metabolic control and regulation Flashcards
how much energy do we get from carbohydrates, lipids & proteins?
- carbs: 4kcal
- lipids: 9kcal
- protein 4kcal
basal metabolic rate (BMR (Kcal)
minimum amount of energy needed
how much energy do humans need?
men: 66 + (13.7xweight) + (5xHeight) - (6.8xAge)
women: 655 + (9.6xW) + (1.7xH) - (4.7xA)
abbreviated weir formula
resting energy expenditure (REE)
REE= 3.9(VO2) = 1.1(VCO2) = 1.44
energy balance
- energy intake (calories eaten) & energy expenditure (calories burned)
- the center of obesity and T2D
- helps us understand energy requirements of athletes
- need to understand how the body uses fuel
- how to accurately measure energy intake (EI) and energy expenditure (EE)
when will body mass stay the same?
intake = expenditure
when will body mass increase?
intake > expenditure
when will body mass decrease?
intake < expenditure
how to measure energy expenditure?
- accelerometer
- doubly labelled water
doubly labelled water
- best method to measure day to day expenditure
- water labelled with 2H and/or 18O, initially applied to measure body composition
simplistic overview of metabolism
- consumption of food filled with energy
- release of energy -> breaking down sugar releases energy -> energy used by cells to perform functions
- digestive system -> digestive enzymes break carbohydrates into sugars (glc), fats into fatty acids and proteins into a.a
- enzyme meet up -> more enzymes meet & bind with compounds -> undergo chemical reactions
- energy store -> reactions happen to release energy for immediate or future use -> energy stored in skeletal muscles, liver or body fat
ATP
- adenosine triphosphate
- large amount of free energy if broken down
- 7.3kcal of free energy
- breaking of high energy phosphate bonds (outermost P)
ATP + H2O -> ADP + Pi + H+
where is ATP used?
- digestion
- circulation
- muscle contraction
- tissue synthesis
- nerve conduction
- glandular excretion
if we had no ATP / couldnt produce ATP
- death
- rigor mortis
ATP and muscle contraction
- myosin head attaches to actin myofilament -> cross bridge
- inorganic P generation in previous contraction cylce released -> initiates power (working) stroke -> myosin head pivots & bends -> pulls on actin filament, sliding it to M line -> ADP released
- new ATP attaches to myosin head -> link between myosin & actin weakens -> cross bridge detaches
- ATP split into ADP + Pi -> myosin head energized (cocked in high energy conformation) (by released energy)
why do we need ATP for muscle contraction?
- need it to allow cross bridge to form
- without cross bridge = no contraction
- a recycling process
is ATP limited?
- yes
- limited supplied & high demand = ATP needs to be resynthesized (from ADP) to meet needs
- food we eat and store provides energy to recharge ATP
how much ATP does our body store?
80-100g
ATP consumption at rest
1.6kg/hr
ATP usage during strenuous exercise
- rise 20-30 fold
- 0.5kg/min
carbohydrate metabolism
- abundant
- 40-80% of total energy
- broken down to glc units -> taken into cells -> broken down to release energy trapped in glc
- bonds holding glc contains ATP -> need to be broken
- glycolysis
C6H12O6 + 6O2 -> 6CO2 + 6H2O + ATP (36)
how is glc stored?
- as glycogen
- muscles = largest store of glycogen
- livers = provide brain with energy e.g. when sleeping
types of carbohydrates
- monosaccharides (glc, fructose)
- disaccharides (sucrose)
- polysaccharides (starch)
what determines how fast muscle glycogen stores are used up?
exercise intensity
glycolysis - CHO oxidation
- 4 ATP produced
- 2 used up
- net gain of 2 ATP
- glc -> pyruvate
NAD+ & NADH
- electron carries (carry H)
- provides the cell with a mechanism for accepting and donating electrons
- NAD+ = low energy form (accepts electrons)
- NADH = high energy form (donates)
lactate formation
- if anaerobic
- use NADH from stage 5 of glycolysis -> NAD (feeds back to glycolysis)
- pyruvate -> lactate
lactate formation depending on exercise intensity
- light exercise has a lower ATP demand -> removal of pyruvate at same pace as production
- moderate intensity -> lactate diffuses out of muscle fibres into blood -> as exercise proceeds: lactate levels decrease and easily removed at this intenisty with good blood flow (e.g. walking after a run)
- heavier exercise -> lactate conc stays high and constant in muscle & blood -> can be uncomfortable
- high intensity -> increased released of lactate in blood -> reduced muscle function
(acidity in muscle drops)
lactate byproduct in anaerobic conditions
- after intense exercise, the lactate produced diffuses from the muscle into the blood and is taken up by the liver to be converted into glucose and glycogen -> can be recylced
Krebs cycle
- aerobic
- first pyruvate -> acetyl-CoA (mitochondria fluid matrix)
- 2 molecules of pyruvate: 2xCO2 + 4xH+
- 2 molecules of acetyl-CoA: 4xCO2 + 16H+ -> to electron transport chain
electron transport chain (ETC)
- ultimate e- acceptor in aerobic = O2
- e- need special carries to be transferred from food to O2
- use NAD+ and FAD -> NAD+ from glycolysis & krebs, FAD from krebs -> both accept a H+ and 2e- -> NADH + FADH2 -> carry e- to O2 in ETC in inner membrane of mitochondria
- oxidative phosphorylation = ATP formation
- 90% of ATP production
- water also formed
examples of short term challenges to energy
- sprints
- explosive movements
- lifting weights
- need ATP immediately (40-50 fold ATP increase)
effect of cyanide phenylhydrazones
stop ATP formation in the ETC
phosphagen system
- intramuscular store of ATP = 80-100g
- intramuscular store of phsophocreatine (PCr) = phosphagen system
- immediate energy store for muscles
- function as an immediate access reserve of high energy phosphates that can be used to make ATP
type 1 muscle fibres
- low ATPase activity (at pH 9.4)
- slow twitch
- have high oxidative and low glycolytic capacity
- are relatively resistant to fatigue
- slower released energy source
type 1 fibres speed
slow
type 1 fibre glycolysis
low
type 1 fibre energy store used
fat -> slower release
type 1 fibre metabolism
aerobic
type 2a fibres
- intermediate fibers because they possess characteristics that are intermediate between fast fibers and slow fibers
- produce ATP relatively quickly, more quickly than SO fibers
- can produce relatively high amounts of tension.
type 2a fibres speed
moderately fast
type 2a fibres gylcolysis
high
type 2a fibres energy store
PCr, glycogen -> energy attained faster
type 2a fibres metabolism
long anaerobic
type 2x fibres
- fast glycolytic fibers
- fastest twitch speeds
- highly fatigable
type 2x fibres speed
fast
type 2x fibres glycolysis
high
type 2x fibres energy store
PCr, glycogen -> fast
type 2x metabolism
short anaerobic
can we train / change our muscle fibre type?
combine type 1 and 2a and 2x:
- using high velocity isokinetic contractions
- ballistic movements: bench press throws and sprints
from type 2 to type 1:
- longer duration, higher volume endurance events
conclusions.
- exercise induced muscle fibre shifting only exists between fast twitch muscle fibre types
- bi-directional shifting between slow and fast twitch fibres
type 1 fibres found in which atheletes?
- long duration contractile activities
- endurance athletes
type 2a and 2x fibres found in which atheletes?
- short duration anaerobic activities
- higher strength and power
genetics
- e.g. successful endurance athletes tend to be from eastern africa
ATP use in high intensity exercise (in each fibre)
- ATP levels drop dramatically
- 2x: drop fastest
- 2a: middle
- 1: slow twitch fibres go into effect after initial energy burst -> not such an extreme drop
- ATP needs to be resynthesised fast to maintain power output
phosphocreatine
- PCr store in muscle can be used to quickly resynthesise ATP stores in muscle depleted during exercise -> to sustain contractions
- PCr has a higher phosphate transfer pot than ATP (transfers more readily)
- 4x more PCr stored in muscles than ATP
- PCr rephosphorylates the ADP back to ATP
creatine kinase
PCr + ADP + H+ -> ATP + Cr
resynthesis of PCr stores
- adaptations occur after repeated efforts
- ability to e.g. sprint again depends on having ATP available again after it was used in the first sprint
- after 30s PCr replenished by 50%
- 2-3 mins between sets to let PCr regenerate
creatine supplements
- Cr conc in muscle = 110-120mmol/kg/dry weight of muscle
- supplements = 130-160mmol/kg/dry weight of muscle
- more creatine available in cytosol = more ATP able to be resynthesized
success of creatine supplements
- works best for people who do have such high resting creatine levels e.g. vegetarians
- those who conusme e.g. more red meat have higher levels already
effectiveness of creatine supplements
- has a strength gain -> can make ppl stronger
- can train harder for longer with a faster recovery
- increases PCr resynthesis during recovery between high intensity exercise
- enhanced performance
- poor evidence for endurance
creatine and increased body mass
- body mass will increase when taking creatine bc combines with water in body -> Creatine helps increase muscle mass by drawing extra water into the muscle cells, causing you to retain fluid
- While your muscles haven’t actually started growing yet, the increased water is important for future muscle growth, and can be the cause of initial weight gain.
what happens when PCr runs out?
- switch to anaerobic glycolysis (lactic acid system)
gly/glycogen -> pyruvate -> lactate - anaerobic glyc max around 5s into high intensity exercise
- PCr declines fast
- PCr used in final sprints
- anaerobic used to maintain speed in middle distance runs
- when events get longer -> aerobic -> oxygen delivery to muscles to maintain speed
fat as an energy source
- stored fat is most abundant and provides the most energy
- greater energy yield but needs more oxygen per molecule of fat
- glc needs 6O2
- fat needs 23O2
- as you increase exercise you become more reliant on muscle glycogen and less on fat
where and how is fat stored?
- 90% stored as triglycerides
- stored in adipose tissue
triglyceride
3 fatty acids bonded to a glycerol molecule
what happens to fat breakdown when you have a meal high in carbs?
- insulin spike due to carbs -> reduced ability to break down fatty acids
- this is due to the fact that carbs impact hormone sensitive lipase
- once you start exercising -> insulin spike will drop and wont have such an inhibitory effect -> easier to breakdown triglycerides as energy source
-> reduces initial ability to use fats for energy
lipase
an enzyme the body uses to break down fats in food so they can be absorbed in the intestines
- Lipase is produced in the pancreas, mouth, and stomach.
why do fatty acids enter the mitochondria?
for β-oxidation
- need to enter the oxidative cycle
β-oxidation
- multiple steps
- fatty acid molecules are broken down to produce energy
- consists in breaking down long fatty acids that have been converted to acyl-CoA chains into progressively smaller fatty acyl-CoA chains
- takes place inside mitochondria
complete oxidation of palmitic acid
7xFADH2 + 7xNADH + 8xAcetyl-CoA
-> all enters the krebs cycle
ATP yield of triglycerides with 3 palmitic acids
387 ATP
16 carbon palmitic acid
- saturated long-chain fatty acid with a 16-carbon backbone
- undergoes 7 cylces of β-oxidation
how to train your body to use more fat?
- higher fat in diet
- to help utilise it more readily when you exercise
daily recommended energy requirements
2111kcal for men
1613kcal for women
aerobic characteristics
- higher capillary density
- greater size and number of mitochondria
metabolic responses to training
- increased ability to oxidise CHO
- increased ability to oxidise lipids
- lower respiratory exchange ratio (RER)
energy provision in an endurance event
- most aerobically
- gradual decline in speed over the race
- PCr to race speed
- anaerobic -> initial maintainance of speed & for short accelerations
- aerobic -> burning fat and carbs -> mainly depend on this
what if we run out of energy?
- rarely in top level atheletes
- mucle glycogen stores depleted
- fat oxidation cant occur without CHO ox
CHO needed for fat oxidation
- oxaloacetate accepts acetly-CoA (formed from pyruvate)
- if glycolysis not functioning (Carbs burning) -> less oxaloacetate -> cant combine to acetyl-coa
what is a protein?
- acid group/carboxyl group and amino grouo attached to a carbon atom
- R: side chian -> structure determines a.a. characteristics
- made of a.a. = building blocks
peptide bonds
- link a.a.
- dipeptide = 2 a.a
- tripeptide = 3 a.a
- polypeptide = up to 100 a.a.
essential a.a.
- cannot be formed by body
- need to be obtained through diet
- 8
non- essential a.a.
synthesised by body
12
protein in diet
- depends on geographical region & socio-economic & cultural factors
- animal protein foods = 60-70% intake in developed regions
- plant proteins = 60-80% intake in developing regions
recommended protein intake UK
= 0.75g/kg body mass
free amino acid pool
- derived from dietary amino acids and the proteolysis of body proteins
- the total amount of amino acids from the diet, protein recycling, and non-essential amino acids produced by the body that is available for metabolic processing
amino acid synthesis in body
- synthesized from intermediates in glycolysis, the citric acid cycle, or the pentose phosphate pathway.
- in the liver?
amino acids and krebs cycle
- many a.a. needed as intermediates in kc
- very important for energy production
where are a.a. used in body?
- brain
- ant.pit
- hypothalamus
- heart
- thyroid
- lungs
- liver
- stomach
- gallbladder
- GI tract
- blood
- skin
- muscle
- bone
what is protein used for?
15% of body mass = proteins
- structural & mechanical e.g. muscles
- enzymes (reactions in body)
- hormones
- antibodies
- fluid balance
- acid-base balance
- channels and pumps
- transport
nitrogen balance
- protein metabolism & utilisation is measured by examining nitrogen content
- nitrogen balance: N2 intake = N2 output
+ nitrogen balance: N2 intake > N2 output (hypertrophy)
– nitrogen balance: N2 intake < N2 output
nitrogen balance measurement
N2 intake = total protein intake x 0.16
N2 output = measure all N2 excreted (urine, faeces, gas, sweat)
factors affecting protein intake
- exercise type
- energy balance
- gender
- training status
- age
muscle hypertrophy
- an increase and growth of muscle cells
- muscles bigger due to increased protein synthesis or decreased protein degredation
-increased muscle fibre diameter - need a + protein balance
why do atheletes feel the need to take protein supplements?
- muscle recovery
- muscle hypertrophy
- increased muscle mass
what is ATP?
- energy currency of the body
what processes require ATP?
- circulation
- digestion
- glandular excretion
- muscle contraction
- nerve conduction
- tissue synthesis
what macronutrient is the most abundant and economic source of food energy in the human diet?
carbohydrates -> 40-80% of total energy in diff pop. around world
what is the krebs cycle?
- an essential reaction cycle in the body
- key component that underpins metabolism and is responsible for generating the body´s fuel
- cycle derives it´s fuel from the breakdown of fats and carbohydrates
does resistance training always cause muscle fibres to shift?
no
what type of athlete would have the higher proportion of type 2x muscle fibres?
- olympic weightlifters or sprinters
- type 2x fibre tends to be involved in sports needing short periods of high intensity speed levels
- these fibres are associated with increase / high levels of power
What is phosphocreatine? What role does it play in energy metabolism?
- PCr = substance used to create ATP when muscle ATP stores have been depeleted
- muscle ATP stores get used up very fast -> ATP must be resynthesised for muscle contraction to be sustained -> PCr used to rephosphorylate ADP back to ATP to generate energy
- PCr has a higher phosphate transfer potential than ATP (can transfer phosphate faster) to quickly produce energy after depletion
- found in skeletal muscles
how much fat is stored in adipose tissue? how are they stored?
- 90%
- stored as triglycerides (triacyglycerol) in adipose
what does the term “hitting the wall” mean?
- refers to time when body has burned up all of its glycogen stores in the muscles and the liver
- body then turns to use fat metabolism as primary source (palmitic acid)
problem with fat metabolism for energy
- produces more energy but at a lower rate & consumes more oxygen
- less efficient
is a high fat meal before period of endurance exercise beneficial for performance?
- no
- carb dense diets better
what are proteins made of? how is this diff to carbs or fats?
- made from amino acids
- amino acids have an acid group and an amino group attached to C atom
- proteins similiar to carbs but also contain Nitrogen
- proteins have R side chains -> determine proteins characteristics
how many amino acids does the body require? how many are essential & non-essential?
- 20 amino acids
- 8 (9 in infants) are essential (body can´t synthesise)
- 12 non-essentail (synthesised by body)
what % of body mass does protein account for?
15%
What important factors will you need to consider if an athlete expresses a desire to utilise protein supplements?
- nutritional personalisation & balance
- what is existing diet like? average dialy protein intake?
- level of athlete
- type of training
Many of the proteins found in mitochondria are not transcribed from mitochondrial DNA. How would you best describe the pathway of such proteins from the cytoplasm into the mitochondria?
- The protein is formed in the cytoplasm as a precursor protein
- it is then transported across the two mitochondrial membranes in a single stage
