This document discusses energy production and metabolism. It begins by defining energy and its various forms. It then discusses metabolism, defining it as chemical reactions that build and break down molecules. There are two types: catabolism breaks down molecules and releases energy, while anabolism uses energy to build molecules. A key molecule in this process is ATP, which captures and transports chemical energy throughout the cell to power other reactions. ATP is produced through cellular respiration, a multi-step process involving digestion, acetyl group formation, the citric acid cycle, and oxidative phosphorylation in the electron transport chain, where ATP is synthesized using the proton gradient established.
2. LEARNING OUTCOMES
At the end of this topic, students will be able to:
Describe the definition and function of energy
Define metabolism, catabolism and anabolism
Describe the definition and function of ATP
Explain energy production by ATP
State the classification of metabolic intermediate compounds
Describe the mechanism of energy production
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3. What is Energy?
Energy is defined as the capacity for doing work:
Chemical Work
Making and breaking of chemical bonds
Transport work
Moving ions, molecules, and larger particles
Can create concentration gradients
Mechanical work
Used for movement (muscle contraction)
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4. Energy transfer in the environment
The Sun is the ultimate source of energy
Photosynthesis organism trap light energy
and use it to drive the energy-requiring
reactions that convert CO2 and H2O to
C6H12O6 and O2 through reduction
reaction.
No photosynthetic organism such as
animals consume these carbohydrates and
use them as energy sources involving
oxidation reaction.
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5. Definition of Metabolism
Metabolism is a series of chemical reactions in a cell that build and breakdown
molecules for cellular processes.
For example, one metabolic pathway for carbohydrates breaks large molecules
down into glucose. Another metabolic pathway might build glucose into large
carbohydrate molecules for storage.
Two types of metabolism:
i. Catabolism: reactions where complex molecules (carbohydrate, lipids, and
proteins) are broken down to simpler one and release energy
ii. Anabolism: reactions that consume energy to build complex molecules
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6. Catabolism
Broken down of complex molecules to a simpler
molecules.
This reactions causes releasing of energy stored in the
bonds of those molecules (exergonic reaction)
Some catabolic pathways can capture that energy to
produce ATP, a molecule used to power all cellular
processes.
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7. Anabolism
Synthesize of a complex molecule from simpler molecules
the reactions require a input of energy (endergonic
reactions)
These processes are critical to the life of the cell, take place
constantly, and demand energy provided by ATP and other
high-energy molecules like NADH and FADH2
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8. What is ATP?
Adenosine triphosphate (ATP) consist of molecule of adenosine (adenine + ribose) to which 3 phosphate
group are attached
ATP is called high energy phosphate compound
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9. Functions of ATP
ATP captures chemical energy of food molecules and releases it to fuel other
cellular processes.
When energy is needed by cell, it is converted from storage molecule into ATP.
ATP serves as shuttle, delivering the energy to where energy consuming activities
taking place
Energy carrier - energy is stores in between phosphate bonds
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10. How ATP produces Energy
Energy production lies with the phosphate group
Breaking the phosphate bond is an exergonic reaction.
When ATP loses one or two phosphate groups via hydrolysis, energy
is released
ATP + H2O → ADP + Pi + Energy (Δ G = -30.5 kJ.mol-1)
ATP + H2O → AMP + PPi + Energy (Δ G = -45.6 kJ.mol-1)
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11. How ATP produces Energy
If one phosphate is removed, ADP is produced;
If two phosphate is removed, adenosine
monophosphate (AMP) results.
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12. Synthesis of ATP
ATP is primarily synthesised in the cellular respiration process.
It is synthesised by the oxidation of respiratory substrates such as
carbohydrate, lipids, protein, etc results in energy production, which is stored in
the form of high energy bonds in ATP.
Glucose is the main energy source in living organism. The catabolism of glucose
takes place in three steps; glycolysis, kerbs cycle(also known as TCA cycle) and
oxidative phosphorylation
Most ATP formation takes place in the electron transport chain by oxidative
phosphorylation. ATP synthase is the enzyme that catalyses the synthesis of ATP
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14. Classification of Metabolic Intermediate
Compounds
Intermediates for storage of energy and transfer of phosphate group
Intermediates for the transfer of electrons in metabolic redox reactions
Intermediates for the transfer of acetyl group
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15. Biochemical Energy Production
(Catabolism)
Energy needed to run human body is obtained from food
Multi-step process in that involves several different catabolic pathways aid in this
process
There are four stages:
1. Stage 1: Digestion
2. Stage 2: Acetyl group formation
3. Stage 3: Citric Acid Cycle (TCA Cycle/Krebs cycle)
4. Stage 4: electron transport chain and oxidative phosphorylation
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16. Stage 1: Digestion
Digestion is the breakdown of food
molecules by hydrolysis reactions into
individual monomer units in the mouth,
stomach, and small intestine.
Carbohydrates, fats, and proteins are
broken down into their individual
monomer units
The digestion products are absorbed into
the blood and transported to body’s cells.
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17. Stage 2: Acetyl group formation
The small molecules from stage 1 are further
oxidized
End product of these oxidations is acetyl CoA
Glycolysis occurs in cytosol, there is a net gain of :
2 molecules of ATP
2 molecules of NADH per glucose molecule.
Pyruvate formed in glycolysis enters mitochondrial
matrix to form
2 molecules of Acetyl CoA
5 NADH
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18. Stage 2: Acetyl Group Formation
Coenzyme A (HS-CoA)
When the thioester bond broken, acetyl group will bind with the S-CoA to form
acetyl-S-CoA (Acetyl CoA)
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acetyl group
19. Stage 3: Citric Acid Cycle
TCA cycle is based in mitochondria
Main function is to produce reduced enzyme
(NADH and FADH2)
These molecules enter the electron transport
chain and ultimately produce ATP.
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20. Stage 3: Citric
Acid Cycle
Involve 8 steps
Begin with Acetyl CoA reacts with
oxaloacetate to form citrate.
Catalysed by citrate synthase.
2 Acetyl CoA produce:
2 ATP
6 NADH
2 FADH2
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21. Stage 4: Electron Transport Chain and
Oxidative Phosphorylation
The culmination of aerobic cell respiration is oxidative phosphorylation along the
electron transport chain.
The electron transport chain is a series of proteins that receive the high energy
electron from NADH and FADH2 molecules and move those electrons along the
inner mitochondrial membrane and onto the final electron acceptor, oxygen. In
the process, a proton gradient is establishes that is then used to create ATP
molecules via the activity of a special enzyme called ATP synthase.
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22. Stage 4: Electron Transport Chain and Oxidative
Phosphorylation
1. High energy electron is released from NADH and
FADH2 molecules.
2. The electron then transferred onto the electron
transport chain.
3. The movement of electron stimulates the movement
of H+ ions (proton) out of the matrix and into
intermembrane space of the mitochondria. This
establishes an electric potential difference between
the two sides.
4. The electron are ultimately captured by oxygen to
form water
5. The unequal distribution of H+ causes the
spontaneous movement of the H+ down their
electrochemical gradient and back into the matrix.
This flow of ions help generate the ATP catalysed by
ATP synthase.
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24. ATP Yield
GLYCOLYSIS ATP 2
NADH 2
ACETYL GROUP
FORMATION
NADH 5
TCA CYCLE ATP 2
NADH 6
FADH2 2
OXIDATION
PHOSPHORYLATION
6NADH X 2.5 15
2 FADH2 X 1.5 3
TOTAL ATP YIELD 37
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