Metabolism Flashcards
Metabolism
- Sum total of all chemical reactions occurring in a cell. Involves acquisition/use of energy (capacity to do work).
- Anabolism (synthesis) and catabolism (degradation) involved
Metabolism in Animals
Animals use the energy stored in chemical bonds of organic molecules to accomplish biological work
Activation energy
Energy input required by most chemical reactions to start
Catalyst
Substance that decreases activation energy of a reaction, and therefore accelerates its rate, but does not get used up during the reaction
Enzyme catalysts
Necessary to aid in metabolic reactions occuring at temperatures and concentrations too low
Enzymes
- Lower the activation energy barrier.
2. Several enzymes operate in sets called enzymatic pathways.
Enzyme Specificity
Enzymes = proteins.
Have active site defined by unique molecular shape, that allows it to combine with a specific substrate (reactant).
Regulation of Metabolism
Metabolism regulated:
either by relative concentration of substrates & products OR by the quantity & activity of enzymes.
Enzymes
Activated or inhibited by changing the protein shape w/ cofactors (vitamins & metal ions), concentration of substrates & products, temperature, pH, etc.
Feedback inhibition
when the final product of a metabolic pathway inhibits the first enzyme in the pathway
ATP (adenosine triphosphate)
ATP stores & releases energy for driving cellular reactions.
NOT A FUEL just a temporary store
Breakdown of ATP is coupled with synthesis of something else
Synthesis of ATP is coupled with breakdown of something else
Metabolic reactions
coupled reactions consisting of an anabolic and a catabolic reaction
Cellular respiration
Coupled Oxidation-reduction (redox) reactions provide energy to a cell
Oxidation
involves electron donor ie hydrogen atoms of a carb molecule
Reduction
involves electron acceptor ie O2
oxidation of fuel molecule
energy is released and ATP formed
Aerobic respiration
when final electron acceptor is O2
Anaerobic respiration
if final electron receptor is some other molecule (ie lactic acid or ethanol)
Why anaerobic respiration still persists
Used by:
- many microorganisms living in O2 depleted habitats
- skeletal muscles of vertebrates during short bursts of activity. White muscle fibers have few mitochondria and primarily use anaerobic metabolism
- diving birds and diving mammals
- some parasitic animals
glycolysis
the enzymatic breakdown of a carbohydrate (as glucose) by way of phosphate derivatives; produces pyruvic or lactic acid ATP.
Acetyl-CoA (acetyl coenzyme A)
important molecule whose main function is to convey the carbon atoms within the acetyl group to the citric acid cycle (Krebs cycle) to be oxidized for energy production.
Krebs cycle
the sequence of reactions that generate energy during the process of aerobic respiration. It takes place in the mitochondria, consuming O2, producing CO2 & H20 as waste products, & converting ADP to energy-rich ATP.
Glucose + 2 ATP + 36 ADP + 36 P + 6 O2—> 6 CO2 + 2 ADP + 36 ATP + 6 H20
Shows how glucose combines with ATP and phosphates and O2; O2 is consumed, ATP & ADP is produced & CO2 & H20 are waste
Lipid Metabolism
Stored fats:
- greatest reserve fuel in body
- Produce > ATPs than carbs becuase contain > Hydrogen (electron donor in electron transport chain that –> ATP)
- Triglycerides (most of the fats) are hydrolyzed to glycerol & fatty acids. Glycerol enters glycolytic pathway & fatty acids enters Krebs cycle
