chapter06 metabolism to be taught
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TRANSCRIPT
INTRODUCTION TO METABOLISM
• Metabolism = the totality of an organisms chemical processes
• Inside cells thousands of chemical reactions occur within microscopic spaces
• Metabolism is concerned with the management of energy and chemical resources of the cell
• Pathways that build up complex compounds are called Anabolic
• Pathways that breakdown complex compounds are called Catabolic
• Often these complimentary reactions are paired
Energy
• Energy is the capacity to do work
• Kinetic energy is the energy of things in motion
• Potential energy is energy of non-moving matter; by virtue of its location or arrangement
• Energy can be converted from one form to another
Thermodynamics
• Thermodynamics is the study of energy transformations
• 1st Law of Thermodynamics = Energy cannot be created or destroyed
• 2nd Law of Thermodynamics = Every energy transfer or transformation increases the entropy (disorder) in the universe
Free Energy
• Free energy is the portion of a system’s energy that can perform work when temp. is uniform throughout the system. Ex In a living cell
• Delta G = Delta H - T Delta S : This is the free energy equation; This term is very important it determines whether reactions will “go” in systems
Free Energy Cont.
• Delta G = Delta H - T Delta S ( a triangle represents delta)
• Delta means “change in”
• G = G final state - G initial state
• T = C + 273
• S = entropy
• H = system’s total energy
Reactions in Biological Systems
• Chemical reactions are classified by their free energy status
• Exergonic reactions = proceed with a net release of free energy
• Endergonic = absorb energy from the environment. They need to be provided “power” to run
• Ex Breakdown of glucose exergonic but photosynthesis is endergonic
ATP and Cellular work
• ATP is a nucleoside that the cell uses to power the cell. It is the main energy currency of cells.
• ATP is composed of an adenine, a ribose, and PO4 group: the tri PO4 tail is unstable
• The bonds can be broken by hydrolysis
• The terminal phosphate is most unstable, when removed it yields - ( negative) 7.3 kcal of energy.
ATP Cont.
• Negative delta Gs mean the reaction is exergonic ( gives off energy)
• Positive delta Gs mean the reaction is endergonic ( needs energy to go)
• The cell can couple reaction yielding and needing ATP to make complex biochemical pathways go.
• ATP is a renewable resource it is recycled
Enzymes
• Most chemical reactions would occur too slowly in bio systems because the temps are fairly low
• Enzymes are chemical agents that change the reaction rate without being consumed or converted in the reaction process
• Enzymes speed reactions by lowering the activation energy
Enzymes cont.
• Enzymes are very specific
• Enzymes are proteins
• Chemical reactions involve bond a making and breaking
• The initial energy necessary to start the reaction is called activation energy
• Enzymes can “ recognize” their substrates WHY?
Enzymes Cont.
• The active site of an enzyme is the pocket where it attaches to the substrate
• Substrate------Product ( Enzyme) ; cofactors = helpers
• Factors affecting enzyme function and stability– Temp– pH– Salinity
Inhibitors
• Enzyme inhibition– Competitive = bind to active site– Non-competitive = bind to another area
Metabolic Control
• Not all metabolic pathways are simultaneously activated
• Feedback inhibition control is most common = pathway is turned off by a specific concentration of the end product