C1.1 Enzymes and Metabolism

Question 1

Define catalyst.

Answer 1

Substance that increases the rate of a chemical reaction

Question 2

State that enzymes speed up chemical reactions without being altered, so can be reused.

Answer 2

Enzymes speed up chemical reactions without being altered, so can be reused

Question 2

State the role of enzymes in the chemical reactions on which life is based.

Answer 2

Enzymes are catalysts for chemical reactions

Question 3

Define metabolism.

Answer 3

The complex network of interdependent and interacting in enzyme-catalyzed chemical reactions occuring in living organisms

Question 4

Define specificity in relation to enzyme structure and function.

Answer 4

Each enzyme is specific and catalyzes a specific metabolic reaction

Question 5

Outline how control of metabolism is regulated by enzymes.

Answer 5

The cell controls metabolism through the use of enzymes

Question 6

List three examples of anabolic processes.

Answer 6

Protein synthesis, glycogen formation, and photosynthesis

Question 7

Contrast anabolic and catabolic reactions.

Answer 7

Anabolic reactions is the synthesis of complex molecules from simpler molecules

Catabolic reactions is the breakdown of complex molecules into simpler molecules

Question 8

List three examples of catabolic processes.

Answer 8

Digestion, Oxidation, Hydrolysis

Question 9

Outline properties of globular proteins.

Answer 9

Quaternary structure
Hydrophilic surface, hydrophobic core

Question 10

Explain the relationship between enzyme structure and enzyme specificity, including the structure and function of the active site.

Answer 10

Enzyme structure determines specificity. Active site’s unique structure binds substrate, facilitating catalysis

Question 10

Outline the stages of enzyme catalysis of a chemical reaction.

Answer 10

Substrate approaches and enters active site of enzyme

Substrate induces the active site of the enzyme to change shape so that it is an optimal fit between substrate and active site

Enzyme-substrate complex is formed

Catalysis occurs as the active site provides optimum conditions for conversion of substrate to product

Product has different chemical properties than substrate and is released from the active site

Question 11

Describe the induced fit model of enzyme binding.

Answer 11

Explains how substrates are converted to products by enzymes

Question 12

Explain the role of random collisions in the binding of the substrate with the enzyme active site.

Answer 12

The more random collisions allow for a faster rate of enzymatic activity

Question 13

Compare enzyme and substrate movement involved in reactions that occur in the cytoplasm, with large substrates and with immobilized enzymes.

Answer 13

Localized reactions that are limited and have diffusive movement.

Question 14

Discuss variation in specificity of different enzymes.

Answer 14

Enzymes vary in specificity due to active site structure and evolution

Question 15

Define denaturation.

Answer 15

A permanent change in shape of proteins

Question 16

Explain the effects of temperature, pH and substrate concentration on enzyme structure and function with reference to collision theory, temporary and permanent denaturation.

Answer 16

Lower temperature lowers the rate of reaction, however the rate of reaction drops when past a certain temperature due to temporary then another increase results in permanent denaturation and no enzyme activity

Optimum pH for enzymes is 8, an increase or decrease lowers enzyme activity

Increase in substrate concentration results in increase in rate of reactions (collision theory) until all of the enzymes active sites are saturated(fully used)

Question 16

Outline the causes and effects of denaturation on enzyme structure and function.

Answer 16

The enzyme structure is permanently altered and loses it’s biological function

Question 17

State two methods for determining the rate of enzyme reaction rates.

Answer 17

Dividing the change in the amount of reactant or product by the time taken

Using a tangent to work out the reaction rate from a graph

Question 17

State the unit for enzyme reaction rate.

Answer 17

mol/s

Question 18

Describe three investigative techniques for measuring the activity of an example enzyme.

Answer 18

1. Colorimetric Assay: Detect enzyme activity through color change in reaction.
2. Oxygen Consumption Assay: Measure enzyme activity by monitoring the rate of oxygen consumption or production during the reaction.
3. pH Change Assay: Assess enzyme activity based on pH variations in reaction.

Question 19

Define activation energy.

Answer 19

Minimum energy required for a chemical reaction to occur

Question 20

State that activation energy is used to break or weaken bonds in the substrate.

Answer 20

Activation energy is used to break or weaken bonds of the substrate

Question 21

Explain the role of enzymes in lowering the activation energy of a reaction.

Answer 21

Enzymes lower the activation energy of chemical reactions

Question 22

Outline the generation of heat energy by the reactions of metabolism.

Answer 22

Metabolism isn’t 100% efficient and releases heat as a consequence

Question 22

State an example of an intracellular metabolic reaction and an extracellular metabolic reaction.

Answer 22

Krebs cycle of respiration. (intra)

Digestive system (extra)

Question 23

Compare the location of synthesis of enzymes used within and outside of a cell.

Answer 23

Intracellular enzymes : produced by mitochondrial or chloroplast enzymes

Extracellular enzymes : syntheszied by enzymes attached to the RER and sent to the Golgi APparatus before being excreted through the exocytosis of secretory vesicles

Question 24

Describe how birds and mammals maintain a body temperature greater than that of their environment.

Answer 24

Endothermic animals depend on the heat generated from metabolism to maintain a constant body temperature

Question 25

Outline an example of maintaining temperature homeostasis using heat generated by reactions of metabolism.

Answer 25

Polar bears maintain a constant temperature of 37C

Question 26

State the reason for metabolic pathways

Answer 26

Enable controlled and regulated biochemical reactions for cellular function and survival

Question 27

Contrast linear metabolic pathways with cyclical reaction pathways.

Answer 27

Sequential steps, unidirectional flow / recurring reactions, continous cycling of metabolites

Question 28

State and example of a linear metabolic pathway and a cyclic metabolic pathway.

Answer 28

Glycolysis linear

Krebs Cycle cyclic

Question 29

Outline the structure and function of an allosteric site.

Answer 29

Regulates enzyme or receptor by inducing conformational changes

Question 30

Define enzyme inhibitor.

Answer 30

Chemicals that bind to the enzyme to slow down it’s activity

Question 31

Describe mechanism of action of non-competitive enzyme inhibitors.

Answer 31

Bind to an allosteric site on the enzyme to change the shape of the active site preventing substrates from binding to it

Question 32

Describe mechanism of action of competitive enzyme inhibitors.

Answer 32

Chemicals that bind to the active site to slow down the activity of that enzyme

Question 33

Outline the function of statins as an example of a competitive inhibitor

Answer 33

A drug that lowers cholesterol levels in humans by reducing the amount of HMG-CoA that converts to mevalonic acid which is then converted to cholesterol through enzyme-catalyzed reactions.

Question 34

Explain why the rate of reaction with increasing substrate concentration is lower with a non-competitive inhibitor compared to a competitive inhibitor

Answer 34

Because an increase in substrate reduces inhibition for competitive inhibitors as it can no longer bind whereas non competitive inhibitors can still bind to the allosteric site

Question 35

Outline the mechanism and benefit of feedback inhibition.

Answer 35

End product inhibits an enzyme in a metabolic pathway thus preventing excessive accumulation of end products, maintaining balance.

Question 36

Illustrate end-product inhibition of the threonine to isoleucine metabolic pathway.

Answer 36

The AA threorine is converted to the Aa isoleucine which is a non competitive inhibitor of threonine, meaning it controls production of isoleucine.

Question 37

Compare reversible and irreversible enzyme inhibition.

Answer 37

Reversible : Temporary binding, inhibitor can dissociate.

Irreversible : Permanent inactivation, covalent binding

Question 38

Outline the cause and consequence of mechanism-based inhibition.

Answer 38

Competitve inhibitors that permanently bond to the active site resulting in substrates being permanently banned from entering the active site

Question 39

Illustrate mechanism-based inhibition using penicillin as an example.

Answer 39

Penicillin binds to transpeptidases which are involved in building cell walls for bacteria, these bacteria without cell walls will undergo lysis and die.