cycle
- Key Point: Generates the most ATP in cellular - From one glucose molecule:
respiration - NADH and FADH2 from glycolysis and the citric
acid cycle generate about 26-28 ATP
Oxidative Phosphorylation Overview
Summary of Cellular Respiration
- Location: Inner membrane of the mitochondrion
- Key Components: - Glycolysis:
- Electron transport chain (ETC): Series of - Ancient metabolic pathway
mitochondrial membrane proteins (Complexes I-IV) - Produces 2 ATP per glucose
- Prosthetic groups: Non-protein components, such - Results in pyruvate, which enters the citric acid
as flavin mononucleotides and cytochromes cycle
- Ubiquinone (Coenzyme Q, CoQ): A mobile, - Citric Acid Cycle:
hydrophobic molecule within the membrane - Each pyruvate generates 2 ATP, 6 NADH, and 2
FADH2
Process of Electron Transport Chain - NADH and FADH2 proceed to the electron
transport chain
- Electron Transport Chain:
- Generates the majority of ATP
- NADH and FADH2 produce around 26-28 ATP

Metabolic Pathways

- Glycolysis: Initial step in cellular respiration

- Citric Acid Cycle: Further breakdown of pyruvate
- Oxidative Phosphorylation: Main ATP production
pathway
- Other food sources (proteins, fats, carbohydrates)
are broken down and fed into these pathways

Mitochondria

- Regarded as the engine of the cell

- Most of the energy needed for cellular activity
comes from mitochondria

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