Proteins Flashcards
Define Protein
Macromolecule of AA subunits arranged in a particular structure which enables it to carry out a specific function in a particular context
What can proteins be in terms of their role in the body/biological processes
Structural (actin within cell or keratin in skin) or functional (catalytic function of enzymes or antibodies in immune defence)
What is DNA
Blueprint for proteins:
* tells cells how to make messenger RNA (mRNA) transcription
* mRNA used by cell as code to make AA chains translation
* Chains form protiens
What can combinations of 3 bases do?
code for AA or stop instruction
Outline the basic structure of an AA
Amine group (NH2), Carboxylic acid group (COOH), R group (vairable side chain), H on centre carbon
What are AA
Chiral - 4 diff groups on central Carbon (except glycine)
How does the acid-base environment affect AA?
Changes in pH affect Protien structure.
* Acid = proton donor
* Base = proton acceptor
Low pH: COOH, NH3+
Neutral pH: NH3+ COO-
High pH: NH2, COO-
Name and describe all the major AA classes
- Aliphatic: R group of hydrocarbon chains - hydrophobic and non-polar
- Aromatic: hydrocarbon ring
- Sulphur-containing: S allows for di-sulphide brides to occur between AA
- Basic
- Acidic
- Polar - carry charge at end of R-group (e.g. hydroxly group)
- Other: proline (hard to break so in tissues requiring strength)
Define primary AA structure
Sequence in which AA monomers are bonded together to form a polypeptide chain - massive variability in protein structure
What reaction occurs in the formation of primary structure
Dehydration reaction: 2 AA combine forming a peptide/amide bond and release water
What are 2 AA monomers called
dipeptide - more and more = polypeptide
What is secondary structure
3D spatial arrangement of AA located near each other in polypeptide chain. Relies on H-bonding between amino hyrdogen of one AA and carboxyl oxygen of another AA in same chain.
Depending on primary structure, protien can configure as an alpha helix or beta pleated sheet
What is tertiary structure
Functional groups of R chains of AA in the polypeptide chain interact with one another
What forces are all involved in tertiary structure
Van der Waals, ionic, hydrogen, disulphide and hydrophobic interactions
What level can functional proteins exist at?
A tertiary structure
How does hydrophobicity/or polar R groups influence protein function
Confers fucntion to some protiens (e.g. membrane proteins or surface proteins)
Explain quaternary protien structure
Several polypeptides intercat with one another to form the quaternary structure (e.g. heamoglobin)
How can denaturation occur?
protein’s chemical bonds are disrupted or destroyed) within secondary or tertiary structure - temp/permanent loss of biological functionality
Rarely stong enough to break primary structure which remains same after denaturation
What is protein structure dependent upon
DNA sequence that codes for AA monomers
What does the way AA monomers interact with each other dictate?
The final structure and function of the protein
What is lost when proteins become denatured
Structure and function is lost
Give the 8 main functions of proteins
- Structural - support for connecting tissues
- Enzymatic proteins - e.g. digestion
- Receptor proteins - G-proteins coupled receptors
- Hormonl protiens - coordinate metabolic function
- Transport protiens - heamoglobin or Na/K pump
- Storage proteins
- Defensive protiens - protection (immunoglobulin)
- Contractile proteins - movement (actin/myosin)
What can post-translational modification/co-translational modification give?
Conjugated proteins
Give 3 examples of conjugated proteins
- Glycoprotiens
- Lipoprotiens
- Metalloprotiens
What are glycoprotiens and how are they formed
- Proteins with more than 1 carbohydrate molecule(s) covalently attached
- Co-translational or post-translational modification where oligosaccharide chains are attached to a protein
WHat are the effects of glycosylation
Alters physical properties:
1. Inc stability
2. Altered solubility
3. Cell signalling
4. Orientation
What are lipoproteins
Proteins combined with lipids
Where can lipoproteins be found and what do they do?
Found in cell membranes and transport hydrophoibic (lipid) molecules (e.g. cholestrolal transport in blood)
What are metalloprotiens and what are their function
- Protien with a metal ion within its structure (co-factors)
- Various functions (e.g. enxymatic, signal transduction, storage and transport) - heamoglobin
What are globular proteins (structure)
tprotiens wih 3D molecular structure
Give some examples of glubular protien functionn
- Storage
- Enzymes
- Hormones
- Transporters
- Structural
What are fibrous protiens (structure)
Elongated protiens with a sheet-like structure
Give some functions of fibrous protiens
- Muscle fibres
- Connective tissue
What can mutations in the DNA sequence coding for a protien lead to?
Disease
What properties may the possetion of quaternary structure confer upon a protein
Post-t modification can give conjugated proteins
* Glycoprotiens
* Lipoprotiens
* Metalloproteines
renaturation
the process in which the complementary strands are reformed by the formation of hydrogen bonds
Heamoglobin
iron-containing oxygen-transport metalloprotein in red blood cells. Quaternary protein. Hemoglobin in blood carries oxygen from the respiratory organs to the rest of the body.
name some other proteins
elastins, collagens, keratins
