Lecture 8 - Bioenergetics 2 Flashcards
different processes that oxidize carbohydrates
Outside mitochondira/in cytosol
Glycolysis
Inside mitochondria
Krebs Cycle
Oxidative Phosphorylation
glycolysis
- > can occur with or without oxygen
- > produces pyruvic acid which will then be converted into acetyl CoA (and FFA) then sent to the Krebs cycle
- > 3 net moles of ATP are created per mole of glycogen OR 2 net moles of ATP per one mol of glucose
oxidation of Pyruvate to form Aceyl CoA
Pyruvate + NAD + CoA = Acetyl CoA + NADH + CO2
Krebs cycle
- > starts with acetyl coA from glycolysis
- > will do 2 kreb cycles
- > needs oxygen and will yield net 2 ATP
electron transport chain
- > H by-products from glycolysis and krebs cycles will then be send to the ETC in the mitochondria, producing net 28 ATP
- > they are carried by cytochromes
*these hydrogen cannot stay in the system as it will be too acidic, so they are used by ETC to from ATP
how is oxidative phosphorylation regulated
by a negative feedback loop
- > if theres too much ATP, ATPase levels will increase and breakdown/lower ATP levels
energy yield from the oxidation of carbohydrates
*combined from Glycolysis, krebs cycle, and oxidative phosphorylation
- > the complete oxidation of glucose can yield 32 molecules of ATP, or 33 are produced from 1 molecule of muscle glycogen
(34 ATP produced - 2ATP cost = 32)
Oxidation of Fat
- > tryglycerides (fat) undergo lipolysis (carried out by lipase) to produce 1 molecule of glycerol and 3 FFA molecules
- > FFA are then carried through the blood and enter muscle fibres via simple diffusion or transporter facilitated diffusion
- > before FFA are able to be broken down and used for energy, then have to be converted into acetyl coA in the mitochondria (beta-oxidation)
- > the newly converted Aceytl coA will then follow the same path as glucose phosphorylation
beta oxidation
breaks acetyl groups off of the carbon chains of the FFA
- > number of steps required depends on the number of carbons in the FFA (usually 14-24 carbons)
- > some H generated from beta-oxidation will undergo oxidative phosphorylation
krebs cycle and the ETC during the oxidation of fat
- > acetyl coA formed during beta-oxidation starts out the krebs cycle, following the same path as carb breakdown
- > ETC does the same thing
- > this will require more O2 as fuel as FFA contain considerably more carbon molecules (C+O = CO2 by product)
advantage of fat breakdown over carb breakdown
FFAs have more carbon than glucose, which produces more acetyl coA
- > so more ACoA enters the kreb cycle, producing more electrons to be sent to ETC and produce more ATP
White vs Brown Adipose Tissue
Brown Adipose
- > used in hibernation
- > used to transfer energy from food directly into heat
- > contains many mitochondria, which gives it the brown appearance
White adipose
- > used form lipid storage and breakdown
oxidation of protein
- > only used in situations of starvation
- > amino acids are converted into glucose via gluconeogenesis OR converted into various intermediates (such as pyruvate or acetyl coA)
- > energy yield is difficult to determine be cause proteins contain nitrogen, and when N is release they are used to form new AA or converted into urea and secreted (which requires ATP)
using lactic acid as a source of energy during exercise
lactic acid is produces by glycolysis and removed from the cell through oxidation
- > can be directly oxidized in the muscle fibre where it was produced (this occurs mostly in cells with high density of mitochondria)
- > lactate produced in a muscle cell can be transported and used elsewhere (lactate shuttle)
- > lactic acid produced can be transported by the blood to the liver where it is reconverted to pyruvic acid and back to glucose via gluconeogenesis (this is called the Cori Cycle)
Crossover Effect
- > describes the balance between carb and fat metabolism during sustained exercise
- > during high (+70% VO2max) carbs serve as the primary substrate
- > at around 60-65% they are both being used at the same level
- > the crossover point is affected by the exercise intensity and endurance training status
