Proteins Flashcards
Why are proteins needed in our body?
For cell growth/repair, Structural role, help metabolic processes
What roles do proteins have in metabolic processes?
Proteins can form antibodies, enzymes and hormones
Where do proteins have a structural role?
In cytoplasm and muscle, collagen and elastin in the skin, collagen in bone, keratin in hair
What are proteins (and amino acids) made of?
Carbon, hydrogen, oxygen and nitrogen
What is the building block of a protein?
An a amino acid, small monomers (amino acids) join together to form a protein
What is important about the sequence of amino acids in a protein?
It determines the type and function of the protein formed
What 2 groups do all amino acids have?
An amino group, a carboxyl group
What are the two groups in an amino acids attached by?
Centrally, a carbon atom, carrying a hydrogen one side and an R group the other
What is the formula for an amino group?
NH2
What is the formula for a carboxyl group?
COOH (the carbon is double bonded to one of the oxygen)
What is an R group?
A side chain, acts as a functional group and helps determine internal bonds/function/shape (Residual group)
What is a dipeptide?
2 amino acids joined together
What is a polypeptide?
Multiple amino acids joined together (a polymer of amino acids)
How do two amino acids join to form a dipeptide?
Joined by a condensation reaction (1 H2O molecules is lost)
What bond forms between 2 amino acids?
A peptide bond
How can a peptide bond be broken/ 2 amino acids un-attatch?
Hydrolisis (using 1 H2O molecule)
What atoms are involved in forming the peptide bond between two amino acids?
The OH of one of the amino acids COOH group, and one of the H’s of the other amino acids amino group (providing the H2O molecule which is lost)
What is the primary structure of a protein?
The sequence, type and number of amino acids in the amino acid chain
What is the secondary structure of a protein?
After primary structure, the chain takes a particular shape and either folds or coils
What determines weather the protein folds or coils (in its secondary structure) ?
The order of amino acids determines the bonds that form and where they form between certain amino acids in the chain
What are the 2 forms of secondary folding?
An Alpha helix and a beta pleated sheet
How is the alpha helix held in place?
Hydrogen bonds between amino acids in one part of the chain and those a little further along the chain
How is the beta pleated sheet held in place?
It folds in a fan style way (diagonal up, diagonal down) Hydrogen bonds connect adjacent pleated sheets above and below one another
What is the tertiary structure of a protein?
The three-dimensional shape of the protein, further coiling and twisting after the secondary structure
What are the two types of tertiary structure?
Globular and fibrous
What is a globular protein?
A tertiary structure - folds and coils into a complex 3D shape
What is a fibrous protein?
A tertiary structure - twists the secondary structure to form a long rope-like shape
What is a hydrogen bond in proteins?
Attraction between the slight neg charge of one amino acid (e.g. CO) and the slight pos charge of another amino acid (e.g NH)
Ionic bond?
Attraction between a pos charged R group of one amino acid and a neg charged R of another amino acid
Disulfide bond?
Covalent bond between sulfur atoms of the R groups of two cysteine amino acids
What is quaternary structure?
A protein made up of more than one polypeptide chain, that type of protein will not function without all of it’s sub units
What is a prosthetic group?
Non-protein part of a protein, containing inorganic molecules/inorganic ions (e.g. haem in haemoglobin contains inorganic ions and is the p group)
Conjugated protein?
A globular protein with a prosthetic group
Structure of haemoglobin?
Its a conjugated protein(globular), 4 polypeptide chains (2 alpha, 2 beta) and each chain is associated with a haem group
Structure of collagen?
A fibrous protein, 3 polypeptides twisted around one another like a plait (each chain is made of 3 repeating amino acids)
What can chains of collagen form?
The chains in turn form collagen fibril, which links with others to form collagen fibre
Why is collagen important?
Provides support in heart/arteries/bone/cartilage and elasticity in skin
What is the helical structure of haemoglobin?
Folded into a right-handed alpha-helical
What is the helical structure of collagen?
Wound into a left-hand helical structure
Is haemoglobin soluble in water?
Yes (dissolves)
Is collagen soluble in water?
No
Are there many types of amino acid in haemoglobin?
Yes most of all 20
Are there many types of amino acid in collagen?
Made of very few (normally 3), glycine mainly
Is there a prosthetic group in collagen?
No
Role of haemoglobin?
Transport oxygen
What test to use for proteins?
Biuret test, use a control tube for comparison. add equal volumes of protein suspension and sodium hydroxide, shake well, then add copper sulfate drop by drop
What colour should the protein suspension turn after buret test?
Mauve/purple if present, copper sulfate blue if not
