Chapter 8 - energy and enzymes Flashcards
Where is energy stored in molecules ?
in the bonds
- covalent bonds have the most energy, then ionic, then hydrogen
creating bonds _____________ energy; breaking bonds __________ energy
requires; releases
what is the first law of thermodynamics
energy is neither created nor destroyed; it simply changes form
- mitochondria does not “make energy”, it transforms glucose into ATP
what is potential energy
energy stored in a position or configurationk
what is kinetic energy
energy in motion
which has more decreasing potential energy: non polar bonds or polar bonds
polar bonds
- non polar covalent bonds have the most potential energy
do lipids tend to have high or low potential energy
high potential energy
do carbs tend to have high or low potential energy
low (polar)
what is enthalpy
the total energy in a molecule
- includes potential energy in the bonds of the molecule plus the kinetic energy’s effect on pressure/volume of its surroundings (represented as H)
define exothermic
releases heat, change in H is negative
define endothermic
uptake of heat, change in H is positive
define entropy
the amount of disorder
what is the second law of thermodynamics
entropy always increases in a system that includes surroundings as well as the products of the reaction
What is Gibbs free energy
determines whether the reaction is spontaneous or requires added energy to be produced
what is gibbs free energy equation
ΔG = ΔH - (TΔS)
- H = change in enthalpy
- S = change in entropy
- T = temperature in degrees kelvin
- reactions are non spontaneous when ΔG is greater than 0
do spontaneous reactions have to happen quick?
no; they may take years (such as rusting)
when does entropy increase
when no energy is brought into a system
what is energetic coupling
when energy is released from an exergonic reaction and is used to power an endogenic reaction
- occurs through a transfer of electrons or transfer of a phosphate group (ADP to ATP)
what are redox reactions related to energetic coupling?
reduction - oxidation reactions that are non spontaneous
- oxidation: loss of electrons
- reduction: gain of electrons
what are ATP transfers relating to energetic coupling?
energy via phosphate groups (non-spontaneous)
- hydrolysis of ATP
phosphorylation coupled with endergonic reactions
define activation energy:
the amount of kinetic energy required to initiate a chemical reaction
- energy needed to reach a transition state
how does a higher temperature impact enzyme substrate collision
higher temperatures impact the collisions by creating more of them until the enzyme hits the optimal temperature
describe the transition state
high energy causing an immediate state of reactants during a chemical reaction that must be achieve for the reaction to proceed
- the more unstable the transition state, the higher the activation energy, the less likely a reaction is to proceed quickly
what do enzymes do?
bring substrates and active sites together; they lower the amount of activation energy needed to create a reaction
- enzymes are a catalyst
- does not make endergonic reactions exergonic
induced fit:
changed shape of the active site of an enzyme as the result of the initial weak binding of a substrate so it binds the substrate more tightly
What are the steps to enzyme activation
Initiation: substrate binds to the active site
Transition state Facilitation: interactions between the enzyme and substrate lower the activation energy
Termination: products have lower affinity for the active site and are released. Enzyme is unchanged after the reaction
Enzymes do not work alone, what are the other factors that impact enzymes
cofactors, coenzymes, and prosthetic groups
Describe cofactors
inorganic ions that reversibly interact with enzymes
describe coenzymes
organic molecules that reversibly interact with enzymes such as the electron carriers NADH
Describe prosthetic groups
atoms or non-amino acid molecules that are permanently attached to proteins such as retinal; retinal is involved in converting light energy into nerve impulses.
within enzyme functions, what do reactions depend on?
- substrate concentration
-enzyme affinity for substrate - specific environment (pH, temperature, CO2 levels)
- regulation: controlling when and where an enzyme will function
what are the two types of regulation?
reversible (non covalent): interactions that do not permanently affect enzymes primary structure
- competitive inhibition: molecules that compete for active sites
- allosteric regulation: molecules that bind to another location changing the shape of the enzyme
Covalent: irreversible changes to the primary structure due to peptide bonds or phosphorylation
