Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

HSE303 > Module 2 - Anaerobic Metabolism > Flashcards

Module 2 - Anaerobic Metabolism Flashcards

Weeks 2 and 3 for Team Based Learning class #2

1
Q

Oxidative Phosphorylation (i.e. aerobic metabolism)

A

Provides majority of ATP during most exercise situations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

2 major limitations of aerobic system

A

1) Cannot immediately provide ATP at onset of exercise or when there is an increase in exercise intensity

2) Maximal rate of ATP produced by aerobic system is inadequate to provide ATP during very intense exercise

  • In such cases, anaerobic metabolism fills the ‘gaps’ in ATP provision to sustain the desired exercise intensity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Onset of exercise - Sprint athlete

A

Aerobic system never plays a significant role in ATP provision because

  • Race is too short (10 seconds) for aerobic metabolism to ‘fully get going’

Anaerobic ATP provision is rapid and sufficient to supply required ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Onset of exercise - Endurance athlete (1500m runner)

A
  • Race starts at light intensity, so aerobic system will be able to supply ATP required
  • But initially, anaerobic metabolism must provide ATP to compensate for ‘oxygen deficit’ that occurs at the onset of exercise
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Oxygen deficit

A

Reflects delay in physiological processes (e.g. increases in HR, stroke volume, respiratory rate) that are necessary to increase oxygen delivery to contracting muscles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

True or false: In both example (sprint & endurance athlete) aerobic metabolism cannot provide required ATP at the onset of exercise?

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Increases in exercise intensity - endurance athlete

A
  • Initially maintains steady pace (steady-state)
  • With 600m to go they accelerate
  • With 400m to go the speed increases again
  • These accelerations demand an immediate increase in ATP that cannot be supplied aerobically and thus require anaerobic metabolism
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Increases in exercise intensity - endurance athlete: If increases in exercise intensity are not too intense and are maintained for a sufficient period of time…

A
  • Oxygen uptake may increase so ATP demands can be met aerobically
  • However, in this example, rapid succession of accelerations (which don’t allow for O2 uptake to ‘catch-up’ to meet ATP demand), along with the liklihood that the very high intensity requires more ATP than the maximal rate of aerobic ATP production
  • Suggests that these accelerations towards the end of the race are fuelled by anaerobic metabolism
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Anaerobic provision of ATP is provided by 2 main pathways:

A
  1. ATP-PCr system
  2. Anaerobic glycolysis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

ATP stored in resting skeletal muscle

A
  • Small amount - 20-25 mmol.kg-1 dry mass used for energy contraction
  • During maximal sprint, muscle energy demand is high (ATP usage: 10-15mmol.kg-2 dry mass.sec-1)
  • Stored ATP depletes within 2-3 seconds assuming no other system is available to produce ATP
  • Complete depletion of ATP stores does not occur
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

ATP-PCr system

A
  • Skeletal muscle contains an energy rich molecule called phosphocreatine (PCr) which can regenerate ATP rapidly (40x and 10x faster than oxidative phosphorylation and glycolysis, respectively) when catalysed by an enzyme called Creatine Kinase (CK)
  • CK activity is very high in skeletal muscle
  • PCr content in resting muscle is 75-90mmol.kg-1 dry mass - 3x the stores of ATP
  • The PCr system can supply ATP rapidly, but only for a short time, as PCr stores are limited
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Anaerobic glycolysis

A
  • Regenerates muscle ATP through the breakdown of carbohydrate and the resultant production of lactic acid
  • Mostly achieved by the breakdown of glycogen stored in the muscle (glycogenolysis)
  • Also achieved by the breakdown of glucose, which is transported to muscle through the bloodstream
  • ATP capacity supplied in skeletal muscle during intense exercise is ~300 mmol.kg-1 dm - 4x greater than the ATP-PCr system
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Anaerobic glycolysis: accumulation of H+

A
  • Drop in pH (i.e. acidosis)
  • Occurs in muscle
  • Associated with fatigue (slows rate of muscle relaxation)
  • Limit the rate of anaerobic glycolysis and ATP supply by inhibiting glycogen phosphorylase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

The role of adenylate kinase in generating ATP

A
  • A small amount of ATP can be regenerated from ADP in a reaction catalysed by the enzyme adenylate kinase (aka myokinase)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Interplay of energy systems during a 400m race

A
  • Shift FROM predominantly anaerobic sources of ATP in the initial stages of maximal exercise TO aerobically sourced ATP with increasing exercise duration
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

The changing contribution of energy systems: repeated sprints (3 x 30s cycling sprints, 4 mins recovery between)

A

Sprint 1:
0-6s = mostly PCr and glycolysis
6-15s = mostly glycolysis
15-30s = mostly oxidative phosphorylation

Sprint 3:
0-6s = mostly PCr, decreased glycolysis
6-15s = mostly oxidative phosphorylation, decreased PCr and glycolysis
15-30s = mostly oxidative phosphorylation, decreased PCr and glycolysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

The changing contribution of energy systems: repeated sprints (10 x 6s cycling sprints, 30s recovery between)

A

Sprint 1:
ATP = 6.3%
Glycolysis = 44.1%
PCr = 49.6%

Sprint 10:
ATP = 3.8%
Glycolysis = 16.1%
PCr = 80.1%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

With repeated high intensity exercise bouts, the major change in anaerobic energy supply is a marked inhibition of…

A

Glycolysis

  • Probably causes by increased acidosis (H+ concentration) inhibiting the activity of glycogen phosphorylase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Apart from the number of exercise bouts in a sequence (i.e. repeated bouts) what are the other factors that influence anaerobic energy system contribution? Clue: O-F-T-M

A
  1. Oxygen availability
  2. Fuel availability
  3. Training status
  4. Muscle fibre type
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Metabolic differences in Type 1 and 2 muscle fibre

A
  • Type 2 can store greater amounts of anaerobic fuels - PCr and glycogen
  • These fuels are used to rapidly generate ATP in type 2 fibres during intense exercise
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

ATP content in type 1 and 2 fibres before and after a 30s maximal sprint

A

Pre-exercise:
Type 1 = 24.0
Type 2 = 24.0

Post-exercise:
Type 1 = 20.6 (3.4 loss)
Type 2 = 19.0 (5.0 loss)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

PCr content in type 1 and 2 fibres before and after a 30s maximal sprint

A

Pre-exercise:
1 = 71.3
2 = 79.3

Post-exercise:
1 = 12.2 (59.1 loss)
2 = 5.0 (74.3 loss)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Glycogen content in type 1 and 2 fibres before and after a 30s maximal sprint

A

Pre-exercise:
1 = 375
2 = 472

Post-exercise:
1 = 298 (77 loss)
2 = 346 (126 loss)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What are Nucleotides

A

Compounds that contain a nitrogen base, a sugar group and at least one phosphate group in their structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What are purine (adenine) nucleotides?

A

Molecules that contain adenine as the nitrogenous base, ribose as the sugar group, and one or more phosphate groups

  • Adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP) are all purine nucleotides as they consist of adenine, ribose and at least one phosphate group.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

ATP hydrolysis

A
  • Water-mediated breakdown of these bonds
  • ADP and inorganic phosphate are products
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

During very intense exercise, there is a rapid breakdown of muscle ATP that exceeds the rate at which ATP can be resynthesised

A

As a consequence,
- Muscle ATP levels fall
- Free ADP and Pi concentrations rise
- If too much ADP and Pi accumulates in the muscle, fatigue occurs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Fatigue as an important muscle cell protective mechanism

A
  • Reducing contractile activity will slow the demand for ATP, allowing production rates to ‘catch up’
  • Prevents muscle cell ATP levels from falling too low
  • Accumulation of free ADP in the muscle cell causes a slowing of muscle shortening velocity and rate of relaxation
  • Increase in muscle Pi causes a reduction in muscle force and slows rate of muscle relaxation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

The enzyme adenylate kinase

A
  • Helps to slow the rise in free ADP levels and delay fatigue for a short period of time
  • Helps decrease free ADP accumulation
  • Phosphate group from 1x ADP molecule is donated to another, to produce 1x ATP molecule (used for energy) and 1x AMP (adenosine monophosphate) molecule
  • Too much AMP tends to drive the adenylate kinase reaction in the direction of making ADP, therefore causing fatigue
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is Inosine Monophosphate (IMP)?

A

Intracellular precursor (thing that comes before) of adenosine monophosphate, and plays a central role in intracellular purine metabolism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Why does muscle produce IMP during intense exercise?

A
  • As the reaction needed to convert ADP molecules to ATP and AMP is an ‘equilibrium reaction’ (can go in either direction depending on concentrations of inputs and products)
  • Accumulation of AMP prevents reaction moving to the right (i.e. producing ATP)
  • Therefore there is a process that allows AMP concentration to be reduced to promote continued ATP production and reduce fatiguing effects of accumulated free ADP
32
Q

AMP + H20 -> NH3 + IMP

The resulting IMP molecule either…

A
  1. Goes through a series of reactions that eventually produces uric acid
  2. Converted back into AMP via the reamination reactions of the purine nucleotide cycle (PNC)
33
Q

The resulting IMP molecule converted back into AMP via the reamination reactions of the purine nucleotide cycle (PNC)

A
  • During contractions, AMP itself inhibits the process that produces AMP from IMP (the reamination arm of PNC)
  • Most of deaminated AMP remains stored as IMP until intense contractions are stopped
  • Small proportion of stored IMP is degraded to inosine and hypoxanthine, which can exit the muscle and be converted to uric acid, which is excreted by the kidney
  • In recovery, most of remaining stored IMP is converted back to AMP and eventually to ATP
34
Q

Metabolic benefits of the production of IMP

A
  1. Lowers AMP concentration, thus allowing adenylate kinase to work in the direction of ATP production
  2. To activate phosphofructokinase (PFK) and phosphorylase B
  3. IMP is co-produced with NH3, which may buffer intramuscular acidosis
35
Q

Phosphofructokinase (PFK) and phosphorylase B

A
  • 2 enzymes that play an important role in regulating anaerobic glycolysis and thus ATP production
36
Q

Individuals without AMP deaminase activity

A
  • No increase in IMP
  • No reduction in ATP
    *note: during exercise
  • Impaired sprint performance - this decreased performance is attributed to an elevated free ADP concentration which slows contraction velocity and rates of muscle relaxation
37
Q

Muscle metabolite levels can be expressed in different ways:

A
  1. mmol.kg-1 wet mass
  2. mmol.kg-1 dry mass
38
Q

mmol.kg-1 wet mass

A

Refers to the amount of a molecule (expressed in mmol) per kilogram of muscle with normal water content

39
Q

mmol.kg-1 dry mass

A

Refers to the amount of a molecule (expressed in mmol) per kilogram of muscle with no water content

  • Water is removed from skeletal muscle via freeze drying
40
Q

Typically, skeletal muscle consists of approx. 77% water and approx. 23% dry matter. So if muscle ATP content was 5 mmol.kg-1 wet weight…

A

the equivalent dry mass value would be 5 divided by 0.23

= 21 mmol.kg-1 dry mass (dm)

41
Q

What is creatine kinase?

A

The reaction involved in the ATP-PCr system supplies ATP, which is catalysed by the enzyme Creatine Kinase (CK)

PCr + ADP + H+ ↔ ATP + Cr

42
Q

There are several CK isoforms (enzymes with similar function but slightly different amino acid sequences) that have specific roles and act in specific locations within cells. These can be categorised as…

A
  1. Cytosolic (acting in the cytosol)
  2. Mitochondrial (acting in the mitochondria)
43
Q

There are three types of cytosolic CK

A
  1. CK-BB - found in brain tissue
  2. CK-BM - found in cardiac muscle
  3. CK-MM - found in skeletal muscle
44
Q

There are two types of mitochondrial CK

A
  1. Sarcomeric mitochondria CK - found in cardiac and skeletal muscle
  2. ubiquitous mitochondrial CK - found in brain and smooth muscle cells
45
Q

Skeletal muscle cells contain both cytosolic (CK-MM) and sarcomeric mitochondrial CK (sMtCK)

A
  1. Muscle CK-MM - located near muscle cytosolic ATPase’s (e.g. myosin ATPase, Na+K+ ATPase, Ca2+ ATPase)
  2. Sarcomeric mitochondrial CK (sMt-CK) – located in intermembrane space of mitochondria
46
Q

CK-MM

A

Enzyme catalysing the

PCr + ADP + H+ ↔ ATP + Cr reaction

in the cytosol when anaerobic metabolism is required to maintain cytosolic ATP levels.

  • Known as temportal ATP buffering (maintaining ATP levels over time)
47
Q

During aerobic metabolism, both CK isoforms (CK-MM and sMt-CK) act together in what is termed the ‘creatine phosphate shuttle’

A

Set of intracellular processes that facilitate the transport of energy from the mitochondria to the myofibrils (aka spatial ATP buffering)

48
Q

The creatine found in an adult muscle cell normally comes from one of two possible sources:

A
  1. Endogenous (de novo synthesis) - creatine is produced and released from the liver
  2. Dietary creatine derived from food (e.g. animal products) or supplements

*muscle cells do not synthesise their own creatine, but may do if levels are abnormally low (e.g. creatine metabolism disorder)

49
Q

Regulation of muscle creatine uptake

A
  • Most important determinant of muscle creatine levels, as muscle creatine loss is not regulated
  • Circulating creatine levels are taken up into skeletal muscle cells by the activity of creatine transporter proteins located on the muscle fibre cell membrane
  • Regulation of the creatine transporter activity is enhanced when circulating creatine levels are increased
50
Q

A proportion of the creatine which enters the muscle is converted to PCr via the action of CK-MM

A
  • 2% of cellular total creatine pool (TCr = Cr + PCr) is degraded (no enzyme involved) to creatinine per day and this sets the rate of loss of creatine from the cell
  • Creatine diffuses from the muscle and is excreted into the urine
51
Q

How can sprint performance be improved by increasing levels of PCr in muscle

A
  • The capacity of the ATP-PCr system to rapidly generate is limited by the amount of PCr stored in muscle
  • However, PCr concentrations in muscle are unaffected by training
  • So how can levels of PCr stored be increased in the muscle?
52
Q

Study of total muscle creatine stores in eight adult males both pre-, and post-ingestion of 20g of a creatine supplement per day for 5 consecutive days.

A
  • 20-30% increase in total muscle Cr (TCr = Cr + PCr) in the form of PCr
  • Increases the capacity of muscle cell to rapidly generate ATP during short-term intense exercise
53
Q

Study of improvements in repeat sprint (6 x 60m with 3 min recovery between each sprint) performance observed in sprinters following creatine supplementation

A
  • Placebo supplementation showed little change in sprint times before and after supplementation
  • Sprint times were high prior to Cr supplementation, compared to after supplementation
54
Q

Reasons why creatine supplementation may not improve performance

A
  • Baseline creatine levels are already sufficiently high, inhibiting further loading
  • Supplementation tends to increase body weight (due to increases in intracellular water storage)
55
Q

the process of glycolysis

A

10 reaction step process with occurs in the cytosol

  • The carbohydrate broken down begins as either glycogen (already in the cytosol) or glucose (transported to the cytosol across the sarcolemmal membrane from the bloodstream)
56
Q

Efficiency of glycogen vs glucose, when producing ATP

A
  • The initial breakdown of glucose into glucose-6-phosphate (first step) requires energy - which is not the case when breaking down glycogen (glycogenolysis)
  • Glycogen (i.e. glycogenolysis) is more efficient at producing ATP
57
Q

10 steps of anaerobic glycolysis (enzymes)

A
  1. Hexokinase
  2. Phosphoglucose isomerase
  3. Phosphofructo-kinase-1
  4. Aldolase
  5. Triose phosphate isomerase
  6. Glyceraldehyde 3-phosphate dehydrogenase
  7. Phosphoglycerate kinase
  8. Phosphoglycero-mutase
  9. Enolase
  10. Pyruvate kinase
58
Q

Aerobic vs anaerobic glycolysis

A

Aerobic = when glucose/glycogen is catabolised to pyruvate

Anaerobic = when glucose/glycogen is catabolised to lactate

*Just a way for scientists to distinguish between the end products, glycolysis is never aerobic!

59
Q

When flux through the glycolytic pathway is high and/or when oxygen consumption is limited (both will occur during short term intense exercise)

A

Pyruvate will increase in concentration

  • This build-up in pyruvate causes rapid production of lactate via the action of lactate dehydrogenase
  • Regeneration of NAD+ in this reaction allows this cofactor to be used again in reaction step 6 of glycolysis
60
Q

Glycogenolysis

A
  • Intracellular glycogen supplied most of fuel for anaerobic glycolysis during intense exercise
  • When glycogen is catabolised, only a small amount of glucose is produced
  • Does not require energy (ATP) - more efficient in producing ATP
  • Since glycogen is already stored in muscle (unlike glucose) - a more readily available source of energy
61
Q

the most abundant product of glycogenolysis is…

A

Glucose-1-phosphate

  • Rapidly converted into glucose-6-phosphate (G6P) by the enzyme phosphoglucomutase
  • G6P can then directly enter the glycolytic pathway
62
Q

When ATP demand in a cell increases…

A

ATP producing pathways are turned on more

63
Q

When ATP demand in a cell decreases…

A

ATP producing pathways are turned down or off

64
Q

Why is skeletal muscle regulation of ATP supply challenging?

A

ATP demand of muscle cell can increase to a high amount (>100 fold) very quickly (almost instantly)

e.g. going from rest to maximal contractile activity

65
Q

How is skeletal muscle regulation of ATP accomplished?

A
  • In each metabolic pathway there are key enzymes (regulatory enzymes) that control flux through a given pathway
  • Regulation of these enzymes may involve allosteric regulation:
  1. Transition from an inactive to active form
  2. Transition from an active to inactive form
  3. Removal of a phosphate group
  4. Regulation by hormones (e.g. insulin, adrenaline, glucagon)
66
Q

What is Allosteric regulation?

A

Regulation of an enzyme by binding an effector molecule at a site other than the enzyme’s active site

  • The site that the effector binds to, is termed an ‘allosteric’ or ‘regulatory’ site
67
Q

Allosteric sites of an effector

A
  • Allows effectors to bind to the protein
  • Results in conformational change of the active sites
68
Q

Allosteric activators

A

Effectors that enhance the protein’s activity

69
Q

Allosteric inhibitors

A

Effectors that decrease the protein’s activity

70
Q

Key metabolic regulatory enzymes normally change their activity in response to cellular metabolic signals (effector molecules) that bind to these enzymes indicating that cellular ATP supply is adequate or not

A

Increase in cellular Pi and AMP = ATP production rates are inadequate

Increase in PCr = ATP supply is OK

71
Q

The 3 key regulatory enzymes in the glycolytic pathway

A
  1. Hexokinase
  2. Phosphofructokinase
  3. Pyruvate kinase
72
Q

Regulatory enzyme: Hexokinase

A

Allosterically activated by Pi
Allosterically inhibited by G6P

73
Q

Regulatory enzyme: Phosphofructokinase (PFK)

A
  • Major regulatory and rate limiting glycolytic enzyme

Allosterically activated by F6P, Pi, AMP, F1, 6 bisP and NH4+

Allosterically inhibited by ATP and PCr

74
Q

Regulatory enzyme: Pyruvate kinase

A

Allosterically activated by ADP
Allosterically inhibited by ATP and PCr

75
Q

The regulation of muscle glycogenolysis is complex. It involves…

A
  1. Supply of substrates (glycogen and Pi)
  2. Allosteric regulators (e.g. Ca2+, AMP)
  3. The hormone adrenaline
76
Q

Supply of Pi is a critical regulator of glycogen breakdown

A
  • Pi levels in resting muscle are low, therefore limiting any activity of phosphorylase
  • Pi levels rise at the onset of muscle contraction, due to increase in ATP hydrolysis, therefore providing suffcient substrate for phosphorylase to act
77
Q

Both Pi and cytosolic Ca2+ levels are important regulators of phosphorylase…

A
  • Ensures that fast rates of glycogen breakdown do not occur in resting muscle when there is no need, but can do so when muscles contract!

HSE303 (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions