Download Chemical Energy

Sylvia S. Mader
Immagini e
concetti
della biologia
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
A5 - Cellular
Activity
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Energy has different forms
Energy is the ability to do work
• Radiant energy
• Chemical energy
• Mechanical energy
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Energy has different forms
Radiant Energy (or solar energy) is the energy coming from
the sun and is associated to electromagnetic waves.
Chemical Energy is the energy contained into organic
molecules in the form of specific chemical bonds.
Mechanical Energy is the energy associated with any type
of motion.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Energy has different forms
Heat is the energy related to the motion of microscopic
systems such as atoms, ions and molecules.
Calorie = the amount of energy needed to increase the temperature of
1 g of water by 1 °C.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Potential energy or kinetic energy?
Potential energy
The energy of a body due to the
position. Is a stored energy.
Kinetic energy
The energy of a body due to its
motion. Is the energy in action.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
The two laws of thermodynamics
Thermodynamics is a branch of sciences concerned with heat
flows and its relations to energy and work.
Principles applied to transformation of energy
are know as “Laws of thermodynamics”.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
The two laws of thermodynamics
I law of Thermodynamics
(or law of conservation of energy)
“Energy can change form within the systems (solar
energy can become chemical energy), but it can be
neither created nor destroyed”.
Solar energy
Chemical energy
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
The two laws of thermodynamics
II law of Thermodynamics
“Energy cannot change from one form to another without
a loss of energy in the form of heat. This heat increases
the entropy (disorder) of the system”.
HEAT
Solar energy
Chemical energy
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
The two laws of thermodynamics
Many important biological reactions involve a
loss of energy as heat.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Energy flow and transformations
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Cellular work is powered by ATP
ATP (Adenosine Triphosphate) is a nucleotide that consists of:
• A double ring of carbon and nitrogen atoms called adenine;
• A small five-carbon carbohydrate called ribose;
• Three phosphate units linked together by covalent bonds.
Adenine
Ribos
e
Phosphate
groups
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Cellular work is powered by ATP
The breaking reaction products (ADP + P) are more stable
than the molecule of ATP.
ATP
Adenosine
Triphosphate
ADP +
P
Adenosine
Diphosphate
Hence, when ATP breaks down to ADP + P,
energy is released.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
ATP cycle
ATP ➞ ADP + P
exergonic reaction
(releases energy)
ADP + P ➞ ATP
endergonic reaction
(requires energy to occur)
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Coupled reactions
Reactions are coupled when the energy required for a
reaction (endergonic) is provided by an exergonic reaction.
ATP hydrolysis is always associated
with endergonic reactions.
Muscular contraction occurs if associated with ATP hydrolysis
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Enzymes are catalysts
Enzymes speed up the reaction by decreasing the
energy of activation (Ea) of a given reaction.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Factors affecting enzymes activity
•Substrate concentration
•Temperature
•pH
•Cofactors as vitamins and coenzymes
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Metabolic pathways and inhibition
Metabolic pathways are
series of chemical reactions
occurring within a cell.
Enzyme inhibition occurs
when a substance binds to an
enzyme and decreases its
activity.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Enzyme inhibition
Noncompetitive inhibition: inhibitor binds to an enzyme
at the allosteric site (a site other than the active site).
Competitive inhibition: an inhibitor and a substrate
compete for the enzyme’s active site.
In the case of some inhibitors such as cyanide, sarin gas or
warfarin (rat poison) enzymatic inhibition can spell death.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Plasma Membrane is dynamic
Proteins are embedded in a phospholipid bi-bilayer in a
“fluid mosaic membrane”.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Membrane Proteins have various
functions
Channel and carrier proteins respectively allow and
assist the passage of molecules through the membrane.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Membrane Proteins have various
functions
Cell recognition proteins help the cell recognize foreign
invaders. Receptor proteins bind specific molecules.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Membrane Proteins have various
functions
Enzymatic proteins carry out metabolic reactions while
junction proteins assist cell-to-cell communications.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Diffusion
Some small molecules or ions such as CO2, O2,
C6H12O6 and H2O, move across the plasma
membrane by diffusion, a passive transport process.
There are two types of diffusion:
Simple diffusion
Facilitated diffusion
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Simple diffusion
Molecules in solution move down a concentration
gradient until they equally distribute.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Facilitate diffusion
Carrier proteins facilitate
diffusion of nonlipid-soluble
substances across the
membrane.
Facilitate diffusion does not require
energy.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Osmosis
Water moves into a region of higher solute concentration, in
order to equalize the solute concentrations on the two sides
of the membrane.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Osmosis
•Cells placed in an isotonic solution
(iso = same) neither gain nor lose water.
•Cells place in a hypotonic solution
(ipo = less) gain water.
•Cells placed in a hypertonic solution
(iper = more) lose water.
Osmosis effects on animal and plant cells
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Active transport
In order to move a substance
against its concentration
gradient the consumption of
energy (ATP) is required.
Carrier proteins involved in
active transport are called
pumps.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Endocytosis
Endocytosis is the process by which cells absorb big
particles by engulfing them.
Most biologically important substances are large molecules
that cannot pass through the plasma membrane.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Exocytosis
Exocytosis is the process by which vesicles transport
substances as digestive enzymes and hormones out of the
cell.
Transport of massive particles (macromolecules) in and out
the cell membrane requires the use of vesicles.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Malfunctions in the membrane
proteins
Malfunctioning plasma membrane
proteins can cause human diseases
such as:
H2O and Cl- are trapped
inside the cell
•Diabetes type 2
•Cystic fibrosis
•Color blindness
malfunctioning FCchannel protein
Accumulation of mucus
in the respiratory tract
Cystic fibrosis is caused by a malfunctioning
gene of the channel protein called FC-protein
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
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