Metabolism

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Metabolism
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Mechanistic view tells us living matter obeys the
ordinary, (universal) laws of physics and
chemistry
Conservation of mass
Conservation of momentum
Gravitation
Chemical properties of elements

• Laws of thermodynamics

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Laws of thermodynamics

• In any isolated system (no matter or energy can
  enter or leave), including the entire universe

• First Law total amount of energy is constant,
  though it can change form

• Second Law Whenever anything actually happens,
  the entropy (disorder) of the system (or of the
  universe) increases (cannot decrease)

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Laws of thermodynamics
Times Arrow points in the direction of
increasing entropy of the universe

• Disorder may be in the arrangement of matter or
  energy Heat (thermal energy) is disordered
  energy

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Mowing the Lawn Thermodynamics

• Given amount of chemical energy in gas

1st law - energy still in gas, transferred to
blades, noise, heat (exhaust, engine)

• 2nd law energy dispersed and isnt available to
  produce initial fuel and do work

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How can life exist?
Life is an organization of matter
A systematic DECREASE in entropy

• Violates the 2nd law of thermodynamics!!

Organizing processes require energy
7
What is the isolated system?

• The Universe as a whole not the Earth
• Steady input of energy from the sun (sun is
  losing energy it will burn out)
• Life is a series of energy transfers

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Food as Energy
http//www.istockphoto.com/file_closeup/style_and_
design/illustrations/line_drawings/73675_baked_bea
n_couple.php?id73675
www.go.dlr.de/wt/dv/ig/icons/funet/cartoon5.gif
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Two hypotheses about animalsuse of food
1. Assimilation - food is added to body for
growth or to replace material lost through wear
and tear
2. Combustion - food is somehow burned within
the body, like fuel in a fire, generating heat,
and being consumed in the process)
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Aristotle and Animal Nutrition

• Animals are composed of the four elements
• Different organs have different proportions of
  each
• Eat to replace material as result of wear and
  tear
• Food contains the same four elements, and can be
  added to the body (assimilated)
• Before being assimilated, food processed
  (concocted) to adjust the proportions to suit
  the different organs

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Food Function and relationship to anatomy
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Human Dissections and Vivisection
Post-mortem examinations were rare well into the
Middle Ages, largely due to religious and
intellectual scruples. This early representation
(c. 1300) of a dissection shows a surgeon and a
monk.
http//www.karlloren.com/ultrasound/p39.htm
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Galen of Pergamum (ca. 130-ca. 200)

• Dissected dead animals served as physician to
  gladiators
• Observed blood vessels (tubes) connecting
  intestines to liver, liver to heart, and heart to
  lungs

www.malaspina.com/jpg/galen.jpg
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Galens Model

• Digestion consisted of series of concoctions to
  refine food
• Food absorbed by intestines
• 1st concocted in liver ? flows to heart
• Further refinement in heart to make blood ? out
  to tissues
• Additional concoction in brain more highly
  refined fluid

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Galens Model

• Before blood leaves heart exchange of material
  with lungs
• Blood flow right to left ventricles via little
  holes
• Waste material right ventricles to lungs
• Lungs take in air ? left ventricle exposed to
  blood producing pneuma (vital spirit vital
  heat)

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14th century anatomist Vesalius

• Spent a good deal of his time sneaking into
  graveyards and stealing bodies
• Would dissect corpses make detailed notes
  illustrations
• Later commisioned artist Titan to do
  illustrations for his book Di Humani Corporis
  Fabrica
• Book and illustrations revolutionary in the field
  of medicine and art
• Contradicted Galen

http//www.search.com/reference/Vesalius
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Di Humani Corporis Fabrica
tyranny.com/graphics/jpegs/vsel1.jpg
tyranny.com/graphics/jpegs/vsel7.jpg
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The Anatomy Lecture of Dr. Nicolaes Tulp by
Rembrandt van Rijn (1632)
mathiasbynens.be/images/anatomy-lecture.jpg
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The Anatomy Lecture of Dr. Nicolaes Tulp by
Rembrandt van Rijn

• Reveals significant changes in the way anatomy
  taught, illustrates a major conceptual
  methodological development in the understanding
  of the natural world
• Notably changed in the portrait is the placement
  of the text, which had directed the observations
  of earlier anatomists
• Focus of lecturer students on corpse, with text
  in shadows at foot of dissecting table
• Close observation by the students is emphasized,
  and the dissection itself reveals the hidden
  underlying structures of the human form

mathiasbynens.be/images/anatomy-lecture.jpg
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William Harvey

• Performed a series of experiments on blood flow
• Observed heart as it beat in a living animal
• Heart is muscular tissue with valves

Members.aol.com/ldaucourt/Histmed.htm
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Heart as a muscular pump
www.med.umich.edu/1libr/aha/hrtflow.gif
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William Harvey

• Calculated heart pumps out 2 oz blood with each
  contraction
• If blood is absorbed ? would provide 10 lbs of
  blood / minute (dont eat that much)
• Blood must circulate

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William Harvey Studies on Blood Flow
www.life.uiuc.edu/ib/494/harvey.html
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Opposition to William Harvey

• Against long-held views
• Inability to explain HOW blood provides
  nourishment
• Connection between arteries and veins?

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Marcello Malpighi (1661) De pulmonibus
observationes anatomicase

• Top left - frog's lung external view
• Top right - lung cut longitudinally
• Alveoli connected with tracheo-bronchial tubes by
  capillary network.
• Established connection - veins and arteries which
  anatomists had been looking for but never found

http//www.scienzagiovane.unibo.it/English/scienti
sts/malpighi-2.html
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Artery ? Capillaries ? Vein
Blood Flow
www.daviddarling.info/images/capillaries.jpg
http//nmhm.washingtondc.museum/news/healthyheart.
html
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Nutrition as replacement of lost material

• Food replace tissue lost from wear and tear
  lubricate muscles joints
• Tissues made of cells / globules in blood
  tissue growth assimilation of globules
• Globularist hypothesis rejected
• - blood globules not same size as cells
• - muscle cells long fibrous
• - how do blood globules get out of blood
  vessels
• But 1830s nutrition still assimilation

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Nutrition as Combustion

• Life dependent on inner fire
• Warm when alive cold when die
• Aristotle innate heat needed by animals
• Galen vital heat associated with pneuma
• Like gunpowder (potassium nitrate sulfur)
• aerial nitre breathed in produces heat when
  reacts with sulfurous material in tissue
• Descartes and others heat arising from friction
  due to movement of body parts

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Combustion hypothesis

• Leonardo da Vinci (1500s) compared animal heat
  to burning candle, and suggested that food served
  as fuel
• Lavoisier (late 1700s) stated flames and animals
  consume oxygen - O2 and produce carbon dioxide
  CO2
• What do flames and animals have in common?

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Lavoisier Laplace slow combustion
www.sjsu.edu/faculty/watkins/Laplace.gif
Lavoisier
http//historyofscience.free.fr/Lavoisier-Friends/
a_tab2_lavoisier_alone.html
Laplace
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Lavoisier and Laplaces Ice Bucket Calorimeter

• Produced CO2 by burning coal or respiration from
  guinea pig
• Measured O2 used CO2 and heat produced

http//www.chem.yale.edu/chem125/125/history99/2P
re1800/Lavoisier/Instruments/calorimeter.html
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Observations on combustion and animals

• both produced about the same amount of heat (as
  measured by amount of ice it melted) per cubic
  inch of CO2 produced.
• both produced about the same volume of CO2 for
  each cubic inch of O2 consumed (0.81 vs 0.75
  cubic inches)
• difference attributed to the amount of air
  carried in the fur of the guinea pig as it was
  thrust through mercury into the sealed chamber)
• concluded that the production of heat and CO2
  were linked and that the underlying process was
  the same in combustion as in respiration

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respiration is therefore a combustion, very slow
it is true, but otherwise perfectly similar to
that of charcoal
it occurs in the interior of the lung, without
producing perceptible light, because the
liberated matter of fire is immediately absorbed
by the humidity of these organs
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Slow combustion

• They hypothesized that animals carry out a slow
  combustion of fuel (now called cellular
  respiration).
• They believed that the function of cellular
  respiration was to make heat.

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How do we use food?

• thermodynamics of chemicals centered on release
  of heat ? wood, coal, other organic chemicals
• heat is one form of energy
• any substances burned releasing heat must contain
  energy in their chemical make-up
• food molecules source of energy because they have
  relatively weak, less stable chemical bonds
  therefore high potential energy

36
How do we use food?

• CO2 H2O have especially strong chemical bonds
  therefore relatively low potential energy
•  
• to synthesize high-energy food molecules from
  more stable, lower-energy molecules (CO2 H2O),
  a source of energy is needed ? light energy from
  the sun
• once appreciated that food molecules are sources
  of energy, photosynthesis and respiration can be
  looked at in a new way

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How do we use food?

• The eventual fate of most of the energy released
  from food molecules is indeed heat (as Lavoisier
  thought), but it is the intermediate uses of that
  energy that make life possible
• Cellular Respiration
•