T2 L1 Role of ATP in living cells Flashcards
What is the definition of metabolism?
An integrated set of enzymatic reactions comprising of both anabolic and catabolic reactions.
Energy is stored as ATP for later use in anabolic reactions.
What is the definition of anabolism?
The synthesis of complex molecules from simpler ones
Requires energy usually derived from ATP
Synthetic reactions
Pathways end in ‘‘genesis’’
What is the definition of catabolism
The breakdown of energy rich molecules to simpler ones
Pathways end in ‘‘lysis’’
Give 4 things that energy is required for
Motion - muscle contraction
Transport - ions/molecules across membranes
Biosynthesis of essential metabolites
Thermoregulation
What does an isothermal system mean?
It maintains a constant temperature
Cells are isothermal systems
Heat flow can’t be used as a source of energy
Heat can only do work when it passes to an area of lower temperature
What is Gibbs free energy?
The energy capable of doing work at a constant temperature & pressure
Delta G = Delta H - T x delta S
What is enthalpy?
The heat content of the reacting system
What is entropy?
The randomness or disorder in a system
What is delta H
The kinds & numbers of chemical bonds that are formed & broken
Positive when energy is absorbed from a reaction - endothermic reaction
What is delta S
The formation of large complex molecules from smaller ones
Positive when randomness increases
What is Gibbs free energy of a reaction?
Maximum amount of energy that can be obtained from a reaction at constant temperature & pressure
What is an exergonic reaction?
Products have less free energy than the reactants
Formation of products is spontaneous
What is an endergonic reaction?
Products have more free energy than reactants so are less stable
Describe the coupling of reactions
Endergonic reactions can be driven in forward direction by coupling to an exergonic reaction through a common intermediate.
1) Glucose + Pi –> glucose-6-phosphate + H2O
2) ATP + H2O –> ADP + Pi
Sum) Glucose + ATP –> glucose-6-phosphate + ADP
Describe Adenosine triphosphate
Provides most of the free energy required
Energy currency of the cell
Formed by phosphate group transfer
Gibbs free energy - energy derived from the oxidation of dietary fuels
Energy conserved as ATP is transducer into useful work
Why is magnesium is present in the cytosol?
ATP is present as a complex with Mg2+
Mg2+ interacts with oxygens of the triphosphate chain & make it susceptible to cleavage in phosphoryl transfer reactions
Mg2+ deficiency will impair almost all metabolism & make the individual tired
What is substrate level phosphorylation?
Formation of ATP by phosphoryl group transfer from a substrate to ADP
Requires soluble enzymes & complex intermediates
Respiration linked phosphorylations involve:
-membrane bound enzymes
-transmembrane gradients of protons
-oxygen
What are enzymes?
Biological catalysts that accelerate the rate of chemical reactions
Create a new pathway for the reaction with a lower activation energy
Doesn’t influence delta G of a reaction
How are enzymes classified?
Transfer of electrons
Transfer of functional groups
Give examples of enzymes with transfer of electrons
Class: Oxioreductases
Important subclasses: dehydrogenase, oxidases, peroxidases, reductases, monoxygenases, deoxygenates
Give examples of enzymes with transfer of functional groups
Class: transferases
Important subclasses: C1 transferases, glyosyltransferases, aminotransferases, phosphotransferases
What are coenzymes?
Non-protein co factors
Most are derived from vitamins
Participate in enzymatic reactions
Have a loose association with their enzyme
Diffuse from one enzyme to the next carrying electrons
Regenerated to maintain cellular concentration
What are prosthetic groups?
Non-protein co factor that is covalently bonded to the enzyme
Not released as part of the reaction
Acts as a temporary store for electrons or intermediates
Give some examples of vitamins
B2- FAD or FMN. Prosthetic group
Niacin - NAD+. Co-substrate
Water soluble vitamins (B1, B2, B3, B6, C, biotin, folic acid & pantothenic acid) are readily absorbed from the diet unlike the fat-soluble vitamins (A,D,E & K)
Describe redox coenzymes/prosthetic groups
Major redox coenzymes/prosthetic groups involved in transduction of energy from dietary foods to ATP:
Electrons are transferred from dietary material to these carriers causing the coenzymes to be reduced
NAD+ is reduced to NADH
FAD is reduced to FADH2
FMN is reduced to FMNH2
Describe nicotinamide adenine dinucleotide
NAD+ & NADP+ accept electrons to form NADH or NADPH
Nicotinamide is te functional part of the molecules
NADH involved in ATP synthesis
NADPH involved in reductive biosynthesis
How does re-oxidation or redox coenzymes occur?
Recycling of NADH & FADH2 occurs via the respiratory chain in the mitochondria
Process is coupled to ATP synthesis - process of oxidative phosphorylation
What are the glycolytic enzymes used in the priming stage?
Priming stage uses 2 ATP & proceeds 2 C3 molecules, which are interconvertible
Hexokinase - phosphorylation reactions
PFK-1 - phosphorylation reactions
Phosphoglucose isomerase - isomerisation reactions
What are the glycolytic enzymes used in the pay off stage?
Pay-off stage generates 4 ATP, 2 NADH & various intermediates
Pyruvate kinase - phosphorylation reactions
Enolase - dehydration reaction
Describe pyruvate
Undergoes oxidation & complex degradation under aerobic conditions
Reduced to lactate in hypoxic conditions to allow NADH to be recycled
Give the steps of glycolysis
Glucose to glucose-6-phosphate to fructose-6-phosphate to fructose-1,6-phosphate
Splits into DHAP or G-3-P
G-3-P goes to 1,3-BPG to 3PG to 2PG to PEP to pyruvate
