Respiration | CEE Academy

📚

CHEMICAL EQUATION OF RESPIRATION

▢ Equations:

▢ Water Balance:

Table 1: Water use and production

Point	Number
\(H_2O\) used	10 molecules
In glycolysis	2 molecules
In Krebs cycle	8 molecules
\(H_2O\) produced	16 molecules

▢ Energy:

Table 1: Energy yield

Point	Value
Energy from glucose	686 kcal / earlier 673 kcal
Energy from 1 ATP	8.15 kcal
Earlier value of 1 ATP	7.3 kcal
Efficiency

▢ Nature: Respiration = oxidative process

▢ MCQ Point:

Q1.

Amount of energy given by 1 ATP molecule is

📚

TYPES OF RESPIRATION

▢ Based on Substrate:

Table 1: Respiration by substrate

Type	Substrate used
Floating / superficial respiration	Carbohydrate
Protoplasmic respiration	Lipid / fat / protein

▢ Based on Reactant:

Table 1: Aerobic vs anaerobic respiration

Feature	Aerobic respiration	Anaerobic respiration
Oxygen	Used	Not used
Water	Evolved; oxygen of water from atmospheric oxygen	Not evolved because oxygen not taken
Oxidation	Complete oxidation of substrate	Incomplete oxidation of substrate
Energy	More; 36/38 ATP	Less; 2 ATP

▢ ATP Ratio: Anaerobic : Aerobic ATP = \(\frac{1}{18}\) or \(\frac{1}{19}\)

📚

MECHANISM OF RESPIRATION

▢ Overview:

Table 1: Respiration overview

Parameter	Number
Total steps	30
Total phases	4
Total sites	4
Rule	Each phase occurs at different site

▢ Phases:

Glycolysis / EMP pathway
Oxidative decarboxylation / link reaction
TCA cycle / Krebs cycle / citric acid cycle
Oxidative phosphorylation / ETS / terminal oxidation

📚

GLYCOLYSIS / EMP PATHWAY

▢ Site: Cytoplasm

▢ Shortcut: \(Glucose\ (C_6H_{12}O_6) \rightarrow 2\ Pyruvic\ acid\ (2CH_3COCOOH)\)

▢ Net Reaction: \(Glucose + 2ADP + 2NAD^+ + 2H_3PO_4 \rightarrow 2Pyruvic\ acid + 2ATP + 2NADH_2 + 2H_2O\)

▢ Steps:

Table 1: Glycolysis steps

Step	Reaction / Product	Enzyme / Note
1	Glucose → Glucose-6-phosphate
2	Glucose-6-phosphate → Fructose-6-phosphate	Phosphohexoisomerase
3	Fructose-6-phosphate → Fructose-1,6-bisphosphate	Phosphofructokinase; phosphorylation; ATP used; rate-limiting step
4	Fructose-1,6-bisphosphate → 3-PGAl + DHAP	Aldolase; irreversible splitting
5	DHAP ⇌ 3-PGAl	Non-enzymatic / isomerisation step
6	3-PGAl → 1,3-diPGAl / 1,3-BPG
7	1,3-diPGA → 3-PGA	Phosphoglycerate kinase; ATP formed
8	3-PGA → 2-PGA	Phosphoglyceromutase
9	2-PGA → PEP	Enolase; \(H_2O\) released
10	PEP → Pyruvic acid

▢ Step Classification:

Table 1: Glycolysis step types

Type	Step(s)	Note
Phosphorylation	1, 3	2 ATP consumed
Irreversible	1, 3, 10	regulatory checkpoints
Non-enzymatic	5	Isomerisation
Oxidative	6	2 \(NADH_2\) produced
Dephosphorylation / ATP generation	7, 10	4 ATP produced
Rate-limiting	3	Enzyme: phosphofructokinase

Total steps = 10; total enzymes = 9

▢ Molecules Consumed:

Table 1: Glycolysis consumption

Molecule	Number
\(O_2\)	0
ATP	2
\(H_2O\)	Used in pathway as given in full equation

If oxygen is used, it enters Pasteur effect.

▢ Gross Molecules Produced:

Table 1: Glycolysis gross production

Molecule	Number
\(CO_2\)	0
\(H_2O\)	2
ATP	4
\(NADH_2\)	2
\(FADH_2\)	0

▢ Net Gain:

Table 1: Glycolysis net gain

Molecule	Number
\(CO_2\)	0
ATP	2
\(NADH_2\)	2
\(FADH_2\)	0

▢ Special Points:

•
Isomerism + phosphorylation → steps 1, 2, 3
•
Splitting → step 4
•
ATP generation → steps 7, 10
•
Glucose-6-phosphate = Robinson’s ester
•
•
Plants can convert fatty acid to sugars via glyoxylate cycle; animals cannot

📚

HEXOSE MONOPHOSPHATE SHUNT / PENTOSE PHOSPHATE PATHWAY

▢ Definition: Alternative pathway of glycolysis

▢ Use: Glucose utilization when glycolysis is inhibited

▢ Main Change: Direct oxidation of glucose-6-phosphate → 6-phosphogluconic acid → ribulose-5-phosphate

▢ Common Enzyme with Glycolysis: Hexokinase

▢ Energy:

Table 1: HMP shunt energy

Point	Value
\(NADH_2\) produced	12
ATP equivalent	36 ATP
ATP used	1
Net gain	35 ATP

▢ Site: Cytoplasm + chloroplast; not mitochondria

▢ Special Point: Resistant to cyanide

📚

OXIDATIVE DECARBOXYLATION / LINK REACTION

▢ Site: Outer mitochondrial membrane

▢ Reaction: \(2CH_3COCOOH + 2CoA + 2NAD^+ \rightarrow 2CH_3CO-CoA + 2CO_2 + 2NADH_2\)

▢ Flow: Pyruvic acid → acetaldehyde → acetyl coenzyme A

▢ Steps:

Table 1: Link reaction steps

Step	Process	Result
11	Decarboxylation	\(2CO_2\) removed
12	Oxidation + CoA addition	\(2NADH_2\) + 2 acetyl-CoA formed

▢ Molecules Consumed:

Table 1: Link reaction consumption

Molecule	Number
\(O_2\)	0
\(H_2O\)	0

▢ Molecules Produced / Net Gain:

Table 1: Link reaction products

Molecule	Number
\(CO_2\)	2
\(NADH_2\)	2
ATP equivalent from \(NADH_2\)	\(2 \times 3 = 6\ ATP\)

📚

TRICARBOXYLIC ACID CYCLE / KREBS CYCLE / CITRIC ACID CYCLE

▢ Site: Matrix of mitochondria

▢ Exception: Succinic dehydrogenase / succinate dehydrogenase found in inner mitochondrial membrane

▢ Nature: Amphibolic pathway

▢ Entry Reaction: \(Acetyl\ CoA + Oxaloacetic\ acid + H_2O \rightarrow Citric\ acid + CoA\)

▢ Cycle Steps:

Table 1: Krebs cycle steps

Step	Reaction / Product	Enzyme / Note
1 / 13	Acetyl-CoA + OAA → Citric acid
2 / 14	Citric acid → Cis-aconitic acid	Aconitase; \(H_2O\) released
3 / 15	Cis-aconitic acid → Isocitric acid	Aconitase; \(H_2O\) used
4 / 16	Isocitric acid → Oxalosuccinic acid
5 / 17		Decarboxylation; \(CO_2\) released
6 / 18
7 / 19	Succinyl-CoA → Succinic acid
8 / 20	Succinic acid → Fumaric acid
9 / 21	Fumaric acid → Malic acid	Fumarase; \(H_2O\) used
10 / 22	Malic acid → Oxaloacetic acid	Malate dehydrogenase; \(NADH_2\) formed

▢ Important Compounds:

Table 1: Important Krebs compounds

Compound	Point
Citric acid	Most stable compound
\(\alpha\)-ketoglutaric acid	Most unstable + most important compound
Oxaloacetic acid / OAA	Regenerated at end of cycle

▢ Step Classification:

Table 1: Krebs cycle step types

Type	Step(s)	Result
Hydration / \(H_2O\) consumed	1, 3, 7, 9	Total 4 steps
Dehydration / \(H_2O\) produced	2	Total 1 step
Oxidative steps	4, 6, 8, 10	Total 4 steps
\(NADH_2\) production	4, 6, 10	3 per cycle
\(FADH_2\) production	8	1 per cycle
ATP production	7	ATP through GTP
Decarboxylation	5, 6	\(CO_2\) produced

▢ Molecules Consumed per Glucose:

Table 1: Krebs cycle consumption

Molecule	Number
\(O_2\)	0
\(H_2O\)	8

▢ Gross Molecules Produced per Glucose:

Table 1: Krebs cycle gross production

Molecule	Number
\(CO_2\)	4
\(H_2O\)	2
ATP	2 through GTP
\(NADH_2\)	6
\(FADH_2\)	2

▢ Net Gain per Glucose:

Table 1: Krebs cycle net gain

Molecule	Number
\(CO_2\)	4
\(H_2O\)	-6 consumed
ATP	2
\(NADH_2\)	6
\(FADH_2\)	2

📚

OXIDATIVE PHOSPHORYLATION / ETS / TERMINAL OXIDATION

▢ Site: Inner mitochondrial membrane on \(F_1\) particle / oxysome

▢ Total Steps: 8

▢ Phosphorylation:

❖ Definition: Formation of ATP from ADP + inorganic phosphate by using energy

❖ Energy: 7.6 kcal

▢ Types of Phosphorylation:

Table 1: Phosphorylation types

Type	Meaning
Substrate-level phosphorylation	Direct ATP production at respiration site; no carrier needed
Chemiosmotic ATP formation
Oxidative phosphorylation	ATP formation with carriers

▢ Carriers:

•
Coenzymes → \(NADH_2\), \(FADH_2\)
•
Cytochromes

▢ Cytochrome Sequence: \(b \rightarrow c_1 \rightarrow c \rightarrow a \rightarrow a_3\)

▢ Cytochrome Ion: Fe

▢ Cyanide: Kills organism by inhibiting cytochrome oxidase

▢ Shuttle System:

Table 1: Shuttle systems

Shuttle	Electron transfer	ATP yield
Malate-aspartate shuttle		38 ATP; more efficient
Glycerol-phosphate shuttle		36 ATP

📚

ENERGY CALCULATION

▢ Total ATP:

Table 1: ATP yield

Respiration / Cell type	ATP
Anaerobic respiration	2
Aerobic respiration	38
Aerobic respiration in prokaryotes	38
Examples of prokaryotes	Mycoplasma, bacteria
Aerobic respiration in eukaryotes	36
Muscles + neurons	36
Heart / myocardial tissue, lungs, kidney	38

▢ Stepwise ATP Calculation:

Table 1: ATP calculation from 1 glucose

Step	Substrate ATP	Through \(NADH_2\)	Through \(FADH_2\)	Total ATP
Glycolysis	2	\(2 \times 3 = 6\) / \(2 \times 2 = 4\)	0	8 / 6
Oxidative decarboxylation	0	\(2 \times 3 = 6\)	0	6
Krebs cycle	2 through GTP	\(6 \times 3 = 18\)	\(2 \times 2 = 4\)	24
ETS	0	\(10 \times 3 = 30\)	\(2 \times 2 = 4\)	36 in eukaryotes / 38 in prokaryotes, heart, lungs, kidney

▢ Special Points:

•
Aerobic glycolysis → 8 ATP
•
Anaerobic glycolysis → 2 ATP
•
1 glucose → 2 pyruvic acid
•
Each pyruvic acid after complete aerobic metabolism → 15 ATP
•
Each acetyl-CoA after aerobic metabolism → 12 ATP
•
1 glucose → 1 glycolysis + 2 Krebs cycles
•
2 Krebs cycles per glucose → 24 ATP
•
Out of 4 ETS structural complexes, ATP produced at 3 complexes only

📚

ANAEROBIC RESPIRATION

▢ Basic Flow: \(Glucose \rightarrow Pyruvic\ acid \rightarrow End\ products\)

▢ ATP Yield: 2 ATP

▢ Pathways:

Table 1: Anaerobic pathways

Organism / Condition	Enzyme / Agent	End product
Yeast	Zymase	Ethyl alcohol + \(CO_2\)
Lactobacillus + muscles	Lactic acid fermentation	Lactic acid
Acetobacter	Acetaldehyde oxidation	Acetic acid
Clostridium butyricum	Butyric fermentation	Butyric acid

▢ Alcoholic Fermentation: \(Pyruvic\ acid \xrightarrow{Yeast/Zymase} Ethyl\ alcohol + CO_2\)

▢ Lactic Acid Fermentation: \(Pyruvic\ acid \xrightarrow{Lactobacillus/muscles} Lactic\ acid\)

▢ MCQ Point:

📚

RESPIRATORY QUOTIENT

▢ Definition: Ratio of volume of \(CO_2\) evolved to volume of \(O_2\) consumed in respiration

▢ Formula: \(RQ = \frac{Volume\ of\ CO_2\ evolved}{Volume\ of\ O_2\ consumed}\)

▢ Measurement: Ganong’s respirometer

▢ Depends On: Respiratory substrate

▢ RQ Values:

Table 1: Respiratory quotient values

Substrate / Condition	RQ	Example / Note
Carbohydrates	1	Floating respiration
Lipids / fats	<1; about 0.7	Protoplasmic respiration
Proteins	<1; about 0.8–0.9	Protoplasmic respiration
Organic acids	>1	Malic acid, oxalic acid
Succulent plants	0	Bryophyllum, Opuntia, Agave, Aloe
Anaerobic respiration	\(\infty\)	Oxygen not used; e.g., yeast

Q1.

During anaerobic respiration, Yeast converts glucose into: [IOM 2004, 2001]

📅IOM 2004, 2001

Q2.

Glycolysis takes place in:

Q3.

Respiration and Photosynthesis both require: [IOM 2002]

📅IOM 2002

Q4.

For anaerobic respiration, respiratory quotient is: [IOM 1996]

📅IOM 1996

Q5.

Fermentation is an………process: [IOM 1996]

📅IOM 1996

Q6.

The common phase between aerobic and anaerobic reaction is: [BPKIHS 2004]

📅BPKIHS 2004

Q7.

The following is an example of competitive inhibition of enzyme: [BPKIHS 2005]

📅BPKIHS 2005

Q8.

In aerobic respiration, respiratory quotient or respiratory ratio of 1 occurs with: [BPKIHS 2006]

📅BPKIHS 2006

Q9.

All of the following are features of glycolysis EXCEPT: [BPKIHS 2006]

📅BPKIHS 2006

Q10.

Kreb's cycle begins with: [BPKIHS 2006]

📅BPKIHS 2006

Q11.

The end products of fermentation are: [BPKIHS 2006]

📅BPKIHS 2006

Q12.

When the fats are the respiratory substrate the Respiratory Quotient (R.Q.) will be: [BPKIHS 2007]

📅BPKIHS 2007

Q13.

The end product of Kreb's cycle is: [BPKIHS 2007]

📅BPKIHS 2007

Q14.

Cyanide kill an organism by inhibiting: [BPKIHS 2007]

📅BPKIHS 2007

Q15.

The link between glycolysis and Kreb's cycle is: [MOE 2062]

📅MOE 2062

Q16.

Number of ATP from complete oxidation of 1 molecule of pyruvic acid is: [MOE 2062]

📅MOE 2062

Q17.

Which of the following leads to wastage of energy? [MOE 2060]

📅MOE 2060

Q18.

Pyruvic acid is

Q19.

The process in which CO_2 is released is: [MOE 2060]

📅MOE 2060

Q20.

The process in which protoplasm is constructed and destructed: [MOE-2003]

📅MOE-2003

Q21.

The end product of glycolysis is pyruvic acid having: [MOE 2058]

📅MOE 2058

Q22.

ATP is not released in: [MOE 2056, 2055]

📅MOE 2056, 2055

Q23.

Aerobic respiration inside the cell occurs in: [MOE 2052]

📅MOE 2052

Q24.

Respiratory opening of the plant is: [MOE 2052]

📅MOE 2052

Q25.

ADP differs from ATP in having

Q26.

The plant which performs Crassulacean Acid Metabolism is

Q27.

The production of ATP by oxidative phosphorylation is driven by energy from: [IE 2006]

📅IE 2006

Q28.

Photorespiration occurs in: [IOM 2014]

📅IOM 2014

Q29.

The electron transfer system is present in [IOM 2014]

📅IOM 2014

Q30.

In prokaryotes the total number of ATP produced in aerobic respiration is [IOM 2014]

📅IOM 2014

Q31.

Alcohol fermentation takes place in the presence of: [IOM 2013]

📅IOM 2013

Q32.

Pyruvic acid is changed into CO_2 and H_2 O in [IOM 2013]

📅IOM 2013

Q33.

Glycolysis occurs in

Q34.

Kreb's cycle occurs in [MOE 2013]

📅MOE 2013

Q35.

Respiration is performed by all the living cells of the plant [MOE 2068]

📅MOE 2068

Q36.

Glycolysis takes place in [MOE 2068]

📅MOE 2068

Q37.

Kreb's cycle is involved in [MOE 2010]

📅MOE 2010

Q38.

Oxidation of glucose takes place in [MOE 2010]

📅MOE 2010

Q39.

In cyclic phosphorylation, main product is [MOE 2010]

📅MOE 2010

16Respiration

Table 1: Water use and production

Table 1: Energy yield

Table 1: Respiration by substrate

Table 1: Aerobic vs anaerobic respiration

Table 1: Respiration overview

Table 1: Glycolysis steps

Table 1: Glycolysis step types

Table 1: Glycolysis consumption

Table 1: Glycolysis gross production

Table 1: Glycolysis net gain

Table 1: HMP shunt energy

Table 1: Link reaction steps

Table 1: Link reaction consumption

Table 1: Link reaction products

Table 1: Krebs cycle steps

Table 1: Important Krebs compounds

Table 1: Krebs cycle step types

Table 1: Krebs cycle consumption

Table 1: Krebs cycle gross production

Table 1: Krebs cycle net gain

Table 1: Phosphorylation types

Table 1: Shuttle systems

Table 1: ATP yield

Table 1: ATP calculation from 1 glucose

Table 1: Anaerobic pathways

Table 1: Respiratory quotient values

More CEE preparation resources