7.5 Proteins Flashcards
Outline primary structure in proteins
The linear 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.
Outline secondary structure in proteins
The 2D shape of the polypeptide chain. Two common shapes are ‘α helix’ (A coil) and ‘β sheets’ (Pleated sheets which are mores stressed that alpha helices)
Outline tertiary structure in proteins
3D shape of the protein. The way a polypeptide folds and coils to form a complex molecular shape. Important for the function of the enzyme (e.g. specificity of active site in enzymes). Caused by interactions between R groups.
State the four types of bonding involved in the tertiary structure of a protein
H-bonds
Disulphide bridges
Ionic bonds
Hydrophilic / hydrophobic interactions
Outline quaternary structure in proteins
The linking of two or more polypeptides to form a single protein. Sometimes contain a non-polypeptide structure called a prosthetic group (conjugated protein).
Define conjugated protein
A protein containing a prosthetic group (non polypeptide structure)
Define prosthetic group
A non-polypeptide structure involved in protein structure or function. Proteins containing them are called conjugated proteins.
Contrast the shape of globular and fibrous proteins
Globular proteins are round in shape; fibrous proteins are long and narrow.
Contrast the role of globular and fibrous proteins
Globular proteins (generally) have a functional role; fibrous proteins (generally) have a structural role.
Contrast the solubility of globular and fibrous proteins
Globular proteins are (generally) soluble in water; fibrous proteins are (generally) insoluble.
Contrast the amino acid sequence in globular and fibrous proteins
Globular proteins have irregular sequences; fibrous proteins have repetitive sequences.
Contrast the sensitivity of globular and fibrous proteins
Globular proteins are more sensitive to changes in heat, pH; fibrous proteins are less sensitive.
State two fibrous proteins.
Collagen, Elastin, Keratin ect
State two globular proteins
Catalase, Lactase, ect
Describe polar amino acids
Hydrophilic R groups. Water soluble. Surface of globular proteins.
Describe non-polar amino acids
Hydrophobic R groups. Lipid soluble. Inside globular proteins. Stabilize the structure of water soluble proteins.
Outline significance of polar and non-polar amino acids in transport
Non-polar amino acids are lipid-soluble, and therefore can pass through the phospholipid bilayer. Polar amino acids, and other water soluble substances must be “carried”.
Outline significance of polar and non-polar amino acids in terms of the active site
Polar amino acids in the active site of an enzyme allow chemical interaction between the substrate and enzyme to form an activated complex. This transitional state allows the weakening of internal molecular structure and therefore the reduction of activation energy.
State six functions of proteins
Structure Hormones Immunity Transport Movement Enzymes
(SHIT ME)
Give an example of a structural protein
Keratin
Give an example of a hormone protein
Insulin
Give an example of an immunity protein
Antibodies
Give an example of a transport protein
Haemoglobin
Give an example of a movement protein
Actin
Give an example of an enzyme protein
Catalse
