Metabolism and its Control Flashcards
what is metabolism?
Chemical processes that occur within a living organism in order to maintain life.
what is a metabolic pathway?
A metabolic pathway starts with a specific metabolite and ends with a product. The first molecule is converted into the last by a chain of enzymatically catalysed reactions. E.g.
Glycolysis: Glucose –> Acetyl-CoA
TCA (Krebs) Cycle: Acetyl-CoA –> CO2
what is a catabolic pathway?
when a complex molecule is BROKEN down to a smaller one and energy is RELEASED
what is an anabolic pathway?
complex molecule is BUILT from simple one which requires energy in the form of ATP
define oxidation
acquisition of oxygen, or loss of electrons, or loss of hydrogen (OIL RIG)
define reduction
Loss of oxygen, or gain of electrons, or gain of hydrogen (OIL RIG)
what are the 7 different important metabolic processes?
Hydrolysis: Adding water to break apart a molecule
Dehydration: Loss of water
Phosphorylation: Addition a phosphate group
Dephosphorylation: Removal of a phosphate group
Carboxylation: addition of a CO2 molecule
Decarboxylation: removal of a CO2 molecule
Ligation reaction: Joining of two molecules
what is ATP and what is its structure?
Adenosine triphosphate – formed from 3 phosphates, ribose sugar, & adenine base
where does ATP store energy?
The ATP molecule stores energy in 2 phosphoanhydride bonds
released via hydrolysis of bond.
how much energy does hydrolysis of ATP create?
Hydrolysis at physiological pH releases 7.3 kcal
what are the 2 ways in which ATP can be formed?
1) substrate-level phosphorylation- doesn’t require oxygen
2) oxidative phosphorylation- requires oxygen
what happens to ATP when its left in room temp for too long?
ATP will slowly release inorganic phosphate and be converted to ADP and eventually AMP
what is the equation for respiration?
i.e how much of each product is formed?
C6H12O6 + 6O2 –> 6CO2 + 6H2O + 31ATP
what are the 4 different stages in the production of ATP?
Glycolysis
Oxidative decarboxylation (Link reaction) TCA cycle (Krebs cycle)
Electron transport chain (oxidative phosphorylation)
describe the process of glycolysis
Glucose is primed with 2 phosphorylation reactions & one isomerisation reaction to form fructose-1,6-bisphosphate
fructose-1,6-bisphosphate split to form 2x GA-3-P
2x GA-3-P undergoes dehydrogenation and phosphorylation (catalysed by an enzyme).
2 x NAD coenzymes accept the removed hydrogens forming 2 x NADH (reduced NAD)
The resulting product 2 x 1,3-BGA then undergoes dephosphorylation twice forming 2x pyruvate and 4x ATP molecules.
what are the overall products produced in glycolysis?
Glucose –> 2 x pyruvate
2 ADP –> 2 x ATP (net yield of 2 x ATP and 2 x NADH bc 2 ATP molecules were used but 4 were made)
2 NAD –> 2 NADH
where does glycolysis occur?
in the cytosol
what do kinase enzymes do in glycolysis?
Kinase enzymes transfer a phosphate to a molecule – this creates a high energy phosphate bond
what 2 phases is glycolysis split into?
Priming
Splitting
what is priming?
ATP is used up in this phase
break down ATP to phosphorylate glucose
then phosphorylate fructose-6 phosphate to form fructose-1,6-bisphosphate
what is splitting?
4 ATP molecules are produced during this phase
when would lactate levels rise in the body?
exercising skeletal muscle –> increased lactate therefore muscle pain
coronary arteries blocked by atherosclerosis –> insufficient O2 supply to cardiomyocytes leading to increased lactate therefore angina pectoris (chest pains)
what needs to be regenerated in order for glycolysis to continue?
NAD+
how is NAD+ regenerated in aerobic and anaerobic respiration?
In aerobic respiration this is done using oxygen
In anaerobic respiration this is done in another way
- Lactate fermentation
- Alcoholic fermentation
what happens during lactate fermentation?
1) glycolysis –> pyruvate: acts as a hydrogen acceptor taking the hydrogen from reduced NAD, catalysed by the enzyme lactate dehydrogenase.
2) The pyruvate is converted to lactate (lactic acid) and NAD is regenerated.
- used to keep glycolysis going so a small quantity of ATP is still synthesised.
3) Lactic acid is converted back into glucose in the liver (gluconeogenesis) but oxygen is needed to complete this process.
^^ This is the reason for the oxygen debt (and the need to breathe heavily) after exercise.
what happens during alcoholic fermentation?
Alcoholic fermentation is non-reversible.
1) Pyruvate (produced by glycolysis) is first converted to ethanal (acetaldehyde), catalysed by the enzyme pyruvate decarboxylase. 1 x CO2 is produced as well.
2) Ethanal can then accept a hydrogen atom from reduced NAD (catalysed by Alcohol dehydrogenases),becoming ethanol.
3) The regenerated NAD can then continue to act as a coenzyme and glycolysis can continue.
what is the cori cycle?
a metabolic pathway in which lactate, produced by anaerobic glycolysis in muscles, is transported to the liver and converted to glucose, which then returns to the muscles and is converted back to lactate.
what do most cells have in their PM?
Almost all cells have high levels of pyruvate & lactate transporters in their plasma membranes
how does the liver form glucose from lactate?
1) The lactate is first converted into pyruvate
2) Pyruvate is then converted into Glucose 6-phophate (gluconeogenesis)
3) Glucose 6-phospahte is then converted into glucose
what is gluconeogenesis?
synthesis of glucose from pyruvate
reverse of glycolysis
what enzymes are used in gluconeogenesis?
phosphofructokinase
fructose-1,6-bisphosphatase
control whether the glycolysis or gluconeogenesis pathway is followed
how is glucose produced from pyruvate during gluconeogenesis?
1) phosphofructokinase converts fructose-6-phosphate into fructose 1-6 bisphosphate to then follow glycolysis and produce pyruvate
2) fructose-1,6-bisphosphatase converts fructose 1-6 bisphosphate into fructose 6 phosphate to then follow gluconeogenesis and produce glucose.
what happens to phosphofructokinase and fructose-1,6-bisphosphatase at high ATP concentrations?
at high ATP conc phosphofructokinase is inhibited & fructose-1,6-bisphosphatase is activated –> gluconeogenesis occurs