Enzymes Homework
Catalyst
A catalyst is a substance that helps a chemical reaction occur
enzymes: special molecules that catalyze biochemical reactions
Enzymes do this by binding to the reactant molecules, and holding them in such a way as to make the chemical bond-breaking and bond-forming processes take place more readily.
enzymes do not change the reaction's ∆G: they do not change whether a reaction is exergonic (spontaneous) or endergonic.
Almost all enzymes are proteins, comprised of amino acid chains, and they perform the critical task of lowering the activation energies of chemical reactions inside the cell.
They only reduce the activation energy required to reach the transition state
Structure and Function of ATP
provides readily releasable energy in the bond between the second and third phosphate groups.
breakdown of ATP through hydrolysis serves a broad range of functions in the cell, including signaling and DNA/RNA synthesis.
ATP is a nucleotide that consists of three main structures:
a chain of three phosphate groups bound to ribose.
the sugar, ribose
the nitrogenous base, adenine
ATP in coupled reactions
Cells couple the ATP hydrolysis' exergonic reaction allowing them to proceed. One example of energy coupling using ATP involves a transmembrane ion pump that is extremely important for cellular function.
Essentially, the energy released from the ATP hydrolysis couples with the energy required to power the pump and transport Na+ and K+ ions. ATP performs cellular work using this basic form of energy coupling through phosphorylation.
Cells use ATP to perform work by coupling ATP hydrolysis' exergonic reaction with endergonic reactions.
This sodium-potassium pump (Na+/K+ pump) drives sodium out of the cell and potassium into the cell
How do you think a single cell might manage various enzymes with different optimal conditions?
In order to bolster a particular pathway, cells can increase the amount of a necessary (rate-limiting) enzyme or use activators to convert that enzyme into an active conformation.
Conversely, to slow down or halt a pathway, cells can decrease the amount of an enzyme or use inhibitors to make the enzyme inactive.
The management of biochemical reactions with enzymes is an important part of cellular maintenance.
Enzymatic activity allows a cell to respond to changing environmental demands and regulate its metabolic pathways, both of which are essential to cell survival.
Such up- and down-regulation of metabolic pathways is often a response to changes in concentrations of key metabolites in the cell.
How Enzymes Catalyze Reactions
Enzyme substrates are chemical reactants that enzymes bind to.
The exact location to which it binds is called the active site, which is made up of different characteristics including amino acids, side chains, r groups, environment, etc.
In order for the enzyme and substrate to have a secured bind, a small process called "induced fit" occurs. This is when the interaction between the enzyme and substrate cause a mild enzyme structure shift to confirm an ideal binding arrangement.
Many chemical reactions required activation energy to occur. The activation energy determines the rate @ which the reaction will proceed. The higher the activation energy, the slower the reaction occurs.
This can be lowered by enzymatic-substrate complex that contorts substrate molecules to facilitate bond-breaking.
There are several types of inhibitors that aid with the molecular regulation of enzymes
noncompetitive inhibitors attaches to another non-active site but can still block the substrate from binding.
competitive inhibitors compete with substrates to bind with the active site.
allosteric inhibitors bind to enzymes so that substrates bind to the active site less efficiently.
Cofactors and Coenzymes exist to help molecules bind to enzymes. It is temporary through ionic or hydrogen bonds and permanent through covalent bonds.
Cofactors are inorganic ions, ie: iron and magnesium.
Coenzymes are organic molecules comprised of hydrogen + carbon. ie: dietary supplements
Heating a system will cause the reaction to occur faster.