Energy and Metabolism Flashcards
what is the first law of thermodynamics
energy can neither be created nor destroyed but is transferred from one form to another or from one place or another
what is the second law of thermodynamics
energy doesn’t transform without entropy in the universe (usually lost as heat)
what is metabolism
the sum of all chemical reactions in which energy is made available and consumed in the body
examples of metabolism
oxidation of fuel to CO2 and water
- achieved by a series of biochemical reactions
production of energy (ATP) and loss of energy (heat)
what does the body need energy for
contraction of muscle
- skeletal, cardiac, smooth -> blood vessels and gut
accumulation of ions and other molecules against conc. gradients (nerve impulses)
biosynthesis -> building of tissues
waste disposal -> getting rid of the end products of bodily function
generation of heat -> maintenance of body temperature
reaction to create glucose 6 phosphate
glucose + PO4^2 –> glucose 6 phosphate
reaction cannot happen spontaneously because the energy of the products is higher than the sum of the energy of the reactants
in order for this equation to become spontaneous, we need to couple it with another equation
ATP -> ADP + PO4 2-
rules of gibbs free energy
if the product contains more energy than the substrate -> delta G is +ve
if the product contains less energy than the substrate -> delta G is -ve
is the catabolism of nutrients exergonic or endogonic?
exergonic
the cells can harness this energy as ATP
ATP basic info
energy currency of living organisms
- hydrolysis to give ADP and Pi liberates a large amount of energy
ATP equations
ATP (+ H2O) –> ADP + Pi
- delta G = -30kJ/mol
- in cells, delta G = -50kJ/mol
ADP + Pi –> ATP + H2O
- delta G = +30kJ/mol
- in cells +50 kJ/mol
endergonic definition
products of greater free energy than the reactants; non-spontaneous
free energy definition
the energy available in a system to do useful work
exergonic definition
reactants of greater free energy than the products; spontaneous
The tricarboxylic acid cycle (TCA)
also known as Krebs cycle
acetyl CoA (2 carbon) condenses with oxaloacetate (4 carbon) to produce citrate (6 carbon)
this occurs in 2 phases
- deoxycarbylation (citrate -> succinyl CoA (4 C )) -> 2 C molecules lost as CO2
- reductive (succinyl CoA to oxaloacetate)
what is the overall reaction for TCA
acetyl CoA + 3NAD+ + FAD + GDP + Pi + 2H2) –> CoA + 2CO2 + 3NADH + FADH2 + GTP (ATP) + 3H+
what are the products of 1 turn of TCA cycle
3 x NADH
1 x FADH2
^ molecules produce ATP in the ETC
what are the main components of the ETC
four protein complexes
ATP synthase
intermembrane space in mitochondria
FADH2
NADH
H+
co-enzyme Q
cytochrome C
progress of e- through the ETC
intermembrane has a higher conc. of protons because of pump
1- co-enzymes donate 2e- and H+ to the ETC
2- electrons passed through redox centre (in the complex)
- moved between redox centres
- each one has a higher affinity
- produces ATP (used to pump protons against conc. gradient)
3- co-enzyme Q passes the electrons to the next protein complex (1-> 2 -> 3)
4- cytochrome C -> complex 4
5- when e- reaches the end of complex 4
- 2H+ + 1/2O2 -> H2O
O2 is the terminal electron carrier
where does FADH2 enter the ETC
complex 2
what is oxidative phosphorylation
ATP synthase
- only way H+ can get back into matrix
- ADP + Pi -> ATP
- main generator of ATP
what is the ATP yield of the TCA (incl. ETC)
produced by substrate level phosphorylation: 1 GTP (equal to ATP) + 3NADH + 1FADH
generally accepted that each___ oxidised by the ETC produces
- NADH = 2.5 ATP
- FADH2 = 1.5 ATP
- therefore, the total yield/ acetyl CoA is 1 + (3 x 2.5) + (1 x 1.5) = 10 ATP
what is glycolysis
glucose -> pyruvate (3 C)
occurs in the cytosol of cells
- can occur in all cells (e.g. RBCs and cells with shortage of O2)
exogonic reaction
2 phases
- endogonic (ATP investment)
- exogonic (generation)
describe the process of ATP investment (stage 1 of glycolysis)
glucose –> glucose 6 phosphate
- hexokinase, uses 1 ATP
glucose 6-phosphate –> fructose 6 phosphate
- phosphoglucose isomerase (reversable)
fructose 6 phosphate –> fructose 1,6 bisphosphate
- phosphofructokinase, uses 1 ATP
fructose 1,6 bisphosphate –> dihydroxyacetone phosphate
- triose phosphate isomerase
OR
fructose 1,6 phosphate –> glyceraldehyde 3 phosphate
- aldolase
describe the process of generation (stage 2 of glycolysis)
glyceraldehyde 3 phosphate –> 1,3 bisphosphoglyceral
- glyceraldehyde 3-phosphate dehydrogenase, catalyses PNAD+ conversion to NADH (reversible)
1,3 bisphosphoglyceral –> 3-phosphoglycerate
- phosphoglycerate kinase, catalyses ADP conversion to ATP (reversible)
3-phosphoglycerate –> 2-phosphoglycerate
- phosphoglycerate mutase (reversible)
2-phosphoglycerate –> phosphoenolpyruvate
- enolase, produces H2O (reversible)
phosphoenolpyruvate –> pyruvate
- pyruvate kinase, catalyses ADP -> ATP
outline the anaerobic conditions of glycolysis
pyruvate is converted to lactate
- regenerated NAD+ (oxidised form) to keep glycolysis going
- ATP is localised -> each cell needs to make it for itself
describe fermentation
glucose –> 2 pyruvate
- glycolysis
- 2ADP + 2Pi –> 2ATP
- 2NAD+ + 2NADH +2H+ ]
2 pyruvate –> 2 lactate
- 2NADH + 2H+ -> 2NAH+
overall equation for anaerobic glycolysis
C6H12O6 + 2ADP + 2Pi –> 2 lactate + 2ATP
describe process of the link reaction
pyruvate is transported into the mitochondrion and converted to acetyl CoA by the action of pyruvate dehydrogenase
(1- pyruvate enters the mitochondrion through a transport protein
2- CO2 produced
3- NAD+ –> NADH + H+
4- CoA reacts
5- acetyl CoA produced)
overall reaction of the link reaction
CH2-CO-CO2- (pyruvate) + NAD+ + CoASH -> CH3-CO-SCoA (acetyl CoA) + CO2 + NADH
describe fatty acid degradation
beta-oxidation
1- 16 C long chain (palmitic acid)
2- carbon backbone cleaved between the alpha and beta carbons (proximal to the carboxy terminus)
3- forms acetyl CoA
4- oxidation reaction
happens 7 times
produces 8 acetyl CoA molecules
overall products of one C16 molecule (palmitic acid)
b-oxid -> 7 x NADH + 7 x FADH2 + 8 x AcCoA
TCA -> 8 x (3 x NADH) + (1 x FADH2) + (1 x ATP)
total -> 31 NADH + 15 FADH2 + (8 x ATP) - 2 x ATP + (31 x 2.5 ATP) + (15 x 1.5 ATP) + 6 ATP
= 106 ATP
simplified process of fatty acid metabolism
1- fatty acids are transported in the blood as a complex with albumin (most prolific plasma protein) (to make it hydrophilic) and are taken up by cells for oxidation
2- fatty acid modification (essential for entry into mitochondria) and entry into mitochondria
3- B-oxidation leading to energy (ATP) formation
detailed fatty acid metabolism
1- free fatty acid + CoA + 2ATP –> fatty acyl CoA (acyl-CoA synthase)
2- fatty acyl CoA –> fatty acyl carnitine (carnitine -> CoA)
3- fatty acyl carnitine enters mitochondrial matrix through transport protein
4- fatty acyl carnitine –> fatty acyl CoA (CoA –> carnitine)
5- fatty acid degradation
what are the two stages of protein metabolism
transamination and deamination
describe transamination
important because it releases the carbon backbone to be turned into intermediates of the Krebs cycle
a-ketoglutarate most common to accept residue
- produces glutamate (PROTEIN) and a-ketoacid
- alanine -> pyruvate
- aspartate -> oxaloacetate
- all the intermediates of the Krebs cycle
describe deamination
in the liver
production of ammonium
cells have to be able to remove ammonium -> turns into urea
glutamate -> a-ketoglutarate
what are glucogenic acids
glucose
pyruvate
oxaloacetate
intermediate of TCA
what are ketogenic acids
fatty acids
acetyl CoA
acetoacetyl CoA
only lysine and leucine are totally ketogenic
what happens to a-ketoacids
after they have been converted into intermediates they then
- TCA cycle
- recycled for fatty acid synthesis
gluconeogenesis
metabolic adaptations to starvation
1- fat -> triglycerides in adipose tissue which is sufficient to prolong life for 3 months
2- protein -> provides approx. 14 days’ worth of energy but is spared for as long as possible to permit mobility
other sources: glycogen, glucose
what is the basal energy expenditure (BEE)
used to estimate the energy required to maintain basic functions
- also known as basal metabolic rate (BMR)
- when the person is lying down, relaxed (not asleep), in a normal ambient temperature
what is the equation for calculation BEE for males
BEE = 66.5 + 13.75W + 5.003H - 6.775A
what is the equation for calculation of BEE in females
BEE = 655.1 + 9.563W + 1.850H - 4.676A
BMI basic info
body mass index
BMI = W/H2
- weight in Kg
- height in M
<20 = underweight
20-25 = ideal weight
25-30 = overweight
>30 = obese
why is the BMI not always a good measure of an individual
doesn’t account for muscle mass/ cardiovascular condition
although helpful, should be used with some degree of caution
fatigue symptoms
tiredness
lack of energy
weakness
exhaustion
sleepiness
some of the causes are metabolic in nature
what causes fatigue in short bursts of exercise
phosphocreatine depletion
what causes fatigue in middle bursts of exercise
phosphocreatine depletion and proton accumulation
what causes fatigue in long times of exercise
glycogen depletion
explanation of phosphocreatine depletion
entropy and loss of energy of heat
- depletes energy stores in the body
- phosphocreatine used when ATP is depleted (only for a short time)
- stored ATP only lasts for about 2 seconds in sprinting
explanation of glycogen depletion
anaerobic glycolysis of stored glycogen starts to occur as the length of run increases
- lactic acid
- reduces the pH of the blood
- only short time
what happens in intense sustained exercise
glycogen stores are depleted
hitting the wall
move to fat metabolism
