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119 Terms
What is energy metabolism?
The processes by which energy is supplied, transformed, directed to useful functions, and released by cells or organisms.
What is second law of thermodynamics?
A law stating that if an isolated system undergoes internal changes, the total effect is always to increase disorder.
What is an isolated system?
A portion of the material universe that does not exchange matter or energy with its surroundings.
What is energy?
The ability to maintain or increase structure within a system.
What is an open system?
A portion of the material universe that exchanges matter or energy with its surroundings.
What is chemical energy?
The energy released or required to rearrange atoms into new configurations.
What is electrical energy?
The energy a system possesses due to the separation of positive and negative electric charges.
What is mechanical (kinetic) energy?
The energy from organized movement where many molecules move simultaneously in the same direction.
What is heat (molecular kinetic energy)?
The energy from random atomic or molecular motion.
What is physiological work?
Any process performed by an animal that increases internal complexity and organization within the body.
What is high-grade energy?
Forms of energy that can perform physiological work.
What is low-grade energy?
Forms of energy that cannot perform physiological work.
What is the efficiency of energy transformation?
How well energy is converted from one form to another.
What is ingested energy?
The energy contained in the chemical bonds of an animal's food.
What is absorbed energy?
The chemical energy an animal absorbs from its gastrointestinal tract.
What is biosynthesis?
The biological process by which animals create necessary molecules and structures using absorbed energy.
What is maintenance?
The processes that maintain homeostasis in an animal’s body, including circulation, respiration, and tissue repair.
What is external work?
Mechanical work performed by an animal that involves applying forces to objects outside the animal's body.
What happens to energy over time?
Over time. energy decreases unless new energy is added.
Which biomolecule contains the most energy per gram?
Fat contains more energy per gram compared to other biomolecules.
Why do animals need energy?
Animals need energy to create and maintain homeostasis.
What forms of energy exist?
Energy exists in various forms
Chemical energy
Electric energy
Mechanical energy
Heat energy
What does energy do?
All energy can perform work, but in animals, the different forms can perform work with varying efficiency.
In this context, work refers to physiological work.
Chemical energy is totipotent, meaning "can do everything."
Electrical and mechanical energy can perform certain types of physiological work.
Heat cannot perform any type of physiological work.
What happens to energy when it’s transformed?
Some energy is degraded to heat when high-grade energy is transformed to another form of high-grade energy.
Energy transformation is therefore always inefficient
What does animals use absorbed energy for?
Animals use absorbed energy for three major functions:
Biosynthesis
Maintenance of homeostasis
External work
The absorbed energy in animals is used to export chemical energy, heat, and mechanical energy for external work.
Energy is consumed and absorbed by an animal in the form of chemical energy and is released as heat energy, chemical energy, and external work.
What is consumed energy?
Energy that was in the form of high-grade energy but has been converted to heat.
What is metabolic rate?
An animal's rate of energy consumption, the rate at which an animal converts chemical energy into heat and external work.
What is calorie (cal)?
A common unit of energy; 1 cal is the amount of heat required to raise the temperature of 1 gram of water by 1°C.
What is joule (J)?
A unit of energy used in the SI system; 1 cal = 4.186 J.
What is watt (W)?
A unit of power, the amount of energy converted into another form per unit of time, e.g., 1 J/second.
What is direct calorimetry?
Measurement of the metabolic rate by quantifying heat and external work.
What is indirect calorimetry?
Measurement of the metabolic rate by assessing factors other than heat and external work, such as O₂ consumption.
What is respiratory quotient (RQ)?
A measure used to quantify the amount of carbon dioxide produced and the amount of oxygen consumed during metabolism.
What is respirometry?
The measurement of an animal's gas exchange with the environment.
Why is metabolic rate important?
Metabolic rate is important for three main reasons:
An animal's metabolic rate is one of the key factors in determining how much food the animal needs to consume.
An animal's metabolic rate roughly represents the intensity of the animal's life.
Ecologically, an animal's metabolic rate measures the burden the animal places on the physiologically usable energy resources in its ecosystem.
Which biomolecule is the best form of energy to extract the most energy per unit of O2?
Carbohydrates are the best form of energy for an animal to consume if it needs to extract the most energy per unit of O₂.
How is the respiratory quotient(RQ) calculated?
The respiratory quotient is the ratio of produced CO2 divided by consumed O2 per unit of time, measured at the gas exchange organ.
What is the most common way to measure metabolic
The amount of consumed O2 is the most common measure of metabolic rate.
What is basal metabolic rate (BMR)?
A standardized measure of metabolic rate applicable to homeothermic animals, meaning animals that physiologically regulate their body temperature, such as mammals and birds.
BMR is the animal's metabolic rate when the animal is in its thermoneutral zone, when the animal is fasting, or when the animal is resting/sleeping.
"Fasting" means that the SDA from the last meal has ended.
What is standard metabolic rate (SMR)?
A standardized measure of metabolic rate applicable to ectothermic (poikilothermic) animals, meaning animals that allow their body temperature to vary freely with changes in the surrounding temperature, such as amphibians, mollusks, and most fish.
SMR is the animal's metabolic rate when the animal is fasting or resting/sleeping.
"Fasting" means that the SDA from the last meal has ended.
What is specific dynamic action (SDA)?
An increase in an animal's metabolic rate caused by the processing of consumed food.
What is aerobic metabolism?
Metabolic processes that require oxygen to produce ATP.
What is anaerobic metabolism?
Metabolic processes that do not require oxygen to produce ATP.
What does each animal cell possess?
Each animal cell possesses aerobic catabolic pathways.
What can aerobic catabolic pathways do?
Aerobic catabolic pathways can, by use of O2, completely oxidize foodstuff molecules to CO2 and H2O and capture in ATP-bonds much of the chemical energy that is released.
What is glycolysis?
A series of enzymatically catalyzed reactions where glucose is converted into pyruvic acid.
Occurs in the cytosol
Each molecule of glucose is converted into two molecules of pyruvic acid
Two molecules of NAD are reduced to NADH2 per molecule of glucose catabolized
Two molecules of ATP are used for and four are formed for each glucose processed, providing a net yield of two ATP molecules per glucose molecule
What is citric acid cycle (Krebs Cycle)?
A cyclic series of enzymatically catalyzed reactions that oxidize pyruvic acid to CO₂.
The six carbons of each glucose molecule catabolized emerge in the form of six molecules of CO2 as the pyruvic acid molecules produced by glycolysis are processed
The CO2 is formed by decarboxylation reactions
For each glucose molecule catabolized, eight molecules of NADH2 and two molecules of FADH2 is produced in the cycle
One molecule of ATP is generated for each molecule of pyruvic processed
What is electron-transport chain?
A series of compounds in the mitochondria, each compound capable of reversible oxidation and reduction, that passes electrons removed from food molecules to O2, capturing released energy for use in producing ATP.
First step in ATP-production that uses O2
Consists of four major protein complexes (I-IV) located in the inner membrane of the mitochondria
Takes electrons from NADH and FADH, and passes them in sequence from one compound to the next in a series of reductions and oxidations
Last step, complex IV, passes electrons with H+ -ions to oxygen, reducing O2 to water
What is oxidative phosphorylation?
The process of forming ATP from ADP using energy released in the electron-transport chain.
A common mode of expressing the efficiency of ATP production by oxidative phosphorylation is as a P/O ratio (P = phosphate, O = oxygen), defined to be the number of ATP molecules formed per atom of oxygen reduced to water.
What happens when there is complete O2 deficiency?
Without O2, electrons entering the electron-trasport (E-T) chain cannot be discharged at the end by the reduction of O2.
Because of that the E-T chain is a dead end for electrons which leads to cytochromes and other parts of the E-T chain become fully reduced.
As a consequence oxidative phosphorylation can’t take place and E-T chain is not reoxidizing molecules from Krebs cycle which leads to cell supply of NAD and FAD is threatened which leads to zero ATP production
What is redox balance?
A state in which a cell has the capability to remove electrons from a compound that undergoes reversible reduction and oxidation as fast as electrons are added to the compound
To make ATP without O2, a cell must possess alternative mechanisms that will permit redox balance to be maintained while at least some ATP-generating reactions continue to take place.
Some tissues have evolved to make ATP at significant rate without O2, mammalian brain is not one of them; succumbs rapidly when O2 is denied.
How can vertebrate skeletal tissue transfer energy?
Vertebrate skeletal tissue and many others use substrate-level phosphorylation of glycolysis to transfer energy from glucose to ATP in absence of O2. Tissue must have way of maintaining redox balance for NAD without O2, since NAD is needed as immediate electron acceptor.
What is anaerobic glycolysis?
A process where NADH2 is reoxidized to NAD by passing electrons to pyruvic acid, turning the latter into lactic acid. The pyruvic acid is used as final electron acceptor
Enzyme lactate dehydrogenase (LHD) needs to be present for a cell to carry out this process
LHD catalyzes reduction of pyruvic acid. A cell with appropriate amounts of types of LHD can convert every NADH2 it forms back to NAD without O2
Glucose and glycogen are the only food molecules used as fuel in this process
Only 2 ATP molecules per glucose molecule catabolized
What happens to the catabolic end products?
CO2 and H in aerobic catabolism. Usually disposed as CO2 by exhaling, and the H as H2O.
Organic compounds far from fully oxidized and posses further potential to yield energy, in anaerobic catabolism.
Great to save for further energy production, but harmful in higher concentrations. Animals with only short-term anaerobic catabolism more likely to be able to retain all the end-product molecules without too much harm.
Ultimately get rid of lactic acid metabolically by transforming back to pyruvic acid. However, that is an oxidation reaction, so can only take place when O2 is present again. After conversion to pyruvic acid, carbon chains of lactic acid go through one of two paths – both require O2.
Tissues that are well supplied with O2 can metabolize lactic acid made by other tissues that are deprived of O2; this can occur even while lactic acid production continues.
What are the requirements for a steady ATP-production
Four requirements to be classified as steady:
ATP produced as fast as it is used
Uses raw materials no faster than they are replenished
Chemical by-products voided as fast as they are made
Does not cause cell disruption
If steady cell remains homeostatic
Aerobic usually steady, anaerobic usually unsteady.
Aerobic catabolism can draw its O2 from preexisting stores of O2 in a cell or tissue – this makes it unsteady! Muscle cells often have O2 stores because they comtain myoglobin (type of hemoglobin).
What is phosphagen?
Compounds that serve as temporary stores of high-energy phosphate bonds.
Provide an additional mechanism of ATP production without O2.
Creatine phosphate is phosphagen that occurs in skeletal muscles in vertebrates, arginine phosphate in invertebrates.
What is the interplay of aerobic and anaerobic catabolism during exercise?
Behavior and biochemistry are linked during physical activity because attributes of performance depend on how the ATP for muscular effort is synthesized.
Submaximal forms of exercise can be supported entirely (except during transition phases) by aerobic catabolism using O2 taken in from the environment by breathing.
An oxygen deficit occurs at the start of exercise, pay-as-you-go-phase in the middle, and excess postexercise oxygen consumption (EPOC) occurs at the end.
As the duration of all-out exertion increases, ATP must increasingly be supplied by steady-state aerobic catabolism, rather than by nonsteady-state mechanisms that can produce ATP exceptionally rapidly but cannot produce a great deal of it.
Individual differences are a fact.
What is impaired O2 influx?
Decreased availability of oxygen
Can occur if O2 in environment is low or environment isn’t breathable ex under water
What is the difference between hypoxia and anoxia?
Hypoxia
Especially low level of O2
Anoxia
Absence of O2
Some tissues may experience this during impaired O2 influx
Anaerobic catabolism in anoxia and sometimes in hypoxia
What is metabolic depression?
A reduction of ATP-needs below normal, but above immediate physiological threat to life, during impaired O₂ influx.
Animals that is less active/in hibernation during winter use this to save energy and only focus on keeping warm.
When diving for long periods of time, mammals and birds subdivides their bodies. They always prioritize O2 to the brain and deprive large portions of their bodies of O2, these parts depend on anaerobic glycolysis.
What is oxygen regulation?
Maintenance of steady O₂ consumption and ATP production in environments with lowered O₂ levels.
Usual pattern – Animals O2 consumption unaffected over certain range of O2 levels. Often involves increased breathing.
Seem to evolved in parallel with habitat selection
How do the different locomotion differ in their efficiency?
Efficiency of locomotion from (least) running/walking, flying, swimming (most).
Underwater swimming more efficient than surface.
Swimming not primary locomotion for those species
Fish are the most efficient at underwater swimming. Aquatic mammals and sea turtles are not as efficient because they are not as streamlined.
Running/walking has a linear relationship for O2 consumption (which is tied to energy expenditure) and distance travelled.
Flying has a U-shaped curve
Quite a bit of variation due to morphology, environment etc.
Swimming has a J-shaped power function
How does the mode of locomotion primarily influence the minimum cost of transport for animals of a given body size?
Among animals engaged in their primary form of locomotion, the minimum cost of transport displayed by a species of given body size typically depends principally on the species’ mode of locomotion rather than its clade (phylogenetic position) or the details of its locomotor mechanisms.
Among animals that share a single primary mode of locomotion, large-bodied species cover distance at considerably lower weight specific cost than small-bodied species do.
In what ways do metabolic rate relationships with speed differ among running mammals, swimming fish, and animals engaged in flapping flight?
When a mammal or other animal runs, its metabolic rate typically increases linearly with its speed. Metabolic rate and speed are related by a J-shaped power function in swimming fish. For animals engaged in flapping flight, metabolic rate is expected to exhibit a U-shaped relation to speed, but this theoretical expectation is not always observed in real animals.
What speed minimizes the cost of transport and maximizes the distance an animal can travel with a given amount of energy?
Cost of transport is the energy cost of covering a unit of distance. The speed that minimizes the cost of transport is the speed that maximizes the distance that can be traveled with a given amount of energy.
What is VO2 max?
Aerobic capacity or maximum aerobic power
Can only be maintained for a few minutes
Determines the peak rate at which an animal can synthesize ATP by aerobic catabolism
Unclear what is limiting
An organ (circulatory system?) limits, other could go higher
All organs are equally unable: symmorphosis
Variation between species and individuals in one species
What is aerobic scope for activity?
The difference (-) between its VO2max at that temperature and its resting rate of O2 consumption at the same temperature.
What is aerobic expansibility?
The ratio of its VO2max over (/) its resting rate of O2 consumption.
What is average daily metabolic rate (ADMR)?
Amount of energy an animal expends in a day
Usually measured by doubly labelled water
What is the difference between a endotherm and an ectotherm?
Endotherm: Produce heat from the inside the body and can keep a stable temperature
Ectotherm: Gets heat from the environment
What is the meaning of homeothermy?
An animal that thermoregulates by physiological means (rather than simply by behavior). Protects mammals and birds from extreme external thermal conditions.
What is behavioral fevers?
Happens in ectothermic animals where the fever makes them search for warmer environments to get well/survive
Where does the detection of body temperature in a mammal or bird happen?
Occurs in multiple parts of the body; thermosensitive neurons of importance are found in the skin, spinal cord, and brain, and sometimes also in specialized locations such as the scrotum.
What is pilomotor responses?
Each hair can be held upright or allowed to lie flat against the skin by the contraction or relaxation of a tiny muscle at its base, under control of the sympathetic nervous system in mammals.
What is ptilomotor responses?
Each feather can be held upright or allowed to lie flat against the skin by the contraction or relaxation of a tiny muscle at its base, under control of the sympathetic nervous system in birds
What is vasomotor responses?
In blood vessels responses that alter the rate of blood flow to the skin surface and other superficial parts of the body.
Vasoconstriction (shrinking)
Vasodilation (expansion)
What is postural responses?
Alters the amount of body surface area directly exposed to ambient conditions.
Ex: At low ambient temperatures, for example, mammals often curl up, and some birds tuck their heads under their body feathers or squat so as to enclose their legs in their ventral plumage. Many birds hold their wings away from their bodies when ambient temperatures are high.
What is thermogenic mechanisms?
Specialized mechanisms to generate heat in mammals and birds, ex shivering
What is shivering?
Unsynchronized contraction and relaxation of skeletal muscle motor units in high-frequency rhythms, mediated by motor neurons (nerve cells) of the somatic nervous system.
Generates metabolic heat
Deliberate movement, such as jumping up and down, generates heat the same way
What is nonshivering thermogenesis(NST)?
The process in which brown fat, with its ability to release energy from fuel molecules directly as heat, is used to increase metabolic heat
Ex in lab rats, when they were living in warm temperatures and then transferred to a room at 6 C, they shiver violently during their first days there.
What is brown adipose tissue(BAT)?
A metabolically active form of adipose tissue, known only in mammals, that serves as the primary site of mammalian nonshivering thermogenesis and expresses a distinctive mitochondrial protein, uncoupling protein 1 (UCP1).
What is Uncoupling protein 1 (UCP1, Thermogenin)?
A protein that mediates the heat production in BAT
What is the lowest a footpad cools, even when exposed to extreme cold?
If they are in contact with much cooler substrates ((-30) -(-50) C), the footpads don’t cool any further than 0 C. The footpads, therefore, are thermoregulated at the lowest temperature that does not subject them to a risk of frostbite!
What is countercurrent heat exchange?
A mechanism that transfers heat between two fluid streams flowing in opposite directions.
Such heat exchange depends on the transfer of heat between two closely juxtaposed fluid streams flowing in opposite directions (counter = “opposite”; current = “flow”).
What is rete mirabile?
A complex network of tiny vessels
What is an example of behavioral defenses?
Ex desert rodents for instance, construct burrows, which they occupy during the day and most emerge on the desert surface only at night. They thus evade the extremes of heat loading that could occur in deserts.
What is an example of insulatory defenses?
For example, some species of large, diurnal mammals and birds native to hot, arid regions have evolved strikingly thick pelages and plumages.
How can body temperature be a defense?
Both high-amplitude cycling of body temperature and profound hyperthermia can act as defenses and in fact are commonly employed as water-conservation mechanisms by species adapted to hot environments.
Hyperthermia
A controlled increase in body temperature used as a water-conserving mechanism in hot environments.
Many mammals and birds employ controlled, profound hyperthermia as a principal nonevaporative water-conserving mechanism for coping with hot environments
What is sweating?
A fluid called sweat is secreted, by way of the ducts of sweat glands, through the epidermis of the skin onto the skin surface. Even when an animal is not sweating, water loss occurs through the substance of the skin but typically at a low rate.
Sweat is not pure water but instead is a saline solution. Concentrations of Na+ and Cl– in sweat are lower than in the blood plasma, and during acclimation to hot conditions the salinity of sweat becomes reduced.
What is panting?
An increase in the rate of breathing in response to heat stress. Panting increases the rate of evaporative cooling because water evaporates from the warm, moist membranes lining the respiratory tract into the air that is breathed in and out.
What is gular fluttering?
Rapidly vibrating their gular area (the floor of the buccal cavity) while holding their mouth open.
Gular fluttering shares certain positive attributes with panting: It creates a vigorous, forced flow of air across evaporative surfaces and does not entail salt losses.
Unlike panting, gular fluttering cannot induce severe alkalosis, because it enhances only oral airflow, and CO2 is not exchanged between air and blood across oral membranes.
What are the three major chronic responses to winter for mammal and birds?
Acclimatization of peak metabolic rate: When a mammal or bird exhibits this response, it increases the maximum rate at which it can produce heat by sustained, aerobic catabolism
Acclimatization of metabolic endurance: meaning an increase in the length of time that a high rate of metabolic heat production can be maintained. Although current evidence indicates that this sort of acclimatization is common, little is known about its mechanisms.
Insulatory acclimatization: an increase in the animal’s insulation, I (resistance to dry heat loss), at ambient temperatures below thermoneutrality.
What is controlled hypothermia?
The state of having an unusually low body temperature, and in the cases we are discussing, it is “controlled” because the animals orchestrate their entry into and exit from hypothermia rather than being forced
What are some examples of controlled hypothermia?
Hibernation:
When an animal allows its body temperature to fall close to ambient temperature for periods of several days or longer during winter.
Estivation:
When an animal allows its body temperature to fall close to ambient temperature for periods of several days or longer during summer
Daily torpor:
When an animal permits its body temperature to fall close to ambient temperature for only part of each day (generally on many consecutive days) in any season. Is typically timed by the circadian clock
What advantage does temporal heterotherms have?
They are in essence able to switch back and forth between two very different thermal worlds at different times.
What is the meaning of arousal?
Emergence from hibernation and the process of rewarming the body by metabolic heat production.
The animals do not require outside warming to return to homeothermy. Instead, they are in control:
They return to homeothermy on their own by employing intense shivering and, in mammals, intense nonshivering thermogenesis to warm their tissues.
How does the billfish heat up portions of the extraocular eye muscles?
Current evidence suggests that they produce heat at a high rate by a "futile cycle" of Ca2+ pumping: ATP is used to transport Ca2+ actively from one intracellular compartment to another, and then the Ca2+ leaks back to where it started, where once again ATP is used to pump it; the principal net result is breakdown of ATP at a high rate to release heat. This help the fishes in their pursuit of prey because the tissues are kept from becoming cold when the fish swim through cold water.
What is a countercurrent vascular?
Array that short-circuits outflow of heat from a tissue—thereby preventing the heat from reaching the gills—is required for the tissue to be endothermic.
What does it mean with ordinary metabolic heat production?
The source of heat for endothermy in all cases except the billfish, which have specialized "heater" tissues derived from extraocular eye muscles.
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