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68 terms

chapter 6

STUDY
PLAY
energy
ability to promote change or do work
what are the two forms of energy?
kinetic and potential
potential energy
energy that a substance possesses due to its structure or location
chemical energy
the potential energy contained within covalent bonds in molecules
thermodynamics
the study of energy interconversions
first law of thermodynamics
energy can't be created or destroyed
second law of thermodynamics
transfer of energy from one form to another increases entropy
entropy
a measure of the randomness of molecules in a system
what happens to entropy when a physical system becomes more disordered?
entropy increases
enthalpy
the total energy of a system
free energy
the amount of available energy that can be used to do work
exergonic reaction
negative free energy, is spontaneous, and favors the formation of products
endergonic reaction
positive free energy, not spontaneous and favors the formation of the reactants
what is ATP broken down into?
adenosine diphosphate (ADP) and inorganic phosphate (Pi)
chemical equilibrium
the rate of formation of products equals the rate of formation of reactants
phosphorylation
the attachment of a phosphate to a molecule
catalyst
an agent that speeds up the rate of a chemical reaction without being permanently changed or consumed
activation energy
an initial input of energy in a chemical reaction that allows the molecule to get close enough to cause a rearrangement of bonds
transition state
in a chemical reaction, a change in which the original bonds have stretched to their limit. ONce this state is reached, the reaction can proceed to the formation of products
what are two ways to overcome the barrier of the activation energy slowing down the rate of chemical reactions?
reactants can be exposed to large amount of heat and to lower the activation energy by having the enzymes bind to small reactant and having chemical reactions that involve more than one reactant
active site
the location in an enzyme where the chemical reaction takes place
substrates
the reactant molecules that bind to an enzyme at the active site and participate in the chemical reaction
enzyme-substrate complex
...
specificity
refers tot he concept that enzymes recognize specific substrates
induced fit
occurs when a substrate binds to an enzyme and the enzyme undergoes a conformational change that causes the substrate to bind more tightly to the enzyme
Km
Michaelis constant- the substrate concentration at which the velocity is half its maximal value
high Km
higher substrate concentration to achieve a particular reaction velocity
affinity
degree of attraction between enzyme and substrate
high Km has high or low affinity for their substrates?
low affinity and binds weakly
low Km has high or low affinity for their substrates?
high affinity and binds tightly
competitive inhibitors
molecules that bind to the active site of an enzyme and inhibit the ability of the substance of the substrate to bind
noncompetitive inhibitor
a molecule that binds to an enzyme at a location that is outside the active site and inhibits the enzyme's function
allosteric site
a site on an enzyme where a molecule can bind noncovalently and affect the function of the active site
steps of an enzyme catalyzed?
1) ATP and glucose bind to enzyme
2) Enzyme undergoes conformational change that binds the substrates more tightly. The induced fit strains chemical bonds within the substrates chemical bonds within the substrates and/or brings them closer together
3) Substrates are converted to products
4) Products are released. Enzyme is released
prosthetic groups
small molecules that are permanently attached to the surface of an enzyme and aid in catalysis
cofactors
inorganic ions Fe3+ or Zn2+ temporarily bind to the surface of an enzyme and promote a chemical reaction
coenzymes
organic molecules that temporarily bind to an enzyme and participate in the chemical reaction but are left unchanged after the reaction is completed
what surrounding conditions affect enzymes?
temperature, pH, ionic conditions
does high or low temperature denature a protein?
high temperature
denature a protein
unfold
metabolic pathways
a series of chemical reactions in which each step is catalyzed by a specific enzyme
catabolic reactions
a metabolic pathway in which a molecule is broken down into smaller components, usually releasing energy
anabolic reactions
a metabolic pathway that involves the synthesis of larger molecules from smaller precursor molecules. Such reactions usually require an input of energy
energy intermediates
a molecule such as ATP or NADH that stores energy and is used to drive endergonic reactions in the cells
substrate-level phosphorylation
a method of synthesizing ATP that occurs when an enzyme direectly transfers a phosphate from an organic molecule to ADP
chemiosmosis
a process for making ATP in which energy stored in an ion electrochemical gradient is used to make ATP from ADP and Pi
oxidation
the removal of one or more electrons from an atom or molecule
reduction
the addition of electrons to an atom or molecule
does an oxidized or reduced substance have more energy?
reduced
NAD+
(nicotinamide adenine dinucleotide) a dinucleotide that functions as an energy intermediate molecule. It combines with two electrons and H+ to form NADH
biosynthetic reactions
also called an anabolic reaction; a chemical reaction in which small molecules are used to synthesize larger molecules
what are the three ways metabolic pathways are regulated?
gene regulation, biochemical regulation, and cellular regulation
cellular regulation
cells integrate signals from their environments and adjust chemical reactions to adapt to those signals
biochemical regulation
binding of a molecule to an enzyme directly regulates its function
feedback inhibition
the product of a metabolic pathway inhibits an enzyme that acts early in the pathway
gene regulation
cell controls chemical reactions
half-life
the time it takes for 50% of the molecule to be broken down and recycled
what is the functions of degradation?
cell conserve energy when proteins are no longer necessary, mRNA may be faulty and the degradation is beneficial to the cell to prevent the harmful effects of aberrant proteins
exonuclease
enzyme that cleaves off nucleotides, one at a time, from the end of the RNA
exosome
a multiprotein complex that degrades mRNA
proteases
enzymes that cleave the bonds between adjacent amino acids
proteasome
a molecular machine that is the primary pathway for protein degradation in Archaea and eukaryotic cells
ubiquitin
a small protein in eukaryotic cells that directs unwanted proteins in a proteasome by its covalent attachment
what is the advantages of ubiquitin targets?
enzymes that attach to its target recognize improperly folded proteins and allow the cell to identify and degrade nonfunctional proteins, change some cellular conditions may warrant the rapid breakdown of particular proteins
steps of protein degradation in eukaryotic cells
1) string of ubiquitins are attached to a target proteins
2) protein with attached ubiquitins is directed to the proteasome
3) protein I unfolded by enzymes in the cap and injected into the core proteasome. Ubiqutin is released back into the cytosol
4) protein is degraded to small peptides and amino acids
5) small peptides and amino acids are recycled back to the cytosol
process of autophagy
1) membrane tubule beings to enclose an organelle
2) double membrane completely encloses an organelle to form an autophagosome
3) autophagosome fuses with a lysosome. Contents are degraded and recycled back to the cytosol
autophagy
a process whereby cellular material, such as worn-out organelle, becomes enclosed in a double membrane and is degraded
what does the cell use to convert all exogenic reactions to endogenic reactions?
ATP