24-01-22 - Introduction to Metabolism Flashcards
Learning outcomes
- Define the terms: Metabolism; Anabolism; Catabolism; Oxidation; Reduction
- Describe the major types of fuel used in the body and broadly how they are utilized in metabolism
- Explain how ATP acts as a universal currency for energy, which allows many energy-requiring processes in cells to proceed
- Explain the thermodynamic term ‘Free Energy’ and how enzyme reactions can be coupled to utilize this free energy
What do all physiological processes required?
How is this generated?
What is metabolism?
What are the 2 divisions of metabolic pathways?
What links together these two processes?
- All physiological processes require energy
- Energy is generated by digestion and absorption of food/fuel
- Metabolism is mechanisms which couple the demand for energy (which is constant) with the fuel supply (which is intermittent)
• 2 divisions of metabolic pathways:
1) Catabolism – degradation of molecules to release energy
2) Anabolism – synthesis of new molecules to store energy
- ATP is required by both these processes, which links them together
- There is constant building up and breaking down, the system is never static
What occurs at the 3 stages of metabolism?
• 3 stages of metabolism
1) Stage 1
• Digestion in the GI tract, where nutrients are absorbed and transported in the blood
• They typically immediately go to the liver via the hepatic portal
1) Stage 2
• In the cell cytoplasm there are:
1) Anabolic reactions
• Nutrients built into storage molecules
• This includes glycogen, proteins, and lipids
2) Catabolic reactions
• Nutrients broken down to pyruvic acid and acetyl CoA so they can be fed into pathways to generate ATP
• This process is known as glycolysis
• All fuel sources have key intermediates (e.g proteins to amino acids, fats to fatty acids) so that they can feed into other pathways
3) Stage 3
• In the mitochondria:
• Catabolism requiring oxygen to c0ompletely breakdown foo and generate more ATP
• The Kreb cycle and oxidative phosphorylation occurs here
• This further oxidises food sources, giving as much ATP as possible
What state do bodies exist in?
What are the 2 nutritional states?
What occurs to energy in these states?
What occurs in response to body demands?
- Bodies exist in a dynamic catabolic-anabolic balance
- Two nutritional sates:
1) Absorptive (fed)
2) Postabsorptive (fasting)
- Energy is stored in the adsorptive state and released in the postabsorptive state
- In response to body demands, energy reserves are built up or broken down, with most reactions being reversible e.g protein to amino acids
How can energy in a fuel source be determined?
Why does he body not use this method?
What process does cellular respiration allow cells to use to harvest energy?
How does this process work?
- Energy in a fuel source can be determined by the direct burning of the energy source in a non-living system
- If cells used this method, they’d lose all the energy to heat
- The process of cellular respiration (stages 2 and 3) allows stepwise oxidation of food e.g glucose
- Each step of this process generates energy, which is captured as chemical energy to store in high energy phosphate bonds of ATP
How much oxygen is consumed by humans at rest?
How much can this increase during exercise?
What type of reactions are many cellular reactions?
What are oxidative reactions?
What reactions are in the final steps of metabolism?
What does this power?
- At rest, humans consume about 350ml of Oxygen a minute, which can increase as much as 5x during exercise
- Many cellular reactions are oxidative reactions e.g glucose undergoing the process of oxidation to generate ATP
- Oxidative reactions are the gain of O2 molecules of loss of Hydrogen (or loss of electrons from molecules)
- Reduction reactions are loss of O2 molecules or gain of hydrogen (or addition of electrons
- Final steps in metabolism are the transfer of electrons along a chain of inner mitochondrial membrane proteins (redox reactions) (electron transport chain)
- This ultimately powers the phosphorylation of ADT to ATP
What do redox reactions involve?
What are coenzymes?
What are 2 important coenzymes in metabolism?
What are they derived from?
What is the role of these coenzymes?
- Redox reactions involve one substance losing electrons and becoming oxidised, while another substance is gaining electrons and become reduced
- Coenzymes are molecules essential to the function of enzymes, but are not part of the enzyme itself
• 2 important enzymes in metabolism:
1) Nicotinamide dinucleotide (NAD)
2) Flaven adenine dinucleotide (FAD)
- These coenzymes are derived from B vitamins
- These coenzymes transfer hydrogen/electrons to oxidise molecules in reversible redox reactions during metabolism (glycolysis, citric acid cycle, oxidative phosphorylation)
What is ATP?
Where is energy stored in ATP?
How is energy released by ATP?
How much energy is released?
What can ATP donate to other molecules when needed?
What can other molecules do for ATP?
What is this process called?
- ATP is the universal currency of free energy in biology
- Energy is stored in the phosphate bonds of ATP (phosphoanyhydride bonds)
- The breaking
- Energy is released when ATP is hydrolysed (catabolised) to ADP and Pi (inorganic phosphate – PO4 3-)
- About -30.5kh/mol of energy is released
- ATP can donate its phosphate group to other molecules when needed, forming ADP or AMP
- Molecules like GTP and Creatine Phosphate can donate their phosphate to ADP to form ATP
- This process is called substrate level phosphorylation, which is substrate level, in comparison with oxidative phosphorylation, which happens in the inner mitochondrial membrane
- These 2 processes are the main way of generated ATP
What is the first law of thermodynamics?
What is potential energy?
What are 4 examples of potential energy?
What is kinetic energy?
What are 4 examples?
What is an example of how potential energy is converted to kinetic energy?
- First law of thermodynamics – the total energy of a system (the universe) is constant – energy cannot be created nor destroyed, only converted from one form to another
- Potential energy is stored energy:
1) Nuclear
2) Chemical
3) Gravitational
4) Mechanical
• Kinetic energy is energy a body possesses while in motion:
1) Sound
2) Heat
3) Light
4) Chemical
• Potential energy stored in the bonds of ATP can be released and converted into chemical energy by the movement of pumps
What is the activation energy in biological systems?
What can this also be known as?
What do catalysts, such as enzymes, do to the activation energy?
What do we have at the end of the reaction?
What does Gibbs free energy give an indication about?
Which reaction is more favourable?
What is the formula for Gibbs free energy?
• In biological systems, the activation energy is the energy needed to transform substrates into the transition state (highest energy state of the reaction, but also the most unstable point)
• This can also be known as the Gibbs free energy of Activation (ΔG + or –)
• Catalysts, like enzymes, decrease the activation energy needed for the reaction to take place
• At the end of the reaction, we have the change in free energy (ΔG), aka Gibbs free energy
• Gibbs free energy gives an indication of whether a reaction generates more energy than it requires to initiate (Exergonic reaction -ΔG) or generates less energy than it requires to be initiated (Endergonic +ΔG)
• Exergonic reactions are more favourable
How can essential but unfavourable endergonic reactions take place?
What is an example of this?
What enzyme is used?
What is the Gibbs free energy of this reaction?
What occurs to spare energy not used?
- Unfavourable endergonic reactions can take place by coupling reactions
- Coupling is the biological way of harnessing he spare energy from one reaction to power another less favourable reaction
- An example of this is the 1st step of glycolysis (endergonic) being coupled with the hydrolysis of ATP to ADP and Pi (exergonic)
- The enzyme hexokinase or glucokinase is used, with magnesium binding to the enzyme as a coenzyme
- The Hydrolysis of ATP releases about -30.5 kj/mol of energy, while the 1st step of glycolysis (phosphorylation of glucose) requires +13.8kj/mol of energy, meaning the Gibbs free energy is -16.7k/mol
- Couple reactions often have spare energy, which is not used, this tends to be lost as heat
