Chapter 8 Intro To Metabolism

cell respiration

cell respiration: extracts energy. stored in sugar and other fuels

metabolism

  • totality of an organisms chemical reactions
  • emergent property
  • metabolic pathway: begins with a specific molecule and ends with a product

pathways

  • catabolic pathways: release energy by breaking down complex molecules into simpler compounds
  • anabolic pathways: consumes energy to build complex molecules from simpler ones

biogenetics

  • biogenetics: study of how energy flows through living systems

energy

  • energy: capacity to cause change
  • can be converted from one form to another
  • kinetic energy: energy associated with motion
  • thermal energy: random movement of atoms or molecules
  • heat: thermal energy in transfer between objects
  • potential energy: energy matter possess based on location/structure
  • chemical energy: potential energy waiting to be released in a chemical reaction

laws of energy transformation

  • thermodynamics: study of energy transformations
  • isolated system: liquid in a thermos, unable to exchange energy ot matter with its surroundings
  • open system: energy and matter can be transferred
  • organisms are open systems

  ==first law of thermodynamics==

  • energy of the universe is constant
  • cant be created or destroyed
  • aka principle of conservation of energy

  @@second law of thermodynamics@@

  • some energy is unusable and is often lost as heat
  • every energy transfer increases the entropy of the universe
  • entropy: measure of molecular disorder, randomness
  • spontaneous process: occur without energy input; they can happen quickly or slowly
  • non spontaneous processes decrease entropy; occur only if energy is provided

biological order and disorder

  • organisms create ordered structures from less organized forms of energy and matter
  • organisms can also replace ordered forms of matter and energy in their surround with less ordered forms
  • ex: animals consume complex molecules in their food and release smaller, lower energy molecule and heat into their surroundings

free energy

  • free energy: energy that can do work when the temperature and pressure are uniform
  • measure of a systems instability, tendency to change to a more stable state
  • change in free energy; delta G
  • spontaneous change- free energy decreases
  • equilibrium: state of maximum stability
  • a process is spontaneous and can perform work only when it is moving toward equilibrium

free energy and metabolism

  • exergonic reaction: net release of free energy and is spontaneous
  • endergonic reaction: absorbs free energy from its surroundings and is non spontaneous

equilibrium and metabolism

  • reactions in a closed system eventually reach equilibrium and then can do no work
  • cells are not in equilibrium: open systems experiencing a constant flow of materials
  • our metabolism is never at equilibrium
  • catabolic pathway in a cell releases free energy in a series of reactions

ATP

  • cell does 3 main types of work
  • chemical work: pushing endergonic reactions
  • transport work: pumping substances against the direction of spontaneous movement
  • mechanical work: such as contraction of muscle cells
  • energy coupling: use of an exogenic process to drive an endergonic one
  • most energy coupling is used by atp

composed of

  • ribose (sugar)
  • adenine (a nitrogenous base)
  • three phosphate groups

how does atp hydrolysis perform work?

  • hydrolysis of ATP makes ADP (adenosine diphosphate)
  • from exergonic to endergonic reaction
  • phosphorylation: transfer of a phosphate group to some other molecule, like a reactant
  • phosphorylated intermediate: recipient molecule
  • transport and mechanical work in the cell are powered by atp hydrolysis
  • leads to a change in protein shape and binding ability

regeneration of atp

  • renewable source that is regenerated by addition of a phosphate group to ADP
  • energy comes from the catabolic reaction in the cell
  • ATP cycle is a revolving door through which energy passes during its transfer from catabolic to anabolic

 

enzymes

  • enzyme: catalytic protein
    • ex. sucrase catalyzes the hydrolysis of sucrose (helps facilitate the split)

    enzymes activity can be affected by

  • general environmental factors, like pH and temperature
  • chemicals that specifically influence the enzyme
    • catalyst: any chemical agent that speeds up a reaction without being consumed by the reaction.
    • catalysis: enzymes or other catalysts speed up specific reactions by lowering the activation energy barrier.
    • optimal temperature: the temperature at which a procedure is best carried out
    • optimal pH: the pH at which a procedure is best carried out

activation energy barrier

  • activation energy: initial energy needed to start a chemical reaction (free energy of activation)
  • often supplied in the form of thermal energy that the reactant molecules absorb from their surroundings.

substrates specificity of enzymes

  • substrate: the reactant that an enzyme acts on
  • enzyme-substrate complex: the enzyme binds to its substrate
  • active site: region on the enzyme where the substrate binds
  • induced fit: brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction
  • fast acting and emerge from reactions in their original form.
substrate bonds to enzyme which changes its shape and creates reaction productsprocess of enzyme-substrate complex
  1. substrate enters active site
  2. substrates are held in active sire by weak interactions
  3. the active site lowers activation energy
  4. substrates are converted to products
  5. products are released
  6. active site is available for new substrates
  7. process starts over

catalysis

active site can lower activation energy barrier by covalently bonding to the substrate

  • the rate of reaction can be sped up by increasing substrate concentration
  • if enzyme is saturated, the reaction rate can only be sped up by adding more enzymes

cofactors

nonprotein enzyme helpers

  • coenzymes: an organic cofactor; includes vitamines
  • competitive inhibitors: binds to the active sire of an enzyme, competing with the substrate
  • noncompetitive inhibitors: binds to another part of an enzyme, causing the enzyme to change shape and making the active site less effective

  ## regulation of enzyme activity helps control metabolism

  • if a cells metabolic pathways were not tightly regulated, chemical chaos would result
  • a cell does this by switching on or off the genes…

    ## allosteric regulation

  • inhibit/stimulate an enzymes activity
  • occurs when a regulatory molecule binds to a protein at one site and affects the protein’s function at another site.
  • made from polypeptide subunits

cooperativity

  • form of allosteric regulation that can amplify enzyme activity

feedback inhibition

  • the end product of a metabolic pathway shits down the pathway
  • prevents a cell from wasting chemical resources by synthesizing more product than is needed.