Chapter 6 - Energy Transfer in the Body Flashcards
What is the Energy Currency of the Body?
- ATP
What provides major sources of potential energy?
- Macronutrients
How does ADP form?
- When ATP joins with water
What enzyme catalyzes the reaction of ATP and Water to form ADP?
- Adenosine Triphosphatase (ATPase)
What are the Cells’ two major energy-transforming activities?
- Extract potential energy from food/conserve it within ATP bonds
- Extract/transfer chemical energy in ATP to power biological work
How much ATP does the body store at resting condition?
- 80-100g ATP
How long can resting stores of ATP in the body provide energy?
2-3 seconds of Maximal Exercise
Which ways can the mitochondria produce ATP?
Methods
- Citric Acid Cycle
- Respiratory Chain (Aerobic)
Fuel sources
- fatty acids
- Pyruvate from glucose
- Some deaminated amino acids
Which ways for ATP production occur in the Cytosol?
- anaerobic glycolysis
-using glucose and glycogen - adenylate kinase
- Glycerol
- Some Deamniated Amino Acids
- Phosphocreatine shuttle
Where does Aerobic ATP production occur?
- Mitochondria
Where does Anaerobic ATP production occur?
- Cytosol
Where does ATP production from phosphocreatine occur?
- Cytosol
What happens with the anaerobic splitting of a phosphate from Phosphocreatine?
- ATP resynthesis
How much Phosphocreatine do cells store compared to ATP?
- 4-6 times
How long can Phosphocreatine provide energy for?
- around 10s
What does Adenylate Kinase Reaction represent?
- single-enzyme mediated reaction for ATP
- 2 adp -> atp + amp
cellular oxidation: Where does most energy for phosphorylation derive from?
oxidation of:
- Carbohydrates
- Lipids
- Protein
cellular respiration: What do oxidation reactions do?
- Donate electrons
cellular respiration: What do Reduction reactions do?
- Accept Electrons
cellular respiration: What constitutes the biochemical mechanism that underlies energy metabolism?
- RedOx Reactions (oxidation - reduction)
cellular respiration: What do redox reactions provide from catabolism of stored macronutrients?
- Hydrogen Atoms
cellular respiration: what do the carrier molecules in mitochondria do?
- Remove electrons from hydrogen (oxidation)
- Pass them to oxygen (reduction)
- Synthesize ATP through redox
cellular oxidation: What catalyze’s hydrogen’s release from the nutrient substrate?
- substrate-specific dehydrogenase enzymes
cellular oxidation: What accepts pairs of electrons from hydrogen?
- coenzyme component of the dehydrogenase
cellular respiration: What happens when Nicotinamide Adenine Dinucleotide (NAD+) gains hydrogen and two electrons?
-Reduces to NADH
cellular respiration: What happens to the other Hydrogen when one pairs with NAD+?
- Appears in the cell fluid as H+
cellular respiration: How many electrons does Flavin Adenine Dinucleotide accept?
- Two
cellular oxidation: What are NAD+ and FAD?
- Electron Acceptors
electron transport: What are Cytochromes?
- A series of Iron-protein electron carriers dispersed on the inner membranes of the mitochondrion
electron transport: What do cytochromes do
pass pairs of electrons carried by NADH and FADH2 down the chain
electron transport: what is electron transport
final common pathway where electrons extracted from hydrogen pass to oxygen
electron transport: What drives the respiratory chain? How?
Oxygen
- serving as final electron acceptor to combine with hydrogen to form water
electron transport: What happens for each pair of hydrogen atoms that reach the cytochrome?
- Two Electrons flow down the chain and reduce to one atom of oxygen
electron transport: What is released during the passage of electrons down the chain?
- Enough energy to re-phosphorylate ADP to ATP`
oxidative phosphorylation: How does oxidative phosphorylation synthesize ATP?
- Transfer of electrons from NADH and FADH2 to oxygen
oxidative phosphorylation: How much ATP synthesis occurs in the respiratory chain by oxidative reactions coupled with phosphorylation?
> 90%
oxidative phosphorylation: How many coupling sites during the electron transport does energy transfer from NADH to ADP to reform ATP?
- three distinct places
oxidative phosphorylation: Why do only 2 ATP molecules form for each hydrogen pair oxidized from FADH2?
- FADH2 enters respiratory chain at lower energy level, beyond point of first ATP synthesis
oxidative phosphorylation: how much energy is generated since the shuttling of hydrogen in the electron transport chain requires energy?
On Average
- NADH produces 2.5 ATP
- FADH2 produces 1.5 ATP
How much energy does 1 mole of ATP formed from ADP + P conserve?
- 7kcal energy
What is the relative efficiency level for harnessing chemical energy via the electron transport oxidative phosphorylation?
- 34%
Coupling electron transport-oxidative phosphorylation: What is created by electron transport energy-releasing reactions in the mitochondria?
- Proton (H+) gradient across the inner mitochondrial membrane
What provides the electrochemical basis for coupling electron transport to oxidative phosphorylation to form ATP?
- energy from NADH and FAD2H are used to pump H+ into intermembrane space
- flow of H+ into mitochondria matrix down gradient generates energy to rephosphorylate ADP
Which three prerequisites exist for continual re-synthesis of ATP during coupled oxidative phosphorylation?
- Tissue availability of NADH and FADH2
- Presence of oxygen in tissue (oxidizing agent)
- Sufficient concentration of enzyme and mitochondria to ensure energy transfer reactions proceed at appropriate rate
What are the 6 fuel sources?
- Phosphocreatine
- Anaerobic Glycolysis
- Blood Glucose (derived from liver glycogen)
- Triacylglycerol and Glycogen Molecules within muscles
- Free Fatty Acids (from liver triacylglycerols and adipocytes)
- Carbon Skeleton of Amino Acids
What controls the phosphorylation of ADP from PCr?
Enzyme Control
- Creatine Kinase
- Adenylate Kinase
Where are triacylglycerol’s stored?
- Within Muscle Cells
Where are the carbon skeletons of amino acids located?
- Intramuscular
- Liver-derived
What is the only macronutrient substrate whose stored energy generates ATP without oxygen?
- Carbohydrates
What is required for processing a large quantity of fat for energy?
- minimal carbohydrate breakdown
What aerobic breakdown occurs faster, Carbs or Fats?
- Carbs
What requires an uninterrupted supply of carbs to function properly?
- The central nervous system
If we received 100% of energy from 1 full glucose, how much energy would we get?
- 686 kcal
How do we determine the yield of ATP from the breakdown of 1 Glucose?
1 Full Glucose 100% - 686kcal
34% Efficiency - 686x0.34 = 233kcal
7.3kcal/mol
233kcal/7.3kcal/mol = 32mol
What happens to the rest of the potential energy after the breakdown of glucose?
- Dissipated as heat
What are the two forms of carbohydrate breakdown?
- Anaerobic Glycolysis
- Aerobic Glycolysis
How much energy is released from Anaerobic Glycolysis of Glucose?
- 5%
What results from the Anaerobic Glycolysis of Glucose?
by-product and energy release yield
- pyruvate-to-lactate formation
- Release of 5% energy
What is the result of Aerobic Glycolysis of Glucose?
- Pyruvate-to-Acetyl Coenzyme A- to Citric Acid Cycle and Electron transport chain
- Release of all available energy from glucose
What is the First Step of Anaerobic Glycolysis?
- Glucose to Glucose 6-phosphate
What does the conversion of Glucose to Glucose-6-phosphate require?
- 1 ATP
- Hexokinase Enzyme
What does the Enzyme Hexokinase catalyze?
- Glucose to Glucose-6-phosphate
What is not required to convert Glycogen to Glucose-6-phosphate?
- ATP
- Hexokinase Enzyme
Where does Glycolysis take place?
- Cytosol
What does Glucose break down into following Glycolysis? What does it net?
- 2 Pyruvates
- Gains 2 ATP
What does Glycogen break down into following glycolysis? what does it net?
- 2 Pyruvates
- Gain 3 ATP
What is Glycogenesis?
- Glycogen Synthesis
Explain Glycogenesis
Glycogen Synthesis
- Surplus Glucose forms Glycogen
- Occurs in low cellular activity
- Facilitate by Glycogen Synthase
- Glucose links to large Glycogen molecules
What is Glycogenolysis?
- Glycogen Breakdown
Explain Glycogenolysis.
Glycogen Breakdown
- Glycogen breakdown to glucose
- occurs in high cellular activity with glucose depletion
What regulates Glycolysis?
- Levels of substrate fructose 1,6-diphosphate
- high oxygen inhibits
- Concentration of 4 enzymes
What 4 enzymes regulate Glycolysis?
- Hexokinase
- Phosphorylase
- Phosphofructokinase
- Pyruvate Kinase
What anagram is used for remembering the 4 key enzymes that regulate glycolysis?
He - Hexokinase
Played - Phosphorylase
Poker - Phosphofructokinase
Poorly - Pyruvate Kinase
If Pyruvate converts to acetyl-CoA is it reversible?
- NO
When would pyruvate irreversibly convert to acetyl-CoA and enter the citric acid cycle?
- Abundance of Oxygen Present
What happens during strenuous physical activity, when energy demands exceed oxygen supply?
- The respiratory chain can’t process all hydrogen joined to NADH
What is required for the continued release of anaerobic energy?
- NAD+ to oxidize 3-phosphoglyceraldehyde
1-3 diphosphoglycerate is important for making pyruvate
How does NAD+ regenerate during anaerobic glycolysis? When would this be required?
How
- Pair of hydrogens from NADH combine with Pyruvate to form Lactate
When
- Energy demands exceed oxygen supply (strenuous physical activity)
What are the steps of Lactate formation? What is required? Is it Reversible?
Steps
- 2 hydrogens combine pyruvate
- Catalyzed by lactate dehydrogenase
Required
- Lactate Dehydrogenase Enzyme
Reversible
- YES
What happens to lactate formed from pyruvate?
Oxidized By:
- Neighbouring Muscle Fibers
- Heart
- Ventilatory Muscles
Indirect Precursor
- Liver Glycogen
Where would lactate form during rest and moderate physical activity?
- Red blood cells (no mitochondria)
- Muscle fibers with high glycolytic activity, and low enzymes
What happens once lactate forms in the in the muscle?
Two Routes:
- Diffuse in interstitial space/blood for buffering
- Provides Gluconeogenic substrate for glycogen synthesis
What is Gluconeogenesis? What does it result in?
Metabolic pathway
- Generation of glucose from non-carbohydrate carbon substrates
What are the two phases of Aerobic Glycolysis?
Phase 1
- Pyruvate from Glycolysis enters kreb cycle
Phase 2
- Electron Transport Chain
What happens in Phase 1 of Aerobic Glycolysis?
- Coenzyme A turns Pyruvate into Acetyl-CoA
- Reduced coenzymes (NADH and FADH2) transfer hydrogen to the electron transport chain
What happens in Phase 2 of Aerobic Glycolysis?
- Reduced Coenzyme Complexes become oxidized
What is the breakdown of ATP yield from Aerobic Glycolysis?
Yield
- 2 ATP Glycolysis
- 2 ATP Citric Acid Cycle
- 28 ATP Oxidative Phosphorylation
How much energy does fat supply ?
30-80%
What determines the amount of energy used from fat?
- Nutritional Status
- Level of Training
- Intensity/Duration of Physical Activity
What is the total energy reserve of fat in a young adult male?
- 60-100k kcal in adipocytes
- 3k kcal stored in intramuscular triacylglycerol
What are three specific energy sources from fat catabolism?
- Triacylglycerol stored in muscle near mitochondria
- Triacylglycerols in blood
- free fatty acids in blood
Where are circulating triacylglycerols stored?
- Lipoprotein Complexes
Where do circulating free fatty acids come from?
Mobilized from triacylglycerol in adipose tissue
What is required for the triacylglycerol to split into glycerol ad three fatty acids?
- Lipase Enzyme
How many steps does it take for lipid mobilization?
- 7 discrete steps
What are the 7 discrete steps of lipid mobilization?
- Breakdown triacylglycerol to free fatty acid.
- Transport of Free fatty acids in the blood
- Uptake of free fatty acids from blood to muscle
- Preparation of fatty acids for catabolism
- Entry of activated fatty acids into muscle mitochondria
- Breakdown of fatty acid to acetyl-CoA via beta oxidation and production of NADH and FADH2
- Couple oxidation in citric acid cycle and electron transport chain
How many ATP molecules does the complete oxidation of triacylglycerol molecules yield?
- 460ATP (depends on # of carbons)
What serves as the most plentiful source of potential energy?
- Stored Fat
When does fat become the primary energy fuel for exercise and recovery?
Intense, long-duration exercise depletes both blood glucose and muscle glycogen
What is the breakdown of ATP Yield from the complete breakdown of a triacylglycerol?
3 Fatty Acids (18-carbon each)
- 147 ATP per
- 147 x 3 = 441
1 Glycerol
- 19 ATP
- 441 + 19 ATP = 460 ATP
What pathways do fatty acids utilize for ATP synthesis?
- B-oxidation
- Citric Acid Cycle
What pathways do glycerols utilize for ATP synthesis?
- Glycolysis
- Citric Acid Cycle
What does it mean that “fat burns in a carbohydrate flame”?
- acetyl-CoA enters citric acid cycle by combing Oxaloacetate to form citrate
- Oxaloacetate breaks down over time
- Pyruvate can create more Oxaloacetate
- Without Oxaloacetate, no break down of Fatty Acids
- Without Pyruvate, no Oxaloacetate
How do amino acids enter the energy pathway?
Deamination
- removal of nitrogen
How do glucogenic amino acids contribute to energy?
When Deaminated
- yield intermediates for glucose synthesis
How do Ketogenic amino acids contribute to energy?
When Deaminated
- yield intermediate actyl-CoA or acetoacetate for TAG formation
What provides the vital link between macronutrient energy and chemical energy?
- Citric Acid Cycle
What are the metabolic interconversions between carbohydrates and other macronutrients?
- Carbs to lipids (lipogenesis)
- lipids to nonessential amino acids
- proteins to carbs or lipids
Which enzyme is required for glycogenolysis
Glycogen phosphorylase
how does exercise affect fat metabolism?
- hormone release of epinephrine, norepinephrine, glucagon
- these hormones augment lipase
