chapter 8: an introduction to metabolism. metabolism = catabolism + anabolism catabolic reactions...
TRANSCRIPT
Chapter 8:Chapter 8:An IntroductionAn Introductionto Metabolismto Metabolism
• Metabolism = Catabolism + Anabolism
• Catabolic reactions are energy yielding involved in the break down of more complex molecules into simpler ones
• Anabolic reactions are energy requiring
• involved in the building up of simpler molecules into more-complex ones
• Bioenergetics-study of how organisms use their energy resources
Metabolism
11stst & 2 & 2ndnd Laws of Thermodynamics Laws of Thermodynamics
“Energy can be transferred or
transformed but neither created nor destroyed.”
“Every energy transfer or transformation increases the
disorder (entropy) of the universe.”
Note especially the waste heat
transform energy to new forms (1st law)
are less than 100% efficient (2nd law)
Organisms tend to use energy in a more organized fashion therefore requiring energy ( always fighting entropy)
Organisms as TransformersOrganisms as Transformers
• G-Free energy-energy that is available to perform work
• H- total energy (enthalpy) • S – entropy• ΔG = ΔH - T ΔS • If ΔG = negative, reaction is
spontaneous• If ΔG = positive, reaction needs energy
Free energy change- Free energy change- ΔΔGG
Metabolic Reactions
• Exergonic reaction- releases energy so G decreases and ΔG is negative
• Endergonic reaction- absorbs free energy so G increases and ΔG is positive
Exergonic ReactionsExergonic Reactions
Energy released
“Food”
KNOW THIS CHART!
Endergonic ReactionsEndergonic Reactions
Energy required
“Work”
KNOW THIS CHART!
Cells do different kinds of work
Mechanical- muscles
Transport- cell membrane
Chemical- endergonic reactions
Summary of Metabolic CouplingSummary of Metabolic Coupling
Exergonic processes drive Endergonic processesATP is an agent of energy coupling
It is created by one process and is used in another!
Adenosine Triphosphate (ATP)
http://www.bozemanscience.com/atp-adenosine-triphosphate
Cellular work is always powered by ATP Cellular work is always powered by ATP
• Hydrolysis releases 7.3 kcal of energy per mole ATP
• Can heat the environment (keep us warm)
• ATP is renewable
• Catalysts speed up a reaction without being consumed
• An enzyme is a catalytic protein
• Catalysts reduce activation energy- energy needed to get a reaction going
Enzymes
KNOW THIS CHART !!!!KNOW THIS CHART !!!!
Enzymes lower activation
energy
Catalysis as Viewed in 3D
Active site is site of catalysis
Substrate is reactant that the enzyme works on
Induced Fit- used to beCalled “lock and key”
Enzymes and substrate brought into position for optimum interaction
• Temperature- increases enzyme action until it denatures
• pH 6-8 depending on environment or organ
• Cofactors- non-protein helpers (minerals)
• Coenzymes- vitamins
Environmental Factors and Enzymes
Each Enzyme has Opt. Temp and pHEach Enzyme has Opt. Temp and pH
Denatured?
Optimal pH of most
enzymes fall in 6-8 range
Competitive Enzyme Inhibitors
• resembles the substrate and bonds to active site, blocking it
• Is reversible by increasing substrate concentration
Noncompetitive Enzyme Inhibitors
• Binds to another site (allosteric site) not the active site
• Changes shape of protein so it can no longer function
• Toxins and Poisons- sarin, DDT
• Sarin (nerve gas ) attaches to acetylcholine- important nervous system enzyme
• DDT• Antibiotics blocks
active sites of bacterial enzymes
Negative Effects of Inhibition Negative Effects of Inhibition
• Not all inhibitors are bad. • Some are used to
regulate enzyme activity
• Can activate or inhibit enzyme
• Example-speeding up or slowing down of ATP production
Allosteric Regulation of Enzymes
Feedback Inhibition Pathway
is
switched
off by the
binding
of the
product to
the
allosteric site
ATP Feedback Inhibition