An Introduction to Metabolism A.P. Biology Chapter 8 Mr. Knowles Liberty High School.
Chapter 8: An Introduction To Metabolism
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Transcript of Chapter 8: An Introduction To Metabolism
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2.a.1 – All living systems require constant input of free energy (8.1-8.3).
4.b.1 – Interactions between molecules affect their structure and function (8.4 & 8.5).
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The totality of an organism’s chemical processes
Concerned with managing the material and energy resources of the cell
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Pathways that break down complex molecules into smaller ones, releasing energy
Example: Cellular respiration DOWNHILL!
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Pathways that consume energy, building complex molecules from smaller ones
Example: Photosynthesis, condensation synthesis
UPHILL!
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Energy cannot be created or destroyed
It can be converted from one form to another
The sum of the energy before the conversion is equal to the sum of the energy after the conversion
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Some usable energy dissipates during transformations and is lost
During changes from one form of energy to another, some usable energy dissipates, usually as heat
The amount of usable energy therefore decreases
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Ability to do work The ability to rearrange a collection of
matter Forms of energy:
› Kinetic› Potential› Activation
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Kinetic: › Energy of action or motion› Ex: heat/thermal energy
Potential: › Stored energy or the capacity to do work› Ex: chemical energy
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Energy needed to convert potential energy into kinetic energy
Potential Energy
Activation Energy
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The portion of a system's energy that can perform work
Known as ΔG
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ΔG = Δ H - T Δ SΔ = change (final-initial)ΔG = free energy of a systemΔH = total energy of a system
(enthalpy)T = temperature in oKΔS = entropy of a system
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If the system has:› more free energy=less stable (greater
work capacity)› less free energy=more stable (less
work capacity)› As rxn moves towards equilibrium, ΔG
will decrease
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These are the source of energy for living systems
They are based on free energy changes Two typesTwo types: exergonic and endergonic
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Exergonic: › chemical reactions with a net
release of free energy› Ex: cellular respiration› - ΔG , energy out, spontaneous
Endergonic: › chemical reactions that absorb
free energy from the surroundings› Ex: Photosynthesis› + ΔG , energy in, non-spontaneous
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- ΔG +ΔG
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Couples an exergonic process to drive an endergonic one
ATP is used to couple the reactions together
Types:Types: mechanical, transport, chemical
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AAdenosine TTripphosphate Made ofMade of::
1. Adenine (nitrogenous base)2. Ribose (pentose sugar)3. 3 phosphate groups*
*bonds can be broken to make ADP
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Three phosphate groups and the energy they contain
Negative charges repel each other and makes the phosphates unstable› Tail is unstable = more free energy = more
instability Works by energizing other molecules by
transferring phosphate groups Hydrolysis of ATP = free energy is
released as heat (can be adv or not adv)
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Energy released from ATP drives anabolic reactions
Energy from catabolic reactions “recharges” ATP
Very fast cycle
› 10 million made per second
Coupled RXN
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Takes place in cytoplasm and mitochondria
Using special process called substrate-level phosphorylation› Energy from a high-
energy substrate is used to transfer a phosphate group to ADP to form ATP
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Biological catalysts made of protein Speeds up rxn without being consumed Cause the speed/rate of a chemical rxn
to increase› By lowering activation energy
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AB + CD AC + BD*AB and CD are “reactants”*AC and BD are “products”*Involves bond forming/breaking*Transition state: can be unstable
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Unstable state
Energy is released as heat
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Lower the activation energy for a chemical reaction to take place
Why do we need enzymes?› Cells can’t rely on heat to kick start rxns› Why? Denaturation, heat can’t decipher
between rxns› Enzymes are selective! Can only operate
on a given chemical rxn
Intro to
Enzy
mes movie
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SubstrateSubstrate – – › the material the enzyme works on
Enzyme namesEnzyme names: : › Ex. Sucrase› “- ase” name of an enzyme› 1st part tells what the substrate is (i.e.
Sucrose)
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Some older known enzymes don't fit this naming pattern
Examples: pepsin, trypsin
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The area of an enzyme that binds to the substrate
Structure is designed to fit the molecular shape of the substrate
Therefore, each enzyme is substrate specific
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Enzyme + Enzyme-Enzyme +
Subtrate Sub complex Product
Notice: Complex becomes product, but enzyme stays the same! Enzyme is NOT CONSUMED!
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1. Lock and Key model2. Induced Fit model
Reminder:Reminder: Enzymes and substrates are usually held together by weak chemical interactions (H/ionic bonds)
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Substrate (key) fits to the active site (lock) which provides a microenvironment for the specific reaction
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Substrate “almost” fits into the active site, causing a strain on the chemical bonds, allowing the reaction
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Usually specific to one substrate Each chemical reaction in a cell requires
its own enzyme Don’t change during rxn Always catalyze in direction towards
equilibrium
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1) Active site is template for enzyme2) Enzymes may break/stretch bonds
needed to be broken/stretched3) Active site is microenvironment4) Active site directly participates in
chemical rxn
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Environment Cofactors Coenzymes Inhibitors Allosteric Sites
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Factors that change protein structure will affect an enzyme.
Examples:› pH shifts (6-8 optimal)› Temperature (up, inc activity)› Salt concentrations
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Cofactors:Cofactors:› Non-proteinNon-protein helpers for catalytic
activity› Examples: Iron, Zinc, Copper
Coenzymes:Coenzymes:› Organic molecules that affect
catalytic activity› Examples: Vitamins, Minerals,
usually proteins
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CompetitiveCompetitive › mimic the substrate and bind to the
active site (compete for active site)› Toxins/poisons – Ex: DDT› Can be used in medicine – painkillers,
antibiotics Noncompetitive
› bind to some other part of the enzyme› Causes active site to change shape
Inhibitor video
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Identify forms of energy and energy transformations. Recognize the Laws of Thermodynamics. Recognize that organisms live at the expense of free
energy. Relate free-energy to metabolism. Identify exergonic and endergonic reactions. Identify the structure and hydrolysis of ATP. Recognize how ATP works and is coupled to metabolism. Recognize the ATP cycle Relate enzymes and activation energy. Recognize factors that affect enzymes specificity and
enzyme activity.. Recognize factors that control metabolism.