Lecture 10 + 11 : Enzymes Speeding up Chemical Reactions Flashcards
Metabolism
the totality of an organism’s chemical reactions
what does a metabolic pathway start and end with?
with a specific molecule and ends with a product
how do catabolic pathways release energy?
by breaking down complex molecules into simpler compounds
what is an example of a catabolic pathway?
Cellular respiration, the breakdown of glucose in the presence of oxygen
why do anabolic pathways consume energy?
to build complex molecules from simpler ones
what is an example of an anabolic pathway?
The synthesis of protein from amino acids is an example of anabolism
energy
capacity to cause change
kinetic energy
motion energy
heat (thermal energy)
kinetic energy associated with random movement of atoms or molecules
potential energy
energy that matter possesses because of its location or structure
Chemical energy
potential energy available for release in a chemical reaction
free energy
a portion of the system’s energy that can do work when temperature and pressure are uniform, as in a living cell
Free energy equation
∆G = G final state - G initial state
∆G = ∆H -T∆S
how do you know if a certain process is spontaneous or not?
-∆G
how do spontaneous processes occur?
without energy input; they can happen quickly or slowly
exergonic reaction
proceeds with a net release of free energy and is spontaneous
endergonic reaction
absorbs free energy from its surroundings and is nonspontaneous
what are the three types of cellular work that are nonspontaneous/endergonic
mechanical, transport, and chemical
energy coupling
the use of an exergonic process to drive an endergonic one (Overall, the coupled reactions are exergonic)
what is the most common example of energy coupling?
ATP hydrolysis
ATP’s structure is made up of?
ribose (a sugar), adenosine (a nitrogenous base), and three phosphate groups
How does the hydrolysis of ATP make a coupled endergonic reaction possible?
- hydrolysis breaks the bonds between the phosphate groups
- Energy is released from ATP when the terminal phosphate bond is broken
- release of energy comes from the chemical change to a state of lower free energy, not from the phosphate bonds themselves
how is ATP regenerated?
- regenerated by addition of a phosphate group to adenosine diphosphate (ADP)
- The energy to phosphorylate ADP comes from catabolic reactions in the cell
what can thermodynamics predict?
predicts if a reaction can occur spontaneously without input of outside energy (negative ΔG) or not
catalyst
a chemical agent that speeds up a reaction without being consumed by the reaction
enzyme
catalytic protein
activation energy (free energy of activation)
initial energy needed to start a chemical reaction
How do enzymes lower activation energy?
- increasing concentrations of substrates at active site of enzyme
- do not affect the change in free energy (∆G); instead, hasten reactions that would occur eventually
substrate
The reactant that an enzyme acts on
what is an enzyme substrate complex?
the location where the enzyme binds to the substrate
active site
the region on the enzyme where the substrate binds
how can the active site lower an activation energy barrier?
-Orienting substrates correctly
- Straining substrate bonds
- Providing a favorable microenvironment
- Covalently bonding to the substrate
what can an enzymes active site be affected by?
- General environmental factors, such as temperature and pH
- Chemicals that specifically influence the enzyme
cofactors
nonprotein enzyme helpers (vitamins or minerals)
examples of cofactors
- Cofactors may be inorganic (such as a metal in ionic form) or organic
what is an organic cofactor called?
-coenzyme (loosely bound)
- prosthetic group (tightly bound to an enzyme)
- coenzymes include vitamins
competitive inhibitors
bind to the active site of an enzyme, competing with the substrate
Noncompetitive inhibitors
bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective
how is enzyme activity regulated?
by switching on or offthe genes that encode specific enzymes or by regulating the activity of enzymes
How does allosteric regulation work?
- Regulatory molecules bind to enzymes somewhere other than the active site to turn them on or off
- when a regulatory molecule binds to a protein at one site and affects the protein’s function at another site
- most enzymes with this regulation are made from polypeptide subunits
feedback inhibition
- the end product of a metabolic pathway shuts down the pathway
- Feedback inhibition prevents a cell from wasting chemical resources by synthesizing more product than is needed
