Unit II Enzymes

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What are the functions of enyzmes?

catalysts, by lowering activation energy, thus speeding up reactions. enzymes only catlyze energy releasing reactions,

What is the structure of an enzyme?

Largest component is the apoenzyme, made from protein but can also be RNA, which contain active sites that interact with substrates, is specific only work on one reaction.

What is a substrate?

A molecule with complementary shape to an enzymes' active site; it facilitates the action breaking or making bonds. They are also specific reactants, which has the potential to turn into specific products.

What occurs from an enzyme substrate reaction?

the enzyme releases the products.

What is the induced fit model?

enzymes recognize their substrates and adapts to it slightly.

What are coenzymes?

small, non-protein, organic molecules, synthesized by from vitamins, not specific to a given rxn; can only transfer hydrogen ions or electrons. Removes a chemical group from 1 substrate and adds it to another.

What are some examples of coenzymes?

Carrier molecules such as NAD and NADP used during cellular respiration and photosynthesis.

What are cofactors?

inorganic ions, metallic, that adjust the shape of the active sites so they fit to a substrate, help bring active site and substrate close together

What are reactants?

molecules that under chemical changes to yield products.

What are products from enzyme reactions?

The final outcome of the enzyme and substrate reaction, it is released from the enzyme and can often perform same function repeatedly.

What enzyme reaction involves large molecules synthesizing by removing water?

Dehydration synthesis

What enzyme reaction involves large molecules being split apart by adding water?


What enzyme reaction involves a gain of electorns during photosynthesis?


What is the enzyme reaction that changes CO2 to glucose?


What enzyme reaction is involved in the loss of electrons?


What ezyme reaction involves phosphate addition to a molecule?


What is activation energy?

energy required to start a reaction; allows rxns that normally could not occur because of temperature or pressure; allows reactions that would typically occur only in vitro (test tube)

What enzyme reaction involves a donating phosphate to ADP?


What enzyme reaction involves electron from a subtrate that is used to convert ADP to ATP?


Define dehydration synthesis

when larger molecules are formed building blocks by removing water i.e., proteins from amino acids;

Define hydrolysis reaction

when large moleucles are split apart (digested) by adding water

Define reduction reaction

when a molecule gains electrons; during photosynthesis, CO2 is reduced to glucose (hydrogens)

Define oxidation reaction

when a molecule loses electrons (hydrogens)

Define phosphorylation reaction

when a phosphate is added to a molecule

define photosynthetic reaction

when a chlorophyll is used in the converson of ADP to ATP

Define substrate reaction

when a phosphyorlyated substrate donates its phosphate to ADP

Define oxidative reaction

when elelctrons from an oxidized substrate are used to convert ADP to ATP (involves electron transport system)

What are the classification of enzymes

endoenzymes; exoenzymes; constitutive; inducible; repressible


intracellular enzymes; work inside the cell can only be active here


enzymes that are secreted; extracellular; considered virulence factors; must be outside of the cell to become active


enzymes that are always produced; keep a constant number of enzymes regardless of the amount of enzymes


enzymes that are produced only when needed; in response to the presence of a specific substrate


enzymes that do not make any product when the product of the enzyme pathway is present; turned off


when an enzyme is turned on (induced) or off (repress) in response to the changes in concentration of the substrate or product

Naming of enzymes

is often based on name of the enzymes substrate; is often based on type of reaction;

What occurs in dehydration synthesis

Requires ATP, releases H2O from 2 glucose molecule substrates attached to an enzyme; OH bonds are close together bonds the 2 molecules together with peptide bonds

What occurs in hydrolysis reaction

digests; the addition of H2O breaks apart peptide bonds between two amino acids, adds OH to 1 molecule and just an H to the other; ribosomes hook amino acids together before hand; hydrolysis deals with exoenzymes

enzyme naming

typically involves the name of the enzyme's substrate (gelatinase, maltase), often based on type of reaction involved (permiase, oxidase and reductase)

What are the conditions that affect enzyme activity?

anything that denatures a protein; feedback inhibition; competitive inhibition; the concentration of substrates influence efficiency, more substrate the greater the enzyme activity all enzyme molecules engaged

What is feedback inhibition?

occurs when the concentration of enzyme product block further activity; a product reacts with an allosteric site , the shape of the enzyme is altered and production stops.

What is an allosteric site?

is a second binding site on an enzyme, is the regulatory site, provides negative feedback to slow down or stop enzyme activity once a certain concentration is reached.

What is competitive inhibition?

a bacterial inhibitor molecule that mimics a normal enzyme substrate; the mimic occupies the active site "competing with the normal substrate"; shutting down the enzyme because it produces nothing normal substrate can't access the active site

What are some nucleoside mimics?

AZT and Acyclovir

What do AZT and Acyclovir inhibit?

inhibit the activity of reverse transcriptase and DNA polymerase

What do sulfa drugs inhibit?

they compete with PABA for a bacterial enzyme active site; PABA is normally converted to folic acid by microbial enzymes

Removing hydrogen ions from sugar during glycolysis is an example of this enzyme reaction?

Oxidation, loses hydrogen atoms

Hooking two amino acids together to make a dipeptide is an example of this reaction?

Dehydration synthesis, hooking together

Digesting protein into individual amino acids is an example of this reaction?

Hydrolysis; digesting by adding H2O

What two reactions always occur conjuctions, or consecutively?

Oxidation and reduction

What is the most common purpose of oxidation and reduction?

producing atps thru cell respiration in phosphorylation, uses ATP, transfers a Phosphate to glucose, and the end produces ADP

Glycogen is the substrate molecule of an enzyme, this means that?

glycogen has a shape complentary to the enzyme active site and the eznyme converts glycogen to a product.

What is feeback inhibition?

relates to the concentration of products produced by enzymes; enzyme is blocked from further production when the concentration is homeostatic, a product attachesto an allosteric site which alters the emzyme's active site and production stops

What is competitive inhibition?

relates to the presence of inhibitor molecules; which compete for attachment at the active site; (mimics) such as AZT and Acyclovir; the enzyme can not produce a product when this occurs

What is PABA?

para-amino benzoic acid that is converted to the vitamin folic acid by microbial enzymes found in bacteria produced by their enzymes

What is folic acid's role?

is a B vitamin: used as a coenzyme for multiple enzymes that facilitate the synthesis of Purines (adenine, guanine), Pyrimidines (thymine, cytosine) and certain amino acids

What drug competively inhibits the production of folic acid?

sulfa, selective, not antibiotics, made from a dye

How do humans acquire folic acid?

foods; intestinal bacterial flora (which make folic acid for its own use) and some pathogens that cause disease make their own folic acid

In what ways do sulfa drugs affect folic acid?

block folic acid production by both normal intestinal flora and pathogens thru competitive inhibition with PABA for an enzymes active site

Example of inducible enzyme?

when lactose is present it induces the lactose operon - the repressor protein - RNA polymerase attaches to transcribe; when absent no transcription occurs operator site is blocked again

Example of repressible enzyme?

when tryptophan is absent - repressor protein can't block operator site - RNA polymerase transcribes; when tryptophan is present repressor complex fits operator site

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