Energy and Cell Chemistry

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Chapter 3

• Energy and Cell Chemistry

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Energy

• Ability to do work (move matter against a force
  such as gravity or friction) or cause change
  (such as during a chemical reaction)
• Plants can work in unusual ways since they are
  stationary
• Chemical energy made in photosynthesis is then
  used to make DNA, new cells, grow and reproduce
  animals eat plants and see an energy conversion

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Work

• Philodendron uses leaves to collect sunlight to
  make energy, however when reproducing the flowers
  can maintain a temperature of 45?C (113?F) during
  cold nights
• Heat aids in reproduction
• See in other plants such as skunk cabbage and
  voodoo lily
• Voodoo lily also produces a compound that smells
  like dung that attract certain insects that will
  help to pollinate other plants

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2 Types Energy

• Potential energy stored energy, available to do
  work in organism, stored in various molecules
  such as sugars and fats
• Kinetic energy energy being used to do work,
  burning sugar, transferring motion to other matter

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Heat

• Form of kinetic energy
• Cant use heat in plants for the most part
• Convert the potential energy in the rock at the
  top of the hill, only when the rock rolls down
  the hill do we see kinetic energy and the
  generation of heat
• Cant move between kinetic and potential energy
  with 100 efficiency

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Laws of Thermodynamics

• Govern flow of energy in nature
• Involves system (collection of matter or chemical
  reactions being studied) and surroundings
  (everything else)
• closed system no energy exchanged with
  surroundings
• open system readily exchanges energy and matter
  with surroundings

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1st Law

• Conservation of energy
• energy cannot be created or destroyed but can be
  converted to other forms
• OR
• energy in a system and surroundings remains
  constant
• OR
• amount of energy in universe is constant
• Plants convert sunlight energy and convert it to
  stored energy of organic molecules

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2nd Law

• Law of entropy disorder
• Energy transformation is inefficient amount of
  useful energy decreases in energy transformations
• OR
• systems tend towards more disorder,
  spontaneously, usable energy is lost as heat
• All systems reach maximum disorder universe is
  running down and becoming more disordered
• dead organisms decompose because no energy is
  being taken in to keep cells organized

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Survival Energy

• Organisms get energy by different mechanisms
• Plants use sunlight, animals eat organisms for
  energy, cells use chemical reactions to get
  energy breakdown fats and sugars to H2O and CO2
  and heat (very inefficient)
• Cells seem to violate the laws of thermodynamics
  because they are highly ordered, but cells are
  pen systems and they transfer heat to
  surroundings to maintain the order

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• All energy ultimately comes from the sun so
  plants, photosynthetic bacteria and algae are
  most important in this scheme

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2 Primary Energy Transformations

• Photosynthesis H2O and CO2 to make sugars
  (energy rich) and O2 is released\
• Cellular respiration extract energy from sugars
  and conserved temporarily as ATP
• otherwise too much heat release

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Metabolism

• All chemical reactions in an organism
• Break apart sugars, etc., slowly in steps drop
  in amount of energy available with some lost as
  heat but some is stored in other chemical
  reactions

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Metabolism

• Converts energy to work
• Vast array of chemical reactions happening in
  cells
• occur in step-by-step reactions metabolic
  pathways
• Product of 1 reaction becomes the substrate for
  the next reaction

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sugar O2 ? H2O CO2 ATP heat

• Catabolic reaction catabolism
• breakdown large molecules into smaller molecules
• see above reaction
• Anabolic reaction anabolism
• small molecules assembled into large molecules
• sugar into starch
• (Hint anabolic steroids make you bigger)

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Oxidation and Reduction

• Chemical reactions
• Oxidation adds O2 to substance or lose electrons
  (catabolic reaction, release energy)
• Reduction adds electrons either alone or with 2
  H (anabolic reaction, requires energy)
• Redox reactions work together

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ATP Energy

• Main energy source for cells
• Energy storage form from the breakdown of energy
  rich compounds cellular respiration
• Use the energy in anabolic reactions
• ATP is a ribonucleotide and energy is trapped in
  the 3rd phosphate bond, hydrolysis reaction

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Why ATP Is Effective

• 3rd PO4 bond is weak compared to the other 2
• Releases 2x the energy needed to drive an
  anabolic reaction but just right for others
• Cant cross the plasma membrane so remains with
  the cell
• ATP is not a long term energy storage molecule
  because it is unstable in the long run
• Still most common energy source in the cell and
  we generate large amounts every day

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2 Types of Reactions Need ATP

• Coupled reactions use the energy in 1 reaction
  to make ATP and then use the ATP to drive the
  second reaction, occurs simultaneously (linking
  an exergonic to endogonic reaction)
• Phosphorylation reaction transfer of the PO4
  gives the molecule the energy required to do the
  next reaction may be at a later time

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Other Energy Storage Molecules

• NAD - nicotinamide adenine dinucleotide is
  reduced to NADH (accepts 2 e- and H)
• used to make ATP during cellular respiration
• NADP - nicotinamide adenine dinucleotide
  phosphate is reduced to NADPH
• used during photosynthesis
• Both are derivatives of the vitamin Niacin
  (vitamin B3)

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Enzymes

• Used to speed up reactions by lowering the
  activation energy
• cells cannot wait for reactions to occur
  spontaneously
• Organic catalysts
• Regulate the rate of metabolic reactions
• Enzymes are the targets of some drugs, whether
  you are a plant or animal
• herbicides
• antibiotics
• Some human diseases are caused by ineffective
  enzymes

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Molecules of Life

• Carbohydrates, proteins, lipids and nucleic acids
• make up the majority of cells if you exclude H2O
• All are built from the CO2 in photosynthesis
  along with H2O and minerals in the soil using
  energy from the sun
• All are polymers made by adding single subunits
  to a growing molecule (lipids add 2 subunits at a
  time)
• Variation in the amounts and types of polymers
  make up the differences between plants and
  animals
• Plants have some special molecules such as
  lignin, alkaloids, terpenoids and sterols that
  are important to plant function

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Carbohydrates

• Store energy, C and make up wood of trees
• Formula 2 H and 1 O for each C
• glucose is C6H12O6 but so is fructose, elements
  are arranged differently and this imparts
  different physical properties
• Carbohydrate monomers can be attached to other
  molecules as well
• Types of carbohydrates
• monosaccharide single sugar (simple)
• disaccharide 2 monosaccharides linked (simple)
• polysaccharide many sugars linked (complex)

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Sucrose

• Most common simple sugar in plants table sugar
• Made of glucose and fructose
• Moves carbon/energy from leaves to roots so can
  ve used to make energy in non-photosynthetic
  parts of plants
• can be harvested to make maple syrup
• used as an energy source by insects
• bees eat the nectar and makes honey flavor from
  the oils in the nectar and from the pollen grains

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Cellulose

• Most abundant polysaccharide in plants and most
  abundant polymer on earth
• Found in cell wall of plants and can make hard
  enough to form wood, fibers around cotton seeds
• Strength comes from structure 100 to 15,000
  glucose molecules in a linear fiber, 1000 or more
  fibers twist into a microfibril like a cable

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Cellulose Fibers

• Intertwining microfibrils
• Other molecules such as pectins and
  hemicelluloses help to form a meshwork
• acts like reinforced concrete in terms of
  structure and stability
• Cell wall will allow H2O/nutrients to pass thru

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Hemicelluloses

• Come from stem, roots, leaves and fruit
• Called gum complex, branched complex, usually
  several types of monomers
• gum arabic in glue, beer suds, hand lotions and
  liquid soup NOT chewing gum

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Commercially Important Polysaccharides

• Agar and Carrageenan
• made from red algaes slippery substance around
  the cell wall
• each is different mix of monomers
• Agar drug capsules, gelatin and cosmetics used
  in microbiology to solidify the medium to grow
  bacteria and fungus
• Carrageenan stabilizer in paint, cosmetics,
  salad dressing and also smoothing agent in salad
  dressing

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Starch

• Most common storage polysaccharide
• Repeating glucose monomers
• Used as stored energy during germination and
  seedling growth
• Animals use as a food source and can actually get
  calories from, unlike cellulose
• Stored during photosynthesis and used during the
  dark reactions as energy and converted to sucrose
  for entire plant to use
• Sucrose can get converted back to starch in the
  potato and lima bean

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Inulin

• Another storage molecule
• Polymer of fructose
• In dahlias, Jerusalem artichokes, globe
  artichokes and sweet corn
• taste sweet because of the fructose