93 What rules govern cellular energy flow Chapter 5 and lead in to CH 6

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9/3 What rules govern cellular energy
flow?Chapter 5 and lead in to CH 6

• CH 4 please go back and look at the review
  questions! Questions 1a, 4-4, 4-5, 4-7 are best.
• What do cells use energy for?
• What units are used to measure energy in an
  isolated systems like cells?
• How much energy is contained in proteins, lipids
  and carbohydrates? ATP is ultimate energy
  currency!
• 1st Law of Thermodynamics energy is conserved!
• 2nd Law of Thermodynamics disorder of energy in
  a system always increases!
• How does standard free energy let us predict
  reactions? ?Go
• Dont forget to read CH 5!!!!

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What six forms of work are present in
biological systems?
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Energy is the capacity to do work or cause
change!What are 6 ways cells use energy?

• 1) Synthetic Work is the Classic Biosynthesis
• Cells use energy to form chemical bonds and make
  more ordered products
• Why do cells need energy for maintenance?
• Why do cellular needs change over time?
• Cellular time frame
• Time frame of organism life span
• Inceptiongtgrowthgtreproductiongtmaintenancegtrepair
• Synthesis of large molecules
• DNA, Proteins, Lipids, Polysaccarides
• Synthesis of small molecules
• Glucose, amino acids, fatty acids, etc
• Degradation of biomolecules requires energy
• Damaged collagen or tissues
• Digestion

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2 ) Homeothermy energy generates HEAT (work)
which vitally modifies enzyme function/activities
in the cell or the organism. Source broken
chemical bondsHeat a by-product of many other
types of energy transferChange is the
temperature of the system

• 3) Concentration Gradients are an important type
  of energy in cells and the body!
• Gradient more molecules stacked on one side of a
  PM than other!
• Cells establish gradients using energy from
  broken bonds!
• Gradients are expensive to maintain!
• Release energy (dam analogy) when gradient is
  released,,,i.e. Mitochondrial H gradient/motion
  is used to make ATP!
• Up to 2/3 of cellular energy expenditure is used
  to run pumps that maintain chemical gradients
  across the plasma membrane!
• Na-outside and K-inside the cell!

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4) What kinds of motion require energy?
1)Flagellated cells (sperm) -cells move relative
to environment when a dynein arm moves relative
to a microtubule 2) Ciliated
epithelium (bronchi)-move particles relative to
cells when a dynein arm moves
relative to a microtubule 3) Muscle
cells-contraction/shortening in given
dimension4) Chromosomes -chromosomes move
relative to spindle when
kinetochore moves relative to microtubules
5) Cyclosis in plant cells -organelles etc
move through cytoplasm when mysoin moves relative
to microfilaments -6) mRNA moves relative to
ribosome during protein synthesis 7)
Movement of plant parts (venus flytrap)
-biological "hydraulic
movement"-leaves snap shut as turgor pressure in
key cells changes rapidly 8)
Amoeboid movement-cytoplasmic flow and movement
of actin within the cell
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5) Electrical Work can also be performed,
typically from an established concentration
gradient!Membrane potentials (mV)!Current?
electric eels!Current? ECG or EMG!Changes in
electric fields and navigation!

• 6) Energy can also be used by cells to provide
  for bioluminescence!
• Fireflies and signaling
• Deep sea fish (symbiotic bacteria)
• Energy converted to released photons of light!

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How are cells classified relative to energy
source?

• Autotrophic energy generation is independent of
  contributions from pre-existing life.
• Photosynthetic Only about 40 of the captured
  energy is actually converted to sugars etc.
• Chemosynthetic bacteria
• Heterotrophic Obtain energy that was converted
  to storage chemicals by autotrophs!
• Energy Released from storage via
• Glycolysis-
• Fermentation-
• Respiration-
• Other pathways for energy use also exist!

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How do we measure energy use, content and
production in living things in an isolated system?

• Chemistry 1 calorie (cal)
• energy needed to heat 1 ml of water 1 degree
  (from 14.5 to 15.5 C)
• Nutrition 1 kilocalorie (kcal) or Calorie (Cal)
• energy needed to heat 1,000 ml or 1 liter of
  water
• 1 degree (from 14.5 to 15.5 C)
• Joules are a unit of energy more commonly used by
  European scientists 1 J 0.239 cal or 1 cal
  4.184 J
• We usually refer to energy content as
• cal/mole OR Cal/grams

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Examples of Energy Content

• Carbohydrates 4 Cal/g.400 g 1,600 Cal
• Protein 4 Cal/g.200g 800 Cal
• Lipids 9 Cal/g..200g 1,800 Cal
• All cells of body require a total of about 2,000
  Cal/day
• All cells of body require a total of about
  2,000,000 cal/day
• Cells in your body need __grams glucose/day for
  2,000 Cal
• Basic calculations on test will not require a
  calculator.
• Adenosine Triphosphate (ATP) is the energy
  currency that mediates most forms of cellular
  work!
• Whys is ATP handy in this regard?

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1st Law of Thermodynamics energy is conserved in
different forms in a cell!

• Energy can change forms (chemically or
  physically) in a cell but cant be created from
  nothing or simply disappear!
• The total amount of energy in a cell is dependent
  on what enters and leaves!
• Heat Content (enthalpy or H) takes into account
  internal energy, pressure and volume
• ?H ?E ?PV
• ?H ?H products - ?Hreactants
• If heat content of products is less than
  reactants heat was released---Exothermic!
• If heat content of products is greater than
  reactants heat had to be added to the system
  from and external source Endothermic!

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2nd Law of Thermodynamics disorder of energy in
a cellular system always increases!

• Systems and chemical reactions tend towards
  greater randomness!
• This lets us predict if a reaction will
  spontaneously occur under a set of conditions!
• Entropy or S measures system randomness!
• Change in or Delta (?) S measures changes in
  Randomness!
• Gibbs Free Energy measures system spontaneity!
• ?G measures changes in Free Energy
• System Temperature measured in absolute units
  called Kelvins
• Gibbs Free Energy measures system spontaneity!
• ?G measures changes in Free Energy
• System Temperature measured in absolute units
  called Kelvins
• ?G ?H -T?S
• Change in G(Change in Enthalpy)-(Temp)X(change
  in Entropy)
• If ?G is NEGATIVE Spontaneous reaction occurs!
• ATP ? ADP Pi Energy
• If ?G is POSITIVE reaction requires ADDED energy
  from an external source before it will occur!
  ADP Pi Energy ? ATP
• A negative ?G means it occurs, but RXN speed is
  not indicated!

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Negative ?G means energy released by this
oxidationPositive ?G means energy required for
this reduction
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Standard Free Energy (?Go )lets us predict if a
reaction will occur in a cell under a set of
observed conditions.

• Assume reactants and products are present at
  molar concentrations of 1 M and pH7.0
• ?Go-2.303RT log keq
• -2.303 is a mathematical constant
• R is the gas constant 1.987 cal/mole K
• T is temperature in Kelvin (usually 298 K)
• Keq Equilibrium Constant-ratio of products and
  reactants when the reaction comes to its normal
  equilibrium
• The larger the - ?Go more energy is released in
  achieving Keq!

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ATP hydrolysis releases energy so cells can run
chemically unfavorable reactions. ATP provides
?Go that allows cells to perform unfavorable
reactions under the condition inside a cell!

• Classic ?Go values for hydrolysis to lower
  energy state products
• ?Go Kcal/mole
• ATP gt ADP Pi
• ?Go -7.3 energy released!
• Glucose PigtG-6-P H2O
• ?Go 3.3 energy required!
• Net ?G (-7.3) (3.3) -4
• ATPGlucosegt G-6-P ADP
• ?Go -4 kcal/mole
• Negative so reaction occurs
• The enzyme hexokinase speeds the reaction up!

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