Ex. Phys. Metabolism Flashcards
what are the substances derived from food used for growth, maintenance, and repair of tissues
carbohydrates (CHO) (4 kcal/g)
Proteins (4 kcal/g)
Lipids (Fats) (9 kcal/g)
carbohydrates
- primary role
- how is it circulated
- stored where
- stores as what
- most CHOs are…
- average person can store enough CHO to expend..
- primary role is fuel source for basic life functions and exercise
- circulated in blood as glucose
- stored in muscle, liver, and kidneys as glycogen
- most CHOs are consumed, but body can synthesize them - liver regulates the availability of glucose in the body
- an average person can store enough CHO to expend approximately 2500 kcal of energy
proteins
- primary roles
- sub-unit name
- inessential vs. essential
- stored where
- not a main fuel source, but when does it become more of one?
- primary roles are for regulatory functions, such as enzymes and transport receptors
- sub-units are call amino acids
- some AAs are inessential (the body can make them) and some are essential (must be consumed)
- stored in blood and tissues, especially the liver and muscle
- not a main fuel source, but becomes more so when CHO and lipid availability is low
lipids
- primary roles
- stored where
- most lipids are _____
- other roles
- how much energy can a lean person store int he form of lipids
- primary roles are fuel source and fuel storage
- stored in muscle and adipose tissue
- most lipids are triglycerides (glycerol + fatty acids)
- some serve other roles, such as membrane structures and hormones
- they can expend approximately 70,000 kcal of energy
fuel consumption distribution at rest
CHOs: 35%
lipids: 60%
AAs: 5%
fuel consumption during exercise
CHOs: 10-90%
lipids: 10-90%
AAs: 5-10%
energy
- how to think of it
- energy intake =
- process of energy transformation leads to
- think of energy as kinetic or potential
- energy intake = energy output + energy stored
- process of energy transformation leads to heat loss (measured in kcal)
anabolism
- definition
- requires
- building large molecules from small molecules
- requires energy
catabolism
- definition
- releases
- degrading large molecules into smaller ones
- releases energy
what are the most important metabolic reactions
breakdown and synthesis of ATP
ATP characteristics
- donates 7.3 kcal when it is split apart via hydrolysis
- accomplishes its work by donating phosphate groups via phosphorylation
- ADP and AMP receive energy from the breakdown of other molecules and can easily gain additional phosphates
- ATP turnover is 200 kg/day, but you only have a few grams available at any given time
why is creatine phosphate (CrP) not as cool as ATP
it gives off energy well, but doesn’t accept phosphates as easily
purpose of macronutrients and metabolic pathways from an ex. phys. perspective
generate sufficient ATP to conduct physical work
what are metabolic pathways controlled by
- substrate (e.g. fuel) and enzyme availability
- the energy needs of cells
- conditions like temperature and pH
Ox/redox reactions
-what are they
-what are proteins
what drives ATP synthesis
chemical reactions designed to harness the energy of protons and electrons
-protons: typically hydrogen ions (H+) that have been stripped of their electrons (e-)
H+ and e- movement within a muscle fiber drives the majority of ATP synthesis
ox/redox reactions
- reduction
- oxidation
- important ox/redox compounds
reduction -gain e- oxidation -lose e- important ox/redox compounds -NAD+/NADH/NADH + H+ -FAD/FADH2
purpose of NAD+/NADH/NADH + H+
and FAD/FADH2 reactions
transport H+ and e- for use in metabolic pathways that generate ATP w/ oxygen
purpose of metabolic pathways
generate and use ATP
three categories of energy systems
- immediate system (Phospagen or ATP-CrP systems)
- glycolytic system (glycolytic-lactic acid system)
- mitochondrial respiration (“oxidative” system)
characteristics of the above systems
- duration of ATP production/synthesis
- rate of ATP production/synthesis
- aerobic or anaerobic conditions
- where they occur in the body
- substrate source
immediate system
- namesake refers to…
- ATP and CrP stored within…
- characteristics of the reactions that break down and synthesize new ATP
- enzymatically regulated by
- ideal for
- ATP and CrP storage are…
- note about ATPase
namesake refers to rapid accessibility of ATP and CrP
-stored within muscle fiber sarcoplasm
characteristics
-rapid, simple, anaerobic, and take place in the muscle fiber sarcoplasm
enzymatically regulated by kinases (creatine kinase and myokinase) and myosin ATPase
ideal for rapid and/or ultra-intense bouts of exercise
storage are limited, therefore, rapid ATP breakdown and synthesis cannot last long
-ATPase also found on myosin heads for muscle contraction
glycolytic system (CHO metabolism)
- what provides the next fastest way to generate ATP after the immediate system?
- occurs where
- ideal for
catabolism of glucose via anaerobic pathways
occurs within the muscle fiber sarcoplasm
ideal for short-medium duration, intense exercise
glycogenolysis
- purpose
- enzymatically regulated by
purpose is to break down glycogen into glucose-6 phosphate (G6P), which can be used later on in glycolysis
enzymatically regulated by glycogen phosphorylase
glycogenolysis note
not an energy-yielding pathway
it just preps glucose for glycolysis
is often not considered as part of the glycolytic system
highly linked with glycolysis
glycolysis
- purpose
- what will hopefully happen to some of the products
- enzymatically regulated by
purpose
-break down glycogen into pyruvate, while providing ATP rapidly for intense exercise
some products will hopefully be transferred to other metabolic pathways to generate additional ATP later on
enzymatically regulated by kinases (hexokinase and phosphofructokinase)
glycolysis note
this is the first energy-yielding metabolic pathway encountered by glucose or G6P
products of glycolysis
- -2 ATP to activate pathway (only uses 1 ATP if G6P is generated from glycogenolysis
- +4 ATP (2 for each GA3P molecule)
- +2 NADH + H+
- +2 pyruvate
what stimulates glycolytic activity?
AMP
mechanoreceptors stimulated by muscle receptors
function of kinases
add a phosphate
fate of pyrovate
- during LIGHTER intensity exercise
- -is this good or bad
pyruvate and NADH + H+ are shuttled into the mitochondria for aerobic metabolism
-this is usually good, because H+ ions are acidic and removal from the sarcoplasm helps maintain a neutral pH within the muscle fiber
during the shuttling process, what happens to pyruvate
pyruvate is converted to Acetyl-CoA but creates an additional NADH + H+
what enzyme catalyzes the pyruvate-Acetyl-CoA conversion
Pyruvate Dehydrogenase Complex
in this circumstance, what is glycolysis sometimes referred to as
slow or aerobic
products of pyruvate conversion to Acetyl-CoA
+2 NADH + H+ (1 for each pyruvate molecule)
+2 Acetyl-CpA (1 for each pyruvate molecule)
+2 CO2 (1 for each pyruvate molecule
fate of pyruvate during HIGH intensity exercise
-is this good or bad
the NADH + H+ produced during glycolysis reduces pyruvate to lactate
-this is usually bad, because H+ ions are acidic and still in the sarcoplasm, which decreases the pH within a muscle fiber
why is decreasing the pH in the muscle fiber bad
the acidity shuts down anaerobic metabolic pathways and stimulates free nerve endings causing muscular “burn”
in this circumstance, what is glycolysis sometimes referred to as?
fast or anaerobic
products of pyruvate conversiton to lactate
+2 NAD+ (1 for each pyruvate molecule)
+2 lactate (1 for each pyruvate molecule)
what can happen to lactate?
-how should it be viewed?
can be “shuttled” into the mitochondria within the same muscle fiber, or “shuttled” out to adjacent muscle fibers, other muscles, and the liver via blood circulation to be converted into new glucose (via gluconeogenesis/the Cori cycle)
-lactate may actually be considered a friend, not a foe to exercise performance
lactate threshold practical note
the term “lactate threshold” refers to the shuttling of lactate out of a muscle fiber as quickly as it is produced
when lactate threshold is passed, lactate and H+ accumulate within the sarcoplasm and muscular fatigue/pain increase
mitochondrial respiration
- when is it used
- what does it do?
- when do we often use it?
when exercise is sustained beyond the immediate and glycolytic pathways abilities’ to synthesize ATP and/or exercise intensity is low enough to not rely on those pathways
- becomes the primary source for ATP synthesis
- this is the primary system we rely on 24 hrs/day to keep us alive
mitochondrial pathways
Kreb’s cycle (aka “the citric acid (TCA) cycle”
electron transport system (ETC)
oxidative phosphorylation (OP)
what do these steps do?
-fortunately…
slow down ATP production and reduce exercise intensity
fortunately, the capacity to generate ATP via mitochondrial respiration is huge
therefore, mitochondrial respiration can provide energy for extended periods of exercise
Kreb’s cycle
-purpose
-series of steps result in…
enzymatically regulated by
purpose
-extend the energy potential of a glucose molecule (which was converted into 2 pyruvate, then hopefully into 2 acetyl-CoA) in aerobic conditions
series of steps result in production of ATP and more “good” molecules (NADH + H+ and FADH2) that can be used in ETC/OP to generate ATP
enzymatically regulated by dehydrogenases (especially isocitrate dehydrogenase)
products of Kreb’s cycle (from 2 acetyl-CoA from glycolysis
+2 ATP (1 during each cycle)
+2 FADH2 (1 during each cycle)
+6 NADH + H+ (3 during each cycle)
electron transport chain/oxidative phosphorylation
- purpose
- where does it occur
purpose
-finally harness the energy potential of the NADH + H+ and FADH2 compounds to produce gobs of ATP using oxygen
where
-chain of cytochromes found within inner membrane cristae of mitochondria that accept protons from NADH + H+ and FADH2
electron transport chain/oxidative phosphorylation
-process involving electrons and H+
- e- are stripped from H+, then passed down chain via specific carriers
- H+ are pumped out of matrix via power from e- flow, creating an electrochemical gradient (potential energy)
- e- are finally trapped by O2 and combine with additional H+ to form H2O
- H+ pumped into inter-membrane space re-enter the matrix due to electrochemical gradient
- H+ re-entry release energy (kinetic energy) to put a Pi on ADP to form ATP
products of ETC/OP
6 ATP from 2 NADH + H+ (derived via glycolysis)
6 ATP from 2 NADH + H+ (derived via pyruvate conversion to Acetyl-CoA)
4 ATP from 2 FADH2 (derived via Kreb’s cycle)
18 ATP from 6 NADH + H+ (derived via Kreb’s cycle)
final ATP summary from the breakdown of a single glucose mulecule using mitochondrial respiration
glycolysis: +2 ATP
Kreb’s cycle: +2 ATP
ETC/OP: +34 ATP
TOTAL: 38 ATP
summary note
if glucose comes from glycogenolysis, an additional ATP is saved, thereby bringing total production up to 39 ATP
practical note
the term oxygen consumption (VO2) is used to describe how much O2 is used (consumed) for mitochondrial respiration at any moment at time.
the measurement is typically expressed as an absolute rate, i.e. liters of O2 consumed per minute or as a relative rate, i.e. mL O2 consumed per minute per kg of bodyweight
lipid metabolism types
lipolysis and translocation
B-oxidation
lipolysis and translocation
- occurs where
- _____ is degraded to _____
- what degrades it
- what allows FFA to enter muscle fiber
- how are FFA activated
- where is this converted molecule taken
- occurs in adipose tissue and within a muscle fiber
- degrades triglycerides into free fatty acids (FFA)
- hormone sensitive lipase degrades it
- capillary lipoprotein lipase allows FFA to enter muscle fiber
- FFA are activated via conversion to fatty Acyl-CoA (requires 2 ATP)
- fatty acyl-CoA are translocated into mitochondria
B-oxidation
- fatty acyl-CoA produces…
- number of cycles is determined by…
- in nature, most fatty acyl-CoA are…
- what is the remaining molecule
- enzymatically regulated by
- fatty acyl-CoA produces 1 acetyl-CoA, 1 NADH + H+, and 1 FADH2 for each “cycle” through B-oxidation
- number of cycles is determined by [# of carbons in FA-CoA/2] - 1
- in nature, most fatty acyl-CoA are even-numbered chains, such as 16, 18, 20, 22 etc.
- remaining molecule is acetyl-CoA
- enzymatically regulated by B-ketothiolase
the ATP potential for a 20-carbon Fatty Acyl-CoA after going through B-oxidation and mitochondrial respiration would be
Initial FFA activation - -2 ATP B-Oxidation -9 FADH2: +18 ATP -9 NADH + H+: +27 ATP mitochondrial respiration -10 Acetyl-CoA: +10 ATP -10 FADH2: +20 ATP -30 NADH + H+: +90 ATP Total -163 ATP
when are amino acids used for ATP generation
when there is an excess supply for protein synthesis, although their contribution to ATP formation is typically minimal
in CHO-deprived states, such as stravation or extended exercise
what must happen to an AA to be used for ATP generation
must have the amine group removed via the urea cycle (deamination)
what happens to remaining carbon skeletons after deamination
converted to common intermediates, such as tryptophan, that can be metabolized in other pathways
ATP yield from AAs depends on
depends on the AA and where it enters the metabolic pathways
what are hormones
chemical messengers that can signal various tissues to mobilize or store nutrients
in general, what elicits hormonal responses
meals elicit hormonal responses that initiate fuel storage
exercise elicits hormonal responses that initiate fuel metabolism
what influences hormonal responses during and following exercise
intensity
duration
major hormones that relate to exercise
insulin glucagon epinephrine norepinephrine cortisol growth hormone insulin-like growth factor-1
insulin primary roles
stimulates liver, muscle, and fat cells to clear glucose from blood to mobilize for fuel (e.g. lower blood glucose levels) and stimulates protein synthesis and lipogenesis
glucagon
- primary roles
- when CHO availability is low
roles
-stimulates glycogenolysis (G6P) in the liver to mobilize glucose for fuel
-lipolysis in adipocytes to mobilize FFA
-deamination to mobilize AAs
when CHO availability is low, glucagon also stimulates gluconeogenesis in the liver to form new glucose
epinephrine
-primary roles
stimulates glycogenolysis in the muscles and liver to mobilize glucose for fuel
stimulates lipolysis in adipocytes and muscles to mobilize FFA
norepinephrine
-primary roles
stimulates lipolysis in adipocytes and muscles to mobilize FFA
cortisol
- primary roles
- what does cortisol do when CHO availability is low
roles
-stimulates lipolysis in adipose tissue to mobilize FFA
-stimulates gluconeogenesis to form new glycogen from ketones (derived from lipolysis)
when CHO availability is low cortisol stimulates deamination to mobilize AAs
growth hormone
-primary roles
roles
- stimulates production of IGF-1 in liver to facilitate protein synthesis
- stimulates lipolysis in adipocytes to mobilize FFA
- stimulates gluconeogenesis
insulin-like growth factor-1 (IGF-1)
-primary roles
facilitates AA uptake and protein synthesis in bone and muscle
hormones vs. neurotransmitters
hormones produce larger and longer acting changes
