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Exam 2 Chap 5-6
Terms in this set (17)
· Describe the different cellular activities for which energy is required.
1. Synthetic work - changes in chemical bonds -
- Biosynthesis - cell growth, maintain/replace structures
2. Mechanical work - location/orientation changes of a cell/subcellular structure - Cell movement (ex. obtain food)
3. Concentration work - molecule movement across membrane against concentration gradient - Replace molecules, remove by-products/ toxins
4. Electrical work - ion movement across membrane against electrochemical gradient
- Establish electrical potential across membrane (produce ATP, conduct impulse in nerve & muscle cells
5. Heat - temperature increase for homeotherms (warm-blooded animals) - Regulate body temperature
6. Bioluminescence - light production
Define bioenergetics? What is the flow of energy through different components of the biosphere?
1. Bioenergetics: transformation of energy in living organisms
The flow of energy depends on the nutrients available. Sunlight sustains all life, directly or indirectly
Define phototrophs, chemotrophs.
1. Phototrophs (light-feeders) - capable of photosynthesis - plants, algae, cyanobaacteria, some bacteria
2. Chemotrophs (chemical feeders) - intake chemical compounds - carbohydrates, fats, proteins from phototrophs - Animals, protists, fungi, most bacteria
· Why is energy necessary in different organization levels of organisms (e.g. cellular components, cell, tissue, organs, etc.)? What is entropy?
1. Entropy: thermodynamic quantity representing the unavailability of a system's thermal energy for conversion into mechanical work, can be interpreted as the degree of disorder or randomness in the system.
Energy is necessary for each level of the cell so it can function and carry out their daily functions, survival, and energy is required for metabolism, movement, and breathing.
What is the 1st Law of Thermodynamics, 2nd Law of Thermodynamics? What is the tendency towards equilibrium? What is steady state? What happens to the cell if reactions reached equilibrium?
1. 1st law of thermodynamics: 1st Law of Thermodynamics - law of conservation of energy - In every chemical/physical change, energy may be converted from one form to another but can never be created or destroyed
2. 2nd Law of Thermodynamics - thermodynamic spontaneity - universe tends towards disorder/entropy - reactions have directionality - some reactions possible & occur - Some reactions use energy (endergonic) - Some reactions yield energy (exergonic)
- The tendency towards equilibrium drives all chemical reactions - Living cells maintain a steady state (metastable), far from & don't reach thermodynamic equilibrium (no net reactions, no energy released, no work done, cannot maintain life à a dead cell)
· What are enzymes? What are their functions?
1. Virtually all cellular reactions mediated by enzymes - catalysts
2. Changes state from "can go" to "will go"
3. Increases efficiency of chemical reactions, For reactions to occur: - Molecules must overcome activation energy (EA) barrier - Molecules must interact & reach the transition state • Rate of uncatalyzed cell reactions is very low - (metastable rate)
How do cellular reactions occur?
For reactions to occur: - Molecules must overcome activation energy (EA) barrier - Molecules must interact & reach the transition state
· What is activation energy? Why can heat NOT be used as an energy input?
1. Activation energy: energy required to start a reaction. Enzymes = proteins that need to bind to a molecule or substrate to modify it.
2. Heat cannot be used as an energy input because biological systems are isothermal (constant temperature) - problematic
· Why are enzymes biological catalysts? How do they function?
1. They are catalysts because they catalyze chemical reactions in the bio system. They accelerate the rate of a chemical reaction, it is neither changed or consumed in the reaction.
Have active sites - cluster of aa due to 3-D structure- location where reaction occurs (in groove/pocket)
· What are the properties of enzymes? Are they used up in a reaction? Can they change the products of a reaction? How do enzymes change and function in catalyzing a reaction?
1. Properties: work rapidly, can work in either direction (metabolic reactions are reversible), cannot be destroyed or altered by the reactions they catalyze, sensitive to pH changes and temperatures, specific in their action.
2. The enzymes speed up the reaction but they aren't used up so they can be reused.
3. Enzymes are not used up in the reactions so they do not appear in the reaction products.
4. Enzymes are biological catalysts, catalysts lower the activation energy in reactions.
· How are enzymes characterized?
1. They are characterized by a remarkable efficiency and specificity.
· What is the induced fit model in enzymatic activity? Enzyme kinectics - what and how are the factors involved in increasing the reaction rate?
1. Induced-fit model
• substrate binds, enzyme changes conformation
- positions substrates to react
• also give right environment for substrate activation
• distort/weaken bond so reaction can occur
• may accept/donate protons - increase substrate chemical reactivity (ex. pH dependent)
• may accept/donate electrons - for temporary covalent bonds between enzyme & substrate
• enzyme binds substrates, changes conformation, substrates react, enzyme releases product, enzyme returns to original conformation
· Describe the various methods of enzyme inhibition? Are they permanent?
1. Reversible- binds to enzymes noncovalently & disassociates. Competitive inhibitors bind to active sites. Noncompetitve binds to locations other than activation sites
2. Irreversible- inhibitor binds to enzyme covalently and causes permanent loss of enzymatic activity
· How are enzymes regulated? Why is this important in the cell?
1. Need to control reaction - to match needs of cell
2. Feedback inhibition - product inhibits enzyme(s) in pathway - stop making product (ex. Isoleucine)
· Describe allosteric inhibition and allosteric activation of enzymes.
1. Allosteric inhibition is the process by which a regulatory molecule binds to an enzyme in a spot different from the active site for another molecule.
2. Allosteric enzyme regulation, therefore, is when a molecule binds a site other than the active site and changes the behavior of the enzyme by changing its conformation.
What is covalent modification? Give an example
1. Covalent modification - add/remove chemical groups
What are ribozymes? How do they function? What is their substrate? What is their product?
1. Ribozymes: 1. • pre-rRNA-enzyme that excises & splices itself (autocatalysis)
• RNA also can have tertiary structure
2. Compounds that resemble real substrate, binds to active site but cannot result in functional product
• Important in treatment of infection diseases
• Sulfa drugs
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