B1.2 - proteins Flashcards
proteins
Complex macromolecules composed of one or more chains of amino acids
amino acids
Monomers used to make proteins
NH2 (amino group)
H (hydrogen atom attached to central carbon)
R side chain
COOH (carboxyl group)
bonding + reactions of amino acids in protein
Amino acids join together by condensation reaction
Peptide bond formed when the carboxyl group (–COOH) of one amino acid reacts with the amino group (–NH2) of another amino acid to form a dipeptide
n terminal, c terminal
role of proteins
catalysis, signalling pathways, structural support
word equation of amino acids to create dipeptide
amino acid + amino acid → dipeptide + 1 water molecule
essential amino acids
amino acids that your body CANNOT produce.
Obtain from food
non-essential amino acids
produced by body from other amino acids/ breakdown of proteins
genetic code
set of rules specifies how info in DNA is translated into sequence of amino acids
universal language of all living things
transcription
DNA —> mRNA
translation
mRNA —-> sequence of amino acids
codon
group of 3 nucleotides that specify type of amino acid/ stop signal required
genetic code is degenerate
multiple codons (64) can code for the same amino acid (20)
allows for silent mutations!!
peptide bond
covalent/stable bond between carboxyl group of one amino acid to amino group of the other amino acid
lets add another amino acid to the chain
n-terminal NOT involved in peptide bonds, new amino acids are added to the c-terminal
list examples of polypeptides
lysozyme, alpha-neurotoxins, glucagon, myoglobin
lysozymes
enzyme composed of 129 amino acids
tears and saliva
antimicrobial properties (disrupts cell wall)
How do extremes of pH impact the structure of a protein?
It denatures the protein by changing the 3D conformation
haemoglobin
- 4 polypeptide chains
- conjugated protein
- binds to oxygen
- 4 subunits held by h-bonds
denaturation of protein (2 factors)
pH and temp (breaks weak h-bonds)
conjugated protein
(definition + example)
contains non-protein components (metal ions, carbohydrates)
ex. haemoglobin
non-conjugated proteins
contains only polypeptide subunits
ex. insulin, collagen
alpha-neurotoxins
polypeptide
- 60-75 amino acids
- snake venom
- targets nervous system
glucagon
polypeptide
- hormone
- 29 amino acid residues
- regulates blood sugar lvls
- secreted from pancreas
myoglobin
polypeptide
- oxygen binding protein
- 153 amino acids
- muscle tissues
- storage and release of oxygen to muscle fibres (used in physical activity)
R-groups (properties)
- hydrophobic/ hydrophilic
- hydrophobic are non-polar, repels water
- hydrophilic are polar, contains partial charges
basic (+)
acidic (-)
primary structure of proteins
refers to specific sequence of amino acids joined together to form polypeptide chains
- determines how the chain will fold (3D shape!)
secondary structure of proteins
refers to local folding patterns that occur within the polypeptide chain
- alpha helices
- beta-pleated sheets
alpha helices
- hydrogen bonds form between amine hydrogen of one amino acid and carboxyl oxygen of another amino acid 4 residues away in the sequence
- allows coiling
beta-pleated sheets
- sections of the polypeptide run parallel
- h-bonds form between adjacent strands
tertiary structure of proteins
further folding
(interactions + bonding between R groups)
H-bonds, ionic bonds, disulfide covalent bonds, hydrophobic interactions
hydrogen bonding (tertiary)
- between polar R groups
- stabilizes 3D shape (holds distant regions tgt)
ionic bonding (tertiary)
- R groups go through binding & dissociation of H+ ions to create charged R groups
disulfide covalent bonds (tertiary)
- forms between pairs of cysteine (contains sulfur)
hydrophobic interactions (tertiary)
- occur between non polar amino acids
- cannot interact with water, so they clump tgt in clusters in the inside of proteins
globular proteins (+ example)
- spherical, irregular folds
- soluble
- enzymes, transporters, regulators
ex. insulin, myoglobin
fibrous proteins (+ example)
- long, narrow
- stability for skin, tendons, bone
ex. collagen
quaternary structure of proteins
- arrangement/ interaction of 2 or more polypeptide chains
insulin
- hormone regulating amount of glucose in the body
- produced by pancreas
- binds to receptors of the cell, allowing glucose to enter)
- compact and GLOBULAR
- hydrophobic exterior, hydrophilic interior
collagen
- most abundant protein in the body (forms connective tissues + skin, cartilage)
- made of 3 polypeptide chains twisted in a triple helix
- fibrous protein
- contains glycine and proline residues
