Lecture 7 - Intro. to Metabolism and Energy Flashcards
What is metabolism?
the totality of an organisms chemical reactions, managing the materials and energy resources of the cell
What is anabolism?
- reactions that require energy to organize the cell
- ADP is recycled for catabolic reactions
- DNA replication
What is catabolism?
- reactions that release energy from the breakdown of nutrients
- ATP from these reactions drive the energy needs of anabolic reactions
What are energy and work?
energy = capacity to cause or the capacity to do work, that is the capacity to change or move something work = a force acting on an object over a distance
What are the two main energy types?
potential = stored energy due to position or composition kinetic = energy due to movement
What are the laws of thermodynamics?
- study of energy transformations
- 1st law = energy cannot be created or destroyed, can only be converted/transformed from one form to another
- 2nd law = entropy of the universe is always increasing (reactions will be spontaneous if the disorder of the system is increased, the system will become more stable)
What is free energy?
- portion of a system’s energy that is available to perform work
What happens if the free energy is negative?
- spontaneous reactions
- exergonic
- energy released
- catabolic
- ex) cellular respiration
What happens if the free energy is positive?
- non-spontaneous reactions
- endergonic
- requires energy
- anabolic
- ex) photosynthesis
What is energy coupling?
- energy from exergonic reactions are used to power endergonic reactions
- sodium/potassium pump
What is ATP?
- the cellular energy currency
- ATP = adenosine triphosphate
- major source of energy in cells
- contains potential energy due to position and composition
- hydrolysis of these bonds release energy (exergonic)
- ATP -> ADP + Pi,
- free energy = -13 kcal/mol under cellular conditions and therefore hydrolysis of ATP to ADP can do 13kcal of work
What are enzymes?
- biological catalysts that provide an alternative energy path for a reaction to proceed with a low activation energy
- function in both exergonic and endergonic reactions
- highly regulated in the cell
- lower activation energy barrier necessary for reactions to occur without changing the free energy
- catalytic protein that speeds up a reaction without being consumed
- end in “-ase”
Do enzymes change the free energy?
NO
How do enzymes work?
- bind and act on substrates
- very specific to their substrate
- have an active site
- catalytic site (active site) has geometric and chemical compatibility with the substrate
What is Catalysis?
- often proceeds by induced fit
- slight change in enzyme shape to accommodate substrate
- reactants converted to products
- enzyme is unchanged by reaction and can be reused
How can enzymes lower the activation energy?
1) bring reactants closer together
2) active site contains a unique chemical environment favorable for a reaction
3) physically stress bonds to be broken
4) covalently stabilize reaction intermediate
5) place substrates in the correct orientation
What is enzyme inhibition?
- certain chemical selectively inhibit the action of specific enzymes
What are the types of enzyme inhibitors?
- competitive = binds the active site but does not participate in a reaction, can be outcompete by an increase in the substrate
- non-competitive = binds the site on the enzyme that is no the active site and block enzyme activity
