Proteins Flashcards
what are proteins
proteins are polymers made up of amino acids joined together by peptide bonds.
what type of reaction joins two amino acids
condensation
what is the bond between two amino acids called
peptide bond
what reaction breaks the bond between two amino acids
hydrolysis
what is the primary structure of the protein?
the sequence of the amino acids in the protein chains
two types of secondary structure that can appear in a protein
- coiled structure called alpha helix
- a flatter folded structure called beta beta-plated sheet
what bonds hold the secondary structure together.
hydrogen bonds
tertiary structure of a protein
the overall 3D shape of the protein
strength of hydrogen bond
individual bonds are weak but often many H bonds are formed and collectively they provide stability.
strength of an ionic bond
stronger than H bonds
disulfide
very strong
hydrophobic/hydrophilic interactions
weak interactions
properties of globular proteins
compact
water-soluble
spherically shaped
why are globular proteins soluble?
hydrophobic R groups at the centre of the protein and hydrophilic on the outside/surface so water molecules can interact with surface
how does globular proteins’ solubility enable them to carry out their function?
they can carry out important metabolic reactions in an aqueous environment
Examples of globular proteins
haemoglobin
enzymes
peptide hormones
antibodies
T/F haemoglobin has a quaternary structure
TRUE
T/F haemoglobin does not have a prosthetic group
FALSE - the haem group is a prosthetic group
T/F haemoglobin is a simple protein
FALSE-haemoglobin is a conjugated protein because it contains a prosthetic group.
Describe what a conjugated protein is
a conjugated protein has a permanent non-protein component called a prosthetic group
why is haemoglobin described as a conjugated protein?
has 4 haem groups as part of its structure
how does solubility helop globular proteins
insulin has to be transported in the blood to target cells, so it is important that it is soluble.
how does a very specific 3D shape help globular proteins.
insulin has to bind to receptors on target cells therefore its 3D shape is very important
what is transcription
the first stage of protein synthesis
what happens during transcription
DNA - mRNA
what is translation
the second stage of protein synthesis
what happens during translation
mRNA- Protein
role of transcription
to produce short single-stranded sections of mRNA using DNA as a template
Process of transcription
- DNA helicase unwinds and unzips the DNA - breaking hydrogen bonds between nucleotide bases
2.pre-mRNA forms using complementary base pairing with the template strand of DNA
- RNA polymerase catalyses the formation of phosphodiester bonds in the pre-mRNA
Why is collagen such a strong molecule
it is made up of three polypeptides wound together in a strong rope like structure
describe and explain why collagen is a fibrous protein
- triple helix structure
- long polypeptide chains
- structural role , stability within phospholipid bilayer
- no tertiary structure
- high number of hydrophobic R groups makes it insoluble
why are fibrous proteins insoluble?
high number of hydrophobic R groups
what are fibrous proteins?
long strands of polypeptide chains that have cross-linkages due to hydrogen bonds
why are fibrous proteins suited for structural role?
- insoluble
- organised structure due to repetitive sequence
examples of fibrous proteins
keratin
elastin
collagen
what are globular proteins
proteins that are compact spherical and soluble in water
why do globular proteins form a spherical shape when folding into their tertiary structure
- their non-polar hydrophobic r groups are orientated towards centre of the protein
- polar hydrophilic R groups are on outside of protein
what does the prosthetic heam group contain in haemoglobin?
iron which is able to reversibly combine with an oxygen molecule
how much oxygen can a haemoglobin carry
it has 4 heam groups so 4 oxygen molecules.
