Exercise Physiology

bioenergetics

the chemical process of converting food into energy; metabolism

• body converts food to useful energy

monosaccharides

glucose, fructose, galactose

• easy energy for exercise

single 6 carbon ring

disaccharides

maltose, sucrose

• linked monosaccharides

polysaccharides

starch, cellulose, glycogen

• large forms of monosaccharide linkages

• steady release over time into the bloodstream

glycogen

complex chain; storage form of glucose in animals typically stored in the muscle and liver

• used by the muscle that stores it

• liver glycogen can be used throughout the body

combining glucose monomers into the chain is the solution to store carbs in muscle cells so that you manipulate osmolarity

glucose

simple sugar (monosaccharide) that can be used for energy or stored as glycogen

glycogenesis

formation of glycogen from glucose

• putting the chains together

glycogenolysis

the process of breaking down glycogen into glucose

• breaking up the linked chains

gluconogenesis

generation of glucose from non carbohydrate carbon substances like pyruvate, glycerol, glucogenic amino acids, or lactate; takes place primarily in the liver

• liver takes up other molecules to form new glucose and maintain homeostasis

hyperglycemia

an excess of glucose in the bloodstream often associated with diabetes

type 1 diabetes: body doesn’t make insulin, insulin producing cells are attacked

type 2 diabetes: body cannot use insulin or make enough of it so you get no response; cell tries to make more insulin to take up glucose but you get no response

**breaking down muscle mass can send glucose to bloodstream

hyperinsulinemia

a condition in which there are excess levels of insulin circulating in the blood than expected relative to the level of glucose; too much insulin because the cell is trying to make more to pick up the excess glucose but you get no response so it’s just an insulin build up

insulin

produced by beta cells in the pancreas

• secreted when blood glucose levels are high

• stimulates translocation of glucose transporters and uptake of glucose in both skeletal muscle and adipose tissue (insulin makes transporters to take up blood glucose)

• stimulates glycogen synthase and glycogenesis (we want to sequester glucose away to make glycogen so there’s more room for glucose in the blood… don’t want to mess up blood omsmolarity)

glucagon

produced by alpha cells in the panreas

• secreted when blood glucose levels are low

• stimulates glycogen phosphorylase and glycogenolysis (breaks down glycogen so we get glucose in the blood)

**exercise uses up stored glucose so insulin decreases and glucagon increases to make more glucose to keep blood sugar steady; insulin is usually the only hormone that goes down with exercise

glucose transport in skeletal muscle

insulin binds to start a signalling pathway which then allows glucose to be taken into the cell

• simple sugars right before exercise spikes insulin but not a problem because exercise will regulate the SNS to push blood to muscles that are active… insulin will have less effect at notworking tissue

• if you wait longer, the body begins to compete with where the insulin/glucose goes

• eating right after exercise is needed because insulin receptors are still active so you can restore what the muscle just used… protein aids in this process

**exercise works just like insulin pathway

muscle glycogen

400g of carbs

can only use what is stored here

liver glycogen

100g

this glucose can be used anywhere in the body

fats

can be metabolized for energy

composed of fatty acids and triglycerides

fatty acid

simple carbon chain (usually 12-16 carbons long)

• can be saturated, monosaturated, or polyunsaturated

triglyceride

stored fatty acids

• form of fatty acids stored in fat cells and other cells like skeletal muscle

• glycerol molecule plus 3 fatty acids

• broken down by lipase in the process of lipolysis for energy

• stores are abundant, cannot be depleted

break this apart for useable energy (see this in the blood)

saturated fatty acid

contains max number of hydrogen atoms and no double bonds; fully saturated with hydrogen

• have to be warm to be moveable, otherwise they are compressed and remain firm/stiff

• this is why they function best above room temperature

unsaturated fatty acid

does not contain max number of hydrogen atoms and has at least 1 double bone (bond shared between carbons so not all are saturated with hydrogen)

• changes the shape!!

• fish have these because they like to be in cold water! otherwise they’d be a stiff block of fat

monounsaturated fatty acid

at least 1 double bond in the fatty acid

polyunsaturated fatty acid

more than 1 double bond in the fatty acid

has health benefits

lipolysis

fatty acid metabolism is regulated by the availability of fatty acids which are generated from the breakdown of triglycerides

• broken down by lipase which is activated by epinephrine, norepinephrine, growth hormone, atrial natriuretic hormone, brain natriuretic hormone, and glucagon (need energy from fat when carbs are low)

• lipase inhibited by lactate, insulin, ketones

insulin affect on liapse

inhibits it

• takes up glucose in the blood to be used as energy so we don’t need energy from fat, therefore no lipolysis

ketones affect on lipase

signals that we don’t have enough glucose available, liver tries to maintain blood glucose but incomplete oxidation occurs so you get ketones

protein

only a small amount metabolized for energy

• central carbon bound to a hydrogen, an amino group, acid group, and unique side change

• 9 essential amino acids that must be digested, cannot be synthesized

• nonessential amino acids can be synthesized

**side chain dictates how the proteins fold

**can examine nitrogen excretion to see how much is being broken down

glucogenic

can be rearranged from broken down amino acids to make more glucose in the liver

• alanine glucose cycle

ketogenic

can enter into the cycles to help form intermediates

• citric acid cycle intermediates

enzymes

protein molecules that facilitate a chemical reaction by lowering the activation energy required to carry out said action; does not initiate reaction, only speeds it up

• one enzyme is the rate limiting step in multi step reactions, only as fast as the weakest link

• can only bind to the right shape, can use drugs to mimic

catabolic reaction

breaking down of substrate into molecules so you release energy

anabolic reaction

using energy to form a product from separate molecules

ex: anabolic steroids enhance the building of tissues

mass action affect

the concentration of substrates and products determines which direction the reaction will go (if you have a lot of the product, reaction will move towards the reactants and become catabolic)

• often require coenzymes

• affected by temperature, acidity, and need for coenzymes (faster at higher temperatures and very specific range of acidities)

ATP

adenosine triphosphate

adenosine + ribose + 3 phosphate molecules

• broken down to release energy to the cell and increase the acidity because you are increasing H+

exergonic

yields energy (releases heat)

endergonic

needs energy

ATP production

not enough stored to sustain long term exercise

• ATP made in first 30 second, 30 seconds to 3 minutes then uses glycolysis

• longer than 3 minutes uses metabolism which requires oxygen and the mitochondria

ATP PC system

PC = phosphocreatine

• short intense sprints and vertical jumps

• small amount of ATP in cells so must be replenished by phosphocreatine quickly; enzyme creatine kinase breaks down PC into creatine and phosphate; phosphate is donated to ATP to replenish ATP (we take creatine to make more PC that can be used in recovery)

depletion of phosphocreatine

not the primary cause of decreased muscle force and fatigue… more likely due to accumulation of phosphate and increased acidity from hydrolysis of ATP

when breakdown of PC does occur, an aerobic recovery period is necessary to provide energy to reform PC; this is why high intensity bouts are combined with lower intensity recovery periods

adaptations of ATP-PC system

increases in activity of enzymes like creatine kinase can result in faster regeneration of ATP (more enzymes available to break PC into useable ATP)

in anaerobic training, ATP and PC may be increased at rest

anaerobic metabolism

first 30 seconds of exercise dependent on ATP-PC; will quickly be depleted (PC broken down so ATP can use the P)

30 seconds - 3 minute is glycolysis

• when anaerobic, no O2, pyruvate from glycolysis is converted it lactate

• when O2 present, usually in extended lower intensity bouts, pyruvate enters aerobic pathways instead

**ADP - ATP imbalance is a humeral factor that drives metabolism to occur; ADP concentration is a signal for metabolism to start because it means you’re out of ATP

glycolysis

enzymatic reactions that metabolize glucose, occurs in cytoplasm and results in ATP production from breakdown of glucose

** glucose can be supplied from blood glucose via transporters/insulin or from glycogen stores

• produces energy for aerobic and anaerobic metabolism but does not use O2 itself; either converts pyruvate to acetyl co A for aerobic pathway or to lactate and recycled into glucose

steps of glycolysis

1. start with glucose or glycogen and use ATP to break it down into fructose

2. use more ATP to break it down more

3. 4 ATP total and 2 NADH made (NADH is an intermediate energy of sorts), then 2 pyruvate molecules

4. NADH donates H+ back to make more BAD+ for glycolysis to keep going; H+ donation increases acidity which decreases pH which can shut things down

• pyruvate can’t leave the cell on its own so it’s converted to lactate than can leave the cell and glycolysis can continue; tissue can take up lactate and convert it back to pyruvate if needed for aerobic metabolism

5. end with 2 ATP if starting from glucose and 3 ATP if starting from glycogen because it takes one less ATP to get started

hydrogen production of glycolysis

ATP is required to begin; hydrogens are produced by NADH when pyruvate is converted to lactate

• donated hydrogens at the end can be picked up by NAD+ to transport hydrogens to mitochondria for aerobic metabolism

• if aerobic metabolism does not accept hydrogens, pyruvate can accept them to become lactate

glycolysis enzyme adaptations

changes in glycolytic enzymes may improve performance by increasing ATP availability from glycolysis

• more glycogen phosphorylase that breaks down glycogen to glucose may enhance performance if you have more glycogen to use and release

• PFK (phosphofructokinase) is the rate limiting enzyme so increasing this can increase the rate of glycolysis

• LDH (lactate dehydrogenase) converts pyruvate to lactate so increasing this can increase the rate of producing lactate

**PFK will have more impact than others because it’s rate limiting

**if you want to improve aerobic glycolysis, you have to stress aerobic glycolysis

glycolysis training adaptations

• increases in intramuscular glycogen can affect glycolytic and aerobic production of ATP; this is increased by endurance training… have to train to deplete glycogen and get better at building it; weight and sprint training don’t have enough of this stimulus

• length of training and type of training affects how your systems work; if you want to get good at running fast, you have to train that system that powers you to run fast

glycolysis buffering adaptations

improving the ability to buffer acidity of hydrogen ions produced in glycolysis increases performance and recovery

• buffers like bicarbonate combine with H+ ions to form a weaker acid so that acidity isn’t too high and body can function (you will have more CO2 though so then you have to breathe harder to breathe off CO2)

• endurance and sprint training increase buffering capabilities which is thought to prevent acidity-associated fatigue; but you can still produce decent force in acidic conditions

aerobic metabolism

provides a majority of energy during long duration, low intensity physical activity (ex. marathon)

• need aerobic engine for anything longer than just 1-2 minute bursts

• about 80% of energy comes from this system when activity longer than 10 minutes

• the longer the sprint, the greater the percentage of ATP derives from glycolysis and aerobic metabolism instead of ATP-PC system

time required to restore ATP and PC system

about 120 seconds of rest is required to resynthesize intramuscular ATP and PC after a 40m sprint

• if rest is not sufficient, performance may suffer because then you start to rely on a slower system of ATP production… if you improve ATP system, less rest is required because system gets more efficient

krebs cycle

system in aerobic metabolism after pyruvate is made in glycolysis

• oxidizes substrates (removes hydrogens and electrons) and produces some ATP

• hydrogens are removed and taken to ETC

electron transport chain

system that follows the krebs cycle

• NAD+ becomes NADH and FAD becomes FADH in krebs and takes hydrogens here

• produces majority of ATP during aerobic metabolism, called oxidative phosphorylation

• forms water from hydrogens and oxygen becomes final electron acceptor

steps of krebs cycle

1. pyruvate from glycolysis is broken down into acetyl CoA, a molecule that can enter the cycle

2. acetyl CoA combines with oxaloacetate to form citrate, a 6 carbon molecule; liver sometimes uses this to make glucose so then oxidation doesn’t finish and you get ketones

3. citrate goes through a series of reactions to produce 2 CO2, 1 ATP, 3 NADH, and 1 FADH2

steps of electron transport chain

1. pairs of electrons are passed through releasing energy to phosphorylate ADP and make ATP

2. energy released is used to pump H+ from inner to outer membrane of mitochondria, creating a gradient

3. H+ flowing activates ATP synthase which makes ATP

4. oxygen acts as final electron acceptor by forming H2O

**H+ from NADH provide more energy than those from FADH2 because NADH enters at an earlier point so they can pick up more energy

oxygen free radical

can sometimes produce ½ an oxygen molecule at the end of the ETC that can react with anything; this increases with exercise due to metabolism