Biology Notes (Exam Guide 7)

metabolic pathways

begin with a specific molecule and end with a product

- emergent property of life, regulated to maintain homeostasis

- it’s a series of chemical reaction, each involves energy transformation (each step is catalyzed by a specific enzyme

anabolic pathways

• synthetic, making bonds requires energy

• simple molecules which become complex molecules

- ex: synthesis of protein from amino acids

catabolic pathways

• breaks bonds, release energy 

• complex molecules which become simple molecules

- ex: cellular respiration

energy 

• capacity to cause change/ do work 

- movement of matter 

• two types: kinetic energy and potential energy 

kinetic energy

the energy of motion

potential energy

stored energy, has not been used yet

thermodynamics

study of energy transformations

• two laws:

1. energy cannot be created nor destroyed, only converted from one form to another - principle of conservation of energy

- ex: food which is chemical energy + heat

2. every energy transfer or transformation increases entropy in the universe 

- entropy is the measure of disorder, randomness not usable -- disperse into environment 

- ex: heat released during respiration 

light energy

• comes from the sun enters on ecosystem and heat energy exists

- energy conversion is never 100% efficient

- the total energy in the universe is constant

- total energy available to do work decreases

Gibbs free energy

the energy available to do work

- cannot be measured but we can see how free energy changes during a reaction

- change in energy = delta G

- if delta G is less than 0 than energy is released from reaction

- if delta G is greater than 0 than energy is added to cause a reaction, non spontaneous

- if delta G is equal to 0 than chemical processes at equalibrium

exergonic

• - delta G energy released spontaneously 

endergonic

• + delta G energy stored requires energy

cells use ATP to carry energy, its structure is

• ribose (5-C sugar) , adenine (Nitrogen base), and 3 phosphate group

- coupled reactions pair endergonic reaction (requires energy) with exergonic reaction (provides energy)

• ATP drives endergonic reactions by phosphorylation, phosphate group transferred to molecule, molecule now now shape

- reactant now = phosphorylated intermediate

enzymes speed up reactions by lowering energy barriers 

 

activation energy

the initial energy needed to start a reaction

active site

cleft or groove for substrate binding

substrate

reactant that an enzyme acts upon

- change of shape , facilitates breaking of bonds

induced fit

• enzyme changes shape after binding substrate for better fit, facilitates breaking/ forming bonds