Download RESPIRATION

RESPIRATION
What is
respiration..?
The phenomenon of liberation of
energy from organic substances
in a multistep enzyme mediated
catabolic process is described as
respiration.
TWO DEFINITIONS OF RESPIRATION
BIOCHEMICAL RESPIRATON PHYSIOLOGICAL RESPIRATION
• The metabolic process
by which an organism
obtain energy by
reacting oxygen with
glucose to give water
,carbon dioxide & ATP.
• It refers to cellular
respiration which takes
place in individual cell.
• It concern with the bulk
flow and transfer of
metabolites between
the organism and
external environment.
• Breathing is a part of
physiological respiration
which include exchange
of gases.
RESPIRATORY QUOTIENT(RQ)
Ratio of volume of CO2 release to the volume of
O2 taken in respiration in the given period of
time at standard temp. and pressure.
R.Q.= Volume of CO2 evolved
Volume of O2 absorbed
R.Q OF CARBOHYDRATES
• The volume of CO2 evolved during the process
is equal to the volume of O2 absorbed.
• Thus the R.Q. is equal to unity.
• R.Q. = vol.of CO2
vol.of O2
R.Q OF FATS
• Fats are hydrolysed to fatty acids and glycerol.
• Complete oxidation of glycerol results R.Q. of
0.86.
• The fatty acids, being poorer in oxygen,
require more oxygen for complete oxidation
as compared to CO2.
• R.Q. become less than unity.
R.Q FOR PROTEINS
• Proteins are hydrolysed into amino acids.
• They require more oxygen and evolve less
carbon dioxide during their complete
oxidation.
• R.Q. become less than unity.
R.Q FOR ORGANIC ACIDS
Acids are rich in oxygen.
Evolve more CO2 & R.Q. become more.
R.Q. of oxalic acid is 4 as shown in the following
reaction .
2(COOH)2 + O2
4CO2 + 2H2O+60.2 K cal
R.Q. = vol. of CO2 = 4 = 4
vol. of O2
1
RESPIRATORY SUBSTRATES
• Organic nutrients which are synthesized inside
the plant by anabolic processes
(photosynthesis,fat synthesis and protein
synthesis).
• Respired completely to CO2 and H2O.
• Under natural conditions only carbohydrates are
oxidized(floating respiration).
• If carbohydrates are used up & shortage become
acute then other protoplasmic structures may be
catabolized (protoplasmic respiration).
TYPES OF SUBSTRATES
• 1. CARBOHYDRATES:- major respiratory
substrates in plants. glucose, fructose,
sucrose, starch.
• R.Q. for carbohydrates-1
• (a) Starch :- a polysaccharide which is broken
down into glucose-1 phosphate units by the
action of enzyme starch phosphorylase.
• Glucose-1 phosphate is further converted into
glucose-6 phosphate by enzyme phosphoglucomutase.
• Glucose-6 is an intermediate of glycolysis &
oxidized completely to CO2 & H2O.
• (b) Sucrose:- It is the principal soluble
disaccharide which is converted into the
glucose and fructose by the action of enzyme
invertase.
• (C) Glucose:- A monosaccharide hexose
molecule which act as chief respiratory
substrate.
• (d)Fructose:- It is directly converted into
fructose-6-phosphate by enzyme fructokinase
and then enters into the glycolysis.
2. FATS:- first convereted into fatty acids and
glycerol in presence of enzyme lipase.
Fatty acids being poorer in oxygen require more O2
for complete oxidation.
O2 absorption is more and CO2 liberation is less.
R.Q. is less than unity.
Glycerol + ATP
Glycerol-3 phosphate + ADP
Glycerol-3 phosphate+ NAD
phosphate + NADH+ H+
Dihydroxy acetone
Fatty acids are converted into acetyl coenzyme-A
which enters into the krebs cycle.
3.PROTEINS:- R.Q is less than unity.
Proteins are hydrolysed into amino acids.
Require more O2 and CO2 liberaton is less.
4. ORGANIC ACIDS:- like malic acid accumulate in
dark in some succulents plants(CAM).
Under continuous dark period malic acid is
converted into CO2 & H2O.
COOH
2
+ O2
4CO2+2H2O+60.2Kcal.
COOH
TYPES OF RESPIRATION
1. AEROBIC RESPIRATION:- oxidative breakdown
of respiatory substrates with the help of
atmospheric O2.
Complete breakdown of substrates into CO2
and water.
ANEROBIC RESPIRATION
Oxidation of respiratory substrates in absence
of O2.
Involves incomplete breakdown of respiratory
substrates.
Ethanol or lactic acid are produced & CO2 is
released at the end.
C6H12O6
2C2H5OH+2CO2+56 Kcal
MECHANISM OF ANEROBIC
RESPIRATION
• Involves conversion of glucose into ethanol &
CO2 in the alcoholic fermentation and the
conversion of glucose to lactic acid in the
muscles of animals and certain lactic acid
bacteria.
• The process does not require oxygen.
• First glucose is converted into pyruvic acid and
then converted into ethyle alcohol or lactic acid.
• Occures in cytosol.
EMBDEN – MEYERHOF – PARANAS
PATHWAY(GLYCOLYSIS)
• Anerobic respiration carried out by some
bacteria&fungi(e.g. yeast) is termed as
fermentation.
• ALCOHOLIC FERMENTATION:-Occures in some
fungi(e.g. yeast) and higher plants under
anerobic conditions.
• It occures in two steps:• The pyruvic acid is first of all decarboxylated to
acetaldehyde in presence of enzyme- pyruvic
acid decarboxylase.
LACTIC ACID FERMENTATION
• The breakdown of pyruvic acid yield lactic acid as an
end product.
• Pyruvic acid is reduced to lactic acid by
NADH + H in presence of enzyme lactic acid
dehydrogenase.COOH
COOH
COOH
C =O+ NADH+H
CHOH+ NAD
CH3
CH3
PYRUVIC ACID
LACTIC ACID
• COOH
C=O
CH3 CHO+ CO2
ACETALDEHYDE
CH3
Acetaldehyde is reduced to ethyle alcohol by
NADH + H, produced in glycolysis.
CH3CHO+ NADH+ H
C2H5OH + CO2
ETHYLE
ALCOHAL
PRODUCTION OF ATP IN ANEROBIC
RESPIRATION
• Glycolysis produces 4 ATP's and 2 NADH, but
uses 2 ATP's in the process for a net of 2 ATP
and 2 NADH.
MECHANISM OF AEROBIC
RESPIRATION
• Stepwise breakdown of respiratory substartes to
CO2 and H2O in presence of oxygen is referred to
as aerobic respiration.
• It involve 4 major stages:• (A) Glycolytic breakdown of glucose to pyruvic
acid.
• (B) Oxidative decarboxylation of pyruvic acid to
acetyl Co A.
• (C) Kreb’s cycle.
• (D) Terminal oxidation & phosphorylation.
(A) GLYCOLYSIS
(B) OXIDATIVE DECARBOXYLATION OF
PYRUVIC ACID TO ACETYE CO A
• 2 NADP are produced.
( 1 per pyruvate)
• 2 CO2 are released.
( 1 per pyruvate)
(C) KREBS CYCLE OR TCA CYCLE
• Aerobic oxidation of pyruvic acid through a
series of reactions was studied in detail by
Hans Krebs(1937).
PRODUCTION OF ATP IN KREBS CYCLE
•
•
•
•
•
•
•
8 NADH are produced.
2 FADH2 are produced.
2 ATP are produced.
8 NADH* 3 = 24 ATP
2 FADH2*2 = +4 ATP
2 ATP = +2 ATP
TOTAL = 30 ATP