The necessary introduction to histology

or

What is the composition of the living matter?

Physical and chemical features of the components of living mass determine their visualization on histological slide.

Doc. MUDr. Marie Jirkovská,CSc

Institute of Histology and Embryology

DNA- deoxyribose, phosphate, bases (adenine, guanine, thymine, cytosine - A,G,C,T)

nucleotide dinucleotide

DNA molecule – hydrogen-bonded base pairs

less morestable stable

R.J.Epstein: Human Molecular Biology, 2003

From DNA to chromosome

Levels of DNA structure R.J.Epstein: Human Molecular Biology, 2003

RNA- ribose, phosphate, bases (adenine, guanine, cytosine, uracil - A,G,C,U)

mRNA – messenger RNA (transfer of information from nucleus to cytoplasm)

rRNAs – together with certain proteins form ribosomestRNAs – match aminoacids to codons in mRNA

ATP (adenosine-triphosphate), GTP (guanosine-triphosphate) - ribonucleotides containing high-energy bonds.

R.J.Epstein: Human Molecular Biology, 2003

Proteins long chains of L-aminoacids, each linked to its neighbor through peptide

bondAminoacids: essential (from food only)

nonessential (synthetized in the organism)

According to features of aminoacids side chains (R) polypeptides form three-dimensional conformation and have electrical charge. Polypeptides may bind oligosaccharide chain (glycoproteins).

Various shapes of protein molecules

Alberts B et al. Essential Cell Biology, 1998

R.J.Epstein: Human Molecular Biology, 2003

Lipids – water insoluble (fatty acids, triacylglycerols, steroids, glycolipids)

Fatty acids

a) saturated

b) unsaturated (one or more double bonds ). Components of glycolipids, phospholipids and triacylglycerols.

Triacylglycerols - esters of glycerol and fatty acids

Steroids - cholesterol and its derivatives (steroid hormones, biliary acids)

Glycolipids - composed of two long hydrocarbon chains and a polar region containing one or more sugar residues.

Essential fatty acids – from food only (e.g. linoleic acid, linolenic acid).

Alberts B et al. Essential Cell Biology, 1998

Sugars (mono-, di-, oligo-, polysaccharides)

Monosaccharides - e.g. components of nucleic acids (ribose, deoxyribose), energy source (glucose).

Disaccharides - energy source, absorbed after breaking down into monosaccharides.

Oligosaccharides and polysaccharides - linear and branched molecules made from monosaccharides, e.g. glycogen (made entirely of glucose units).

Alberts B et al. Essential Cell Biology, 1998

Enzymesdetermine all of the chemical transformations that occur in cells. Each

of thousands of those transformations is catalysed by a special enzyme. The name of enzyme is characterized by suffix -ase (e.g.

phosphatase, dehydrogenase).

Enzyme consists of a big protein molecule which conformation forms „active site“ - there is bound molecule of substrate (S). Enzyme catalyses its transformation to product.

In addition to protein molecule (apoenzyme), the function of some enzymes requires cofactors ( Mg+2 , Zn+2) or coenzymes (e.g. vitamine derivatives). Temperature and pH influence the activity of enzyme.

Lock and key model of enzyme mechanism.

Elliot H, Elliot D: Biochemistry and molecular biology, 2001