Organisation
Selectivity
Energy Flow
Perpetuation
Evolution
Human Awareness
8
9
10
11
12
5
6
3
4
7
1
2
The structure of DNA
Chromosomes are made up of genes
DNA and protein synthesis
Structure and function of protein molecules in cells
The importance of polysaccharides and lipids
DNA replication
Enzymes
DNA and protein evidence for evolution
Mutations
Genetic manipulation
Some social consequences of genetic manipulation
Multiplying and sequencing DNA

Students should know and understand the following:
M1.
The chemical unit of genetic information in most organisms is DNA
M2.
The structural unit of information in the cell is the chromosome
M3.
The functional unit of information on the chromosome is the gene
M4.
The flow of information from DNA to protein is unidirectional in most organisms
DNA Î RNA Î protein
M5.
The three-dimensional structure of a protein is critical to its function
M6.
Polysaccharides and lipids are important macromolecules in cells and organisms
M7.
Specific base-pairing is the mechanism of DNA replication
M8.
Enzymes are specific for their substrate
M9.
Molecular recognition is an important property for life processes
M10.
Enzymes increase reaction rates by lowering activation energy
M11.
Macromolecules are used as energy reserves
M12.
DNA carries genetic information from one generation to the next
M13.
The universal presence of DNA is strong evidence for the common ancestry of all living things
M14.
DNA and protein sequences usually show greater similarity between closely related groups of organisms than between distantly related groups
M15.
Change in the base sequence of DNA can lead to the alteration or absence of proteins, and to the appearance of new characteristics in the descendants
M16.
Human beings can manipulate DNA
M17.
Human beings can sequence even small amounts of DNA
(© SSABSA Stage 2 Biology Curriculum Statement 2006, p22-24 and used with permission.
Teachers and students are advised to check the website www.ssabsa.sa.edu.sa for any changes.)

6 SACE 2 BIOLOGY E ssentials WORKBOOK
DNA   stands   for   ‘deoxyribonucleic   acid’.
This   molecule   is   found   primarily   in   the   nucleus   of   cells.
It   is   a   double   stranded   molecule   with   the   strands   wound   around   each   other   to   form   a   double   helix.
The   molecule   is   made   up   of   repeating   units   called   nucleotides.
A   single   nucleotide   is   made   up   of   three   components:   a   deoxyribose   sugar,   a   phosphate   and   an   organic   base.
The   diagram   below   is   a   representation   of   2   nucleotides   bonded   together.
Bases
A T
Deoxyribose sugar
Phosphate
C
T
C
C
T
G
A
G
G
A
A
A
G
A
A
A
G
G
T
T
C
T
T
T
C
C
Weak hydrogen bonds between bases
There   are   four   organic   bases   found   in   DNA:   Adenine,   Thymine,   Guanine   and
Cytosine.
The   letters   A,   T,   G   and   C   represent   these   bases.
A   single   strand   of   DNA   is   a   sequence   of   nucleotides   joined   together   with   alternating   phosphate   and   sugar   components.
The   double   helix   molecule   consists   of   two   complementary   strands   that   are   joined   by   hydrogen   bonds   between   the   bases.
The   bases   always   pair   in   specific   ways:
Adenine   always   bonds   with   Thymine
Guanine   always   bonds   with   Cytosine
Thymine   always   bonds   with   Adenine
Cytosine   always   bonds   with   Guanine
The   adjacent   diagram   shows   the   double   helical   model   for   DNA   first   proposed
by   two   scientists   Watson   and   Crick   in   1953.
1.
Write   a   concise   statement    to   explain   each   of   the   following   terms:
complementary    ……………………………………………………………………………………………...
DNA
macromolecule
………………………………………………………………………………………..….…
………………………………………………………………………………………..….…
monomer
nucleic   acid
nucleotide
organic
polymer
base
………………………………………………………………………………………..….…
………………………………………………………………………………………..….…
………………………………………………………………………………………..….…
………………………………………………………………………………………..….…
………………………………………………………………………………………..….…
………………………………………………………………………………………..….…
deoxyribose   sugar   ………………………………………………………………………………………..….…
phosphate     ………………………………………………………………………………………..….…
©
Crierie   A.
and   Greig   D.
2008
All   rights   are   reserved,   copying   is   prohibited   by   law.

Worksheet 1 THE STRUCTURE OF DNA
2.
The   following   sequence   of   bases   was   found   in   a   segment   of   DNA
7
A A G G C T T G C
Write   the   sequence   of   bases   that   would   be   found   in   the   complementary   strand.
……………………………………………………………………………………………………………………….
3.
Name   the   four   major   organic   bases   found   in   DNA.
………………………………………………………………………………………..……………………………...
4.
Write   down   the   four   possible   base   pairings   in   DNA.
………………………………………………………………………………………..……………………………..
5.
If   a   sequence   of   DNA   has   30%   guanine   bases   in   it   what   percentage   of   thymine   would   there   be?
………………………………………………………………………………………..……………………………..
6.
Refer   to   the   diagram   below.
Sugar Phosphate Sugar Phosphate Sugar Phosphate Sugar Phosphate
Base Base Base Base
(a)   Circle   a   nucleotide   in   the   representation   of   a   strand   of   DNA   shown   above.
(b)   How   many   nucleotides   are   shown   in   the   diagram?
……………………………………………………….
7.
Use   the   figure   to   label   A   B   C   and   D   in   the   diagram   below.
A
A T
B
C
D
A   …………………………………………………………………………………………………………………
B   ………………………………………………………………………………………..………………………..
C   ………………………………………………………………………………………..………………………..
D   ………………………………………………………………………………………..………………………..
©
Crierie   A.
and   Greig   D.
2008
All   rights   are   reserved,   copying   is   prohibited   by   law.

8 SACE 2 BIOLOGY Essentials WORKBOOK
Chromosomes   are   thread ‐ like   structures   made   up   of   DNA   and   proteins   call   histones.
These   structures   are   found   in   the   nucleus   of   eukaryotic   cells   and   are   visible   as   the   cells   start   to   divide.
The   chromosome   number   is   constant   for   each   species,   e.g.
46   in   humans,   48   in   a   chimpanzee,   40   in   a   mouse   and   38   in   cabbage.
Chromosomes   in   non ‐ dividing   cells   are   single   stranded   and   the   DNA   is   not   condensed,   that   is,   the   DNA   is   spread   out   to   make   it   easier   to   access   genes   in   transcription,   an   important   process   in   protein   synthesis   and   replication,   where   another   copy   of   the   DNA   is   made.
When   the   chromosomes   are   visible   during   the   Prophase   stage   of   mitosis   and/or   meiosis   they   appear   double   stranded.
This   doubling   has   occurred   as   the   DNA   has   replicated   in   order   that   new   cells   can   receive   their   complement   of   DNA.
A   gene   is   the   unit   of   heredity.
Genes   represent   sequences   of   the   bases   A   T   G   and   C   on   chromosomes   and   code   for   protein   molecules   or   parts   of   protein   molecules.
Each   gene   is   found   on   a   particular   chromosome.
Genes   prescribe   the   features   of   an   organism:   green   eyes,   skin   colour   or   the   shape   of   a   nose.
In   a   human   with   46   chromosomes   it   is   thought   that   there   are   around   40,000   genes,   each   chromosome   containing   hundreds   or   thousands   of   genes.
A   single   gene   usually   contains   between   300   to   several   thousand   bases.
Each   gene   has   a   start   and   a   finish   to   signal   where   transcription   begins   and   ends.
The   diagram   below   shows   schematic   representations   of   some   human   chromosomes   and   some   of   the   gene   locations   that   have   been   identified.
2 3
Familial
Colon Cancer
Retinitis
Pigmentosa
7 9
Cystic
Fibrosis
Malignant
Melanoma
11 12
Sickle Cell
Anemia
PKU
14 17
Alzheimer's
Disease
Breast
Cancer
The human genome project.
This   is   a   project   that   was   first   proposed   around   1987.
Its   aim   was   to   map   the   entire   sequence   of   genes   to   chromosomes   and   sequence   the   human   genome.
The   figure   above   illustrates   some   of   the   known   gene   locations   (loci).
In   Adelaide   a   group   of   scientists   at   the   Women   and   Children ʹ s   Hospital   is   involved   in   studying   chromosome   16.
This   overall   mapping   is   a   major   undertaking   as   there   are   approximately   3   billion   building   blocks   or   nucleotides   in   the   total   genome.
The   first   stage   was   completed   in   about   June
2000.
This   photograph   shows   a   typical   set   of   human   chromosomes,   which   was   taken   from   a   prepared   slide   using   a   light   microscope.
The   images   have   been   cut   out   and   pasted   together   to   show   the   homologous   pairs.
Until   recently   this   was   done   with   scissors,   it   is   now   done   with   computer   software   They   are   generally   numbered   and   arranged   from   longest   to   shortest.
The   sex   chromosomes   are   bottom   right   of   this   photo.
This   is   the   male   set   of   chromosomes   or   karyotype.
A   female   has   two   copies   of   the   longer   (X)   sex   chromosome    instead   of   one   long   (X)   and   one   short   (Y).
©
Crierie   A.
and   Greig   D.
2008   All   rights   are   reserved,   copying   is   prohibited   by   law.

Worksheet 2 CHROMOSOMES ARE MADE UP OF GENES 9
1.
Write   a   concise   statement   to   explain   each   of   the   following   terms:
.
chromatid      ……………………………………………………………………………………………...
chromosome
gene
……………………………………………………………………………………………...
……………………………………………………………………………………………...
genome      ……………………………………………………………………………………………...
2.
In   what   organelle   are   the   chromosomes   found   in   eukaryotic   cells?
………………………………………
3.
Why   are   the   chromosomes   not   usually   visible   in   non ‐ dividing   cells?
……………………………………………………………………………………………...………………………
……………………………………………………………………...………………………………………………
4.
Explain   the   differences   between   DNA,   genes,   chromosomes.
……………………………………………………………………………………………...………………………
……………………………………………………………………...………………………………………………
5.
What   does   it   mean   to   say   that   a   gene   is   linked   to   a   chromosome?
……………………………………………………………………………………………...………………………
……………………………………………………………………...………………………………………………
6.
Explain   the   significance   of   different   species   having   different   numbers   and   types   of   chromosomes?
……………………………………………………………………………………………...………………………
……………………………………………………………………...………………………………………………..
7.
Approximately   how   many   genes   are   there;
(a)   on   one   human   chromosome?
………………………...……………………………………………….
(b)   in   the   human   genome?
………………………...……………………………………………….
8.
Scientists   have   known   for   a   considerable   period   of   time   that   the   gene   for   colourblindness   is   on   the   X
chromosome.
(a)   Suggest   how   it   was   discovered   that   this   was   linked   to   the   X   chromosome.
……………………………………………………………………………………………...………………………
……………………………………………………………………...………………………………………………
(b)   Genes   like   this   are   said   to   be   ‘X ‐ linked’   and   the   characteristics   are   said   to   be   sex ‐ linked.
Explain   why   this   is   so.
……………………………………………………………………………………………...………………………
……………………………………………………………………...………………………………………………
9.
Explain   what   it   means   to   say   that   the   structural   unit   of   information   in   an   organism   is   the   chromosome.
……………………………………………………………………………………………...………………………
……………………………………………………………………...………………………………………………
……………………………………………………………………………………………...………………………
……………………………………………………………………...………………………………………………
©
Crierie   A.
and   Greig   D.
2008   All   rights   are   reserved,   copying   is   prohibited   by   law.

10 SACE 2 BIOLOGY Essentials WORKBOOK
Genes   on   the   DNA   code   for   a   specific   sequence   of   amino   acids   (aa)   that   comprise   a   polypeptide.
Several
poypeptides   usually   make   up   a   protein.
They   can   also   code   for   the   production   of   an   RNA   molecule.
Protein   synthesis   requires   two   steps:   transcription   and   translation .
Three   main   nucleic   acids   are   involved .
DNA :     provides   the   template   for   the   production   of   the   mRNA.
mRNA:   transcribed   from   the   DNA   and   provides   a   sequence   of   codons translated   into   a   sequence   of   amino   acids   on   the   ribosomes.
that   are   able   to   be   tRNA:   there   are   more   than   20   different   types   of   these,   each   one   capable   of   carrying   only   one   type   of   amino   acid.
Transcription
This   process   occurs   in   the   nucleus   of   a   cell   and   is   where   the   DNA   template   acts   as   a   code   to   transcribe   a   gene   segment   of   DNA   bases   into   a   working   copy   of   mRNA.
The   enzyme   involved   is   called   RNA
Polymerase.
The   diagram   below   shows   the   process   of   transcription.
C
C
T
T
C
T A
C
T
T
A
G
T
C
T
A
G
T A
RNA polymerase
A
C C G
U
U
C
A
A
G
C G
U A
U
C
C
C
G
C
U
U
C
T A
A
C
G
U
G
U
A
C
Nucleotides used to assemble the mRNA
DNA Template
Growing mRNA strand
T A
C G
mRNA   nucleotides   in   the   nucleus   are   binding   to   the   exposed   DNA   bases   to   form   a   working   copy   of   the   gene   that   will   be   able   to   be   translated   on   the   ribosomes   to   form   protein.
Translation
Is   a   process   where   the   codon   sequence   on   the   mRNA   is   translated   into   an   amino   acid   language.
tRNA   molecules   carry   specific   amino   acids   into   position   as   the   anti ‐ codon   of   the   tRNA   links   with   the   codon   on   the   mRNA.
The   next   diagram   shows   the   process   of   translation.
©
Crierie   A.
and   Greig   D.
2008   All   rights   are   reserved,   copying   is   prohibited   by   law.

Worksheet 3 DNA AND PROTEIN SYNTHESIS
Leucine Serine
Growing polypeptide chain tRNA molecule
11
A
U
A U
U A
U
A
C A
G U
Anti codon mRNA molecule codon ribosome
In   the   diagram   above,   leucine   and   serine   are   the   first   two   amino   acids   that   are   joined   together   by   peptide   bonds   to   start   the   polypeptide   or   protein.
The steps involved in protein synthesis can be set out as follows.
1.
The   double   helix   of   the   DNA   unwinds   and   unzips   at   the   required   gene   site   exposing   the   nitrogenous   bases   on   the   template.
2.
mRNA   nucleotide   bases   (A   U   G   C)   attach   to   the   exposed   DNA   bases   with   the   assistance   of   the   enzyme   RNA   polymerase.
3.
Once   the   sequence   for   the   mRNA   has   been   completed,   the   mRNA   is   released   and   moves   out   of   the   nucleus   into   the   cytoplasm.
4.
The   DNA   strands   will   rejoin   and   recoil   themselves   to   form   the   double   helix.
5.
The   mRNA   molecule   attaches   to   the   ribosomes   in   the   cytoplasm.
6.
Specific   amino   acids   combine   with   their   appropriate   tRNA   molecules.
7.
The   ribosome   moves   along   the   mRNA   molecule   attaching   the   appropriate   tRNA   anti ‐ codon   to   the   codon   on   the   mRNA.
8.
The   amino   acids   join   together   to   form   a   polypeptide   sequence.
9.
When   a   stop   codon   is   reached   the   translation   is   complete.
10.
The   protein   breaks   away   and   is   ready   for   use   within   the   cell,   or   to   be   packaged   and   secreted   from   the   cell.
1   Write   a   concise   statement   to   explain   each   of   the   following   terms:
amino   acid      ……………………………………………………………………………………………
anti ‐ codon
codon
……………………………………………………………………………………………
……………………………………………………………………………………………
RNA   polymerase    ……………………………………………………………………………………………
mRNA
ribosome
……………………………………………………………………………………………
……………………………………………………………………………………………
©
Crierie   A.
and   Greig   D.
2008   All   rights   are   reserved,   copying   is   prohibited   by   law.

12
transcription
translation
SACE 2 BIOLOGY Essentials WORKBOOK
……………………………………………………………………………………………
……………………………………………………………………………………………
tRNA      ……………………………………………………………………………………………
2.
To   help   you   identify   differences   between   DNA,   mRNA,   and   tRNA,   complete   the   following   statements   by   writing   the   appropriate   nucleic   acid(s)   after   each   one.
a.
is   single   stranded         ……………..
b.
has   a   double   helical   structure
c.
is   only   found   in   the   cytoplasm
d.
is   found   primarily   in   the   nucleus   of   a   cell
e.
contains   the   base   thymine
f.
contains   the   base   uracil
g.
is   involved   in   the   process   of   replication
h.
carries   amino   acids   to   the   ribosomes
i   has   triplets   of   bases   called   codons
j   is   found   in   both   the   nucleus   and   cytoplasm
……………..
……………..
……………..
……………..
……………..
……………..
……………..
……………..
……………..
k   has   three   bases   which   comprise   the   anticodon   ……………..
3.
Explain   the   role   of   the   following   in   the   process   of   protein   synthesis:
DNA    ………………………………………………………………………………………………………..
…………………………………………………………………………………………………………………………...
mRNA   ………………………………………………………………………………………………………..
…………………………………………………………………………………………………………………………...
tRNA   ………………………………………………………………………………………………………..
…………………………………………………………………………………………………………………………...
amino   acids   ………………………………………………………………………………………………………..
…………………………………………………………………………………………………………………………...
ribosomes   ………………………………………………………………………………………………………..
…………………………………………………………………………………………………………………………...
mitochondria……………………………………………………………………………………………………….
…………………………………………………………………………………………………………………………..
4.
Explain   the   difference   between:
a)   transcription   and   translation
………………………………………………………………………………………………………………………
………………………………………………………………………………………………………………………
b)   a   codon   and   an   anti ‐ codon
………………………………………………………………………………………………………………………
………………………………………………………………………………………………………………………
©
Crierie   A.
and   Greig   D.
2008   All   rights   are   reserved,   copying   is   prohibited   by   law.

Worksheet 3 DNA AND PROTEIN SYNTHESIS
5.
Use   the   diagram   below,   which   shows   a   summary   of   the   process   of   protein   synthesis,to   write   the   names   and   roles   of   the   structures   labelled:
NUCLEUS CYTOPLASM
13
T
C
A
G
T A
C
C
C
C
T
T
T A
C
T
A
G
T
T
A
C C G
U
U
C
A
A
G
C G
U A
U
C
C
C
G
C
U
U
C
T A
D
B
G
A
C
U
A
G
A
C
U
E
F
Leucine
J
Serine M
I
T A
C G
A
U
A
U
U
A
U
A
C
G
A
U
L
K
H G
A   …………………………………………………………………………………………………………………
B   …………………………………………………………………………………………………………………
C   …………………………………………………………………………………………………………………
D   …………………………………………………………………………………………………………………
E   …………………………………………………………………………………………………………………
F   …………………………………………………………………………………………………………………
G   …………………………………………………………………………………………………………………
H   …………………………………………………………………………………………………………………
I   …………………………………………………………………………………………………………………
J   …………………………………………………………………………………………………………………
K   …………………………………………………………………………………………………………………
L   …………………………………………………………………………………………………………………
M   …………………………………………………………………………………………………………………
©
Crierie   A.
and   Greig   D.
2008   All   rights   are   reserved,   copying   is   prohibited   by   law.

14 SACE 2 BIOLOGY Essentials WORKBOOK
6.
The   table   below   shows   which   codons   carry   the   information   for   each   amino   acid.
AUU
AUC
AUA
AUG
GUU
GUC
GUA
GUG
UUU
UUC
UUA
UUG
CUU
CUC
CUA
CUG ile ile ile
start/met val val val val leu leu leu leu phe phe leu leu
ACU
ACC
ACA
ACG
GCU
GCC
GCA
GCG
UCU
UCC
UCA
UCG
CCU
CCC
CCA
CCG ala ala ala ala thr thr thr thr ser ser ser ser pro pro pro pro
AAU
AAC
AAA
AAG
GAU
GAC
GAA
GAG
UAU
UAC
UAA
UAG
CAU
CAC
CAA
CAG asn asn lys lys asp asp glu glu his his gln gln tyr tyr stop stop
AGU
AGC
AGA
AGG
GGU
GGC
GGA
GGG
UGU
UGC
UGA
UGG
CGU
CGC
CGA
CGG
The   table   below   shows   the   names   of   the   amino   acids   together   with   the   abbreviations   used   in   the   table   above.
ala    =   arg    =   asn    =   asp    =   cys    =   gln    =   glu    =   alanine     arginine   asparagine aspartic   acid     cysteine    glutamine
glutamic   acid
gly his ile
=
=
=
glycine     histidine   isoleucine leu    =   leucine     lys    =   lysine
met    =   methionine     phe    =   phenylalanine
pro    =   proline     ser    =   serine     thr    =   threonine   trp    =   tryptophan     tyr    =    tyrosine   val    =   valine
Now,   use   the   table   of   the   genetic   code   and   names   of   the   amino   acids   given   to   help   you   complete   the   following   table.
DNA   base   triplets     AGA     ________   ________   ________
mRNA tRNA
codons anti ‐
codons
amino   acid   coded   for
________
________
________
CGG
________
________
________
CUG
________
________
________
methionine   gly gly gly gly ser ser arg arg cys cys stop trp arg arg arg arg
©
Crierie   A.
and   Greig   D.
2008   All   rights   are   reserved,   copying   is   prohibited   by   law.

Worksheet 4 STRUCTURE AND FUNCTION OF PROTEINS 15
Protein   molecules   are   large   polymers   made   up   of   about   20   common   building   blocks   called   amino   acids   linked   together.
Organisms   typically,   have   thousands   of   these   molecules.
Humans   are   thought   to   have   between   50,000 ‐ 100,000   different   proteins,   each   one   with   a   unique   three ‐ dimensional   structure   that   is   critical   for   its   particular   function.
Proteins   can   be   placed   into   2   main   groups,   fibrous   or   structural   proteins,   and   globular   proteins.
Protein structure can be studied at four levels
•
Primary   structure  ‐  the   sequence   of   amino   acids   linked   by   peptide   bonds.
Each   protein   is   characterised   by   its   own   unique   number,   type   and   sequence   of   amino   acids.
Typically   proteins   are   made   up   of   hundreds   to   thousands   of   amino   acids,   haemoglobin,   a   transport   protein,   is   some   400   times   bigger   in   size   than   a   glucose   molecule.
•
Secondary   structure  ‐  the   coiling   or   folding   of   the   polypeptide   chain.
•
Tertiary   structure  ‐  the   three ‐ dimensional   structure,   which   is   important   for   binding.
•
Quaternary   structure  ‐  applies   to   those   proteins   with   more   than   one   polypeptide   strand.
It   is   the   tertiary   structure   of   each   specific   protein   that   determines   its   specific   function.
If   the   delicate   three ‐ dimensional   shape   of   a   protein   is   altered,   it   usually   follows   that   the   function   of   that   protein   is   also
inhibited,   this   is   called   denaturation.
The   diagram   below   gives   a   diagrammatic   representation   of   the   different   levels   of   structure   in   a   molecule   of   haemoglobin   which   is   a   protein   found   in   blood.
ala
Polypeptide chain gly leu val lys
Heme
Polypeptide chain
PRIMARY
STRUCTURE
SECONDARY
STRUCTURE
TERTIARY
STRUCTURE
QUATERNARY
STRUCTURE
The   structural   proteins   are   more   fibrous   in   nature   and   tend   to   have   repeating   units   of   amino   acid   sequences,   whereas   the   globular   proteins   each   have   their   own   unique   sequences   giving   them   their   particular   shape   that   is   so   vital   for   their   function.
Types of proteins.
Proteins   can   be   placed   into   groups   depending   on   their   particular   roles   in   the   organism.
Structural
Examples   include   those   that   make   up   ligaments   and   tendons,   while   others   assist   in   movement,   for   example   muscle   proteins.
Keratin   is   an   important   structural   protein   found   in   organisms,   it   makes   up   the   outer   layer   of   skin,   and   is   the   main   component   of   hair,   nails,   wool,   beaks   and   feathers.
Proteins   embedded   in   the   cell   membrane   are   vital   for   the   efficient   functioning   of   cells.
Some   have   roles   in   acting   as   channel   proteins   allowing   certain   molecules   to   enter   or   leave   cells,   but   not   others.
Other   proteins   act   as   receptor   proteins   that   can   bind   to   chemicals   like   hormones,   and   thus   bring   about   a   particular   response.
Defence
Specific   protein   molecules,   called   antibodies,   are   released   from   white   blood   cells   and   have   a   role   in   the   inactivation   and   destruction   of   foreign   antigen   molecules   that   may   invade   our   tissues.
The   unique   shape   of   the   protein   antibody   means   that   the   action   of   each   antibody   is   specific   for   a   particular   antigen;   one   particular   antibody   can   only   bind   with   and   inactivate   one   particular   antigen.
©
Crierie   A.
and   Greig   D.
2008   All   rights   are   reserved,   copying   is   prohibited   by   law.

16 SACE 2 BIOLOGY Essentials WORKBOOK
Communication
Certain   molecules,   including   some   hormones,   bring   about   their   specific   action   by   binding   to   other   molecules.
When   the   hormone   insulin   binds   to   receptor   proteins   in   the   cell   membrane,   the   cell   membrane
increase   its   permeability   to   glucose   and   the   cell   takes   up   more   glucose   to   store   as   glycogen.
The   diagram   below   represents   the   binding   of   a   hormone   to   a   surface   receptor.
Hormone messenger molecule
Receptor molecule embedded into the bi-lipid layer of cell membrane
Lipid bi-layer
Binding leads to activation
Transport
Haemoglobin   is   a   protein   molecule   found   inside   human   red   blood   cells.
It   has   a   specific   role   in   the   transport   of   oxygen   molecules   to   the   tissues   of   the   body.
The   particular   shape   of   the   molecule   makes   it   ideal   for   the   reversible   binding   that   occurs   with   oxygen.
The control of metabolic reactions.
All   reactions   inside   cells   need   specific   enzyme   molecules   to   ensure   that   they   proceed.
Enzymes   are   protein   molecules   with   a   specific   shape   that   is   critical   for   the   binding   of   the   reactant   or   substrate   molecules.
The   three   dimensional   shape   of   the   protein   gives   rise   to   an   active   site   on   the   enzyme   where   an   induced   fit   binding   occurs.
1.
Write   a   concise   statement   to   explain   each   of   the   following   terms:
antibody     ……………………………………………………………………………………………
antigen     ……………………………………………………………………………………………
complementary   strand     ………………………………………………………………………………………..
denature     ……………………………………………………………………………………………
enzyme      ……………………………………………………………………………………………
haemoglobin
hormone
insulin
polypeptide
protein
surface   receptor
……………………………………………………………………………………………
……………………………………………………………………………………………
……………………………………………………………………………………………
……………………………………………………………………………………………
……………………………………………………………………………………………
……………………………………………………………………………………………
©
Crierie   A.
and   Greig   D.
2008   All   rights   are   reserved,   copying   is   prohibited   by   law.