Overview of Metabolism Flashcards
What is metabolism?
Series of enzyme reactions within cells for converting
fuel molecules into ‘useful energy’
The enzyme reactions of synthesis/breakdown/interconversion of essential biomolecules
What is catabolism?
the breakdown of complex molecules in living organisms to form simpler ones, together with the release of energy
How can you identify catabolic reaction?
Names end in ‘lysis’
Name 3 e.g.s of catabolism
- glycolysis
- lipolysis
- glycogenolysis
What does catabolism generate?
ATP & NADH – energy storage mol
Where does catabolism mostly occur?
Mitochondria
What is anabolism?
the synthesis of complex molecules in living organisms from simpler ones together with the storage of energy
How can you identify anabolic reaction?
Names end in ‘genesis’
Name 3 e.g.s of anabolism
- gluconeogen
- lipogen
- glycogenesis
What does anabolism use?
ATP, GTP, UTP
Where does anabolism mostly occur?
Cytosol
What do pathways of glycolysis and TCA cycle act together to do?
convert glucose to CO2
What is chem reaction for aerobic resp?
C6H12O6 + + 6O2 —> 6CO2 + 6H2O + 30 ATP (+2 GTP)
What do the TCA cycle and glycolysis pathways do through mit resp?
provide energy for tissues, such as muscle, kidney and brain
What are 4 stages of cat for glucose?
- Glycolysis
- Link reaction
- TCA cycle
- Ox phos
What are 3 stages of cat for FA?
- Beta ox
- TCA cycle
- Ox phos
What are 3 stages of cat for aa?
- Transamination
- TCA cycle
- Ox phos
What occurs during glycolysis?
Glucose converted to pyruvate
What occurs during LR?
Pyruvate converted to acetate
What occurs during TCA cycle?
- ox of acetate to CO2
- production of NADH + FADH2
What occurs during ox phos?
- H + O2 —> H2O
- ADP + Pi —> ATP
What occurs during beta ox?
FA converted to acetate
What occurs during transamination?
aa converted to acetate
When are aa used in met?
When starving as last resort
Why can’t get energy from anything fully ox e.g. CO2?
contains no H
Why can from fully red mol e.g. CH4?
contains H - can gen energy from combustion
Where does glycolysis occur?
Cytoplasm
Where does Beta ox occur?
Matrix of mit
Where does LR occur?
Matrix of mit
Where does TCA cycle occur?
Matrix of mit
Where does ox phos occur?
Inner mit mem
How do FAs get into cells?
FAs bind to albumin in blood and then taken up by FA binding protein inside cell and probs transporter inbetween
How does glucose get into cells?
Through specific glucose transporters
What are 2 properties of ATP?
- Chemically stable at pH 6-9
- Structural features e.g. NH2 group recognised by specific proteins, enzymes, etc
What does ATP hydrolysis give?
ADP + Pi + H+ + energy
How are the bonds in ATP formed, what type of bonds are they and why are they special?
- phosphoric acid + phosphoric acid – form anhydride bond
– high energy
Which phosphoanhydride bond is broken in ATP hydrolysis?
– only last 2 bonds and not one between ribose and 1st phosphate
What is the energy available from ATP hydrolysis used for?
- cellular work
- chem syn
When 2 phosphoanhydride bonds are broken at ATP, what is the resulting mol?
AMP
What is free energy of reaction of ATP hydrolysis?
30.5 kJ mol-1 (approx 31 kJ of energy per mol)
How does ATP affect equilibria of coupled reactions and e.g?
- shifts it by a factor of 10 to power 8
- e.g. A to B is unfavourable reaction – use energy from ATP hydrolysis to make it go
- A B now A + ATP + H2O —> B + ADP + Pi + H+
What are functions of ATP?
- Used directly in cell motility and contraction e.g. myosin, dynein e.g. of proteins that take this energy and use it for contraction
- Used in Na+ / K+ pumps, active transport systems & metabolic control
- phosphorylation of proteins
- Used in metabolism to add Pi to metabolic intermediates e.g. glucose to keep it in the cell during glycolysis
What are gen features of met pathways?
- Can’t go directly from sub e.g. glucose to product e.g. CO2
- has to be series of multiple reactions with pathways using multiple enz
What is the rate of a biochemical reaction dependent on?
enzyme activity
What is the direction (equilibrium) of a reaction dependent on?
the properties of the chemical molecules themselves.
How do enz affect reactions and how?
- accelerate rate of reaction so reaction that normally wouldn’t occur is accelerated
- Enz lower Ea bc if its not lowered, reaction can’t occur bc its too high
How can rate of enz reaction be regulated by sub?
by altering the availability of the substrate, (e.g. by increasing the transport system into the cell – more sub coming in)
How can rate of enz reaction be regulated enz?
- by increasing the amount of enzyme present in the cell
- by increasing the rate of transcription from the gene in DNA into mRNA
- ‘up regulation’ or ‘induction’ – inc reaction rate by inc enz expression
- ‘down regulation’ or ‘repression’ e.g. inhibitors to stop reaction occuring
What are Regulation Mechanisms for Enzymes already present in the Cell and e.g.?
- Interconversion of ‘active’ & ‘inactive’ forms of key enzymes
- e.g. Protein kinase uses ATP to put phosphate on OH group of inactive enz – form ester bond and now phosphorylated form of enz (active)
- remove phosphate using protein phosphatase
For normal enz, what does velocity depend on and why?
- S conc
- Low S conc means not all sites occupied so velocity inc
- until get to high S conc and enz working at max velocity so can’t inc any further
- Hyperbolic graph
How do allosteric enz differ to normal enz?
- have:
- activating site
- S binding site
- inhibitory site
- Way of reg enz through activator/inhibitor
- Sigmoid graph e.g. Hb
What do met reactions require?
- fuel mol (sub/intermediates)
- enz
- cofactors e.g. activating ions - Mg2+, Cl-, Zn2+ or coenz/prosthetic groups
What is role of ATP for?
- ‘high energy’ cofactor in the cell for kinase enzymes
- driving mechanical events such as pumps, transporters, contractile events & movement
- ATP —> ADP + Pi
What are other ‘high energy’ nucleotide cofactors used for and e.g?
- drive specific biosynthetic reactions
– enz recognise them for certain reactions - UTP drives the synthesis of complex sugars
- GTP drives the synthesis of proteins, also couples hormone receptors to cell surface for hormone to act in cell
