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77 Cards in this Set
- Front
- Back
What are 2 types of nucleic acids?
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~ DNA and RNA
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Deoxyribonucleic acid is the molecule that?
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1) Carries the genetic code for protein synthesis in all cells 2) Replicates itself, ensuring the DNA is accurately copied for cell division |
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Ribonucleic acid is another nucleic acid that is?
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~ Involved in protein synthesis |
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Nucleic acids like DNA and RNA are polymers made up of?
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~ Many repeating monomers called nucleotides which bond together ~ Forming polynucleotides |
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The components of nucleotides are?
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~ Phosphate ~ Nitrogenous base |
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In DNA the pentose sugar is? |
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In RNA the pentose sugar is?
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~ Ribose |
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What elements are contained in pyrimidine bases (single structure)?
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~ Thymine, cytosine, uracil |
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What elements are contained in purine bases (double ring structure)? |
~ Adenine and guanine
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What elements are found in DNA?
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~ Thymine, adenine, guanine and cytosine |
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What elements are found in RNA?
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~ Uracil, adenine, cytosine and guanine |
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What is the structure of a DNA molecule?
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~ The 2 strands of the double helix are held together by weak hydrogen bonds between pairs of nitrogenous bases |
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How many hydrogen bonds can form between each complementary base pairs?
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~ Cytosine and guanine (3 hydrogen bonds) |
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Why is complementary base pairing important?
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~ As there will be the same proportion of adenine and thymine to cytosine and guanine in a DNA molecule |
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What are the 3 different types of RNA?
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~ Transfer RNA (tRNA) ~ Ribosomal RNA (rRNA) |
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What does mRNA do?
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~ It carries the genetic code for the polypeptide chain that will be formed in the translation stage of protein synthesis |
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What does tRNA do and what is its structure like?
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~ tRNA has an anticodon and an amino acid site |
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What does the rRNA do?
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~ Combines with protein to form ribosomes |
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RNA similarities with DNA?
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2) Each nucleotide is made up from phosphate, pentose sugar and base 3) There are 4 bases in RNA and DNA |
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RNA differences to DNA?
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1) RNA molecule have only 1 polynucleotide strand, DNA molecule comprise of 2 strands 2) DNA= Deoxyribose RNA= Ribose 3) DNA= Thymine RNA= Uracil (pairing with A) 4) DNA - remains within a cell for the whole of a cell cycle RNA- is synthesised and then broken down after use |
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Where is energy supplied by?
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What does ATP comprise of? |
~ Adenine nitrogenous base ~ 3 phosphate groups |
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What is ATP synthesised using?
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~ And energy is required to form a high energy bond between the 2nd and 3rd phosphate groups |
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What is ATP synthesis called?
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~ Phosphorylation |
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How is the synthesis of ADP + Pi to ATP catalysed by?
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~ The enzyme ATPsynthetase |
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What happens when the high energy bond is hydrolysed?
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~ ADP (adenosine diphosphate) + Pi (inorganic phosphate) is formed |
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What enzyme catalyses the hydrolysis of ATP to ADP?
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~ ATpase |
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When is ATP synthesised?
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~ Where chemical energy is transferred to cellular processes which require energy |
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How does ATP transfer chemical energy?
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~ When ATP is converted to ADP + Pi via the hydrolysis of the high energy bond |
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Why is it often called the universal energy currency in living organism? |
~ It supplies energy ~ Used in all reactions, in all cells ~ In all organisms |
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What are the advantages of using ATP as a source of energy?
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~ Only one enzyme is needed to release energy from ATP (glucose needs many) ~ ATP releases energy in small amounts when needed (glucose releases large amounts - which might not be needed) ~ Soluble ~ Can be transported across (organelle) membranes easily |
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Why must chromosomes make copies of themselves?
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What is the copying of DNA called?
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~ Semi conservative replication |
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Where and at what phase does replication occur?
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~ Nucleus and during interphase |
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How does replication occur?
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~ Catalysed by helicase enzyme 2) Each polynucleotide strand acts as a template for free DNA nucleotides align opposite unpaired exposed DNA bases 3) Free DNA nucleotides complimentary base pair and join to exposed bases ~ They bind to one another forming hydrogen bonds ~ DNA polymerase joins the DNA nucleotides together to form a complementary DNA polynucleotide strand 4) 2 double stranded DNA are formed |
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When 2 new copies rewind to form double helices, what is it called?
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~ Semi conservative replication |
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Why does DNA control the cell's activities?
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~ Enzymes are proteins ~ Enzymes catalyse all cell's reactions + the cell's characterises and functions |
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How is the primary structure determined? |
DNA determines the primary structure of a protein because the sequence of DNA bases determines the specific sequence of amino acids |
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How long is the code?
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~ Each sequence codes for one specific amino acid |
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1 base code generates?
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~ 4 combinations
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2 base code generares?
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~ 16 combinations |
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3 base code generates? |
~ 64 combinations to accommodate 20 different amino acids |
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4 base code generates?
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~ 256 combinations, which means that errors in copying the code would occur more frequently |
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When a polypeptide is required, what occurs?
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~ A triplet code in mRNA is called a codon |
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What is the region of DNA which contains the genetic code for a protein called? |
~ Exon or gene ~ This is the basis of the 'one gene one polypeptide' hypothesis |
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What exists between exons? |
~ Regions of non-coding DNA called introns |
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What are introns? |
~ Regions of non-coding DNA |
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What is the primary structure of a protein? |
~ Made up of a polypeptide chain ~ Which are amino acids joined together with peptide bonds ~ The unique sequence of amino acids |
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Which region of DNA on a chromosome contains the genetic code? |
~ Exon or gene |
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All triplet codes/ condons are universal |
All triplet codes/ codons are universal |
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What 2 stages of protein synthesis occur (in different parts of the cell)? |
~ Transcription ~ Translation |
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What does transcription do and where does it occur? |
~ The formation of mRNA
~ Occurs in the nucleus |
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What does translation do and where does it occur? |
~ The translation of the code into primary strcuture protein ~ Occurs at ribosomes in the cytoplasm |
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What is trasncription? |
~ The mechanism by which the base sequence of a gene on a DNA strand in converted into a complementary base sequence of mRNA |
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What are the phases of transcription? 1-3 |
1) DNA is physically too big to leave the nucleus via nuclear pores 2) RNA polymerase binds to DNA at the gene/ exon (specific sequence of DNA bases) to be copied and unwinded 3) DNA unzips |
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What are the phases of transcription? 4-5 |
4) Only one of the DNA strands is used as a template 5) Free RNA nucleotides align themselves opposite the complementary DNA base and joins = G to exposed C & A-U |
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What are the phases of transcription? 6-8 |
6) RNA polymerase moves along the strand joining nucleotides forming single stranded DNA 7) mRNA now carries the complementary codons - which code for specific amino acids 8) At the end the sequence of mRNA detaches and DNA rewinds |
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What are the phases of transcription? 9 |
9) mRNA transfers nucleotides through the nuclear pores to the cytoplasm - where it attaches to ribosomes consisting of ribosomal RNA and protein |
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Where does transcription take place? |
~ In the nucleus |
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What is the name and role of the enzyme involved in transcirption? |
~ RNA polymerase ~ Binds to the gene/ exon of DNA ~ To be copied and unwinds ~ Then moves along the strand, joining nucleotides forming single stranded mRNA |
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Which type of RNA is the genetic code transcribed to? |
~ messenger RNA (mRNA) |
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mRNA is converted into what? (translation) |
~ Into amino acid sequence (protein primary structure)
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What does tRNA form? (translation) |
~ It is a single strand ~ Forms a 'clover leaf' shape due to base pairing being possible in certain sections of the molecule |
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Exposed bases at the bottom of a molecule are called what? |
~ Anticodon |
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Why is anticodon important? |
1) It determines the specific amino acids that attaches to that tRNA molecule ~ Therefore the sequence of amino acids in the polypeptide chain 2) Only the anti-codon can base pair with the codon on the mRNA which is complementary |
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What does translation involve? 1-2 |
1) mRNA strand moves out of the nucleus via nuclear pores to the cytoplasm
2) A ribosome attaches to the mRNA strand which is held in place |
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What does translation involve? 3 |
3) In the surrounding cytoplasm an amino acid is activated by ATP and is attached - to a specific tRNA molecule via specific attachment site - which carries amino acid at one end and an anticodon at the other |
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What does translation involve? 4-6 |
4) tRNA molecules bring specific amino acids to the mRNA 5) The anti-codon of the tRNA complementary base pairs to the start codon of the mRNA 6) tRNA forms hydrogen bonds with mRNA |
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What does translation involve? 7-8 |
7) Another tRNA complementary base pairs to the second codon of the mRNA 8) A ribosomal enzyme catalyses peptide bond (requiring ATP) formation between an amino acid on one tRNA and the growing polypeptide on the other tRNA |
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What does translation involve? 9 |
9) The first tRNA is released and returns to the cytoplasmic pool to join to the same specific amino acid |
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What does translation involve? 10 |
10) A ribosome passes along mRNA, one codon at a time - tRNA with the appropriate anticodon fills the vacant slot and the amino acid forms a peptide bond with the last member of the chain using energy from ATP -until a stop codon is reached |
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How may the polypeptide be further modified? |
~ In the golgi body e.g. glycoprotein ~ A protein may consist of more than one polypeptide e.g. fibrous and quaternary proteins |
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What is the role of tRNA is tranlation? |
~ tRNA molecules bring specific amino acids to the mRNA |
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How many codons of mRNA can fit into the ribosome? |
~ 1 |
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When the first tRNA is released, where does it go? |
~ It returns to the cytosplamic pool ~ To join to the same specific amino acid |
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When tRNA has an appropriate anticodon and fills the vacant slot, what happens? |
~ The amino acid forms a peptide bond with the last member of the chain ~ Using ATP |
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What is the name and role of the enzyme involved in translation? |
~ A ribosomal enzyme ~ Which catalyses the formation of a peptide bond forming between an amino acid on one tRNA and the growing polypeptide on the other tRNA ~ Requiring ATP |