Week 36 Metabolism & energetics (ch. 7-11)

Catabolic processes

Catabolic processes

Breakdown of molecules to release energy

Anabolic processes

Building new molecules at the cost of energy

Isolated system

a part of the material universe that exchanges nothing—neither matter nor energy—with its surroundings

Open system

not isolated, exchange energy or matter with surroundings

Energy

capacity to increase order

Heat

molecular kinetic energy, energy of random atomic-molecular motion

Physiological work

any process that increases order in an animal

Efficiency of energy transformation

(output of high-grade energy) / (input of high-grade energy)

Metabolic rate

rate at which animals consume energy

Respiratory quotient (RQ)

(moles of CO2 produced per unit time) / (moles of O2 consumed per unit time)

Burst exercise

sudden intense exercise

Glycolysis

• Glucose or glycogen is converted into pyruvic acid

• Occur in the cytosol

• Each molecule of glucose (6C) is converted into two molecules of pyruvic acid (3C).

• Two molecules of NAD are reduced to NADH2 per molecule of glucose catabolized.

• Two molecules of ATP are used and four are formed for each glucose processed, providing a net yield of 2 ATP per glucose molecule

Krebs cycle (citric acid cycle)

• During aerobic catabolism, pyruvic acid formed during glycolysis enters the mitochondria by facilitated diffusion (: mediated by carrier protein).

• Pyruvic acid is then oxidized in the mitochondria.

• 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 by the ________.

  • 1 pyruvic adic molecule per cycle produces 3 CO2 so 6 CO2 in total for 2 pyruvic adic molecules

• For each glucose molecule catabolized, the _______ produces eight molecules of NADH2 and two molecules of FADH2.

  • Formed from NAD and FAD which are reduced

  • Again, 2 pyruvic adic molecules per glucose molecule

• Two molecules of ATP are produced for each molecule of glucose catabolized.

Electron-transport chain (ETC)

• 4 major protein complexes (I-IV) located in the inner membranes of mitochondria

• O2 acts as the final electron receptor

  • Will not run out as it is continuously supplied to the cell and the product of reduction H2O can be pissed out, thereby carrying electrons out of the cell

Oxidative phosphorylation

• The process of forming ATP from ADP by use of energy released in the transport of electrons through the ETC

• As energy is released in electron transport, it is used to pump protons across the inner mitochondrial membrane → creates a proton elecro-chemical gradient. Protons diffuse back across the membrane toward eqilibrium through a ATP-synthesizing protein (ATP-synthase).

• In the ETC 3 complexes (I, III and IV) pump protons across the membrane.

  • Estimated that 10 protons are pumped for every for each pair of electrons that move through the whole ETC.

Anaerobic glycolysis

• Only glucose and glycogen work for fuel in most conditions

• Makes only 2 ATP per glucose molecule

• Only works in tissues that have a way of maintaining redox balance for NAD without O2.

  • Used in vertebrate skeletal muscles if O2 is too low

• Pyruvic acid is the final electron acceptor in the anaerobic cell → reduces it to lactic acid

• The main factor of whether a cell can carry out _____________ at a substantial rate is its expression of the enzyme lactate dehydrogenase (LDH), the enzyme that catalyzes reduction of pyruvic acid.

  • Creates a redox balance

Aerobic

requires O2

Anaerobic

can function without O2

P/O ratio

measures efficiency of ATP production by oxidative phosphorylation

Coupling

linkage of ETC & oxidative phosphorylation

Uncoupling protein 1 (UCP1)

Exists in the mitochondrial membrane of certain types of specialized cells. Makes it so that ETC and oxidative phosphorylation are not linked

Steady state

• a mechanism is in ___________ if

  • (1) it produces ATP as fast as ATP is used

  • (2) it uses raw materials (e.g., foodstuff molecules) no faster than they are replenished

  • (3) its chemical by-products (besides ATP) are voided (or metabolically destroyed) as fast as they are made

  • (4) it does not cause other changes in cell function that progress to the point of disrupting cell function.

• can go on indefinitely

Phosphagens

compounds that serve as temporary stores of high-energy phosphate bonds

Hypoxia

low O2 in tissues

Anoxia

No O2 in tissues

Metabolic depression

a regulated reduction in the ATP needs of the animal (or certain tissues) to levels below the needs ordinarily associated with rest

Oxygen regulation

maintenance of a steady rate of O2 consumption regardless of the level of O2 in the environment

Oxygen conformity

rate of O2 consumption falling as environmental O2 levels fall

Oxygen deficit

when the body’s supply of O2 from the environment (uptake) is less than its theoretical O2 demand for exercise.

Redox balance

the cell possesses the means to remove electrons from the compound as fast as electrons are added to it.

Maximal exercise

uses maximal rate of O2 consumption for the individual

Submaximal exercise

uses less than maximal rate of O2 consumption for the individual

Can be supported aerobically (except during transition) and can be sustained indefinitely

Supramaximal exercise

uses more than maximal rate of O2 consumption for the individual

Pay-as-you-go phase

• When, in submaximal exercise, the breathing and circulatory systems have accelerated and meet the full O2 demand of the exercise.

• All ATP is made aerobically

VO2max

aerobic capacity or maximum aerobic power

Aerobic scope for activity

the difference (-) between an animal’s VO2max at that temperature and its resting rate of O2 consumption at the same temperature

Aerobic expansibility

the ratio of an animal’s VO2max over (/) its resting rate of O2 consumption

Average daily metabolic rate (ADMR)

amount of energy an animal expends in a day

Basal metabolic rate (BMR)

base metabolism during rest in a thermoneutral environment

Endothermy

an animal’s tissues are warmed by its metabolic production of heat

Thermoregulation

maintenance of a relatively constant temperature

• behavioural (seeking heat/shade)

• physiological (sweating, shivering)

Ectotherm/poikilotherms

body temperature is determined by the environment/not elevated by metabolism

Heterothermy

difference in thermal relations from one time to another, or one body region to another, within a single individual

Homeothermy

same (or similar) temperature in whole body regulated by physiological or behavioural means

Thermoneutral zone (TNZ)

Temp at which an animal’s resting metabolic rate is independent of ambient temperature and constant

• Smaller-bodied species have a tighter ____ than larger-bodied

Lower-critical zone

lowest ambient temp in TNZ

Upper-critical zone

highest ambient temp in TNZ

Dry heat transfer

Heat transfer that does not involve the evaporation (or condensation) of water

• Proportional to the difference between the animals body temp and the temp of the environment

Thermal conductance (C)

a measure of how readily heat can move by dry heat transfer from an animal’s body into its environment

• Animals with high C need a higher metabolic rate to stay warm in a cool environment

  • Low resistance to dry heat loss (insulation)

Insulation

resistance to dry heat loss

Countercurrent heat exchange

• Requires artery and vein to be close to each other

• Allows the heat to ”short-circuit”, preserving the heat and keeping extremities cool

• Good because O2 can still get to the extremities without much heat loss

High-amplitude cycling of body heat

• Allowing the body to get cold during the night and hot during the day

• Stores some heat in the body, can later be voided by nonevaporative means

  • Using convection of cool air instead of sweating and losing water

Acclimatization of peak metabolic rate

animal increases the maximum rate at which it can produce heat by sustained, aerobic catabolism

Acclimatization of metabolic endurance

an increase in the length of time that a high rate of metabolic heat production can be maintained

Insulatory acclimatization

increase in the animal’s maximum resistance to dry heat loss (insulation)

Hypothermia

body temp below normal

Controlled hypothermia

allowing the body temperature to fall in a controlled manner under certain circumstances (ex. hibernation)

Temporal heterotherms (hibernators)

animals that can do controlled hypothermia

Arousal

process of rewarming the body after hibernation

Saturated fatty acids (SFA)

contain no carbon-carbon double bonds

Monounsaturated fatty acids (MUFAs)

contain one carbon–carbon double bond per molecule

Polyunsaturated fatty acids (PUFAs)

fat that contains two or more double bonds per molecule

• More effective hibernation (lose less weight and lower body temp)

Social hibernation

hibernating in groups

• Better survival rates as huddling increases insulation and huddling animals require less of an increase in metabolic rate than those hibernating alone or in small groups

• Synchronized arousal: waking up at the same time

  • Lowers energy costs as an animal is not pressed against a bunch of cold bodies