Topic 7.5: Proteins Flashcards
(50 cards)
Explain Primary (1°) Structure of Protein (3)
The order / sequence of the amino acids of which the protein is composed
Formed by covalent peptide bonds between adjacent amino acids
Controls all subsequent levels of structure because it determines the nature of the interactions between R groups of different amino acids
Explain Secondary (2°) Structure of Protein (4)
The way the chains of amino acids fold or turn upon themselves
Held together by hydrogen bonds between non-adjacent amine (N-H) and carboxylic (C-O) groups
May form an alpha helix, a beta-pleated sheet or a random coil
Secondary structure provides a level of structural stability (due to H-bond formation)
Explain Tertiary (3°) Structure of Protein (3)
The way a polypeptide folds and coils to form a complex molecular shape (e.g. 3D shape)
Caused by interactions between R groups; including H-bonds, disulphide bridges, ionic bonds and hydrophilic / hydrophobic interactions
Tertiary structure may be important for the function of the enzyme (e.g. specificity of active site in enzymes)
Explain Quaternary (4°) Structure of Protein (4)
The interaction between multiple polypeptides or prosthetic groups that results in a single, larger, biologically active protein
A prosthetic group is an inorganic compound involved in protein structure or function (e.g. the heme group in haemoglobin)
A protein containing a prosthetic group is called a conjugated protein
Quaternary structure may be held together by a variety of bonds (similar to tertiary structure)
What is the difference between a fibrous protein and globular protein in respect to shape?
Fibrous: long and narrow
Globular: round/spherical
What is the difference between a fibrous protein and globular protein in respect to role?
Fibrous: structural (strength and support)
Globular: functional (catalytic, transport, etc)
What is the difference between a fibrous protein and globular protein in respect to solubility?
Fibrous: (generally) insoluble in water
Globular: (generally) soluble in water
What is the difference between a fibrous protein and globular protein in respect to sequence?
Fibrous: repetitive amino acid sequence
Globular: irregular amino acid sequence
What is the difference between a fibrous protein and globular protein in respect to stability?
Fibrous: less sensitive to changes in heat, pH, etc
Globular: more sensitive to changes in heat, pH, etc
What is the difference between a fibrous protein (6) and globular protein (4) in respect to examples?
Fibrous: collagen, myosin, fibrin, actin, keratin, and elastin
Globular: catalase, hemoglobin, insulin, immunoglobin
Is collagen a fibrous or globular protein?
fibrous
Is myosin a fibrous or globular protein?
fibrous
Is fibrin a fibrous or globular protein?
fibrous
Is actin a fibrous or globular protein?
fibrous
Is keratin a fibrous or globular protein?
fibrous
Is elastin a fibrous or globular protein?
fibrous
Is catalase a fibrous or globular protein?
globular
Is hemoglobin a fibrous or globular protein?
globular
Is insulin a fibrous or globular protein?
globular
Is immunoglobin a fibrous or globular protein?
globular
Explain the significance of polar and non-polar amino acids (4)
Polar amino acids have hydrophilic R groups, whereas non-polar amino acids have hydrophobic R groups
For water soluble proteins, non-polar amino acids tend to be found in the centre of the protein (stabilising structure) while polar amino acids are found on the surface (capable of interacting with water molecules)
For membrane-bound proteins, non-polar amino acids tend to be localised on the surface in contact with the membrane, while polar amino acids line interior pores (to create hydrophilic channels)
For enzymes, the active site specifically depends on the location and distribution of polar and non-polar amino acids as hydrophobic and hydrophilic interactions can play a role in substrate binding to the active site
What are the six functions of proteins?
structure, hormones, immunity, transport, movement, and enzymes
What is the role of structure proteins?
Support for body tissue
What is the role of hormone proteins?
Regulation of blood glucose
