Bio ch7- Metabolism: Energy, Enzymes

Bioenergetics

study of energy flow through a living system

Metabolism

• all chemical reactions of a cell or organism

• Metabolism = anabolic reactions + catabolic reactions

metabolic pathway

series of biochemical reactions that converts 1+ substrates into final product

2 types of metabolic pathways

1. anabolic

2. catabolic

anabolic reaciton

• smalll molecules made into larger ones

• energy is required (reactant side)

catabolic reaction

• larger moecules broken into smaller ones

• energy is released (product side)

energy

ability to do work

2 types of energy

1. KE → motion

2. PE → stored

Gibb’s freee energy

• amount of energy available to do work

• ΔH = change in total energy of system

• ΔS = change in entropy

exergonic reactions

• energy is released

  • ΔG < 0

• spontaneous → occur without added energy

• products < reactants (free energy)

• water is on reactant

endergonic reacitons

• require input of energy

  • ΔG > 0

• products > reactants (free energy)

• water is on products

activation energy

• energy required for reaction to proceed

• lets reactants unstable → bonds broken → transition state (reaction occurs fast)

when a reaction is catalyzed, the activation energy is

lower

thermodynamics

study of energy and energy transfer involving physical matter

first law of thermodynamics

energy cannot be created or destroyed

second law of thermodynamics

• transfer of energy is not complete

  • energy is lost

entropy

measure of randomness/disorder

what provides the energy for cell’s endergonic reactions?

hydrolysis of ATP

ATP structrue

Adenosine backbone (adenine + ribose) + 3 phosphate groups

phosphate groups in order (furthest from ribose sugar)

alpha, beta, gamma

ATP equation

ATP + H2O → ADP + Pi + (-ΔG)

ATP hydrolysis

• ATP hydrolyzes quickly because it is unstable

• reversible

sodium-potassium pump

• 3 Na+ out

• 2 K+ in

enzymes

• protiens that speed up reactions by lowering activaition energy

• are specific because of its 3D shape

substrates

reactants

induced fit

• active site shifts a little in shape to optimize reactions

• slight changes → maximizes catalysis

• “lock-and-key” model

2 parts of active site

1. binding site: binds and orientates substrates

2. catalytic site: reduces chemicals activaiton energy

how does an enzyme help the substrate reach its transiiton state (4)

1. position 2 substrates so they are aligned for reaction

2. provide optimal enviornment → acidic or polar

3. contort/stress → less stable = more likley to react

4. temporarily react with substrates → chemically change it to make it less stable

how can enzymes be regulated (4)

1. modifications to temperature and/or pH

2. make molecules that inhibit/promote enzyme function

3. availability of coenzymes or cofactors

4. compartamentalized

2 types of enzyme inhibition

1. competitive inhibition

2. noncompetitive inhibition

competitive inhibition

• binds to active site

• competes with substrate for active site

• slow but DOES NOT affect the maximal rate

noncompetitive inhibition

• binds to enzyme

• causes slower reaction since it binds to enzyme at different location

• slow but DOES affect maximal rate

maximal rate

speed of a reaction when substrate is not limited

allosteric inhibitors

• modify the acitve site of the enzyme so that the substrate that binds to it is reduced or prevented

• decrease enzyme activity

allosteric activators

• modify the active site of the enzyme so that the need for the substrate increases

• increase enzyme activity

cofactors

inorganic ions

coenzymes

organic molecules

feedback inhibition

• end-product of the pathway inhibits an upstream step

• how cells self-regulate