B1.2 - proteins (2f) Flashcards
what are proteins?
proteins are made of chains of amino acids
where are proteins made?
proteins are made on ribosomes, using information from the base sequence of DNA
what determines a proteins’ function?
the sequence and number of amino acids determine the 3D shape of the protein and therefore its function
what are some examples of proteins?
e.g) enzymes, hormones, fibrinogen, spindle fibres, haemoglobin
what are the dietary requirements for amino acids?
- essential amino acids cannot be synthesized so must be obtained from food
- non-essential amino acids can be made from other amino acids
- vegan diets require attention to ensure essential amino acids are consumed
what are the components of an amino acid?
central carbon atom with 4 groups:
- amine group (NH2)
- carboxyl group (COOH)
- R-group (20 different chemical groups)
- hydrogen (H)
what is the word equation for forming dipeptides?
amino acid + amino acid –> dipeptide + water
- condensation reaction
what is the word equation for forming a tripeptide?
dipeptide + amino acid –> tripeptide + water
- condensation reaction
what is a peptide?
a single linear chain consisting of typically 2-50 amino acid monomer units held together by peptide bonds
what is a polypeptide?
a single linear chain consisting of typically 51+ amino acid monomer units held together by peptide bonds
what is a protein made out of?
one or more polypeptides, folded into a 3D conformation that determines its function
why is there infinite variety of possible peptide chains?
this is due to a combination of three factors:
- peptide chains can have any number of amino acids, from a few to thousands
- there are 20 amino acids coded for in the genetic code
- these amino acids can be in any order
what is denaturation?
irreversible change to the conformation of a protein
what causes denaturation?
high temperatures and extreme pHs cause denaturation
what is the impact of denaturation?
denaturation affects enzymes by changing the shape of its active site, so the substrate is unable to attach
- this slows the rate of enzyme activity by preventing the reaction
how can high temperatures cause denaturation?
- vibrations at high temperatures break bonds
- intramolecular bonds within the protein are broken
- irreversible change to conformation of a protein
- protein cannot carry out it’s function OR soluble proteins become insoluble and precipitate
how does extreme pH cause denaturation?
- extreme pH alters amino acid’ charges and breaks ionic bonds
- intramolecular bonds within the protein are broken
- irreversible change to conformation of a protein
- protein cannot carry out it’s function OR soluble proteins become insoluble and precipitate
what is the role of haemoglobin?
haemoglobin = binds to oxygen, allowing transport of oxygen in erythrocytes
what is the role of insulin?
insulin = a hormone that causes uptake of glucose from the blood by many body cells including muscle and liver cells
what is the role of collagen?
collagen = a structural hormone found in skin and connective tissue such as tendons
what is the role of immunoglobulins?
immunoglobulins = proteins that function as antibodies, binding to antigens on ‘non-self’ cells, such as pathogens
what is the role of fibrinogen?
fibrinogen = a protein involved in blood clotting
what is the role of actin?
actin = a protein in muscle fibers which is involved in cytokinesis and muscle contraction
- the subunits join together to form filaments
what is the role of microtubules?
microtubules = proteins that form the spindle fibres that move chromosomes during mitosis and meiosis
- two different subunits join to form a dimer, which then join together to form filaments
