Chapter 8 Flashcards
Living cell is a …
miniature factory where thousands of reactions occur that convert energy into work
Energy
the capacity to do work
Some organisms can convert ___ to light
energy to light
i.e. bioluminescent of jellyfish
Some organisms can convert light into___
chemical energy
i.e. in plants
Organism’s metabolism
transforms matter and energy, subject to the laws of thermo, into the ability to perform work
Metabolism
the totality of an organism’s chemical reactions that arises from interactions between molecules
Metabolic Pathway
has multiple steps that begin with a specific molecule and end with a product that is catalyzed by specific enzymes (highly specific)
Catabolic Pathways
break down complex molecules into simpler compounds during a process that release energy
i.e. during cellular respiration, glucose i broken down into CO2 and H2O in the presence of O2
Anabolic Pathways
build complicated molecules from simpler ones during a process that consumes energy
Energy
- the capacity to cause change and exists in various forms some of which can perform work
- can be converted from one form to another
Kinetic Energy
the energy associated with motion
Potential Energy
stored in the location of matter and includes chemical energy stored in molecular structures, such as glucose
Thermodynamics
The study of energy transformations and life is subject to the laws of thermodynamics
1st Law of Thermodynamics
states that energy can be transferred and transformed, but energy cannot be created or destroyed
(Conservation of energy)
Entropy
- the quantity of disorder or randomness
- the more random a collection of matter, the greater the entropy
2nd Law of Thermodynamics
states that every energy transfer or transformation increases the entropy of the universe
Order may increase locally; however,
the universe tends towards randomness
in other words, spontaneous changes do not require outside energy to increase the entropy, or the amount of disorder
Living systems create ordered structures from…
less ordered starting materials and decrease the entropy of the universe and
use energy to maintain order
i.e. aa are ordered into polypeptide chains which are ordered into proteins which are ordered into organelles, etc.
Free energy
the energy that can do work under cellular conditions (constant temp and pressure)
Free-Energy Change (∆G)
of a reaction tells us whether the reaction is spontaneous or not
Spontaneous Reaction
Spontaneous changes do not require energy which is preferred for cellular reactions
(create energy)
∆G equation
∆G = ∆H - T∆S
where H = enthalpy
S = entropy
Organisms live at the expense of free energy during a spontaneous change,
free energy decreases and the stability (order) of a system increases
i.e. - ∆G becomes a negative #
A system at equilibrium is…
at maximum stability
2 classifications of chemical reactions
1) exergonic
2) endergonic
based on their free energy (∆G) state
Exergonic reaction
proceeds with a net release of free energy and is a spontaneous reaction (- ∆G)
Endergonic reaction
one that absorbs free energy from its surroundings and is non spontaneous
(+ ∆G)
Reactions in a closed system
- eventually reach equilibrium
- can perform no work
- is a dead cell
Reactions in an open system
Cells tend to maintain a state of disequilibrium, which are capable of constantly exchanging matter with their surroundings
Coupling Reactions
ATP powers the coupling of exergonic and endergonic reaction as a way to manage their energy resources to do work
3 kinds of work a cell does
1) Mechanical
2) Transport
3) Chemical
1) Mechanical
the beating of cilia or contraction of muscles
2) Transport
the pumping of substances across membranes
3) Chemical
driving endergonic reactions such as the synthesis of polymers from monomers
ATP (adenosine triphosphate)
the cell’s energy shuttle and provides energy for cellular functions
Energy released from ATP
when the terminal phosphate bond is broken by hydrolysis and favorable products are produced
releases 7.3kcal of energy/mole of ATP with a (- ∆G)
ATP hydrolysis can be
coupled to other reactions to make the overall runs favorable of the cell
i.e. glutamic acid + ammonia => glutamine (G: +3.4kcal/mol) with
ATP + H2O => ADP + P ( G: -7.3kcal/mol)
= total G -3.9kcal/mol
ATP drives endergonic reactions by
phosphorylation: transferring a phosphate to other molecules creating a more reactive (less stable) than the original unphosphorylated molecule
The hydrolysis of ATP powers three types of
cellular work
1) Mechanical: place P on protein=> activate (i.e. myosin); ATP phosphorylates motor proteins
2) Transport: active transport; ATP phosphorylates transport proteins
3) Chemical: coupling or adding P on substrates; ATP phosphorylates key reactants
ATP is a renewable resource that
can be regenerated by the addition of a phosphate group to ADP
- the energy to phosphorylate ADP comes from various catabolic pathways that drive the regeneration of ATP from ADP and phosphate
Enzymes
- speed up metabolic reactions to make them biologically relevant by lowering energy barriers
- a catalytic protein capable of speeding up reaction rates by lowering energy barriers (make reactions go faster)
Catalyst
a chemical agent that speeds up a reaction without being consumed by the reaction
Enzymes regulate
reactions in metabolic pathways by bond breaking and forming
“reorganization”
Enzymes within a cell may be groups into
complexes, incorporated into membranes, or contained inside organelles (i.e. the mitochondria)
Ribosome
is an enzyme made up of protein and RNA
Every chemical reaction between molecules involves both
bond breaking and bond forming and enzymes help break and reform chemical bonds
Sucrase
an enzyme that catalyzes the hydrolysis of sucrose is a chemical reaction involving the breaking of the bond between glucose and fructose and the formation of new bonds with hydrogen and hydroxyl ions with water
Activation Energy (Ea)
the initial amount of energy needed to start a chemical reaction
- the energy to push the reactants over the energy barrier
At the summit of the reaction, the molecules are in an unstable condition known as
transition state
Enzyme and activation energy
an enzyme will catalyze/speed up reactions by lowering Ea barrier but not the ∆G
Energy profile or “reaction coordinate” for an exergonic reaction
releases energy into its surrounding
Enzymes accelerate
reactions and lower their Ea by providing an environment for the chemical reaction to proceed
Substrate
the reactant or molecule an enzyme acts on
Enzyme binds to substrate
forming an enzyme-substrate complex during which the catalytic action of the enzyme converts the substrate to the product or products
- binds at the active site which is a specific region on the enzyme where the substate binds
Induced fit of a substrate
brings chemical groups of the active site into positions that enhance or tighten their ability to catalyze the chemical reaction wth their substrates
Active Site can lower Ea barrier by
1) orienting substrates correctly,
2) straining substrate bonds,
3) providing a favorable microenvironment
4) covalently bonding to the substrate
the activity of an enzyme is affected by general environment factors
temperature and pH
Each enzyme has an optimal temperature and pH in which it can function
i.e. Taq (temperature)
Trypsin (pH 8 , intestinal pH)
Cofactors
nonprotein enzyme helpers (inorganic)
Coenzymes
organic cofactors for enzymes
Competitive inhibitors
bind tot eh active site of an enzyme competing with the substrate
Noncompetitive inhibitor
bind to another part of an enzyme, changing the function
Metabolic pathways
must be tightly regulated and enzyme activity is essential to control cellular metabolism
Allosteric regulation
a protein’s function at one site is affected by binding of a regulatory molecule at another site
Many enzymes are allosterically regulated
to become more stable (active) or inhibited (stop/block) depending on the needs of the cell
Allosteric enzymes
change shape when regulatory molecules bind to specific sites, affecting function
Cooperativity
a form of allosteric regulation that can amplify enzyme activity
- enzymes with multiple cattail units can become stabilized upon substrate binding which factors additional substrate binding and activity
i.e. oxygen binding and transport protein hemoglobin
Feedback inhibition
- the end product of metabolic pathway feeds bask upon itself and shuts down the pathway
- prevents a cell from wasting chemical energy
i.e. Isoleucine will feedback and inhibit threonine deaminase
