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FAQ’S
1.
What do you mean by respiration?
Ans: In physiology, respiration (often confused with breathing) is defined as the transport of oxygen from the outside air
to the cells within tissues, and the transport of carbon dioxide
in the opposite direction. This is in contrast to the biochemical definition of respiration which refers to cellular respiration: Cellular respiration is the set of the metabolic reactions and processes that take place in the cells of organisms
to convert biochemical energy from nutrients into adenosine
triphosphate (ATP), and then release waste products. The reactions involved in respiration are catabolic reactions, which
break large molecules into smaller ones, releasing energy in
the process as they break high-energy bonds. Respiration is
one of the key ways a cell gains useful energy to fuel cellular activity. Chemically, cellular respiration is considered an
exothermic redox reaction. The overall reaction is broken into
many smaller ones when it occurs in the body, most of which
are redox reactions themselves.
2.
What are the basic types of respiration?
Ans: Cellular respiration may be divided into two categories
depending on the availability of oxygen.
aerobic respiration: Aerobic respiration requires oxygen in
order to generate energy (ATP). Although carbohydrates, fats,
and proteins can all be processed and consumed as reactant, it
is the preferred method of pyruvate breakdown in glycolysis and
requires that pyruvate enter the mitochondrion in order to be fully
oxidized by the Krebs cycle. The product of this process is energy
in the form of ATP (adenosine triphosphate), by substrate-level
phosphorylation, NADH and FADH2.
b) Anaerobic respiration is used by some microorganisms
in which neither oxygen (aerobic respiration) nor pyruvate or a
pyruvate derivative (fermentation) is the final electron acceptor.
Rather, an inorganic acceptor such as sulfur is used. Yeast and
muscle cells are examples which they can respire anaerobically for
a short time. This is also called as oxygen debt.
3.
What are respiratory substrates? Name the most
common
respiratory substrate.
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Ans: Like animals, the plants also require energy for growth
and development, metabolism, and other life activities. This energy
mainly comes from respiratory breakdown of various substrates.
These substrates are called organic nutrients and synthesized
inside the plants by anabolic processes (viz., photosynthesis, fat
synthesis, protein synthesis, etc.) these organic substances, which
are present in large amounts in plant cells and respired completely
to CO2 and H2O, are called respiratory substrates. The most
commonly used respiratory substrates are carbohydrates.
Differentiate between Respiration and Combustion.
4.
Ans:
Respiration
It
takes
place
in
air
oxygen.
It is a single-step process
or
Enzymes are not involved
Energy release is vigorous and
not under control
energy is released in form of heat
and light (a flame can result)
Combustion
Takes place in cells.
While a series of chemical
reactions.
It is controlled by enzymes.
Energy release is slower and
under control
energy is released in form of heat
and an energy-rich compound
Differentiate between Glycolysis and Krebs cycle.
Ans: Glycolysis is a series of reactions carried out by a group
of soluble enzymes located in the cytosol. Chemically, glucose
is partly oxidized to produce two molecules of pyruvate (a three
carbon compound), a little ATP, and stored reducing power in the
form of a reduced pyridine nucleotide, NADH. Both glycolysis and
TCA cycle takes place in the inner membrane of mitochondrion.
Tricarboxylic acid cycle: When oxygen is present, acetyl-CoA
is produced from the pyruvate molecules created from glycolysis.
Once acetyl-CoA is formed, two processes can occur, aerobic or
anaerobic respiration. When oxygen is present, the mitochondria
will undergo aerobic respiration which leads to the Krebs cycle.
However, if oxygen is not present, fermentation of the pyruvate
molecule will occur.
5.
Differentiate between Aerobic respiration and Fermentation
Ans: If we compare both anaerobic respiration and anaerobic
fermentation, we can say that both of them are completely
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separate from each other as both follow different pathways.
In anaerobic respiration, the process involves the transfer of
electrons through a system of chain system in the membrane
of the cell.
Fermentation takes place when a co-enzyme, NADH reduces
the pyruvate to form the organic compound. It is the process
of getting energy by the oxidation of some compounds like
carbohydrates, and by using an endogenous electron-acceptor that is usually an organic compound. The common products of fermentation are lactic acid, ethanol and hydrogen etc.
But respiration is the process where electrons are given to an
exogenous electron-acceptor, such as oxygen, through the
electron transport chain. Another difference between fermentation and respiration is that it is not necessary for fermentation to occur in environments suitable for anaerobic respiration. A good example of this is yeast, which ferments even if
oxygen is present, or if sugar is present. Thus, we can easily
say that fermentation can occur when the electrons that are
present in the coenzymes (NADH derived after glycolysis) are
turned back partly to pyruvate. It should also be noted that
the electrons are donated to things that have come from the
pyruvate cells.
There is yet another difference between anaerobic respiration
and anaerobic fermentation is the electron acceptor, which is
also known as the final electron acceptor. For fermentation,
pyruvate is the final electron acceptor. This can be seen in
yeast fermentation, which gives alcohol as the final acceptor
and does not break further for releasing energy. However,
the main purpose of anaerobic respiration is to produce ATP
(Adenosine Triphosphate), which is used by a cell for energy
purposes.
6. What
are the main steps in aerobic respiration? Where
does it take place?
Ans: The main steos of aerobic respiration are:
a) Glycolytic breakdown of glucose to pyruvic acid
b) Oxidative decarboxylation of pyruvic acid to acety coA
c) Krebs cycle and
d) Terminal oxidation and phosphorylation in respiratory
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chain.
8.
Explain the role of ETS.
Ans: The electron transport chain consists of a collection
of electron transport proteins bound to the inner of the two
mitochondrial membranes. This system transfers electrons from
NADH, produced during glycolysis and the TCA cycle, to oxygen.
This electron transfer releases a large amount of free energy in
the form of ATP.
9. Distinguish between Glycolysis and Fermentation.
Ans: Glycolysis is a series of reactions carried out by a group
of soluble enzymes located in the cytosol. Chemically, glucose
is partly oxidized to produce two molecules of pyruvate (a three
carbon compound), a little ATP, and stored reducing power in the
form of a reduced pyridine nucleotide, NADH. Both glycolysis and
TCA cycle takes place in the inner membrane of mitochondrion.
Without oxygen, pyruvate (pyruvic acid) is not metabolized by
cellular respiration but undergoes a process of fermentation. The
pyruvate is not transported into the mitochondrion, but remains in
the cytoplasm, where it is converted to waste products that may
be removed from the cell. This serves the purpose of oxidizing the
electron carriers so that they can perform glycolysis again and
removing the excess pyruvate. Fermentation oxidizes NADH to
NAD+ so it can be re-used in glycolysis.
10. Distinguish between Aerobic respiration and Anaerobic
respiration.
Ans:
oxygen requirement
oxidation of sugar
energy released
end products
Occurrence
aerobic respiration
anaerobic respiration
Essential
complete oxidation
large amount
inorganic: CO2 and H2O
Nill
incomplete oxidation
Small amount
organic:ethanol
or
lactic acid
in lower organisms
(e.g.
bacteria
and
yeast) and vertebrate
muscles.
in most living
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Distinguish between Glycolysis and Citric acid Cycle.
Ans: Glycolysis is a series of reactions carried out by a group
of soluble enzymes located in the cytosol. Chemically, glucose
is partly oxidized to produce two molecules of pyruvate (a three
carbon compound), a little ATP, and stored reducing power in the
form of a reduced pyridine nucleotide, NADH. Both glycolysis and
TCA cycle takes place in the inner membrane of mitochondrion.
Tricarboxylic acid cycle: When oxygen is present, acetyl-CoA
is produced from the pyruvate molecules created from glycolysis.
Once acetyl-CoA is formed, two processes can occur, aerobic or
anaerobic respiration. When oxygen is present, the mitochondria
will undergo aerobic respiration which leads to the Krebs cycle.
However, if oxygen is not present, fermentation of the pyruvate
molecule will occur. In the presence of oxygen, when acetyl-CoA
is produced, the molecule then enters the citric acid cycle (Krebs
cycle) inside the mitochondrial matrix, and gets oxidized to CO2
while at the same time reducing NAD to NADH. NADH can be used
by the electron transport chain to create further ATP as part of
oxidative phosphorylation. To fully oxidize the equivalent of one
glucose molecule, two acetyl-CoA must be metabolized by the
Krebs cycle. Two waste products, H2O and CO2, are created during
this cycle.
1. Define RQ. What is its value for fats?
Ans: Respiratory quotient (R.Q) id the ratio of the volume of carbon
dioxide released to the volume of oxygen taken in respiration in
the given period of time at standard temperature and pressure.
R. Q. = Volume of CO2 evolved
Volume of O2 absorbed
Its value for fats is less than unity
2. Give briefly the structure of ATP?
ATP contains the purine base adenine and the sugar ribose which
together form the nucleoside adenosine. The basic building blocks
used to construct ATP are carbon, hydrogen, nitrogen, oxygen,
and phosphorus which are assembled in a complex that contains
the number of subatomic parts equivalent to over 500 hydrogen
atoms. One phosphate ester bond and two phosphate anhydride
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bonds hold the three phosphates (PO4) and the ribose together.
The construction also contains a b-N glycoside bond holding the
ribose and the adenine together.
14. What are the main constituents of ATP?
Ans: ATP consists of the purine base adenine and the sugar
ribose which together form the nucleoside adenosine and three
phosphates.
15. What do you mean by compensation point?
The compensation point is the amount of light intensity on the
light curve where the rate of photosynthesis exactly matches
the rate of respiration. At this point, the uptake of CO2 through
photosynthetic pathways is exactly matched to the respiratory
release of carbon dioxide, and the uptake of O2 by respiration is
exactly matched to the photosynthetic release of oxygen.
16. What are redox reaction?
Any oxidation-reduction (redox) reaction can be divided into
two half reactions: one in which a chemical species undergoes
oxidation and one in which another chemical species undergoes
reduction. Although oxidation and reduction must occur together,
it is convenient when describing electron transfers to consider the
two halves of an oxidation-reduction reaction separately.
17. Define redox potential?
Reduction potential (also known as redox potential, oxidation
/ reduction potential, ORP or ) is a measure of the tendency
of a chemical species to acquire electrons and thereby be reduced.
Reduction potential is measured in volts (V), or millivolts (mV).
Each species has its own intrinsic reduction potential; the more
positive the potential, the greater the species’ affinity for electrons
and tendency to be reduced.