| what is the structure of mononucleotide in DNA? | phosphate group
nitrogenous base
deoxyribose pentose sugar |
| DNA | deoxyribonucleic acid
contains the genetic material that is used to build and maintain organisms by producing various proteins
DNA can be passed on from parents to offspring |
| what are the names of all the bases? | adenine
cytosine
guanine
thymine
uracil (in RNA instead of thymine) |
| structure of a DNA molecule | double helix structure
sugar-phosphate backbone
mononucleotides linked by phosphodiester bonds between phosphate group and pentose sugar
hydrogen bonds between bases |
| complementary base pairing | A - T and C - G in DNA
U - A in RNA |
| protein synthesis: transcription | RNA polymerase breaks the hydrogen bonds between DNA nucleotides and DNA unwinds forming a template/antisense strand and a coding/sense strand
at a start codon free RNA nucleotides form phosphodiester bonds between nucleotides and hydrogen bonds by complementary base pairing between RNA and DNA bases
a strand of mRNA is made once RNA polymerase has reached a stop codon
the mRNA molecule leaves the nucleus through a nuclear pore |
| protein synthesis: translation | a ribosome binds to the start codon on the mRNA molecule
a tRNA molecule enters and binds to the ribosome
each tRNA molecule attached to an amino acids which has an anticodon sequence
the tRNA anticodons bind with the mRNA codons by complementary base pairing forming hydrogen bonds
the synthesized amino acids are joined by peptide bonds to form a polypeptide chain
once the tRNA molecule has reached a stop codon the polypeptide chain breaks off, is packaged and sent off to be folded and modified |
| what is the role of RNA polymerase? | the enzyme that unzips DNA by breaking the hydrogen bonds between the nucleotide bases during DNA transcription |
| what is mRNA? | messenger RNA
the molecule that is made during DNA transcription that has a complementary base sequence to the coding strand of DNA and an identical base sequence to the template strand of DNA |
| what is tRNA? | transfer RNA
involved in translation
attached to amino acids |
| ribosomes | organelles in cells where the process of translation occurs during protein synthesis
can be attached to an endoplasmic reticulum or be free floating in the cytoplasm |
| what are codons? | the sequence of 3 nucleotides which form the genetic code in DNA and RNA molecules
they code for amino acids |
| what is the genetic code? | the sequence of bases on DNA consisting of triplets of bases which code for an amino acid
it is degenerate, non-overlapping, universal and also a triplet code |
| why is the genetic code a triplet code? | each of the three bases in a codon code for an amino acid |
| why is the genetic code degenerate? | more than one triplet codes for the same amino acid |
| why is the genetic code non-overlapping? | each triplet is only read once and triplets don't share bases |
| what is a gene? | a sequence of bases on a DNA molecule that codes for a sequence of amino acids in polypeptide chain |
| what is the basic structure of an amino acid? | contains amine group and carboxyl group |
| what are polypeptides? | long chains of amino acids joined by peptide bonds in condensation reactions
the primary structure of proteins |
| why is the primary structure of a protein important? | determines how the protein will be folded
determines what bonds should be formed in its 3D shape
determines the proteins properties and function |
| how does the primary structure determine other structures? | the R-groups in each amino acid determine what type of bonds are formed in the polypeptide chain |
| function and sturcture of globluar proteins | they have a functional role
they have complex tertiary/quaternary structures
they are soluble
example includes haemoglobin, hormones, antibodies and carrier proteins |
| function and structure of fibrous proteins | are for structural purposes
they are insoluble
usually secondary structures, not many tertiary/quaternary structures
they are long and parallel
cross linkages form microfibrils for tensile strength
examples include collagen |
| what is the primary structure of a protein? | a sequence of amino acids bonded by peptide bonds |
| what is the secondary structure of a protein? | the 2D arrangement of amino acids
can be alpha helix or beta pleated sheet |
| what is the tertiary structure of a protein? | the 3D folding of the secondary structure into a complex shape
the shape is determined by 3 types of bonds:
hydrogen bonds - attractions between partially charged atoms in R-groups
ionic bonds - salt bridges between oppositely charged R-groups
disulphide bridges - covalent bonds between sulphur atoms and cysteine |
| what is the quaternary structure? | the last level of protein structure
contains 2 or more polypeptide chains in its structure
is also a 3D structure like tertiary |
| collagen properties and function | fibrous protein
high tensile strength due to hydrogen and covalent bonds present
made of 3 polypeptides forming an alpha triple helix
main component of connective tissues
insoluble |
| haemoglobin properties and function | globular protein
soluble
made of 4 polypeptide chains so has quaternary structure
carries oxygen in the blood which binds to the haem group (Fe2+) in the protein |
| what are enzymes? | globular proteins
biological catalysts |
| what is activation energy? | the minimum amount of energy needed for a reaction to occur |
| how do enzymes lower activation energy | distort the substrate bonds
creates a charge distribution
reduce reaction entropy by bringing substrates closer together
provide an alternative reaction pathway |
| what is the active site of an enzyme? | the region on an enzyme where the substrate molecules bind and undergo a chemical reaction |
| what are the names of the two enzyme models? | lock and key model
induced fit model |
| how does the primary structure of an enzyme determine the active site's shape? | the order of amino acids and their R-groups influences which type of bonds are formed and how the protein folds into its tertiary structure |
| intracellular enzyme | enzymes that are made and used within the cell its made by |
| extracellular enzyme | enzymes that are made in a cell but not used by the cell |
| anabolic enzyme | enzymes that combines smaller molecules to make a larger one |
| catabolic enzyme | enzymes that are used to break down larger molecules into smaller ones |
| factors that affect enzyme activity | temperature
enzyme concentration
substrate concentration
pH |
| what is the induced fit model? | where the enzyme's active site adjusts around the substrate to fit
this goes against the lock and key model because it allows the enzyme to not have a fixed shape |
| investigate the effect of enzyme and substrate concentration on the initial rates of reaction | potatoes contain the enzyme catalase which breaks down hydrogen peroxide
cork bore and cut up the potato into evenly sliced disks into 5,10,15,20 and 25 disks sets
hydrogen peroxide in conical flask with gas syringe
add each number of potato disks to the hydrogen peroxide and measure the volume of oxygen produced every 10 seconds for 1 minute
repeat this 3 times for each set of disks to get mean
no disks present as control |
| why is the initial rate of reaction used? | the initial rate shows change whereas the end of the reaction stays constant
the initial rate allows for a graph to be able to be plotted |
