Respiration in Plants 1 Flashcards
define respiration
Mechanism of breakdown of food materials within the call to release energy
and trapping of this energy for synthesis of ATP is called Cellular Respiration.
The breaking of the C-C bonds of complex compounds
through oxidation within the cells, leading to release of considerable
amount of energy is called respiration.
what are respiratory substates
the compounds that are oxidised in the process of respiration is called as respiratory substrates. They are the molecules which participate in metabolic pathways.
Usually
carbohydrates are oxidised to release energy, but proteins, fats and even
organic acids can be used as respiratory substances in some plants, under
certain conditions
how is energy used in the body
it is important to understand that the energy released by oxidation in
respiration is not (or rather cannot be) used directly but is used to
synthesise ATP, which is broken down whenever (and wherever) energy
needs to be utilised. Hence, ATP acts as the energy currency of the cell.
This energy trapped in ATP is utilised in various energy-requiring
processes of the organisms, and the carbon skeleton produced during
respiration is used as precursors for biosynthesis of other molecules in
the cell.
why is respiration a multistep reaction and not a single large oxidation?
The respiratory pathways is sequenced in the form of multistep reactions so as to reduce the loss of energy in the form of heat.
do plants breathe
es, plants require
O2
for respiration to occur and they also give out CO2
. Hence, plants have
systems in place that ensure the availability of O2
. Plants, unlike animals,
have no specialised organs for gaseous exchange but they have stomata(leaves, herbaceaous stem)
and lenticels(woody stem, fruit) for this purpose
i) root- has air spaces within parenchyma tissue/ permeable to air present in air spaces in the soil/ diffusion of air from soil to cells
ii) stem- herbaceous- stomata/ woody- lenticels( ruptured epidermis with loosely arranged prenchyma cells )
why do plants not necessarily have respiratory organs
First, each plant part takes care of its own gas-exchange needs. There is very little transport of gases from one plant part to another.
Second, plants do not present great demands
for gas exchange. Roots, stems and leaves respire at rates far lower than
animals do. Only during photosynthesis are large volumes of gases
exchanged and, each leaf is well adapted to take care of its own needs
during these periods. When cells photosynthesise, availability of O2
is not
a problem in these cells since O2
is released within the cell.
Third, the distance that gases must diffuse even in large, bulky plants is not great.
Each living cell in a plant is located quite close to the surface of the plant.In stems, the ‘living’ cells are organised in thin layers inside
and beneath the bark. They also have openings called lenticels. The cells
in the interior are dead and provide only mechanical support. Thus, most
cells of a plant have at least a part of their surface in contact with air. This
is also facilitated by the loose packing of parenchyma cells in leaves, stems
and roots, which provide an interconnected network of air spaces.
what is respiratory quotient
The ratio of the
volume of CO2
evolved to the volume of O2
consumed in respiration is
called the respiratory quotient (RQ) or respiratory ratio.
The respiratory quotient depends upon the type of respiratory
substrate used during respiration
what is respiratory quoetient for:
(I) glucose
(ii) fats
(ii) proteins
() 1
(ii) tripalmitin- 0.7
(iii) 0.9
What is important to recognise is that in living organisms respiratory
substrates are often more than one; pure proteins or fats are never used
as respiratory substrates.
intro to glycolysis
The term glycolysis has originated from the Greek words, glycos for sugar,
and lysis for splitting. The scheme of glycolysis was given by Gustav
Embden, Otto Meyerhof, and J. Parnas, and is often referred to as the
EMP pathway.
describe glycolysis
In anaerobic organisms, it is the only process in respiration.
Glycolysis occurs in the cytoplasm of the cell and is present in all living
organisms. In this process, glucose undergoes partial oxidation to form
two molecules of pyruvic acid.
from where do plants get their food
In plants, this glucose is derived from
sucrose, which is the end product of photosynthesis, or from storage.carbohydrates. Sucrose is converted into glucose
and fructose by the enzyme, invertase, and these
two monosaccharides readily enter the glycolytic
pathway.
what are the steps of glycolytic pathway
-Glucose and fructose are
phosphorylated to give rise to glucose-6-
phosphate by the activity of the enzyme
hexokinase. This phosphorylated form of
glucose then isomerises to produce fructose-6-
phosphate.
The fructose 1, 6-bisphosphate is split
into dihydroxyacetone phosphate and
3-phosphoglyceraldehyde (PGAL). We find
that there is one step where NADH + H+ is
formed from NAD+
; this is when
3-phosphoglyceraldehyde (PGAL) is converted
to 1, 3-bisphosphoglycerate (BPGA). Two
redox-equivalents are removed (in the form of
two hydrogen atoms) from PGAL and transferred
to a molecule of NAD+
. PGAL is oxidised and
with inorganic phosphate to get converted into
BPGA. The conversion of BPGA to
3-phosphoglyceric acid (PGA), is also an energy
yielding process; this energy is trapped by the
formation of ATP. Another ATP is synthesised
during the conversion of PEP to pyruvic acid.
what is the fate of pyruvic acid
Pyruvic acid is then the key product of
glycolysis.
There are three major ways in which different cells handle pyruvic acid
produced by glycolysis. These are lactic acid fermentation, alcoholic
fermentation and aerobic respiration. Fermentation takes place under
anaerobic conditions in many prokaryotes and unicellular eukaryotes.
For the complete oxidation of glucose to CO2
and H2O, however, organisms
adopt Krebs’ cycle which is also called as aerobic respiration. This requires
O2
supply.
what is produced by fermentation (alcoholic)
In fermentation, say by yeast, the incomplete oxidation of glucose is
achieved under anaerobic conditions by sets of reactions where pyruvic
acid is converted to CO2
and ethanol. The enzymes, pyruvic acid
decarboxylase and alcohol dehydrogenase catalyse these reactions.
pyruvate —–pyruvate decarboxylase–> acetaldehyde + co2
acetaldehyde—-alcohol dehdryogenase–> ehtanol( w/ nadh2–>nad+)
what is produced by fermentation ( lactic acid)
Other
organisms like some bacteria produce lactic acid from pyruvic acid.In animal cells also, like muscles
during exercise, when oxygen is inadequate for cellular respiration pyruvic
acid is reduced to lactic acid by lactate dehydrogenase. The reducing
agent is NADH+H+ which is reoxidised to NAD+
in both the processes.
