metabolism Flashcards
Metabolism
the sum total of all the chemical
reactions occurring in an organism
Remember the 2nd law of thermodynamics
– In a closed system the direction of change is
toward disorder
– Animals are an open system
* They require energy to maintain order in
their bodies
Two Metabolic pathways
anabolic and catabolic
Anabolic
– Assembling of substances into complex
molecules
– Requires energy
– Net incorporation of N-containing molecules by
protein synthesis
Catabolic
– Breakdown of complex energy-rich materials
into simpler molecules
– Releases chemical energy
– Some energy stored as ATP or glucose
Three forms of energy
– Chemical
* Freed/needed for atom reconfiguration
– Electrical
* Charge separation of molecules
– Motional
* Mechanical
– Energy of organized motion
* Heat
– Formed by random motion of all molecules
Work and Physiological work
- Work- the transfer of energy from one source
to another - Physiological work- any process carried out by
an animal (or plant) that increases order in the
environment (internal and external)
– Breakdown of molecules
– Bodily movements - Heat generation is NOT physiological work
Heat
- Can only convert heat to work if there is a temperature
discrepancy within the system- Internal combustion engine propels a car
- Heat is important to organisms and MR
- Energy forms and heat
– High-grade energy- can perform phys. work
* Chemical, electrical, mechanical
– Low-grade energy- cannot perform phys. work
* Heat
* Degrade energy when convert from high to low
Animal energy use
- Ingested energy- chemical bonds of food
– Food unable to be digested- Fecal energy
– Food assimilated into body- Absorbed energy - Absorbed energy has 3 routes
– Biosynthesis
– Maintenance
– External work
note to self, study what is happening on the uses of energy by an animal image
page 2 slide 3 on page
Biosynthesis
- Synthesis of body proteins and lipids
– Accumulation of chemical energy in body
tissues- during growth
– Also during fat storage
– Eventually eaten or die (decompose) - Some synthesized chemicals are exported
– Gametes, milk, excreted mucus, skin, hair, etc. - Some energy lost as heat
Maintenance
- Maintain integrity of the organism as a whole
– Internal work- Circulation, respiration, gut motility, etc.
- Very costly to the organism
– Almost all of the high-grade energy is degraded
to heat
– Every step of ATP use causes additional
degradation
External work
- Mechanical work performed outside the body
– Necessary events to be biologically successful- Food, sex, and practicing for both!
- Some of this energy is degraded to heat (ATP)
- Some is transferred outside of the body where
it ultimately finds the same fate
– Resistance to motion (heat)
– Potential energy followed by resistance (heat)
All animals create heat
- Think about the diagram
– Most of the absorbed energy becomes heat
– Are endothermic organisms unique? - The pathway is one-way
– Not possible to convert heat into high-grade
energy
– Energy is not recycled
* Explains why animals require continued
consumption throughout their lives - Collective heat from all organisms radiates into space
Metabolic rate
– Conversion of chemical energy into heat
– Expressed as heat energy released per unit
time, rate of heat production
– Determines how much food is needed
– Representative of an animal’s lifestyle/intensity
– Measures an organism’s drain on the
ecosystem by degradation of chemical energy
