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Bio > Nucleic Acids And Proteins - Unit 3 AOS 1 > Flashcards

Nucleic Acids And Proteins - Unit 3 AOS 1 Flashcards

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Biology 101 flashcards
1
Q

Nucleic acid

A
  • A biomolecule made up of monomers of nucleotides that includes DNA and RNA
  • the polymer of nucleotides
  • a nucleic acid includes recurring units of nucleotides
  • they are connected together via a condensation reaction
  • the resulting chain of sugars and phosphate form a backbone with the nitrogenous base facing outwards facing
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2
Q

nitrogenous base

A
  • each nucleotide can have one of four nitrogenous bases
  • adenine, cytosine, guanine and thymine/uracil
  • guanine and adenine are purines (double ringed)
  • cytosine, and thymine/uracil are pyrimidines (single ringed)
  • the order of these bases will form a genetic sequence
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3
Q

nucleotide

A
  • the monomer of a nucleic acid
  • phosphate group, sugar and nitrogenous base,
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4
Q

DNA

A
  • a double stranded nucleic acid chain that contains the hereditary information and has the code fpr creating RNA
  • stored in the nucleus of eukaryotic cells
  • two strands of nucleotides bonded together by complementary base pairing
  • packaged into chromosomes
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5
Q

structure of DNA

A
  • two chains of DNA are held together by hydrogen bonding between complementary base pairing
  • the strands run antiparallel, forming a double helix
  • atoms will organise themselves into the most stable energy configuration
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6
Q

RNA

A
  • a single stranded nucleic acid chain that functions to transfer genetic instructions from the nucleus to the cell
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7
Q

types of RNA

A
  • mRNA is formed through transcription and carries the genetic information from the nucleus to the ribosome. each group of three nucleotides provides the information that codes for the addition of an amino acid
  • tRNA had anticodons that are complementary to the codons on mRNA and its role is to deliver and links amino acids to the specific sequence on mRNA
  • rRNA is the main structural component of ribosomes
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8
Q

Difference between DNA and RNA

A
  • DNA contains thymine, RNA contains uracil
  • DNA is double stranded, RNA is single stranded
  • DNA contains a deoxyribonucleic sugar, RNA contains a ribosome sugar with an oxygen on the second prime carbon
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9
Q

Amino acids

A
  • the monomer of polypeptide chains
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10
Q

Structure of amino acids

A
  • amine group
  • carbonyl group
  • r group is the variable component and is one of 20 variations
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11
Q

polypeptide

A
  • amino acids are covalently joined together in a condensation reaction to form a polypeptide bond
  • a dipeptide is when two amino acids join
  • polypeptides can be broken down back into amino acids via hydrolysis (requires water)
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12
Q

Peptide bond

A
  • a chemical bond between two amino acids
  • forms a polypeptide chain
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13
Q

Condensation reaction

A
  • two molecules are joined resulting in the loss of a smaller molecule
  • oxygen and hydrogen break off carboxyl group and a hydrogen breaks off the amine group, forming water
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14
Q

Protein structure (primary)

A
  • primary structure is the sequence of amin acids joined by peptide bonds to create a polypeptide chain
    formed by covalent bonds between the amine group and the carboxyl group of adjacent amino acids
  • it determines the sequence of R groups
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15
Q

protein structure (secondary)

A
  • secondary structure is when hydrogen bonds from between amino acids creating an alpha helix (spirals) or beta pleated sheet (arrows)
  • it results from hydrogen bonding of non-adjacent amino acids
  • alpha helix increases tensile strength
  • beta pleated sheet increases stability
  • random coils
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16
Q

protein structure (tertiary)

A
  • tertiary structure is formed through many bonds and interactions, creating a 3D functional protein
  • interactions between R-groups, including hydrogen bonds, disulphide bridges, ionic bonds and hydrophobic interactions
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17
Q

protein structure (quaternary)

A
  • quaternary structure forms when multiple polypeptide chains join together
  • can also include inorganic prosthetic groups
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18
Q

Proteome

A
  • the complete collection of proteins that are expressed within an organism
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19
Q

Function of proteins

A
  • transport - proteins are embedded in membranes controlling the entry and exit of substances
  • Hormones - proteins can act as hormones, coordinating an organisms activity by triggering a response e.g. insulin
  • immunity - proteins protect against disease by recognising and destroying pathogens
  • structure - proteins support cell and tissue shape e.g collagen
  • enzymes - proteins act as enzymes, calalysing chemical reactions e.g catalase
  • movement - contraction and movement of muscles, cilia and flagella
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20
Q

gene

A
  • a section of DNA that carries the instructions for building a protein
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21
Q

Gene structure - promoter

A
  • a region upstream from the coding region of a gene that acts as the binding sites for RNA polymerase
  • it denotes the starting position and direction of transcription
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22
Q

Gene structure - introns

A
  • the non coding DNA that does not contribute to the overall protein as they are removed during RNA processing
  • only in eukaryotes
23
Q

Gene structure - exons

A
  • the regions of coding DNA which are transcribed and translated into proteins
24
Q

Gene structure - Terminator

A
  • a sequence at the end of a gene that signals for transcription to stop
25
Q

Gene structure - operator

A
  • The binding sites sites repressor proteins which inhibit Gene expression. Only found in prokaryotes.
  • when a repressor protein is bound to a gene, RNA polymerase cannot bind to it, therefore transcription can not occur.
26
Q

gene structure (coding sequence)

A
  • the sequence of DNA that is actually transcribed into RNA
27
Q

Transcription

A
  • transcription factors RNA polymerase bind to the promoter and triggers the unwinding and separation of the DNA
  • RNA moves along the template strand, breaking hydrogen bonds between DNA strands, exposing the bases as the double helix is unwound
  • free RNA nucleotides are used to make a strand of pre-mRNA that is complementary to the template strand
  • RNA polymerase will continue until it reaches the terminator and the pre-mRNA is released
28
Q

translation

A
  • information of mRNA is converted into a sequence of amino aids and synthesised into a protein.
  • the 5 prime end of the mRNA binds to the ribosome
  • a tRNA molecule with a complementary anticodon binds to the codon attached to the mRNA and delivers the amino acid methionine.
  • the mRNA molecule is fed through the ribosome as more tRNA molecules deliver more amino acids.
  • as amino acids continue to be delivered, a peptide bond forms between each one, creating a polypeptide chain.
  • this process continues until the stop codon is reached which signals for the end of translation.
  • the ribosome is released into the cytoplasm where it can further fold into a protein.
29
Q

RNA processing

A
  • a 5 methyl cap is added to the 5 prime which prevents the mRNA from being degraded by enzymes and helps with the binding of te ribosome to the 5 prime end.
  • a poly-A tail is added to the 3 prime end which stabilises it and also prevents it from being broken down by enzymes. (polyadenylation)
  • in eukaryotes splicing is where chunks of RNA are removed. The introns are removed by spliceosome and the exons are joined together (only in eukaryotes)
30
Q

alternate splicing

A
  • different exons may also be sliced, allowing one strand of mRNA to form many different mRNA molecules.
31
Q

properties of the genetic code

A
  • the genetic code is a set of rules that defines how the information in nucleic acids is translated into proteins.
    universal: all organisms use the same code. the same sequence of nucleotides codes for the same amino acid in all organisms.
  • unambiguous: each codon is only capable of coding for one amino acid.
  • degenerate/redundant: amino acids may be coded for by more than one codon. the degenerate nature of the genetic code minimises the effect of random mutations because the codons that code for the same amino acids will typically only differ by one nucleotide.
  • non-overlapping: each codon is read on its own.
32
Q

gene regulation

A
  • the control of gene expression, typically achieved by switching transcription on or off
  • organisms use gene regulation to save energy by not making unnecessary gene products and to ensure cells are differentiated from one an other.
33
Q

gene expression

A
  • the process of reading a gene to create products
34
Q

structural gene

A
  • a region of DNA that codes for a protein that preforms a specific function within a cell such as enzymes
35
Q

regulatory gene

A
  • a region of DNA that codes for a regulatory protein which controls the expression of other genes
36
Q

repressor protein

A
  • a protein coded for by regulatory genes that prevents gene expression by binding to its operator
37
Q

activator protein

A
  • a protein coded for by regulatory genes that increases gene expression
38
Q

difference between eukaryotic and prokaryotic gene expression and regulation

A
  • in prokaryotes, there is an operator which id for the repressor protein to bond to. In eukaryotes, there are enhancers and silencers for activator and repressor proteins to bind to
  • transcription and translation occur separately in eukaryotes. In prokaryotes, it occurs at the same time
39
Q

operon

A
  • a cluster of linked genes (in prokaryotes) that share the same promoter and operator and are transcribed at the same time
40
Q

trp operon

A
  • a series of genes within certain species of bacteria that encode for the production of an enzyme responsible for synthesising the amino acid tryptophan
  • the expression of it is controlled by a transcription factor called the trp repressor
41
Q

tryptophan

A
  • can be used as a building block to create large complex protein
  • the rearrest amino acid
  • very energy expensive to make so its production needs to be regulated
  • the expression of it will depend on its levels within the cell
42
Q

low levels of tryptophan

A
  • transcription of the trp structural genes is started in order to increase the amount of tryptophan available
43
Q

high levels of tryptophan

A
  • transcription of the trp structural genes is stopped in order to prevent unnecessary production of the amino acid.
44
Q

repression

A
  • when there are high levels of tryptophan, tryptophan will bind to a repressor protein, causing it to undergo confirmational change
  • it changes into its active form, allowing it to bind to the operator , preventing RNA polymerase from transcribing the gene
  • when there is no tryptophan, it mans the repressors will not bind to the operator and so transcription can take place.
45
Q

leader sequence

A
  • contains two trp codons.
  • has sections that are complementary to one an other and can form hairpin loops
46
Q

attenuation when tryptophan levels are high

A
  • transcription and translation begin and the ribosome arrives at the two trp codons (in region 1) and tRNA brings tryptophan to be added to the polypeptide chain.
  • the robosome does not need to pause and so the mRNA molecule is folded in a terminator hairpin loop and this fold causes the mRNA to separate from the template stand
  • the RNA polymerase detaches, causing transcription to stop before any structural genes are transcribed
47
Q

attenuation when tryptophan levels are low

A
  • transcription and translation begin
  • the ribosome arrives at the try codons in region 1 and because there are not tryptophan’s available, it stops, while the RNA polymerase continues
  • this causes two regions to pull together, forming an anti-terminatory hairpin loop
  • this doesn’t cause the attenuator sequence to separate meaning the RNA polymerase can continue transcribing the gene.
48
Q

the protein secretory pathway

A
  1. ribosome
  2. rough ER
  3. transport vesicles
  4. Golgi apparatus
  5. secretory vesicles
49
Q

protein destinations

A
  • free ribosomes will synthesis proteins that are required for use within the cell
  • ribosomes bound to rough ER will synthesis proteins that are to be exported out of the cell.
50
Q

protein secretory pathway - ribosome

A
  • a ribosome assembles a polypeptide chain from amino acids by translating mRNA
  • proteins that are intended to be secreted from the cell are synthesised in ribosomes on the rough ER
51
Q

protein secretory pathway - rough ER

A
  • allows for the correct folding of the newly formed polypeptide chain before being transported to the Golgi apparatus
52
Q

protein secretory pathway - transport vesicles

A
  • carry protein buds from the rough ER to the Golgi apparatus.
  • the vesicles fuse with the Golgi membrane and release the protein into its lumen
53
Q

protein secretory pathway - Golgi apparatus

A
  • proteins are modified such as having sugar molecules added or removed.
  • they are then packaged into secretory vesicles and released.
54
Q

protein secretory pathway - secretory vesicles

A
  • they travel through the cytoplasm and fuse with the plasma membrane, releasing the protein via exocytosis

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