Energy reaction in cells Flashcards
Define Metabolism
Metabolism is the set of processes which derive energy and raw materials from food stuffs and use them to support repair, growth and activity of the tissues of the body to sustain life
Where do reactions in metabolic pathways occur
– Some metabolic pathways occur in all cells
– Others are restricted to some cell types
– Some may be further restricted to compartments within cells
What are the different points in the metabolic pathway
– Start points
– Intermediates (metabolites)
– End points
– Interconnections
What are the two types of the metabolic pathway, and what do each do?
- Catabolic pathways
– Break down larger molecules into smaller ones
(intermediary metabolites)
– Release large amounts of free energy
– Oxidative – release H atoms – ‘ reducing power’ - that generates ATP - Anabolic pathways
– Synthesise larger important cellular components
from intermediary metabolites
– Use energy released from catabolism (ATP)
– Reductive (i.e. use H released in catabolism)
What is Isothermal
Humans are isothermal - can not use heat energy for work
What are all cellular activities an expression of
All cellular activities are expressions of chemical reactions in which chemical bonds are broken or formed
What is Exergonic and Endergonic difference
- Exergonic - release energy
- Endergonic - require energy
Exergonic Reaction
Exergonic reaction:
* ∆G < 0
* Energy released
Endergonic Reaction
Endergonic reaction:
* ∆G > 0
* Requires energy input
In a metabolic pathway is the ∆G negative or positive
the ∆G must be negative overall
How is energy released from chemical bond
Chemical bond energy of fuel molecules is released by oxidation reactions
What is Oxidation
Oxidation
- removal of electrons (e-) or
- removal of H-atoms (H+ + e-)
What is redox
All oxidation reactions accompanied by a reduction
reaction, known as REDOX REACTIONS
What happens to the electrons and protons when fuel molecule is oxidised
When fuel molecules are oxidised, electrons and protons are transferred to carrier molecules
What are the MAJOR carrier molecules
Major carrier molecules / Oxidised form. / Reduced form
Nicotinamide adenine dinucleotide. / NAD+ / NADH + H+/
Nicotinamide adenine dinucleotide phosphate / NADP+ / NADPH + H+ /
Flavin adenine dinucleotide. / FAD. / FADH2. /
What is the conc of ‘oxidised and reduced’ carriers
Total concentration of ‘oxidised and reduced’ carriers is constant - cycle between oxidative and reductive processes.
What is the ∆G for
ATP + H2O –> ADP + Pi
ADP + H2O –> AMP + Pi
∆Go’ = -31 kJ.mole-1
∆Go’ = -31 kJ.mole-1
(energy stored within the phosphate bond)
What is the ∆G for
ADP + Pi –> ATP + H2O
∆Go’ = +31 kJ.mole-1
what is Energy released in exergonic reactions used to drive
ADP + Pi ——–> ATP
How is energy flow controlled
ATP is stable in the absence of specific catalysts
Enables flow of energy to be controlled
Facts about ATP turnover
- At any moment in time, the human body contains ~250 g ATP
- ATP energy currency is constantly turning over
- Turnover body weight in ATP each day
What is the high energy signals
High energy signals
Activate anabolic pathways
ATP NADH NADPH FADH2
What is the low energy signals
Low energy signals
Activate catabolic pathways
ADP, AMP NAD+ NADP+ FAD
What is Adenylate Kinase (myokinase)
Enzyme that converts
2ADP —> ATP + AMP
Switched on when ATP levels are dropping
What does a boost in AMP trigger
AMP increases ATP generation by glycolysis
What does AMP and ADP activate
AMP (and ADP) is also an important activator of
AMP dependent kinase
that regulates gene expression switching from anabolic to catabolic pathways
(anabolic - switches of with elevated AMP)
(catabolic - switched on with elevated AMP levels)
What happens when puppy of energy exceeds demand
When supply exceeds demand, energy is most often stored in the form of polymer macromolecules of fuel molecules, e.g. glycogen, triglyceride
What is creatine phosphate used for
Creatine + ATP <——> Creatine Phosphate + ADP
Uses Creatine Kinase Enzyme
- When ATP concentrations ([ATP]) are high, creatine phosphate is formed
- If ATP concentration falls suddenly, the reaction reverses providing short term boost to [ATP]
What is Creatine Kinase (CK)
What is it used for
Creatine Kinase (CK) - a marker of muscle damage
- Creatine kinase is made up of two subunits – M and B – and because it is a cytosolic enzyme will appear in blood soon after cell damage.
- 3 Different isoform combinations are possible – MM, BB and MB.
- CK-MB used to be used as a marker for cardiac muscle damage (e.g. myocardial infarction – but it is not very specific and has been superseded by cardiac specific troponin tests)
- CK activity is still a sensitive serum marker for any condition that causes myocyte damage and is used routinely for patients with suspected muscle injury or unexplained muscle weakness (myopathy).
What is Creatinine
Creatinine is a Breakdown product of creatine (and creatine phosphate)
- Produced by a spontaneous reaction at a constant rate
– unless muscle is wasting
What is creatinine used for clinically
- Excreted via kidneys
- Used to assess kidney function
- Creatinine excretion per 24h is proportional to muscle mass of the individual
– Provides a measure of muscle mass - Creatinine concentration in urine is a marker of urine dilution
- Can be used to estimate true urinary loss of many substances – E.g. hormones in pregnancy
