B1.2_Proteins

B1.2 Proteins

Form and function - Molecules

• What is the relationship between amino acid sequence and the diversity in form and function of proteins?
• How are protein molecules affected by their chemical and physical environments?

B1.2.1—Generalized structure of an amino acid

Proteins: biomolecules comprised of amino acids joined together by peptide bonds.

Research skills – Using search engines and libraries effectively

B1.2.1—Generalized structure of an amino acid

Tryptophan

B1.2.3—Dietary requirements for amino acids

Essential amino acids: cannot be synthesized, must be taken through the diet

Conditionally essential:

• Tyrosine can be synthesised from phenylalanine.
• Arginine cannot be synthesised by infants.

B1.2.3—Dietary requirements for amino acids

Diet sources of essential amino acids

Vegan diets require attention to ensure essential amino acids are consumed.

https://www.mdpi.com/1422-0067/23/19/11281

B1.2.3—Dietary requirements for amino acids

Non-essential amino acids: are synthesized from other amino acids

B1.2.2—Condensation reactions forming dipeptides and longer chains of amino acids

Draw your peptide name!

B1.2.4—Infinite variety of possible peptide chains

There are infinite possibilities of polypeptides because:

• 20 different amino acids are coded by the genetic code
• polypeptides can be of any length (up to thousands)
• amino acids can be in any order

Insulin

B1.2.5—Effect of pH and temperature on protein structure

Interactions between amino acid side chains determine the structure of the protein

Protein structure determines function

B1.2.5—Effect of pH and temperature on protein structure

B1.2.5—Effect of pH and temperature on protein structure

pH = -log [H+]

B1.2.5—Effect of pH and temperature on protein structure

B1.2.6—Chemical diversity in the R-groups of amino acids as a basis for the immense diversity in protein form and function

R groups

Hydrophobic

Hydrophilic

Charged

Polar

Positive

Negative

Determine the structure and properties of proteins

B1.2.6—Chemical diversity in the R-groups of amino acids as a basis for the immense diversity in protein form and function

Protein structure determines function

Interactions between amino acid side chains determine the structure of the protein

B1.2.7—Impact of primary structure on the conformation of proteins

Primary structure:

• Secuence of amino acids linked throug covalent bonds
• Determines the subsequent conformation

B1.2.7—Impact of primary structure on the conformation of proteins

Primary structure:

• Secuence of amino acids linked through covalent bonds
• Determines the subsequent conformation -> allows us to predict protein structures

Click on the image to check the structure of insulin

B1.2.8—Pleating and coiling of secondary structure of proteins

Secondary structure is due to hydrogen bonding between the amine and carboxyl groups of non-adjacent amino acids

Alpha helix Beta - pleated sheet

B1.2.9—Dependence of tertiary structure on hydrogen bonds, ionic bonds, disulfide covalent bonds and hydrophobic interactions

B1.2.9—Dependence of tertiary structure on hydrogen bonds, ionic bonds, disulfide covalent bonds and hydrophobic interactions

Bonds between R groups of aminoacids in tertiary structure:

• Hydrogen bonds

• Ionic bonds: between positively or negatively charged amine and carboxyl groups

• Disulfide bonds: between cysteins

• Hydrophobic interactions

B1.2.10—Effect of polar and non-polar amino acids on tertiary structure of proteins

B1.2.10—Effect of polar and non-polar amino acids on tertiary structure of proteins

Integral protein

B1.2.11—Quaternary structure of non-conjugated and conjugated proteins

Quaternary structure: bonds between R groups of different peptide chains

Insulin Collagen

B1.2.11—Quaternary structure of non-conjugated and conjugated proteins

Quaternary structure: bonds between R groups of different peptide chains

non- conjugated Conjugated (haemoglobin)

B1.2.11—Quaternary structure of non-conjugated and conjugated proteins

NOS: Technology allows imaging of structures that would be impossible to observe with the unaided senses. For example, cryogenic electron microscopy has allowed imaging of single-protein molecules and their interactions with other molecules.

B1.2.12—Relationship of form and function in globular and fibrous proteins

Linking questions

• How do abiotic factors influence the form of molecules
• What is the relationship between the genome and the proteome of an organism?