Page 34 - PRE-U STPM BIOLOGY TERM 1

Biology Term 1 STPM Chapter 2 Structure of Cells and Organelles

Chloroplast envelope Ribosomes

Oil droplet

Thylakoid
Stroma
Granum 2
Language Check
Starch grain Language Check
Chloroplast DNA
Intergranal lamella
(a)

Intergranal lamellae

Language Check
Language Check
Thylakoid
• granum – singular
grana – plural
• lamella – singular
lamellae – plural

(b)
Figure 2.21 Structure of chloroplasts
9. The thylakoid membrane forms circular discs that are stacked like
shillings called granum.
Exam Tips
10. Each granum is made up of 10-100 thylakoids stacked together.
There are 40-60 grana per chloroplast. Remember the structure,
functions and distribution
11. There are channels called inter-granal lamella connecting one of chloroplast of flowering
plants.
thylakoid of a granum to another granum. These inter-granal Remember that three
lamellae form a network between the grana. The membrane of organelles i.e. nucleus,
the tylakoids and lamellae is lipoprotein in nature, but there are mitochondria and
chloroplasts are surrounded
photosynthetic pigments forming photosystems that are studded in by envelope of double
the membrane of both the lamellae and grana. Each photosystem lipoprotein membrane
consists about a mixture of 300 various chlorophyll, carotenoid and and they have several
similarities.
protein molecules to form a complex.
12. Stroma contains a colloidal sol where enzymatic reactions that
require no light to take place. It contains the followings:
(a) Enzymes, especially those involved in the Calvin cycle where
reactions forming carbohydrates and other organic compounds
take place.
(b) End products of photosynthesis such as sucrose, starch and fat
droplets, which are usually attached to the lamellae.
(c) Intermediate compounds, such as organic acids, phosphorylated
monosaccharides and their acids.
(d) Ribosomes of the 70S types.
(e) A circular ring of DNA and RNA.

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