B1.2 (Proteins) Flashcards
Proteins
complex macromolecules composed of one or more chains of aminoacids
Amino acids
monomers that make up proetins
Components of a protein
- Amino Group
- Side chain (alpha carbon & R)
- Carboxyl Group
Formation of a peptide Bond
-COOH + -NH2 –> OC-NH + H20
Definition
Non Essential AA
can be produced by body
Definition
Essentials AA
cannot be produced by body
Examples
9 Essential AA
Histidine, Isoleucine, Lysine, leucine, Methionine, Phenylalamine, Threonine, Tryptophan and Vanine
Sources of protein
beans, lentils, meat, nuts, seeds
Uses of proteins
- growth
- repair
- catalyst
- structure (collagen)
- transport (across membrane)
- immunity
- bidning sites for neurotransmitters
- homeostasis (insulin)
Transcription
Dna -> mRna
Translation
mRna -> sequence of AA
Amount of Codons
64 Codons code for 20 AA
Codons
Three adjacent nucleotides in DNA or mRNA that code for a particular AA
Degenerate
Refers to the redundancy of genetic code (multiple codons code for the same protein)
Silent Mutations
Change in DNA sequence that does not result in the change of AA sequence of a protein
Nonesense mutation
A change in DNA sequence in which a stop codon is produced, ending the protein synthesis
Missense Mutation
Change in DNA arrengement as one nucleotide base is swapped causing a diferent AA sequnece
Frameshift Mutation
A change in DNA sequnece in which a nucletide is added or deleted resulting in triplet codons being read incorrectly
Polypeptides
A chain of AA which is linked together by peptide bonds
Lysozyme
enzyme that functions as a natural defense against bacterial infections by breaking down bacterial walls
Where is Lysozyme found
Salive and Tears
Alpha Neurotoxin
Binds to and inhibits receptors causing neuro toxic effects like paralysis and death
where is alpha neurotoxin found
snake venom
Glucagon
hormone which regulates blood sugar (low -> high)
where is glucagon found
secreted from pancrease and released by the liver
Myoglobin
oxygen binding protein which facilitates the storage and release of O2 to muscle fibres
Denaturation
process in which the structure of a protein is irreversibly altered causing it to lose its function
How PH affects protein structure
The change in PH affects the charge on the protein molecule altering its activity so therefore its shape and solubility
What are the determinents of a proteins structure
the R group
How Temperature affects protein structure
The change in temperature breaks the hydrogen bonds holding the structure together meaning that the protein will unfold and lose its function
Protein - Definition
Primary structure
specific sequnece of AA that join to form polypeptide bonds
Protein - Definition
Quatenary Structure
arrangement & interaction of two or more polypeptide chains to form a functional protein
Protein - Definition
Secondary Structure
local folding patterns that occur within a polypeptide chain
ex:
Protein - Definition
Tertiary Structure
gives rise to the overall three dimensional shape of the protein
ex: integral proteins embedded in membranes: Rhodopsin in retinal cells which absorbs light
Examples
Examples of Fibrous Protein
- Keratin
- Collagen
Globular Proteins
- spherical
- irregular folds
- water soluble
- complex
Fibrous Proteins
- narrow
- elongated
- water insoluble
- repeating structures
Examples
Examples of Globular Protein
- Pepsin
- Haemoglobin
- Insulin
- Myoglobin
Protein Structure
Hydrogen bonds
- form between R Groups
- hold distant regions of polypeptide chains together
- maintains functional integrity
Protein Structure
Ionic bonds
- R group undergo binding/dissasociation of hydrogen ions
- R groups interact with oppositely charged atoms in other molecules
Types of secondary protein folding patterns
Alpha helices and beta pleated sheets
Protein Structure
Disulfide Bridges
- between cysteine AA residues which contain sulfur atoms
- form covalent bonds
Protein Structure
Hydrophobic interactions
- between non polar AA
- as non polar dont interact with water = clump together
- create hydrophobic clusters
Alpha helices
- H-Bond forms between amine group & -COOH
- Every 4 Bond together
- allows it to coil
important to remeber about hydrogen bonds
Hydrogen bonds are very weak intermolecular forces but they can be strong if they occur collectively
Beta pleated sheets
- H bonds form between adjacent strands (parallel)
- pleated like structure
- flat surface
conjugated proteins
globular proteins with a prospthetic group
ex: Haemoglobin
prosthetic group
non polypeptide group that is required for biological functioning on the protein
non conjugated proteins
only polypeptide subunits
ex: collagen (3) or Insulin (2)
Uses of globular proteins
enzymes, transport, regulators
fibrous proteins
support & stability to cells
ex; bones, tissue, tendons
Relating to protein stucture
Insulin
- globular
- binds to specific receptor cells to allow glucose to enter
- hydrphilic exterior & phobic interior which allows interaction with water in blood
- compact
Collagen
- fibrous
- 2 polypeptide chains
- hydroxyproline residues allows it to twist due to van-der-waals*
Van der Waals forces
weak intermolecular forces between atoms/molecules caused by temporary imbalance of electrons
quatenary protein examples
haemoglobin & rubisco (enzyme)
property of globular membrane protein
hydrophobic outside
property of globular water soluble protein
hydrophilic outside
Amount of AA combinations possible to form polypeptides
20 to the power of 20
Glycoproteins
Proteins with one or more carbohydrates attached to them
Amino acid polarity in membrane proteins
- polar= soluble, form stable interactions in water, strongly hydrophillic = form hydrophillic channels/pores
- non polar = are soluble in lipid layer, hydrophobic
