NYJC Prelim P2

8/16/2019 NYJC Prelim P2

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Question 4 NYJC Prelim P2/Q1/2009

The diagram shows the tertiary structure of a molecule of the enzyme RNase.

Fig. 4.1

(a) Name the chemical group found in position A.

Amino group (-NH2) ! amine group

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(b) %&plain what is meant 'y the tertiary structure of a protein.

Refers to oerall specific uni*ue precise three-dimensional structure conformation as a

result of folding of secondary structures i.e. α helices and β pleated sheets

Held together 'y hydrogen 'onds+ ionic 'onds+ disulfide 'onds andor hydropho'icinteractions 'etween R-groups side chains

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Question 4: AQA/Jan05/ BYB7/Q3

,apain is an enzyme used to 'rea down protein in industrial processes. n many of these

processes papain is immo'ilized.

a) /escri'e one way in which an enzyme can 'e immo'ilized.

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b) The graph shows the effect of temperature on the actiity of papain in solution and

immo'ilized papain.

i. /escri'e the differences 'etween the actiity of papain in solution and

immo'ilized papain.


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ii. %&plain the effect of temperature on the actiity of papain in solution.

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iii. 1sing information from the graph+ suggest one adantage of using papain in

industrial processes rather than using proteases o'tained from a mammalian

digestie system.

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[Total: 7


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HCI Prelim 2011 / P2 / Q1Metabolic pathways can be controlled by end-product inhibition of enzyme-catalysed reactions.KAS III is the initial enzyme of fatty acid production in bacteria. The substrate for this reaction ismalonyl-ACP.

Three different mutant strains of bacteria were enerated! each with a different mutated KAS III ene" M1! M2 and M3. The enzyme acti#ity of the wild-type and the three mutant strains wastested with and without the addition of a KAS III inhibitor! dodecanoyl-ACP. $odecanoyl-ACP isstructurally similar to malonyl-ACP. Fig. 5.3 shows the mean acti#ity of KAS III in the wild-type!M1! M2 and M3 strains.

Fig. 5.3

(b) %ith reference to Fig. 5.3! e&pla in why the acti#ity of KAS III in the wild-type strainchanes when dodecanoyl-ACP is added.

$odecanoyl-ACP e&hibits competiti#e inhibition by bindin to the acti#e siteand pre#entin enzyme-substrate comple& formation'

hence lowerin the rate of enzymatic reaction as some enzymes become inhibited from(.) *mol min-+ m-+ to +., *mol min-+ m-+'

Key" without inhibitor with inhibitor

%ild-type M1 M2 M3

+

)

/

,

(

0

1acterial strain

i n -

1 m

-

1


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(c) Suest an e&planation for the effect of mutation on KAS III acti#ity.

The /$ conformation of acti#e site is altered in mutated KAS III such that it is no loner complementary to the substrate 5in terms of size! shape! chare! orientation6'pre#entin bindin to acti#e site to form enzyme-substrate comple& resultin in a

reduction in KAS III acti#ity' The acti#e site is also no loner complementary to the /$ conformation of dodedecanoyl-ACP'

Thus it cannot bind to the acti#e site of mutated KAS! mutated KAS III is not inhibited bydodedecanoyl-ACP'

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Quesi!" 3# YJC Prelim 0$

The se7uence of a portion of a pro8aryotic ene is shown below.

(%) If transcription beins at position + and proceeds to the riht! what would be these7uence and orientation of the resultin m9:A;

3+4

(b)


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(c) $efine silent mutation and describe an e&ample of a silent mutation that may occur inthe i#en pro8aryotic ene.

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(&) Antibiotics ha#e been #ery useful in elucidatin the steps of protein synthesis. Arecently disco#ered antibiotic by the name of smilimycin bloc8s a particular step in

protein synthesis such that an m9:A with the se7uence! A>?->CC->AC->AC-??A! istranslated to @ust a simple amino acid! Met! instead of the normal polypeptide! Met-Ser-Tyr-Tyr-?ly. %hich step in protein synthesis does smilimycin affect and why;

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1 Fig. 5 shows mo#ements that ta8e place within a cell durin mitosis. The three cur#es showchanes in distance between"

+ the centromere and the poles of the spindle.

, the centromeres of sister chromatids.

C the poles of the spindle.

n the time scale! mar8s the time when chromosomes line up the e7uator.

Fig. 5

(%) %ith reference to Fig. 5!

(i) identify the two main staes of mitosis when these mo#ements occur.

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(ii) describe what happens to the chromatids after +( minutes.

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(iii) account for the chanes in cur#e C.

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(b) utline the role of centromeres.

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(c) Suest the sinificance of mitosis in humans.

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'!%l# 10*

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