Big Idea #2 Biological Systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis

Free Energy

Energy A very difficult to define quantity The ability to do something (i.e. move) 2 general types: Potential energy- stored energy Kinetic energy – moving energy

Types of Potential Energy Gravitational Elastic Nuclear Electrical (separation of charges) Chemical (energy stored in chemical bonds)

Chemical Potential Energy

Kinetic Energy Moving objects Radiation (movement of light particles/waves) Thermal (heat, movement of particles Electrical (movement of electrons)

1st Law of Thermodynamics Energy is never created or destroyed Energy is, however, transformed from one form to another i.e. wind’s motion is converted to electricity, which is converted to heat and light energy in a light bulb

2nd Law of Thermodynamics The entropy of an isolated system is always increasing Entropy is the amount of energy in an unusable form – usually heat Systems are always losing usable forms of energy

What This Means In every conversion of energy- a lot of energy is lost as heat I.e. when you burn gas in your car- you lose a lot of energy as heat

Put Another Way Energy will be spread from areas of high energy to low energy I.e. heat will transfer from a hot pan to the air around it A moving object will lose its kinetic energy to other objects and heat Chemicals with a lot of potential energy tend to explode – releasing heat and movement of other objects

Why Do Biologists Care About This Physics Stuff? Because living things obey these laws! Living things are always losing energy to their surroundings

We Require an Energy Input For living things to remain whole they must have an energy input I.e. organisms must get energy from sun, deep thermal vents or eating

Order and Organization Require Energy Things naturally break down – to keep them from breaking down or to put them together requires an input of energy

Energy Coupling Processes that release energy are coupled to ones that require an input of energy More energy must be released than is required for the next reaction due to entropy (energy loss)

Example Flexing a muscle requires an energy input Breaking down food releases energy

Exergonic Reactions Release free energy Used in living things to provide energy for other processes

The Most Significant Exergonic Reaction ATP + H2O ADP + Pi + Energy This is the main molecule the body uses to transfer energy to where it is needed

Making ATP is an Endergonic Reaction It requires an input of energy Made in cellular respiration (input of chemical energy in food)

Uses of Free Energy Maintain body temperature (some organisms) Reproduction Growth Movement

Body Temperature Regulation Endothermy Ectothermy Use heat released by metabolic reactions to keep a stable temp I.e. humans Use external sources to try to maintain body temperature I.e. snakes/reptiles

Reproduction Requires a huge amount of energy! Many species only reproduce when energy is available I.e. most plants flower in the spring when sunlight energy is abundant

Growth Extra free energy not needed for cellular processes like movement and reproduction can be put to growth I.e. extra calories become stored fat

Energy Deprivation Mass is broken down to provide energy Eventually death will occur if there is no energy input

Smaller Organisms Require More Food Per Body Mass Smaller organisms have more surface area relative to volume, so they lose more heat So they must replenish that energy loss by eating more (relative to their body size) than larger animals do

The Trophic Levels Energy works its way up the food chain BUT at every level energy is being lost due to entropy So there is less energy available for higher levels of the food chain

Energy on an Ecological Level The more energy available for a population, the more it will grow I.e. rain forests have the most abundant plant life – constant energy source

Loss of Energy There is rarely enough energy to support more than 3-4 steps on a food chain Very little energy left for top level carnivores- part of reason these animals so often are endangered

Energy Doesn’t Cycle!!!!!!