Biology

Cellular Respiration and Enzymes

1,721 Questions

Explore key concepts of cellular respiration, including glycolysis, the Krebs cycle, and the electron transport chain. These questions also cover ATP production, anaerobic respiration, and essential metabolic pathways. This topic forms a core part of the biology syllabus for many competitive examinations.

Glycolysis and metabolic pathwaysKrebs cycle processesElectron transport chainATP production countAnaerobic respiration products

Cellular Respiration and Enzymes Questions

Multiple choice bio-chemistry cell biology cytoplasm the components in a cell component of the cell

Movement of .......... in cytoplasm is considered as a signalling activity for metabolic processes.

  1. Calcium ions

  2. Proteins

  3. Sodium ions

  4. Potassium ions
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Movement of calcium ions in and out of the cytoplasm is thought to be a signalling activity for metabolic processes. In plants, movements of the cytoplasm around vacuoles are known as cytoplasmic streaming. 

Multiple choice biology reproduction in living organisms regeneration asexual modes of reproduction reproduction in animals

During constructive metabolism or regeneration

  1. pH becomes normal

  2. R.Q. increases

  3. Lactic acid decreases

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The process of storing energy in order for the body to maintain itself and grow is referred to as constructive metabolism or anabolism.
Anabolism is the synthesis process which requires energy (ATP). To gain energy, the cell undergoes glycolysis. As a result of glycolysis, there is decrease in the production of lactic acid and also RQ increases. RQ is the respiratory quotient which is calculated as:
RQ = (Volume of carbon dioxide released/ Volume of oxygen consumed)/ per unit time.
Thus, the correct answer is option D.

Multiple choice evs respiration in organism human respiration the mechanism of breathing breathing and its movements
Select the wrong statement

  1. Oxidative decarboxylation of pyruvic acid requires the presence of enzyme pyruvate dehydrogenase.

  2. All living cells whether aerobic or anaerobic, perform glycolysis.

  3. Cyanide does not stop chemiosmosis.
  4. Respiratory chain uses ${O} _{2}$ as final hydrogen acceptor.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Cyanide is an inhibitor of complex IV (in ETS) and other heme-containing enzymes of mitochondria. Thus, cyanide blocks ATP production in the cells.

Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

Combination of apoenzyme and coenzyme produces

  1. Prosthetic group

  2. Holoenzymes

  3. Enzyme-substrate complex

  4. Enzyme-product complex
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Enzymes are proteins which help to catalyze the biochemical reaction. The enzyme has a protein part which is not active is known as apoenzyme. It gets activated by the addition of an organic or inorganic cofactor. The holoenzyme is defined as apoenzyme in combination with the cofactor. 
So, the correct answer is option B.
Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

An enzyme acts by

  1. Reducing the energy of activation.

  2. Increasing the energy of activation.

  3. Decreasing the pH.

  4. Increasing the pH.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The reactants do not undergo chemical change automatically. They do so in transition state. Transition state has more free energy than reactants or products. The inability of reactants to undergo change due to requirement of extra energy for converting them to transition state is called as 'Energy Barrier'. Energy required to overcome energy barrier is called as 'Activation Energy'.

Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

The enzymes are functional at 

  1. 0-5$^{\circ}$C
  2. 15-25$^{\circ}$C
  3. 25-40$^{\circ}$C
  4. 70-85$^{\circ}$C
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Enzymes works precisely at certain narrowly optimum conditions, such as appropriate temperature, pH, and ion concentration. Deviation from the optimal conditions adversely affects enzyme activity.  Most enzymes have an optimal temperature, at which the rate of reaction is fastest. For human enzymes, the temperature optima are near the human body temperature (35-40$^o$C). Enzymatic reactions occur slowly or not at all at low temperatures. As the temperature increases, molecular motion increases, resulting in more molecular collisions. The rates of most enzyme-controlled reactions, therefore, increase as the temperature increases, within limits. High temperatures rapidly denature most enzymes. The molecular conformation (3-D shape) of the protein becomes altered as the hydrogen bonds responsible for its secondary, tertiary, and quaternary structures are broken. Because this inactivation is usually not reversible, activity is not regained when the enzyme is cooled.

Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

Which of the following is the transition state structure of the substrate formed during an enzymatic reaction?

  1. Permanent but unstable

  2. Transient and unstable

  3. Permanent and stable

  4. Transient but stable
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Reactions do not undergo chemical changes automatically. They do so in transition states. Transition state has more free energy than reactants or products. Higher free energy helps in collision of transition state reactants. The enzymes binds to substrate molecules and form an unstable transient state called as transition state. The transition state rapidly undergoes degeneration into products and unchanged enzyme molecule.

Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

Which of the following is iron porphyrin coenzyme or cofactor?

  1. Cytochrome

  2. FAD

  3. CoA

  4. NAD
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Hemes are the iron containing porphyrins. They are extensively found in nature. These are also present in proteins like haemoglobin and myoglobin. Cytochromes are also a haemoproteins. Cytochrome also act as an integral part of membrane protein.

Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

Enzymes which transfer electrons are

  1. Hydrolyses

  2. Hydrogenases

  3. Proteases

  4. Transaminases
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Enzymes which helps in the transfer of electrons are known as hydrogenases. It catalyzes the reversible oxidation of hydrogen to protons by the loss of electrons. The electron acceptors like oxygen are reduced in this particular reaction while electron donors like ferredoxin are oxidized.
Hydrolyses are the enzyme which catalyzes the splitting of compounds by addition of water.
Proteases hydrolyze the peptide bond.
Transaminase catalyzes aminotransferase reaction between an amino acid and a α-keto acid.
So, the correct answer is option B.
Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

Select the correct option: 

Enzymes catalyze the biochemical reactions by .......... the activation energy.

  1. lowering

  2. increasing

  3. unaltering

  4. either (a) or (b)
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Enzymes are macromolecular biological catalysts. which accelerates chemical reactions. Catalysts lower the activation energy (energy required to start a reaction.) for reactions. The lower the activation energy for a reaction, the faster the rate.

So, the correct answer is 'lowering'.

Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology
Enzymes that catalyse removal of groups from substrates by mechanisms other than hydrolysis, and addition of groups to double bonds, are called

  1. Ligase

  2. Lyase

  3. Hydrolase

  4. Dehydrogenase
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Lyases enzymes catalyse the breakage of specific covalent bonds and removal of group with out hydrolysis producing double bonds or removal of double bonds by adding group,e.g., histidine decarboxylase that splits $C-C$ bond of histidine,forming $CO _2$ and histamine.

${\overset{X}{\overset{|}C}}-{\overset{Y}{\overset{|}C}} \xrightarrow{lyase}X-Y+C=C$

Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

With reference to enzymes, which one of the following statements is true?

  1. Apoenzyme = Holoenzyme+ Coenzyme

  2. Holoenzyme= Apoenzyme + Coenzyme

  3. Coenzyme= Apoenzyme + Holoenzyme

  4. Holoenzyme= Coenzyme+ Apoenzyme
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Enzymes work efficiently in association with various factors which enhances it's activity. These factors may be;

Coenzymes are organic molecules that are mostly derivatives of vitamins soluble in water by phosphorylation. Example of coenzyme include thiamine pyrophosphate (TPP), flavin adenine dinucleotide (FAD), biotin

Apoenzyme is an inactive form of enzyme lacking the association of coenzyme and/or cofactors. Activation of the enzyme occurs upon binding of an organic or inorganic cofactor.

Holoenzyme is a complete and catalytically active form of enzyme. An apoenzyme together with its cofactor is holoenzyme.  Examples of holoenzymes include DNA polymerase and RNA polymerase which contain multiple protein subunits.

So the correct option is 'Holoenzyme= Apoenzyme + Coenzyme'.
Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

Arrange the steps of catalytic action of an enzyme in order and select the correct option.
I.   The enzyme release the products of the reaction      and the enzyme is free  to bind to another                substrate.
II.  The active site of enzyme is in close proximity of      the substrate and breaks the chemical bonds of     the subtrate.
III. The binding of sustrate induces the enzyme to          alter its shape fitting more tightly around the           sustrate. 
IV.The substrate binds to the active site of the              enzyme.

  1. IV, III, II, I

  2. III, II, I, IV

  3. IV, II, I, III

  4. II, I, IV, III
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Four Steps of Enzyme Action:
1) The enzyme and the substrate are in the same area. Some situations have more than one substrate molecule that the enzyme will change.
2) The enzyme grabs on to the substrate at a special area called the active site. A process called catalysis.
3) The binding of substrate induces the enzymes to alter its shape to fit around the substrate. 
4) The enzyme breaks the chemical bonds of the substrate and releases the product of the reaction and the enzyme is free to bind to another substrate.

So, the correct option is 'IV, III, II, I'.

Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

In biochemical reactions, the enzymes act by

  1. By decreasing the energy of the reactants

  2. By increasing the activation energy of the reaction

  3. By decreasing the activation energy of the reaction

  4. By increasing the energy of the products of the reaction

  5. By decreasing the energy of the products of the reaction
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The minimum energy requirement that must be met for a chemical reaction to occur is called the activation energy. The activation energy is the energy difference between the reactants and the activated complex, also known as transition state. In a chemical reaction, the transition state is defined as the highest-energy state of the system. If the molecules in the reactants collide with enough kinetic energy and this energy is higher than the transition state energy, then the reaction occurs and products form. In other words, the higher the activation energy, the harder it is for a reaction to occur and vice versa. However, if a catalyst is added to the reaction, the activation energy is lowered because a lower-energy transition state is formed. Enzymes can be thought of as biological catalysts that lower activation energy. Enzymes are proteins or RNA molecules that provide alternate reaction pathways with lower activation energies than the original pathways. Enzymes affect the rate of the reaction in both the forward and reverse directions; the reaction proceeds faster because less energy is required for molecules to react when they collide. Thus, the rate constant (k) increases.
So, the correct answer is option C.