A Grose 2015
Stage 3 HBS Extended Response
The Cell Membrane and Protein Synthesis (35marks)
Answer all the questions below relating to the Cell membrane and Protein Synthesis.
Draw a fully labelled diagram of the Cell membrane structure.
The main structure of the membrane is made up
of phospholipid molecules arranged in two layers
called a bilayer.
Each phospholipid molecule has a head that is
hydrophilic (water loving) and a tail that is
hydrophobic (water hating).
The phospholipids are arranged in the two layers
with their heads on the outside and tails on the
inside.
The membrane contains protein channels,
protein carriers, receptor proteins and cell
identity markers.
(5 marks)
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1
A Grose 2015
Stage 3 HBS Extended Response
Describe the function of the cell membrane.
(4 marks)
A physical barrier -The membrane separates the
cell cytoplasm from the extracellular fluid
around the cell.
1
Regulation of the passage of materials. The
membrane controls the movement of materials
into and out of the cell.
1
Sensitivity. The cell membrane senses changes
in the extracellular fluid.
It has receptors that are sensitive to particular
molecules in its immediate
environment.
Support. The membrane supports the whole cell
because the internal part is attached to the
microfilaments of the cell’s cytoskeleton.
Connections between the membranes of
adjacent cells support the whole tissue of which
the cell is a part.
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1
c) Explain how Active transport aids in moving substances across the cell membrane
(10 marks)
( 1 mark each)
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Active transport – requires energy from ATP.
Active process – energy is required to form the vesicle.
Substances are transported across the membrane against the concentration gradient
from a region of low concentration to a region of high concentration.
Mention of how the Sodium Potassium works. (2 marks)
Vesicular transport – Movement across the cell membrane in structures called
vesicles.
Endocytosis – taking liquids and solids into the cell.
Pinocytosis – taking liquids into the cell.
Phagocytosis – taking solids into the cell
Exocytosis – taking solids and liquids from the cell. The vesicle fuses with the cell
membrane then pushes the contents out into the extracellular fluid.
A Grose 2015
Stage 3 HBS Extended Response
d) Describe the process of Protein Synthesis.
(12 marks)
Protein Production
Any 5 of the following:
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transcription
DNA double helix is broken/ bond breaks between base pairs
DNA broken by RNA polymerase
mRNA/ pre-mRNA is formed
mRNA is a coding/ complementary strand
introns/ excess bases removed
mRNA moves from nucleus to ribosome/ mRNA moves through the nuclear
membrane
Any 5 of the following:
 translation
 ribosome attaches to one end of the mRNA
 ribosome reads the code
 codons/ triplet consist of 3 mRNA bases
 3 mRNA bases determine one amino acid
 start codon is AUG/ all proteins start as methionine
 tRNA brings amino acids to ribosome
 tRNA contains anticodons/ has complementary nucleotides to mRNA
 ribosome joins amino acids together
 polypeptide chain formed
(10 marks)
(e) The structure of a protein has either three or four levels of complexity.
Describe the four levels.
1. Primary structure- a chain of amino acids joined by peptide bonds.
2. Secondary Structure- Amino acid chain forms sheets or spirals due to bonding between
different parts of the chain.
3. Tertiary structure- produced by further bending and folding of protein.
4. Quaternary Struture-when two or more chains of amino acids interact.
(4 marks)
Total / 35