LECTURE 5: lipid metabolism, aerobic metabolism, endurance athletes & games players

Question 1

what attaches to TAG to activate them for storage & metabolism? what do they become?

Answer 1

acetyl CoA, fatty acyl CoA

Question 2

what compounds are fatty acyl CoA broken into during beta oxidation?

Answer 2

groups of 2C acetyl groups attached to CoA

Question 3

what is the purpose of beta oxidation?

Answer 3

breakdown of fatty acid chains of triglycerol to release energy for ATP resynthesis and acetyl CoA for krebs cycle

Question 4

where does beta oxidation occur?

Answer 4

in the mitochondria

Question 5

list four sources of acetyl

Answer 5

fatty acids (one for every 2 carbons), proteins (only little), ketone bodies, carbohydrates

Question 6

what is lipolysis?

Answer 6

hydrolysis of triglycerides, “fat metabolism”

Question 7

what protein transports FFA through blood?

Answer 7

albumin

Question 8

what is lipolysis?

Answer 8

hydrolysis of triglycerides, “fat metabolism”, breakdown of TAG into 3 fatty acids + glycerol

Question 9

which causes an uptick in lipolysis - higher FFA concentration or lower FFA concentration in the blood?

Answer 9

low FFA concentration. lipolysis is favoured when FFA is low

Question 10

list 5 hormones stimulating and 1 hormone inhibiting lipolysis

Answer 10

adrenaline, noradrenaline, glucagon, cortisol, growth hormone stimulate, insulin inhibits

Question 11

will fasted or non fasted athletes have a higher blood FFA concentration during exercise? why?

Answer 11

fasted, non-fasted athletes use blood glucose and ingested FFA, reducing lipolysis rates

Question 12

what are typical blood FFA levels at rest and in exercise?

Answer 12

rest: 0.2-0.4mmol/L, exercise: 2.0mmol/L

Question 13

what part of the mitochondria does the krebs cycle take place?

Answer 13

the matrix (inside both membranes)

Question 14

where does the ETC take place?

Answer 14

intermembrane space (between two membranes)

Question 15

true or false: krebs cycle begins within the first 2seconds of exercise?

Answer 15

true - to make up for the using up of intracellular ATP in 2seconds of exercise

Question 16

list the 5 stages of the krebs cycle

Answer 16

1) acetyl CoA dissociates to form acetyl to enter krebs cycle
2) Acetyl (2C) + Oxaloacetate (4C) = Citrate (6C)
3) citrate is oxidised (e- removal) and loses 2C as CO2
4) step three turns citrate into Oxaloacetate (4C)
5) oxaloacetate binds with a new acetyl to enter another krebs cycle

Question 17

how many ATP are generated in the krebs cycle and what other by products are produced?

Answer 17

2ATP, NADH, FADH2

Question 18

what is the greatest number of ATP that can be generated in the ETC?

Answer 18

38 ATP

Question 19

list the three aims of the krebs cycle

Answer 19

1) decarboxylation of acetyl groups (removing carbons)
2) complete oxidation of acetyl groups & resynthesise ATP
3) production of reduced electron carries/coenzymes (gained electrons)

Question 20

which is the definition of aerobic metabolism: the krebs cycle or the ETC?

Answer 20

ETC

Question 21

what is the main aim of the ETC?

Answer 21

transport of electrons from krebs cycle to ETC to generate ATP

Question 22

how many protein-lipid complexes make up the ETC?

Answer 22

4

Question 23

what is the basic principle of the ETC?

Answer 23

electrons jump from complex to complex, releasing energy each time

Question 24

what is the last recipient of e- in the ETC?

Answer 24

Oxygen

Question 25

what is generated as a byproduct of aerobic metabolism?

Answer 25

water (H2O)

Question 26

how long must an event last for for it to be classed as endurance?

Answer 26

8min-10h

Question 27

do endurance athletes have more efficient glycolysis of lipolysis systems?

Answer 27

lipolysis

Question 28

true or false - endurance athletes could theoretically exercise forever given unlimited O2 & FFA?

Answer 28

true

Question 29

in what time frame are glycogen stores used up in endurance events?

Answer 29

1-1.5h

Question 30

which fibre type changes to benefit endurance events in trained athletes?

Answer 30

type II fibres - they take on characteristics like type I fibres to facilitate more aerobic metabolism

Question 31

do endurance athletes use all CHO, FFA or a combination of both as fuel?

Answer 31

combination

Question 32

can training enhance aerobic energy pathways such as the krebs cycle and ETC?

Answer 32

yes

Question 33

list two physiological changes in endurance training that increase aerobic capacity

Answer 33

increased mitochondrial density, increased capillary density

Question 34

list 3 points related to easy-moderate endurance exercise

Answer 34

- relies mostly on FFA, little on CHO, - high FFA uptake in skeletal muscle at beginning, followed by a catch up in lipolysis rates - FFA concentration increases over duration of exercise

Question 35

list two reason FFA release to bloodstream is reduced in moderate-high endurance exercise

Answer 35

1. accumulation of H+ inhibits lipolysis 2. blood flow to adipose tissue reduces (redirected to skeletal muscle)

Question 36

list two causes of fatigue in endurance athletes

Answer 36

1. ATP synthesis reduces in skeletal muscles 2. hepatic glycogen stores deplete

Question 37

list two limitations of aerobic metabolism, especially as endurance exercise duration increases

Answer 37

1. supply of O2 to blood from lungs and ability of heart to pump O2 rich blood to circulation 2. O2 extraction ability of skeletal muscle exceeding the O2 supply

Question 38

does amount of energy demand met by aerobic metabolism increase or decrease with exercise duration?

Answer 38

increase

Question 39

what energy source is most important for games players?

Answer 39

muscle glycogen

Question 40

does aerobic contribution to energy increase or decrease with cumulative sprints?

Answer 40

increase

Question 41

how many minutes of recovery are required to restore pre-10s sprint levels of PCr?

Answer 41

5mins

Question 42

list four reasons the increase in BLa levels slow throughout a game?

Answer 42

- Insufficient recovery means Pi, H+ & La aren't cleared and glycolysis is inhibited - accumulation of other inhibitors of glycolysis (eg ADP, NH4+) occurs in high intensity exercise - reduced neural drive - higher oxidative metabolism

Question 43

what is a good target for pre-game glycogen stores to prevent early fatigue?

Answer 43

45mmol/khww

Question 44

list two reasons for temporary fatigue in games

Answer 44

1. muscle ion homeostasis disrupted 2. impaired excitation of sarcolemma

Question 45

do type I or II fibres have larger net glycogen storage capacity?

Answer 45

type II