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chapter 8
reading reflection
| Question | Answer |
|---|---|
| how does the second law of thermodynamics help explain the diffusion of a substance across a membrane? | second law involves randomization/entropy. When concentration is equal on both sides the distribution is more random than when they are unequal. Diffusion of a substance with less concentration increases entropy, making it energetically favorable process |
| describe the forms of energy found in an apple as it grows on a tree, then falls, then is digested by someone who eats it? | the apple has potential energy in its postion and the sugars have chemical energy, the apple has kinetic as it falls and when digested the chemical energy is broken down to do work and the rest is lost to thermal energy |
| if you place a teasopoon of sugar in the bottom of a glass of water, it will dissolve completely over time. Left Longer, eventually the water will disappear and the sugar crystals will reappear. Explain these observations in terms of entropy | the sugar crystals become less ordered as they dissolve and become randomly spread and overtime the water evaporates and the volume decreases and this increases order |
| cellular respiration uses glucose and oxygen, which have high levels of free energy, and releases CO2 and water, which have low levels of free energy. Is cellular respiration spontaneous or not what happens to energy from glucose | cellular respiration is a spontaneous and exergonic process. The energy released from glucose is used to do work in the cell or is lost as heat |
| a key process in metabolism is the transport of hydrogen ions (H+) across a membrane to create a concentration gradient. Other processes can result in an equal concentration of H+ on each side. Which situation allows the H+ to perform work in this system | When h+ concentration are the same, the system is at equilibrium and can do no work. Hyrdogen ions can perform work if concentration differs on each side, energy input is required for a gradient |
| some night time partygoers wear glow in the dark necklaces. The necklaces start glowing once they are activated and is this exergonic or endergonic? | the reaction is exergonic because it releases energy in the form of light |
| How does Atp typically transfer energy from exergonic to endergonic reaction in cell | Atp usually transfers energy to endergonic processes by phosphorylating other molecules |
| which of the following combinations has more free energy, glutamic acid+ammonia+atp, or glutamine+adp+pi | A set of coupled reactions can transform the first combination into the second. Since this is an exergonic process, Delta g is negative and the first combination must have more free energy |
| many spontaneous reactions occur very slowly. Why don't they occur instantly? | A spontaneous reaction is a reaction that is exergonic. However, if it has a high activation energy that is rarely attained, the rate of the reaction may be low |
| why do enzymes act only on very specific substrates? | only the specific substrates fit properly into the active site of an enzyme, the part of the enzyme that carries out catalysis |
| Malonate is an inhibitor of the enzyme succinate dehydrogenase. How would you determine whether malonate is a competitive or noncompetitive inhibitor? | in the presence of malonate, increase the concentration of the normal substrate (succinate) and see whether the rate of reaction increases. If it does, malonate is a competitive inhibitor |
| in nature, what conditions could lead to natural selection favoring bacteria with enzymes that could break down the fucose containing disaccharide discussed? | if lactose wasn't present in the environment as a source of food and the fucose containing disaccharide was available, bacteria that could digest the latter would be better able to grow and multiply than those that could not |
| How do an activator and an inhibitor have different effects on an allosterically regulated enzyme | The activator binds in such a way that it stabilizes the active form of an enzyme, whereas the inhibitor stabilizes the inactive form. |
| imagine you are a pharmacological researcher who wants to design a drug that inhibits a particular enzyme. Upon reading the scientific literature, you find that the enzymes active site is similar to that of several other enzymes. What might work? | inhibitor binds active site of the enzyme wanted to inhibit could bind to and block the enzymes with similar structures, causing side effects. For this reason, better off choosing to screen chemical compounds that bind allosterically to the enzyme |
| explain how the highly ordered structure of a cell does not conflict with the second law of thermodynamics | The process of ordering a cell's structure accompanied with increase in entropy or disorder of the universe. Entropy decrease often offset by heat |
| explain the meaning of each component in the equation for the change in free energy of a spontaneous chemical reaction. Why is this important with metabolism? | spontaneous reaction has a negative delta G and is exergonic. For a chemical reaction to proceed with a net release of free energy, total energy of a system must decrease, entropy must increase, spontaneous reactions supply energy for work |
| what roles do allosteric regulation and feedback inhibition play in the metabolism of a cell? | a cell tightly regulates its metabolic pathways response fluctuating needs for energy and materials. The binding of activators or inhibitors to regulatory sites on allosteric enzyme stabilizes either the active or inactive form of the subunites |
| catabolism is to anabolism as __ is to __ | exergonic endergonic |
| most cells cannot harness heat to perform work because | temperature is usually uniform throughout a cell |
| Name a metabolic process that can occur without a net influx of energy from some other process | C6H12O6+6O2= 6CO2+6H20 |
| if an enzyme in solution is saturated with substrate, the most effective way to obtain a faster yield of product is to | add more of the enzyme |
| some bacteria are metabolically active in hot springs because | their enzymes have high optimal temperatures |
| if an enzyme is added to a solution where its substrate and product are in equilibrium, what will occur? | nothing, the reaction will stay at equilibrium |
| describe the ATP cycle: How is Atp used and regenerated in a cell | Free energy released from the hydrolysis of atp may drive endergonic reactions through the transfer of a phosphate group to a reactant molecule, forming a more reactive phosphorylated intermediate. Atp hydrolysis also powers the mechanical and transport |
| cont | work of a cell, often by powering shape changes in the relevant motor proteins. Cellular respiration, the catabolic breakdown of glucose, provides the energy for endergonic regeneration atp from adp and pi. |
| how do both activation energy and barriers and enzymes help maintain the structural and metabolic order of life? | activation energy barriers prevent the complex molecules of the cell which are rich in free energy from spontaneously breaking down to less ordered, more stable molecules, enzymes permit a regulated metabolism by binding to substrates and forming enzyme |
| cont | substrate complexes that selectively lower the Ea for the chemical reactions in a cell |
Created by:
kward66666