Nucleic Acids Flashcards
What biochemical processes do nucleotides take part in?
Nearly all
What are nucleotides structurally?
Phosphate waters of pentane sugars where a nitrogenous base is linked to carbon atom 1 of the sugar residue and a phosphate group is linked to either carbon atom 5 or 3 of the sugar residue.
What bonds form between nucleotides and how?
Covalent bonds formed by condensation reactions
Name the four main things nucleotides do?
Form monomers of nucleic acid, DNA and RNA
Become phosphorylated nucleotides when they contain more than one phosphate group
Help regulate many metabolic pathways
May be the component of many coenzymes
What is the nucleotide pentose sugar is?
Ribose
What in DNA is the nucleotide pentane sugar?
Deoxyribose
Nucleotides become a phosphorylated nucleotides when they contain more than one phosphate group.
Give an example of this?
ADP and ATP
What is ADP real name?
Adenosine diphosphate
What is ATP real name?
Adenosine triphosphate
What is ATP and what’s it used for?
ATP is an energy-rich end-product of most energy-releasing biochemical pathways
Used to drive more energy-requiring metabolic processes in cells.
Help regulate many metabolic pathways give examples?
ATP, ADP and AMP
What’s AMP real name?
Adenosine monophosphate
Adenine nucleotides are components of which coenzymes?
NADP
NAD
FAD
What is NADP real name?
Nicotinamide adenine dinucleotide phosphate
What is NADP used in?
Photosynthesis and respiration
Nucleotides are?
Molecules consisting of a five-carbons sugar, a phosphate group and a nitrogenous group.
What are the four bases?
AT
CG
A base is?
Adenine
C base is?
Cytosine
G base is?
Guanine
T base is?
Thymine
Where is DNA found in eukaryotic cells?
In the nucleus
What is DNA found in prokaryotic cells?
In the cytoplasm
What type of microorganism is DNA in?
Fungi
Bacteria
Some viruses
What type of material is DNA?
Hereditary
What does DNA carry?
Coded instructions used in the development and functioning of all known living organisms.
What is DNA one of the most important?
Macromolecules that make up structure of living organisms.
What are the other important macromolecules that make up the structure of living organisms?
Proteins, carbohydrates and lipids
Is DNA a monomer or a polymer?
A polymer
Why is DNA a polymer?
It is made up of many repeating monitored units (nucleotides)
What does DNA consist of?
Two polynucleotide strands
Define polynucleotide
Large molecule containing many nucleotides
Define macromolecules?
very large molecule commonly created by polymerization of smaller monomers
What direction do the two strands of DNA run in?
Opposite directions
Antiparallel
What does each DNA nucleotide consist of?
A phosphate group, deoxyribose and one of the four bases.
What is deoxyribose?
A five-carbon sugar
What type of bond is there between the sugar residue and the phosphate group in a nucleotide?
Covalent bond
Phosphodiester
When are phosphodiester bond broken?
When polynucleotides break down
When are phosphodiester formed?
When polynucleotides are synthesised
What length are DNA molecules?
Long
What does the length of DNA molecules allow?
They can carry a lot of encoded genetic information
How many different type of nucleotides does DNA consist of?
Four
What is the same in all nucleotides?
Phosphate and sugar groups
What differs in the type of nucleotide?
The nitrogenous bases differ
What are the four types of nucleotide?
Purine
Adenine or guanine (two rings)
Pyramidine thymine or cytosine (one ring)
How are the two Antiparallel DNA strands jointed together between bases?
Hydrogen bonds
How many hydrogen bonds does Adenine with thymine take?
Two
How many hydrogen bonds does Guanine with cytosine take?
Three
What does a purine always pair up with?
A pyramidine giving equal rungs of the DNA ladder
What can the rungs on the DNA do?
Twist into double helix
What does the double helix shape give?
Stability
What do the hydrogen bond allow the molecule to do?
Unzip for transcription and replication
How is the upright part of the large DNA molecules resembling a ladder formed?
Sugar-phosphate backbones of the Antiparallel polynucleotide strands
What do the opposite directions of the two strands refer to?
The direction the 3rd and 5th carbon molecules on deoxyribose are facing
What happens at 5 carbon end of the molecule?
The phosphate group is attached to the fifth carbon atom of the deoxyribose sugar
What happens at 3 carbon end of the molecule?
Where the phosphate group is attached to the third carbon atom of the deoxyribose sugar
What do the rungs of DNA consist of?
Complementary base pairs joined by hydrogen bonds
How stable is DNA stable?
Very
What is the integrity of the coded information on DNA within the base sequence?
Protected
Where is the majority of DNA in eurkayotic cells?
In the nucleus
In eukaryotic cells what what are the DNA tightly wound around?
Special histone proteins into chromosomes
What is a chromosome therefore?
A molecule of DNA
What also DNA bit is there inside mitochondria and chloroplast?
Loop of DNA without histone proteins
How is DNA in a prokaryotic cell?
In a loop and within cytoplasm not enclosed in nucleus
Are prokaryotic around histone proteins?
No so described as naked
What do DNA do viruses contain?
DNA Loop of naked DNA
What are all the genes within the cell called?
The genome
What carries instructions to make and maintain that organism?
The genome and the DNA within every cell of the organism
What does DNA have to do every time a cell divides?
DNA has to be copied so that each new daughter cell receives the full set of instructions
Do all DNA molecules replicate?
Yes
When does replication take place?
Interphase before the cell divides
What does this result in for eukaryotic cells?
Each chromosome having an identical copy of itself. At first they are joined together at the centromere forming two sister chromatids.
When does DNA in mitochondria and choroplasts replicate?
Every time these organelles divide just before the cell divides
What does a DNA molecule have to do to make a new copy of itself?
Unwind
Unzips
What happens when it unwinds?
Double helix is untwisted a bit at a time catalysed by a gyrase enzyme
What happens when it unzips?
Hydrogen bonds between nucleotide bases are broken. Catalysed by DNA helicase and results in two single strands of DNA with exposed nucleotide bases
What happens next in DNA replication?
Free phosphorylated nucleotides present in the nucleotide present in the nucleus are bonded to the exposed bases following complementary base-pairing rules
What does the enzyme do after this?
DNA polymerase catalyses the addition of new nucleotide bases in the 5’ to 3’ direction to the single strands of DNA uses every single strand of unzipped DNA as a template
What happens to the leading strand?
It is synthesised continuously whereas lagging strand is in fragments (discontinuous) that are later joined catalysed by ligase enzyme.
Next (hydrolysis)
Hydrolysis of activated nucleotides to release extra phosphate groups supplies energy to make phosphodiester bond between the sugar residue of one nucleotide and the phosphate group of the next nucleotide
What is the product of replication?
Two DNA molecules
Identical to each other and to parent molecules
Why is this product termed as semi-conservative replication?
Each of these molecules contains one old strand and one new strand
How do loops of DNA in prokaryotes and inside mitochondria and chloroplast replicate?
Semi-conservatively
Bubble sprouts from loop and unwinds and unzips and then complementary nucleotides join to the exposed nucleotides eventually the whole loop is copied.
Can errors occur in DNA replication?
Yes
How often do these mistakes happen?
Estimated 1 in 10^8 base pairs
What could this mutation do?
Change the genetic code example of point mutation.
What can proofreading enzymes do ?
Proofread and Edit out mistakes incorrect nucleotides reducing rate of errors
What is the problem with proofreading enzymes?
Many genes have such changes to nucleotides (alleles).
Are all mutations harmful?
No. Some may give no advantage and some may be advantageous.
What is RNA sugar molecule and is this different to DNA’s?
RNA sugar is ribose
DNA sugar is deoxyribose so yes it is different
What replaces pyrimidine base thymine in RNA?
The nitrogenous base uracil which is pyrimidine
Is having the base uracil in RNA different in DNA?
Yes DNA has thymine instead of uracil
Who has the longer polynucleotide chain?
DNA has a longer chain that RNA
What sort of stranded molecule are DNA and RNA?
RNA usually single- stranded
DNA double-stranded.
How many different types of RNA are there?
Three
mRNA, tRNA and rRNA
What’s mRNA?
Messenger RNA
What’s tRNA?
Transfer RNA
What’s rRNA?
Ribosomal RNA
What’s a gene?
A length of DNA that codes for a polypeptide or got a length of RNA that is involved in regulating gene expression
What does a gene contain?
A code that determines the sequence of amino acids in a particular polypeptide or protein
How much of an organism’s dry mass is protein?
75%
Name the two types of protein?
Structural proteins
Functional proteins
What determines the amino acid sequence of a polypeptide?
Within each gene there is a sequence of DNA base triplets that determine primary structure
What has to correct for the molecule to fold correctly and be held in its tertiary structure or shape?
The primary structure of a polypeptide is correct.
What does the primary structure of polypeptides enable?
It will fold correctly and be held in its tertiary structure it shape enabling it to carry out its function
Name an example of when the structure or shape affects its function relating to enzymes?
Shape of active site of enzyme molecule must be complementary to the shape of the substrate molecule
Name an example of when the structure or shape affects its function relating to antibodies?
Part of an antibody molecule must have a shape complementary to that if the antigens on the surface of an invading pathogen
Name an example of when the structure or shape affects its function relating to drugs?
A receptor on a cell membrane must have a shape complementary to the shape of the cell-signalling molecule, such as a hormone or a drug that it must detect
Name an example of when the structure or shape affects its function relating to ion-channel proteins?
Ion-channel protein must have hydrophilic amino acids lining the inside of the channel and lipophilic amino acids on the outside portion that will be next to the lipid bilayer of the plasma membrane.
Where are genes?
Nucleus
Where are proteins made?
Cytoplasm at ribosomes
How is the problem of these instructions being copied dealt with?
A copy of each gene is transcribed into a length of mRNA. Codons can now pass out of the nucleus to the ribosomes ensuring that the coded instructions are translated and the protein is assembled correctly.
What are codons?
A sequence of base triplets
What does the word transcribed mean?
Copied
What can the genetic code be described as?
Nearly universal
Degenerate
Non-overlapping
What does it mean that the genetic code is nearly universal?
In almost all living organisms the same triplet of DNA bases codes for the same amino acid
What does it mean that the genetic code is degenerate?
All amino acids except methionine and tryptophan there is more than one base triplet. This may reduce effect of point mutations as change in one base of triplet could produce another base triplet that still codes for the same amino acid
What does it mean by the genetic code is non-overlapping?
It’s read starting from a fixed point in groups of three bases. If base is added it deleted can cause frame shift as every base triplet after that and hence every amino acid coded for is changed.
Step one of Transcription of a gene into a length of mRNA?
Gene unwinds and unzips
Step two of Transcription of a gene into a length of mRNA?
Hydrogen bonds between complementary nucleotide bases break.
Step three of Transcription of a gene into a length of mRNA?
The enzyme polymerase catalyses the formation of temporary hydrogen bonds between RNA nucleotides and their complementary unpaired DNA bases. ATCGCUA (order of template strand)
Step four of Transcription of a gene into a length of mRNA?
A length of RNA that is complementary to the template strand of the gene is produced. It is therefore a copy of the other DNA strand-the coding strand
What is the final step of Transcription of a gene into a length of mRNA?
mRNA now passes out of nucleus through nuclear envelope and attaches to a ribosome
Where are ribosomes made?
In the nucleus
How does the ribosomes made in the nucleolus leave the nucleus?
It is made in 2 subunits and these pass separately out of the nucleus through pores in the nuclear envelope and then come together to form the ribosomes.
What helps to make these two subunits of ribosome one?
Magnesium ions
What are ribosomes made from?
ribosomal RNA and protein in roughly equal parts.
Where is transfer RNA molecules made?
In the nucleolus
Once the tRNA has been made in the nucleolus what does it do?
Pass out of the nucleus into the cytoplasm
What are tRNA like?
Single-stranded polynucleotides
can twist into hairpin shape.
At one end three nucleotide bases that recognises and attaches to a specific amino acid.
At the loop of the hairpin is an anticodon complementary to the codon of bases on the mRNA.
What’s an anticodon?
Another triplet of bases complementary to the codon
What do ribosomes catalyse?
The synthesis of polypeptides
What do tRNA do?
Brings amino acids it finds and places then where the anticodon bonds by temporary hydrogen bonds to the complementary codon on the mRNA molecule
What do ribosomes do as they move along the length of mRNA?
Reads the code and when two amino acids are adjacent to each other a peptide bond forms between them
What is needed for polypeptide synthesis?
ATP
What does the gene determine?
The amino acid sequence
What happens after the polypeptide had been assembled?
mRNA breaks down
Component molecules can be recycled into new lengths of mRNA with different codon sequence
What is helped by chaperone proteins in the cell to fold correctly into its tertiary structure to carry out its functions?
The newly synthesised polypeptide is helped
