Proteins Flashcards
What is the structure of an amino acid
R group Amine Group (NH2) Carboxyl Group (COOH)
How are peptide bonds formed
X-COOH + NH2-Y -> X-C(O)N(H)-Y + H2O
What is the start and end of the polypeptide
Start = N-Terminus End = C-Terminus
What is an example of a protein with one polypeptide chain
Myoglobin
What is an example of a protein with 2 polypeptide chains
A and B chains of insulin
What is an example of a protein with 3 polypeptide chians
Collagen Helix of tendons and bones
What is an example of a protein with 4 polypeptide chains
the two alpha and beta subunits of haemoglobin
what are the 2 classes of R groups
Hydrophilic and Hydrophobic
What are the 3 divisions of the hydrophilic class of R groups
Acidic
Neutral
Basic
Which 3 groups make up the six hydrophilic side chains
=O
- OH
- NH
Which 1 group makes up the 2 acidic side chains
X-COO-
Which 1 group makes up the three basic side chains
-NH
What is the primary structure
order of the covalent polypeptide sequence
Location of Disulphide bridges, prosthetic groups, glycosylation
What is secondary structure
3-D Arrangement of ONLY the polypeptide main chain, stabilised by only hydrogen bond
What is the tertiary structure
3-D arrangement of amino acid side chains with each other and the main chain
Stabilised by hydrogen bonds, salt bridges, hydrophobic interactions, disulphide bridges
What is the quaternary structure
3-D assembly of individual protein subunits for a protein made from multiple polypeptide chains
What are the two main types of secondary structure
Alpha Helix
Beta Pleated Sheet
What is the Alpha Helix
The helical arrangement of a single protein maintain that repeats itself approximately every fourth residue
What are the 6 features of the Alpha Helix
Rond-like with the R groups outside
All C=O and N-H maintain groups bonded by hydrogen bonds
All H-bonds are parallel to the helix
N-H forms H-bond to C=O which is 4 residues forward
3.6 residues per turn
Always right-handed for reason of the L-amino acids
What are the 5 features of the Beta Pleated Sheet
Both Parallel and antiparallel sheets
All H-bonds are between separate main chains and perpendicular to the direction of the main chain
Extended main chain with the R-Groups alternating up and down
All the C=O and N-H groups are H-bonded
Beta Turns
What is an antiparallel beta sheet
N-Termini are at opposite ends
What are parallel beta sheet
N-Termini are at the same end
What are the 2 features of a beta turn
Sharp reversal in the direction of polypeptide chain over just 4 AA residues
Sterically demanding, so a Gly residue is often located in middle of the turn
What are the 5 features of globular proteins
Compact
Soluble in water
2ry structure is made of both alpha helices, beta sheets, and loop structures
4ry structure held together by non-covalent bonds
Functions in all aspects of metabolism
What are the 5 features of fibrous proteins
Extended structure Insoluble in water 2ry structure made on one type only 4ry structure held by covalent bridges Functions in structure of the body or cell
4 general examples of globular proteins
Enzymes
Transport
Immune Response
Hormones
6 general examples of fibrous protein function
Tendons Bones Muscle Hair Ligaments Skin
Name 3 specific examples of fibrous proteins
Alpha-Keratin
Elastin
Collagen
How is Alpha-Keratin organised
the subunit contains two alpha-helices, cross-linked by disulphide bridges
Assembled to form fibres
What 3 things is alpha keratin used for
Hair
Nails
Outer layer of skin
How is Elastin organised
Cross-linked subunits connected by covalent bonds
What 4 things is Elastin used for
Connective tissue
Large arteries
Ligaments
Lung Wall
How is collagen organised
Triple Helix secondary structure
Assembly of tropocollagen into fibres
Chemical cross linkage
What 5 things is collagen used used
Connective tissue Skin Tendons Cartilage Bones
Give 3 examples of a globular protein
Haemoglobin
IgG
Fibrinogen
