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HLTH1100 > Bioenergetics > Flashcards

Bioenergetics Flashcards

1
Q

What is metabolism and how is it regulated

A
  • Sum of all chemical reactions that occur in the body, anabolic (synthesis of molecules) and catabolic (breakdown of molecules)
  • Regulated by enzymatic activity
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2
Q

What is bioenergetics

A
  • Converting foodstuffs (fats, proteins, carbohydrates) into energy
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3
Q

Describe cell structure

A
  • Cell Membrane: Phospholipid bilayer (lipid soluble substances), fluid mosaic, semipermeable, regulates passage of materials (secretion / absorption), proteins embedded, interacts with environment
  • Nucleus: Genetic information (DNA - linear chromosomes), controls shape and activity through protein synthesis, exports genetic information as RNA via the nucleolus / nuclear pores
  • Cytoplasm: Gelatinous helix that surrounds the nucleus, membrane bound organelles suspended, chemical reactions, cytosol (semi-fluid matrix)
  • Mitochondria: Double walled (inner wall = membranous cristae) partition matrix in-between (DNA / ribosomes), divides independently, site of cellular respiration / metabolism, semi-autonomous
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4
Q

What is energy storage and ATP

A
  • Storage: Energy is stored in chemical bonds within molecules and released when these bonds are broken
  • ATP: Adenosine triphosphate, energy currency of cell, energy rich phosphate bonds, made up of three elements (adenine, ribose and phosphate)
  • Adenosine diphosphate + inorganic phosphate forms adenosine triphosphate
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5
Q

What are enzymes and two types

A
  • Complex protein structures, catalysts that regulate speed of reactions by lowering the activation energy (Ea), formation of an enzyme substrate complex, remains unchanged (not consumed)
  • Kinases: Add phosphate groups to the substrates (creatine kinase, ATPase)
  • Dehydrogenases: Remove hydrogen from their substrate (lactate dehydrogenase)
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6
Q

What are factors that affect enzyme activity

A
  • Temperature: Small rise in body temperature increases enzyme activity, exercise results in increased body temperature, large increases in temp can result in decreased activity (exercise)
  • pH: Change in pH reduces enzyme activity, each enzyme has an optimal pH range, acid during exercise
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7
Q

What are rate limiting enzymes / modulators of them

A
  • Control of bioenergetics, regulate rate of pathways
  • Increase ‘opportunity’ for reaction to progress (increase number of enzymes)
  • Switch off enzymes when not required
  • Modulators: Levels of ATP and ADP + Pi , high levels of ATP inhibit ATP production, low levels of ATP and high levels of ADP+Pi stimulate ATP production
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8
Q

What is an energy system

A
  • Function to restore ATP (or similar high energy phosphates), energy for can be provided by ATP-PC, glycolysis, oxidative phosphorylation / ETC, beta oxidation / ETC
  • No one energy system provides all of the energy for ATP regeneration
  • Involves varying contributions for each system
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9
Q

What is ATP hydrolysis and repletion

A
  • Breakdown (catabolic), ATP → ADP + Pi + free energy for biological work, enzyme ATPase breaks the chemical bond of ATP
  • Repletion: Occurs very rapidly via ATP-PC (phosphocreatine), lactic acid system and aerobic system, enough for ~ 1sec maximal contraction contained within the cell
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10
Q

What is the phosphocreatine system

A
  • PC, PCr, CP, CrP
  • Energy rich phosphate bond, most readily available fuel source for muscle contraction (stored within muscle fibre
  • ~5-10 seconds worth of muscle contraction
  • ATP hydrolysis catalysed by creatine kinase during exercise
  • ATP-PC system, immediate source of ATP, PC + ADP + creatine kinase → ATP + C
  • Rapid due to short uncomplicated reaction, doesn’t require O2, easily accessible
  • Used in throwing, jumping, sprinting, power lifting, events lasting < 10s
  • Regulated by creatine kinase (CK), activated by increase ADP (instantly triggers breakdown of CP to replenish ATP), inhibited by increased ATP
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11
Q

What is glucose vs glycogen and transferals between

A
  • Glucose: C6H12O6, glycogen is a more compact storage form of glucose, blood glucose interacts with muscle glycogen during glycolysis to form pyruvate / lactate
  • Glycogenesis: Formation of glycogen from glucose
  • Gluconeogenesis: Formation of glycogen from substrates other than glucose
  • Glycogenolysis: Breakdown of glycogen to glucose, occurs one glucose at a time
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12
Q

What is glycolysis and what does it produce

A
  • Anaerobic pathway, breakdown of glucose or glycogen to form pyruvate, occurs within the sarcoplasm (outside the mitochondria)
  • Ubiquitous, substrate level phosphorylation
  • Releases a small amount of energy stored in glucose, much energy still locked up in pyruvate (C-H)
  • Preparatory / payoff phase
  • Glucose + 2 NAD+ + 2 ADP + 2 Pi → 2 Pyruvate + 2 NADH + 2 H+ + 2 ATP
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13
Q

What are the steps of glycolysis

A

Preparatory Phase:
- Energy investment, phosphorylation of glucose (6C)
- Glucose-6-phosphate (via hexokinase, use ATP)
- Fructose-6-phosphate
- Fructose-1,6-biphosphate (via phosphofructokinase, use ATP)
- Glyceraldehyde-3-phosphate (3C)
- Used: 2 ATP molecules, 1 glucose and 2 NAD+
Payoff Phase:
- Energy production, glyceraldehyde-3-phosphate (3C) converted to pyruvate (3C)
- Products: 2 NADH (re-oxidised to NAD+), 4 ATP (2 ATP net) and 2 pyruvate

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14
Q

What are electron carrier molecules

A
  • Energy Carriers: Transport H and associated E, to mitochondria for ATP generation (aerobic) or to convert pyruvic acid to lactic acid (anaerobic)
  • NAD: Nicotinamide adenine dinucleotide, NAD+ + H → NADH, NADH produced in glycolysis must be converted back to NAD+
  • Shuttling H+ into the mitochondria via specific transport system in mitochondrial membrane
  • FAD: Flavin adenine dinucleotide, FAD + 2H → FADH2
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15
Q

Define aerobic vs anaerobic

A
  • Anaerobic: Formation of ATP without the use of O2 (ATP-PC and glycolysis), cytoplasm, shorter energy production
  • Aerobic: Production of ATP using O2 as the final electron acceptor (TCA, ETC), oxidative, mitochondria, longer energy production (60sec)
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16
Q

What is our immediate source of energy

A
  • The immediate source of energy for muscular contraction is the high-energy phosphate ATP. ATP is degraded via the enzyme ATPase as follows: ATP + ATPase → ADP + Pi + energy
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17
Q

How do muscle cells produce ATP

A
  • Produce ATP by any one or a combination of three metabolic pathways
  • (1) ATP-PC system
  • (2) glycolysis
  • (3) oxidative formation of ATP
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18
Q

Describe glycolysis activity at rest vs sprinting

A
  • Rest: Not very active at rest, only way RBC can produce energy is through glycolytic pathway
  • Sprint Activity: During sprint activity glycolysis must occur several hundred times faster than at rest
19
Q

How is glycolysis regulated (4 RLE)

A

Glycogen Phosphorylase:
- Facilitates conversion of glycogen to glucose
- Activated by high ADP, Ca, epinephrine and inhibited by high ATP and FA
Hexokinase:
- Facilitates conversion of blood glucose to glucose-6-phosphate, high affinity for glucose, inhibited by high FA and its product (glucose-6-phosphate)
- ATP required
- Prefer to use glycogen to produce glucose-6-phosphate (inhibits HK and ‘spares’ blood glucose / ATP)
Phosphofructokinase (PFK):
- Facilitates conversion of fructose-6-phosphate to fructose 1,6 biphosphate
- Key rate limiting step
- Activated by high fructose-6-phosphate and ADP and low creatine phosphate
- Inhibited by high H, citrate (krebs cycle), ATP and FA
Pyruvate Kinase:
- Final glycolytic step, activated by high fructose-6-phosphate, inhibited by ATP, conversion of glyceraldehyde-3-phosphate into pyruvate

20
Q

What is the function and steps of the lactate system and when is it utilised

A
  • Supplements ATP-PC system when O2 supply rate is inadequate for the energy demand, valuable fuel source
  • Produced in quantities equivalent to the amount of H+
  • Re-oxidise NADH, consume H (increase pH) and permit continued ATP production from glycolysis
  • Pyruvate → lactate (transported in blood) → liver → pyruvate → glucose / glycogen, reuse lactate and recovery of glucose
  • Primarily recruited for max efforts lasting 20-50s
21
Q

How is lactate removed following exercise

A
  • 10% sweat and urine, 20% gluconeogenesis in the liver and 70% re-oxidised to pyruvate then enters the TCA cycle
  • Often occurs in non working muscles and heart
  • Moderate Exercise: 30-50% of VO2 max, improves recovery by maintaining high BF and oxidative functioning of working musculature
  • Intense Exercise: >AT, >70% of VO2 max) may result in further lactate production, not suitable recovery
22
Q

What is TCA cycle and facilitation of energy carriers

A
  • Complete oxidation of CHO, fats and sometimes proteins for energy, produces 2 ATP, 6 NADH, 2 FADH2, 9 steps
  • Oxidation: The removal of H+ from a compound or the addition of O to it
  • Reduction: Addition of H+ or removal of O
  • Energy Carriers: NAD+ and NADH facilitate redox reactions without being consumed, they are recycled, allows many different donors and acceptors to interact, coenzyme acts as intermediary
23
Q

What is the priming step of TCA cycle

A
  • Priming and oxidation of pyruvate (3 C) to create acetate (2 C), binds with coenzyme A to produce acetyl CoA, CO2 and 2 NADH
24
Q

What is the process of TCA cycle

A
  • Acetyl CoA (2 C) combines with oxaloacetic acid (4 C) to produce citrate / citric acid (6 C)
  • Subsequent decomposition / oxidation / breaking down of citrate, produces 2 CO2, 2NADH (1-4)
  • Production / regeneration of oxaloacetic acid, rearranging, produces 1FADH2 and 1NADH (5-9)
  • Transfers high energy e- to carriers, harvested e- directed to ETC to drive ATP synthesis
25
Q

What is the ETC

A
  • Oxidative phosphorylation of NADH and FADH2 to ATP produced in glycolysis and citric acid cycle via a series of carriers (cytochromes)
  • Produces 25 ATP (from 10 NADH), 3 ATP (from 2 FADH2)
    H+ and electrons are accepted by O2 to form metabolic water
  • Multi protein complexes and mobile carriers in the inner mitochondrial membrane / cell membrane of bacteria
  • Each compound in the sequence has a higher affinity for electrons
26
Q

What are the steps involved in ETC

A
  • Stimulates one directional pumping of H across the inner mitochondrial membrane, establishes a proton gradient, excess H+ makes one side of membrane positively charged
  • As H+ is transported back across the membrane, energy is released to form ATP (chemiosmosis) and used by ATP synthase to generate ATP
27
Q

What is chemiosmotic energy coupling

A
  • Proton gradient for ATP synthesis established across a membrane
  • Must contain proteins that couple the “downhill” flow of electrons in the electron transfer chain with the “uphill” flow of protons across the membrane
  • Membrane must contain a protein that couples “downhill” flow of protons to the phosphorylation of ADP
28
Q

Provide a summary of products and RLE in glycolysis, pre-TCA, TCA and ETC

A
  • Glycolysis: 2x pyruvate, 2x ATP and 2x NADH, phosphofructokinase
  • Pre-TCA Cycle: 2x NADH
  • TCA Cycle: 2x ATP, 6x NADH and 2x FADH2, isocitrate dehydrogenase
  • ETC: 25 ATP (10 NADH), 3 ATP (2 FADH2) / metabolic water, overall 32 ATP, cytochrome oxidase
29
Q

What is fat metabolism and its efficiency

A
  • ATP Production: Varies with the length of the Fatty Acid (FA) chain, steric acid 18 carbon chain = 147x ATP and palmitic acid 16 carbon chain 130x ATP
  • β Oxidation: FA broken down to acetyl CoA 2 C at a time, 1 ATP used, 1x FADH2 and 1x NADH generated, then enters into TCA cycle
  • Efficiency: Less efficient than glucose, 15% more O2 required for FA oxidation
30
Q

How is fat metabolism regulated

A
  • FA utilised for energy by muscle come from triglyceride stored in muscle, body fat and circulating in blood stream
  • Lipase’s split FA from glycerol portion of TG
  • Activated by hormones, high Ep, NorEp, cortisol and glucagon and low insulin
  • Increase in SNS activity, increased release of FA and TG stores
  • Insulin decreases during prolonged exercise, exercise lasting >1hr blood FA conc may increase by 5x
31
Q

How is metabolic water produced in ETC

A
  • The end result of the electron transport chain is the formation of ATP and water
  • Water is formed by oxygen-accepting electrons; hence, the reason we breathe oxygen is to use it as the final acceptor of electrons in aerobic metabolism
32
Q

How do aerobic and anaerobic metabolisms interact

A
  • Energy to perform exercise comes from an interaction of anaerobic and aerobic pathways
  • Shorter the activity (high intensity), the greater the contribution of anaerobic energy production
  • Long-term activities (low to moderate intensity) utilise ATP produced from aerobic systems
33
Q

What are ways of measuring aerobic capacity and the limitations

A

VO2max:
- Maximal rate at which cells can utilise oxygen
- Higher VO2max increases aerobic capacity
Steady State:
- Stable VO2, HR and Ve
- Takes at least 2-3 mins for O2 consumption to stabilise
- HR is stable within 4 bpm
- VO2max is stable oxygen consumption
Blood Lactate:
- Marker of glycolytic energy production, allows glycolysis to continue
- Accumulates due to hypoxia, high NADH, recruitment of fast twitch muscle fibres
Limitations:
- Performance is limited by O delivery and utilisation
- Fick: VO2 = (SV)(HR)(a-vO2)

34
Q

What is critical power

A
  • Indicator of training intensity
  • The maximal power output that can be maintained for an extended period of time without fatigue
  • Predict maximal work rate
  • Corresponds to highest metabolic power output
  • Could theoretically be maintained indefinitely
  • Unlimited in capacity, limited in rate
35
Q

What is W’

A
  • Total amount of work that can be achieved above CP
  • Changes with oxygen availability
  • Decreases in hyperoxic environments and at high altitude
36
Q

Why is carbohydrate metabolism a primary fuel source during exercise

A
  • Primary fuel source for short duration, incremental or high intensity exercise, major substrate used at the onset of low to moderate intensity exercise
  • During prolonged work (>30 min) there is a gradual shift from carbohydrate metabolism towards an increasing reliance on fat as a fuel substrates
37
Q

How is carbohydrate metabolism regulated

A
  • Availability of NAD+, O2 availability, H+ concentration (inhibits PFK) and increased ADP and Pi stimulate glycolysis
  • Epinephrine is released during periods of high stress or heavy exercise, stimulates glycolysis and promotes carbohydrate metabolism
38
Q

What is blood glucose homeostasis

A
  • Plasma glucose maintained through four processes
  • Mobilisation of glucose from liver glycogen
  • Mobilisation of FFA from adipose tissue (spares blood glucose)
  • Gluconeogenesis from AA, lactic acid, and glycerol
  • Blocking the entry of glucose into cells (forces use of FFA as a fuel)
  • During exercise it is controlled by hormones, fast-acting (insulin, glucagon epinephrine, norepinephrine) and slow-acting (cortisol, growth hormone)
39
Q

What is insulin vs glucagon

A
  • Insulin: Increases cellular uptake of glucose, declines during exercise of increasing intensity and duration, a decrease will increase amount of glucose in the blood
  • Glucagon: Increases blood glucose, increased mobilisation of liver glycogen, increased liver glucose output and increased sensitivity of the liver to epinephrine
40
Q

How does fat metabolism contribute to fuel supply and how is it regulated

A
  • First fat (triglyceride) must be broken down via lipase into FFA, then metabolised via b-oxidation into 2 C chains and oxidised in TCA cycle
  • Epinephrine, norepinephrine, glucagon increase lipase activity promote lipolysis
  • Insulin: Inhibits lipase activity, decline in insulin during longer duration exercise results in increased FFA and glycogen sparing
  • Lactate: High levels promote recombination of FFA and glycerol to form fats thereby decreasing the available FFA as fuel
  • Lipolysis is a slow process, occurs only after several minutes of exercise
41
Q

How does protein metabolism contribute to fuel supply

A
  • Proteases may become active in prolonged exercise

- Skeletal muscle can directly metabolise some AA with help of proteases

42
Q

What occurs when one goes above CP

A
  • Steady state is unable to be attained
  • [PCr] decreases (increase glycolytic / TCA)
  • VO2 max increases (increase SV, Q, a-vO2)
  • Muscle pH decreases (buffer)
  • Increased anaerobic contribution to energy production
  • Increase HR / ventilation
43
Q

How is plasma glucose maintained during exercise

A
  • Increasing liver glycogen mobilisation
  • Using more plasma FFA, increasing gluconeogenesis, and decreasing glucose uptake by tissues
  • The decrease in plasma insulin and increase in plasma glucagon, E, NE, GH, and cortisol
44
Q

Why does plasma FFA concentration decrease during exercise

A
  • The plasma FFA concentration decreases during heavy exercise even though the adipose cell is stimulated by a variety of hormones to increase triglyceride breakdown to FFA and glycerol. This may be due to:
    (a) the higher H+ concentration, which may inhibit hormone sensitive lipase
    (b) the high levels of lactate during heavy exercise promoting the re-synthesis of triglycerides
    (c) an inadequate blood flow to adipose tissue

HLTH1100 (7 decks)

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