Chapter 4: Nucleosides, Nucleotides, DNA, and RNA

nucleoside and nucleotide functions

- maintain and transfer genetic information

- drive protein synthesis

- store energy if body is desperate

- metabolic regulation

nucleotide composition

- base (parent compound)

- sugar

- one phosphate group or more

parent compound/base types

purine and pyrimidine

possible sugars for nucleotide

- 2-deoxy-D-ribose

- D-ribose

nucleoside composition

- base

- sugar

pyrimidine bases

cytosine, thymine, uracil (CUT)

purine bases

adenine, guanine (AG)

molecules involved in purine synthesis

- ATP

- glycine

- aspartic acid (D)

- glutamine (Q)

- CO2

- folate/folic acid

folate/folic acid

a form of vitamin B, also called folacin; essential for metabolism

molecules involved in pyrimidine synthesis

- ATP

- aspartic acid (D)

- glutamine (Q)

- CO2

monophosphate

nucleotide with one phosphate group

phosphodiester bond

the type of bond that links the nucleotides in DNA or RNA.; joins the phosphate group of one nucleotide to the hydroxyl group on the sugar of another nucleotide

nucleotide catabolism

1) phosphate groups removed (becomes nucleoside)

2) sugars enter metabolic pathway

3) purine bases convert to xanthine; eventually excreted as uric acid

uric acid

nitrogenous waste excreted in the urine

free radical

an atom or a group of atoms that has one unpaired electron

formation of phosphodiester bond

hydroxyl group (-OH) on the 3rd carbon of one nucleotide reacts with the phosphate group attached to the 5th carbon on another nucleotide

type of reaction in creation of phosphodiester bond

condensation reaction

oligonucleotide

a short polymer of nucleotides (usually fewer than 50)

polynucleotide

long chain of nucleotides

3' end

- the end of the DNA ladder that DNA polymerase can add nucleotides to during DNA replication

- free hydroxyl group

5' end

the end of the DNA ladder that DNA polymerase is UNABLE to build

DNA polymerase

principle enzyme involved in DNA replication

RNA composition

- single helix

- ribose sugar

- phosphate

- nitrogen-containing bases

RNA function

protein synthesis

messenger RNA (mRNA)

RNA molecule that carries copies of instructions for the assembly of amino acids into proteins from DNA to the rest of the cell

transfer RNA (tRNA)

form of RNA that brings amino acids to ribosomes during protein synthesis

ribosomal RNA (rRNA)

type of RNA that combines with proteins to form ribosomes (post-transcription)

regulatory RNA

RNA molecule that plays a role in controlling gene expression

ribozymes

- can catalyze transfer of amino groups to a growing protein sequence

- can act on themselves or other RNA molecules

DNA functions

directs protein synthesis and serves as genetic blueprint during cell replication

DNA bases act in

pairs

part of DNA molecule that is more hydrophobic

internal

part of DNA molecule that is more hydrophilic

external

internal DNA groups

where bases are found in the DNA double helix

external DNA groups

- where sugars and phosphate groups are found in the DNA double helix

- outer hydrophilic deoxyribose and phosphategroups are exposed to the water environment of thecell

purine and pyrimidine characteristics

- highly conjugated weak bases

- relatively hydrophobic

why bases stack

3-D structure of double helix

type of bonds between amino and carboxyl groups

hydrogen bonds

why bonds between amino and carboxyl groups in DNA can be undone and why this is important

- hydrogen bonds are noncovalently attracted

- can separate to allow for DNA replication

- double helix can then rebond to protect the DNA message

chromosomes

- threadlike structures made of DNA molecules that contain the genes

- where nucleotide strands that code for each protein are found

genome

A,G,C,T sequence of nucleotides in living system

mitochondrial DNA (mtDNA)

- genetic material in the mitochondria of the cytoplasm of a cell

- 13 total proteins involved in energy production

- only inherited from the mother

- circular shape

importance of mtDNA shape

- efficient way to quickly make energy

- break phosphodiester bond quickly

exons

expressed sequence of DNA; codes for a protein

introns

- intervening, noncoding sequences of DNA located between genes and in between exons