AW- energy to life Flashcards
Explain the role of catabolic and anabolic pathways in cellular metabolism.
Catabolism is the break down complex molecules into simpler compounds to release energy. In contrast, anabolism involves building complicated molecules from simpler ones consuming energy in the process. There is no absolute distinction between pathways because many pathways have both catabolic and anabolic functions. Thus the distinction is not that clear. For example, respiration in plants both produces energy and important intermediates that are subsequently used in amino acid synthesis.
Distinguish between kinetic and potential energy.
Kinetic energy is the energy associated with motion. Potential energy is stored in the location of matter and includes chemical energy stored in molecular structure. These two forms of energy can be interconverted.
Explain the first and second laws of thermodynamics
According to the first law of thermodynamics energy can be transferred and transformed, but energy cannot be created or destroyed. According to the second law of thermodynamics spontaneous changes that do not require outside energy increase the entropy, or disorder, of the universe.
Explain why highly ordered living organisms do not violate the second law of thermodynamics.
Organisms decrease their entropy, but “export” entropy to the environment in the form of heat and simple molecules like H2O and CO2. This increases the total entropy of the universe, even though the entropy of the organism decreases.
Write and define each component of the equation for free-energy change.
- The change in free energy, ∆G during a biological process is related directly to the enthalpy change (∆H) and the change in entropy (∆S). ΔG = ΔH – TΔS
- ΔH= change in total enthalpy
- TΔS= change in entropy at constant temp
Distinguish between exergonic and endergonic reactions in terms of free energy change and difference between these and exo and endothermic reaction
During exergonic reactions, free energy is released whereas during endergonic reactions energy is gained. In practice the cell groups exergonic reactions to endergonic reactions.
- that endergonic and exergonic reactions consume and release energy, whereas endothermic and exothermic reactions consume and release heat.
List three main kinds of cellular work.
- Mechanical
- transport
- chemical
Explain in general terms how cells obtain the energy to do cellular work.
Energy is released from food or obtained directly from the sun by photosynthesis. Energy is released from complex substrates by respiration.
Explain how ATP performs cellular work.
The energy of ATP is associated with the unstable terminal P. This unstable bond breaks readily and the P is transferred to other molecules. This transfers energy to those recipient molecules by making them unstable and more able to react.
Describe the function of enzymes in biological systems.
Enzymes speed up metabolic reactions by lowering energy barriers for a reaction. Thus they allow the chemical reaction to proceed by lowering the activation energy of a reaction. Enzymes are catalysts which speed up a reaction without being consumed by the reaction or altering the final balance between reactants and products. Enzymes are catalytic proteins that facilitate a reaction by enabling both bond breaking and bond forming. You can think of an enzyme as a “workbench” on which reactants are brought together and contorted into new shapes and combinations.
Explain why an investment of activation energy is necessary to initiate a spontaneous reaction.
The activation energy, EA, is the initial amount of energy needed to start a chemical reaction (breaks initial bonds). It is often supplied in the form of heat from the surroundings in a system.
Explain how enzyme structure determines enzyme specificity.
The enzyme binds to its substrate, forming an enzyme-substrate complex. This occurs at the active site which has the correct shape and charge to bind to the substrate(s) of the reaction.
Describe the mechanisms by which enzymes lower activation energy.
1) Orienting substrates correctly by induced fit
2) Straining substrate bonds
3) Providing a favourable microenvironment,
4) Covalently bonding to the substrate.
Explain how metabolic pathways are regulated.
1- enzyme inhibition
2- feedback inhibition
3- allosteric regulation.
Define catabolism
breakdown of complex molecules in living organisms to form simpler ones, together with the release of energy
