Monday, 9/10/12

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Monday, 9/10/12

• Reminder Chp.8 Guided Reading homework is due
  tomorrow
• Grades are posted on window
• Pass back Controlled Expt Packets, discuss
• Chp.8 Lecture/Notes
• 1st lab this week!
• Chp.4,5,8 Test next Monday
• Carbon, Biomolecules, Enzymes

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Lecture Notes

• Chapter 8
• An Introduction to Metabolism

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Key Concepts from book

• (8.1) An organisms metabolism transforms matter
  and energy, subject to the laws of thermodynamics
• (8.2) The free-energy change of a reaction tells
  us whether or not the reaction occurs
  spontaneously (energetically favorable, process
  occurs without an input of energy).

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Key Concepts Cont.

• (8.3) ATP powers cellular work by coupling
  exergonic reactions to endergonic reactions.
• (8.4) Enzymes speed up metabolic reactions by
  lowering energy barriers.
• (8.5) Regulation of enzyme activity helps control
  metabolism.

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Metabolism/Bioenergetics

• Metabolism The totality of an organisms
  chemical processes managing the material and
  energy resources of the cell
• Catabolic pathways degradative process such as
  cellular respiration releases energy
• Anabolic pathways building process such as
  protein synthesis photosynthesis consumes energy

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Thermodynamics

• Energy (E)capacity to do work Kinetic energy
  energy of motion Potential energy stored energy
• Thermodynamics study of E transformations
• 1st Law conservation of energy E
  transferred/transformed, not created/destroyed
• 2nd Law transformations increase entropy
  (disorder, randomness)
  
• Combo quantity of E is constant, quality is not

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Free energy

• Free energy (G) portion of systems E that can
  perform work (at a constant T)
• Exergonic reaction net release of free E to
  surroundings
• Endergonic reaction absorbs free E from
  surroundings

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Fig.8.14 Energy profile of an exergonic reaction
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Energy Concepts Video Clip

• 2 min.

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Energy Coupling ATP

• E coupling use of exergonic process to drive an
  endergonic one
• Adenosine triphosphate (ATP)
• ATP tail high negative charge
• ATP hydrolysis release of free E
• Phosphorylation (phosphorylated intermediate)
  enzymes

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Figure 8.12 The ATP cycle
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Enzymes

• Catalytic proteins change the rate of reactions
  w/o being consumed
• Free E of activation (activation E, EA) the E
  required to break bonds
• Substrate enzyme reactant
• Active site pocket or groove on enzyme that
  binds to substrate
• Induced fit model

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How Enzymes Work Video Clip

• 1 min.

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Figure 8.13 Example of an enzyme-catalyzed
reaction hydrolysis of sucrose by sucrase
CH2OH
CH2OH
CH2OH
CH2OH
O
O
O
O
H
H
H
H
H
H
H
Sucrase
H
HO
OH
H
H
OH
H2O
HO
O
H

OH
H
O
HO
CH2OH
CH2OH
HO
OH
H
H
H
H
OH
OH
OH
Fructose
Glucose
Sucrose
C12H22O11
C6H12O6
C6H12O6
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Fig.8.17 The active site and catalytic cycle of
an enzyme
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Effects on Enzyme Activity

• Temperature (denature)
• pH
• Cofactors
• inorganic, nonprotein helpers ex. zinc, iron,
  copper
• Coenzymes
• organic helpers ex.vitamins

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Enzyme Inhibitors

• Irreversible (covalent) reversible (weak bonds)
• Competitive competes for active site
  (reversible) mimics the substrate
• Noncompetitive bind to another part of enzyme
  (allosteric site) altering its conformation
  (shape) poisons, antibiotics

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Allosteric Regulation

• Activators Inhibitors
• Insert Feedback inhibition example/diagram
• Pg.157, Figure 8.21

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Figure 8.21 Feedback inhibition in isoleucine
synthesis
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After if time

• Enzymes Metabolism Worksheet
• Reminder Chp.8 homework due tomorrow!!!!