Proteins Flashcards
What are proteins comprised of?
Proteins are comprised of long chains of recurring monomers called amino acids
What is the cause for amino acid diversity?
The R-group of amino acids is variable, causing 20 different natural variations within amino acids.
What are polypeptides?
Polypeptides are chains of amino acids that are made by linking together amino acids by condensation reactions
What are peptide bonds?
The bond formed between the amino group of one amino acid and the carboxyl group of the adjacent is a peptide bond.
What is the cause for polypeptide diversity?
Amino acids can be linked together in any sequence giving a huge range of possible polypeptides.
- If we consider a polypeptide with 100 amino acids, the number of possible sequence is 20^100
- However, only particular sequences are made in very large quantities because they have useful properties
What is the significance of genes in the formation of polypeptides?
- The amino acid sequence of a polypeptide is coded for by a gene
- The sequence of bases in the DNA of the gene determines the sequence of amino acids in the polypeptide
What is the primary structure of amino acids?
The linear sequence of amino acids. Formed through peptide bonds.
What is the secondary structure of amino acids?
The stable configuration of amino acid sequences. Caused by hydrogen bonds between O and H in the peptide bond.
Two types:
1. Alpha helicles (spiral in shape) - most common
2. Beta-pleated sheets (directionally-oriented)
What is the tertiary structure of amino acids?
The overall three-dimensional configuration of the protein. Will have bonds such as disulphide bonds, ionic interactions, polar associations.
What is the quaternary structure of amino acids?
The quaternary structure describes the way in which the different subunits are packed together to form the overall structure of the protein
Example:
- Lysosome consists of 1 polypeptide
- Integrin consists of 2 polypeptides
- Collagen consists of 3 polypeptides
- Haemoglobin consists of 4 Polypeptides
What are the 7 main functions of proteins (with examples)?
- Enzymes
- Rubsico catalyses the reaction that fixes CO2 from
the atmosphere
- Rubsico catalyses the reaction that fixes CO2 from
- Antibodies & Clotting Factor
- Immunoglobulins are antibodies
- Immune system produces a variety of
immunoglobulins, each with a different binding site - Plasma proteins act as clotting factors
- Hormones
- Insulin, Glucagon, LH, FSH
- Structural components
- Collagen forms a mesh of fibres in skin and blood
vessels to prevent tearing, and in bones to prevent
fractures - Spider silk is used make webs; stronger than kevlar
and steel (resisting breakage)
- Collagen forms a mesh of fibres in skin and blood
- Movement
- Actin and myosin are involved in the contraction of
muscles
- Actin and myosin are involved in the contraction of
- Transport
- Hemoglobin is responsible for transporting oxygen
- Sensitivity
- Rhodopsin is the membrane protein of rod cells
that absorb light
- Rhodopsin is the membrane protein of rod cells
What is the proteome?
A proteome is all of the proteins produced by a cell, a tissue, or an organism
What is the difference between genome and proteome?
The genome (all of the genes of an organism) of an organisms is fixed, while the proteome is variable. This is because the proteins made in an organism (even in a single cell) vary over time depending on the cell’s activity.
Why are proteomes unique?
- Differences in activity
2. Differences in the amino acid sequences (due to differences in genes)
What is denaturation?
Denaturation is a structural change in a protein that results in the loss of its biological properties, as the tertiary structure of a protein (the way it folds) determines its function
