1.3 Flashcards
biological molecules 2
define nucleotides
molecules with 5 carbon pentose sugar, a nitrogen containing base, a phosphate group joined by condensation reactions
what is ATP made up of
base adenine, pentose sugar ribose, 3 phosphate groups
how is deoxyribose different to ribose
one less O2 atom
what is the difference between purine & pyrimidine bases
purine - 2 nitrogen containing rings
pyrimidine - 1 nitrogen containing ring
which bases are purines & pyrimidines
purines - adenine, guanine
pyrimidine - cytosine, thymine, uracil
where are phosphate ions found
cytoplasm
what charge do nucleotides have and why
negative charge due to the phosphate ion
what reactions occur in the production of nucleotides
2 condensation reactions
what does ATP stand for
adenosine triphosphate
how does ATP release energy
third phosphate bond in ATP is broken in a hydrolysis reaction catalysed by ATPase to form ADP and a free inorganic phosphate group (Pi)
roughly how much energy is produced when ATP is hydrolysed
34kj
what is ATP used for in the body
building new molecules
active transport
nerve impulses
muscle contractions
define redox reaction
reactions in which one reactant loses electrons (oxidised) and another gains electrons (reduced)
what is nucleic acid
polymers made up of many nucleotide monomer units that carry all the information needed to form new cells
what does DNA stand for
deoxyribose nucleic acid
how do nucleic acids bond together
condensation reaction forms a phosphodiester bond between the sugar and the phosphate group
both DNA and RNA have a ….. backbone
sugar-phosphate backbone
state the bonding pairs of the bases and the bonds in between them
A & T - 2 hydrogen bonds
C & G - 3 hydrogen bonds
describe the structure of RNA
single polynucleotide strand
can fold into complex shapes held through hydrogen bonds or remain as long thread-like molecules
describe the structure of DNA
2 polynucleotide strands twisted around each other into a double helix shape
10 base pairs for each complete twist
strands are 5 prime (5’) and 3 prime (3’)
define genome
the entire genetic material of an organism
what are the two main ideas of how DNA replicates
conservative & semi conservative replication
explain the idea behind conservative replication
the original helix remained intact and a new identical helix was formed outside of the current strand
how was conservative replication disproven
a samples of DNA were produced one with N 15 (denser) present then moved to a source of N 14
if conservative replication occurred then the sample would only contain N 15 in the original strands and new strands would be N 14 however it was found that the new DNA contained both N 14 and N 15 proving semiconservative replication right
summarize DNA replication
DNA unzips and unwinds with DNA helicase to create template strands
exposed bases attract free DNA nucleotides which is catalysed by DNA polymerase
then DNA ligase catalyses the formation of phosphodiester bonds between the two strands of DNA
where does translation occur
surface of ribosomes
define translation
the process by which proteins are produced via RNA using the genetic code found in the DNA
what is a triplet code and why are they needed
the code of three bases
can code for an amino acid or signal the beginning or end of a particular sequence of amino acids
define gene
a sequence of bases on a DNA molecule, contains coding sequence of amino acids in the polypeptide chain that effect an organisms phenotype
what is a codon
sequence of 3 bases in DNA or mRNA
why is mRNA required
DNA is too large of a molecule for the codons to be figured out
so mRNA forms a more readable complementary strand to DNA
what is meant by DNA being non-overlapping and degenerate
non-overlapping - codons do not overlap
degenerate - some base sequences code for the same amino acid
how is RNA different to DNA
contains u in replace of c
contains ribose instead of deoxyribose
what are the 3 main functions of RNA
carries instructions for a polypeptide from the DNA in the nucleus to the ribosomes
picks up specific amino acids from the protoplasm to the surface of the ribosomes
makes up the bulk of ribosomes themselves
what is the sense and antisense strand
antisense strand - the template strand, the section of DNA which codes for proteins
sense strand - the mRNA strand which has complementary base sequence transcribed from the antisense strand
explain how mRNA is formed
RNA nucleotides line up alongside antisense strand after it has been unzipped
RNA polymerase catalyses the formation of phosphodiester bonds between the RNA nucleotides to form a strand of mRNA
small mRNA molecules then easily pass through pores in the nuclear membrane to the cytoplasm then the ribosomes
what is an anticodon
sequence of three bases on a tRNA that are complementary to the bases in the mRNA codon
explain the structure of a tRNA molecule
found in the cytoplasm
clover leaf shape
made up of an anticodon and a binding site specific to certain amino acids found free in the cytoplasm
what is the function of tRNA in the synthesis of proteins
carries a specific amino acid and lines up with mRNA with the complementary codon on the ribosome surface
amino acids are lined up and peptide bonds form between them building the chain of amino acids
what is rRNA and its function
ribosomal RNA
makes up 50% of a ribosome
made in nucleus under the control of the nucleoli
moves into cytoplasm where it binds with proteins to form ribosomes
what do ribosomes do
consist of a large and a small subunit
hold together mRNA and tRNA
act as an enzyme controlling protein synthesis
what are polysomes
groups of ribosomes joined by a thread of mRNA that can produce large quantities of a particular protein
define mutation
a permanent change in the DNA of an organism
what is a somatic cell
a body cell
how does the body try and control mutation
specific enzymes cut out or repair any parts of the DNA strand which become broken or damaged
what is a point mutation
a change in one or a small number of of nucleotides affecting a single gene
what is a substitution mutation
one base substitutes another
what is a deletion mutation
when a base is completely lost in the sequence
what is a insertion mutation
when an extra base is added to the sequence
what is chromosomal mutation
changes in the position of entire genes within a chromosome
what is a whole-chromosomal mutation
entire chromosomes are either lost or duplicated during meiosis
give an example of whole-chromosomal mutation
down syndrome
3 copies of chromosome 21 instead of 2
what is sickle cell disease
a human genetic disease affecting the protein chains making up the haemoglobin in red blood cells as a result of a point mutation
why is sickle cell disease a problem
it causes haemoglobin to stick together and form ridged rods that give the red blood cell a sickle shape so they do not carry oxygen very efficiently and block small blood vessels
