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CBSE Questions for Class 11 Medical Biology Respiration In Plants Quiz 13 - MCQExams.com
CBSE
Class 11 Medical Biology
Respiration In Plants
Quiz 13
Each molecule of pyruvic acid entering the Krebs cycle produces?
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0%
2 molecules of
C
O
2
C
O
2
.
0%
3 molecules of
C
O
2
C
O
2
.
0%
1 molecules of
C
O
2
C
O
2
.
0%
5 molecules of
C
O
2
C
O
2
.
How many carbon atoms are there in substances labelled as P,Q,R and S respectively in the given representation of Krebs' cycle?
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0%
PQRS: 4,3,6,4
0%
PQRS: 3, 4, 4, 6
0%
PQRS: 4,3, 4, 6
0%
PQRS: 3,4,6,4
In Kreb's cycle formation of ___________________.
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0%
34
34
ATP takes place
0%
38
38
ATP takes place
0%
15
15
ATP from each acetyl Co-A takes place
0%
12
12
ATP from each acetyl Co-A takes place
(
24
A
T
P
)
(
24
A
T
P
)
Which one is the positive modulator of glycolysis?
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0%
A
T
P
A
T
P
0%
A
D
P
A
D
P
0%
N
A
D
H
N
A
D
H
0%
F
A
D
H
F
A
D
H
Explanation
ADP is the positive modulator of glycolysis. It activates an enzyme called phosphofructokinase (PFK-1) which speeds up the formation of end products. So, the correct answer is option B.
Identify X, Y and Z in the given diagram of citric acid cycle and select the correct option.
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0%
X-GTP, Y-
N
A
D
H
2
N
A
D
H
2
, Z-
F
A
D
H
2
F
A
D
H
2
0%
X-
F
A
D
H
2
F
A
D
H
2
, Y-
N
A
D
H
2
N
A
D
H
2
, Z-GTP
0%
X-
N
A
D
H
2
N
A
D
H
2
, Y-
F
A
D
H
2
F
A
D
H
2
, Z-GTP
0%
X-
C
O
2
C
O
2
, Y-
N
A
D
H
2
N
A
D
H
2
, Z-ADP
Explanation
The given diagram is of citric acid cycle. It is also called as Krebs cycle. When isocitric acid is converted to
α
-ketoglutaric acid, NAD
+
+
is converted to NADH
2
2
and CO
2
2
is liberated. This reaction is carried out by enzyme isocitrate dehydrogenase. This
α
-ketoglutaric acid undergoes oxidative decarboxylation and succinyl CoA is generated with liberation of NADH
2
2
and CO
2
2
. This reaction is carried out by enzyme α-Ketoglutarate dehydrogenase. Succinyl CoA undergoes phosphorylation to produce succinic acid. In this step, GTP is formed from GDP. Succinic acid then undergoes oxidation to produce Fumaric acid by enzyme succinate dehydrogenase. FADH
2
2
is generated from FAD in this step.
Thus, the correct answer is 'X-NADH
2
2
, Y-FADH
2
2
, Z-GTP.'
In the conversion of pyruvic acid to acetyl coenzyme A, pyruvic acid is:
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0%
Oxidized
0%
Reduced
0%
Isomerised
0%
Inactivated
Explanation
In Krebs cycle pyruvate enters mitochondria through a transport protein, here oxidative decarboxylation ( oxidation as well as removal of carbon dioxide ) occurs to produce co
2
2
which later combines with sulfur which has coenzyme A to form acetyl CoA.
So, the correct option is ' oxidized'.
Choose the correct answers from the alternatives given :
Which one of the following is the link between glycolysis and Krebs cycle?
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0%
Acetyl coenzyme A
0%
Phosphoenolpyutvic acid
0%
Citric acid
0%
Acetyl acetic acid
Explanation
The link between glycolysis and Krebs cycle is called as link reaction where pyruvate is oxidized into acetyl CoA which is the main product of pyruvate dehydrogenase. This reaction requires five coenzymes and three enzymes.
So, the correct option is ' Acetyl coenzyme A'.
Choose the correct answers from the alternatives given :
The first process in breaking down glucose is
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0%
the Krebs cycle
0%
glycolysis
0%
electron transport system
0%
fermentation
Explanation
The process of breaking down of glucose is cellular respiration. It has three steps :
Glycolysis
Krebs cycle
Terminal oxidation
Glycolysis is the first basic step where oxygen is not required, it takes place in the cytoplasm of the cell. In this process glucose molecule is broken down into two molecules of pyruvate by the series of enzymatic reaction to obtain energy which is followed by Krebs cycle and then electron transport system while fermentation is anaerobic respiration, it does not require oxygen.
So, the correct option is ' glycolysis'.
Which process produces both NADH and
F
A
D
H
2
F
A
D
H
2
?
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0%
Krebs cycle
0%
Glycolysis
0%
Electron transport system
0%
Fermentation
Explanation
In respiration energy is produced by three processes :
Glycolysis
Krebs cycle
Electron transport system
In glycolysis, glucose molecule is broken into two molecules of pyruvate where NADH and ATP are produced. In Krebs cycle acetate is derived from pyruvate by the process of oxidation and degradation, here ATP, NADH, and FADH
2
2
are produced.
So, the correct option is ' Krebs cycle'.
Choose the correct answers from the alternatives given :
Which process must occur before fermentation?
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0%
Krebs cycle
0%
Glycolysis
0%
Electron transport system
0%
The transition reaction
Explanation
Fermentation is anaerobic respiration in which organic foods are degraded incompletely in the absence of oxygen.
G glycolysis is the basic step of cellular respiration, it occurs in both aerobic as well as an anaerobic type of respiration. It is the common first step in both the type of respiration i.e; it must occur before the Krebs cycle as well as before fermentation.
So, the correct option is ' Glycolysis'.
Choose the correct answers from the alternatives given :
The carbon dioxide we exhale is produced in
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0%
glycolysis
0%
electron transport system
0%
lactate fermentation
0%
Krebs cycle
Explanation
In aerobic respiration three processes occurs out of which two of the processes i.e ; glycolysis and electron transport system does not produce carbon dioxide while in Krebs cycle pyruvate is degraded into molecules of water and carbon dioxide which is obtained by the process of respiration in human beings and is exhaled by humans and animals and is taken up by the plants for the completion of cellular respiration .
So, the correct option is ' Krebs cycle'.
Acetyl-CoA is produced from
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0%
pyruvate and a coenzyme
0%
citric acid and a coenzyme
0%
ATP and pyruvate
0%
CO2 and pyruvate
Explanation
The process of production of Acetyl CoA is called as transition reaction or link reaction, it links the process of glycolysis ( where glucose is broken down to form two molecules of pyruvate )
to the process of Krebs cycle where pyruvate undergo oxidative decarboxylation and then combines to sulfur-containing coenzyme A to form acetyl CoA.
So, the correct option is ' pyruvate and a coenzyme'.
Fatty acids enter cellular respiration as
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0%
one-carbon fragments
0%
two-carbon fragments
0%
three-carbon fragments
0%
long chain-carbon fragments
Explanation
Cellular respiration is the process in which sugar is broken down to obtain energy. The first step of fatty acid in cellular respiration is the entering of acetyl CoA in the Krebs cycle which is after the process of glycolysis. Acetyl CoA is a fatty acid which is two carbon compounds product which gets condensed by an enzyme and forms the first product of Krebs cycle which is six carbon compound.
So, the correct option is ' two-carbon fragments'.
Choose the correct answers from the alternatives given :
In an eukaryotic cell, TCA cycle and electron transport system take place within
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0%
nucleolus
0%
peroxisomes
0%
mitochondria
0%
stroma
Explanation
In eukaryotic cells the cellular respiration occurs in three steps :
Glycolysis
Krebs cycle
Terminal oxidation
Glycolysis occurs in the cytoplasm of the cell where glucose molecule is breakdown into pyruvate, this pyruvate enters the mitochondria through the inner mitochondrial membrane and then it starts Krebs cycle which is later followed by the electron transport system.
so, the correct option is ' mitochondria'.
Choose the correct answers from the alternatives given :
Mitochondria are called the powerhouses of the cell. Which one of the following observations supports this statement?
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0%
Mitochondrion is a cell organelle that possesses a double membrane
0%
Mitochondria contain ATP
0%
The enzymes of the Krebs cycle and the cytochromes are found in mitochondria
0%
Mitochondria are found in almost all kinds of cells
Explanation
Mitochondria are the tiny cell organelles present in the cytoplasm which are involved in the release of energy from food, thus they are called as the powerhouse of the cell. Here cellular respiration occurs which requires the enzymes and cytochromes of aerobic respiration.
So, the correct statement is ' The enzymes of the Krebs cycle and the cytochromes are found in mitochondria'.
Which process produces alcohol or lactate?
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0%
Krebs cycle
0%
Glycolysis
0%
Electron transport system
0%
Fermentation
Explanation
Respiration is of two types :
Aerobic respiration- here oxygen is required for the process to occur. It occurs in the following three steps :
Glycolysis
Krebs cycle
Terminal oxidation
Anaerobic respiration- here oxygen is not required in the process of respiration. In this process, organic food is incompletely degraded without the use of oxygen which later produces ethanol or lactic acid as the end product.
So, the correct option is ' Fermentation'.
Choose the correct answers from the alternatives given :
The end product of alcoholic fermentation is:
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0%
ethanol or lactic acid
0%
acetaldehyde
0%
water and
C
O
2
C
O
2
0%
pyruvic acid
Explanation
Alcoholic fermentation is called as lactic acid fermentation, it is anaerobic respiration that does not require oxygen. It is the process of release of energy by incomplete degradation of organic food hence end products are never fully inorganic. First glycolysis occurs and forms two molecules of pyruvate after that fermentation occurs, no oxygen involved and later forms ethyl alcohol and lactic acid.
So, the correct option is ' ethanol or lactic acid'.
Choose the correct answers from the alternatives given :
Which of these is not true of fermentation?
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0%
Net gain of only two ATP
0%
Occurs in cytosol
0%
NADH donates electrons to electron transport system
0%
Begins with glucose
Explanation
Fermentation is the process that takes place after the glycolysis in the cells where the anaerobic respiraton occurs due to absence or lack of oxygen.
Pyruvic acid which is formed at the end of the glycolysis by the break down of the glucose molecule enters the fermentation reaction in the anaerobic cells.
During fermentation reaction the pyruvic acid is converted to lactic acid and one molelcule of NADH is formed per molecule of pyruvic acid.
This molecule of NADH will only form ATP when it will undergo oxidative phosphorylation in the electron transport chain which takes place in mitochondria, but for this process presence of oxygen is required so the organisms or the cells performing anaerobic respiration cannot perforem this process therefore the NADH formed will not donate electron to the ETS and no ATP will be formed by that.
Therefore the answer option 'NADH donates electrons to electron transport system' is correct.
The form in which carbon leaves the citric acid cycle is
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0%
Acetalehyde
0%
Carbon dioxide
0%
Ethanol
0%
None of these
Explanation
Pyruvic acid is a 3 carbon molecule which is first oxidised to acetyl coA after reacting with coenzyme A. During this reaction one molecule of NADH and one molecule of Carbon dioxide is released.
Second molecule of carbon dioxide along with a molecule of NADH is released when 6 carbon citric acid is converted to ketoglutaric acid .
Third molecule of carbon dioxide is released during conversion of ketogluataric acid to succinic acid along with the release of NADH and GDP.
Thus all three molcules of carbon present in the pyruvic acid are released in the form of carbon dioxide from the kerb cycle.
Therefore the correct answer is option 'Carbon dioxide'.
Choose the correct answers from the alternatives given :
Which of these pairs of processes are anaerobic?
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0%
Fermentation and glycolysis
0%
Fermentation and the Krebs cycle
0%
Glycolysis and the Krebs cycle
0%
The Krebs cycle and the electron transport system
Explanation
Respiration is of two types -
Aerobic respiration - It is the process of complete oxidation of organic foods into carbon dioxide and water in the presence of oxygen. it has three steps ;
Glycolysis - It occurs in the cytoplasm in which glucose breaks into two molecules of pyruvate. It occurs in both aerobic and anaerobic respiration.
Krebs cycle occurs in the mitochondria where oxidative decarboxylation of pyruvate takes place to form acetyl CoA.
Electron transport system - Here series of coenzymes and cytochromes acts as a passage of electron.
Anaerobic respiration - It is the process of incomplete oxidation of organic foods. oxygen is not utilized in this process, this occurs in the process of fermentation.
So, the correct option is ' Fermentation and glycolysis'.
Choose the correct answers from the alternatives given :
The citric acid cycle
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0%
must occur twice for each glucose molecule metabolised
0%
produces 2 ATP directly from the cycle intermediates
0%
produces 4 carbon dioxide molecules per glucose molecule
0%
all of the above
Explanation
After glycolysis 2 molecules of 3 carbon pyruvate are formed from one molecule of Glucose.
These pyruvate molecules then are converted to acetyl coA which enters the kerb cycle or the citric acid cycle
After one acetyl coA molecule undergoes the cycle 4 molecules of NADH, one molecule of FADH and on molecule of ATP is formed.
This is the number of the molecules formed from one pyruvate when it undergoes one cycle.
Therefore one glucose molecule forms 2 pyruvates which means that at the end of the kerb cycle one glucose molecule will form 2 ATP
Also for the formation of carbon dioxide; 2 molecules of carbon dioxide are formed, first one during the converstion of citric acid to ketoglutaric acid and second during the conversion of ketoglutaric acid to succinic acid. Whixh means that each pyruvic acid gives 2 molecules of carbon dioxide per cycle.
Therefore one molecule of glucose will give 4 molecules of carbon dioxide as for a glucose molecule to be completed metabolised it has to undergo kerb cycle twice.
Therefore the answer 'all of the above' is correct.
Choose the correct answers from the alternatives given :
In a eukaryotic cell, most of the enzymes of the Krebs cycle are located in the
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0%
intermembrane space
0%
mitochondrial matrix
0%
inner mitochondrial membrane
0%
plasma membrane
Explanation
Kerb cycle is a part of aerobic respiration.
After the reaction of glyolysis that takes place in cytoplasm which ends in formation of pyruvic acid.
The pyruvic acid is converted to Acetyl CoA which will enter the kerb cycle for further reactions.
For the further reaction in eukaryotic cells the acetyl coA will enter the mitochondria
This kerb cycle takes place in mitochondria and so that all the enzymes that are required for the cycle are present in the mitochondrial matrix.
Therefore the correct answer is option 'mitochondrial matrix'.
The enzyme that is not found in a
C
3
C
3
plant is
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0%
RuBP Carboxylase
0%
PEP Carboxylase
0%
NADP reductase
0%
ATP synthase
Explanation
PhosphoEnolPyruvate (PEP) carboxylase is present in the mesophyll cells of the
C
4
C
4
plants and catalyse the conversion PEP to OxaloAecetate. (OAA), the first 4C stable compound formed in
C
4
C
4
plants formed by the acceptance of atmospheric
C
O
2
C
O
2
by PEP in presence of PEP carboxylase.
So, the correct answer is '
PEP Carboxylase'
In which of the following processes is acetyl CoA not involved?
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0%
Fatty acid breakdown
0%
Embden-Meyerhof pathway
0%
Fatty acid synthesis
0%
Transamination
Explanation
Fatty acid break down takes place in the condition of starvation where the fatty acid is broken down to acetyl CoA which takes part in kerb cycle and provides further energy to the body.
Embden meyerhof pathway is the glycolysis pathway which will produce pyruvic acid at the end of the process that converts in to acetyl CoA which takes part in kerb cycle.
Sometimes when fatty acid are required the acetyl CoA is taken out of the pathway and converted to fatty acid by the fatty acid synthesis pathway.
This is done by a reaction between acetyl CoA and NADPH.
Transamination is the reaction which takes place for the formation of the amino acid by the transfer of the amino group from one amino acid to the other. And acetyl coA does not take part in this reaction for the formation of amino acid.
Therefore the answer option 'Transamination' is correct.
Fatty acids are broken down to
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0%
Pyruvate molecules, which take electrons to the electron transport system
0%
Amino acids, which excrete ammonia
0%
Acetyl groups, which enter the Krebs cycle
0%
All of the above
Explanation
During the time of starvation or in the fasting state when then the level of glucose in the blood is less the whole metabolism process gives priority to see that the brain and the other important organs are providedwith glucose.
While other organs use other material such as fatty acid and protein for the synthesis of energy by the kerb cycle.
Fatty acid is the main component that is used in the energy synthesis after carbohydrates as it can be easily stored whereas protein can be used for the energy synthesis but that cannot be stored in the body.
The fatty acid also cannot direct enter the kerb cycle therefore they are to be broken down to acetyl CoA which is done by the process of beta oxidation.
Long chain of fatty acid are broken down to the 2 carbon molecule of Acetyl CoA for example Palmitoyl acid is converted to 8 molecules of Acetyl CoA after beta oxidation.
After bein converted it can enter the kerb cycle.
Therefore the answer option C is correct.
Choose the correct answers from the alternatives given :
The pathway of aerobic respiration is completed in the
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0%
cytoplasm
0%
mitochondrion
0%
plasma membrane
0%
nucleus
Explanation
Aerobic respiration is the respiration that takes place in the presence of oxygen.
The process of glycolysis takes place in the cytoplasm of the cell after which 2 molecules of pyruvic acid is formed per molecule of glucose.
After which the molecule of pyruvic acid is converted to acetyl CoA and then it enters the kerb cycle which takes place in the mitochondrial matrix as all the enzymes that are used for the process of kerb cycle is present in mitochondria.
Therefore the process of aerobic respiration starts in the cytoplasm and ends in the mitochondria.
Therefore the correct answer is the 'mitochondrion'.
State whether the following statements are true or false.
In the conversion of pyruvic acid to acetyl coenzyme A, pyruvic acid is reduced.
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0%
False
0%
True
Explanation
Pyruvic acid is the end product of the Glycolysis which takes place in cytoplasm. After which it is transported to mitochondria where it takes part in Kerb cycle.
Before entering the Kerb cycle the pyruvic acid reacts with Coenzyme A and undergoes Oxidative Decarboxylation forming Acetyl CoA and releasing a molecule of carbon dioxide.
Acetyl CoA reacts with oxaloacetic acid forming citric acid which goes under a cycle of reaction releasing ATP, NADH and ends with the regeneration of oxaloacetic acid.
Therefore the above sentence is false and the answer option 'False' is correct.
State whether the following statements are true or false.
The final electron acceptor in glycolysis is oxygen.
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0%
True
0%
False
Explanation
Glycolysis is an oxygen-independent biochemical process that takes place in the cytoplasm.
The electron transport chain is a different pathway that is responsible for oxidative phosphorylation and generation of ATP and the oxygen is the ultimate electron acceptor.
So, the correct statement is '
The final electron acceptor in the electron transport chain is oxygen.
'.
The given statement is false.
State whether the following statements are true or false.
Fermentation follows glycolysis in some cells when oxygen is not available.
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0%
True
0%
False
Explanation
When oxygen is not available to cells due to rapid metabolism without recovery, instant energy is produced by Fermentation but in fewer amounts.
The pyruvate formed is converted into lactic acid during fermentation in the absence of oxygen.
So, the correct statement is '
Fermentation follows glycolysis in some cells when oxygen is not available.
'.
Which statement is wrong for Kreb's cycle?
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0%
There is one point in the cycle where
F
A
D
+
F
A
D
+
is reduced to
F
A
D
H
2
F
A
D
H
2
0%
During conversion of succinyl coA to succinic acid, a molecule of GTP is synthesised
0%
The cycle starts with condensation of acetyl group (acetyl CoA) with pyruvic acid to yield citric acid
0%
There are three points in the cycle where
N
A
D
+
N
A
D
+
is reduced to
N
A
D
H
+
H
+
N
A
D
H
+
H
+
Explanation
Kerb's cycle also known as citric acid cycle
It begins with condensation of an acetyl group (acetyl CoA (2C)) with oxaloacetic acid (or pyruvic acid) (4C) to form citric acid (6C) with the addition of water molecule (hydration).
Hence the correct answer is the option 'The cycle starts with condensation of an acetyl group (acetyl CoA) with pyruvic acid to yield citric acid'.
The flow chart given below shows the steps in glycolysis. Select the option that correctly fills in the missing steps A, B, C, and D.
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0%
A-Fructose-6-phosphate; B-Fructose-1,6-biphosphate; C- 3-PGAL; D-1,3-biphosphoglyceric acid
0%
A- Fructose -1,6-biphosphate ; B- 3-PGAL ; C- 1,3-biphosphoglyceric acid ; D-3 PGAL
0%
A- 3PGAL ; B-1,3 biophosphoglyceric acid ; C-3PGAL ; D- Frutose-1,6-biphosphate
0%
A- Fructose -1,6-biophosphate ; B-Fructose -6- phosphate ; C-PGAL ; D-1,3- biphosphoglyceric acid
Explanation
Glycolysis is a biochemical reaction in which one glucose molecule into 2 pyruvate molecules.
As shown in the diagram showing the step-by-step biochemical reaction in glycolysis. According to this A - Fructose-6-phosphate, B - Fructose-1,6-Biphosphate; C- 3-PGAL; D - 1,3-biphosphoglyceric acid.
So, the correct answer is (A).
Which of the given enzyme is not concerned with the irreversible reaction of glycolytic pathway?
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0%
Phosphofructo kinase
0%
Hexokinase
0%
Triose phosphate mutase
0%
Pyruvate kinase
Explanation
In glycolysis, the reactions catalyzed by hexokinase, phosphofructokinase, and pyruvate kinase are virtually irreversible; hence, these enzymes would be expected to have regulatory as well as catalytic roles.
So the correct answer should be option "
Triose phosphate mutase"
The three boxes in this diagram represent the three major biosynthetic pathways in aerobic respiration. Arrows represent net reactants or products.
Arrows numbered
4
4
,
8
8
and
12
12
can all be
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0%
H
2
O
H
2
O
0%
F
A
D
F
A
D
or
F
A
D
H
2
F
A
D
H
2
0%
NADH
0%
ATP
Explanation
38 ATP molecules are produced during each cycle of
cellular respiration. The arrowed numbered 4, 8 and
12 represents the number of ATP produced during
each pathways (Glycolysis→Kreb’s cycle) of cellular
respiration.
So, the correct option is 'ATP'.
Study the given steps of glycolysis and identify the enzymes (i), (ii), and (iii) responsible for carrying out these steps.
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0%
Phosphohexose - (i), Phosphofructokinase - (ii), Aldolase - (iii)
0%
Hexokinase - (i), Phosphofructokinase - (ii), Aldolase - (iii)
0%
Phosphohexose - (i), Hexokinase - (ii), Phosphofructokinase - (iii)
0%
Aldolase - (i), Phosphofructokinase - (ii), Phosphohexose isomerase - (iii)
Explanation
The four regulatory enzymes are hexokinase, phosphohexose isomerase, phosphofructokinase, and, aldolase, etc.
Glucose gets converted into glucose-6-phosphate with the help of hexokinase.
Then, glucose-6-phosphate gets converted into fructose-6-phosphate with the help of phosphohexose isomerase.
Fructose-6-phosphate gets converted into fructose-1,6-biphosphate with the help of phosphofructokinase.
Fructose-1, 6-biphosphate gets converted into glyceraldehyde-3-phosphate with the help of aldolase.
So, the correct answer is (A).
Select the correct option:
Identify A,B and C in the given reaction of lactic acid fermentation and select the correct option.
P
y
r
u
v
i
c
a
c
i
d
+
A
L
a
c
t
a
t
e
d
e
h
y
d
r
o
g
e
n
a
s
e
⇌
F
M
N
,
Z
n
2
+
B
+
C
Report Question
0%
A-NADH ; B- Lactic acid +
C
O
2
; C-
N
A
D
+
0%
A-NADH ; B- Lactic acid ; C-
N
A
D
+
0%
A-
N
A
D
+
; B- Lactic acid ; C- NADH
0%
A-
N
A
D
+
; B-Lactic acid +
C
O
2
; C-NADH
Explanation
from the diagram, we can say
So, the correct option is 'A-NADH; B- Lactic acid; C- NAD+'.
The end product of glycolysis is _____________.
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0%
Pyruvic acid
0%
Glucose
0%
Ethyl alcohol
0%
C
O
2
Explanation
Glycolysis is the first step of aerobic respiration in which one glucose molecule gets converted into two pyruvic acid. (as shown in the diagram).
Which is true about the end products of glycolysis?
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0%
2
p
y
r
u
v
i
c
a
c
i
d
+
2
A
T
P
+
2
N
A
D
H
2
0%
2
p
y
r
u
v
i
c
a
c
i
d
+
2
N
A
D
H
2
0%
1
p
y
r
u
v
i
c
a
c
i
d
+
2
A
T
P
+
2
N
A
D
H
2
0%
2
p
y
r
u
v
i
c
a
c
i
d
+
1
A
T
P
+
1
N
A
D
H
2
Explanation
In glycolysis, two molecules of ATP are consumed during two phosphorylation reactions to form fructose 1, 6-biphosphate. In return, four molecules of ATP are produced by substrate-level phosphorylation (conversion of 1, 3-biphosphoglycerate to 3-phosphoglycerate and phosphoenolpyruvate to pyruvate). Two molecules of
N
A
D
H
2
are formed at the time of oxidation of glyceraldehyde 3-phosphate to 1, 3-biphosphoglycerate. The net reaction of glycolysis is as follows:
G
l
u
c
o
s
e
+
2
N
A
D
+
+
2
A
D
P
+
2
H
3
P
O
4
→
2
P
y
r
u
v
a
t
e
+
2
N
A
D
H
+
2
H
+
+
2
A
T
P
Each NADH is equivalent to 3 ATP, so the net gain in glycolysis is 8 ATP.
So the correct answer is '
2
p
y
r
u
v
i
c
a
c
i
d
+
2
A
T
P
+
2
N
A
D
H
2
'.
Which of the following steps during glycolysis is associated with utilization of ATP?
Report Question
0%
Glucose
→
Glucose-6-phosphate
0%
Fructose-6-phosphate
→
Fructose-1,6-bisphosphate
0%
PEP
→
Pyruvic acid
0%
Both (a) and (b)
Explanation
In the initial phase (energy spending phase) of glycolysis, the hexoses (i.e glucose and fructose) are phosphorylated in a reaction that uses ATP at two steps: First in the conversion of glucose into glucose-6-phosphate and second in the conversion of fructose-6-phosphate to fructose-1, 6-biphosphate.
These reactions are catalysed by the hexokinase and phospho-fructokinase respectively.
G
l
u
c
o
s
e
+
A
T
P
h
e
x
o
k
i
n
a
s
e
→
M
g
2
+
G
l
u
c
o
s
e
−
6
−
p
h
o
s
p
h
a
t
e
+
A
D
P
F
r
u
c
t
o
s
e
−
6
−
p
h
o
s
p
h
a
t
e
+
A
T
P
P
h
o
s
p
h
o
−
f
r
u
c
t
o
k
i
n
a
s
e
→
M
g
2
+
F
r
u
c
t
o
s
e
−
1
,
6
−
b
i
p
h
o
s
p
h
a
t
e
+
A
D
P
.
So the correct answer is 'Both (a) and (b)'.
At the end of glycolysis, X is the net energy gain from one molecule of glucose via Y, but there is also energy stored in the form of Z. identify X, Y, and Z.
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0%
X- 1 ATP ; Y-Oxidative phosphorylation ; Z - NADH+
H
+
0%
X- 2 ATP ; Y-Oxidative phosphorylation ; Z - NADH+
H
+
0%
X- 1ATP ; Y-Substrate level phosphorylation ; Z -
F
A
D
H
2
0%
X- 2ATP ; Y-Substrate level phosphorylation ; Z - NADH+
H
+
Explanation
In Glycolysis the net energy gain from one molecule of glucose by phosphorylation of different substrate (i.e., Substrate level phosphorylation) produced 2 ATP. In between this process,
2
N
A
D
+
gets reduced and stored as an energy source to use later.
Thus, X- 2ATP, Y- Substrate level phosphorylation, Z-
N
A
D
H
+
H
+
.
So, the correct option is (D).
A test tube containing molasses solution and yeast is kept in a warm place overnight. The gas collected from this mixture
Report Question
0%
Extinguishes the flame
0%
Bursts into flame when ignited
0%
Turns lime water milky
0%
Both (a) and (c)
Explanation
Yeast do anaerobic fermentation by consuming sugar and forming ethanol and
C
O
2
. As
Molasses mainly contain sugar, yeast will do anaerobic fermentation of the molasses and forms
C
O
2
gas as a by-product.
This
C
O
2
gas can (i) extinguishes the flame, and (ii) Turns lime water milky.
So, the correct answer is (D).
Ethyl alcohol fermentation occurs in _______________.
Report Question
0%
Lactobacillus
0%
Muscles of Humans
0%
Rhizopus
0%
All of these
Explanation
Ethyl alcohol fermentation occurs in fungi such as Rhizopus, yeast, and bacteria.
Lactobacillus and muscles of humans do anaerobic respiration but form lactic acid as an end product. (i.e., Lactic acid fermentation)
So, the correct answer is (C).
Select the correct option:
What does A,B and C depict in the given pathways of anaerobic respiration?
Report Question
0%
A-
N
A
D
H
+
H
+
→
N
A
D
+
; B-
N
A
D
+
→
N
A
D
H
+
H
+
; C-
N
A
D
+
→
N
A
D
H
+
H
+
0%
A-
N
A
D
H
+
H
+
→
N
A
D
+
; B-
N
A
D
H
+
H
+
→
N
A
D
+
; C-
N
A
D
+
→
N
A
D
H
+
H
+
0%
A-
N
A
D
+
→
N
A
D
H
+
H
+
; B-
N
A
D
H
+
H
+
→
N
A
D
+
; C-
N
A
D
H
+
H
+
→
N
A
D
+
0%
A-
N
A
D
+
→
+
H
+
; B-
N
A
D
H
+
H
+
→
N
A
D
+
; C-
N
A
D
+
→
N
A
D
H
+
H
+
Explanation
In glycolysis, NAD+ oxidises glyceraldehyde-3-phosphate by acting as a reducing agent and convert it to 3-phosphoglyceric acid.
(
N
A
D
+
+
H
+
→
N
A
D
H
)
In the absence of oxygen Pyruvic acid to either Lactic acid or ethanol depending on the organism.
1. In Lactic acid fermentation - pyruvic acid converts into Lactate while regenerating the
N
A
D
+
.
(
N
A
D
H
→
N
A
D
+
+
H
+
)
2. In Alcoholic fermentation - pyruvic acid converts into ethanol while regenerating the
N
A
D
+
.
(
N
A
D
H
→
N
A
D
+
+
H
+
)
So, the correct answer is (C).
Which of these steps in krebs' cycle indicates substrate level phosphorylation?
Report Question
0%
Conversion of succunic acid to a-ketoglutaric acid
0%
Conversion of succunic acid to malic acid
0%
Conversion of succunyl CoA to succunic acid
0%
Conversion of malic acid to oxaloacetic acid
Explanation
Succinate thiokinase catalyzes the conversion of succinyl CoA to succinic acid. During this step, CoA is released and one molecule of GTP is formed from GDP. This is a substrate level phosphorylation.
Thus, the correct answer is 'Conversion of succinyl CoA to succinic acid.'
During alcoholic fermentation by yeast two molecules of glucose produce.
Report Question
0%
2
molecules of ethanol
+
2
molecules of
C
O
2
0%
4
molecules of ethanol
+
4
molecules of
C
O
2
0%
6
molecules of ethanol
+
6
molecules of
C
O
2
0%
3
molecules of ethanol
+
3
molecules of
C
O
2
Explanation
Alcoholic fermentation is a process of anaerobic respiration in which 2 molecule of glucose is converted to -
4 molecules of ethanol,
4 molecules of carbon dioxide,and
4 ATP.
So, the correct option is '4 molecules of ethanol + 4 molecules of CO
2
'.
Value of R.Q. in succulents is ____________.
Report Question
0%
Unity
0%
Infinite
0%
Less than unity
0%
Zero
Explanation
Succulents do not evolve carbon dioxide during the night (when their stomata are open) as the same is in carbon fixation. They also change carbohydrates to organic acids which utilise oxygen but do not evolve carbon dioxide.
2
C
6
H
12
O
6
+
3
O
2
⟶
3
C
4
H
6
O
5
M
a
l
i
c
a
c
i
d
+
3
H
2
O
R
.
Q
.
=
Z
e
r
o
C
O
2
3
O
2
=
Z
e
r
o
So the correct option is D.
The net gain of ATP molecules in glycolysis during aerobic respiration is
Report Question
0%
0
0%
2
0%
4
0%
8
Explanation
Correct Option: D
Explanation:
The initial cycle of aerobic respiration is glucose.
At the final stage of the cycle, it generates two
pyruvate
molecules, which is a net gain of two ATP molecules, and two NADH 2 molecules.
Each formation of 1, 3-biphosphoglyceric acid to 3-
phosphoglyceric
acid and that of 2-phosphoenol
pyruvic
acid to pyruvic acid produces two molecules of ATP.
However, two of these four molecules of ATP are used during the conversion of glucose to glucose-6-
phosphate
and fructose-6-phosphate to fructose-1,6-diphosphate.
Two molecules of NADH 2 are produced during the conversion of two molecules of 1, 3-
diphosphoglyceraldehyde
into two molecules of 1, 3-diphosphoglyceric acid.
During aerobic respiration, each NADH 2 produces three ATP and one water molecule.
Hence, in the process of glycolysis, the net gain of ATP molecules is 8 during aerobic respiration.
Select the correct option:
Identify X,Y and Z in the given diagram of Citric acid cycle and select the correct option.
Report Question
0%
X-GTP; Y-
N
A
D
H
2
;Z-
F
A
D
H
2
0%
X-
F
A
D
H
2
; Y-
N
A
D
H
2
; Z-GTP
0%
X-
N
A
D
H
2
; Y-
F
A
D
H
2
; Z- GTP
0%
X-
C
O
2
; Y-
N
A
D
H
2
; Z-
A
D
P
Explanation
In Kreb’s cycle, during the conversion of alpha-ketoglutaric acid to succinyl CoA involves the release of a molecule of NADH
2
, the conversion of succinyl CoA to succinate involves the release of one molecule of GTP, and the conversion of succinic acid to fumaric acid involves the release of a molecule of FADH
2
.
So, the correct answer is
X-
N
A
D
H
2
; Y-
F
A
D
H
2
; Z- GTP
Select the correct option:Fermentation is represented by the equation
Report Question
0%
C
6
H
12
O
6
+
6
O
2
→
6
C
O
2
+
6
H
2
O
+
686
K
c
a
l
0%
C
6
H
12
O
6
→
2
C
2
H
5
O
H
+
2
C
O
2
+
59
K
c
a
l
0%
6
C
O
2
+
12
H
2
O
L
i
g
h
t
→
C
h
l
o
r
o
p
h
y
l
l
C
6
H
12
O
6
+
6
H
2
O
+
6
O
2
0%
6
C
O
2
+
6
H
2
O
→
C
6
H
12
O
6
+
6
O
2
Explanation
Fermentation can be described as an enzyme-catalyzed process in which one substrate is usually broken down by the enzymes produced by bacteria, yeast, and other microorganisms. Fermentation of glucose results in the formation of ethanol and carbon monoxide. This is an exothermic reaction and results in the release of energy.
Thus, the correct answer is ' C
$$_
6$$
H$$_{
12)$$
O$$_
6$$
→
2
C$$_
2$$
H$$_
5$$
O
H
+
2
C
O$$_
2$$
+
59
K
c
a
l
.'
Read the given statements and select the correct option.
Statement 1: Glycolysis occurs in mitochondrial matrix.
Statement 2: Kerbs' cycle occurs on cristae of mitochondria.
Report Question
0%
Both statements 1 and 2 are correct
0%
Statement 1 is correct but statement 2 incorrect.
0%
Statement 1 is incorrect but statement 2 correct.
0%
Both statements 1 and 2 are incorrect
Explanation
Glycolysis is the process of conversion of glucose to pyruvate. It occurs in the cytoplasmic matrix.
Krebs' cycle occurs in the mitochondrial matrix and generates a pool of chemical energy (ATP, NADH, and FADH2) from the oxidation of pyruvate, the end product of glycolysis.
Therefore, both statements are incorrect.
So, the correct options are (D).
Acetyl CoA is produced from pyruvate by
Report Question
0%
oxidative decarboxylation
0%
oxidative photophosphorylation
0%
oxidative hydrogenation
0%
oxidative photorespiration.
Explanation
Acetyl CoA is produced from pyruvate by the process of oxidative decarboxylation in the presence of an enzyme called the pyruvate dehydrogenase complex (PDC). The by-products of this reaction are carbon dioxide and NADH.
Thus, the correct answer is 'oxidative decarboxylation.'
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Practice Class 11 Medical Biology Quiz Questions and Answers
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