Anaerobic Energy Provision (S2)

Question 1

How is energy provided for cells? List multiple ways

Answer 1

1. Primarily via ATP (to ADP + Pi) = -30.5 kJ/mol
2. ADP -> AMP + Pi = -30.5 kJ/mol
3. ATP -> AMP + PPi = -40.6 kJ/mol
4. PPi -> 2 Pi = -31.8 kJ/mol

Question 2

What is ATP made of?

Answer 2

Ribose (sugar), adenine, and high-energy phosphate groups

Question 3

Why are the phosphate groups in ATP important?

Answer 3

They are bound by high-energy bonds that release energy when broken

Question 4

What enzyme breaks down ATP and what are the products?

Answer 4

ATPase breaks ATP into ADP and inorganic phosphate (Pi)

Question 5

Why is ATP considered the universal energy currency?

Answer 5

All cells accept it and it is essential for processes like muscle contraction

Question 6

What happens if ATP is not available in muscle contraction?

Answer 6

Myosin heads stay bound to actin and cannot detach (only ATP can do this job)

Question 7

What role does ATP hydrolysis play in muscle contraction?

Answer 7

It detaches the myosin head from actin = allows contraction of muscle

• it can then reset for another cycle

Question 8

How long does stored ATP last during maximum contraction?

Answer 8

About 2 seconds

Question 9

What happens if the body can’t resynthesise ATP?

Answer 9

Muscles stay contracted - often why we see rigor mortis (stiffening of joints + body) in deceased due to myosin staying bound to actin

• cramp can occur on the minor scale

Question 10

What are the 3 main ATP synthesis systems?

Answer 10

1. ATP-PCr system (anaerobic)
2. Glycolytic system (anaerobic)
3. Oxidative system (aerobic)

Question 11

What are common markers used to assess the glycolytic and oxidative systems?

Answer 11

Lactate for glycolytic and oxygen uptake for oxidative

Question 12

What does the ATP-PCr system use to regenerate ATP?

Answer 12

Phosphocreatine (PCr) and the enzyme creatine kinase

Question 12

What is the ATP yield from the ATP-PCr system?

Answer 12

1 mol ATP per mol PCr

Question 13

How long can the ATP-PCr system sustain maximal effort?

Answer 13

3 to 15 seconds

Question 14

Can PCr be used directly for cellular work?

Answer 14

No, but it can be used to regenerate ATP

Question 15

What happens to PCr levels as exercise intensity increases?

Answer 15

They drop rapidly to help keep ATP levels stable

Question 16

Why does muscle ATP concentration remain relatively constant during early high-intensity exercise?

Answer 16

Because PCr is broken down to rapidly regenerate ATP

Question 17

Why don’t animals like cheetahs have high creatine stores despite being fastest sprinters?

Answer 17

PC is osmotically active and draws water into cells, increasing body weight

Question 18

What are potential effects of creatine supplementation in humans?

Answer 18

Increased cell water content + possible weight gain

Question 19

What is the myokinase (adenylate kinase) reaction?

Answer 19

Another pathway to generate ATP quickly (good for sprinting etc)

• ADP + ADP → ATP + AMP

Question 20

When is the myokinase reaction most active?

Answer 20

During high-intensity exercise when pH drops

Question 21

What does AMP do during intense exercise?

Answer 21

Activates enzymes involved in glycogen breakdown = energy production

Question 22

What is the substrate for anaerobic glycolysis?

Answer 22

Glucose or glycogen

Question 23

What are the end products of anaerobic glycolysis?

Answer 23

Pyruvate, which is then converted to lactate

Question 24

How long can anaerobic glycolysis supply energy for?

Answer 24

15 seconds to 2 minutes

Question 25

What is the net ATP yield from glucose and glycogen in anaerobic glycolysis?

Answer 25

Glucose - 2 ATP per glucose molecule Glycogen - 3 ATP per glycogen molecule

Question 26

Why is ATP yield higher from glycogen than glucose?

Answer 26

Glycogen is already partially phosphorylated so it requires less ATP investment

Question 27

What is the ATP yield per lactate molecule if all pyruvate is converted?

Answer 27

1 to 1.5 ATP per lactate

Question 28

What is the rate-limiting enzyme of glycolysis + why is it rate-limiting?

Answer 28

Phosphofructokinase (PFK) - without it we wouldn't get to pyruvate and therefore lactate either

Question 29

What does citrate synthase do in the Krebs cycle?

Answer 29

Catalyses the condensation of Acetyl-CoA with oxaloacetate to form citrate

Question 30

What does succinate dehydrogenase do in the Krebs cycle?

Answer 30

Converts succinate to fumarate

Question 31

Are citrate synthase or succinate dehydrogenase rate-limiting?

Answer 31

No

Question 32

What is the ATP yield from the electron transport chain after the Krebs cycle?

Answer 32

About 28 ATP

Question 33

What type of activity uses the aerobic energy system most?

Answer 33

Endurance events

Question 34

What enzyme controls the ATP-PCr system and how?

Answer 34

Creatine kinase (CK) via negative feedback

Question 35

How is CK activity regulated?

Answer 35

Increases when ATP falls and ADP rises, decreases when ATP rises

Question 36

How is PFK activity regulated?

Answer 36

Increases when ATP falls and ADP rises, decreases when ATP is high

Question 37

What else regulates PFK activity besides ATP levels?

Answer 37

Products of the Krebs cycle - NADH, FADH2, CO2

Question 38

Which energy system enzymes are higher in aerobically trained individuals?

Answer 38

Succinate dehydrogenase, malate dehydrogenase, carnitine palmityl transferase

Question 39

Which energy system enzymes are lower in aerobically trained individuals?

Answer 39

Glycolytic enzymes like phosphorylase, phosphofructokinase, and lactate dehydrogenase

Question 40

Which enzymes are more highly expressed in anaerobically trained individuals?

Answer 40

Creatine kinase and myokinase (ATP-PCr system

Question 41

What general rule links enzyme activity to training type?

Answer 41

The more you train a pathway, the more you develop that pathway's enzymes

Question 42

Is this rule the same between muscle fibres and enzyme activity?

Answer 42

Yes - aerobic enzymes will be typically expressed in Type I (aerobic - slow twitch) fibres and vice versa

Question 43

What is the Wingate test protocol?

Answer 43

30 seconds all-out sprint on a cycle ergometer applying the correct load (7.5% body mass as resistance)

Question 44

What two key values are measured in the Wingate test?

Answer 44

Peak power and fatigue index

Question 45

When is peak power typically reached in a Wingate test + then what happens?

Answer 45

Around 5 seconds - then begin to fatigue as PCr stores decrease

Question 46

What does a high fatigue index indicate?

Answer 46

Poor anaerobic endurance or very high peak power causing large drop-off

Question 47

Which fibres show the most ATP drop in the first 10 seconds?

Answer 47

Type IIa and IIx

Question 48

What happens to Type I fibres later in the Wingate test?

Answer 48

ATP levels begin to drop so they contribute more

Question 49

What happens to Type II fibres by the second half of the test?

Answer 49

They are exhausted and no longer contribute meaningfully to power

Question 50

When does PCr contribute most in the Wingate test?

Answer 50

Dominates until peak power is reached (~5s), then declines to ~10s

Question 51

When is the glycolytic system most active?

Answer 51

After ~12.5 seconds

Question 52

When does aerobic contribution become significant?

Answer 52

From around 22.5 to 27.5 seconds

Question 53

Why does PCr-ATP and glycolysis dominate early in the Wingate test?

Answer 53

1. They produce ATP very quickly – many molecules per unit time 2. Metabolic Inertia - aerobic metabolism slower to start as need time for oxygen to reach muscle

Question 54

Why do marathon runners perform worse on the Wingate test?

Answer 54

They have lower peak power compared to sprinters

Question 55

How to calculate energy expenditure for aerobic / anaerobic exercise?

Answer 55

Aerobic - using Douglas Bag collection techniques Anaerobic - ATP turnover via muscle biopsy (to measure levels of ATP, PCr, lactate + pryuvate)

Question 56

What is the calculation for ATP turnover (anaerobic energy contribution)?

Answer 56

-2(ΔATP) - 1ΔPCr + 1.5Δlactate + 1.5Δpyruvate (in mmol ATP.kg.s)