Energy and Metabolism
Terms
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- What produces energy from the sun?
- Plants and other phytosynthetic organisms
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Define:
Metabolism - Sum of all chemical reactions that occur in an organism
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Define:
Metabolic Pathway - A series of steps that converts a molecule into a product
- What catalyzes each step in a metabolic reaction?
- A specific enzyme catalyzes each specific step
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Define:
Anabolic Pathways -
metabolic pathways that build complex molecules from simpler ones.
consumes energy - What is an example of a catabolic pathway?
- Cellular Respiration. Releases energy by breaking down glucose and other organic fuels
- What is an example of an anabolic pathway?
- Photosynthesis. Consumes energy (light) to produce glucose and oxygen
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Define:
Energy - The capacity to do work
- What is kinetic energy?
- The energy of motion
- What is potential energy?
- stored energy
- What are the three types of energy?
- Chemical Energy, Radiation Energy, and Thermal Energy
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Define:
Chemical Energy - The energy stored in molecular bonds
- What kind of energy is released by catabolic pathways?
- Chemical Energy
- What kind of energy is used during photosynthesis?
- Radiation Energy
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Define:
Radiation Energy - light
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Thermal Energy - Kinetic energy of atomic motion. Heat.
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Define:
The First Law of Thermodynamics - Any form of energy can be converted to any other form of energy BUT is never created or destroyed.
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The Second Law of Thermodynamics - All transfers and transformations increase the entropy of the universe.
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Define:
Entropy - a quantity that measures disorder or randomness
- What is lost in all energy transformations?
- useful energy in the form of heat
- As heat increases atomic motion _____ increases
- entropy
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Define:
Free Energy - The energy in a system that is available to do work. Useful energy.
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Define:
Gibb's Free Energy Equation -
ΔG = ΔH - TΔS
Δfree energy = Δtotal energy - (Kelvin temp X Δsystem's entropy) - What happens to a system as the free energy increases?
- The system becomes less stable -> can do more work
- What happens to a system as the free energy decreases?
- The system becomes more stable -> can do less work
- How can all energy transformations be described?
- by the change in free energy
- What must happen in order for a process to occur spontaneously?
- There must be a decrease in free energy. (-ΔG)
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List:
Characteristics of an Exergonic Reaction -
-reactions that release energy
- -ΔG
- spontaneous -
List:
Characteristics of Endergonic Reactions -
- reactions that absorb energy
- +ΔG
- not spontaneous - What are the equations for cellular respiration and photosynthesis?
- C₆Hâ‚â‚‚O₆ + Oâ‚‚ ⇔ COâ‚‚ + Hâ‚‚O
- What can the released free energy do in a spontaneous metabolic reaction?
- The released free energy can be harnessed to do work.
- How does a cell keep its metabolic pathways from reaching equilibrium?
- By using catabolic pathways in which a series of exergonic reactions release energy. The products of one reaction are the reactants to the next.
- How do cells drive endergonic reactions?
- By using the energy released from exergonic reactions.
- Why does a phosphate molecule break off from the triphosphate group of ATP sponateously?
- Because the negative charges on the phosphate groups repel one another.
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Define:
Energy coupling - the use of exergonic reactions to drive endergonic reactions. The overall ΔG is negative, so together the reaction is sponateous.
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Define:
Catalyst - a substance that speeds up a reaction without being consumed or changed by the reaction
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Define:
Enzyme - A catalytic protein
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Define:
Activation Energy - The initial energy required to place reactant molecules in an unstable state.
- What types of molecules are most likely to undergo energy transformations?
- Unstable molecules
- What often provides activation energy?
- heat. It causes the molecules to be less stable.
- What lowers activation energy?
- enzymes
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Define:
Substrate - reactant molecule that enzymes bind to
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Active Site - Region of enzyme that binds substrate
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Define:
Enzyme-Substrate Complex - combination of enzyme and substrate molecules
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Induced Fit - When substrate binds, enzyme changes shape to hold substrate tightly
- Where does enzyme specificity arise from?
- The shape of the active site.
- How do enzymes lower activation energy?
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1. Position two substrates so that bonds can form
2. Contort substrate, creating an instability of bonds
3. Create a favorable microenvironment
4. Active site amino acids participate in reaction. - What factors effect enzyme specificity?
- pH and Temperature
- How does temperature effect enzyme specificity?
- Low temps decrease molecular motion, making substrate-enzyme collisions less likely. High temps denature the enzyme
- How does pH effect enzyme specificity?
- enzyme denatures at too high or too low of pH.
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Define:
competetive inhibition -
Inhibitor molecule binds to active site, preventing binding of substrate.
Can be overcome by adding more substrate -
Define:
Noncompetitive inhibition -
inhibitor molecule binds to site other than active site, changing the shape of the active site, therefore not allowing binding of substate.
Cannot be overcome by adding more substrate -
Define:
Allosteric Regulation - binding of a molecule at one site of an enzyme affects function at another site.
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Define:
Allosteric activator: - molecule that stabilizes the active form of an enzyme
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Define:
Allosteric Inhibitor - molecule that stabilizes the inactive form of an inhibitor
- What does allosteric regulation control?
- metabolic pathways
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Define:
feedback inhibition - allosteric inhibition of a metabolic pathway by the product of that pathway. The end product binds inhibitorily to an enzyme that acts early in the pathway.
- What are the three stages of cellular respiration?
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1. Glycolysis
2. Citric Acid Cycle
3. Oxidative Phosphorylation - What happens between glycolysis and the citric acid cycle?
- Pyruvate from glycolysis enter mitochondria and is converted to acetyl CoA
- What does glycolysis produce?
- 1 glucose produces 2 pyruvate, 2 ATP and NADH
- What does the glycolysis/citric acid junction produce?
- 2 pyruvate produce 2 acetyl CoA, 2 NADH and 2 CO2
- Where does he citric acid cycle occur and what does it require?
- The krebs cycle occurs in the mitochondrial matrix and requires oxygen
- What is the finction of the krebs cycle?
- oxidation of organic compounds derived from acetyl CoA
- How many steps are in the citric acid cycle?
- 8
- How many turns of the citric acid cycle are there for every glucose?
- 2 turns
- For every acetyl CoA, what does the citric acid cycle produce?
- 3 NADH, 1 FADH2, 1 ATP, 2 CO2
- For every glucose, what does the citric acid cycle produce?
- 6 NADH, 2 FADH2, 1 ATP, 2 CO2
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Define:
Oxidatitive Phosphorylation - The production of ATP using energy derived from the redox reactions of an electron transport chain.
- Where does the tranformation of chemical energy come from?
- The transfer of electrons from one atom to another
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Define:
Oxidation Reduction Reaction - the transfer of electrons from one reactant to another
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Oxidation - Loss of electrons.
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Reduction - addition of electrons
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Reducing Agent - atom that loses electrons
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Oxidizing agent - atom that gains electrons
- Describe the potential energy of polar vs nonpolar molecules
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Nonpolar- high potential energy
polar- low potential energy - What makes oxygen a strong oxidizer?
- its high electronegativity
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Define:
Cellular Respiration - extracting chemical energy from complex organic molecules
- How much energy does cellular respiration produce?
- 686 kcal/mole
- What is the energy from cellular respiration used to produce?
- ATP
- What is the oxidizing agent of cellular respiration?
- Nicotinamide adenine dinucleotide (NAD+)
- During respiration, electrons are transferred from _____ to _____ throught the electron transport chain.
- NADH to oxygen
- How does respiration harvest chemical energy?
- Through transfer of electrons from organmic compounds to oxygen.
- Where does glycolysis occur?
- In the cytosol
- What is the only stage of respiration that does not require oxygen?
- glycolysis
- What is the function if glycolysis?
- Glycolysis breaks down glucose into two pyruvate molecules
- Glycolysis is a catabolic pathway that involves how many steps?
- 10 steps
- For every glucose molecule, how many ATP are invested during glycolysis?
- 2 ATP
- What is the energy payoff of every glucose molecule?
- 4 ATP and 2 NADH