1. Proteins - General Structure of Proteins Flashcards
What decides the amino acid sequence that determines the primary structure of a protein?
A DNA sequence
Describe the ionic bonds that hold the tertiary structure of a protein in place.
Form between free CARBOXYL and AMINO groups in the POLYPEPTIDE chain or between OPPOSITELY charged R groups of AMINO ACIDS
How would you carry out the Biuret test for proteins?
- Place a 2cm3 of food in a test tube.
- Add 2 cm3 of sodium hydroxide solution at room temperature.
- Add a few drops of very dilute copper (II) sulfate solution (Biuret reagent)
- Observe and record colour change.
Which colour does Biuret solution turn in the presence of protein?
Biuret changes from blue to purple.
Describe the disulfide bonds that hold the tertiary structure of a protein in place.
Only with cysteine that can form disulphide bridges which are strong covalent bonds
What do we call 2 amino acids chemically joined together?
Dipeptide
Name the bonds that hold the tertiary structure of a protein in place.
Disulfide Bonds
Hydrogen Bonds
Ionic Bonds
Name 3 fibrous type proteins
Collagen
Keratin
Silk
What do the below instructions describe:
* Place a 2cm3 of food in a test tube.
* Add 2 cm3 of sodium hydroxide solution at room temperature.
* Add a few drops of very dilute copper (II) sulfate solution (Biuret reagent)
* Pale blue to lilac
The Biuret test for proteins.
Identify the molecule
Amino acid
What is the monomer unit of a protein?
Amino acid
What is meant by a fibrous protein?
A protein made from long parallel polypeptide chains. These chains are linked by cross bridges.
Form stable molecules
Structural function
Give 3 examples of enzymes
Amylase
Protease
Lipase
Give 2 examples of hormones
Insulin
Oestrogen
What is the function of the protein keratin?
the main component of hard structures such as hair, nails, claws and hooves.
What is meant by the primary structure of a protein?
The sequence of the amino acids in the polypeptide that forms the protein.
Which colour does Biuret reagent turn in the absence of protein?
It remains a blue colour
What is meant by the secondary structure of a protein?
Hydrogen bonds form between amino acids in the chain causing it to fold into an ALPHA HELIX or fold into a BETA PLEATED SHEET.
The NH group and C–O on each side form weak hydrogen bonds.
Identify the circled group
R group
Idenitfy the circled group
Amine group
What is meant by the tertiary structure of a protein?
When the α helix or β pleated sheets of the secondary protein structure are folded even more to give a complex, specific 3D structure.
What colour is Biuret reagent?
Blue
What is meant by a globular protein?
- More spherical
- Carry out metabolic functions
- Channel proteins in membranes
Describe the hydrogen bonds that hold the tertiary structure of a protein in place.
Individually weak and easily broken
Cumulatively provide some strength
What is the polymer unit of a protein?
Polypeptide
How can a polypeptide be broken down into amino acids?
Hydrolysis
How many naturally occurring amino acids are their?
20
Name 3 globular type proteins
Enzymes
Antibodies
Transport proteins eg Haemoglobin
What is the only difference between different amino acids?
the R-group
Give an example of a transport protein
Haemoglobin in red blood cells
Cell membrane transport protiens
Which type of bond forms between two amino acids?
Peptide bond
A change of just 1 amino acid in the primary structure of a protein can cause what to happen?
A change in the shape of the protein.
The protein will stop working.
The protein will stop working as well.
Every protein has a very _________ 3D shape, which is why they can carry out very ________ functions
specific
specific
Name the 3 groups present on in an amino acids molecule.
Amino group (NH2)
Carboxyl group (COOH)
R-group
What is released when two amino acids chemically join together?
A water molecule (from condensation reaction)
Identify the circled group
Carboxyl group
Which type of reaction takes place during the polymerisation of amino acids?
Condensation reaction
What is the function of the protein collagen?
the main component of connective tissue such as tendons and cartilage
Which part of the amino acid structure is different inthe 20 different amino acids.
The R group
Give an example of a prosthetic group that is asociated with a quaternary protein structure.
The iron containing ‘Haem’ group in the haemoglobin protein.
What is meant by the quaternary structure of a protein?
(Molecule contains) more than one polypeptide (chain);
There may also be prosthetic (non protein) groups attached to these proteins.
Describe the structure of proteins
- Polymer of amino acids;
- Joined by peptide bonds;
- Formed by condensation;
- Primary structure is order of amino acids;
- Secondary structure is folding of polypeptide chain due to hydrogen bonding;
- Tertiary structure is 3-D folding due to hydrogen bonding and ionic/disulfide bonds;
- Quaternary structure is two or more polypeptide chains;
Describe how proteins are digested in the gut
- Hydrolysis of peptide bonds;
- Endopeptidases break polypeptides into smaller peptide chains;
- Exopeptidases remove terminal amino acids;
- Dipeptidases hydrolyse/break down dipeptides into amino acids;
describe how a peptide bond is formed between 2 AA to form a dipeptide
condensation reaction/loss water
between amine and carboxyl group
describe how the secondary structure of a protein is produced
H bonds
between NH and C=O
forming beta pleat sheets or alpha helix
2 proteins have same number and type of AA but different tertiary structire - why?
different sequence of AA
therefore
ionic/H/disulphide bonds form in different places
Describe the hydrogen bonds that hold the tertiary structure of a protein in place.
Plentiful but easily broken
Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells
- DNA in nucleus is code (for protein);2. Ribosomes/rough endoplasmic reticulum produce (protein);Accept rER for ‘rough endoplasmic reticulum3. Mitochondria produce ATP (for protein synthesis);4. Golgi apparatus package/modifyORCarbohydrate added/glycoprotein produced by Golgi apparatus:Accept body for apparatus5. Vesicles transportORRough endoplasmic reticulum transports6 (Vesicles) fuse with cell-surface) membraneAccept exocytosis at cell membrane
Eukaryotic cells produce and release proteins.Outline the role of organelles in the production, transport and release of proteins from eukaryotic cellsDo not include details of transcription and translation in your answer.
- DNA in Is code (for protein),2. Ribosomes/rough endoplasmic reticulum produce (protein), Accept rER for ‘rough endoplasmic reticulum3. 4. Mitochondria produce ATP (for protein synthesis), Golgi apparatus package/modity:ORCarbohydrate added/glycoprotein produced by Golgi apparatus, Accept body for ‘apparatus’5. Vesicles transporttransports;6. (Vesicles) fuse with cell(-surface) membrane; Accept exocytosis at cell membrane
