Chapter 8. Introduction to Metabolism Flashcards
Exergonic Reaction
A net release of free energy. Delta G is negative. (G is product and -G is the reactant)
Endergonic Reaction
Rxn that absorbs free energy from its surroundings. Stores energy. Delta G is positive.
Activation energy
The amount of energy necessary to push reactants over the transition state.
- At the summit molecules are at an unstable point, which is the transition state.
- The difference between free energy of the products ad free energy of the reactants is the Delta G.
Catalysts
Lower activation energy of reactants.
- speed up chemical reactions.
- most cellular catalysts are proteins called enzymes.
- If a protein ends in -ase, its usually an enzyme.
How do enzymes speed up reactions?
By lowering Ea (Activation energy)
-The transition state can be reached even at the moderate temperatures.
Do enzymes change Delta G?
No. Enzymes do not change Delta G.
- They hasten reactions that would eventually occur.
- Because enzymes are selective, they determine which chemical process will occur at any time.
Are enzymes efficient catalysts?
Yes.
ex) 2H2 -> O2->2H2
Are enzymes substrate specific?
Yes.
- A substrate is a reactant which binds an enzyme.
- The active site of an enzyme is typically a pocket or groove on the surface of the protein in which the substrate fits.
Enzyme Substate recongition
Open/Closed form. Protein flexibility participates in enzyme substrate interaction.
Primary Structure
All covalent bonds
peptide bonds = strong covalent bonds.
Secondary Structure
A) Alpha helix
B) Beta sheers.
What are the consequences of week bonds?
- Proteins are very flexible.
- Shapes can change reversibly.
- “on” shape = functional protein
- “off” shape = non functional protein.
- covalent peptide bond holds protein together despite shape change.
Cellular work
A cell does three main kinds of work which are mechanical work, transport work, and chemical work.
Mechanical work
- beating of cilia.
- contraction of muscle.
- movement of chromosomes.
Transport Work
- pumping substances across membranes against the direction of spontaneous movement.
- moving vesicles from ER to golgi.
