2.4 Proteins Flashcards
What are the functions of Proteins?
- structural: forming of structural components e.g. collagen
- regulatory: regulating cellular function e.g. insulin
- contractile: contractile elements in muscle e.g. myosin
- immunological: functioning to combat invading microbes e.g. antibodies
- transport: carrier molecules e.g. haemoglobin
- catalytic: catalysing biochemical rections e.g. amylase
- sensory: components of nervous system
What are proteins?
polymers
units are amino acids
single functional polypeptide or more (usually several polypeptides joined together)
General structure of amino acids
central C atom
amine (NH2)
carboxyl (COOH)
R group - each different amino has a different R group (gives it its function)
Info about amino acids
found in living things
coded for by the DNA sequence in the ribosome
that all organisms share the same amino acids is evidence that all living things evolved from a common ancestry
nine amino acids cannot be made by the body and must come from food - essential amino acids
Polypeptides
unbranched chain of amino acids
coded for by a gene
the sequence of bases determines the sequence of amino acids (3 bases codes for an amino acid)
amino acids are joined by a condensation reaction, peptide bond formed
dipeptide is split during a hydrolysis reaction
amino acids can be linked together in any sequence giving a huge range of possible polypeptides
Protein structure
primary: sequence of a chain of amino acids
secondary: occurs when the sequence of amino acids is linked by hydrogen bonds (pleated sheets or alpha helix)
tertiary: occurs when certain attractions are present between alpha-helices and pleated sheets (some proteins end their conformation here)
quaternary: protein consisting of more than one amino acid chain
Protein conformation
the amino acid sequence determines the three-dimensional conformation of a protein
the conformation of a protein is its 3D structure
vital to the function of the protein
Two main structural forms of a protein
fibrous:
- have a structural role
- water insoluble
- tough and stretchy
- composed of long chains of polypeptides
globular:
- catalytic, hormones, transport, immunological
- water soluble
- polypeptide chains folded into a specific shape
living organisms synthesise many different proteins with a wide range of functions
Polarity of proteins
may be polar or non-polar
allow for different materials to pass through the protein in cell membranes and specificity of active sites in enzymes
polar amino acids on surface of proteins make them water soluble
non-polar amino acids make them insoluble
Must know examples of proteins
spider silk: structural - used to make web, tensile strength, difficult to break
insulin: regulatory - hormone that lowers blood sugar levels, binds to body cells
collagen: structural - three polypeptide wound together like a rope, prevents tearing in skin, bones, tendons and ligaments
rhodopsin: sensory - pigment in retinal cells make light sensitivity, cell is stimulated and sends nerve impulse to the brain
immunoglobins: immunological - antibodies bind to specific antigens on pathogens owing to specific surface proteins
rubisco: catalyst - enzyme, catalyses photosynthesis reaction
What is a proteome?
all the different proteins produced by the cell or an organism
every individual has a unique proteome
proteins that different cells make will be different depending on cells function
like a genome
What is a proteome?
all the different proteins produced by the cell or an organism
every individual has a unique proteome
proteins that different cells make will be different depending on cells function
like a genome
