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Chapter 2 Biological Molecules Biology 11th Class Punjab Short Questions

Question No. 1 - What is the role of pH on enzyme activity?

Answer No. 1 - A slight change in pH can change the ionization of the amino acid at the active site. Moreover it may effect the ionization of the substrate.Under these changed condition enzyme activity is either retarded blocked completely.

Question No. 2 - Define inhibitors with example.

Answer No. 2 - An inhibitors is an chemical substance that can react with the enzyme but is not transferred in to product and thus block the active site temporarily or permanently. For Example: poisons like cyanide, antibodies, anti metabolites, some drugs and pesticides etc.

Question No. 3 - Define active site of enzyme and write only names of its two regions.

Answer No. 3 - An enzyme and its substrate react with each other through definite charge bearing site called active site. The active site of an enzyme is a three dimensional cavity bearing a specific charge by which the enzyme reacts with its substrate.
Active sites have two regions:
1. Binding Site
2. Catalytic site

Question No. 4 - What is induced fit model of enzyme action?

Answer No. 4 - On the basic of new evidences, Koshland proposed modified form of lock and key model. This is known as induced fit model. He argued when a substance combines with an enzyme. It induced changes in the structure enables the enzyme to perform its catalytic activity more efficiently. This shows that enzymes are not rigid and flexible but are capable of considerable internal movement.

Question No. 5 - Define optimum temperature, Give optimum temperature of human.

Answer No. 5 - All enzymes can work at their maximum rate at a specific temperature called as optimum temperature, For enzymes of human body 37 Degree is the optimum temperature.

Question No. 6 - Write four characteristics of enzyme.

Answer No. 6 - 1. All enzymes are globular proteins.
2. They increase the rate of reaction without themselves
being used up.
3. Their presence does not affect the nature of properties
of end products.
4. Even a small amount of enzymes can bring about the
change in large amount of the substrate.

Question No. 7 - What is enzyme to enzyme chain?

Answer No. 7 - In certain cases enzyme act in series of chemical reaction in a particular order to complete the metabolic pathway such as respiration or photosynthesis. The successive enzyme containing these reactions are normally present together in a precise order of reaction such that substrate molecule can be literally handed on form one enzyme to another forming a enzyme, coenzyme chain.

Question No. 8 - What is NAD?

Answer No. 8 - NAD stands for Nicotinamide Adenine Dinucleotide. It is and important enzyme.

Question No. 9 - In what way, substrate concentration affects the rate of reaction?

Answer No. 9 - 1. At low substrate concentration is kept constant and the amount of substance is increased, a point is reached when a further in the substrate does not increased the rate of reaction any more. This is because at high substrate level all the active sites of enzyme are saturated with substrate,After this the rate of enzyme reaction becomes steady and addition of substrate will not have the positive effect.

Question No. 10 - How does high temperature effect enzyme activity?

Answer No. 10 - The rate of enzyme controlled reaction may increase with increase in temperature but up to a certain limit. All enzymes can work at their maximum rate at a specific temperature called optimum temperature.
Heat provide activation energy and therefore chemical reaction are accelerated at high temperature.

Question No. 11 - Discuss lock and key model of enzyme action.

Answer No. 11 - Emil Fischer in 1890 proposed lock and key model to visualize enzyme substrate interaction. According ti this model as only a specific key fits in a particular lock to open it. Similarly a specific enzyme can transform only one substrate in product.
According to lock and key model the active site is a rigid site is rigid structure. There is no key modification or flexibility in the active site before, during and after the enzyme action and it is used only as a template.

Question No. 12 - Why enzymes are denatured at high temperature?

Answer No. 12 - At high temperature heat provides activation energy and therefore, chemical reaction are accelerated at high temperature. Heat also supplies kinetic energy to the reacting molecules causing them to move rapidly. Thus the reactant move rapidly and chance of their collision with each other also increased.

Question No. 13 - What is co-factor? Give its role.

Answer No. 13 - Some enzymes consists of solely of proteins. Other have a non proteins part known as co-factor. Which is essential for the proper functional of the enzymes. The co-factor usually acts as a bridge between the enzymes and its substrate, often it contributes directly to the chemical reaction which bring about catalysis.

Question No. 14 - Define apoenzyme and cofactor.

Answer No. 14 - Apoenzyme: The proteins of enzyme is called apoenzyme or enzyme without non protein part is called apoenzyme.

Question No. 15 - How enzyme catalyze series of chemical reaction?

Answer No. 15 - In certain cases enzymes act in a series of chemical reactions in a particular order to complete metabolic pathway such as respiration or photosynthesis. The successive enzymes containing these reactions are normally present together in a precise order of reaction.

Question No. 16 - Differentiate between enzyme and co enzyme?

Answer No. 16 - Enzyme: Enzyme are called biological catalyst they tremendously increase the rate of reaction, decrease the energy of activation and the are produced by the living organisms.

Question No. 17 - Give the role of pH in enzyme action. Give the optimum pH values for any two enzyme actions.

Answer No. 17 - Optimum pH for pepsin is 2.00 and for sucrose is 5.50.

Question No. 18 - At high substrate level, rate of enzyme action is not increased. Give reason.

Answer No. 18 - If the enzyme concentration is kept constant and the amount of substrate is increased a point is reached when further increase in the substrate s does not increase the rate of reaction any more, This is because at high substrate level all the active sites of enzyme are saturated with example.

Question No. 19 - What are co-factor? Give its types.

Answer No. 19 - Co-factors is a non proteins part of enzymes, which is essential for the proper functioning of the enzymes. Some enzymes consist of solely of proteins. Other have a non-proteins part known as co-factor. Types of co-factors are activators, prosthetic group and co-enzymes.

Question No. 20 - Differentiate between co-factor and activator?

Answer No. 20 - Co-factor: Some enzymes consists of solely of proteins. Other have a non proteins part known as co-factor. Which is essential for the proper functional of the enzymes. The co-factor usually acts as a bridge between the enzymes and its substrate,often it contributes directly to the chemical reaction which bring about catalysis.

Question No. 21 - Distinguish between prosthetic group and Co-enzyme.

Answer No. 21 - Prosthetic Group: If the non proteins parts are covalent bonded it is known as prosthetic group.

Question No. 22 - What are enzymes? Give their importance?

Answer No. 22 - Enzymes are called biological catalyst the tremendously increase the rate of reaction, decrease the energy of activation and they are produced by the living organisms.
Importance: Enzyme control and catalyst chemical reaction in the living bodies or cell.Without enzymes reaction are not possible ultimately making life impossible.

Question No. 23 - Differentiate between reversible and irreversible inhibitors.

Answer No. 23 - Reversible inhibitors: They form weak linkages with the enzyme. Their effect can be neutralized completely or partly by an increase on the concentration of the substrate.

Question No. 24 - Give difference between prosthetic group and activator.

Answer No. 24 - Prosthetic Group: Covalently bounded non protein part is called prosthetic group.
Activator: DNA-binding transcription metabolite that positively modulates an allosteric Enzyme or regulates one or more genes by increasing the rate of transcription.

Question No. 25 - Differentiate between apoenzyme and holoenzyme.

Answer No. 25 - Apoenzyme: The proteins part of enzyme is called apoenzyme or enzyme without non protein part is called apoenzyme.
Holoenzyme: Holoenzymes are the active forms of enzymes. Enzymes that require a cofactor but are not bound by one are called apoenzymes.

Question No. 26 - What is role of enzyme concentration on the rate of enzyme action?

Answer No. 26 - The rate of reaction depends upon directly on the amount of enzyme present at a specific time at unlimited substrate concentration. If the amount of enzyme is increased by two fold the reaction is doubled.

Question No. 27 - Give function of binding site and catalytic site of the active site of an enzyme.

Answer No. 27 - The binding sites helps the enzymes in the recognition and binding of a proper substrate to produce and ES complex. This reaction activities the catalytic site. Activated catalytic site catalyzes the transformation of the substrate into products.

Question No. 28 - What is an activator?

Answer No. 28 - Some enzymes use metal ions as co factor like Mg2+etc. The detachable co-factor is known as activator if it is an inorganic ions like.

Question No. 29 - Give the optimum pH values of enzyme pepsin and pancreatic lipase.

Answer No. 29 - Optimum pH for pepsin is 2.00 and that for pancreatic lipase is 9.00.

Question No. 30 - Who proposed induced fit model of enzyme action?

Answer No. 30 - Koshland's proposed induced fit model.

Question No. 31 - Define optimum pH.

Answer No. 31 - Every enzyme function most efficiently over a narrow range of pH known as the optimum pH.

Question No. 32 - How extreme change in pH affect enzyme?

Answer No. 32 - A slight change in pH can change the ionization of the amino acids at the active site. Moreover it may affect the ionization of the substrates.Under these change condition enzyme activity is either retarded blocked completely. Extreme change in pH cause the bonds in the enzymes to break, resulting in the enzyme denaturation.

Question No. 33 - What is active site of an enzyme?

Answer No. 33 - An enzyme and its substrate react with each other through definite charge bearing site called active site. The active site of an enzyme is a three dimensional cavity bearing a specific charge by which the enzyme reacts with its substrate.

Question No. 34 - Compare competitive and non competitive inhibitors.

Answer No. 34 - Competitive Inhibitors: Such inhibitors have structural similarity with the substrate both of which compete for same active sites of the enzyme. Because of the structural similarity with the substrate they may be selected by the binding sites.

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