PT721 - Unit 1 - Energy metabolism

What are the 6 uses for ATP

1) active transport across membranes
2) protein synthesis
3) muscle contraction
4) making PCr
5) synthesizing and secreting glandular secretions
6) active pumping of ions for nerve conduction

In terms of initiating exercise, what are the training adaptations that can allow you to reach steady state more quickly?

-increased capillaries
-increased mitochondrial density
-increase RBCs

What is steady state?

the point where the oxidative pathway for energy generation is fully working such that it provides most of the energy needed

Aside from training, what is the other factor that can influence how quickly someone reaches steady state when exercising?

exercise intensity. The higher the intensity, the longer it will take to reach steady state

What are the internal factors that raise BMR?

-increased lean muscle mass - increases energy expenditure b/c of tone
-increased thyroid hormone secretion - increase metabolic rate, produces more heat
-increased testosterone secretion - anabolic effect that builds more lean mass
-increased growth horm

Why is BMR usually lower for women than men?

Women have less lean mass and in general they are typically smaller

Why does BMR decline with age?

-less lean mass due to fatty infiltration that occurs with age
-decreased sensitivity and/or decreased output of GH and testosterone

Why is BMR lower in sleep?

-less muscle tone
-less CNS activity

What is the thermic effect of food and how much does it contribute to daily EE?

This is the caloric cost of digesting, absorbing and storing macronutrients.
*only makes of 8% of total daily EE

Eating carbs and fats can elevate metabolic rate by 4%, but protein elevates it higher. How much higher? Why does this not make a huge difference to total daily EE?

a primarily protein meal will elevate metabolic rate 30% for 3-12 hours, but this is only elevating the thermic effect of food which already only accounts for 8% of total daily EE.

How much of total daily EE does BMR normally account for?

~60%

What is the most effective way to enhance total daily EE?

increase the amount of physical activity

What is the typical contribution of physical activity to total daily EE?

~25%

What is non-exercising activity and how much does it contribute to total daily EE?

This is unplanned unpurposeful movement that includes fidgeting, posture, and muscle tone

What is allometric scaling and why is it important for comparing BMRs if different people?

-this is scaling BMR relative to another variable such as surface area, body weight, or lean mass
-men and women for example have very different BMRs largely b/c of differences in lean mass so by allometrically scaling BMR for lean mass, you can compare a

What is a MET and how is it usually written?

-this is a Metabolic Equivalent which means it's measures the rate of energy expended for a given activity or intensity level relative to body weight
-it is written as mLO2/kg body weight/min

what is one MET?

3.5 mLO2/kg BW/min

What does it mean if you acribe more METs to a given activity?

That the intensity if higher and it will therefore expend more energy more quickly

What is the difference between measuring BMR and resting metabolic rate (RMR)?

measuring BMR is more stringent in terms of parameters
-longer fasting time
-no vs minimal excitement stimulation
-must have a constant temperature
-no physical activity 2 hours prior
*RMR does not have these requirements

During high intensity exercise, there are actually two factors that can cause more lactate to form instead of pyruvate. What are they? When do they tend to come into play?

1) lack of oxygen - this happens at the onset of exercise when energy is still being largely produced anaerobically
2) backup of pyruvate waiting to enter citric acid cycle - rather than stop producing energy at all, lactate is formed which frees up NAD t

What are the typical RERs for at rest, burning all fats, and burning all carbs?

-resting: 0.78-0.8
-all fat: 0.7
-all carb: 1.0

What is the RER equation?

RER=VCO2 output/V O2 uptake

Why is it difficult to say how much ATP burning proteins nets?

b/c different types of AAs will enter the oxidative pathway at different points as different compounds. They can go into the citric acid cycle as intermediates, or as pyruvate or as acetyl CoA

What happens when you eat more calories than you need to exactly meet your daily demands, but you don't consume any fat in those calories? Does it mean you won't gain weight?

-an excess intake of calories will be stored as fat therefore you will gain weight regardless of whether you actually consume fat
-AAs and CHO can both be converted to triglycerides and stored in adipose tissue

T/F, it takes more energy to convert CHO and proteins to fat for storage?

Yes, it requires less energy to take in fat and store it as fat compared to converting the other macronutrients to fat so they can then be stored. Still, the cost isn't significant enough that it cancels out the effect of consuming excess calories

Suppose you have an 18 carbon FFA. What must happen to it in order for it to enter the citric acid cycle?

-first it is beta oxidized: two carbons are separated from the rest of the chain
-the two carbons separated in beta oxidation are then attached to Coenzyme A to form acetyl CoA
-this product can then enter the citric acid cycle

T/F, beta oxidation has to occur 6 times to fully burn a 12 carbon chain FFA?

True. Beta oxidation would be repeated six times to make six acetyl coenzyme molecules that could enter the citric acid cycle

T/F, glycerol can be used for glycolysis?

True. When separated from the three FA chains that make it a triglyceride it can then be put through the glycolysis process like glucose

What role to FADH and NADH play in the oxidative pathway?

-they are produced by glycolysis and the krebs cycle and they shuttle electrons and protons from those points to the ETC to increase ATP production

What is the goal of the Krebs Cycle?

-to produce electron carriers
-to remove hydrogens and harness the energy of the molecules of the krebs cycle

What intermediate is required to keep the krebs cycle going?

oxaloacetate. Sometimes this can be provided by a protein entering the cycle.

Why is it necessary for the phosphogen (ATP-PCr) and glycolytic systems to provide most of the necessary energy in the first few minutes of exercise?

B/c oxygen is not available metabolically yet on the scale needed at the beginning of exercise so these anaerobic systems are needed as a buffer to give the body time to get aerobic respiration going.

What are the two fates of lactate after exercise?

1) it can turn back into pyruvate and be run through the citric acid cycle
2) it can travel to the liver and be used to make glucose via gluconeogenesis

What makes PCr such a good buffer for meeting high rate of ATP demand at the beginning of exercise?

-there is higher energy in the PCr bond than for P bonding to ADP so the PCr is eager to drop in energy and form the new bond with ADP

What three factors govern which substrates are used to meet ATP demands?

1) substrate availability
2) ATP demand (both rate and duration requirements)
3) oxygen availability

T/F, muscle glycogen to be turned back into glucose and released to the blood stream to enhance blood glucose levels?

False. Only the liver has the enzyme necessary to turn glycogen back into glucose to be released into the bloodstream. Therefore, the liver manages blood glucose levels with its glycogen stores and the muscles utilize their glycogen stores directly to spa

What will a muscle use first when it becomes active and needs more energy? Why?

It will use its intracellular stores of glycogen and triglycerides b/c other energy sources need time to be transported through the blood and carrier across the muscle's cell membrane.

If you don't know the exact RER, but want to estimate calorie expenditure what is the usual number used?

5 calories/L O2