Page 53 - Cell biology PDG 2024

the protein ex: hydrogen bonding, ionic bonding and dipole-dipole
interactions
Ex: myoglobin
4) Quaternary structure
Some proteins are made up of multiple polypeptide chains, also
known as subunits. When these subunits bind together, they give
the protein its quaternary structure.
Ex: hemoglobin (tetramer formed of α(2):β(2)), DNA polymerase
(formed of 10 subunits)
Denaturation of proteins:
When a protein loses its higher-order structure, but not its primary
sequence, it is said to be denatured. Denatured proteins are usually
non-functional
Gene expression

It is the process during which the genetic information of the gene is used
for production of a functional protein. It is also the process at which
genotype gives rise to the phenotype

Gene expression occurs in eukaryotes, prokaryotes, and viruses

All steps in the gene expression process are regulated. Regulation of gene
expression includes the control of the timing, location, and amount of the
protein that will be produced. This regulation of gene expression is
important for cellular differentiation and development

Regulation of gene expression

First we should know some terms:

Constitutive gene: is a gene that is transcribed continually

Facultative gene: is a gene which is only transcribed when needed

Housekeeping gene: is a gene that is required to maintain basic cellular
function and so, it is expressed in all the cells of an organism. Examples:
actin, GAPDH and ubiquitin. Some housekeeping genes are transcribed at
a relatively constant rate and these genes can be used as a reference point
in experiments to measure the expression rates of other genes

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