Proteins Flashcards
What is the general structure of an amino acid?
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The R group defines an amino acid and represents a side chain from the central carbon atom, and can be anything from a simple hydrogen atom to a more complex ring structure. There are 20 different R-groups.
What reaction joins two amino acids together?
Condensation- water is formed and removed allowing for a bond to made.
What is the name of the bond that forms between 2 amino acids?
Peptide
How would multiple amino acids be bonded together?
What is the primary structure of proteins?
- it’s the specific sequence of amino acids in a polypeptide, held together by peptide bonds
- it is determined by the DNA code
- ALL proteins have a primary structure
What is the secondary structure of proteins?
- It’s a polypeptide that has the amino group and carboxyl group on either sides
- it’s a-helix / b-pleated structure is formed through weak hydrogen bonds between the amino and carboxyl groups
What is the tertiary structure of proteins?
-it’s the precise folding of the secondary structure into a more complex, globular 3D shape, held together by hydrogen, ionic and disulphides bonds and hydrophobic interactions.
Hydrogen bonds: polar R groups form bonds with other polar R groups
Disulphides bonds: amino acid cysteine contains a sulphur atom in its R group and so bonds with another cysteine’s sulphur atom.
Ionic bonds: positive and negative R group bond together
Hydrophobic interactions: Amino acids orient themselves towards centre of polypeptide to avoid water
What is the quaternary structure of proteins?
- proteins which consist of two or more polypeptide chains (subunits) which interact with each other and arrange themselves to form a larger protein complex
- structure is formed through the linkage of the polypeptide chains with each other through hydrogen bonding, disulphides bridges, and salt bridges
What are the general structures, properties and roles of globular proteins?
- almost spherical shape (3D)
- soluble in water due to position of hydrophilic/ phobic R group
- have metabolic roles
What are the general structure and properties of fibrous proteins?
- regular, repetitive sequences of amino acids
- insoluble in water
- structural roles
For the globular protein ‘Haemoglobin’ explain its structure, it’s function, and its properties.
Structure:
- made up of two a-globin and two b-globin polypeptide chains (each has own tertiary structure).
- Has the prosthetic group (non-protein part vital for functioning) of haem. This allows oxygen to bind to this group.
- Is a conjugated protein (a globular protein with a prosthetic group)
- function: found in red blood cells and binds reversibily to oxygen
- properties: soluble in water as hydrophilic R group on surface
For the globular protein ‘Amylase’ explain its structure, it’s function, and its properties.
Structure: a single chain of amino acids with both a-helix and a b-pleated sheet section
Function: catalysed they break down of starch to maltose
Properties: soluble in water as hydrophilic R group on surface
For the globular protein ‘insulin’ explain its structure, it’s function, and its properties.
Structure:
- made up of 2 polypeptide chains
- chain begins with a-helix and end with b-pleats
- both chains are joined by disulphide bonds
Function: carries out function by binding to specific receptor molecules
Properties: soluble in water as hydrophilic group on outside surface
For the fibrous protein ‘collagen’ what is it’s function and properties?
Function: provide mechanical strength as it’s a structural protein
Properties:
- insoluble in water as there’s a large proportion of amino acids with hydrophobic groups
- no weak spots
- examples of where collagen is found: artery walls, tendons, bones, skin, teeth, cartilage
For the fibrous protein ‘keratin’ what is it’s function and properties?
Function: provide mechanical protection and strength
Properties:
- very strong
- waterproof
- insoluble in water as large proportion of amino acids with hydrophobic groups
- examples of where keratin is found: fingernails, hair, horns, scales, fur, feathers
