Proteins Flashcards
Describe the structure of an amino acid. (F)
- amine group (-NH2)
- carboxyl group (-COOH)
- alpha-carbon (C)
- R-group (variable)
State how many amino acids occur in life.
20
Explain how the variety of amino acids leads to a wide range of dipeptides and very quickly to an incredible variety of polypeptide chains.
- Dipeptide: 400 possible combinations (20^2)
- Tripeptide: 8000 possible combinations (20^3)
- etc.
Define the term “polypeptide chain”.
Chain of three or more amino acids
Describe how one end of a polypeptide chain differs from the other end.
One end is an amine group (-NH2) which has basic properties, and the other end is a carboxyl group (-COOH) and has acidic properties.
Define the term “primary structure” of a protein. (F)
The sequence of amino acids.
Define the term “secondary structure” of a protein and describe the two different types. (F)
The folding of the polypeptide chain into an alpha helix (coiled) or beta pleated sheet (flat).
Define the term “tertiary structure” of a protein. (F)
The 3D shape of a polypeptide chain.
Explain how the primary structure of a protein determines its tertiary structure.
The R-groups on the amino acids affect the bonding in the tertiary structure.
Define the term “quaternary structure” of a protein.
When two or more polypeptides associate.
Define the term “globular protein”. (F)
Spherical, water-soluble protein.
Define the term “prosthetic group”. (F)
Non-protein component of a conjugated protein
Give an example of a conjugated protein (the bloody one).
Haemoglobin
Give an example of an enzyme (the H2O2 one ;) ).
Catalase
Give an example of a peptide hormone (the sugary one).
Insulin
Give 3 examples of fibrous proteins.
- collagen
- elastin
- elastin
Describe the structure of collagen.
- 3 polypeptide chains
- triple helix
- every third amino acid is glycine
- hydrogen bonds
Describe the structure of keratin.
- lots of cysteine (with S)
- disulfide bridges (degree of disulfide bonds determines flexibility)
Describe the structure of elastin.
- cross-linked structure
- covalent bonds between lysine amino acids
Compare the structure of globular and fibrous proteins.
- G is spherical
- F is long
Compare the properties of globular and fibrous proteins.
- G is soluble
- F is insoluble
Compare the functions of globular and fibrous proteins.
- G acts as enzymes and hormones
- F acts as structural components
Identify the key structural components of haemoglobin.
- 4 polypeptide chains
- 2 alpha helices, 2 beta pleated sheets
- 4 haem prosthetic groups (Fe2+)
State the properties of haemoglobin.
Haem group combines reversibly with an oxygen molecule
State the functions of haemoglobin.
Transports oxygen in red blood cells
Identify the key structural components of catalase.
- 4 polypeptide chains
- 4 haem prosthetic groups (Fe2+)
State the properties of catalase.
Can interact with H2O2 with haem groups
State the functions of catalase.
Speeds up breakdown of H2O2 formed from metabolic reactions
Identify the key structural components of insulin.
3 polypeptide chains
State the properties of insulin.
- soluble
- precise shape
State the functions of insulin.
Regulation of blood glucose concentration
Describe the properties of collagen.
- flexible
- tough
Describe the location of collagen.
- skin
- tendons
- ligaments
- nervous system
Describe the functions of collagen.
Connective tissue
Describe the properties of keratin.
- strong
- inflexible
- insoluble
Describe the location of keratin.
- hair
- skin
- nails
Describe the functions of keratin.
- protection
- adhesion
Describe the properties of elastin.
- flexible
- strong
Describe the location of elastin.
- walls of blood vessels
- alveoli in lungs
Describe the functions of elastin.
- allow flexibility to expand when needed
- allow to return to normal size
- strength and elasticity
What holds the primary structure of a protein held together? (F)
Peptide bonds
What holds the secondary structure of a protein held together? (F)
Hydrogen bonds
What holds the tertiary structure of a protein held together? (F)
- hydrogen bonds
- ionic bonds
- disulfide bridges
- hydrophobic-hydrophilic interactions
What holds the quaternary structure of a protein held together? (F)
- hydrogen bonds
- ionic bonds
- disulfide bridges
- hydrophobic-hydrophilic interactions
Define the term “protein”.
One or more polypeptides with a specific function
Define the term “fibrous protein”. (F)
Long, insoluble, structural protein.
Define the term “conjugated protein”. (F)
Globular protein that contains a prosthetic group
