2.4 Syllabus
u1. Amino Acids are linked together by condensation to form polypeptides.
Polypeptides:
-Chains of amino acids that are made by linking together amino acids by condensation (anabolism) reaction
-Condensation reaction involves amine group (-NH2) of one amino acid and carboxyl group (-COOH) of another. Water eliminated in condensation reactions and new bond formed between two amino acids which is peptide bond:
-Amino acids can be covalently joined together in a condensation reaction to form a dipeptide and water
-Polypeptide chains can be broken down via hydrolysis reactions, which requires water to reverse the process
-Chains of amino acids that are made by linking together amino acids by condensation (anabolism) reaction
- Happens on ribosomes by process called translation
-Condensation reaction involves amine group (-NH2) of one amino acid and carboxyl group (-COOH) of another. Water eliminated in condensation reactions and new bond formed between two amino acids which is peptide bond:
-Amino acids can be covalently joined together in a condensation reaction to form a dipeptide and water
-Polypeptide chains can be broken down via hydrolysis reactions, which requires water to reverse the process
u2. There are 20 different amino acids in polypeptides synthesized on ribosomes.
-R group that gives variation to amino acids.
-Amine group and carboxyl group used up in forming peptide bond
-Amine group and carboxyl group used up in forming peptide bond
U3. Amino Acids can be linked together in any sequence giving a huge range of possible polypeptides.
-Ribosomes link amino acids together one at a time, until a polypeptide is fully formed.
→ Ribosomes can make peptide bonds between any pair of amino acids so any sequence of amino acids is possible
→ Ribosomes can make peptide bonds between any pair of amino acids so any sequence of amino acids is possible
U4. The amino acid sequence of polypeptides is coded for by genes.
-Amino acid sequence of each poly peptide is stored in a coded form in the base sequence of a gene.
-Some genes have other roles, but most genes in a cell store the amino acid sequence of polypeptide.
→Use genetic code to do this
-Three bases of gene are needed to code for each amino acid in polypeptide
- Ribosomes are the site of polypeptide synthesis, but ribosomes need a template – the messenger RNA, which, in turn, is translated by transfer RNA molecules which, in turn, carry specific amino acids.
-Some genes have other roles, but most genes in a cell store the amino acid sequence of polypeptide.
→Use genetic code to do this
-Three bases of gene are needed to code for each amino acid in polypeptide
- Ribosomes are the site of polypeptide synthesis, but ribosomes need a template – the messenger RNA, which, in turn, is translated by transfer RNA molecules which, in turn, carry specific amino acids.
U5. A protein may consist of a single polypeptide or more than one polypeptide linked together.
-Some proteins are single polypeptides , other two or three more.
1. Integrin: Membrane protein with two polypeptides making connections between structures inside and outside the cell
2. Collagen: Consists of three long polypeptides wound together to form a rope-like molecule
3. Hemoglobin: Four polypeptides with associated non-polypeptide structures and transport protein in red blood cells.
1. Integrin: Membrane protein with two polypeptides making connections between structures inside and outside the cell
2. Collagen: Consists of three long polypeptides wound together to form a rope-like molecule
3. Hemoglobin: Four polypeptides with associated non-polypeptide structures and transport protein in red blood cells.
U6. The amino acid sequence determines the three-dimensional conformation of a protein.
-Conformation of protein is its three- dimensional structure.
Conformation determined by amino acid sequence of protein and its constituent polypeptides
-In globular proteins, polypeptides gradually fold up as they are made, to develop the final conformation. They are soluble in water, and there are hydrophilic R groups on the outside of molecule & there are usually hydrophobic groups on the inside. There are regions with hydrophobic R groups on the outside of the molecule, which are attracted to the hydrophobic centre of the membrane.
-In fibrous proteins the amino acid sequence prevents folding up and ensures that the chain of amino acids remains in an elongated form.
Conformation determined by amino acid sequence of protein and its constituent polypeptides
-In globular proteins, polypeptides gradually fold up as they are made, to develop the final conformation. They are soluble in water, and there are hydrophilic R groups on the outside of molecule & there are usually hydrophobic groups on the inside. There are regions with hydrophobic R groups on the outside of the molecule, which are attracted to the hydrophobic centre of the membrane.
-In fibrous proteins the amino acid sequence prevents folding up and ensures that the chain of amino acids remains in an elongated form.
U7. Living organisms synthesize many different proteins with a wide range of functions.
Function of Proteins:
- Structural: Collagen
- Movement: Actin
- Transport: Hemoglobin
- Hormones: Insulin
- Defense: Antibodies/Immunoglobins
- Synthesis: DNA polymerase
- Hormonal communication: Insulin
- Food stores: casein in milk
- Pigments: Opsin
U8. Every individual has a unique proteome.
Proteome: Gene that code for several proteins
-While the genetic make up of an organism is the same in all cells, each tissue or individual cell shows variable gene expression and thus different proteins are created
-While the genetic make up of an organism is the same in all cells, each tissue or individual cell shows variable gene expression and thus different proteins are created
A2. Denaturation of proteins by heat or by deviation of pH from the optimum.
-Denaturation: 3 dimensional structure of protein is altered.