Unformatted text preview: Chemical Reactions
one or more substance
Chemical reaction: Process in which _____________________
changed into other substances.
sum total of all the
Metabolism: The ____________________
chemical reactions that
occur within an organism. break down
___________ - metabolic pathways that __________
into smaller units to ____________. Anabolism
- metabolic pathways that ________
from smaller units. These
source of energy
reactions require a ____________________.
reactants and products
Chemical reactions involve both ______________________. 1 A cell’s metabolism involves many intersecting metabolic pathways.
Each pathway begins with a specific reactant molecule which is
then modified in a series of specific enzyme-catalyzed steps to
required product molecule
produce the __________________________.
Enzyme 1 A B
Reaction 1 initial
reactant Enzyme 1 Enzyme 1 C
Reaction 2 thats three reactant to get D D
Reaction 3 final
product 2 Energy
There are two classes of energy:
due to chemical
1) Potential energy – energy that is stored ________________
structure or to location
covalent bonds between C-Hs
in organic molecules store
potential energy. - cellulose in wood or paper for example.
- is chemical potential energy.
on one side of
Concentrating ions or molecules ___________
a cell membrane
also represents stored
potential energy that can be used to do
work in cells.
Fig. 4.12 3 with movement,
2) Kinetic energy - energy associated ___________________
_____________. energy become kinetic
- cell can only do work when _____________________. Energy exists in several different forms:
- heat, chemical, mechanical, electrical, electromagnetic
one of these forms to another
Energy can be converted from _________________________. Sunlight to chemical bond energy, for example. making light energy making light energy By Emmanuelm at English Wikipedia, CC BY 3.0, 4 taking outside energy and they break down that energy turn it to heat energy Fig. 3.2 5 open
Living systems function as _______
systems within the isolated
system of the universe. Fig. 3.11 energy and matter
Open systems bring in ________________
from their surroundings
to maintain their highly organized state heat and waste gases
And they release ______________________
into their environment
increasing the ___________
of their surroundings. island of order
A living organisms is an ____________
in sea of increasing disorder. Energy transfers in living systems are subject to the Laws of
Thermodynamics 6 First law of thermodynamics:
Thermodynamics is the branch of physical science dealing with
relations between heat and other forms of energy and
relationships between all forms of energy.
Energy can be transferred from one type (or form) to another or
but energy can not be created
from one place to another, _________________________________
Means living organisms ______________
the energy they need, so
they must get the energy they need from their surroundings. When a plant converts solar energy into chemical bond energy, the
plant is functioning as an ___________________,
not an energy
7 Second Law of Thermodynamics:
During a transfer (transformation) of energy:
1) there is an increase in the degree of ___________
(entropy) in the univers - entropy(S) is a measure of disorder.
2) there is a decline in ________________
in the universe
useful energy, energy that is actually
- free energy is _________________________________
available to do work
__________________________. One of the characteristics of living organisms is their ability to
their bodies (systems).
a higher degree of order
They can do this by functioning as __________________. 8 They require sources of energy ______________________.
rich in free energy
flow this energy through reactions
Living systems _____________________________
maintaining or increasing order and producing mechanical
work, and: - release, as by-products of metabolism, ______________
heat and small
energy poor molecular like C02
to their environment,
which increases disorder in their surroundings.
As a consequence of growing, organisms cause a _______________
decrease in entropy
in their environment than the __________________
associated with their growth. 9 free energy (AG)
During a chemical reaction, there is a change in ________________. ΔG can be calculated using the formula: ΔG = ΔH - TΔS
H is _________
is the total potential energy or total heat content of
change in the enthalpy
ΔH is the ____________________
of a system over the course of a
reaction. ΔH = H products – H reactants
change in entropy of a system over the course of a reaction
ΔS is the _____________ ΔS = S products – S reactants
T is the temperature in degrees Kelvin.
So, in an _____________
reaction, ΔH increases in value while
^G having a +ve value
ΔS decreases, which will result in ________________________. - because this type of reaction is an endergonic reaction or energy
And, in a _________
reaction, ΔH decreases while ΔS increases
which will result in ΔG having a ______________. - because this type of reaction is an exergonic reaction or energy
reaction. 11 Exergonic Reactions
exergonic ( exothermic) reaction
Energy releasing reactions are _______________________________. negative
Exergonic reactions have a ___________
ΔG because products of the
reaction will have ____________________
than the _________
less free energy
Exergonic reactions are ______________
because they do not require
outside source of energy to take place.
an _____________________ Fig. 3.7
ΔG =-ve value 12 Endergonic Reactions
Endergonic reactions are _____________
reactions and their ΔG
is always a _______________
Positive because the products of the reaction have ____________
the reactants of the reaction.
reactions because they require an outside
source of energy to proceed. Fig. 3.7 ΔG = + ve value 13 ΔG indicates which reactions are exergonic and spontaneous and
which reactions are endergonic and thus requiring an input of
not possible to have a
An implication of the second law is that it is ___________________
complete transfer of free energy
from one molecule to another
during a reaction.
heat which can not be used by living
There is energy released as _____
organisms to do work.
to exergonic reaction or process in cell to get the
Endergonic reactions are coupled
input of energy they require to proceed. Many endergonic reactions in cells are coupled to the conversion
ATP to ADP
the latter reaction being an exergonic reaction.
14 hexokinase 1. Glucose + phosphate + energy Glucose-phosphate + H2O
ΔG = ____ 2. ATP ADP + Pi + energy 7.3 kcal/mole
ΔG = ____ Pi transferred
to gluoce 4
ΔG = ____
ATP is adenosine triphosphate bond to get enegry out
Pi bond ADP is adenosine diphosphate
Pi is an inorganic phosphate molecule.
decrease in entropy
Note that there is a ________________
in reaction 1.
Fig. 3.14 15 ~ Example illustrates:
1) Enzyme hexokinase) _____________
two reactions. - thermodynamically favorable reaction is used to
- drive the thermodynamically ________________. 2) Whenever energy is transformed, there is always an increase
in entropy (decrease in free energy) as energy is __________
_______________________. 16 resynthesized
ATP used to drive endergonic processes must be ________________.
Resynthesis of ATP from ADP is a _______________________. endergonic reaction
It is also an ____________________
so it has to be coupled to an
exergonic reaction. ADP + Pi +energy The ATP/ADP Cycle
Energy from one of the ____________
_____ in respiration or in photosynthesis heat like a
vaucum Fig. 3.16
17 75g of ATP
There is roughly __________________
in the average human.
A reasonably active person turns over about __________
ATP per day, so a typical ATP molecule is broken down and
each day. In rapidly metabolizing tissues the lifetime of each ATP molecule
A FEW seconds
is only ____________________
. 18 Enzymes
Reactions proceed _____________
physiological temperatures. energy barriers prevent reactions from
At these temperatures, _____________
proceeding at a reasonable rate. Energy required to overcome this energy barrier is called
activation energy )Ea)
__________________. Fig. 3.17 19 Activation energy makes critical bond(s) in the reactants
Enough molecules must gain enough Ea to occupy a ___________
where critical bonds are unstable and ______________.
can be broken
state Reaction rates can be sped up by the application of high heat or
pressure, but these options kill living organisms.
Living organisms, instead, speed up reaction rates using globular
proteins called ___________________.
enzymes as catalysts
speed up the rate of reaction
Catalysts are chemical agents that _______________________
but are, themselves, not modified during the reaction. 20 Fig. 3.19
substrates Don’t need a lot of enzyme to speed up a reaction because enzymes
can be repeatedly reused
- reaction rate sped up without need for an increase of heat.
not change the ^G
Note the enzyme does _____________________for
a reaction. Reactants in enzyme catalyzed reactions are called ____________.
21 lowering the required Ea
Enzymes speed up reactions by ________________________. very little energy needed substrates 22 substrance(s)
Each enzyme has a particular location into which the __________
can fit, called the active site
- it is the site of _______________.
catalysis The active site for each enzyme has a __________________
unique 3-D shape
______________________. β-galactosidase specific as to which subtrate(S)
Thus, each enzyme is ______________________________
- enzymes _______________________. 23 The substrate(s) enters the active site and ___________
for a brief period of time, to form an ____________________.
enzyme- substrate complex
An enzyme-substrate complex is a temporary molecule formed
when an enzyme comes into ______________
with its substrate.
Just before the substrate(s) binds to the enzyme, the enzyme _______
such that it will more precisely binds to the substrate induced fit
- called ________________. 24 Induced Fit: Example - Enzyme Hexokinase
glucose ATP enzyme’s shape
modified during the interaction
between the enzyme and its substrate. induced fit
occurring A change in shape of the enzyme
occurs called _______________.
Only the proper substrate is capable
proper alignment of
of inducing the _______________
the active site. pull them
together in the
after induced fit Hexokinase has a large induced fit motion that closes over
adenosine triphosphate and the substrate glucose. 25 broke apart and water is brought in Fig. 3.21 Binding of the substrate to the enzyme causes changes in the
distribution of electrons
in the chemical bonds of the substrate(s),
ultimately causing reactions to take place that lead to the
formation of the products.
26 factors that lower Ea and thus, speed up of the reaction rate
Enzymes bring substrate molecules ________
and in an orientation that
facilitates the reaction. Fig. 4.23
Enzyme has a unique _____________________
in the active site which promotes catalysis. The enzyme may also stretch a critical bond
on the substrate(s) causing it to reach a
which makes the bond
easier _to break
_ speed up
It’s these factors that ____________
and, thus, ___________
reaction rate. 27 The reaction proceeds and the substrate(s) are converted to
The product(s) are _____________
and the enzyme returns to its
shape opening up the active site so that it is ready to
catalyze another reaction
________________________. 25 Catalytic Cycle of an Enzyme
substrate enzyme-substrate complex
products released Fig. 3.21 hydrolysis
This is a _________
reaction 29 Some enzymes require that a non-protein functional group or
molecule called a _________
to associate with the enzyme for the
enzyme to function. Cofactor Types
that bind to a specific location in the enzyme, usually
within the active site.
- include ions of iron, copper, zinc or manganese Metals are known to be involved in over 40% of enzymatic
metallome the life-supporting metals
These metals are part of the ________,
that have biological functions. 30 coenzymes are organic cofactors which
carriers that transfer functional groups or electrons from
one organic molecule to another. They are required by certain enzymes to carry out their catalysis.
They bind into the active site of the enzyme, participating
considered to be substrates
in catalysis, but they are _______________________________
of the reaction.
that as ADP, picks up a ______________
reaction, becoming ATP, and then delivering the
phosphate group to another protein involved in a different
reaction. 31 Conditions Affecting Enzyme Activity
I. Effects of Temperature and pH on Enzyme Activity
Enzymes reach their ________________
pH and temperature. Activity of enzymes subjected to pH or temperature on either side
of their optimum can __________
because the chemical structure
of the enzyme is altered.
Activity of an enzyme can drop dramatically when environmental
conditions are ____________
for the enzyme. 32 I. A. pH
Most cytosolic enzymes have a pH optima close to
the pH found within the _________________.
However, hydrolytic enzymes in ____________
have their highest
activity in _________________. Fig. 4.28 human stomach is most active at
Pepsin secreted into the _______________________________
(acidic) pHs, whereas trypsin secreted into the ______________
moderate basic pHs
most at _______________________.
33 I. B. Temperature
As temperatures rise, chemical reactions proceed _____________.
Because the _________________
of molecules increases at higher
of collisions and strength of collisions increase between
enzymes and their substrates at higher temperatures. At cooler than optimum temperatures, the substrate molecules
enough kinetic energy
do not have ____________________
to interact with the enzyme
and enzyme activity drops off dramatically. 34 Peak activity for most enzymes, is between 40-50oC.
of structure and
Fig. 4.29 still with slight
u need to boil food to kill the enzyme but if temperature get to high, the protein begins to unfold losing its 3-D globular structure,
resulting in significant reduction in function and finally complete loss of function at very high
we say enzyme has become denature.
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