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Metabolism

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Title: Metabolism


1
Metabolism
2
Cell Energetics
  • Metabolism total of all the chemical reactions
    taking place in an organism

3
Metabolism
  • Anabolism build up processes consume
    (store) energy by assembling macromolecules
    (photosynthesis)
  • Catabolism break down reactions release
    energy by breaking down (lyse) molecules
    (digestion)

4
  • Concept 8.1 An organisms metabolism transforms
    matter and energy, subject to the laws of
    thermodynamics

5
Metabolism
  • Energy - the ability to do work
  • Closed Systems - system without energy input
  • Open systems system with energy input

6
Types
  • Potential capacity to do work
  • Caused by POSITION
  • Stored chemical energy (glucose, glycogen)
  • Kinetic energy of motion
  • Equilibrium energy runs out

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8
Thermodynamics
  • Thermodynamics - the study of energy
    transformations
  • 1st Law of Thermodynamics - energy cannot be
    created nor destroyed transformed

9
  • 2nd Law of
    Thermodynamics - in a
    closed system, when
    energy is
    transformed,
    some is lost as heat
  • Entropy decreasing
    available energy of the
    universe is
    increasing
    (disorder)
  • Energy systems become more disordered/random
  • Total entropy increases stuff runs down

10
Free Energy
  • The energy in a system
    available for work
  • A spontaneous change can cause free energy to
    flow
  • System becomes more stable
  • Less work capacity
  • Free energy decreases (entropy)

11
Biological Order and Disorder
  • Organisms live at the expense of free energy
  • Organisms are open systems with low entropy
  • Use free energy to maintain order and
    organization
  • Convert complex molecules into simpler ones
    digestion
  • Trade organization for heat (increases randomness
    and entropy)

12
Types of Reactions
  • Exergonic reaction - net release of free energy
  • Less stable, more work
  • Fire, respiration
  • Endergonic reaction - energy-requiring reaction
    energy is absorbed/stored
  • Photosynthesis

13
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15
Concept 8.3 ATP Powers Cellular Work by Coupling
Exergonic Reactions to Endergonic Reactions
  • Cells do three main kinds of work
  • Mechanical - movement
  • Transport of stuff
  • Chemical polymerization, bioluminescence

16
Coupled Reactions
  • Coupled Reactions - endergonic reactions are
    coupled with exergonic reactions
  • Energy from an exergonic reaction (respiration)
    is stored in phosphate bonds
  • Phosphate group is added to a molecule
  • Phosphorylation
  • Molecule works

17
ATP
  • Adenine ribose phosphate group
  • Phosphate bond is easily broken/formed
  • Controlled by enzymes

18
Uses of Energy
  • Mechanical - beating of cilia/flagella, muscle,
    cytoplasmic flow, movement of chromosomes
    (mitosis)
  • Transport - H pump, receptors
  • Chemical polymerization, bioluminescence

19
Enzymes
20
Concept 8.4 Enzymes speed up metabolic reactions
by lowering energy barriers
21
Enzymes
  • Enzymes - biological catalysts
  • Accelerate reactions without being changed
  • Proteins (700)
  • Catabolic or anabolic
  • All chemical reactions require activation energy
  • Activation energy, EA - the initial amount of
    energy needed to start a chemical reaction
  • Often supplied as heat from the environment
    (spontaneous)

22
Enzymes
  • Cellular T needs to remain low, but metabolism is
    too slow at low T
  • Enzymes reduce activation energy
  • Transition state - reactants have absorbed energy

23
Enzymes
  • Substrate substance enzyme acts upon
  • Active site area on the enzyme which the
    substrate binds to (attaches)
  • Verryyy specific
  • Groove, pocket 3d shape

24
Enzymes
  • 2 mechanisms describe how enzymes function
  • Lock and Key
  • Induced Fit - enzyme may change shape to allow
    better reaction on substrate

25
Chemical bonds broken
Active site
Induced fit
26
Enzymes
  • Enzymatic action is reversible
  • E S P E
  • Enzyme unaffected by reaction
  • Dependent upon concentration of reactants vs
    products
  • Reaction rate of 1000s per second
  • Speeding up enzyme reactions
  • Add more substrate until saturated with
    substrate
  • Add more enzyme
  • DNA controls cells activities by storing the
    code for protein synthesis (enzymes)

27
Factors That Affect Enzyme Activity
  • Temperature and pH
  • Inorganic salts disrupt H, ionic bonds,
    hydrophobic interactions
  • Cofactors
  • Inhibitors

28
Cofactors
  • Cofactors - nonprotein enzyme helpers
  • Metals Fe, Zn, Cu
  • Coenzymes - organic
  • Vitamins
  • Inhibitors substances that inhibit the actions
    of enzymes (2 kinds)
  • Competitive inhibitors
  • Noncompetitive inhibitors

29
Competitive inhibitors - resemble substrate,
block active site Neurotoxin, Disulfiram
30
Enzymes
  • Noncompetitive inhibitors - causes enzyme to
    change shape
  • Destroys conformation (active site)
  • DDT, nerve gas (DSF)
  • May be allosteric regulation

31
Concept 8.5 Regulation of enzyme activity helps
control metabolism
  • A cells metabolic pathways must be tightly
    regulated

32
Allosteric Regulation of Enzymes
  • Allosteric regulation - a proteins function at
    one site is affected by binding of a regulatory
    molecule at another site
  • Receptor site located away from the active site
    (quaternary structure)
  • Allosteric site has to be activated, (may be
    inhibited)

33
Allosteric activator
34
Allosteric inhibitor
35
Enzymes
  • Cooperativity - one substrate molecule can
    activate all other subunits of an enzyme
  • Only requires a small concentration of substrate
    to activate enzyme
  • Hemoglobin

36
Feedback Inhibition
Isoleucine allosteric inhibitor
  • Metabolic pathways series of enzymes creates
    small steps to a final product
  • Controlling the enzymes (activity or production)
    controls the pathway and product(s)
  • Feedback Inhibition - end product of the pathway
    inhibits the pathway

37
Enzymes
  • Feedback inhibition prevents cells from wasting
    resources
  • dont need gas if you dont have a car.

38
Structure and Metabolism
  • Cells are organized
  • Enzymes are grouped into complexes or
    incorporated into membranes
  • Multi-enzyme complex enzymes are assembled in
    correct physical position for a sequence of
    events to happen
  • Mitochondria, chloroplasts
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