Page 11 - Q & A STPM 2022 Biology

Biology STPM Chapter 3 Membrane Structure and Transport
Answer :
(a) P : Phospholipid bilayer
Q : Intrinsic protein
R : Extrinsic protein
S : Channel or pore protein
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T : Glycolipid Semester
(b) – Proteins are amphoteric.
– They have both basic and acidic proteins as they are zwitterions.
– Hence, their hydrophilic (polar) regions are in the aqueous parts, 1
either facing in or out of the membrane.
– Proteins also contain regions of hydrophobic amino acids which
enable them to interact with hydrophobic tails in the phospholipid
bilayer.

(c) – Provides structural support to the cell membrane.
– Allows transport across membranes by acting as pumps, carriers and
channel proteins.
– Are receptor sites for enzymes, hormones or antibodies.
– As antigens.
– Act as enzymes.
– Helps to link up neighbouring cells.

• The pore formed by the proteins encloses the channel which is the space
that allow substances to flow through the membrane.
• Glycolipids involve attachment of carbohydrate to the hydrophilic heads
of the phospholipid bilayer.
• Carbohydrates attached to the proteins form glycoproteins which act as
antigens.
• The proteins in the membrane have hydrophobic amino acid regions that
interact with the fatty acid ‘tails’ to repel water.
• The functions of the proteins include the functions of channel protein,
carrier proteins and proteins as receptor molecules for chemical signalling
between cells.

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Chapter 3.indd 51 11/2/21 9:21 AM