Lecture 8: Enzymes Flashcards
An ____________ is a protein + cofactor complex designed to catalyze biological reactions
enzyme
____________, _____________ & __________________ within the molecule are 3 basic ways that enzymes work on biological molecules.
Catabolism, Anabolism and rearranging atoms/molecules
Enzymes catalyze biological reactions in two ways: by _____________ and __________ _______
specificity and reaction rate
_____________ work to lower the ACTIVATION ENERGY of chemical reactions.
Catalysts
Without enzymes, most reaction rates would be at or near ______.
zero
Enzymatic reaction rate is between _______ to _______ times as fast if molecules were left alone to react.
100,000 to 1,000,000,000
Enzymes have a discriminatory ability to work on or select the exact molecule or atoms they’re designed for called ___________
specificity
_____________ is the generic name for a molecule that will be worked on by an enzyme; eg starch is the ___________ of amylase enzymes.
Substrate; substrate
Many drugs and herbs “_________” the specificity of enzymes. This is often caused by ______________ _____________ of the active site.
fool; competitive inhibition
There are both __________ & __________ consequences in artificially interfering with the active site & specificity of an enzyme.
positive and negative
Enzymes are made of protein but also incorporate cofactors like ____________, ___________, _____________ & mineral ions to facilitate their functioning
coenzymes, vitamins, porphyrins & mineral ions
The ____________ structure of an enzyme includes at least one _______ ______ where molecules fit & are transformed thru biochem reactions.
tertiary structure; one active site
_______ is a coenzyme and is utilized by many enzymes to facilitate the breaking and fusing of bonds in affected substrates.
ATP
Enzymes are also found as huge _____________ structures, with concatenated tertiary subunit proteins.
quaternary
Other enzymes, because they rearrange molecules in orientation, will _________ a change without using _____
catalyze; ATP
Enzyme activity is affected by many _________ _________
external factors
Name a few external factors that affect enzyme activity…
- Presence or absence of substrates, 2. pH changes or other iconic factors, 3. temp range, 4. availability of nutrients - ATP, cofactors, coenzymes & ions, 5. functionality of enzyme & 6. molecules form drugs, herbs, toxins or organisms
Synthase is known as a _____________
transferase
Amylase molecules from human saliva need ________ & ________ ions to be most effective
calcium & chloride ions
Enzymes are typically classified by the _________ ___________ of the reactions they catalyze
chemical reactions
__________________ remove molecules or atoms from substrates
Oxidoreductases
___________ - transfer functional groups from one molecule to another, such as moving a phosphate group
Transferases
______________ add water to substrates
Hydrolases
_________ work with double bonds
Lyases
_____________ change the isomeric status of a molecule
Isomerases
___________ join or release carbon bonds and requires ATP
Ligases
Enzymes are also named for the _____________ upon which they work
substrate
Examples of enzymes named after substrates they work on are __________ (work on urea molecule) & _______________ (remove water from molecule)
Urease & Dehydrogenase
Two digestive enzymes that retained their old names are __________ & ___________. They are both proteases.
Trypsin & Pepsin
A __________ ____________ goes from substrate enzyme entering active site to substrate complex to product complex to product leaving active site of enzyme
Catabolic pathway
An ________ __________ goes from entering enzyme product active site to product complex to substrate complex product being absorbed into active site of enzyme substrate
Anabolic pathway
A common way that drugs or other molecules stop enzyme function is via _________ __________
competitive inhibition
The term _________ _________ is commonly used to signify that a number of enzymes work on substrates in a specific order
enzyme cascade
____________ is known as an enzyme cascade
Glycolysis
Many enzymes are dependent for proper function on several non-protein molecules called _________
cofactors
When an enzyme doesn’t have its cofactors present, it is called an __________ and is not functional.
apoenzyme
An enzyme with cofactors and fully functioning is a _____________.
holoenzyme
Biochemists classify 2 types of cofactors - __________ ________ & ______________
Prosthetic groups & Coenzymes
Common prosthetic groups are ___________, ____________ groups & ___________ ______. These groups are often the limiting factor in nutrition & energy generation.
vitamins, porphyrin groups & metallic ions
Deficiency in vitamins and minerals slow metabolism and revert back to ___________ status
apoenzyme
Ion in prosthetic groups provided for enzymes come from _________
metals
_____________ is an ion prosthetic used by plants to produce sugars
Magnesium
____________ is an ion prosthetic that helps with the antioxidant system of your body.
Selenium
Whenever there is a Porphyrin with Iron, it’s called a _______
heme
Vitamins have to come in via ______ _________
your diet
Pyruvate dehydrogenase is a ___-________ ________ used to eventually make acetyl coenzyme A from pyruvic acid necessary for Krebbs Cycle.
six-domain enzyme
______________ are called cosubstrates because they act to donate a part of themselves like a substrate to a reaction happening in an active site.
Coenzymes
NAD/NADH and Acetyl coenzyme A are ____________ used repeatedly in production of _____ in mitochondrion
coenzymes; ATP
NAD has one component - _________
Niacin/Vitamin B3
Acetyl Coenzyme A has one component - _________ ______
Pantothenic acid/Vitamin B5
_____ vitamins play a vital role in energy production and can be a limiting factor in nutrition
B vitamins
ATP, Lipoamine, FAD/FADH, Ubiquinone (Coenzyme Q10) & S-adenyl methionine (Sam-e) are all important ___________
coenzymes
ATP splits off a high energy bonded __________ ________ in the active sites of enzymes to propel reaction
phosphate group
What regulates enzyme production?
Gene expression
Genes coding for enzymes are either ________ or _________ by gene expression factors.
Induced or inhibited
If the product produced by the enzyme reaches a plateau concentration, this turns off the enzyme.
Negative feedback loop or allosteric inhibition
Some enzymes are regulated by _________ or __________ molecules that tell the enzyme to operate or not.
inhibitor or activator
Enzymes can be modified by ________ or _______ of functional groups to make the enzyme active or not.
Addition or subtraction
__________ of enzymes will turn on the breakdown of glycogen.
Phosphorylation
(T/F) Placing an enzyme in a changed environment, as in pH change, can activate or deactivate the enzyme.
True - this is one of the regulations of enzyme activity by the cell.
A pre-active enzyme.
Zymogen or proenzyme
What are 3 coenzymes?
1) NAD/NADH+
2) Acetyl Coenzyme A
3) ATP - Adenosine Triphosphate
Enzyme which reduces glutathione disulfide (GSSG) to the sulfhydryl form?
Glutathione reductase
The most important cellular antioxidant.
Reduced glutathione (GSH)
What antioxidant keeps one from getting chronic illness?
Reduced glutathione (GSH)
What molecule is required to reduce GSSG to GSH? And how many of this molecule is required?
NADPH; 2
What is the reduced, phosphorylated version of NAD+?
NADPH
For every _________ and 2 ________ you gain 2 reduced GSH molecules that can again act as antioxidants scavenging reactive oxygen species (ROS) in the cell.
GSSG and NADPH
The process of GSR reducing GSSG forming GSH is especially important in _____ _______ ______.
Red blood cells
Oxygen with an extra electron: O2 -1
Superoxide
(T/F) Reactive forms of oxygen that leak from mitochondrial respiration enzymes and wreak havoc on a cell.
True
What enzyme detoxifies superoxide?
Superoxide dismutase (SOD)
What special type of reaction, where 2 equal but opposite reactions occur on 2 separate molecules?
Dismutation
SOD takes two molecules of ________, strips the extra electron off of one, and places it on the other.
superoxide
The product of SOD creates a normal oxygen molecule and _________ __________, a toxic compound.
hydrogen peroxide
What enzyme is used to detoxify the cell from hydrogen peroxide?
catalase
What enzyme is the fastest enzyme and can convert hydrogen peroxide to water and O2 by the millions per second.
catalase
SOD has recently gained notoriety for its connection with ________ _________ ________.
Amyotrophic Lateral Sclerosis (ALS)
What is the common name for ALS?
Lou Gehrig’s disease
What disease which is a degenerative disorder that leads to selective death of motor neurons in the brain and spinal chord, leading to gradually increasing paralysis over a few years?
Lou Gehrig’s disease
What enzyme where a protein contains an iron porphyrin ring?
hemoprotein enzymes
What enzyme is a common, large and diverse group of hemoprotein enzymes found in many types of life forms?
cytochrome P450 group
Cytochrome P450 is found in mostly what life forms?
Eukaryotes
Cytochrome P450 have 2 common functions:
1) oxygenate substrates
2) pass electrons in aerobic respiration
Cytochrome P450 are unusual enzymes, b/c they can catalyze a plethora of substrates and so are _______.
nonspecific
Where are cytochrome P450 found?
1) mitochondria - part of electron transport chain of oxidative phosphorylation
2) luman of ER in cells - detox functions
What enzyme is one of 57 human cytochromes and is part of the electron transport chain in oxidative phosphorylation?
cytochrome c
_________ are membrane-associated proteins, located either in the inner membrane (cristae) of mitochondria or in the ER of cells.
cytochromes
(T/F) Cytochromes metabolize only a few of endogenous and exogenous compounds.
False - it metabolizes thousands
Cytochrome P450 enzymes are present in all tissues of the body, and play important roles in 3 ways?
1) hormone synthesis and breakdown
2) cholesterol synthesis
3) vitamin D metabolism
What organ does the cytochrome P450 perform as a detox function?
liver
What is the most important cytochrome in cellular detoxification?
cytochrome P450 3A4
Where does the cytochrome P450 3A4 reside?
ER of cells
What organ detoxifies or metabolizes drugs and toxic compounds, all foods, as well as metabolic products?
liver
What is a breakdown product of hemoglobin?
bilirubin
Many drug side effects have to do with the overuse or inhibition of the cytochrome deoxification potential in liver __________.
hepatocytes
What is the term used for reduced dosage of medications from too rapid metabolism?
induction
What is the term used for slow breakdown of drugs, possibly causing an overdose?
inhibition
