Chapter 5 Energy
Energy: capacity to do work
Capacity to create change
Potential energy is potential change
Kinetic energy is change in progress
1st law of thermodynamics: Energy cannot be
created or destroyed, but only change form
2nd law of thermodynamics:
(in a closed system (no energy input from outside))
Energy transformations tend to become heat/
Energy transformations always have less than
100% efficiency/
Entropy increases/
Disorder increases/
Mixed-upedness increases
Energy and chemical reactions
Exergonic reactions
(high energy molecule  low energy molecule)
Endergonic reactions
(low energy moleculehigh energy molecule)
Coupled reactions
ADP + P  ATP endergonic
Glucose  CO2 + H2O exergonic
Enzymes: catalyst
Catalyst: speeds up a chemical reaction; lowers
the activation energy
Catalysts are not consumed by the reaction
Catalysts are not strictly speaking necessary for
the reaction to occur
Spontaneous/exergonic reactions don’t initiate
without activation energy (wood needs a spark to
start burning, but not to continue burning)
Enzymes allow living things to control the
occurance and rate of chemical reactions
Enzymes are proteins. Each enzyme has a very
specific shape.
Metabolism:
All the chemical reactions in the body
All the energy transformations in the body
Metabolic rate:
Rate of the chemical reactions
Rate of the energy transformations
Classify organisms by how they get energy
Autotrophic: take sunlight and make food
Heterotrophic: find food in the environment
Redox reactions
Reduction and oxidation
Reduction (adding electrons, usually means
adding energy)
Oxidation (removing electrons, usually means
lowering energy)
Diffusion: particles move from high concentration
to low concentration
Osmosis: diffusion of water
Direction of diffusion is from high concentration
to low concentration
Gradients are a form of potential energy
Passive transport (diffusion and osmosis): no
energy input needed, downhill, no ATP
Active transport: cell working to move particle
across a membrane to a higher concentration
(uphill); requires ATP
Osmosis of water
Hypertonic solution (e.g. seawater): pulls water
out of the cell
Hypotonic (e.g. freshwater): drives water into the
cell
Isotonic (body fluids): equal osmotic pressures
inside and outside of cell, no movement of water
Endocytosis: cell membrane engulfs a volume of
fluid, and forms a vesicle or vacuole that enters
the cell
Exocytosis: cell bulk export