MBB11003 -Molecular and Cell Biology Flashcards
What are the universal properties of cells?
-contain DNA
-cell components can self-assemble
-proteins require signals
-they can respond to signals from environment
-they have feedback mechanisms
What are the roles of proteins?
-recognise specific molecules (hormones, antibodies, DNA binding proteins)
-move other molecules (eg. porin, ferritin)
-accelerate the rate of rxns (enzymes)
-structural roles (microtubules)
What is the primary structure of a protein?
the order of amino acids in a polypeptide
-involves peptide bonds (which have no rotation)
What is the secondary structure of a protein?
the folding of peptide chain into its 3D structure -alpha helix or beta sheet
-involves H-bonds
-represented by ribbon diagrams
What is the tertiary structure of a protein?
the tightly-packed thermodynamically stable 3D structure of a protein
-involved non-covalent interactions between side chains
What interactions occur between cysteine residues?
disulphide bridges
-S-H → -S-S-
-form crosslinks
What are protein domains?
areas of the protein which fold tightly and carry out a specific part of the protein’s function
-one protein will have multiple domains
What is the quaternary structure of a protein?
a protein’s complex structure made up of two or more subunits joined together
-can be a dimer (2 subunits), trimer (3 sub-us), tetramer (4 sub-us), etc
What happens in post-translational modification?
-specific parts of sequence are removed (irreversible!)
-molecules are added (methylation, glycosylation, ubiquitination, phosphorylation)
What is methylation?
addition of methyl group
eg. histones are methylated to control which parts of genome are expresses
What is glycosylation?
addition of sugars
-usually to cell surface proteins or secreted proteins
What is ubiquitination?
addition of ubiquitin (76-amino acid polypeptide -small regulatory protein)
-for degradation
What is phosphorylation?
addition of phosphate group (PO3)
-done by kinases (requires ATP, which is dephosphorylated to ADP and Pi)
-typically done to serine, threonine or tyrosine residues
-can regulate enzyme function (can change active site’s properties and alter binding of substrate)
-can be reversed by phosphatases
What are the Mendelian laws of inheritance?
-law of segregation (genes come in pairs, one of which is passed onto the offspring)
-law of independent assortment (different genes are passed onto the offspring separately)
-law of dominance (when there are two alleles of a gene, the dominant allele is expressed)
What is Mendel’s law of segregation?
genes come in pairs, one of which is passed onto the offspring
What is Mendel’s law of independent assortment?
different genes are passed onto the offspring separately
What is Mendel’s law of dominance?
when there are two alleles of a gene, the dominant allele is expressed
What can be concluded from Mendel’s laws of inheritance?
there must be a physical genetic material, which is able to be replicated, stored, expressed and varied via mutations
Why did Sutton use grasshoppers/Boveri use Ascaris worms when investigating genetic material?
-both have large chromosomes
-both only have a few chromosomes
What did Sutton and Boveri observe?
-chromosomes group in pairs and can separate
-chromosome number is reduced in gametes
-chromosomes are required for embryonic development
-chromosomes are linear structures made of genes
What did Sutton and Boveri investigate?
chromosomal inheritance
What did Frederick Griffith investigate?
whether characteristics could be swapped
investigated Streptococcus pneumoniae + whether he could make the S strain into R strain and vice versa
What is the difference between S strain and R strain Streptococcus pneumoniae?
S (smooth) strain has a polysaccharide coat (forming a protective capsule around the bacteria, protecting it from the host’s immune system) and is pathogenic
R (rough) strain does not have a polysaccharide coat (so is unprotected from host’s immune system) making it not pathogenic
What was the transforming principle Griffith came up with?
something hereditary which was causing a change in genotype
-options were DNA, proteins, polysaccharides, lipids, RNA