Metabolism Flashcards
what is metabolism?
- sum of reactions that convert nutrients into energy and complex molecules
- catalysed by enzymes (proteins)
- organised into metabolic pathways
- pathways operate in coordinated manner, reactions effect other reactoins
metabolic pathways
- proceed stepwise
- transferring substrates into products using enzymes (catalyst)
NAD+
- hydrogen is released from organic molecules in food
- this is catalysed by dehydrogenase
- collected by NAD+
- good at reversibly carrying e- (H+)
- 2 e- and 1 proton stored in NAD+
stepwise energy harvest via NAD+
- in cellular respiration, glucose is broken down
- e- from glucose transferred to NAD+
- transfer of e- during chemical reactions releases the stored energy
- energy is ultimately used to create ATP
principle #1 of metabolism
- mass is not converted to energy in a cell
- mass is conserved during metabolic reactions
principle #2 of metabolism
- cells need a continual input of energy to stay organised and move
- energy is need to break covalent bonds
- a thermodynamic reaction (-∆G) can drive an unfavourable reaction (+∆G)
Free energy changes
- exergonic reaction energy is released (-∆G)
- endergonic reaction energy is needed (+∆G)
- can couple together so exergonic reaction cause endergonic reaction (COUPLING)
∆G in the ATP cycle
- energy is released when hydrolysing ATP (endergonic)
- energy is needed to synthesis ATP from ADP and Pi
catabolism vs anabolism
- catabolism is the breakdown of molecules into smaller units and releases energy (exergonic)
- anabolism is the synthesis of molecules and requires energy for the reaction to occurs (endergonic)
Free Energy
- energy released in a chemical reaction that is available to do work
- (-)∆G reaction will proceed forwards
- ∆G depends on
- –conc of reactants and products
- – strength of all bonds formed and broken
stages of Glycolysis
Phase 1) priming - fructose is added to the ends of the glucose molecule - uses 2 ATP Phase 2) cleavage - break molecule in half - two molecules with 3 C and 1 P Phase 3) energy generation - transform into 2 pyruvate molecules - 4 ATP produced - yeilds NADH - next action depends on O2 availability
phosphocreatine system
PC + ADP + H(+) —(protein kinase)—> creatine + ATP
- note that H+ is being consumed
- therefore, [H+] decrease and pH increase
metabolic cooperation between liver and skeletal muscles
Cori Cycle
- lactate from muscle glycolysis goes into blood stream
- some travels to liver
- gluconeogenesis in liver (lactate to glucose) (use ATP)
- glucose goes into blood stream
- back to exercising muscle
Glucose-alanine cycle
- pyruvate from muscle glycolysis transaminated in muscle (pyruvate to alanine)
- alanine goes in blood to liver
- amino group removed off alanine (now pyruvate)
- pyruvate undergo gluconeogenesis (now glucose)
sources of fuel for exercise
Carbohydrates - blood glucose - cell glycogen Fats - plasma FFA (from adipose tissue) - intramuscular triglycerides Proteins - only small contribution Blood lactate - cori cyclw
the citric acid cycle
- although no O2 is used in the cycle, O2 is used to re-oxidise NADH and FADH2
- there is limited amounts of e- carrier coenzymes, therefore must be reused
