into to amino acids and proteins Flashcards
exam 2
what is the central dogma of molecular biology
The flow of genetic information from DNA to RNA to proteins can be represented by a scheme called the central dogma of molecular biology
what is the information in DNA used for
- three nucleotides make a codon
- triplets code for amino acids
what is the exceptions to the universal code
- some organisms have slight modifications eg. mitochondria
- triplets code for different amino acids
greek name for protein
proteios meaning primary
what are the components of proteins
C,H,O,N (approx 16%) and sometimes S
what is the molecular weight of an amino acid
110 g mol-1
what is protein mass weighed in and how much does a large bio molecular way
- Daltons (Da)
- large bio moleucules >10,000 Da
what is the average protein length of amino acids
- 200
- most between 50 - 2000
functions of proteins
- transport
- fluid balance
- source of energy and glucose
- acid- base balance
- cell membrane structure and function
- enzymes
- hormones
- immune factors - antibodies
structure of amino acid
H2N—-CHR—–COOH
left- amine group
right - carboxyl group
central C - chiral carbon
R- residual group ( variable)
what are the two isomers of amino acids and which are only found in proteins
L isomer - only found in proteins - amino group on left side
D isomer - amino group on right side
what are the exceptions to the amino acid characteristics
- Glycine - has no enantiomers as it has two hydrogen groups
- Proline - a amino group is attached directly to side chain so makes an amide
how many essential and non essential amino acids are there and what do they mean
Non essential - 11 - humans can synthesis them
essential - 9 - cannot be synthesised
define peptide, polypeptide and proteins
peptide - <40-50 amino acids
polypeptide - >50 amino acids
protein - one or more polypeptides
what is a peptide bond
link the alpha amino group to the carbonyl group of the next amino acid
what is the primary structure of a protein
- sequence of amino acids in a single polypeptide chain
- most related to nutritional value
- makes the core amino acid backbone
- determines the chemical and physical characteristics
where does hydrogen bonding occur in the primary structure
backbone due to carboxyl group and hydrogen atoms bonded to amine group
cause, signs and treatment of sickle cell anaemia
cause - single error in amino acid sequence of haemoglobin
signs -anemia, chest, abdomen and join pain,
swollen hands and feet, frequent infections, stunted growth and vision problems
treatment - drug therapy, blood infusions, supplemental oxygen, bone marrow transplants, gene therapy
what is the secondary structure of a protein
folding of a protein due to hydrogen boding between elements in the amino acid backbone forming alpha helix or beta folded sheets
where do hydrogen bonds form in an alpha helix
every 4th amino acid forming a helical structure
what are the two type of beta folded sheets and how are they formed
antiparallel - amino acid strands run opposite directions
parallel - amino acid strands run the same direction
- rows of amino acids are liked by hydrogen bonds
where do loops form
outside of proteins when the protein folds into its tertiary structure
what are loops used for and what are their properties
- often binding sites for other molecules
- rich in hydrophilic residues as they are exposed to water
why are weak bonds important in polypeptides
- many weak bonds act in parallel to hold two regions tightly together
- stability determined by the number of non covalent bonds
what is the tertiary structure of a protein
- 3D folding and coiling of the polypeptide forming a globular structure
- maintained by ionic bonds, disulphide bridges and hydrogen bonds aswell as hydrophobic interactions
- contains multiple secondary structures
what are homomers
proteins made of all of the same sub unit
what are oligomers
proteins made of multiple subunits
what are heteromers
proteins made of different subunits
what is a proteins quaternary structure
- interactive folding of several polypeptide chains forming a single functional protein
- subunits held together by non covalent forces
what are protein domains
- a unit of organization distinct from the four structures
- usually contain 40 to 35- amino acids
- different domains are associated with different functions
how are protein domains formed
a substructure is produced by any part of the polypeptide chain and is folded interdependently into a compact, stable structure
what is sequence alignments used for
- identifys homologous protein domains
- uses short signature sequences
what is paralogous
- homologous sequence separated via a gene duplication event
- a gene in an organism is duplicated to occupy two different positions in the same genome these two copies are paralogous
what is orthologous
- homologous sequence separated via a speciation event
- species diverges into two separate species the copies of single gene in both species are said to be orthologous
what is post translational modification and what does it involve
- allows the newly made polypeptide chain to become fully functional
- involves 3D shaping and/or adding methylation and phosphorylation
how are proteins further modified
- attachment of carbohydrate, lipid or RNA groups
- attachment of small
inorganic and organic molecules eg. metal ions, vitamins, methyl groups and phosphorylation
what are cofactors
usually metal ions or small organic molecules necessary for protein activity
