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Transcript of Mills 2012 Chapter 6 Metabolism: Energy and Enzymes Read chapter 6 of textbook Read Enzyme Activity...
Mills 2012
Chapter 6Metabolism: Energy and
Enzymes
Read chapter 6 of textbookRead Enzyme Activity Lab in AP Lab Manual (#13)
Read pages 22 (chemical reactions and metabolic processes)
in CliffsAP (3rd)
Do MC questions on pg 25-28 of Cliffs – Due Sept 17Be sure you could answer the free response questions
pg 29
Mills 2012
Chapter 6Metabolism: Energy and
Enzymes• Topics
– 6.1 Cells and the Flow of Energy– 6.2 Metabolic Reactions and Energy
Transformations– 6.3 Metabolic Pathways and Enzymes– 6.4 Metabolic Pathways and Oxidation Reduction
Mills 2012
Metabolism: Energy and Enzymes6.1 Energy
• Energy = capacity to do work or bring about a change
• All living things need energy• Many kinds of energy
– Kinetic energy
• Energy of motion
• Mechanical
– Potential energy
• Stored energy
• Chemical energy
Flow of Energy
4
solarenergy
heat
heat
heat
heat
Mechanical energy
Chemicalenergy
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
sunCO2
H2O
solar energy producercarbohydrate
heat
Mills 2012
Metabolism: Energy and Enzymes6.1 Energy
• Two laws of thermodynamics– Law of conservation of
energy• Energy cannot be created
or destroyed, only converted from one form to another
– Second law (Entropy)• Energy cannot be
converted from one form to another without a loss of usable energy
Energy = Mass x The Velocity of Light squared
Mills 2012
Metabolism: Energy and Enzymes6.1 Energy
• Entropy– A measure of randomness or disorder– Things tend toward more entropy – takes
energy to keep organized
Cells and Entropy
H+
H2O
C6H12O6
• more organized• more potential energy• less stable (entropy)
a.
Carbon dioxideand water
• less organized• less potential energy• more stable (entropy)
CO2
kineticenergy
channel protein
H+
H+
H+
H+
H+
H+
H+
H+H+
H+
H+
Unequal distributionof hydrogen ions
Equal distributionof hydrogen ions
• more organized• more potential energy
b.• less stable (entropy)
• less organized• less potential energy• more stable (entropy)
Glucose
H+
H+
H+H+
H+
H+
Mills 2012
Metabolism: Energy and Enzymes6.1 Energy
• Whole ecosystem also follows these rules– Ultimately all energy
ends up as heat, which is very random energy (high entropy)
Mills 2012
Metabolism: Energy and Enzymes6.2 Metabolic Reactions and Energy
Transformations• Metabolism = sum of all reactions that go on in body
– Free energy • = amount of energy (G) that is still available (free) to do work after a
chemical reaction has occurred. (change in energy is designated delta G)• If delta G is negative it means the products have less energy than the
reactants did. And the reaction will occur spontaneously– Exergonic – give off energy
• Delta G is negative• ATP ADP +P + free Energy
– Endergonic – need energy• Delta G is positive – products have more free energy than reactants.• Free Energy + Reactants Products
Mills 2012
Metabolism: Energy and Enzymes6.2 Metabolic Reactions and Energy
Transformations
• Coupled reactions– Many reactions in body are coupled
• One gives off energy and the other uses it
Mills 2012
Metabolism: Energy and Enzymes
6.2 Metabolic Reactions and Energy Transformations
• ATP; energy for Cells– Adenosine triphosphate is
a common source of stored energy for cells
– Provides energy for:• Chemical work –
synthesizing macromolecules
• Transport work – pumps substances across membranes
• Mechanical work – muscle contractions, cilia, flagella, cytoskeleton
– Energy stored in third phosphate bond
ATP is a nucleotide
Coupled Reactions
12
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1 2 3
P
Myosin assumes itsresting shape whenIt combines with ATP.
ATP splits into ADPand p , causingmyosin to change itsshape and allowing itto attach to actin.
Release of ADP andp cause myosin toagain change shapeand pull against actin,generating force andmotion.
ADPmyosin
actin
ATP
Mills 2012
Metabolism: Energy and Enzymes6.3 Metabolic Pathways and Enzymes
• Metabolic pathways– Series of consecutive reactions– Each step catalyzed by an enzyme
• Enzymes (organic catalysts) are made of proteins• Lower the activation energy
– Substance enzyme reacts with is called a substrate
Mills 2012
Mills 2012
Metabolism: Energy and Enzymes6.3 Metabolic Pathways and Enzymes
• Importance of Enzymes– Enzymes are needed for most chemical reactions to
occur in living cells, lower activation energy• Such as getting “energy” from sugars
– We would die without enzymes– Enzyme acts on a substrate– Enzyme names often end in “ase”– Enzymes are organic (usually globular proteins)
catalysts• Speed up a reaction without being used up themselves
– Can speed up a reaction by as much as a million times
Starch degradation by enzyme amylase animation ..\..\Biology\Biology Clipart Movies Animations Sounds\Biology movies\starch degrade animation.dir
Mills 2012
Metabolism: Energy and Enzymes6.3 Metabolic Pathways and Enzymes
• How Enzymes Work– Enzymes have active sites
• Enzyme-substrate complex
– Bind to specific spot on substrate
– Can put substrates together or break them apart
– Two theories to explain how• Lock and key• Induced fit
Mills 2012
Metabolism: Energy and Enzymes6.3 Metabolic Pathways and Enzymes
• Fit together like a lock and key
Hydrogen proxide
catalase
Water and oxygen
catalase
Degradation
Synthesis
Mills 2012
Metabolism: Energy and Enzymes6.3 Metabolic Pathways and Enzymes
• Induced fit– Once enzyme substrate complex has formed,
enzyme changes shape slightly for a better fit
Mills 2012
Metabolism: Energy and Enzymes6.3 Metabolic Pathways and Enzymes
Mills 2012
Mills 2012
Metabolism: Energy and Enzymes6.3 Metabolic Pathways and Enzymes
• Factors affecting ezymatic speed– Many factors can affect
enzyme action• Substrate concentration• Temperature• pH• Enzyme concentration• Enzyme inhibition• Enzyme co-factors
– Affect only the rate of the reaction, not the amount of end products
– Only very small amounts of enzyme are needed to catalyze reactions
The enzyme catalase (present in our liver) can break up 5 Million molecules of hydrogen peroxide in one minute (at Oo C = 32o F).
Mills 2012
Metabolism: Energy and Enzymes6.3 Metabolic Pathways and Enzymes
• Read Lab 2 – Enzyme Catalysis– Oct 14th lab – in your AP Lab Manual pg
Mills 2012
Metabolism: Energy and Enzymes6.3 Metabolic Pathways and Enzymes
• Temperature• Generally higher temp
increases rate of reaction
• In living tissues, don’t want high temp
• Enzymes work best at optimal temp
– Usually the normal temp of the cell they are in
• If temp too high enzymes are denatured
– Boiled egg
What is optimal temp for this enzyme in Fahrenheit degrees?
Formula: oF = (9/5) oC + 32
oF = (9/5) o42 + 32 = 107.6oF
Mills 2012
Metabolism: Energy and Enzymes6.3 Metabolic Pathways and Enzymes
• Enzyme and substrate concentrations– Increasing the amount of substrate or enzyme will
increase the reaction rate, but only up to a maximum point
Start
Fixed amount of substrate-add more and more enzyme.
Maximum point – adding more enzyme will not increase rate any more.
Mills 2012
Metabolism: Energy and Enzymes6.3 Metabolic Pathways and Enzymes
Start
Fixed amount of enzyme- add more and more substrate.
Maximum point – adding more substrate will not increase rate any more.
Mills 2012
Metabolism: Energy and Enzymes6.3 Metabolic Pathways and Enzymes
• pH– Enzymes also have an
optimal pH at which they work best
• Optimal pH for pepsin?• Where might you find
it?• Optimal pH of trypsin?
Mills 2012
Metabolism: Energy and Enzymes6.3 Metabolic Pathways and Enzymes
• Enzyme inhibition– Competitive
inhibition• Molecule binds and
blocks active site
Mills 2012
Metabolism: Energy and Enzymes6.3 Metabolic Pathways and Enzymes
• Enzyme inhibition– Non-competitive
inhibition• Molecule does not
bind to active site, binds to allosteric site
• Feedback inhibition (see next slide) works this way
Mills 2012
Metabolism: Energy and Enzymes6.3 Metabolic Pathways and Enzymes
• Feedback Inhibition– Many biological systems (metabolic
pathways)work this way
Mills 2012
Mills 2012
Metabolism: Energy and Enzymes6.3 Metabolic Pathways and Enzymes
• Enzyme cofactors– Some enzymes are not made
entirely of protein, contain other substances that help them function
• These are substances are called cofactors
– Can be inorganic (such as minerals Cu, Zn, Fe) or ,
– Can be organic- called coenzymes organic –non protein (such as vitamins)
– Some vitamins are coenzymes• Humans cannot synthesize most
vitamins, so need to take in diet
– Help enzyme perform it’s function
Mills 2012
Metabolism: Energy and Enzymes6.4 Organelles and the Flow of Energy
• Oxidation and Reduction– Occur together = redox– Oxidation = loss of electrons
• In living systems H often accompanies the electron (usually as e- + H+)
• So usually means loss of hydrogen atom
– Reduction = gain of electrons• In living systems H often accompanies the electron (usually as e-
+ H+)• So usually means gain of hydrogen atom
Mills 2012
Metabolism: Energy and Enzymes 6.4 Organelles and the Flow of Energy
• Two energy capturing pathways that use redox reactions (we will look at in the next two chapters)
– Photosynthesis – Ch 7– Cell respiration – Ch 8
• Both systems make use of an electron transport system and produce ATP
• We will look closer at these systems in chapters 7 and 8.
Mills 2012
Metabolism: Energy and Enzymes 6.4 Organelles and the Flow of Energy
• Photosynthesis overview– Takes energy from the sun and converts it
into chemical energy– Equation Summarizing Photosynthesis
• 6CO2 + 12H2O C6H12O6 + 6H2O + 6O2
Light
Mills 2012
Metabolism: Energy and Enzymes6.4 Metabolic Pathways and Oxidation
Reduction
• Photosynthesis overview– Many reactions involved– At one point, a coenzyme called NADP+, is
used to carry electrons from one place to another – usually to the ETS
NADP+ + 2e- + H+ NADPH
Mills 2012
Metabolism: Energy and Enzymes 6.4 Organelles and the Flow of Energy
• Cell Respiration Overview– Takes energy from glucose and makes ATP– Equation summarizing cell respiration
• C6H12O6 + 6H2O + 6O2 6CO2 + 12H2O + 36 ATP + heat
– Uses coenzyme NAD to carry electrons to ETS• NAD+ (is reduced) + 2e- + 2H+ NADH + H+
Oxidation
Reduction
Mills 2012
Metabolism: Energy and Enzymes 6.4 Organelles and the Flow of Energy
• Electron Transport System Overview– Series of carrier
molecules that pass electrons along
– Electrons lose a little bit of energy each time passed
– Carriers are oxidized and reduced
Mills 2012
Mills 2012
Metabolism: Energy and Enzymes 6.4 Organelles and the Flow of Energy
Will discuss in more detail later
Mills 2012
Metabolism: Energy and Enzymes6.4 6.4 Organelles and the Flow of Energy
• ATP Production Overview– Uses energy from ETS– ETS located within membranes of
mitochondria and chloroplasts– Process called chemiosmosis
• ETS deposits H on one side of the membrane• H flow down electrochemical gradient through
ATP synthase complex• Flowing through the complex provides the
energy to add a P to ADP ATP
Animations from http://www.cat.cc.md.us/courses/bio141/lecguide/unit4/metabolism/cellresp/etsch.html
Mills 2012
Metabolism: Energy and Enzymes 6.4 Organelles and the Flow of Energy
Peter Mitchell
1978 Nobel Prize
Chemiosmosis Theory
Chemiosmosis blah, blah blah, blah blah, blah blah,
blah blah, blah…..
Mills 2012
ATP synthesis and the electron transport chain animation
Mills 2012
Metabolism: Energy and Enzymes 6.4 Organelles and the Flow of Energy
• Chemiosmosis website animation– From: http://www.tvdsb.on.ca/westmin/science/sbioac/plan
ts/chemios.htm
Mills 2012
The End
Read Connecting the Concepts with the Big Ideas pg 115