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
ALGUNAS DEFINICIONES
CALORIMETRÍA
Tasa Metabólica
Directa
BASAL
ESPECíFICA
Indirecta
ACTIVA
ESTÁNDAR
Regulación hormonal y nerviosa
TMB = aMb
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
EJERCICIO Y DEUDA DE OXÍGENO
METABOLISMO:
Carbohidratos
Monosacáridos (glucosa)
Disacáridos (sacarosa)
Polisacáridos (almidón)
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
Transporte de quilomicron
Metabolismo hepático
Control neural y hormonal
HDL y LDL
Grasas 9 cal/g – 22% peso corporal – 84% valor combustible
Proteínas 4 cal/g – 14% peso corporal – 15% valor combustible
Carbohidratos 4 cal/g – 0,77% peso corporal – 1% valor cvombustible
OBESIDAD
>20-25% CONTENIDO DE GRASA EN EL CUERPO
Hipertrófica
Hiperblástica-hipertrófica
INANICIÓN
1) Carbohidratos
2) Grasas y proteínas
3) Proteínas estructurales
ACCION DINAMICA ESPECIFICA
ACCION DINAMICA ESPECIFICA
RELACIÓN MASA-SUPERFICIE
TMB y TAMAÑO CORPORAL I
TMB y TAMAÑO CORPORAL II
TMB y TAMAÑO CORPORAL III
TMB = aMb
TAMAÑO CORPORAL Y REQUERIMIENTOS
ENERGÉTICOS
TASA METABÓLICA
ESPECÍFICA
TASA METABÓLICA ACTIVA
TEMPERATURA
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
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 or poikilotherms 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
Homeotherms and Heterotherms
Homeotherms – thermoregulate their
Tb by physiological means, e.g. the rate
of heat production, rather than
just by behaviors
- thermoregulation endotherms
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
Temperature
relations in endotherms
Thermodynamic Principles
ENVIRONMENT
Radiation
Conduction
Convection
Evaporation
ENVIRONMENT
Radiation
Conduction
Convection
HEAT GAIN
METABOLISM
Maintenance
Exercise
Growth
Lactation
Feeding
ANIMAL
HEAT LOSS
METABOLISM
Milk Removal
Fecal Removal
Urinary Removal
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
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)- energyrequiring 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