Enzymes and Energy Flashcards
MTC wk 5
What is enthalpy?
heat content
what is change in enthalpy? (delta H)
amount of heat absorbed/released during a reaction
What is entropy?
the measure of chaos: how much thermal energy per unit of temperature is UNavaliable.
What is the calculation for Gibbs Free Energy?
G= enthalpy - Temp x entropy
What is Gibbs Free Energy?
Change in free energy
Describe exergonic reactions.
The energy of the reactants is higher than the products: energy released
Describe endogonic reactions.
The energy of the reactants is lower than the products: energy is added.
How do cells attain energy?
from chemical bonds of organic molecules (oxidation)
What is oxidation?
removal of electrons from an atom
what is reduction?
addition of electrons to an atom
What is a REDOX reaction?
The simultaneous occurrence of oxidisation and reduction
What happens to C-H bonds in an oxidization reaction?
the number of them decrease
what happens to a C-H bond in reduction?
the number of them increase
What are the electron carriers?
NADH, NADPH and FADH
What do the electron carriers do and become?
Carry hydride ions, pass them onto a donor atom and become oxidised (NAD+, NADH+ and FAD+)
what is the reaction for ATP?
ATP + H2O –> ADP + P + free energy
what does ATP do?
Captures and transfers free energy by phosphorylating other molecules
is the conversion of ADP –> ATP exo or endergenic?
Endergonic
what are the three basic steps of a basic enzyme catalysed reaction?
Binding of a substrate- E + S <–> ES
Conversion of bound substrate to bound product ES <–> EP
Release of product EP <–> E + P
What do enzymes lower and what do they NOT change?
Lower energy barrier for reactions
final equilibrium and Gibs Free energy does not change
What does Glucokianse catalyse?
the transfer of P from ATP to C6 of glucose
What are two general ways that drugs can impact enzymatic activity?
Drugs can inhibit or activate it
Alter V or Km
what is the Michaelis-Menten Equations
Describes rate of enzymatic reactions by relating reaction rate (V) to substrate concentration (S)
What is Km?
Affinity constant
What can sulfa drugs do that impact enzymatic activity?
inhibit folic acid synthesis is essential for the metabolism and growth of disease-causing bacteria
What happens to Km and S when competitive inhibition occurs?
Increase S= decreased inhibitor action
Km higher
What do Non-competitive inhibitors do to enzymes?
react with enzymes and alter its structure and activity.
less activity = slow reaction rate
what happens when increase in entropy?
increased disorder
Describe the nature of catabolic reactions.
bonds broken, disorder and negative Gibbs Free Eneregy
Describe the nature of anabolic reactions.
bonds created, more order and positive Gibbs Free Energy
What do you need for a negative Gibbs Free?
negative delta H (exergonic)
what do you need for a positive Gibbs Free?
positive delta H (endergonic)
What occurs in Cellular Respiration (reference glucose bonds)
Energy in glucose bonds is broken down and used to create other compounds.
6C6h12O6 + 6O2 –> 6CO2 + 6H20 + energy
oxidization
What is the difference between NADP+ and NADPH?
NADP+ = oxidised form
NADPH = reduced as H added to the nicotinamide ring
What is the structure of NADPH?
Two phosphates attached to ribose with added H on the nicotinamide ring
What is the chemical reaction for Flavin Adenine Dinucleotide.
Succinate <-Succinate dehydrogenase-> Fumarate
succinate dehydrogenease= FAD–> FADH2
How much can enzymes speed reactions by?
10^6 - 10^17
How do enzymes lower energy barriers for reactions?
bring substarte, coenzyme and metals to enzyme –> change shape
Describe the graph that represents Michaelis-Menten Kinetics
Reaction rate (v) (vertical axis) vs Substrate concentration
What does Km tell us?
Concentration of substrate = velocity that is 1/2 maximal velocity
what does a low Km tell us?
high affinity
Decribe the Km of isomers Hexokinase 1 vs Glucokinase (in liver)
Hexokinase: Km= 0.05 = high affinity for glucose = low glucose concentartion
glucokinase =Km= 5-6 low affinity for glucose = needs a High glucose concentration
what are the units for reaction velocity? (Vmax units)
Vmax units = umol/min/mg protein
How can we analyse the impact of drugs on enzymes?
use lineweaver-burk plots
What does the lineweaver-burk plot determine and what is the formula?
Determines Km and Vmax
1/v = km/Vmax (1/{s} + 1/Vmax
What is the impact of increases [S] in Competitive inhibition?
decrease inhibitors actions
In competetive inhibition, can the same Vmax be reached with more [S]?
Yes
Describe what happens to V, Vmax and [S] in non-competitive inhibition.
V is lower (slower rate of reaction) = less product
increasing [S] NOT stop inhibition
Vmax desceases
What is the impact on Vmax and Km with competitive inhibition?
Same Vmax will be met (despite inc [s])
Km will be higher
What are allosteric enzymes?
enzymes that have an additional binding site for effector molecules. Not an active site.
Why are allosteric enzymes important for regulating the entire metabolic pathway?
They provide inhibitory and stimulatory responses. So will inhibit to slow down process that are not needed and allow for extra binding sites if need to have an increased reaction.
What is the function and common features of a activation-transfere coenzyme?
Functions
-participate directly in catalysis by forming a covalent
bond
-
features
Two groups in the coenzyme:
* Forms a covalent bond (functional group)
* Binds tightly to the enzyme (binding group)
what is an example of an activation-transfer coenzyme?
Thiamine pyrophosphate
Where is the highest energy phosphate on ATP found?
The bonds between phosphate groups, especially the second and third.
Why is there a higher level of glucose but not glycogen in the liver for a patient with a glucokinase mutation?
Glucokinase is not functioning correctly = glucose not broken into glycogen correctly = as glycogen is the store of glucose in the blood, the body does not recognise that it has glucose in it. Thus the BG levels will contain to rise rather than raise and plateau.
What happens to the Km, Substrate concentration and V-Max in a patient with glucokinase mutation?
Km will increase as the body needs a higher substrate concentration to absorb the glucose, and V-max stays the same.
What is the importance of Mg2+ in ATP hydrolysis?
Activator of hydrolysis and increases metabolic state
- How can Positive Delta G reactions go in the forward direction
high reactants and low product levels
What is the name of the enzyme that breaks down alcohol?
aldehyde dehydrogenase.
what are isozymes and an example?
enzymes that catalyze the same type of reaction but are created by different genes and have different molecular shapes.
creatine kinase
What is the difference between NADH and NADPH?
NADPH has a phosphate group which alters its shape.
NADPH= anabolic (energy added)
NADH= catabolic (energy released)
what is the role of thiamine? What can be caused when
enzymatic cofactor in alcohol metabolism. heart and over issues
What is the highest energy phosphate found in ATP?
Alpha and beta phosphate (2nd and 3rd)
What promotes the forward direction of glycolysis? (Glucose-6-phosphate –> Glucose 1-phosphate)
Delta is positive = non-spontaneous = needs energy
[subrate] high enough and products low enough
If the Delta G is negative =
spontaneous
f delta G is positive =
non-spontaneous
Which parto of the enzyme catalyst has the product inhibition?
first
