Intro To Metabolism Flashcards
Metabolism
Is an emergent property of life that arises from orderly interactions between molecules.
Metabolic pathways
A specific molecule is altered in a series of defined steps,resulting in a product.
Each step of a pathway is catalyzed by a specific enzyme: Analogues to the red ,yellow and green stoplights that control the flow of automobile traffic ,mechanisms that regulate enzymes balance metabolic supply and demand.
Catabolic pathways
A major catabolism is cellular respiration ,in which sugar glucose and other organic fuels are broken down in the presence of oxygen to carbon dioxide and water.
*Release energy by breaking down complex molecules.
Anabolic pathways
Consume energy to build complicated molecules from simpler ones; they are sometimes called biosynthetic pathways.
Bioenergetics
The study of how energy flows through living organisms.
Forma of Energy
The capacity to cause change.
Kinetic energy -relative to motion of objects .
Thermal energy- is kinetic energy associated with the random movement of atoms or molecules ; Thermal energy is transfer from one object to another called HEAT.
Potential energy - energy that matter possesses because of its location or structure.
Chemical energy- refer to potential energy available for release in a chemical reaction
The Laws of energy Transformation
Thermodynamics- the study of the energy transformations that occur in a collection of matter.
Isolated system- such as that approximated by liquid in a thermos bottle ,is unable to exchange either energy or matter with its surroundings outside the thermos .
Open system- energy and matter can be transferred between the system and its surroundings .
The first law of thermodynamics and The second law of thermodynamics
The first law of thermodynamics: Energy can be transferred and or transformed, but it cannot be created or destroyed.
The second law of thermodynamics: Every energy transfer or transformation increase the entropy/ disorder of the universe.
Spontaneous process: Means energetically favorably . For a process to occur spontaneously, it must increase the entropy of the universe.
The entropy of a particular system ,such as an organism ,may actually decrease as long as the total entropy of the universe - the system plus its surroundings -increases.
Free energy change (/_\G) ,Stability,and Equilibrium
Is the portion of a systems energy that can perform work when temperature and pressure are uniform throughout the system,as in living cell.
Chemical reaction of life :change in free wnergy (/\G) .
G represents the diff btw the free energy of the finak state and the free energy of the initial state:
/\G = G. - G
final state initial state
We could measure G for any reactions.
•With a - /\ G can occur with no input of energy so the value of /\G tells us whether a particular reaction is a spontaneous one.
•For a reaction to have a NEGATIVE /_\G ,the system must lose free energy during the change from initial state to final state.
• +change will not be spontaneous ; systems never spontaneously move away from equilibrium bc a system at equilibrium can not spontaneously change, it can do no work.
A process is spontaneous and can perform work only when it is moving toward equilibrium.
Free energy: AS A MEASURE OF A SYSTEMS INSTABILITY-its tendency to change to a more stable state.
Chemical Equilibrium: the forward and reverse reactions occur at the same rate,and there is no further net change in the relative concentration of products and reactants.
Exergonic (energy outward) and Endergonic (energy inward) Reactions in Metabolism
Exergonic reaction: proceeds with a net release of free energy.
Cellular respiration:
C6H12O6 + ) O2 -> 6CO2 + 6 H2O
/_\G= -686 kcal/mol(-2870) kk/mol)
Endergonic reaction : absorbs free energy from its surroundings .G increase ,G is positive
ATP powers cellular work by coupling exergonic reactions to Endergonic reactions
Cells does 3 makn kinds of work :
•Chemical work: the pushing of endergonic reactions that would not occur spontaneously ,such as the synthesis of polymers from monomers.
- Transport work: the pumping of substances across membranes against the direction of spontaneous movement.
- Mechanical work: such as the beating of cilia ,the contraction of muscle cells,and the movement of chromosomes during cellular reproduction.
Energy coupling : the use of an exergonic process to to drive an endergonic one . ATP is responsible for mediating most energy coupling in cells ,and in most cases it acts as the immediate source of energy that powers cellular work.
The structure and Hydrolysis of ATP
ATP (adenosine triphosphate) : contains the sugar ribose ,with the nitrogenous base adenine and a chain of three phosphate groups bonded to it .
In addition to jts role in energy coupling ,ATP is also one of the nucleoside triphosphate used to make RNA.
The bonds btw the phosphate groups of ATP can be broken by hydrolysis. When the terminal phosphate bond is broken down by the addition of a water molecule,a molecule of inorganic phosphate (HOPO2- 3 ,which is abbreviated P leaves the ATP . This way , adenosine triphosphate becomes adenosine diphosphate ,or ADP . The reaction is exergonic and releases 7.3 kcal of energy per mole of ATP hydrolyzed:
ATP+ H2O -> ADP + P
/_\G = -7.3kcal/mol (-30.5kJ/mol)
The phosphate bonds of ATP may imply ; the reactants (ATP and water ) themselves have high wneegy relative to the energy of the products
Phosphorylated intermediate
Recipient with the phosphate group covalently bonded to it.
The key to coupling exergonic and Endergonic reactions is the formation of this phosphorylated intermediate, which is more reactive (less stable) than the original unphosphorylated molecule.
The regeneration of ATP
An org at work uses ATP continuously ,but ATP is renewable resource that can be regenerated by the addition of phosphate to ADP .
Free energy required to phosphorylate ADP comes from exergonic breakdown reactions (catabolism) in the cell.
The regeneration of ATP from ADP and P is necessarily endergonic:
ADP + P -> ATP + H2O since not spontaneous ATP formation from ADP and P free energy must be spent to make it occur.
How does the enzyme sucarse to the solution when all the sucrose may be hydrolyzed within seconds ?
An enzyme is a macromolecule that acts as a catalyst ,a chemical agent that speeds up a reaction without being consumed by the reaction .
The activation energy barrier
Free energy of activation / activation energy : abbreviated E
A
Activation energy is often supplied by heat in the form of thermal energy that the reactant molecules absorb from the surroundings
Transition state: When the molecules have absorbed enough energy for the bonds to break ,the reactants are in an unstable condition known as the transition state.
How enzymes speed up reactions
Organisms carry out catalysis a process by which catalyst selectively speeds up a reaction without itself being consumed.
An enzyme catalyzes a reaction by lowering the E
A
barrier ,enabling the reactant molecules to absorb enough energy to reach the transition state even at moderate temperatures.
Enzymes can only hasten reactions that would eventually occur anyway,but this enables the cell to have a dynamic metabolism ,routing chemicals smoothly through metabolic pathways.
Substrate specificity of enzymes
The reactant an enzyme acts on is referred to as the enzymes SUBSTRATE.
The enzyme binds to its substrate (or substrates,when there are 2 or more reactants),forming an enzyme substrate complex.
- 2 line goes back and forth
Enzyme + Substrates Enzyme -substrate Complex Enzyme +Products
Active site : a pocket or groove on the surface of the enzyme where catalysts occurs
Induced fit : like a active site into positions that enhance their ability to catalyze the chemical reaction.
Cofactors
May be bound tightly to the enzymes as permanent residents or they may bind loosely and reversibly along with the substrate.
Cofactors of some enzymes are : inorganic ,such as the metal atoms zinc ,iron, and cooper in ionic form.
Coenzyme: is an organic molecule
Vitamins acts as such or raw materials from which coenzymes are made .
Coenzymes perform a crucial chemical function in catalysis.
Effects of temperature and ph
Optimal condition: favors the most active shape for the enzyme.
Enzyme inhibitors
Competitive inhibitors : reduce the productivity of enzyme by blocking substrates from entering active sites.
Can be overcome by inc the concentration of substrate so that as active sites become available ,more substrate molecules than inhibitor molecules are around to gain entry to the sites.
Noncompetitive inhibitors: do not directly compete with the substrate to bind to the enzyme at the active site.
Selective inhibition: is essential to the control of cellular metabolism
The evolution of enzymes
Mutation - a permanent change in a gene result in a protein with one or more changed amino acids.
Allosteric regulation of enzymes
To describe any case in which a proteins function at one site is affected by the binding of a regulatory molecule to a separate site .May result in either inhibition or stimulation of an enzyme activity.
Cooperatively - mechanism amplifies the response of enzymes to substrates.
Cooperative considered allosteric regulation bc binding of the substrate to one active site affects catalysis in another site.
Feedback inhibition
Metabolic pathway is halted by the inhibitory binding of its end product to an enzyme that acts early in the pathway.
