Biological molecules 2 Flashcards
What are nucleotides made up of?
-5 carbon pentose sugar
-Nitrogen-containing base
-Phosphate group
What are the functions of nucleotides?
-Energy currency for a cell (ATP)
-Building blocks for DNA and RNA
How many nitrogen-containing rings does a purine base have?
Two
How many nitrogen-containing rings does a pyrimidine base have?
One
What the two most common purine bases?
Adenine and guanine
What the three most common pyrimidine bases?
Cytosine, thymine and uracil
What makes nucleotides carry a negative charge?
The phosphate group
How is the sugar, base and phosphate group joined together?
Condensation reaction
How many phosphate groups does ATP have?
Three
What happens when energy is needed in a cell?
-The third phosphate bond is broken by a hydrolysis reaction
What enzyme breaks down ATP?
ATPase
What product is formed from the breakdown of ATP?
Adenosine diphosphate (ADP)
What are nucleic acids made up of?
Many nucleotide monomer units
What is the function of nucleic acids?
Carries all the information needed to form new cells
How are nucleic acids made?
Condensation reaction
What are the bonds in nucleic acids?
Phosphodiester bonds
What bases are present in RNA?
C, G, A and U
What bonds hold together bases?
Hydrogen bonds
How many bonds are between C and G?
Three bonds
How many bonds are between A and T?
Two bonds
What happens in semi-conservative replication?
The DNA unwinds and new nucleotides align along each strand
What happens in conservative replication?
The double helix remains intact and new strands form
Which enzyme catalyses the unwinding of DNA?
DNA helicase
What is the function of DNA polymerase?
Lines up and catalyses the linking up of the nucleotides along the template strand
What is the function of DNA ligase?
Catalyses the formation of new phosphodiester bonds between the two strands of DNA
Where does translation take place?
The surface of the ribosomes
What is a triplet code?
The code of three bases, giving 64 possible combinations
What is the definition of a gene?
A sequence of bases on a DNA molecule coding for a sequence of amino acids, that affect the phenotype
What is a codon?
A sequence of three bases on the DNA or RNA
How did scientists work out the codons of DNA?
Using mRNA as it is a complementary strand to the DNA acting as a reverse image of the original DNA sequence
how is the code non-overlapping?
Each base in a gene is only part of one triplet of bases that codes for one amino acid
What is an advantage of a non-overlapping code?
If point mutation occurs, It will only affect one codon and therefore one amino acid
How is the code degenerate?
The genetic code contains more information than is needed, there are 64 combinations.
What is the advantage of a degenerate code?
If the final base in the triplet is changed, the mutation could still produce the same amino acid with no effect on the organism
What is the structure of RNA?
Single helix
What are the three main functions of RNA in the process of protein synthesis?
-Carries instructions for a polypeptide from the DNA to the ribosomes
-Picks up specific amino acids from the protoplasm and carried them to the ribosome
-Makes up the bulk of ribosomes
Where does mRNA form a template?
On the antisense strand of the DNA
What does mRNA code for?
One polypeptide
What is the function of DNA-directed RNA polymerase (RNA polymerase)?
Allow parts of the DNA molecule to transcribe onto strands of mRNA
-catalyses the formation of phosphodiester bonds between the sugars and phosphate groups of the bases to form a strand of mRNA
How does mRNA allow protein synthesis to take place?
-Passes through the nuclear pores into the cytoplasm
-Moves to the surface of the ribosomes where protein synthesis takes place
What is the function of Transfer RNA (tRNA)?
Picks up particular amino acids from the cytoplasm and transports them to the surface of a ribosome to align with mRNA
What is an anticodon?
Sequence of three bases on tRNA that are complementary to the bases in a mRNA codon
What is the function of Ribosomal RNA (rRNA)?
To hold together the mRNA and tRNA and act as enzymes controlling the process of protein synthesis
What are polysomes?
Groups of ribosomes, joined by a thread of mRNA, that can produce mass amounts of a particular protein
What is transcription?
DNA information copied to mRNA
What is translation?
mRNA information translated into specific sequence of amino acids
What is mutation?
A permanent change in the DNA of an organism
What is point/gene mutation?
A change in one or a small number of nucleotides affecting a single gene
What are the three types of point mutation?
-Substitution
-Deletion
-Insertion
What is a substitution?
One base in a gene is substituted for another
What is a deletion?
Where a base is completely lost in the sequence
What is an insertion?
When an extra base is added, either a replication or a new base completely
What are chromosomal mutations?
A change in the positions of genes within chromosomes
What is whole-chromosome mutations?
When an entire chromosome is either lost during meiosis, or duplicated in one cell
What chromosome causes Down syndrome?
chromosome 21, 3 copies instead of two
How can mutations be advantgeous?
Could result in the production of a new and superior protein, giving an organism a reproductive advantage
What happens in sickle cell disease?
Haemoglobin molecules stick together to form rigid rods that give red blood cells a sickle shape
What mutation happens in sickle cell disease?
Point mutation, affects the protein chains making up haemoglobin
What happens to blood flow in sickle cell disease?
The sickle cells may block blood vessels
They don’t carry oxygen very efficiently
