Marieb casus 1.3
II De cel: eiwitsynthese (deel 1):
Chapter 2
2.11 DNA and RNA store, transmit, and help express genetic
information
The nucleic acids are the largest molecules in the body. The nucleic acids include two major
classes of molecules:
- DNA
- RNA
Roles of DNA and RNA
They have different roles in the cell.
Comparison of DNA and RNA
Characteristic DNA RNA
Major cellular site Nucleus Cytoplasm
Major functions Is the genetic material; Carriers out the genetic
direct protein synthesis; instructions for protein
replicates itself before synthesis
cell dividion
Structure Double strand coiled into Single strand, straight or folded
a double helix
Sugar Deoxyribose Ribose
Bases A, G, C, T A, G, C, U
Enzymen bestaan ook uit DNA.
DNA has two fundamental functions:
1. It replicates itself before a cell divides, insuring that the genetic information in the
descendant cells is identical
2. Provides the basic instructions for building every protein in the body
There are three major varieties of RNA
- Messenger RNA
- Ribosomal RNA
- Tranfer RNA
Structure of DNA and RNA
Nucleotides are the structural units of nucleic acids. Each nucleic acids consists of three
components:
- A nitrogen-containing base (A<C<G<T<U)
- A pentose sugar
- A phosphate group
,Purines: A en G zijn groter
Pyrimides: C, T, U
Double helix
Complementary bases
Summary of Monomers and Monomers Polymer
Polymers of Some Organic
Molecules
Carbohydrates Monosaccharides Polysaccharides
Proteins Amino acids Polypeptides or proteins
Nucleic acids Nucleotides DNA or RNA
Chapter 3
3.9
Nucleoli
Within the nucleus are nucleoli, dark-staining spherical bodies where the ribosomal subunits
are assambled.
Nucleoli are not membrane bounded.
Nucleoli are usually largest in growing cells that are making large amounts of tissue proteins.
Nucleoli are aggregations of all of the components needed to synthesize and assemble
ribosomal subunits. They centrer around the DNA that codes for ribosomal RNA (rRNA).
As rRNA molecules are synthesized, they combine with proteins to form the two kinds of
ribosomal subunits.
The finished subunits leave the nucleus through the nuclear pores and enter the cytoplasm,
where they join to form functional ribosomes.
Chromatin
Chromatin is a system of bumby threads weaving through the nucleoplasm. Chromatin is
composed of approximately:
30 % DNA
60 % histone proteins
10 % RNA chains
The fundamental units of chromatin are nucleosomes, which consist of flattened disc-
shaped cores or clusters of 8 histone proteins connected like beads on a string by a DNA
molecule.
The DNA winds twice around each nucleosome.
Histones provide a physical means for packing the very long DNA molecules in a compact,
orderly way, but also play an important role in gene regluation.
When a cell is preparing to divide, the chromatin threads coil and condense enormously to
form short, barlike bodies called chromosomes.
, 3.11 Messenger RNA carries instructions from DNA for building
proteins
Gene: segment of a DNA molecule that carries instructions for creating one polypeptide
chain.
Each sequence of three bases: triplet is a particular amino acid.
The coding regions: exons, they are seperated from each other by long interventing
sequences: introns.
Introns allow making different (related) proteins form one gene.
The role of RNA in Protein Synthesis
Most polypeptides are manufactured at ribosomes in the cytoplasm, but in interphase cells
3.11 Translation (cyclus 1.4)
In the translation step of prortein synthesis, the language of nuclei acids (base sequence) is
translated into the language of proteins (amino acid sequence)
Genetic code
amino acid sequence. Codon: three-base sequence.
64 mogelijke codons totaal, 3 stopcodons. Meerdere codons voor een aminizuur.
Role of tRNA
Translation involves the:
- mRNAs
- rRNAs
- tRNAs
tRNA has a anticodon: a three-base sequence, which binds to the mRNA codon calling for
the amino acid carried by that particular tRNA.
Because anticodons form hydrogen bonds with complemantary codons, tRNA is the link
between the language of nucleic acids and the language of proteins.
There are approximately 45 types of tRNA, each capable of binding with a specific amino
acid.
Activated by ATP.
Once its amino acid is loaded, the tRNA diffuses to the ribosome, where its amino acid is
positioned.
The ribosome holds the mRNA and tRNA close together to coordinate the coupling of codons
and anticodons.
3 sites by the large subunit ribosome:
- A: for incoming aminoacyl-tRNA
- P: for the tRNA holding the growing polypeptide chain
- E: exit site for an outgoing tRNA.
II De cel: eiwitsynthese (deel 1):
Chapter 2
2.11 DNA and RNA store, transmit, and help express genetic
information
The nucleic acids are the largest molecules in the body. The nucleic acids include two major
classes of molecules:
- DNA
- RNA
Roles of DNA and RNA
They have different roles in the cell.
Comparison of DNA and RNA
Characteristic DNA RNA
Major cellular site Nucleus Cytoplasm
Major functions Is the genetic material; Carriers out the genetic
direct protein synthesis; instructions for protein
replicates itself before synthesis
cell dividion
Structure Double strand coiled into Single strand, straight or folded
a double helix
Sugar Deoxyribose Ribose
Bases A, G, C, T A, G, C, U
Enzymen bestaan ook uit DNA.
DNA has two fundamental functions:
1. It replicates itself before a cell divides, insuring that the genetic information in the
descendant cells is identical
2. Provides the basic instructions for building every protein in the body
There are three major varieties of RNA
- Messenger RNA
- Ribosomal RNA
- Tranfer RNA
Structure of DNA and RNA
Nucleotides are the structural units of nucleic acids. Each nucleic acids consists of three
components:
- A nitrogen-containing base (A<C<G<T<U)
- A pentose sugar
- A phosphate group
,Purines: A en G zijn groter
Pyrimides: C, T, U
Double helix
Complementary bases
Summary of Monomers and Monomers Polymer
Polymers of Some Organic
Molecules
Carbohydrates Monosaccharides Polysaccharides
Proteins Amino acids Polypeptides or proteins
Nucleic acids Nucleotides DNA or RNA
Chapter 3
3.9
Nucleoli
Within the nucleus are nucleoli, dark-staining spherical bodies where the ribosomal subunits
are assambled.
Nucleoli are not membrane bounded.
Nucleoli are usually largest in growing cells that are making large amounts of tissue proteins.
Nucleoli are aggregations of all of the components needed to synthesize and assemble
ribosomal subunits. They centrer around the DNA that codes for ribosomal RNA (rRNA).
As rRNA molecules are synthesized, they combine with proteins to form the two kinds of
ribosomal subunits.
The finished subunits leave the nucleus through the nuclear pores and enter the cytoplasm,
where they join to form functional ribosomes.
Chromatin
Chromatin is a system of bumby threads weaving through the nucleoplasm. Chromatin is
composed of approximately:
30 % DNA
60 % histone proteins
10 % RNA chains
The fundamental units of chromatin are nucleosomes, which consist of flattened disc-
shaped cores or clusters of 8 histone proteins connected like beads on a string by a DNA
molecule.
The DNA winds twice around each nucleosome.
Histones provide a physical means for packing the very long DNA molecules in a compact,
orderly way, but also play an important role in gene regluation.
When a cell is preparing to divide, the chromatin threads coil and condense enormously to
form short, barlike bodies called chromosomes.
, 3.11 Messenger RNA carries instructions from DNA for building
proteins
Gene: segment of a DNA molecule that carries instructions for creating one polypeptide
chain.
Each sequence of three bases: triplet is a particular amino acid.
The coding regions: exons, they are seperated from each other by long interventing
sequences: introns.
Introns allow making different (related) proteins form one gene.
The role of RNA in Protein Synthesis
Most polypeptides are manufactured at ribosomes in the cytoplasm, but in interphase cells
3.11 Translation (cyclus 1.4)
In the translation step of prortein synthesis, the language of nuclei acids (base sequence) is
translated into the language of proteins (amino acid sequence)
Genetic code
amino acid sequence. Codon: three-base sequence.
64 mogelijke codons totaal, 3 stopcodons. Meerdere codons voor een aminizuur.
Role of tRNA
Translation involves the:
- mRNAs
- rRNAs
- tRNAs
tRNA has a anticodon: a three-base sequence, which binds to the mRNA codon calling for
the amino acid carried by that particular tRNA.
Because anticodons form hydrogen bonds with complemantary codons, tRNA is the link
between the language of nucleic acids and the language of proteins.
There are approximately 45 types of tRNA, each capable of binding with a specific amino
acid.
Activated by ATP.
Once its amino acid is loaded, the tRNA diffuses to the ribosome, where its amino acid is
positioned.
The ribosome holds the mRNA and tRNA close together to coordinate the coupling of codons
and anticodons.
3 sites by the large subunit ribosome:
- A: for incoming aminoacyl-tRNA
- P: for the tRNA holding the growing polypeptide chain
- E: exit site for an outgoing tRNA.
