Introduction to Cell Biology
(BOOK)
CH1. Introduction to the Cell
Cell biology is the study of the structure, function and behaviour of cells.
The universal features of cells on earth
The phenomenon of heredity (passing forward of genes) is central to the definition of life.
Living cells store information in the form of double stranded molecules of DNA. DNA are long, in
branched, paired polymer chains formed of four types of monomers called nucleutides: adenine A,
guanine G, cytosine C and thymine T. Each nucleotide consists of two parts: a sugar (desoxyribose)
with an phosphate group attached to it, and a base (A/G/C/T). Each desoxyribose is linked to the next
via the phosphate group.
Polymerization
The DNA polymer is extended by adding monomers at one end. DNA is synthesised on a template
formed by a preexisting DNA strand. The bases protruding from the existing strand binds to the bases
of the strand being synthesised. This is not randomly due to the complementary structures of the
bases: A binds to T and C binds to G. The two strands formed twist around each other forming a DNA
double helix.
The bond between the bases is a hydrogen bond and therefore weaker then the sugar-phosphate
links. This allows the DNA strands to be pulled apart without breaking the sugar-phosphate bonds
and each strand can function as a template for DNA replication. Thus, DNA is the information store
for heredity, and templates polymerisation is the way in which this information is copied throughout
the living world.
, DNA transcription
For DNA to carry out its information-bearing function, RNA and proteins should be formed. This
process begins with transcription in which segments of the DNA strand are used as template to
produce another kind of polymer called ribonucleic acid (RNA). In RNA the backbone is formed of
another sugar than DNA it is formed by ribose instead of deoxyribose. Another difference is that
Thymine T has been replaced by Uracil (U).
The RNA transcribed of the DNA strands are called RNA transcripts. These transcripts function as
messenger RNA (mRNA) that guide the synthesis of proteins.
Because the bases are not coupled, bases on the RNA strand can couple to complement bases.
Because the ability to couple to bases of the same strand, RNA strands can fold into numerous of
forms, which can all function for different processes.
Proteins
Proteins are as well long unbranched polymer chains formed by stringing together monomeric
building blocks called amino acids. There are 20 different amino acids which can all be linked to any
other amino acid in the set.
Each protein molecule is formed by polymer chains of amino acids, is a polypeptide which is a
molecule formed by many amino acids joined in a particular sequence.
The particular sequence makes how the polypeptide is folded into a three-dimensional form which is
unique for that polypeptide. The form makes that it can react and bind with other molecules and can
act as enzyme to catalyse reactions that make or break covalent bonds.
(BOOK)
CH1. Introduction to the Cell
Cell biology is the study of the structure, function and behaviour of cells.
The universal features of cells on earth
The phenomenon of heredity (passing forward of genes) is central to the definition of life.
Living cells store information in the form of double stranded molecules of DNA. DNA are long, in
branched, paired polymer chains formed of four types of monomers called nucleutides: adenine A,
guanine G, cytosine C and thymine T. Each nucleotide consists of two parts: a sugar (desoxyribose)
with an phosphate group attached to it, and a base (A/G/C/T). Each desoxyribose is linked to the next
via the phosphate group.
Polymerization
The DNA polymer is extended by adding monomers at one end. DNA is synthesised on a template
formed by a preexisting DNA strand. The bases protruding from the existing strand binds to the bases
of the strand being synthesised. This is not randomly due to the complementary structures of the
bases: A binds to T and C binds to G. The two strands formed twist around each other forming a DNA
double helix.
The bond between the bases is a hydrogen bond and therefore weaker then the sugar-phosphate
links. This allows the DNA strands to be pulled apart without breaking the sugar-phosphate bonds
and each strand can function as a template for DNA replication. Thus, DNA is the information store
for heredity, and templates polymerisation is the way in which this information is copied throughout
the living world.
, DNA transcription
For DNA to carry out its information-bearing function, RNA and proteins should be formed. This
process begins with transcription in which segments of the DNA strand are used as template to
produce another kind of polymer called ribonucleic acid (RNA). In RNA the backbone is formed of
another sugar than DNA it is formed by ribose instead of deoxyribose. Another difference is that
Thymine T has been replaced by Uracil (U).
The RNA transcribed of the DNA strands are called RNA transcripts. These transcripts function as
messenger RNA (mRNA) that guide the synthesis of proteins.
Because the bases are not coupled, bases on the RNA strand can couple to complement bases.
Because the ability to couple to bases of the same strand, RNA strands can fold into numerous of
forms, which can all function for different processes.
Proteins
Proteins are as well long unbranched polymer chains formed by stringing together monomeric
building blocks called amino acids. There are 20 different amino acids which can all be linked to any
other amino acid in the set.
Each protein molecule is formed by polymer chains of amino acids, is a polypeptide which is a
molecule formed by many amino acids joined in a particular sequence.
The particular sequence makes how the polypeptide is folded into a three-dimensional form which is
unique for that polypeptide. The form makes that it can react and bind with other molecules and can
act as enzyme to catalyse reactions that make or break covalent bonds.
