Chapter 5.3-5.4 - Proteins Flashcards
7 functions of protein
- Enzymes
- Structure
- Movement
- Signalling
- Transport
- Regulation
- Defence
Enzymatic proteins regulate metabolism by acting as:
Catalysts
Catalyst
Chemical agents that selectively speed up chemical reactions without being consumed by the reaction
Building blocks of proteins are:
Monomers: amino acids
Polymers: peptides, polypeptides
What shape do proteins take
A unique 3D structure
Proteins are constructed from:
The same set of 20 amino acids, linked in unbranched polymers
Peptide Bond
The covalent bond between amino acids formed by a dehydration reaction (occurs on the ribosome)
Polypeptide
A polymer of amino acids
Protein
A biologically functional molecule made up of one or more polypeptides, each coiled and folded into a specific 3D structure important for its function
Amino acids differ in their:
R Groups! These determine properties.
Some R groups are hydrophobic (nonpolar)
Some R groups are hydrophilic (polar)
Some R groups carry charge (+ or -) at cellular pH
Amino Acid
An organic molecule with both an amino group and a carboxyl Group. They are the building blocks of protein.
*see diagram in notes
Amino Acid Diagrams and Groups
SEE TEXTBOOK P. 85
Protein functions result from:
Exquisite Molecular Order
Four Levels of Superimposed Structure
- Primary
- Secondary
- Tertiary
- Quaternary
Primary Structure (3)
- Linear chain of amino acids
- Unravelled depiction of amino acids
- Ex: transthyretin in textbook!!!!
Secondary Structure (4)
- Hydrogen bonds between atoms of backbone
- Within the backbone, the oxygen atoms have a partial negative charge, while the hydrogen atoms attached to the nitrogen’s have a partial positive charge.
- Can be depicted in ribbon models of protein
- Toxic proteins may undergo helix to sheet transitions
Tertiary Structure (4)
- Polypeptides fold into a specific shape determined by primary structure
- Interactions among R Groups of amino acids stabilizes the tertiary structure of a protein
- Covalent Bonds called disulphide bridges may further reinforce the shape of a protein
- SEE TEXTBOOK
Quaternary Structure (4)
- Two or more polypeptides (subunits) May interact (aggregate)
- Globular Protein; e.g, hemoglobin (textbook p. 89)
- Non-covalent interactions between polypeptides
- Can often be predicted from primary structure
Methods to determine protein structure (2)
- X-Ray Crystallography
2. Nuclear Magnetic Resonance Spectroscopy
Protein Structure Depends on (3)
- Temperature
- pH
- Salt Concentration
What could happen if temp, pH or salt concentration are altered?
Denaturation
Denaturation
When the weak chemical bonds and interactions within a protein are destroyed, causing the protein to unravel and lose its shape
Renaturation
Reversal of denaturation
Chaperonins
Protein molecules that assist the proper folding of other proteins
Importance of Protein Structure (3)
- Each protein folds into a unique shape (tertiary structure) that determines its specific function
- The shape of a protein is determined by its primary structure
- The side chains of amino acids determine the interactions that occur within and between proteins
Neurodegenerative diseases attributed to protein misfolding: (4)
- Alzheimer’s
- Huntington’s disease
- Parkinson’s
- Prion
Why can misfolded proteins cause disease?
Due to the production and accumulation of misfolding proteins that aggregate and damaged nerves
CTE or Chronic Traumatic Encephalopathy:
A progressive degenerative brain disease in individuals with a history of repetitive brain injury (common in contact sports).
Associated with memory loss, aggression, impaired judgement etc.
Diagnosis of CTE:
Hallmark is accumulation of an abnormal variant of tau protein
Normal Function of Tau Protein (2)
- Binds to microtubules (a component of cytoskeleton) in axons of neurons
- Stabilizes and promotes polymerization of microtubules in axons
Normal Structure of Tau Protein (3)
- Globular, naturally disordered, soluble protein
- Low content of secondary structure
- Folds into stable structure when bound to microtubules via repeat regions in C terminus
Protein Phosphorylation (2)
- Phosphorylated amino acids are usually theronine, serine and tyrosine.
- Site of phosphorylation is influenced by surrounding amino acids diagrams in notes
Hyperphosphorylated Tau
Adopts a beta sheet conformational and changes secondary and tertiary structure of ptau
Ptau
Improperly folded or damaged Tau. See drawings in notes!
Severity of CTE in relation to PTau
Severity is determined by measuring ptau accumulation in brain tissue sections. CTE is classified as either mild or severe based on amount of ptau deposition
Oligomerization of Ptau
- Misfolding of ptau results in formation of aggregates (oligomers) that are toxic to cell.
Ptau Fibrils (3)
- Beta sheets are stacked in tau oligomers
- Oligomers polymerize to form fibrils
- Fibrils have a high tensile strength
*see drawings in notes!
Head injury does what to the brain
It causes it to oscillate in skull
