Page 14 - Q & A STPM 2022 Biology

Biology STPM Chapter 3 Membrane Structure and Transport
(b) – Some membrane proteins act as enzymes that function to catalyse
chemical reactions in the cell.
– Some proteins are receptors for specific substances such as hormones.
For example, hormone insulin molecules bind to the receptor on the
cell membrane of the liver cell and promotes the conversion of excess
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glucose to glycogen.
– Protein molecules form channels and carriers for passage of ions and
polar molecules to enter or leave the cell.
– Some protein molecules act as carrier proteins that are able to actively
Semester
1 transport molecules across the cell membrane. The process involves
the use of energy obtained from ATP.
– Cell adhesion proteins act to bind adjacent cells together to form
tissues that carry out specific functions.
– Glycoproteins with branching oligosaccharides are involved in cell-
cell recognition and act as antigen.
– Some protein molecules provide attachment sites for the cytoskeleton
filaments.

3.2 Movement of Substances across Membrane

Section A Multiple-choice Questions

Question 1
Which of the following methods of transport across the plasma membrane
uses ATP and is able to transport across a substance against concentration
gradient?
A Active transport
B Active transport and receptor-mediated pinocytosis
C Facilitated diffusion and active transport
D Facilitated diffusion, active transport and receptor-medicated pinocytosis

Answer : B
The active transport is the transport of molecules or ions across the membrane
against the concentration. The receptor-mediated endocytosis is a form of
endocytosis that makes use of receptors attached to the cell membrane to
engulf molecule. Both of these processes require energy.

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