the 1st unicram (4) Flashcards
What are Amphoteric properties?
A substance which can act as an acid or a base
Proton donor or proton acceptor
Do amino acids have amphoteric properties?
Yes
How are peptide bonds formed/broken?
Formed by condensation, broken by hydrolysis
Needs ATP
What is primary structure?
- Order or sequence of the polypeptide chain, joined by peptide bonds
- Determined by the codons on DNA
- Determins the tertiary structure of the polypeptide
What is secondary structure?
- The primary structure folds back on itself
- Hydrogen bonds form between C=O and N-H of primary structure
- ALPHA HELIX OR BETA PLEATED SHEET
- R groups project out from the alpha helix
- Beta pleated folds backwards and forwards in pleats with the H bonds forming between C=O and N-H of adjacent folds
- R group project alternately above and below the plane of the sheet
The Alpha Helix
Right - hand coil, R groups project out from helix
Polar residues face outwards toward liquid and hydrophobic residues face protein interior
Kinked
The Beta Pleated sheet
3 Types:
parallel beta sheet - all bonded strands have the same N to C direction. Seperated by long sequence stretches
Antiparallel beta sheet - Beta strands run in alternating directions, can be formed between regions that are close on the primary sequence
Mixed beta sheet - A mixture of parallel and antiparallel hydrogen bonding
When does a turn occur for beta pleated sheets?
When protein chain needs to change direction to connect two other elements of secondary structure
What are random coils?
Regions of the protein chain that don’t form a regular secondary structure or have a regular hydrogen bonding pattern
Found in Terminal arms and loops
Tertiary Structure?
Secondary structure folds back on itself to form a 3D globular structure
Determined by nature of R groups
Bonds between R groups are Hydrogen, Ionic, Disulphide
(Weakest to strongest) - Also weak molecular forces and hydrophobic,philic interactions
What are chaperone proteins?
Chaperone proteins assist in ensuring the tertiary correctly folds to ensure the correct structure is formed
Prevents hydrophobic patches of amino acids from aggregating into non-functional aggregates
Conjugated proteins
Proteins that contian a non-protein prosphetic group (attached by covalent bonds)
Protein is called the apoprotein
Quaternary proteins ?
Consist of more than one polypeptide chain
Joined by bonds between R groups
Either fibrous or globular
Collagen?
Organic phase of bones, teeth and most other connective tissues
Fibrous quaternary protein
Made of 3 amino acids repeated over and over, one of which is glycine
Glycine has H as the R group, makes it small and so pulls the helix in. Helices are joined by bonds between R groups
Haemoglobin?
Global heteromeric quanternary protein
Conjugated chromoprotein with heme groups
Hydrophobic interactions hold 4 subunits together
Hydrophilic interactions allow it to dissolve in water
Types of signal transduction?
Autocrine
Intracrine
Juxtracrine
Paracrine
Endocrine
Autocrine and Intracrine transduction?
Autocrine:
A cell secrets a chemical messenger out of the cell which binds to receptors on the same cell membrane. Activates effector on the same cell
Intracrine:
Chemical messenger is released within the cell and is not secreted out of the cell. Instead, a nuclear and cytosolic receptor
Juxtacrine and Paracrine transduction?
Juxtacrine:
Utilises gap-junction proteins to transport a chemical messenger across the cell membrane of an adjacent cell to cause an effect on that adjacent cell
Paracrine:
Chemical messenger is released from a cell and is allowed to diffuse into the local tissue.
Allows it to target a series of neighbouring cells for effect
Endocrine transduction?
Release of cellular messengers (hormones) from a cell and is transported to the tissue/cell of activity via the bloodstream. This requires transportation into and out of the bloodstream
Cell signalling: Dopamine?
Neuotransmitter molecule, promotes reward and pleasure responses to beneficial activities
Binds to several different types of dopamine receptors, each has a unique effect
Release of dopamine?
Synthesised within the cytol of neurons from L-DOPA and packaged into synaptic vesicles
Dopamine vesicles are released from the first neuron by an action potential activated exocytosis
Binding of dopamine?
Dopamine is released into the intrasynaptic gap
Dopamine can then bind to specific dopamine activated receptors on both sides of the synaptic gap
While binding to receptors on the opposite neuron, dopamine acts as a paracrine signalling molecule
While binding to receptors on the neuron which released it, dopamine acts as an autocrine signalling molecule
2 types of Dopamine binding receptors:
Type 1 and 2
1: Increase production of cAMP which acts as an intracellular secondary messenger, passing on the message to new effectors
2: Reduce or inhibit cAMP production, reducing the secondary messenger effects, halting the message to new effectors
Process of Dopamine binding?
1) Dopamine is synthesised from L-DOPA
2) Dopamine is packaged into the vesicle awaiting an action potential
3) Action potential fires, releases the dopamine via exocytosis
4) Dopamine binding to type 1 receptor activates cAMP continuing the message
5) Dopamine binds to a type 2 receptor deactivates cAMP, halting the message
6) Dopamine binding to an autocrine type 2 receptor prevents dopamine production
Motor proteins?
- Set of molecular motors which move molecules along the cytoskeleton of cells
- Utilises the hydrolysis of ATP, convert chemical potential energy into movement
- Kinesins and dynein are two motor proteins, transport molecules and structures along the structural microtubule structures to the periphery and interior of the cell respectively
