# data[].attributes.body
All living systems require constant input of free energy.

All organisms require constant energy input to maintain organization, to grow and to reproduce.

Free energy is required for living systems to maintain organization, to grow or to reproduce, but multiple strategies exist in different living systems.

Changes in free energy availability affect organisms, populations and ecosystems. Especially changes in the producer level that can have drastic effects on the ecosystem and species.

# data[].attributes.headline
Capture and storage of free energy (cont.)

# data[].attributes.subject
Capture and storage of free energy (cont.)

# data[].attributes.body
Catabolic Pathways yield energy by oxidizing organic fuels. The breakdown of organic molecules is exergonic.

# data[].attributes.body
Autotrophs capture free energy from physical sources in the environment.

Heterotrophs capture free energy present in carbon compounds produced by other organisms.

# data[].attributes.body
Changes in free energy availability can result in changes in population size and disruption to an ecosystem:

Change in the producer level can affect the number and size of other trophic levels.

Change in energy resource levels such as sunlight can affect the number and size of the trophic levels.

Each food chain in a food web is usually only a few links long. Two hypotheses attempt to explain food chain length: the energetic hypothesis and the dynamic stability hypothesis.

The energetic hypothesis suggests that length is limited by inefficient energy transfer. (more supported

The dynamic stability hypothesis proposes that long food chains are less stable than short ones.

Population fluctuations at lower trophic levels are generally magnified at higher levels. Any loss of producers within the food chain affects the consumers.

# data[].attributes.body
There is a relationship between metabolic rate per unit body mass and the size of multicellular organisms – generally, the smaller the organism, the higher the metabolic rate. This is because larger animals have more body mass so they require more chemical energy. However when comparing the metabolic rate per unit of body mass to body size we see that the smaller the animal the more energy cost of maintaining a stable body temperature.

Due to this a smaller animal must eat more food per unit of body mass than a larger animal

# data[].attributes.body
Reproduction varies by organism, it also takes more free energy than maintenance and growth. Examples
Humans - 9 months of pregnancy & months of breastfeeding (5-8% annual energy budget)
Penguins - Activity takes most of energy but well insulated (6% cost for egg making/incubating + food for chicks)
Deer mouse - Large amount for temp. regulation
Snake - Produces only 650g of eggs

# data[].attributes.body
Terms to know:
Metabolic rate - The amount of energy an animal uses in a unit of time.
Basal metabolic rate (BMR) - The metabolic rate of a non-growing, unstressed endotherm at rest with an empty stomach.
Standord metabolic rate (SMR) - The metabolic rate of a fasting, non-stressed ectotherm at rest at a particular temperature.
Endotherms maintain body temperatures and ectotherms depend on the environment for their body temperature.

# data[].attributes.body
Uses of free energy include

Regulating body temperature

Reproduction & rearing of offspring

Metabolism

Maintain organization

Grow

The flow of energy through an animal is it's bioenergetics. It ultimately limits the animal's behavior and how much food it needs.
Animals harvest chemical energy from the food they consume, once it goes through digestion ATP is produced for all of the cellular work.

Excess energy results in energy storage or growth.

Insufficient energy results in loss of mass, and in the end the death of the organism.

# data[].attributes.body
The metabolism transforms matter to energy by following the laws of thermodynamics.
Metabolic pathways start with specific molecules and end with specific products, each step of a metabolic pathway is catalyzed by a specific enzyme.
These pathways can be either catabolic or anabolic.

Catabolic pathways release energy by breaking down complex molecules. ex - cellular respiration, breakdown of glucose in the presence of oxygen

Anabolic pathways consume energy to build complex molecules. ex - the synthesis of protein from amino acids

# data[].attributes.body
Energy is defined as the capacity to cause change. The first law of thermodynamics is that energy can not be created or destroyed but it can be converted from one form to another. The second law states that the total entropy of the universe increases over time.

Kinetic - Motion

Heat (thermal) - Random movement of atoms/molecules

Potential - Based on location

Chemical - Release from chemical reactions

Spontaneous processes occur with no energy input and can be quick or slow. But in order for it to occur without energy it has to increase the randomness of the universe.
Energy in ecosystems comes in through light and comes out through heat. Order is maintained by coupling processes that increase entropy with ones that decease it.
In order to maintain order energy input must exceed energy output. Cells create ordered structures from less ordered ones and organisms do the opposite with matter.

# data[].attributes.body
There are a few reactions that have to deal with free energy. Exergonic ones and endergonic ones

Exergonic reactions release free energy and are spontaneous (-G)

Endergonic reactions absorb free energy and are not spontaneous (+G)

# data[].attributes.body
ATP is perfect for energy coupling which we know is using the energy of an exergonic process for an endergonic process. The energy coupling is done by using the chemical potential energy that is found in the bonds that hold ATP together.
ATP is renewable because all it takes to bring it back to ATP is the addition of a phosphate group. The energy to do this comes from catabolic reactions in the cell. Hydrolysis breaks the bonds of the ATP and then the release of energy can drive an endergonic process. This energy comes from the chemical change not from the bonds themselves

# data[].attributes.body
To tell wether a reaction occurs spontaneously or not we determine the free-energy change. Free energy, fyi is energy that can do work when temperature and pressure are uniform (in a cell).
∆G = ∆H – T∆S
Change in free energy is related to the change in enthalpy, total energy, change in entropy, and temperature in Kelvin.
Negative change of G processes are spontaneous and can perform work.
Free energy is a measure of a systems instability but during spontaneous changes free energy decreases and the stability increases. Equilibrium is when something is at it's most stable, processes can perform work when they are spontaneous and heading towards equilibrium