Cells and Genomes 21:54
What do I need to know?
What are the universal features common to all life on our planet?
The diversity of cells
Universal Features of Cells on Earth
All living cells on earth store their hereditary information in DNA.
All cells replicate their hereditary information by templated polymerization:
Templated polymerization is the way in which information is copied throughout the living
Each nucleotide consists of two parts: a base (either A, C, T, or G), and a sugar with a phosphate
attached to it.
Each sugar is linked to the next via the phosphate group, creating a long polymer chain.
For a single, isolated strand of DNA, monomers can be added in any order because they all attach
in the same way
Individual sugar-phosphate groups are asymmetric, giving the strand a polarity or directionality.
Transcription: where segments of the DNA sequence are used as templates for the synthesis of
shorter molecules of the closely related polymer RNA.
In RNA, the backbone is formed of ribose instead of deoxyribose.
Uracil replaces thymine.
DNA is fixed, but RNA transcripts are mass-produced and disposable.
mRNA: guides the synthesis of proteins according to the genetic instructions stored in the DNA.
Proteins are long unbranched polymer chains, formed by stringing together monomeric building
Proteins form most of the cell’s mass.
Amino acids are the monomers of proteins; there are 4 types.
Polypeptides are protein molecules. Each polypeptide is created by joining amino acids in a
particular sequence that folds into a precise 3D form with reactive sites on its surface.
A groove in the surface of the polypeptide, the enzyme lysozyme, forms a catalytic site.
Polysaccharide molecule: a polymer chain of sugar monomers; binds to the catalytic site of
lysozyme and is broken apart, as a result of a covalent bond-breaking reaction catalyzed by the
amino acids lining the groove.
Proteins are the molecules that put the cell’s genetic information into action.