Acute metabolic responses Flashcards
Block 1 ExMet MW
Where is energy stored in ATP?
Phosphoanhydride linkages
How much ATP is stored in muscle?
5.6 mmol/kg
How much ATP is used whilst sprinting per second? Approx. how long does it last for?
3.7 mmol/kg/s
< 2 seconds
How much ATP is used in sub-maximal exercise per second? Approx. how long does it last?
0.4 mmol/kg/s
< 15 seconds
Name the two types of phosphorylation that resynthesis ATP in skeletal muscle.
Substrate-level phosphorylation - PCr and glycolysis
Oxidative phosphorylation
What are the two enzymes involved in the resynthesis of ATP in PCr system and their function?
Creatine kinase - removes Pi from Cr
Adenylate kinase - phosphorylates ADP
Where does glycolysis occur?
Cytosol
Sources for glycolysis and its products?
Circulating glucose
Stored glycogen in skeletal muscle, liver
2 x pyruvate
Or, 2 x lactate
What enzyme is responsible for converting glucose into glucose-6-phosphate?
Hexokinase
What metabolite is oxidised in glycolysis and why is it important?
NAD+ - must be oxidised for pyruvate to enter krebs cycle
What enzymes are responsible for the conversion of pyruvate (2)?
Pyruvate dehydrogenase - to acetylcoA
Lactate dehydrogenase - lactate
What is the importance of the citric cycle?
Oxidation of electron carriers which can be used in oxidative phosphorylation
What happens to the metabolites in oxidative phosphorylation?
H+ move across mitochondrial membrane to create electrochemical gradient to activate ATP synthase
What is the final product of oxidative phosphorylation?
H20
What type of oxidation does fat undergo to enter Krebs cycle?
beta oxidation
What are the main 2 factors affecting exercise?
Exercise intensity and exercise duration
What is the importance of recovery in between exercise bouts?
Allows for the replenishment of ATP
What is the preferred source of fuel in endurance exercise?
CHO
Respiratory exchange ratio equation
VCO2 / VO2
What is fatigue?
Exercise induced decrease in ability to produce force
Factors influencing fatigue?
Reduced ATP
Reduced PC
Increased Pi
Increased H+
What is metabolic acidosis?
Increased presence of H+ decreases pH
Therefore, affecting rate of enzyme function
Possible mechanisms of fatigue (4)
Reduced calcium reuptake
Reduced calcium release
Calcium insensitivity
Transport of potassium
Causes of fatigue during endurance exercise? (4)
Reduced CHO stores
Impaired handling of calcium
Reduced propagation of sarcolemma
Greater reliance of fat
What enzyme is responsible for the breakdown of glycogen stores?
Glycogen phosphorylase
Why is lactate produced?
The system cannot keep up with the demand of pyruvate conversion to acetyl-coA
Regulation of glycogen phosphorylase
Increased epinephrine and IC calcium activates phosphorylase kinase
Phosphorylase kinase activates glycogen phosphorylase
Via a process called covalent regulation
What is an allosteric regulator?
Direct interaction with another molecule to change its function, e.g. ADP and AMP
What stimulates phosphofructokinase?
Products of ATP - ADP and AMP
Fructose-6-phosphate
What reducing equivalent is important in the conversion of pyruvate to lactate?
NADH to NAD+
What are the key regulators during intense exercise? (2)
Phosphorylase
Phosphofructokinase
What activates release of CHO from the liver?
Increased epinephrine
Increased glucagon to insulin ratio
Increased glucose output
How does circulating glucose enter skeletal muscle?
GLUT4 transporter - further detail in block 3 cards
Regulation of PDH enzyme during exercise.
Regulated via covalent regulation of PDH phosphotase
Increased IC calcium activated PDH phosphotase
PDH activated by the removal of Pi
What stimulates isocitrate dehydrogenase and alpha-ketoglutarate dehydrogenase in the TCA cycle?
Increased intracellular calcium
What is the breakdown of fat in adipose tissue called? And what enzymes are involved?
Lipolysis
TG lipase and hormone sensitive lipase
What does FFA bind to in the blood
Albumin
What stimulates breakdown of fats?
Increased epinephrine
And increased IC calcium in muscle stores
What molecule transports fat into the mitochondria and what process occurs?
Carnitine
Beta oxidation
Why isn’t fat recruited at higher intensities? (4)
CHO regenerates ATP at a faster rate
Decreased adipose tissue blood flow
Inhibition of HSL
Decreased transportation of fat via carnitine
What regulates rate of beta oxidation?
Beta-HAD
What 3 structure uses the most ATP in the body during exercise, and what do they allow?
Myoisin ATPase
Calcium ATPase
Na+ and K+ ATPase
Where do the two steps of substrate phosphorylation take place in the glycolysis?
Formation of glucose-6-phosphate
Fructose-1,6-bisphosphate
How many molecules of glucose produce ATP?
2 x ATP from circulating glucose
3 x ATP from stored glucose
