Chapter 5: Bioenergetics

Energy

the capacity to do work or make physical/chemical changes

synthetic work

changes in chemical bonds

• Photosynthesis

mechanical work

changes in physical location

• A cell using a flagella or cilia

concentration work

changes in concentration of the cell

• moving molecules across a membrane against a concentration gradient

electrical work

change in electrical charge leading to membrane potential

• moving ions across a membrane against an electrochemical gradient

heat

change in temperature

• namely, an increase in temperature that is useful to homeothermic animals

bioluminescence and fluorescence

producing light

• fireflies and jellyfish

phototrophs

organisms that convert light energy from the sun into chemical energy

• use pigments to capture light energy

photoautotrophs

organisms that use solar energy to make necessary carbon compounds from CO₂ during photosynthesis

• plants, algae, cyanobacteria, photosynthetic bacteria

photoheterotrophs

organisms that use solar energy to power cellular activity but get organic compounds from eating/intake

• some bacteria

chemotrophs

organisms that get energy by oxidizing chemical bonds in organic and inorganic molecules

chemoautotrophs

oxidize inorganic compounds for energy and synthesize all their organic compounds from CO₂

• some bacteria

chemoheterotrophs

organisms that eat and use chemical compounds (macromolecules) to provide energy and carbon

• All animals, protozoa, fungi, and many bacteria

thermodynamics

The principles governing energy flow

system

the part of the universe being considered

surroundings

the part of the universe not being considered

work

the use of energy to drive any process other than heat flow

the law of conservation of energy

Energy cannot be created nor destroyed, but it can change forms

• first thermodynamic law

endothermic

a reaction where heat is absorbed

• change in H is positive

• Ex: an ice cube melting

exothermic

a reaction where heat is released

• change in H is negative

• Ex: Water freezing

the law of thermodynamic spontaneity

energy transfer or changes increases the entropy of the universe

• second law

entropy

measure of randomness or disorder

• represented by S

free energy

a measure of system spontaneity

• the amount of energy that can do useful work at constant volume and pressure

• represented by G

exergonic

reactions that result in a decrease of free energy

endergonic

reactions that resulting in an increase of free energy

equilibrium constant

the ratio of product concentrations to reactant concentrations at equilibrium

• represented as K_eq