2:2

kinetics (speed of chemical reactions) are determined by

instability of the transition state between the reactants and products

activation energy

energy required to get from reactants to transition state

enzymes are

• proteins which speed up chemical reactions

• shaped to stabilize the structure of transition state

• reduce activation energy to speed up reactions (by stabilizing)

• not usually not permanently altered and can be reused over and over

a proteins enzymes folded 3D structure includes an active site where

its substrates (reactant of the chemical reaction) can bind and the reaction can be catalyzed

amino acids found at the active site

might not be next to each other in primary structure of a polypeptide

Temperature: Below → optimal

increase temp = increase reaction rate

• increase collision frequency/ force, enzyme dynamics

• increase energy to reach Ea

Temperature: Optimal → above

protein denatures, active site altered, rate drops dramatically

pH

• alters acidic/basic amino acids, prevents ionic bonds

• binding and catalytic amino acids affected

anabolic (biosynthetic) metabolism

• join small → larger molecules

• consume energy

catabolic (degradative) metabolism

• break down large → smaller

• release energy

metabolic reactions are organized into pathways that can be

linear, branching, or circular

competitive modulators

• similar shape to substrate compete for active site

• always inhibit enzyme because take space of substrate

• overcome by increase [substrate]

allosteric (non competitive) modulators

• bind away from active site (no comp) alter protein shape

• can increase or decrease enzyme activity depending on how it changes enzyme shape

• unaffected by [substrate]

enzymatic regulation balances metabolic supply and demand

changing concentrations of enzymes, substrates, and modulators can favor formation of different products from a metabolic pathway

negative feedback

products of a reaction or pathway inhibit an enzyme in the pathway, reducing production of the product

positive feedback

products of a reaction or pathway activate an enzyme in the pathway, increasing production of the product

energy

capacity to cause change (rearrange matter)

kinetic (movement)

heat: sum of molecular movement

potential (location/structure)

chemical energy: number, nature of bonds

more bonds, more energy

less bonds, less energy

Gibbs Free Energy

• measure of instability

• likelihood to change to a more stable state

• delta G = Gp - Gr

• delta G < 0 = spontaneous (energetically favorable, can occur without net energy input)

Exergonic

release energy

• Gr > Gp

• delta G < 0 (spont)

• catabolic

Endergonic

absorb energy

• Gr < Gp

• delta G >0 (non spont)

• anabolic

many metabolic reactions are reversible

• reactants can go in either direction

• one direction might be the more energetically favorable, “spontaneous” direction

closed systems move towards

equilibrium

Equilibrium (reaction rate forward = reaction rate reverse)

• no net change in [reactant] and [product]

• low energy/ stable state: delta G = 0 (energy min)

• add reactant/ remove product → make more product

  • requires an open system

Equilibrium = death

• no net change

• state of maximum stability

• minimum free energy, no work can be done

• achieved in isolated systems

• avoided in open systems

  • addition of reactants, removal of products

energy coupling

• coupling an exergonic reaction to an endergonic reaction

• favorable reaction provides energy to drive unfavorable

• ATP hydrolysis (exergonic reaction that drives many endergonic reactions

study ATP