topic 6 rev

1.

Classification of viruses is based upon the structure of the virus and the type of nucleic acid it contains. (a) Describe how (lambda) phage is classified. ...................................................................................................................................... ......................................................................................................................................(2)

(b)

Some phage viruses were cultured with a suspension of bacteria. The culture was left for forty minutes, during which time one cell infection cycle took place. The number of viruses free in the culture fluid was determined at intervals of 2 minutes. The growth curve below shows the results.

(i)

Describe the events which are occurring inside the bacteria during the first 10 minutes. ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................(3)

St Michael's Catholic Grammar School

1

(ii)

Explain why there is a sharp increase in the number of viruses in the culture fluid after 10 minutes. ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................(2)

(c)

The replication cycle of human immunodeficiency virus (HIV) involves latency. Give two ways in which the structure of HIV differs from the structure of phage. 1 .................................................................................................................................... 2 ....................................................................................................................................(2)

(d)

Describe the growth curve you would expect to see for a virus whose replication cycle involves latency. ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... .......................................................................................................................................(2) (Total 11 marks)

2.

An experiment was carried out to study the growth of bacteria in a medium containing glucose as a carbon source. A liquid culture of bacteria was set up and incubated at 25 C for 24 hours. The glucose 3 concentration at the start was 0.05 mol dm . Samples were removed every 2 hours for 24 hours and the number of viable cells determined. (a) (i) Name one method which could have been used to determine the number of viable cells in this experiment. ........................................................................................................................... ...........................................................................................................................(1)

(ii)

State one precaution that must be taken to ensure an accurate count is made. ........................................................................................................................... ...........................................................................................................................(1)


2

The results of the experiment are presented in the graph below. 9 8 7 L o g 10 n u m b e r o f v ia b le c e lls 6 5 4 3 2 1 0

0

2 T

4 i m e o f

6 i n c u b

8 a t i o n /

1 h

0 o u r s

1

2

In a second experiment, another culture was set up in the same way. After 12 hours some 3 sucrose was added to the culture to give a sucrose concentration of 0.05 mol dm . Samples were removed every 2 hours for the next 10 hours and the number of viable cells determined. (b) (i) On the graph draw a line to show how the number of viable cells may have changed from 12 to 24 hours.(3)


3

(ii)

Give an explanation for the shape of the curve you have drawn. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(3) (Total 8 marks)

3.

A suspension of bacteria was spread evenly over solid medium in a petri dish. The culture was incubated at 25 C for 12 hours. After 12 hours two discs were placed on the surface of the medium. Each disc had been soaked in a different antibiotic (antibiotic A and antibiotic B). The culture was then incubated for 48 hours to allow the antibiotics to diffuse into the medium. The appearance of the culture before and after incubating with the antibiotic-soaked discs is shown below. A n tib io tic s o a k e d d is c B A B a c te ria l c o lo n ie s A p p e a re n c e o f c u ltu re a fte r 1 2 h o u rs , o n a d d in g th e a n tib io tic -s o a k e d d is c s A p p e a r e n c e o f c u ltu r e 4 8 h o u rs a fte r a d d in g th e d is c s A B


4

(a)

Describe the effect of each antibiotic on the growth of bacteria. Suggest a reason for the effect of each antibiotic. Antibiotic A ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... Antibiotic B ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ...............................................................................................................................(4)

(b)

Suggest why antibiotics such as penicillin affect bacterial cells but not the cells of the patient they are used to treat. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ...............................................................................................................................(3) (Total 7 marks)

4.

(a)

Distinguish between an endotoxin and an exotoxin.

..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(3)


5

(b)

Compare the structure of the (lambda) phage with the structure of the human immunodeficiency virus (HIV). ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(3) (Total 6 marks)

5.

The flow diagram below shows the steps involved in Gram staining a smear of bacteria.


6

(a)

Complete the table below by stating the colour that the Gram negative and Gram positive bacteria would appear after steps 4, 5 and 6. Step After step 4 After step 5 After step 6 Appearance of the Gram negative bacteria Appearance of the Gram positive bacteria

(b)

Explain why the Gram negative and Gram positive bacteria appear the colours you have described after step 5. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2) (Total 5 marks)

6.

An infection is caused when pathogenic microorganisms enter the tissues of the host organism and multiply. The symptoms of the infection may result from the production of toxins by the microorganism or from the destruction of host tissue. (a) Food poisoning can be caused by a number of pathogenic bacteria, including Salmonella and Staphylococcus. (i) Name the type of toxin produced by Salmonella. ...


7

(ii)

The symptoms of food poisoning caused by Salmonella occur 12 days after eating contaminated food. However the symptoms resulting from infection by Staphylococcus occur within a few hours after infection. Explain why this difference occurs. ... ... ... ...(2)

(b)

Salmonella is Gram negative whereas Staphylococcus is Gram positive. Describe how the colour of these bacteria would differ after Gram staining had been carried out. . . . .(2) (Total 5 marks)

7.

(a) The diet of a professional athlete is usually higher in carbohydrate than that of a non-athlete. Explain why this is necessary. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2)

(b)

The diagram below outlines different ways in which ATP can be produced in a muscle.A n a e r o b i c r e s p i r a t i o n

G

l y

c o

g

e n

G

l y

c o

g

e n

A

T

P

C p h

r e a t i n e o s p h a t e

A e r o b i c r e s p i r a t i o

n


8

(i)

As a result of training, the level of creatine phosphate in muscles increases. Explain how creatine phosphate generates ATP. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ...............................................................................................................................(2)

(ii)

From the information given above and your own knowledge, suggest how ATP would be produced in the muscles during a 100 metre sprint. Give two reasons for your answer. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ...............................................................................................................................(3) (Total 7 marks)

8.

(a) Explain the meaning of the term latency, as illustrated by the human immunodeficiency virus (HIV). ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(3)


9

(b)

Distinguish between endotoxins and exotoxins. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(3) (Total 6 marks)

9.

The table refers to some features of three different viruses. Complete the table by writing the appropriate word or words in the spaces. Virus Tobacco mosaic virus (TMV) (lambda) phage Human immunodeficiency virus (HIV)(Total 6 marks)

Type of nucleic acid

Structure

Example of host cell Leaf cell in tobacco plant

Complex

Bacterium

10.

(a)

Explain the meaning of the term antibiotic.

. . . .(2)

(b)

An experiment was performed to study the effect of the antibiotic penicillin on the growth of two species of bacteria: Lactobacillus bulgaricus and Escherichia coli. Each bacterial species was cultured in a flask containing 20 cm3 of liquid medium and penicillin. Control cultures without penicillin were also set up. At the start of the experiment each flask contained 1 106 bacterial cells per cm3 of culture medium.


10

At intervals of two hours, the number of bacterial cells in each culture was determined. The results are shown in the graph below. 14 13 c u ltu r e 12 11 10 9 8 7 6 5 4 3 0 (i) 2 4 6 8 10 12 14 16 18 20 22 24 T im e / h o u rs L . b u lg a r ic u s + p e n ic illin L . b u lg a r ic u s o n ly E . c o li + p e n ic illin E . c o li o n ly

Log

10

n u m b e r o f b a c te r ia p e r c m

3

Compare the growth of the control cultures of E. coli and L. bulgaricus over the 24 hour period. ... ... ... ... ... ...(3)


11

(ii)

Describe and explain the effect of penicillin on the growth of L. bulgaricus. ... ... ... ... ... ... ... ...(4) (Total 9 marks)

11.

The table below refers to structural features of bacteria and fungi. If the feature is present, place a tick () in the appropriate box. If the feature is absent place a cross (X) in the appropriate box. F D S C 7 M 0 u N A r r o e l l S e m w r i b b u a n n d e a t u d R e d c o s o m b r e N b n A y a p B a c t e rF i ua n r e s e n p i n r o g t c o i t i n a t g i

t e i n c h t a n

a l l o

t a i n e s o u p n

r e s e n d o r g

r a n

e

e l l e s

p

r e s e n

t

(Total 5 marks)

12.

The diagram below shows the structure of the human immunodeficiency virus (HIV).

P h o s p h o lip id b ila y e r

N u c le ic a c id

E nzym e


12

(a)

Explain what is meant by the term latency with reference to HIV infection. . . . .(2)

(b)

Name the enzyme found in this virus .(1)

(c)

Describe the role of this enzyme in latency . . . .(2)

(d)

Complete the table by giving two structural differences between HIV and tobacco mosaic virus (TMV). H IV 1. TM V

2.(2) (Total 7 marks)


13

13.

The diagram below shows the structure of a human immunodeficiency virus (HIV).

A

B

C

R e v e r s e tr a n s c r ip ta s e

(a)

Name the parts labelled A,B and C. A .. B ...... C ......(3)

(b)

State the function of the reverse transcriptase. .. ..(1)

(c)

Explain the meaning of the term latency in the replication cycle of this virus. .. .. .. ..(2) (Total 6 marks)


14

14.

Read the following passage on Gram staining, and then write on the dotted lines the most appropriate word or words to complete the account. Gram positive and Gram negative bacteria differ in their ability to keep a stain in their cell walls. A slide of bacteria is first flooded with a suitable stain such as . . All bacteria absorb this stain, which is then fixed with Grams . before being decolourised with . . Gram positive bacteria retain the stain complex, but Gram negative do not. Counterstaining with red stain, such as . causes Gram negative bacteria to absorb it and become red. Gram positive bacteria remain . in colour.(Total 5 marks)

15.

The graph below shows the number of new cases of HIV infection and AIDS in England in each year between 1992 and 1998. N e w c a s e s o f H I V in f e c tio n N e w c a se s o f A ID S

3000 2500 2000 N um ber of 1500 p e o p le 1000 500 0 92 93

94

95 Y ear

96

97

98


15

(a)

The graph shows that the number of new AIDS cases reported each year has decreased between 1996 and 1998. (i) Calculate the percentage decrease in the number of AIDS cases reported between 1996 and 1998. Show your working.

Answer.........................................(2)

(ii)

Suggest one reason for this change. .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... ..........................................................................................................................(2)

(b)

Explain why the number of people known to be infected with HIV is always likely to be greater than the number of AIDS cases reported. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(3)

(c)

Suggest why the number of people actually infected with HIV may be much larger than the data suggest. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2)


16

(d)

Explain why HIV can be described as a retrovirus. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2) (Total 11 marks)

16.

The diagram below shows the structure of a bacterium such as Salmonella enteritidis.

A

S to r a g e d ro p le ts

S to ra g e g ra n u le s(a) Give one function of the structure labelled A. .....................................................................................................................................(1)

(b)

State the main chemical component found in (i) the storage granules and (ii) the storage droplets. (i) (ii) granules............................................................................................................. droplets..............................................................................................................(2)


17

(c)

Describe how the presence of Salmonella enteritidis in the intestine may lead to food poisoning. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(3) (Total 6 marks)

17.

An experiment was carried out to test the sensitivity of the bacterium Bacillus subtilis to different antibiotics. The surface of a nutrient agar plate was flooded with a broth culture of the bacterium. The excess broth was discarded. Five filter paper discs, (A, B, C, D and E), each containing a different antibiotic, were placed on the nutrient agar surface. The plate was allowed to stand for 30 minutes at room temperature before being incubated at 30 C for 24 hours. The appearance of the plate after the incubation is shown in the diagram.

A

B a c te ria g ro w in g on agar

C le a r zones

E

B

A n tib io tic s d is c s D C

(a)

State two ways in which antibiotics may inhibit the growth of bacteria such as Bacillus subtilis. 1 .............................................................................................................................. ................................................................................................................................. 2 .............................................................................................................................. .................................................................................................................................(2)


18

(b)

Suggest why the surface of the nutrient agar was flooded with the broth culture rather than being inoculated by a streaking technique. ................................................................................................................................. .................................................................................................................................(1)

(c)

Suggest why the plate was allowed to stand for 30 minutes at room temperature before being incubated. ................................................................................................................................. .................................................................................................................................(1)

(d)

Suggest what the results indicate about the sensitivity of B. subtilis to the antibiotics. ................................................................................................................................. .................................................................................................................................(1) (Total 5 marks)

18.

The diagram below shows the structure of a human immunodeficiency virus (HIV).

(a)

Name the parts labelled A, B and C. A .............................................................................................................................. B .............................................................................................................................. C ..............................................................................................................................(3)


19

(b)

State the function of the reverse transcriptase. .................................................................................................................................... ....................................................................................................................................(1)

(c)

Explain the meaning of latency in the replication cycle of this virus. .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................(2) (Total 6 marks)

19.

The diagram below shows the structure of a human immunodeficiency virus.

RN A

P h o s p h o lip id b ila y e r A

B

(a)

Name the parts labelled A and B. A . B .(2)

(b)

Describe how the phospholipid bilayer contributes to the infection of the host cell. . . . .(2)


20

(c)

Once the virus has infected the cell there is a latent period. Describe the role of the RNA in this latent period. . . . .(2) (Total 6 marks)

20.

Read the following passage on Gram staining and then write on the dotted lines the most appropriate word or words to complete the account. Gram positive and Gram negative bacteria differ in their ability to keep a stain in their cell walls. A slide of bacteria is first flooded with a suitable stain such as .......................................... . All bacteria absorb this stain, which is then fixed with Grams ...............................................before being decolourised with ....................................................... Gram positive bacteria retain the stain complex, but Gram negative bacteria do not. Counterstaining with a red stain, such as ...................................................... causes Gram negative bacteria to absorb it and become red. Gram positive bacteria remain .................................................... in colour.(Total 5 marks)


21

21.

The table below refers to features of two viruses, tobacco mosaic virus (TMV) and human immunodeficiency virus (HIV). Complete the table by writing the appropriate word or words in the boxes. T o b a c c o i r u s ( T m H o us a m i c a n i m m u V ) v i r u s ( H I V n ) o d e f i c i e

F

e a t u

r e

v

M

T

y

p

e

o

f

n

u

c l e i c

a c i d

M

e a n

s

o

f

e n T t re a r ni n s gm

h i so s s i to

n

b

y

a p

h

i d

s

O

n

e

s i g

n

o

f

i n

f e c t i o

n

S

w

o

l l e n

g

l a n

d

s

(Total 4 marks)

22.

Read through the following passage on the human immunodeficiency virus and then write on the dotted lines the most appropriate word or words to complete the passage. The human immunodeficiency virus is a retrovirus. It contains the nucleic acid... and the enzyme

When this virus enters a .. lymphocyte, a copy of the viral genome is synthesised and incorporated into a .. in the host cell nucleus. In this state, the virus may remain dormant for a long time. The virus may become active when the body responds to a particular infection. This could result in a large number of new viruses being made which, when released, attack other cells of the. system of the body. (Total 5 marks)


22

23.

The diagram below shows the structure of a typical bacterial cell as revealed by electron microscopy.

(a)

Give one function for each of the structures labelled A, B and C. A .............................................................................................................................. B .............................................................................................................................. C ..............................................................................................................................(3)

(b)

Gram staining can be used in the identification of bacteria. (i) Explain the difference in appearance after staining between a sample of Gram negative bacteria and a sample of Gram positive bacteria. .......................................................................................................................... .......................................................................................................................... ..........................................................................................................................(2)

(ii)

Give one example of a genus of Gram negative bacteria. ..........................................................................................................................(1) (Total 6 marks)

24.

(a)

(i)

Name the organism that causes tuberculosis.(1)

...


23

(ii)

State one way in which this organism is transmitted from person to person. ... ...(1)

(b)

The table below shows (to the nearest 1000) the number of deaths per year from tuberculosis in England and Wales at 10 year intervals from 1905 to 1995. Y ear 1905 1915 1925 1935 1945 1955 1965 1975 1985 1995 N u m b e r o f d e a th s p e r y e a r 66 000 54 000 43 000 32 000 26 000 9 000 4 000 3 000 1 000 3 000

[Adapted from: Kavanagh & Denning, Biological Sciences Review, 8, no. 2] (i) Calculate the mean reduction per year in annual death rate from 1905 to 1945. Show your working.

Answer ..............................................(2)

(ii)

Antibiotics and immunisation against tuberculosis were introduced during the 1940s. What evidence is there in the data that this affected the annual death rate from tuberculosis? ... ...(2)

(c)

Suggest two reasons why the annual death rate from tuberculosis was failing before antibiotics and effective immunisation were introduced. 1 ...... 2 ......(2)


24

(d)

The data for 1995 suggest a rise in the annual death rate from tuberculosis. This may be linked to the increased incidence of HIV infection. (i) Suggest why HIV infection might increase the risk of developing tuberculosis. ... ... ... ...(2)

(ii)

Suggest one reason, other than HIV infection, which might lead to an increase in deaths from tuberculosis. ... ...(1) (Total 11 marks)


25

Documents

topic 6 rev