Page 31 - PRE-U STPM BIOLOGY TERM 1

Biology Term 1 STPM Chapter 2 Structure of Cells and Organelles

5. Each of the cisternae is of different sizes of 1-3 µm in diameter and
0.05 µm in thickness. There are channels connecting one cisterna
to another. Usually the whole stack is curved with its convex cis face
facing the nucleus. Sacs are added onto the convex surface from ER
for the transport of protein, lipid or carbohydrate.

6. Vesicles can bud off carrying secretion of protein, glycoprotein
2 or lipid. The whole cisterna of the outermost trans face can be
completely budded off as vesicles.
7. The membrane is of lipoprotein type. The membrane can be added
on to form new cisterna at one side and budded off completely on
the other side.
8. There are microfilaments that bind the cisternae to keep them in a
stack.
9. The functions of Golgi apparatus are as follows:
(a) It forms lysosomes through the budding of larger vesicles or
fusion of several smaller ones.
(b) It processes proteins transported from ER to form glycoprotein
before it is packaged into vesicles to be exported from the cell.
(c) It packs digestive enzymes and export them as in the pancreatic
glandular cells.
(d) It produces cell wall materials in vesicles, which are directed
to the cell plate where new cell wall is formed after mitosis in
meristem.
(e) It can process lipids to form glycolipids, package them, transport
and store them within the cell.
(f) It exerts some forms of control over internal transport of vesicles
from one part of the cytoplasm to another part.
(g) It also exerts control over the turn over of the plasma membrane
as each time exocytosis takes place, a certain amount of plasma
membrane is added.

Exam Tips Lysosomes
Remember the process of 1. Lysosomes are spherical vesicles that contain digestive hydrolases.
lysosome action, which
includes its membrane 2. They are found in cells that carry out endocytosis such as phagocytes
fusing with the membrane and protozoa. They are found in most animal cells as well as cells of
of organelle or plasma
membrane to release its metamorphorsising insects and tadpoles. Usually they are absent in
content of hydrolases. The plant cells except in immature xylem cells and sieve tubes.
hydrolases will hydrolyse
complex biochemicals to 3. There may be only one lysosome per cell. A lot of them are usually
their simple and absorbable present in the phagocytes and cells of the tadpole tail.
products.
Remember that nucleus, 4. It is spherical in shape, bound by a layer of lipoprotein membrane.
ribosomes, ER, the Golgi
apparatus and lysosome 5. The size varies from 0.1 to 0.5 µm.
are inter-related.
6. Its membrane is the usual single layer of lipoprotein but the enzymes
it carry do not digest it.

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