Lecture 14 Flashcards
Uses of energy in living things
- movement
- metabolism
- response to stimuli
Energy undergoes transitions in forms
- potential energy
- kinetic energy
- mechanical, chemical, electrical
Properties of energy
- first law of thermodynamics
2. second law of thermodynamics
first law of thermodynamics
- total energy remains constant in a closed system
2. energy cannot be created or destroyed
second law of thermodynamics
- in an isolated system, any change causes the quantity of concentrated, useful energy to decrease
- energy is converted from more useful to less useful forms
- organization of matter and energy
organization of matter and energy
- concentrated energy is more ordered (complex) chemically
2. entropy
Entropy
all processes in an isolated system result in an increase in randomness
Free energy
the portions of a system’s energy that is able to perform work when temperature is uniform throughout the system
what does free energy provide
a criterion for measuring spontaneity of a system
Where is energy stored in
the chemical bonds of biological molecules
dehydration synthesis
How is this stored energy released so work can be accomplished
hydrolysis reaction
What are energy releasing chemical reactions
exergonic
exergonic chemical reactions
- high energy reactants -> low energy products
Endergonic reactions
low energy reactants -> high energy products
A cell does three main kinds of work
- mechanical
- transport
- chemical
mechanical work
- beating of cilia
- contraction of muscle cells
- movement of chromosomes
transport work
pumping substances across membranes against the direction of spontaneous movement
chemical work
driving endergonic reactions such as the synthesis of polymers from monomers
In most cases, what is the immediate source of energy that powers cellular work
ATP
ATP
a type of nucleotide consisting of the nitrogenous base adenine, the sugar ribose, and a chain of three phosphate groups
How can the bonds between phosephate groups be broken
by hydrolysis
What does the hydrolysis of the end phosphate group form
adenosine diphosphate
what does the hydrolysis of the end phosphate group release
7.3 kcal of energy per mole of ATP under stnadard conditions
ATP ->
ADP + Pi
ATP is a renewable resource
adding a PO4- group to ADP
ATP adding a PO4- group to ADP
catabolic reactions in the cell provide energy for addition
In a working muscle cell the entire pool of ATP is recycled once each minute
over 10 million ATP consumed and regenerated per second per cell
Whad does regeneratio, an endergonic process, require
an investment of energy: delta G = 7.3 kcal/mol
What do chemical reactions in living organisms need to be
catalyzed
catalyst
a chemical agent that changes the rate of a reaction without being consumed by the reaction
enzyme
a catalytic protein
What do enzymes regulate
the movement of molecules through metabolic pathways
Activation energy
the amount of energy necessary to push the reactants over an energy barrier
at the summit of activation energy
the molecules are at an unstable point, a transition state
The difference between free energy of the products and the free energy of the reactants
delta G
Enxyme speed reactions by lowering EA
the transition state can then be reached even at moderate temperatures
Enzymes do not grange delta G
- it hastens reactions that would occur eventually
2. enzyme selectivity etermines which chemical processes occurs
Enzyme regulation
- synthesis
- active/inactive forms
- feedback inhibition
- allosteric regulation
- competitive inhibition
- non-competitive inhibitors
- cofactors
- cooperativity
feedback inhibition
metabolic pathway is turned off by its end product
the end product of feedback inhibition
acts as an inhibitor of an enzyme in the pathway
if the product of feedback inhibition is abundant
the pathway is turned off
if the product of feedback inhibition is rare
the pathway is active
what has a major impact on reaction rate
temperature
as temperature increases…
collisions between substrates and active sites occur more frequently as molecules move faster
each enzyme has an…
optimal temperature
what also influences shape and therefor reaction rate
pH
optimal pH for most enzymes
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