7.1 - What is energy

when do chemical reactions occur

when atoms have sufficient energy to combine or change their bonding partners to form new substances

energy

capacity to do work/change

forms of energy

chemical, electrical, heat, light and mechanical

chemical energy

doesn’t do work but has potential to do so e.g. energy stored in chemical bondsthat can be released during a chemical reaction.

electrical energy

separation of charges (electrical gradients), capable of doing work

heat energy

transfer due to temp differences and does work

light energy

electromagnetic radiation stored in photons

mechanical energy

energy of motion, does work

potential energy

stored energy due to position or state, can be converted to kinetic energy. e.g in bonds

kinetic energy

energy of movement - the type that does work/makes changes

anabolic reactions

simple molecules linked to form complex ones - requires energy and captures it in chemical bonds formed (potential energy)

catabolic reactions

complex molecules broken down into simpler ones - energy released

1st law of thermodynamics

energy is neither created nor destroyed = energy is constant so can be transferred and transformed

open system

energy and matter can be transferred between the system and its surroundings - organisms are open systems

closed system

isolated from its surroundings

2nd law of thermodynamics

disorder tends to increase - energy transfer/transform increases entropy as when transformations of energy occurs some energy is lost or unusable

• in bio systems energy is lost as heat

entropy

measure of disorder in a system

change in free energy (G) equation

ΔG = ΔH - TΔS

G = free energy

H = total energy

T = temperature in Kelvin

S = entropy

Δ = change

endergonic reactions

needs input of energy to happen results in positive change in free energy (ΔG > 0). - anabolic

exergonic reactions

release energy, resulting in a negative change in free energy (ΔG < 0). - catabolic