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Biology 111
Ch 6
Energy Definitions
• Ultimately ALL energy comes from the sun
Bioenergetics
• The study of how living organisms use
energy to perform activities of life
Energy – ability to do work (change or
move something) – can be converted
from one form to another
– Radiant to chemical • Wind to electrical
– Chemical to heat
• Solar to heat
Energy moves from
molecule to
molecule through
electrons
Calorie – amount of energy
required to raise the temperature of
1 gram of water 1 degree Celsius
Kilocalorie – unit for measuring
energy in food and output of
organisms – must raise 1000 g
of water 1 degree C.
1kilo cal = 1000 calories
Photosynthesis – energy requiring
stage of energy acquisition
Cellular Respiration – energy
releasing stage
Organisms receive energy from the sun, the earth
and other living things
• Direct from sun, indirect from other
organisms
• Photons – packets of light energy
– Absorbed by electrons (temporarily)
Sun’s annual output- 3.8 sextillion
megawatts of electricity
• Earth gets 2 billionths of this
– Most doesn’t reach living organisms
– 1/3 reflected back into space
– ½ absorbed by planet (converted to heat and
returned to space
– 19% used to power wind and weather and
drives photosynthesis
• Of this, .05% - 1.5% is incorporated into plant
material
– 1/10th of this makes it way into bodies of
animals that eat plants - How many Mw is this?
Most species depend on
autotrophes for energy
A few species get energy
from geothermal sources
Bacteria at vents
provide hydrogen
sulfide – called
Chemoautotrophes
Aerial view of Yellowstone
hot springs
Energy at rest is potential Energy.
Energy in motion is kinetic energy.
Potential – STORED in chemical bonds
Kinetic- chemical bonds BREAK – energy
released – moves objects (atoms)
Laws of Thermodynamics – regulate
energy conversion for life and non-life
• Open system- exchanges energy with
surroundings
• Closed system – no exchange outside the
system
Opened or Closed??
1st Law: Energy is neither created
nor destroyed, but changes form
• Energy in Universe is
constant
• Living systems continually
change
• Amount of energy an
organisms used cannot
exceed the amount of
energy it takes in through
chemical bonds in
nutrients
All energy transformations increase entropy
• Entropy – tendency toward randomness
– Energy transformations are inefficient –
reactions result in increased entropy and loss
of energy as heat
– All energy can convert to heat, but not viceversa
– Energy proceeds in one direction
– Spontaneous – processes that occur without
an energy input
Cell energetics from 2nd Law:
Inefficient reactions lead to
metabolism and produce heat
• Most cells extract about half of the energy
in nutrients
• Organisms remain organized because
they are NOT a closed system
– Coupled reactions – one reaction occurs at
the expense of another
• Organisms can increase in complexity as long as
something else decreases in complexity by greater
amounts
• The sun always decreases in energy.
Metabolism – chemical reactions that
change or transform energy in cells
Fatty Acid Metabolism
Metabolic pathways – step by step sequences of
metabolism – ex: photosynthesis and cellular
respiration
Anabolism– constructs large molecules from
small – USES energy
Catabolism - Large molecules into small –
RELEASES energy
FORMING bonds takes energyBREAKING bonds releases energy
• Bond energy – amount of energy stored in
the electrons of a chemical bond (
• Free Energy – amount of energy
potentially available to form new bonds
• Energy of activation – start up energy
(kindling temp for fire)
Endergonic and Exergonic
• Endergonic- products contain more energy than the reactants
– Ex: glucose + fructose = sucrose (Anabolism is endergonic
• Exergonic reaction- products contain less energy than the
reactants
– Ex Glucose  Carbon dioxide + water (catabolism is
exergonic)
– Hyperlink on
picture
Reactions halt when equilibrium is met
• Chemical equilibrium – when reactions go
back and forth at the same rate
– Energy not gained or lost
In living systems, electrons move through
oxidation/reduction (Redox) chains
• Oxidation – loss of electrons from a molecule
– Usually oxygen takes a molecules electrons
– Ex. Oxidation of glucose
• Reduction – gain of electrons ( therefore energy)
– Usually are anabolic and require energy
• Redox – linked reactions – ex. Electron transport
chains – the more reduced they are the more energy
they contain.
ATP- Energy Currency in the Cell
• Adenosine Triphosphate- stored useable
energy – made in the mitochondria during
cellular respiration.
Loss of phosphate group = energy release.
Provides almost twice as much energy as
necessary to energize mot biological reactions
(extra energy is given as heat
Cells couple ATP formation and
breakdown to other reactions
• Cells use ATP 2 ways
– To energize a molecule
– To change the shape of a molecule
– Both transfer phosphate to another molecule
– process called phosphorylation
• Phosphate is released after reaction occurs
• 7 kilocalories are released in splitting 1 mole (1023
molecules) of ATP
Cofactors – non protein helpers enable
some reactions to proceed
They are often trace minerals (Mg2+)
cofactor
enzyme or protein
Zn++
carbonic anhydrase
Zn++
alcohol dehydrogenase
Fe+++ or Fe++
cytochromes, hemoglobin
Fe+++ or Fe++
ferredoxin
Cu++ or Cu+
cytochrome oxidase
K+ and Mg++
pyruvate phosphokinase
Coenzymes – carry protons
Vitamin
or electrons (NAD+)
•May be a nucleotide like ATP
•Depends on it’s ability to
donate or receive an electron
(not phosphorylation)
•Vitamins are source
•Examples: NAD+ and others
niacin
riboflavin
Coenzyme
Function
nicotinamid
e adenine
dinucleot
ide
(NAD+)
oxidation or
hydrogen
transfer
flavin
adenine
dinucleot
ide (FAD)
oxidation or
hydrogen
transfer
pantothenic
acid
coenzyme A
(CoA)
Acetyl
group
carrier
vitamin B-12
coenzyme
B-12
Methyl
group
transfer
thiamin (B1)
thiaminpyro
phosphat
e (TPP)
Aldehyde
group
transfer
Enzymes: Life’s Catalysts
Activation energy may come from environment
Enzymes speed biochemical reactions
Enzymes decrease the energy of activation
Enzymes sensitive to denaturation
Cells control metabolic pathways
• Negative feedback- when too much product is made,
cells need to turn process off. Final product binds to an
enzyme – turns process off (aka feedback inhibition)
• Competitive inhibition – product binds to enzyme active
site (competition for site)
• Noncompetititive inhibition – product binds to a a site
other than active site – changes shape of enzyme
Positive Feedback