5.1 Energy Transformation and Metabolism Flashcards
What is cellular metabolism?
sum of all the chemical reaction that occur in a cell
What is a significant part of cellular metabolism?
involves the breaking down and the building up of molecules
What is catabolism?
the breaking down of molecules
What is anabolism?
the building up (synthesis) of molecules
What are reactants in a chemical reaction?
substances that participate in a reaction
What are products in a chemical reaction?
substances that form as a result of a reaction
How do you know if a reaction will proceed in the indicated direction?
using the concept of entropy, it is possible to state that a reaction will occur if it increases the entropy of the universe
HOWEVER, in cell biology, we d o not usually wish to consider the entire universe; we simply want to consider a particular reaction
therefore, cell biologists use the concept of free energy instead of entropy
What is free energy (△G)?
amount of energy available, that is, energy that is “free” to do work after a chemical reaction has occurred
How is the change in free energy after a reaction occurs calculated?
by subtracting the free energy content of the reactants from that of the products
What does a negative result when calculating the change in free energy after a reaction mean?
that products have less free energy than the reactants, and the reaction will go forwards
What is an exergonic reaction?
spontaneous and release energy
What is an endergonic reaction?
requires an input of energy to occur
Which reactions in the body are endergonic?
protein synthesis, nerve impulse conduction, muscle contraction
What are endergonic reactions in the body (protein synthesis, nerve impulse conduction, muscle contraction) driven by?
the energy released by exergonic reactions
What is ATP?
adenosine triphosphate
the common energy currency of cells, unstable and has high stored energy
What happens when cells require energy?
they “spend” ATP
the more active the organism, the greater demand for ATP
What is ATP constantly being generated from?
ADP (adenosine diphosphate) and a molecule of inorganic phosphate
Why is a cell assured of a supply of ATP?
because glucose breakdown during cellular respiration provides the energy for the buildup of ATP in mitochondria
How much free energy of glucose is transformed to ATP?
only 39%, the rest is lost as heat
What are the biological advantages to the use of ATP as an energy carrier in living systems? (4)
- common universal energy currency because it can be used in many different types of reactions
- when ATP is converted to energy, ADP and inorganic phosphate, the amount of energy released is sufficient for a particular biological function, and little energy is wasted
- ATP breakdown can be coupled to endergonic reactions in a way that minimizes energy loss
Describe an endergonic reaction.
creation of ATP from ADP and inorganic phosphate requires input of energy from other sources
ie. cellular respiration
Describe an exergonic reaction.
hydrolysis of ATP releases previously stored energy, allowing the change in free energy to do work and drive other processes
ie. protein synthesis, nerve conduction, muscle contraction
Describe the ATP cycle.
- in cells, ATP carries energy between exergonic reactions and endergonic reactions
- when a phosphate group is removed by hydrolysis, ATP releases the appropriate amount of energy for most metabolic reactions
What is ADP?
more stable than ATP
