Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
47 Cards in this Set
- Front
- Back
|
Enzymes |
- catalysts that make reactions occur faster -not destroyed during reactions - function by lowering activation energy - most are globular proteins - undergo hydrolysis (degradation) and denaturation - can be switched on or off whenever needed for regulation
ex. glucose occurs faster with enzymes rather than taking 2 hours to occur alone |
|
|
Generic Enzymes |
It works for various substrates while highly specific ones work only for one specific substrate - some are moderately specific and can bind to various similar molecules |
|
|
What does -ase mean |
usually identifies a substance as an enzyme
ex. lipase, sucrase |
|
|
What does -in mean? |
usually found in names of 1st enzymes studied which deals with digestion (pepsin)
oxidase- oxidation reaction |
|
|
Coenzymes |
function as shuttles or transfers for agents, usually your b vitamins
ex. B1, B2, etc These are destroyed and you must keep making more every time you use them up |
|
|
Cofactors |
usually metal ions that bind to the enzyme or substrates
ex. Mg, Co, CU, Are not destroyed during the reaction |
|
|
Enzyme Properties |
- functions as catalysts - globular shaped proteins (suspended/ soluble) - Lowers activation energy - can switch on and off when needed - make reactions occur faster rates - cannot be destroyed in the process - can undergo the same functions as proteins (hydrolysis, degradation, denaturation) |
|
|
Isoenzymes |
They form the same chemical reactions but are simply structurally different. - multiple forms of an enzyme
-similar biological effects but occur in different tissues.
- different amino acid compositions (diff because made by diff cells)
ex. different forms of LDH in the liver compared to the heart |
|
|
proenzymes or zymogens |
- inactive precursor of enzymes - in order become active, you must add or remove fragments to make it become active
ex. pepsinogen -> pepsin (would digest in stomach) thus removal of peptide fragment by hydrolysis.
|
|
|
Covalent modification |
where we see a change of structure and activity of the enzyme due to formation or hydrolysis (by adding or simply removing the functional groups) of chemical bonds. - these are usually reversible (2 important processes)
ex. protein phosphorylation (kinases) or dehosphorylation (turning off or removal of phosphate) |
|
|
Synthesis |
inducers, substrates or structurally similar compounds that stimulate/ induce synthesis of enzymes |
|
|
Repression |
excess metabolite turns off synthesis of enzymes and may induce/ stimulate degration (digestion) of enzymes.
where you stop making RNA protein and turns off genes or DNA
Governed by DNA and gene regulation since enzymes are proteins |
|
|
allosteric enzymes |
(quartinary proteins of more than 1 chain) can turn off enzymes. - molecule of 2 or more protein chains and 2 kinds of binding sites (active/ catalytic site; substrate/ allosteric site for regulator) - both sites are different and can be located on 2 different chains or on 2 different site locations on the same chain - binding on the allosteric chains changes the overall 3D shape of the enzyme as well as the active site |
|
|
Regulators or Effectors |
substances that bind to allosteric sites |
|
|
2 different effects for allosteric enzymes |
1. positive effectors: substrate is accepted more readily. increases enzyme activity and reaction time 2. negative effectors: substrate is accepted less readily. similar to non competitive inhibition with a decrease in enzyme reaction time |
|
|
List 4 enzyme reactions |
oxidase hydrolase dehydrogenase decarboylase
|
|
|
oxidase |
involves oxidation reaction |
|
|
hydrolase |
involves hydrolysis |
|
|
dehydrogenase |
removal of hydrogen |
|
|
decarboylase |
removal of CO2 |
|
|
What is an example of a zymogen or proenzyme? |
pepsinogen -> pepsin (digest in stomch) removal of peptide fragment by hydrolysis |
|
|
What are the factors that affect enzyme activity? |
- temperature - pH - reactant concentration |
|
|
How does temperature affect enzyme activity? |
-increases temp - increases kinetic energy - increases collision frequency
- as temp increases from low to high, the # of molecules whose KE is > or equal to the energy of activation increases
- temperatures above 100 degrees F denatures the protein
- high temps decrease enzyme activity = less collision, less binding
|
|
|
How does pH affect enzyme activity? |
(7 - 7.5 for most) (.2-.3 for some) - altercations in pH affects the structure of the protein (denaturation) - acidic/ basic conditions affects the activity of enzyme activity |
|
|
How does reactant concentration affect enzyme activity? |
- when [c's] are high, there are many molecules with enough energy to collide and react - you can double one reactant and the rate will increase by 2. double that and rate will increase by 4x - reaction rate is proportional to the concentration of reacting molecule |
|
|
What are the models of enzyme actions? |
1. active site 2. substrate
|
|
|
Active site |
small portion of the enzyme that is invovlved in catalysis |
|
|
substrate |
attached reversibly to the active site to form and enzyme substrate complex
- where it bind for a few milli sec, converted into something else, then releases product from active site. |
|
|
(Catalytic site models) Lock and key model (1st theory) |
the active site is fixed and rigid and there is only specific substrates that can bind to it |
|
|
induced fit model |
the active site can change its shape to whatever it wants. whether it wants the substrate to bind or to change to a shape to avoid it from binding.
-metal ions (cofactors) sometimes are involved in binding substrate molecules - this theory believes that it is not fixed or rigid |
|
|
What is the Michaelis- Menton equation? Identify what each part means. |
vi = vmax [S] / km = [s]
vi = initial velocity vmax = max velocity [s] = concentration of substrate km = michaelis constant = 1/2 vmax |
|
|
Identify the parts of the Michaelis- Menton equation from a Lineweaver- Burk plot. |
Linear way of looking at the Michaelis Menton equation using y = ax + b.
known as a double recipricol plot (take equations and flip them)
so, (v/vi) = km/ vmax * 1/ [s] + 1/vmax
allows us to compare enzyme activity to inhibitors.
|
|
|
inhibit |
slow down |
|
|
competitive inhibition |
- molecule that closely resembles the substrate (chemically) and binds to the active site - similar in shape and charge distribution - temporarily prevents substrates from binding to the active site - increases [s]to overcome inhibition - reversible
vmax does not change; km increases |
|
|
non- competitive inhibition |
- non- similar molecule binds to any site on the enzyme instead of the active site. - binding causes a 3D change in shape of the enzyme along with the change of the active site - you must remove the inhibitor in order to overcome it.
decreases [I] (inhibitor) in order to return to the normal shape to accept substrates
- vmax decreases; km doesn't change |
|
|
irreversible inhibition |
- molecule that forms a strong covalent bond to a part of the active site or allosteric site - permanently prevents substrates from binding to the active site (shuts off enzyme for good) - structurally different molecule - increasing [s] will NOT overcome inhibitor - overcome by removing the inhibitor or make new ones |
|
|
Drugs |
natural target for pharmacological development agents |
|
|
statins |
lower blood cholesterol levels by inhibiting HMG- coA
|
|
|
emtricitabine and tenofoyir |
blocks virus replication by inhibiting viral reverse transcriptase |
|
|
captopril |
lowers blood pressure by inhibiting angiotensin converting enzyme ACE |
|
|
Enzyme regulation |
metabolism (homeostasis) |
|
|
Metabolism (homeostasis) |
ability of enzyme catalyzed reaction rate to respond to changes in the cells internal and external environment |
|
|
metal ions |
may facilitate and aid in substrate binding while some (heavy metals and prevent it) |
|
|
feedback inhibition |
process where activation of inhibition of the enzyme of an earlier reaction in a reaction sequence is controlled by a product of reaction sequence. |
|
|
what are common products of reaction and hormones from outside the cell? |
effectors |
|
|
feedback regulation |
- not a mechanism of enzyme regulation like feedback regulation - product decreases its own synthesis but doesn't do it through enzyme inhibition but through different mechanism |
|
|
enzymes in diagnosis |
- present in blood in small amounts - following diseases, lysis and destruction to cellular fragments occur - fragments dispersed into interstitial fluid and picked up by lymphatic system
speed of enzyme increase the smaller they are |
