Download 3 Nucleosides nucleotides and nucleic acids

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Nucleotides, Nucleosides and Nucleic Acids
NUCLEOSIDES
These are sugars which are linked to a nitrogen containing base. Those of interest are PURINES and PYRIMIDINES,
which have ring structures. The NUCLEOSIDE is complete when a purine or a pyrimidine binds to ribose or 2deoxyribose. Eg. Adenine (a nucleotide) forms Adenosine when bound to ribose.
NUCLEIC ACIDS
These are dietary organic acids which get digested and broken down into compenent purines and pyrimidines.
Most purines and pyrimidines however are synthesized de novo from amino acids, mainly in the liver.
RNA is constantly recycled, but DNA is stable throughout your lifespan
NUCLEOTIDES
The above purine and pyrimidine ring structures, with the addition of inorganic phosphate, are called NUCLEOTIDES.
PURINE NUCLEOTIDES: Adenine and Guanine
PYRIMIDINE NUCLEOTIDES: Cytosine, Thymine, Uracil
PYRIMIDINE and PURINE CATABOLISM
PYRIMIDINES
Beta- Amino acids
Because Beta-aminoisobutyrate is
a urine-excreted product of
thymine catabolism, it can be used
to measure DNA turnover
Beta-Alanine
Further degradation
Beta-aminoisobutyrate
CO2
NH3
PURINES:
Adenosine
Hypoxanthine
Xanthine
Oxidase
Guanosine
ALLOPURINOL
Xanthine
Inhibits this step
Xanthine
Oxidase
URIC ACID EXCRETION
Usually the level is about 0.24 mmol/L
URIC ACID
IN THE KIDNEY:
- 90% of urate is reabsorbed
- 2% of urate is not reabsorbed
- 8% of urate is SECRETED actively in the
tubules
On a normal diet, you excrete about 1 gram per day
DNA, Deoxyribonucleic acid
This document was created by Alex Yartsev ([email protected]); if I have used your data or images and forgot to reference you, please email me.
Extremely long nucleotide chains containing
- ADENINE
- GUANINE
- THYMINE
- CYTOSINE
The double helix is held together by hudrogen bonds between the bases :
- ADENINE BONDS TO THYMINE
- GUANINE BONDS TO CYTOSINE
A diploid human cell contains 46 chromosomes. Useful factoid to know.
- EXONS are portions of genes which encode protens;
- INTRONS are portions of the gene which are not encoded into proteins
- PROMOTER regions are near the transcription start of the gene, and this is where RNA polymerase binds to start the
encryption of RNA; it usually includes a TATA (thymine-adenine-thymine-adenine) sequence
- There are also REGULATORY sequences along the gene (about 5 of them) which are ENHANCERS and PROMOTERS
MITOSIS and MEIOSIS
- Each time the cell divides, it follows a sequence of steps, as below:
- FIRST, DNA polymerase catalysis the separation of the double helix into two chains
The INTERPHASE: everything that isn’t mitosis (M phase)
-
o G1 = “gap” phase, period of cell growth which follows division; centrioles replicate
o S phase = DNA replicates
o G2 phase = final growth and ativity before mitosis
Prophase, metaphase, anaphase, telophase, and cytokinesis follow – the M phase
PLOIDY:
-
The number of chromosomes in a cell
DIPLOID: normal resting “euploid” cells with the normal number of chromosomes.
TETRAPLOID is what normal diploid euploid cells become at the point where they are about to divide
ANEUPLOIDY is an abnormal number of chromosomes, commonly found in cancerous cells
RNA, Ribonucleic acid
-
SINGLE-STRANDED
HAS URACIL INSTEAD OF THYMINE
The production of RNA from DNA is called TRANSCRIPTION
Transcription is mediated by RNA Polymerase
Most forms of RNA are involved in TRANSLATION which is the formation of proteins from the genetic code
The translation process occurs in ribosomes
References: Ganong's Review of Medical Physiology, Chapter 1