Session Objectives : Session Objectives To Know the types of respiration
To discuss RQ
To discuss Glycolysis
Types of Respiration : Types of Respiration Aerobic Anaerobic
Respiratory Ratio or Quotient : Respiratory Ratio or Quotient RQ = Volume of CO2 evolved / Volume of O2 consumed RQ is a useful index of the types of substrates used in respiration and the subsequent use of respiratory
energy to support biosynthesis
Slide 4 : CarbohydratesEqual amounts of CO2 and O2 are evolved and consumed RQ = 6CO2 / 6O2
= 1 FatsRQ is less than 1 when fats are utilized in respiration RQ = 102CO2 / 145O2
= 0.7
Slide 5 : Organic acidsRQ is more than 1 when organic acids are used.
Organic acids possess more oxygen atoms than
carbohydrates, thus less oxygen is required for oxidation RQ = 4CO2 / 1O2
= 4 In anaerobic respiration, carbon dioxide is evolved
but oxygen is not utilized RQ = 4CO2 / 0 O2
= Infinity RQ for CAM plants = ???
Respiratory Pathway : Respiratory Pathway
Slide 7 : FOOD
Glycolysis : Glycolysis Also Known as EMP pathway ( Embden Meyerhof Parnas)
Occurs in Cytoplasm
Does not give off CO2 and does not require O2
Simple sugar enter into the cycle 2 Pyruvi acid + 2 ATP + 2 NADH + H+ C6H12O6
Step 1 : Step 1 Enzyme Hexokinase removes phosphate
from ATP and binds to glucose molecule
forming glucose-6-phosphate The suffix Kinase means that a phosphate
group will be removed Glucose + ATP Glucose-6-P + ADP
Step 2 : Step 2 Enzyme Phosphoglucoisomerase
glucose-6-phosphate into
fructose-6-phosphate The suffix isomerase means that
only structure will change Glucose-6-P Fructose-6-P
Step 3 : Step 3 Enzyme Phosphofructokinase transfer
phosphate from ATP to fructose-6-phosphate
forming fructose-1,6-biphosphate Fructose-6-P + ATP Fructose-1,6-diP + ADP
Step 4 : Step 4 Enzyme Aldolases breaks fructose-1,6-
biphosphate into 2 mol. of 3-C compound
DHAP & Glyceraldehyde-3-phosphate Fructose-1,6-diP + ADP Isomerase converts DHAP into its isomer
Glyceraldehyde-3-p
Step 5 : Step 5 Two molecules of glyceraldehyde-3-p
gain phosphate and oxidized forming
2 mol. of NADH + H+ The reaction is catalyzed by
triosephosphate dehydrogenase Glyceraldehyde-3-p 1,3-diphosphoglyseric acid
Step 6 : Step 6 Enzyme Phosphoglycerokinase
transfer the phosphate group
from 1,3-diPGA to ADP forming ATP 1,3-diphosphoglyseric acid 3-phosphoglyseric acid
Step 7 : Step 7 Enzyme Phosphoglyceromutase
changes the position of phosphate
from carbon no. 3 to 2 forming 2-PGA 3-phosphoglyseric acid 2-phosphoglyseric acid
Step 8 : Step 8 Enzyme Enolase releases water molecules
from 2-PGA forming phosphoenol pyruvate 2-phosphoglyseric acid Phosphoenol pyruvate
Step 9 : Step 9 Enzyme Pyruvate Kinase releases phosphate
molecules from phosphoenol pyruvate
and ATP is formed Phosphoenol pyruvate Pyruvate
Glycolysis : Glycolysis
Product of Glycolysis : Product of Glycolysis 2 molecules of Pyruvic acid ( 3 C comound)
2 ATP
2 H2O
2 (NADH + H+) Energetics In the absence of O2 No. of ATP produced = 4
No. of ATP consumed = 2 In the presence of O2 No. of ATP produced = 4
No. of ATP consumed = 2
Gain = 4 – 2 = 2
2 (NADH + H+) = 2 x 3 = 6 Net Gain = 4 – 2 = 2 Net Gain = 2 + 6 = 8
In Glycolysis H2O is release during the formation of : In Glycolysis H2O is release during the formation of 2-PGA
PEP
Pyruvate
1,3-diPGA Illustrative Problem
Which of the following enzyme of Glycolysis is responsible for the spliting of the compound fructose-1,6-diP : Which of the following enzyme of Glycolysis is responsible for the spliting of the compound fructose-1,6-diP Enolase
Aldolase
Phosphoglyceromutase
Phosphofructokinase Illustrative Problem
How many ATP will be formed through Glycolysis by one molecule of DHAP : How many ATP will be formed through Glycolysis by one molecule of DHAP 4
5
6
8 Illustrative Problem 1 DHAP will form 2 ATP & 1 NADP + H+
Hence, Net ATP formation = 2 + 3 = 5
Link Reaction : Link Reaction Occurs in mitochondrial matrix
CoA, NAD+, Lipoic acid, Mg++, TPP are needed
Oxidative decarboxylation
2-C compound Acetyl CoA & NADH2 is formed Pyruvate Acetyl CoA
Kreb Cycle : Kreb Cycle Occurs in Mitochondrial matrix
OAA act as acceptor for Acetyl CoA
4 oxidation steps – NADH2 is formed in 1st, 2nd & 4th oxidation step and FADH2 is formed in 3rd oxidation step
Slide 25 :
Step 1: Condensation : Step 1: Condensation 2-carbon compound, acetyl-S-CoA, participates in a condensation reaction with the four-carbon compound, oxaloacetate, to produce citrate
Reaction is catalyzed by enzyme citrate synthatase OAA (4-C) Citrate (6 –C)
Step – 2 :Isomerization of Citrate : Step – 2 :Isomerization of Citrate It involves a sequential dehydration and hydration reaction, to form the D-Isocitrate isomer with cis-Aconitase as the intermediate
A single enzyme, Aconitase, performs this two-step process
Step 3 : 1st Oxidation : Step 3 : 1st Oxidation The Krebs cycle contains two oxidative decarboxylation steps; this is the first one
The reaction is catalyzed by the enzyme Isocitrate dehydrogenase Icocitrate a- ketoglutrate
Step 4 : 2nd Oxidation : Step 4 : 2nd Oxidation This step is performed by a multi-enzyme complex, the a-Ketoglutarate Dehydrogenation Complex a- ketoglutrate Succnyl CoA
Step 5: Substrate-Level Phosphorylation : Step 5: Substrate-Level Phosphorylation Succnyl CoA Succinate GDP GTP
Step 6: Flavin-Dependent Dehydrogenation : Step 6: Flavin-Dependent Dehydrogenation 3rd oxidation step
FAD act as hydrogen acceptor
Succinate dehydrogenase is a membrane bounded enzyme Succinate Fumarate FAD FADH2
Step 7: : Step 7: Fumarate is converted into Malate
Reaction is catalysed by enzyme Enolase Step 8: 4th Oxidation step Reaction is catalysed by enzyme Malate dehydrogenase Malate OAA NAD NADH2
Energetics : Energetics No. of NADH2 / cycle = 3; 3 x 3 = 9 ATP
No. of FADH2 / cycle = 1; 1 x 2 = 2 ATP
Substrate level ATP / cycle = 1 ATP
Total ATP = 12 ATP/cycle
Slide 34 :