PTE 764: quest 1

bioenergetics, metabolism, metabolic responses, and lab info

what is the study of bioenengetics?

the flow of energy in living things and the take up of that energy stored in chemical bonds and transforming it into mechanical energy (movement)

what is energy?

the capacity to do work and is in a dynamic state that is “measured” with change

what is work?

a measure of amount of force produced and the distance over which that force is exerted

what is power?

the rate (how fast or slow) at which work is done

what is the first law of thermodynamics?

energy can neither be created nor destroyed (however it can be transformed)

what are the two types of energy?

1. potential energy: the energy an object has due to its position or arrangement within a system, possessing the capability to be converted into kinetic energy

2. kinetic energy: the energy an object possesses due to its motion; dependent on object’s mass and speed

what are exergonic reactions?

“downhill reactions” that release energy

• ΔG is negative = exergonic reaction (catabolism)

what is a side effect of an exergonic reaction?

the generation/release of heat

what are endergonic reactions?

“uphill reactions” that store (potential) energy

• ΔG is positive = endergonic reaction (anabolism)

what is the second law of thermodynamics?

in all energy exchanges, if no energy enters or leaves the system, the potential energy of the end state will always be less than that of the initial state

• drop in energy = entropy

what is activation energy?

the phenomenon where energy needs to be placed into a state to get energy out of that state

T or F: enzymes containing a dehydrogenase molecule lower the activation energy.

T

organisms need energy to maintain order and life. how does an organism gain more energy?

• fueling body through food

• reformation of ATP

what does it mean if an organism has high entropy?

the organism ceases to take in energy and dies… RIP

what is one way heat energy may be dissipated?

through sweat

what are the three types of human work?

1. mechanical work: muscle contractions, mitosis, cilia

2. chemical work: maintenance and growth of tissues

3. transport work: moving ions

T or F: the flow of energy defines the limits of exercise intenisty.

T

what are the two roles of enzymes?

1. accelerate chemical reactions

2. reduce activation energy

why does the rate of enzymatic activity increase during exercise?

• increase in energy demand

• increase in intermediate substrates during metabolism

• increase in heat generated by body (making faster reactions)

• allosteric regulation

why do athletes typically perform warm-ups before events?

it mobilizes enzymes which assists the body in producing the work and power needed

______ can either activate or inhibit an enzyme.

substances

which substance inhibits glycolysis at key enzymatic steps of catabolism?

ATP

T or F: fat burns over a carbohydrate flame.

T

what’s the difference between competitive inhibitors and non-competitive inhibitors?

• competitive: mimic substrate by binding to the active site of the enzyme; acting as an on and off switch

• non-competitive: bind to an enzyme causing a change in the shape of the molecule and decreases activity

what are the two types of enzymatic reactions?

1. hydrolysis and condensation

2. oxidation and reduction reactions (REDOX)

what are the two components of a REDOX reaction?

1. reducing agent: substance that donates electrons and itself is oxidized

   • example: lactate

2. oxidizing agent: a substance that receives electrons

   • example: pyruvate

how do we measure energy conversion (metabolism)?

1. heat production

2. oxygen consumed

3. carbon dioxide produced

direct calorimetric

measurement of heat production

indirect closed-circuit spirometry

measurement of oxygen consumed

indirect calorimetry: open-circuit

measures oxygen consumption and carbon dioxide production

T or F: ATP is not recycable.

F; ATP must be recycled as the cells have little amounts

what are the four sources of ATP recycle?

1. readily amounts of ATP in the cytoplasm of the cell

2. the transfer of phosphate group from phosphocreatine

3. glycolysis

4. oxidative pathways

of the four sources of ATP recycling, which on is the ONLY aerobic reaction?

oxidative pathways

where do the three anaerobic sources of ATP occur?

in the cell’s cytoplasm

• the aerobic source occurs in the cell’s mitochondria

what is the end product of glycolysis?

pyruvate

once glycolysis is complete, pyruvate can do two processes. what are they?

pyruvate can then either (1) produce more energy through the oxidative pathways or (2) be reduced to from lactate acid in the absence of aerobic metabolism

how do individuals perceive an increase in lactic acid?

a burning sensation

what other two molecules (besides pyruvate) can be metabolized through oxidative pathways?

lipids and to some extent proteins

ATP source chart

______ facilitates the entry of glucose into the cell.

insulin

T or F: glucose can enter the cell without insulin.

T

• can enter primarily at rest via cortisone

glucose always needs a transporter to enter the cell. what are the two discussed in the notes?

1. glut-1: not sensitive to insulin (happens at rest; within brain)

2. glut-4: sensitive to insulin (happens with exercise; within muscle and adipose)

when does the synthesis of glycogen typically occur?

normally stimulated by insulin in response to high serum glucose levels → the elevated glucose levels triggers the cell to synthesize it into glycogen to store it

glycogen synthesis is under the influence of ______ enzyme.

synthetase

when does the breakdown of glycogen typically occur?

when our body is performing activities (need to mobilize our fuel source)

breakdown of glycogen is under the influence of ______ enzyme.

phosphorylase (A)

phosphorylase (B) is the inactive form of phosphorylase (A) so it must undergo conversion B→A for glycogen breakdown to occur. what stimulates this process?

increases in calcium ions and epinephrine which are associated with stress and work

________ is an enzyme from the liver and kidneys that allows glucose-6-phosphate to exit the cell and stimulate more glucose.

phosphatase

• occurs when serum glucose is low

glycogen storage disease (GSD)

a group of inherited metabolic disorders that affect the body's ability to store or break down glycogen

you notice in your patient’s chart that he was diagnosed with GSD. what are you expecting from him during treatment?

lack of strength/overall weakness, fatigue, lack of metabolism

McArdle’s Disease

a rare inherited muscle disorder that affects the body's ability to break down glycogen, a stored form of glucose in muscles

why do carbohydrates provide energy for cellular work?

• stored energy can form ATP without oxygen

• during light-moderate exercise, carbs supply 1/3 of a person’s energy requirements

• even usage of large quantities of lipids for energy, there is a requirement for some carb metabolism

• metabolism of carbs is rapid

glycolysis is important for activities that take place up to ___ seconds.

90

what are the three general stimulants of glycolysis?

1. decrease oxygen levels (hypoxia): decrease in Kreb’s cycle and oxidative phosphorylation

2. increase in ADP and Pi levels: energy starved

3. increase calcium inside the cells: contracting skeletal muscle

what is the bottleneck (limiting) enzyme for glycolysis?

phosphofructokinase (PFK)

• increase of activity of PFK during maximal exercise to control glycolysis

what are the four factors that inhibit PFK?

1. ATP

2. citrate

3. low pH

4. glucagon

what activates PFK?

ADP and AMP (high energy demands)

the dephosphorylization of _________________ produces ATP (gives us energy).

phosphoenolpyruvate (PEP)

pyruvate kinase is the enzyme responsible for converting PEP into pyruvate. what can inhibit this conversion?

alanine (an amino acid that signals cell of too much pyruvate)

following glycolysis, what happens to the extra NADH?

either (1) continues through fast/anaerobic process to assist pyruvate in creating lactate or (2) continues through slow/aerobic process to help with oxidation via ETC and Kreb’s cycle to produce more ATP

NADH requires a transporter to enter into a cell’s mitochondria. what are the two transporters/shuttles?

1. malate-aspartate shuttle: for heart and liver cells

2. glycerol-phosphate shuttle: for skeletal muscle and brain cells

a feed-forward system gets a process moving. what are two examples of feed-forward regulations for glycolysis?

1. glycogenolysis: stimulated via epinephrine and muscle contractions

2. glucose uptake: stimulated via insulin and muscle contractions

a feedback system inhibits or slows a process. what are some examples of feedback regulations for glycolysis?

• phosphofructokinase (PFK)

• cellular energy charges

• lactate de-hydrogenase

• pyruvate de-hydrogenase

• cytoplasmic redox potential

LDH competes for pyruvate when glycolysis is slow. describe the two types of LDH we discussed?

1. M (muscle and anaerobic) type has a high affinity for pyruvate

2. H (heart and aerobic) type has a low affinity for pyruvate

   • but has a high affinity for lactate and can actually increase pyruvate

what are the two forms of lipase?

1. lipoprotein lipase: promotes storage of lipids; stimulated by insulin and glucose

2. hormone sensitive lipase (HSL): promotes the release of lipids from adipose tissue; stimulated by epinephrine, norepinephrine, and growth hormone

what are the seven steps of lipid metabolism?

1. mobilization

2. circulation

3. uptake

4. activation

5. translocation

6. beta-oxidation

7. mitochondrial oxidation

the key point of mobilization of a lipid (free fatty acid) is to get it into the blood’s circulation. how does that happen?

free fatty acid (FFA) must be bound to albumin to transport through the blood

translocation of a FFA involves stripping of “original” CoA, transporting activated FA into the mitochondrial matrix, and then rebinding a “new” CoA. what co-enzyme is needed for this process?

carnitine

T or F: carnitine can be recycled.

T

carnitine deficiency may result in or be present in….

• myopathy

• hypoglycemia

• cardiomyopathy

T or F: glucose produces more ATP than lipids.

F; lipids produce more ATP but glucose is more efficient and faster

what is the feed-forward regulation of lipid metabolism?

circulating FFA level is controlled by adipose lipolysis rated under hormone sensitive lipase (HSL) regulation

• HSL is usually epinephrine

what is the feedback regulation of lipid metabolism?

acetyl CoA inhibits beta-oxidation; signaling to the body that Kreb’s cycle is doing well

if the Tricarboxylic Acid Cycle (TCA)/Kreb’s Cycle is not the main energy producing reaction within the body, why is it important for it to occur?

it gives off reducing equivalences (FAD and NADH2) which go to other reactions/cycles to create ATP there

what three sources produce acetyl CoA for the kreb’s cycle?

1. from pyruvate (CH2O)

2. from fatty acyl CoA (lipids)

3. from amino acids (proteins)

TCA: oxidation of isocitrate

• substrate: isocitrate

• enzyme: isocitrate dehydrogenase

• product: oxalosuccinate

• oxidizing agent: NAD+

• NAD+ is reduced to NADH + H

• production of CO2

TCA: oxidation of alpha-ketoglutarate

• substrate: alpha-ketoglutarate

• enzyme: alpha-ketoglutarate dehydrogenase

• product: succinyl CoA

• oxidizing agent: NAD+

• NAD+ is reduced to NADH + H

• production of CO2

TCA: production of succinate

• substrate: succinyl CoA

• enzyme: succinyl kinase

• product: succinate

• synthesis of ATP

• production of CO2

TCA: oxidation of succinate

• substrate: succinate

• enzyme: succinte dehydrogenase (SDH)

• product: fumarate

• oxidizing agent: FAD+

• FAD+ is reduced to FADH2

TCA: oxidation of malate

• substrate: malate

• enzyme: malate dehydrogenase

• product: oxaloacetate

• oxidizing agent: NAD

• NAD+ is reduced to NADH + H

tally of Kreb’s Cycle/TCA chart

what are the feed-forward regulations of TCA/ Kreb’s cycle?

1. production of acetyl CoA

2. production of oxaloacetate

what are the feedback regulations of TCA/ Kreb’s cycle?

1. isocitrate dehydrogenase (bottleneck/limited enzyme)

2. cellular energy charge

3. mitochondrial redox potential

what is the ATP count associated with the reducing equivalences at the end of the electron transport chain (ETC)?

NADH = 3 ATP

FADH = 2 ATP

when studying metabolism during exercise, what is considered the steady state time frame?

1-4 mins

what are the three evens occurring at the steady state?

1. energy requirements are met by aerobic metabolism

2. a state of inadequate oxygen consumption exist at the tail end of the lag period; have an oxygen debt

3. the fuel used from rest to light exercise for aerobic metabolism is glycogen (glucose)

what time frame dictates a short term high intensity exercise?

5-60 secs

• activities under 5 secs: energy from ATP-CP system

• activities around 30 secs: energy from combo of ATP-CP and anaerobic/rapid glycolysis

short term high intensity exercises mainly utilize the substrate _______.

carbohydrates

although the exercise duration is “short”, why does blood lactate continuously rise throughout exercising?

lactic acid is the by-product of anaerobic activity (glycolysis) so as the activity continues so will the production of lactic acid

what occurs at the anaerobic/lactate threshold?

the body has saturated it’s anaerobic systems (pyruvate and O2) so it will switch to aerobic systems

what does the anaerobic/lactate threshold tell us?

how aerobic a person is

T or F: anaerobic glycolysis exists when the hydrogen (NADH) produced is oxidized at about the same rate as it becomes available meaning production = utilization.

F; its aerobic glycolysis

what is the final product of aerobic glycolysis?

pyruvate

steady state sub VO2max can be maintained during 10-60 mins of sub-max continuous exercises. what are the two exceptions to this statement?

1. hot, humid environments

2. continuous exercise at a relatively high workload

while exercising in the above environments (hot, humid, and high intensity), the body experiences a slow rise in VO2 due to an increase in serum catecholamines. what do these do?

• stimulate lipolysis (HSL) → increases FFA

• stimulate the breakdown of glycogen (phosphorylase) → increases serum glucose

• may release glucagon in the presence of depleted serum glucose levels

prolonged sub-max exercises mainly utilize the substrates ___ and ____.

lipids and carbohydrates