Proteins Flashcards
1
Q
What is a polypeptide ?
A
- A polypeptide is a polymer made of many amino acids joined together by peptide bonds. A protein may contain one or more polypeptide chains.
2
Q
What is a dipeptide ?
A
- Dipeptides are formed by the condensation of two amino acids.
3
Q
What takes place in the primary structure ?
A
- The sequence of amino acids bonded by covalent peptide bonds is theprimary structureof a protein
- intial polypeptide chain
4
Q
What takes place in the Secondary structure ?
A
- Thesecondary structureof a protein occurs when the weak negatively charged nitrogen and oxygen atoms interact with the weak positively charged hydrogen atoms to formhydrogen bonds
- There are two shapes that can form within proteins due to the hydrogen bonds:
- α-helix
- β-pleated sheet
- Thesecondary structureonlyrelates tohydrogen bondsforming between theamino groupand thecarboxyl group(the ‘protein backbone’)
- The hydrogen bonds can be broken by high temperatures and pH changes
5
Q
What takes place in the Tertiary structure ?
A
- Further conformational change of the secondary structure leads to additional bonds forming between theR groups(side chains)
- The additional bonds are:
- Hydrogen(these are between R groups)
- Disulphide(only occurs between cysteine amino acids)
- Ionic(occurs between charged R groups)
- Weakhydrophobic interactions(between non-polar R groups)
- This structure is common inglobularproteins
6
Q
What takes place in the Quaternary structure ?
A
- Occurs in proteins that havemore than onepolypeptide chain working together as a functional macromolecule, for example, haemoglobin
- Each polypeptide chain in the quaternary structure is referred to as asubunitof the protein.
7
Q
Draw a Protein
A
did you do it correct ?
DONT LIE
8
Q
What is a Globular protein ?
A
- Globular Proteins Are Round and Compact
- In a globular protein, the hydrophilic R groups on the amino acids tend to be pushed to the outside of the molecule. This is caused by the hydrophobic and hydrophilic interactions in the protein’s tertiary structure.
- This makes globular proteins soluble, so they’re easily transported in fluids.
9
Q
Name the three globular proteins
A
- Haemoglobin
- Insulin
- Amylase
10
Q
What is a fibrous protein ?
A
- Fibrous Proteins Are Tough and Rope-Shaped
- Fibrous proteins are insoluble and strong. They’re structural proteins and are fairly unreactive (unlike many globular proteins).
11
Q
What are the three fibrous proteins ?
A
- Collagen
- Keratin
- Elastin
12
Q
Describe Haemoglobin
A
- Haemoglobin is a globular protein that carries oxygen around the body in red blood cells It’s known as a conjugated protein - this means it’s a protein with a non-protein group attached.
- The non-protein part is called a prosthetic group. Each of the four polypeptide chains in haemoglobin has a prosthetic group called haem. A haem group contains iron, which oxygen binds to the haem group.
13
Q
Describe Insulin
A
- INSULIN is a hormone secreted by the pancreas. It helps to regulate the blood glucose level.
- Its solubility is important - it means it can be transported in the blood to the tissues where it acts. An insulin molecule consists of two polypeptide chains, which are held together by disulfide bonds.
14
Q
Describe Amylase
A
- AMYLASE is an enzyme that catalyzes the breakdown of starch in the digestive system. It is made of a single chain of amino acids. Its secondary structure contains both alpha-helix and beta-pleated sheet sections. Most enzymes are globular proteins.
15
Q
Describe Collagen
A
- found in animal connective tissues, such as bone, skin, and muscle. It is a very strong molecule. Minerals can bind to the protein to increase its rigidity, e.g. in bone.
