BIS 102 L1: Review of Bioenergetics and Into to Metabolism

Learning objectives: Review thermodynamics and enzyme action from BIS 102 1. Explain how entropy increases even when cells are creating complex, ordered molecules like proteins and nucleic acids

If nature proceeds towards disorder (2nd law of thermodynamics) how does a cell make complex ordered molecules like proteins?

Total entropy of the universe is continuously increasing

System

reactants, products, immediate atmosphere

Universe

system + surrounding

Isolated

system exchanges neither matter nor energy w/ surroundings

Closed

system exchcanges energy (not matter with surrounding)

Open

exchanges energy & matter to everyone

Potential Energy

nutrients in environment (complex molecules such as sugars, fat)

sunlight

Energy transductions accomplish work

cellular work:

• chemical synthesis

• mechanical work

• osmotic and electrical gradients

• light production

• genetic information transfer

Catabolism

makes compounds simpler, entropy increases
(exergonic)

Anabolism

makes complex molecules, entropy decreases
(endergonic)

Living organisms are _____ systems.

open

T/F The reaction in our cells are at equilibrium.

False, equilibrium is the rate of forward & reverse reaction being the same

no net change in [react] and [product]

In closed systems, chemical reactions proceed ___________ until equilibrium is _____________.

spontaneously, reached

*goal is to reach equilibrium

What system are humans?

dynamic steady state (homeostasis)

What is the delta G of a rxn?

-delta G = spontaneous, exogonic

+delta G = nonspontaneous, endogonic

What is the delta G equation?

delta G = delta G’naught + RT ln [P]/[R]

Do enzyme change delta G or Keq?

No, but increases the rate of reaction (thermodynamics) towards either direction (catalyst)

How do enzymes act as a catalyst?

lowers EA → delta G

faster rate

delta G unaffected

metabolism

sum of all chemical transformation taking place in a cell/organism

pathways

sequence of consecutive rxns

product → reactant

small chemical changes in between

What are some examples of anabolism?

Precursor molecules → Cell macromolecules

amino acids → proteins

sugars → polysaccharides

fatty acids → lipids

nitrogenous bases → nucleic acids

Types of non-linear pathways

converging

diverging

cyclic