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Totality of an organism's chemical reaction; emergent property of life that arises from interactions between molecules within the orderly environment of the cell
metabolism
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There are two types of reactions in metabolic pathways: __ + ___
anabolic and catabolic
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Which reactions release energy?
catabolic
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Which reactions consume energy?
anabolic
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Which reactions build up larger molecules?
anabolic
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Which reactions break down molecules?
catabolic
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Which reactions are considered uphill?
anabolic
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Which type of reaction is photosynthesis?
anabolic
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What type of reaction is cellular respiration?
catabolic
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Which reactions require enzymes to catalyze reactions?
anabolic
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Contrast kinetic energy and potential energy?
- Kinetic energy- associated with motion
- potential energy- energy that's stored and can later be used to do cell work
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Which type of energy does water behind a dam have?
potential energy
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What type of energy does a mole of glucose have?
chemical energy
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__ is the portion of a system's energy that can perform work when temperature and pressure are uniform throughout the system, as in a living cell.
free energy
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What is the symbol for free energy?
triangle G
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For an exergonic reaction, is *triangle* G negative or positive?
negative
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Is cellular respiration an endergonic or an exergonic reaction? Why
- exergonic
- it is breaking down molecules
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What is *triangle* G for cellular respiration?
-686 kcal/mol (-2870 kJ/mol)
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Is photosynthesis endergonic or exergonic? Why?
- endergonic
- it requires solar energy to start the process
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What is the energy source that drives photosynthesis?
from the environment by capturing light and converting its energy to chemical energy
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If energy is released, *triangle* G must be what?
exergonic
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List the three main kinds of work that a cell does. Give an example of each.
- chemical- synthesis of polymers from monomers
- transport- active transport (pumping of substances across membranes against the direction of spontaneuous movement)
- mechanical- beating of cilia, contraction of muscle cells, movement of chromosomes during cell division (reproduction)
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In ATP molecules, what bonds are likely to break?
By what process?
- bonds between phosphate groups
- hydrolysis
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List all the molecules that make up ATP
contains ribose with nitrogenous base adenine and a chain of three phosphate groups bonded to it
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What does ATP stand for?
adenine triphosphate
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When the terminal phosphate bond is broken, a molecule of inorganic phosphate Pi is formed, and energy is ________.
released
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For this reaction ATP ----> ADP +Pi, *triangle* G is ____.
Is this reaction endergonic or exergonic?
- -7.3 kcal/mol (-30.5 kJ/ mole)
- exergonic
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The use of an exergonic process to drive an endergonic one; key feature in the way cells manage their energy resources
energy coupling
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In many cellular reactions, a phosphate group is transferred from ATP to some other molecule in order to make the second less stable. The second molecule is said to be __________.
phosphorylated
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If you could not regenerate ATP by phosphorylating ADP, how much ATP would you meed to comsume each day?
You'd use up nearly your body weight in ATP each day.
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A chemical agent that speeds up a reaction without being consumed by the reaction
catalyst
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amount of energy needed to push the reactants over an energy barrier, or hill, so that the downhill part of the reaction can begin; energy required to contort the reactant molecules so the bonds can break
activation energy (EA)
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What effect does an enzyme have on EA?
lowers EA barrier, enabling the reactant molecules to absorb enough energy to reach the transition state even at moderate temperatures.
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How is *triangle* G affected by the enzyme?
it is unaffected; it cannot change an endergonic reaction to an exergonic one; they only hasten reactions that woul doccur eventually anyway
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macromolecule that acts as a catalyst
enzyme
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reactant an enzyme acts on
substrate
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specific portion of an enzyme that binds the substrate by means of multiple weak interactions and that forms the pocket in which catalysis occurs
active site
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material resulting from a chemical reaction
products
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the change in shape of the active site of an enzyme so that it binds more snugly to the substrate
induced fit
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Describe four mechanisms enzymes use to lower activation energy?
- 1. In reactions involving two or more reactants, the active site provides a template on which the substrates can come together in proper orientation for a reaction to occur between them
- 2. As the active site of an enzyme clutches the bound substrates, the enzyme may stretch the substrate molecules toward their transition-state form, stressing the bonding critical chemical bonds that must be broken during the reaction
- 3. The active site may provide a microenvironment that is more conducive to a particular type of reaction than the solution itself would be without the enzyme
- 4. Direct participation of the active site in the chemical reaction
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What are some factors that affect the rate of enzyme action?
- initial concentration of substrate
- pH
- temperature
- cofactors
- enzyme inhibitors
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Explain how initial concentration can affect the rate of enzyme action.
the more substrate molecules that are available the more frequently they access the active sites of the enzyme molecule. However there is a limit.
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Explain how temperature and pH affect the rate of enzyme action.
Enzymes have optimal conditions. Many have 35-40o C and a pH of 6-8. However, there are some exceptions.
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___ affects the rate of enzyme activity because substrates collide with active sites more frequently when molecules move rapidly.
Increase in temperature- optimal temperature
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Why can extremes of pH or very high temperatures affect enzyme activity?
The can denature the enzyme, making it biologically inactive.
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Name a human enzyme that functions well in pH 2. Where is it found?
- pepsin
- human stomach as a digestive enzyme
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nonprotein molecule or ion that is required for the proper functioning of an enzyme; can be permanently bound to the active site or loosely with substrate during catalysis
cofactor
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organic molecules serving as enzymes, such as vitamins
coenzymes
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substances that reduce the activity of an enzyme by entering the active site in place of the substrate whose structure it mimics
competitive inhibitor
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substances that reduce activity of enzymes by binding to a location remote from the active site, changing the enzyme's shape so that the active site no longer functions effectively
noncompetitive inhibitor
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term used to describe any case in which a protein's function at one site is affected by the binding of a regulatory molecule to a separate site
allosteric regulation
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What is the difference between an allosteric activator and an allosteric inhibitor?
- activator- binds to regulatory sitre, stabilizing the shape that has functional active sites
- inhibitor- binding stabilizes the inactive form of an enzyme
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