enzymology lec 5

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Questions and Answers

This enzyme is involved in the breakdown of hydrogen peroxide, a common byproduct of cellular metabolism that can be harmful to cells at high concentrations. It catalyzes the decomposition of hydrogen peroxide into water and oxygen, effectively reducing oxidative stress within the cell.

Based on this description, what would you name this enzyme?

Catalase

This enzyme speeds up the conversion of carbon dioxide and water into carbonic acid, an important reaction in maintaining pH balance in blood and other bodily fluids.

Carbonic anhydrase

match to the correct one

enzyme that removes phosphate groups from its substrate by hydrolyzing phosphoric acid monoesters into a phosphate ion and a molecule with a free hydroxyl group = Phosphatase This enzyme catalyzes the addition of a phosphate group to a molecule of ADP, using energy from the breakdown of glucose via oxidative phosphorylation. = ATP synthase This enzyme synthesizes DNA molecules from deoxyribonucleotides, the building blocks of DNA. It is essential for DNA replication. = DNA polymerase Essential for DNA replication, this enzyme unwinds the DNA helix at the replication fork to allow for the synthesis of a new DNA strand. = Helicase

Explain the purpose of the fourth digit in an Enzyme Commission (EC) number.

it is the enzyme serial number assigned by the Enzyme Commission. It helps to distinguish between different enzymes that catalyze the same reaction but have unique structural or functional properties. Signup and view all the answers

What information does the third digit of an EC number provide? Give an example to illustrate this.

The third digit is the sub-subclass, it provides furthur information about the type of reaction the enzyme is catalyzing Signup and view all the answers

Two different enzymes, one from a bacterium and one from a human, catalyze the exact same reaction. Would these enzymes have the same EC number or different EC numbers? Explain your reasoning.

These enzymes would have the same EC Number. EC numbers categorize reactions, not specific enzymes. Therefore, enzymes from different organisms that catalyze the same reaction would fall under the same EC number. Signup and view all the answers

Explain why knowing the EC number of an enzyme does not tell us the precise structure or biological function of the enzyme.

EC numbers classify the type of reaction catalyzed by an enzyme, not its structure or function. enzymes from different organisms can catalyze the same reaction and thus share an EC number. Signup and view all the answers

What can be deduced about two enzymes that share only the first two digits of their EC numbers?

they belong to the same class or catalyze the same type of reactions Signup and view all the answers

Match the following enzyme classes with their respective catalyzed reactions:

Oxidoreductases = Transfer of electrons (hydride ions or H atoms) Transferases = Group transfer Hydrolases = Hydrolysis (transfer of functional groups to water) Lyases = Cleavage of C—C, C—O, C—N, or other bonds by elimination, leaving double bonds or rings, or addition of groups to double bonds Signup and view all the answers

Match the following enzyme names with their respective class numbers:

Oxidoreductases = 1 Transferases = 2 Hydrolases = 3 Lyases = 4 Signup and view all the answers

Match the following descriptions with their respective enzyme class:

Transfer of groups within molecules to yield isomeric forms = isomerases Formation of C—C, C—S, C—O, and C—N bonds by condensation reactions coupled to cleavage of ATP or similar cofactor = Ligases Movement of molecules or ions across membranes or their separation within membranes = Translocases Hydrolysis (transfer of functional groups to water) = hydrolases Signup and view all the answers

Explain why cells need enzymes to carry out essential activities like growth, maintenance, and energy extraction.

Enzymes act as biological catalysts, accelerating chemical reactions within cells. This allows cells to perform essential processes efficiently and at a rate suitable for life. Without enzymes, these reactions would occur too slowly to sustain cellular functions. Signup and view all the answers

How do enzymes contribute to the efficiency of cellular processes?

Enzymes lower the activation energy required for reactions to occur, allowing them to proceed at much faster rates. This efficiency enables cells to carry out crucial processes like growth, repair, and energy production quickly and effectively. Signup and view all the answers

enzymes accelerate reactions by factors of up to 10^17 or more, true or false

true Signup and view all the answers

Explain the key characteristic of a catalyst, using the example of enzymes.

A catalyst, like an enzyme, speeds up a chemical reaction without being permanently altered or consumed in the process. Enzymes facilitate reactions by lowering activation energy, but they remain unchanged after the reaction is complete. Signup and view all the answers

enzymes are catalysts regardless of the modifications they may under go

True (A) Signup and view all the answers

how is rate enhancement or catalytic power calculated

catalyzed rate/uncatalyzed rate=kcat/kuncat Signup and view all the answers

as catalyzed rate increases catalytic power increases?

True (A) Signup and view all the answers

why is it better for the enzyme to be complementary to the transition state than the substrate itself?

Since the transition state has a higher free energy than the enzyme-substrate complex, it is energetically advantageous for the enzyme to be more complementary to the transition state. This complementarity helps lower the energy barrier for the reaction to proceed. By binding and stabilizing the transition state, the enzyme reduces the overall activation energy required, facilitating a faster and more efficient conversion of substrates into products. This stabilization is crucial because it enhances the reaction rate without the need for additional energy input Signup and view all the answers

Which of the following correctly describes absolute specific enzymes?

They utilize one substrate or a specific pair in one reaction. (A) Signup and view all the answers

Alcohol dehydrogenase is an example of an absolute specific enzyme.

False (B) Signup and view all the answers

What is the primary function of group specific enzymes?

they make use of a variety of substrates containing specific functional groups. Signup and view all the answers

The enzyme phenylalanine dehydrogenase converts L-phenylalanine into _______.

phenylpyruvate Signup and view all the answers

Match the following enzyme examples to their category:

Alcohol dehydrogenase = Group specific enzyme Phenylalanine dehydrogenase = Absolute specific enzyme Signup and view all the answers

define a group specific enzymes

an enzymes that acts on a variety of substrate containing a functional group that is modified Signup and view all the answers

define absolute specific enzymes

enzymes that makes use of one substrate in one reaction Signup and view all the answers

Flashcards

What does the first digit in an EC number indicate?

The first digit (a) in an EC number indicates the general class of reaction the enzyme catalyzes, like oxidation-reduction reactions or transfer reactions.

What does the second digit in an EC number indicate?

The second digit (b) in an EC number specifies the subclass of the reaction, providing a more specific description of the reaction catalyzed.

What does the third digit in an EC number indicate?

The third digit (c) in an EC number further clarifies the reaction by specifying the sub-subclass, offering a more precise determination of the catalyzed reaction.

What does the fourth digit in an EC number indicate?

The fourth digit (d) in an EC number is a unique serial number assigned to the specific enzyme-catalyzed reaction.