1.5 Nucleic Acids And Their Functions Flashcards
What is the definition of translation
Changing the words of one language into the words in another language that have the same meaning
What is the two stages of protein synthesis
Transcription and translation
What is translation
The process that changes the coded information of mRNA into the correct sequence of amino acids, forming a polypeptide
What’s the function of tRNA
To carry amino acids to the ribosomes
What is amino acid activation
The attachment of an amino acid to its transfer RNA (tRNA)
The tRNA attaches to a specific amino acid in the presence of an enzyme and ATP (requires energy)
3 functions of tRNA
- tRNA’s carry specific proteins
- The tRNA cannot pick up an amino acid unless the amino acid is activated
- The amino acid attachment site of a tRNA will bind to a specific amino acid, if energy is supplied
What is translation step one (name and what is it )
Step one is initiation
The mRNA molecule with the START CODON AUG attaches itself to the ribosome. Most polypeptide chains start with AUG which codes for the amino acid methionine
What is translation step two
The tRNA, with and anticodon complementary to the first codon on the mRNA, attaches itself to the ribosome
Hydrogen bonds bind to the three bases of the codon on the mRNA to the complementary bases of the anticodon in the tRNA
Translation step three
A second tRNA molecule attaches to the ribosome. It has an anticodon complementary to the second codon on the mRNA
Translation step four
Elongation
The amino acids attached to the two tRNA molecules are close enough for a peptide bond to form between them. A ribosomal enzyme catalyses the formation of this bond.
The first tRNA leaves the ribosome leaving its attachment site empty.
Translation step 5
The ribosome moves one codon along the mRNA strand
The second tRNA molecule now occupies the first attachment site. Leaving the second site free
A third comes to fill this site and a peptide bond forms between the second and third amino acid
Translation step six
The ribosome moves along the mRNA stand reading off the message a codon at a time.
As it moves, more tRNA’s attach to the ribosome bringing their animo acids.
The polypeptide chain grows
Translation step seven
Termination
This continues until a stop codon occurs in the mRNA. These donor code for amino acids
The mRNA separates from the ribosome and the completed polypeptide chain is released to the cytoplasm
One gene one polypeptide hypothesis
1940s radiation damage to DNA prevented a single enzyme from being made. This led to one gene one enzyme hypothesis
Enzymes are proteins so became one gene one protein hypothesis
Some proteins like haemoglobin consist of more then one polypeptide so it let to one gene one polypeptide hypothesis
Define a gene
A gene is a sequence of DNA bases that codes for a polypeptide
What is post translation modification
Polypeptides that made on ribosomes carry through the cytoplasm to Golgi body. In the Golgi the polypeptide is folded into secondary, tertiary or quaternary structures
What is a haemoglobin / how is it made
Folded tertiary structure
Combines with non protein groups
Four polypeptides are combined (quaternary = 4)
Alpha helix regions (secondary structure)
Definition of transcription
An exact written copy of something
What carries the information to build a protein from amino acids
Dna carries the information to build the amino acids
DNA doesn’t leave the nucleus
What is immense involved in carrying
The genetic code from DNA in nucleus to the ribosomes in the cytoplasm where protein is made
Function of ribosomes
Site of protein synthesis
What 3 parts make up each nucleotide
A phosphate group
A Penrose sugar
A base which contains nitrogen
What is a cistron
The cistron is a length of DNA that forms a mRNA molecule. A cistron is often equivalent to a gene and codes for a specific polypeptide
Step one of transcription
DNA unwinds as the hydrogen bonds between the base pairs ar broken by the enzyme DNA helicase
Step two of transcription
One of the two DNA strands acts as a template against which a matching RNA strand is formed. RNA nucleotides are attracted to complementary bases on the DNA strand.
Step 3 of transcription
The enzyme RNA polymerase binds to the template strand of DNA at the beginning of the sequence to he copied. The enzyme moves along the DNA forming bonds that add nucleotides one at a time to the RNA strand
Step 3 of transcription
The enzyme RNA polymerase binds to the template strand of DNA at the beginning of the sequence to he copied. The enzyme moves along the DNA forming bonds that add nucleotides one at a time to the RNA strand
Step 4 of transcription
RNA polymerase separates from the DNA strand when it reaches a ‘stop’ signal. The transcript is complete and the newly formed RNA detaches from the DNA
What are extrons
Parts of dna that do code for proteins
What are introns
Non coding regions of a gene - these sequences don’t actually code for a protein
What are the two different types of sequences in a gene
Introns and exons
What is the two types of nucleus acids
Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)
Define polymers
A long chains of repeating units made up of nucleotides
What 5 carbon Penrose sugar is in dna
Deoxyribose
What 5 carbon pentode sugar is in rna
Ribose
What are the 5 types of bases
Adednin
Thymin
Gwanin
Cytosin
And uracil is only present in rna
What is the three bases with a single ring structure and the name for this
Cytosine, thymine and uracil
They are called pyrimidines
One way of reminding is based with second letter is ‘y’ and uracil are pyrimidines
What are the two bases with a double ring structure and the name of this
Adenine and guanine
They are called purines
What does uracil replace in rna
Urscilbreplaces thymine
What reactions breaks hydrogen bonds
Condensation reaction
What do hydrogen bonds hold together
Between the sugur and the phosphate group
What are the rules of base pairing
- Always pair the same way
- adenine and thymine
- cytosine with guanine - Bases are held together by hydrogen bonds
- 2 hydrogen bonds hold adenine and thymine together
- 3 hydrogen bonds hold cytosine to guanine
What is a double helix
Two polypeptide chains twisted into a helix
What are the two functions of dna
Replication and protein synthesis
Why is dna suited to its functions
- Very stable molecule
- Large molecule
- Strands are able to separate
- Base pairs are on the inside of the double helix which means genetic information is protected
What are the three types of RNA
- Messenger RNA (mRNA)
- Ribosomal RNA (rRNA)
- Transfer RNA (tRNA)
What is the functions of mRNA
- Long single stranded molecule
- Manufactured in the nucleus
- Carries the genetic code from the DNA to the ribosomes in the cytoplasm
- Lengths vary
What are the functions of rRNA
- Found in the cytoplasm
- Ribosomes are made up of ribosomal RNA and protein - they are the site of translation of the genetic code into protein
What are the functions of tRNA
- Small and single stranded molecule
- Base sequence c-c-a to which amino acid it carries is attached
- Sequence of 3 bases called and anticodon
- tRNA bring amino acids to the ribosome so that proteins can be synthesised
Functions of DNA
- Double stranded
- Penrose sugar is deoxyribose
- Organic bases present are adenine, guanine, cytosine and thymine
- Found in nucleus
- Permanent
- One basic form
What are the functions of RNA
1.single stranded
2. Penrose sugar is ribose
3. Organic bases present are adenine, guanine, cytosine and uracil
4. Made in nucleus but found throughout cell
5. May be temporary- existing for short periods only
6. Three basic forms: messenger , transfer and ribosomal RNA
What are the two major functions of DNA
Replication and protein synthesis
What is DNA
DNA is a molecule that carries instructions for the construction and behaviour of cells
Why do chromosomes make copies of themselves
- The new cells formed at cell division have all of the correct genetic
- The genetic information can be passed on to the offspring in the sperm and the egg
What’s the first step of dna replication
The hydrogen bonds between the bases break. DNA unwinds and the two halves of the molecule separate. This is catalysed by the enzyme helicase
What happens in the second stage of DNA replication
As the DNA unwinds, the bases are exposed. Therefore each half of the molecule acts as a template on which a new strand of DNA can be built
What is stage 3 of DNA replication
Free nucleotides attach to each template DNA according to the law of base pairing. The enzyme DNA polymerase catalyses the condensation reactions between the nucleotides
What is semi conservative replication
The original double helix separates into two strands. Each of which then acts as a template for the synthesis of a new strand
What is conservative replication
The original double helix remains intact and a completely new double helix is made
What is dispersive replication
The two new double helices contain fragments from both strands of the original double helix
What is the evidence of the semi conservative hypothesis
- Called ultracentrifugation
- the process spins liquid
-most dense molecules are forced to bottom of the tube - less dense particales found at top of tube
What 4 things should you keep the same during the process ?
- Speed
- Time spinning
- Density / concentration of gel
- Temperature
What are genes
Genes are small sections of DNA
What are chromosomes made up of
Made of long, coiled strands of DNA
What is the information that the gene carries called ?
Genetic information
How many bases code for one amino acids
3
What is the structure of RNA nucleotides
One phosphate group
One ribose Penrose sugar
One nitrogenous base
What is the structure of ATP nucleotides
One adenine base
One ribose Penrose sugar
Three phosphate groups
What is the structure of DNA nucleotides
One phosphate group
One deoxyribose Penrose sugar
One nitrogenous base
What molecule makes the energy available when it is needed is ?
ATP
How many kg of ATP do we make and break down each day ?
50kg
Is ATP an energy store ?
No, our body contains about 5G of ATP therefore isn’t a energy store
Hydrolysis by ATPase
- ATPase breaks the bond between the second and third phosphate
- removing the third phosphate group
- H2O adds
- is a reversible reaction
- needs 30.6KJmol-1
- Endergonic reaction
What are the advantages of atp
- Energy released quickly - one step reaction
- Involves one enzyme
- Energy released in small amounts 30.6KJ
- Is the universal energy currency
- Common source of energy in all living things
Uses of ATP
- Used in anabolic reactions
- Active transport
- Muscle contraction
- Nerve impulse transmission
