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(a) Table 1.1 shows some details of the five most common fatty acids found in samples of olive oil produced by olive plants grown in different regions in Portugal.
[Table 1.1]
Key
C : D = number of carbon atoms : number of double bonds in the hydrocarbon chain
X = missing detail
[Image_1: Table 1.1 with details of fatty acids including C:D values, structure, and percentages for oleic, palmitic, linoleic, stearic, and palmitoleic acids]
(i) Table 1.1 shows the C : D values for oleic acid.
In Table 1.1, write the values for D for each of the four other fatty acids listed. [1]
(ii) In the first column of Table 1.1, draw a circle around each of the fatty acids that can be described as saturated. [1]
(iii) State the detail of the chemical structure, represented by X, which is missing from Table 1.1.
.............................................................................................................. [1]
(iv) The analysis of the triglycerides present in the different samples of olive oil showed that:
• there are many different triglycerides present in olive oil
• each olive oil is different in its composition, but the same few triglycerides are present in all olive oils.
With reference to Table 1.1 and to the structure of triglycerides, suggest explanations for these observations.
................................................................................................................. [2]
(b) Glycerol is soluble in water. Triglycerides are insoluble in water.
Explain why water is a good solvent for some substances such as glycerol, but is a poor solvent for substances such as triglycerides.
................................................................................................................. [2]
(c) Phloem is the plant tissue responsible for the transport of organic substances, such as fatty acids, from one area of a plant to another. The tissue is composed of more than one type of cell.
Name the type of cell that forms the transport vessels of phloem tissue.
.................................................................................................................. [1]
572
504
540
People who become infected with human immunodeficiency virus (HIV) are at risk of developing HIV/AIDs, particularly if antiretroviral therapy (ART) is not available.
(a) In people infected with HIV, the use of ART also helps to reduce transmission of the virus to uninfected people.
Outline two control methods, other than ART, that can be used to reduce the transmission of HIV.
............................................................................................................................................................... .......................................................................................................................................................... [2]
In people with HIV/AIDs, a serious lung disease known as pneumocystis pneumonia can result from infection by an opportunistic pathogen known as Pneumocystis jirovecii.
Fig. 2.1 shows P. jirovecii cells in one stage of their life cycle, as seen using a light microscope at a magnification of x600.
(b) Define magnification.
..............................................................................................................[1]
Fig. 2.1 shows that P. jirovecii is a unicellular organism. Although the cells of many species of bacteria are the same size as those of P. jirovecii, research concluded that the organism is a eukaryote and is not a bacterium.
In 1988, analysis of ribosomal RNA (rRNA) resulted in P. jirovecii being classified as a fungus.
(i) Studies of the structure of P. jirovecii have identified that the cell wall is made of polysaccharides such as chitin and 1,3-$\beta$-D-glucan. Explain why this feature helped scientists to confirm that P. jirovecii is not a bacterium.
...........................................................................[1]
(ii) Scientists have identified other features of the cell structure of P. jirovecii. Some of these are listed in Table 2.1.
Complete each row of Table 2.1 so that the table shows:
• four structural features identified in P. jirovecii
• one function for each structural feature
• whether the structural feature is present (✓) or absent (✗) in bacterial cells.
``Table 2.1`
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