ENERGY Flashcards
-states that the natural tendency of the universe is towards increasing disorder.
-In all energy exchanges and conversions, if
no energy leaves or enters the system
under study, the potential energy of the
final state will always be less than the
potential energy of the initial state.
2nd Law of Thermodynamics
(degree of randomness) naturally tends to
increase and energy naturally converts
to less organized form
total entropy
if potential energy of final state is less
than initial:
releases energy (exergonic)
⚫If potential energy of final state is greater
than initial:
requires energy (endergonic)
measurement of disorder or
randomness of a system
⚫Entropy
- The second law of thermodynamics:
events in the universe tend to proceed
from a state of higher energy to a state
of lower energy. * Such events are called
____________, they can occur
without the input of external
energy
spontaneous
Loss of available energy during a
process is the result of a tendency
for randomness to _________
whenever there is a transfer of
energy.
increase
– total energy
content of the system.
Enthalpy
- A quantitative expression or measure of energy for the
performance of work
Free Energy (Gibbs Free Energy (G))
is the energy available to do work.
Free energy, ΔG,
The first and second laws of thermodynamics can be combined and
expressed mathematically.
* Equation:
ΔH = ΔG + TΔS
Spontaneity depends on both ________(total energy content of system; equivalent to ΔE for our purposes) and ____________.
enthalpy & entropy
- combines enthalpy (H) and entropy (S)
- ultimately decides the spontaneity of
a process
Free energy / Gibbs free energy (G)
Catabolic processes degradative, usually oxidative energy
yielding
(exergonic)
Anabolic processes synthetic, usually reductive energy
utilizing
(endergonic)
break down complex substrates into
simple end products.
* Provide raw materials for the cell.
* Provide chemical energy for the cell.
Catabolic pathways
synthesize complex end products
from simple substrates.
* Require energy.
* Use ATP and NADPH from catabolic pathways.
Anabolic pathways
- biological catalysts ; “agents of life”
Enzymes
Properties of Enzymes
- Specificity
- Catalytic efficiency
- Mostly reversible
Enzyme Compositions
- proteins : amino acids : nucleotides in a gene
Models of Enzyme-Substrate Interaction
- Lock-and-Key Model
- Induced-Fit Model
molecules that prevent enzymes reaching their
maximum turnover numbers
Inhibitors
Environmental Factors Affecting Enzyme Activity
- Temperature
- pH
- Salt concentration
Cells can control the flux of metabolites
through:
- Gene expression
- Compartmentation
- Covalent modification
-Feedback inhibition
regulates enzyme activity through the amount or
concentration of enzymes present in the cell —
determined by relative rates of enzyme synthesis
and degradation
Gene expression
localizes enzymes with different catalytic
properties in the different parts of the cell
* enzymes involved in PS are found in
chloroplast
* hydrolases are found in vacuoles
Compartmentation
regulates enzyme activity through
phosphorylation — phosphorylated form is
active while non-phosphorylated form is inactive
Covalent modification
enzyme activity is regulated by the end products
of the metabolic pathways which inhibit the
enzymes involved in earlier steps
Feedback inhibition
(DNA ® RNA)
Transcription
(RNA ® Protein)
Translation
