Metabolismo

Definición de metabolismo

• Es la suma de todas las reacciones químicas que

ocurren en un organismo

• La actividad metabólica de un animal se relaciona con

su temperatura corporal ya que la velocidad de una

reacción química aumenta con la temperatura

• También se relaciona con la masa corporal

CALORIMETRÍA

Directa

Indirecta

Tasa Metabólica

BASAL

ESPECíFICA

ACTIVA

ESTÁNDAR

Regulación hormonal y nerviosa

ALGUNAS DEFINICIONES

TMB = aM b a es la ordenada al origen

M la masa corporal

b exponente empírico

Lavoisier’s direct calorimeter

• Direct calorimetry

• Used in 1780

An open respirometer

A closed respirometer

METABOLISMO:

Carbohidratos

Monosacáridos (glucosa)

Disacáridos (sacarosa)

Polisacáridos (glucógeno)

Glucogénesis y glucogenólisis en hígado

Gluconeogénesis (deaminación proteica)

Glucosa-6-P en músculo

Glucostato hipotalámico

Proteínas

Metabolismo hepático

Regulación hormonal

Grasas

Ésteres de AG con glicerol

Lipólisis / Lipogénesis

Transporte de quilomicron

Metabolismo hepático

HDL y LDL

Control neural y hormonal

COCIENTE RESPIRATORIO

C6H12O6 + 6O2 6CO2 + 6 H2O Para la glucosa: Rq = VCO2 / VO2

Rq = 1

ACCION DINAMICA ESPECIFICA

ACCION DINAMICA ESPECIFICA

TMB y TAMAÑO CORPORAL

TMb = aMb

a es la ordenada al origen

M la masa corporal

b exponente empírico

TMb = aMb = aM(b-1)

M M

log TMb = log a + b (log M)

TASA METABÓLICA

ESPECÍFICA

TMB y TAMAÑO CORPORAL

TMB = aM b

TMB y TAMAÑO CORPORAL

RELACIÓN MASA-SUPERFICIE

TMB y TAMAÑO CORPORAL I

TMB y TAMAÑO CORPORAL II

TEMPERATURA y TASA METABÓLICA

Transmisión de calor

radiación

conducción

convección

evaporación (transpiración, respiración)

HOMO vs POIQUILOTERMIA

ENDO vs EXOTERMIA

Mecanismos

termogénesis tiritante

comportamiento

grasa blanca / grasa parda

circulación

transpiración / jadeo

piloerección

control nervioso y hormonal

Heat Transfer Between Animals and

Their Environment

• Conduction: transfer of heat between objects in

contact with each other

• Convection: transfer of heat contained in a mass

of gas or liquid by the movement of that mass.

e.g wind

• Radiation: transfer of heat by electromagnetic

radiation takes place without direct contact

between objects

• Evaporation: transfer of heat by allowing water to

evaporate from moist body surface

HOMEOTERMIA y POIQUILOTERMIA

Endotherms and Ectotherms

• Endotherms- have constant body

temperature (Tb) and maintain elevated

Tb by endogenous heat production

– High VO2, high heat production, low

thermal conductivity (good insulation)

– high metabolic cost, 5x metabolism of

ectotherms

– Mammals, birds some reptiles and insects

•Ectotherms

• thermal condition outside their bodies

determine their Tb

- their Tb are high in warm environment,

but low in cool environment

- they adjust Tb by means other than

heat production and heat loss

- Low VO2, low heat production, and

poorly insulated

- fish, reptiles and amphibians

Heterotherms

• Exhibit characteristics of endotherms and ectotherms.

• Temporal heterotherms-hibernators, daily torpor in birds and mammals. Some snakes, fish, and insects.

• Regional heterotherms-usually poikilotherm that maintains a high core temperature. Eg., bumble bee.

Pigmy mouse Baiomys taylori

Thermal neutral zone

• Range of Ta in which endotherm does not

need to alter VO2 to maintain constant Tb.

• Upper critical temperature (UCT)-Ta above

which energy-requiring heat loss mechanisms

are used- sweating, panting.

• Lower critical temperature (LCT)- energy-

requiring heat production mechanisms are

used- shivering, non-shivering

thermogenesis.

Regulación en la zona termoneutral

Countercurrent Heat Exchange

• “opposite flow”

• A process that depends on a specialized

morphological arrangement of the blood vessels

carrying blood to and from appendages

• Transfer of heat between two closely

juxtaposed fluid streams flowing in opposite

directions

e.g. rete mirabile ---wonderful rete

RETE MIRABILE en el Atún

Q10

• Q10 is the rate of a reaction at a given

temperature compared to its rate 10o C

lower.

• For most reactions, Q10 is 2-3X

Acclimation

• Laboratory-induced temperature

acclimation in ectotherms.

• Acclimation in whole animals occurs

through the acclimation of individual

cells and tissues.

Supercoolants

• Glycerol, lowers freezing point.

• Antifreeze protein in antarctic fish.

• Antarctic fish are freeze intolerant, but

body fluids do not freeze.

Aclimatación en

ectotermos

Congelamiento

extracelular