Friday, December 18, 2015
Friday, November 23, 2012
STPM BIOLOGY 2012 TIPS
Pls follow the link below for tips:
http://berryberryeasy.com/2012/10/stpm-biology-2012-%E2%80%93-tips-and-predictions-for-papers-9641-9642-and-9643/
http://berryberryeasy.com/2012/10/stpm-biology-2012-%E2%80%93-tips-and-predictions-for-papers-9641-9642-and-9643/
Wednesday, October 10, 2012
ANSWER - STPM TRIAL EXAM (IBM) - U6 2012 - MTC, P1
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1. C
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2. C
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3. D
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4. A
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5. B
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6. B
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7. C
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8. B
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9. A
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10. A
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11. E
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12. D
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13. C
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14. B
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15. B
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16. C
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17. A
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18. D
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19. D
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20. E
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21. D
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22. D
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23. E
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24. A
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25. D
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26. E
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27. A
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28. E
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29. D
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30. A
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31. B
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32. B
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33. B
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34. D
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35. C
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36. B
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37. C
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38. B
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39. B
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40. A
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41. C
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42. D
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43. C
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44. C
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45. A
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46. C
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47. C
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48. D
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49. C
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50. C
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Sunday, September 2, 2012
STPM Biology - chapter 3 (old syllabus); chapter 4 (new syllabus): Revision essay question 18
18. Define the term "enzyme" and relate its function and properties to its structure.
Answer:
Enzymes are substrate specific which means that it has a specific shape that allows only the wanted substrate to bond and react with it.Because of its structure and shape it can carry out its function in speeding up the reaction by lowering the activation energy needed for the reaction to take place.
by sharon teoh
STPM Biology - chapter 1 (old syllabus); chapter 3 (new syllabus): Revision essay question 36
36.
Give an illustrated account of the detailed structure and functions of the plasma membrane.
Answer:
(a) structure
Plasma membrane made up of two layers are composed of phospholipid .The hydrophilic heads of the phospholipids are in contact with water and extracellular fluid in the outer layer and the inner layer in in contact with the cytoplasm.The hydrophobic tails face each other in the middle of the bilayer.The protein molecules float about in phospholipid bilayer forming a mosaic pattern.There are two types of membrane protein which are globular protein.Intrinsic protein are the protein that are fully or partially embedded in the phospholipid bilayer. Extrinsic protein are the proteins that are found floating on the external or internal surface of the plasma membrane.Some of the membrane protein and phospholipid have short ,branched carbohydrate chains ,forming glycoprotein and glycolipid.Lipids such as cholesterol are inserted among phospholipid molecules.
(b) function
It is the protective membrane surrounds the outside of both Eukaryotic and Prokaryotic cells.It is made up of a double layer of phospholipid and controls the movement of various substances into and out of the cell.It also allows cell identification.It seperate interior of a cell from external environment.It is selectively permeable and amphipathic in nature.
Give an illustrated account of the detailed structure and functions of the plasma membrane.
Answer:
(a) structure
Plasma membrane made up of two layers are composed of phospholipid .The hydrophilic heads of the phospholipids are in contact with water and extracellular fluid in the outer layer and the inner layer in in contact with the cytoplasm.The hydrophobic tails face each other in the middle of the bilayer.The protein molecules float about in phospholipid bilayer forming a mosaic pattern.There are two types of membrane protein which are globular protein.Intrinsic protein are the protein that are fully or partially embedded in the phospholipid bilayer. Extrinsic protein are the proteins that are found floating on the external or internal surface of the plasma membrane.Some of the membrane protein and phospholipid have short ,branched carbohydrate chains ,forming glycoprotein and glycolipid.Lipids such as cholesterol are inserted among phospholipid molecules.
(b) function
It is the protective membrane surrounds the outside of both Eukaryotic and Prokaryotic cells.It is made up of a double layer of phospholipid and controls the movement of various substances into and out of the cell.It also allows cell identification.It seperate interior of a cell from external environment.It is selectively permeable and amphipathic in nature.
STPM Biology - chapter 1 (old syllabus); chapter 3 (new syllabus): Revision essay question 36
The figure below shows a
section through part of the fluid mosaic model of the cell surface membrane
with a Na+/K+ pump protein.
a)
Explain why the cell surface membrane is
described as a fluid mosaic.
The cell surface membranes is
described as a fluid mosaic due to the scattered mosaic arrangement of proteins
that float in the phospholipid bilayer. The bilayer is fluid as the lipid and
proteins molecules can move laterally and rotate on their axis.
b)
Describe how the channel surface of the protein
differs from its surface next to the phospholipid tails.
The channel
surface is hydrophilic to allow the passage of ions. The surface next to
phospholipid tails is hydrophobic in order to interact with the hydrophobic
fatty acid tails so that the protein stays in the membrane.
c)
Explain why Na+ and K+
cannot pass freely across the phospholipid bilayer.
Na+ and K+
cannot pass freely across the phospholipid bilayer because the bilayer is
impermeable to ions. The hydrophobic tails in the phospholipid bilayer repel
the ions, hence transport of the ions requires the Na+/K+
pump.
d)
Cholesterol and glycolipids are associated with
the cell surface membranes.
Suggest one function of each compound in
membranes.
Cholesterol:
Functions as a plug to reduce the entry and exit of polar molecules across the
cell
surface membrane.
Glycolipid: Functions
in cell-cell recognition, acting as receptor sites for chemical signals.
by qian ying
STPM Biology - chapter 2:Revision essay question 10
10. Carefully study the
drawings in the figure below made from observations of electron micrographs.
a)
Cells are divided into two major groups
according to their structures. To which group do the above cells belong?
Bacterial cell is belonged to
prokaryotic cell while plant cell is belonged to eukaryotic cell.
b)
Name the structures indicated by the letters A,
B and C on the diagrams above.
A:
Mesosome
B:
Nucleoid
C:
Plasmodesma
c)
State one difference between the structures
labeled B and H.
B contains DNA that lies free in
the cytoplasm and is not associated with protein or RNA, but H is bounded by a
double membrane nuclear envelope and it contains DNA that is associated with
protein and RNA to form chromosome.
d)
State the main function of the following
structures:
D:
Contains chlorophyll to trap light energy for photosynthesis.
E:
Synthesis lipids and undergo detoxification.
F:
Synthesis protein.
G:
Site of aerobic respiration to synthesis ATP.
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