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TQAS BIOLOGY Essay

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0708-AS Biology Revision Top Priority Questions

AS BIOLOGY
TOP 60 QUESTIONS
Chapter 1
1- Fig.1.1 is an electron micrograph of a mesophyll cell from a leaf.

1.5μm

Fig.1.1

(a) Calculate the magnification of Fig.1.1. Show your working and express your answer to the nearest whole number.
(b) Identify, by using the letters A to D, a part of the cell shown in Fig. 1.1 where the following substances are located.
A chlorophyll
B cellulose
C DNA
D phospholipid
(c) State three ways in which the structure of a red blood cell differs from the structure of the cell shown in Fig.1.1.

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0708-AS Biology Revision Top Priority Questions

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2- Fig.1.2 is a diagram of a bacterium.

Fig.1.2
(a) Name structures Q to S.
(b) State the names of three …show more content…

(b) β globin has a tertiary structure that consists of eight helices arranged to give a precise three-dimensional shape.
Describe how the precise three-dimensional shape of a polypeptide is maintained.

9- Starch grains in plant cells contain both amylose and amylopectin.
Explain how both of these substances are formed from glucose in plant cells.

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Chapter 3
1- A student investigated the activity of catalase by measuring the release of oxygen from hydrogen peroxide. The reaction occurs as follows.
2 H2O2
2 H2O + O2
The student used a solution of catalase that was mixed with a 5% hydrogen peroxide solution and placed in the apparatus shown in Fig. 3.1. The total volume of gas collected was recorded every 15 seconds. The results are shown in Fig. 3.2.

Fig.3.1

Fig.3.2
(a) Explain why the total volume of gas collected after 210 seconds remains constant.
Catalase and hydrogen peroxide were kept separately at 10 °C for 30 minutes before they were added together. The reaction mixture was then kept at 10 °C.
(b) Sketch, on Fig. 3.2, the results you would expect when the experiment was repeated at 10 °C.

0708-AS Biology Revision Top Priority Questions

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(c) Describe and explain the results you would expect if the catalase solution was pretreated by being kept in a water bath at 70 °C before being added to the hydrogen peroxide. (d) Explain how you would use this apparatus

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