Energy, Enzymes, Metabolism
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- What is energy? What is work? Describe energy's role in living cells.
- Energy is the capacity to do work. Work is anything that requires energy. Energy is needed for mostly everything a cell does, including synthesizing biochemicals like protein and nucleic acids, actively transporting molecules across the cell membrane, moving chromosomes during cell division, and for growth, development and reproduction.
- Name the forms of energy.
- There are 5 forms of energy. 1 - Thermal (heat) 2 - Radiant (light) 3 - Mechanical 4 - Electrical (flow of charged particles) 5 - Chemical (arrangement of bonds) These forms of energy fall into two categories: Kinetic: energy released by an object in motion - an object doing work. Potential - energy stored because of an object's location or arrangement (bonds)
- Describe the 1st 2 Laws of Thermodynamics.
- 1st law: energy can be changed from one form to another but cannot be created nor destroyed. 2nd law: as energy is converted into different forms, some usable energy degrades to a less usable form (usually heat) along the way.
- What is the equation that relates free energy, enthalpy and entropy?
- ΔG = ΔH – TΔS T: absolute temperature
- What is free energy? What is enthalpy? What is entropy?
- Free energy: usable energy. energy left to do work. (G) Enthalpy: total energy. (H) Entropy: unusable energy. measure of disorder. (S)
- What is an endergonic reaction?
- In ΔG = ΔH – TΔS... Energy requiring reaction (G2>G1) ΔG is positive. Free energy is consumed during the reaction. i.e. A plant getting needed energy required to undergo photosynthesis.
- What is an exergonic reaction?
- Energy releasing reaction. ΔG is negative. Free energy is released during the reaction. i.e. a molecule releasing energy, which is then stored in ATP for endergonic reactions.
- What does ΔG=G2-G1 represent?
- The difference in free energy in products and reactants. G2 = Product G1 = Reactant When the reactant G1 (free energy available to do work) is greater than the product G2, it is an energy releasing reaction. When the reactant G1 (free energy available to do work) is less than the product G2, it is an energy requiring reaction.
- What is anabolic and catabolic metabolism?
- They are the two categories of metabolism. Anabolic reactions build cellular molecules Catabolic reactions break down cellular molecules. These reactions must be catalyzed by enzymes to occur fast enough to sustain life.
- What is NADPH? How does it meet the cell's needs?
- A molecule specializing in carrying high energy electrons to use in cellular reduction/oxidation reactions. NADPH is used in photosynthesis.
- What is NADH? How does it meet the cell's needs?
- A molecule specializing in carrying high energy electrons to use in cellular reduction/oxidation reactions. NADH is used in cellular respiration.
- What is ATP? How does it meet the cell's needs?
- Adenosine triphosphate. 1 - nucleotide to make RNA 2 - stores chemical energy in covalent bonds that connect phosphate functional groups. 3 - stores energy released by exergonic reactions to be used in future endergonc reactions. 4 - energy is stored when ADP + Pi -> ATP 5 - Energy is released when ATP -> ADP + Pi Pi=phosphate
- What is an enzyme?
- 1 - are highly specific 2 - speed up reactions 3 - are NOT destroyed during reaction ; can be used over and over again 4 - DON'T change endergonic reactions to exergonic reactions 5 - are proteins 6 - bind reactants and convert them into products 7 - information on how to make them are stored as genes in DNA 8 - Do not affect equilibrium
- What is activation energy?
- The amount of free energy needed to push an exergonic reaction over the energy barrier. - ΔG (free energy) released is the same even with a lower activation energy.
- What are substrates?
- Reactants / molecules to be modified in an enzyme-catalyzed reaction.
- What are prosthetic groups?
- Nonprotein molecules with specialized functions. Are permanently attached to enzymes. Required by some enzymes in order to function.
- What are cofactors?
- Nonprotein molecules that bind to enzymes. Are essential for enzyme activity. Required by some enzymes in order to function.
- What are coenzymes?
- Organic molecules like ATP, NADH, that add or remove chemical groups from substrates and assist enzyme function. Required by some enzymes in order to function.
- Why do enzymes speed up reactions?
- Because each enzyme has a unique 3D structure with a binding site that fits the substrates perfectly... enzymes binds substrates so covalent bonds of substrates are stressed; activation energy is lowered; the substrate converts to a product faster.
- Why are enzymes highly specific?
- Because there are thousands of chemical reactions a cell needs for growth, development and reproduction, and a cell needs specific enzymes to cater to those thousands of reactions.
- What is a metabolic pathway? How do allosteric enzymes related to metabolic pathways?
- The chemical reactions of metabolism are organized into metabolic pathways. A metabolic pathway contains chemical reactions in cells arranged in sequential steps. Each step is catalyzed by a specific enzyme. Allosteric enzymes, which either activate or inhibit enzymes when they interact with a cells regulatory molecules and change the shape of active sites, are located early in the metabolic pathway so that whether it inhibits or activates the enzymes regulates the activity of the pathway.
- What are allosteric enzymes?
- Enzymes that interact with a cell's regulatory molecules, changing the shape of the active site, activating or inhibiting the enzyme.
- What are competitive / noncompetitive inhibitors?
- Molecules can inhibit an enzyme by being a ... Competitive inhibitors compete with a substrate for the active site. Noncompetitive inhibitors bind elsewhere on the enzyme, altering the structure of the active site (inhibits/destroys the enzyme's function)