Carbohydrates and Nucleic Acids

Carbohydrates

Major source of energy, composed of carbon, hydrogen, and oxygen.

Monosaccharides

The simplest form of carbohydrates, consisting of 1 carbonyl and 7 hydroxyl groups

Glucose (C6H12O6)

A monosaccharide, main sugar in our blood, energy fuel.

structure: 2 hydroxls below plane (C), 2 hydroxyls above plane (C)

Galactose (C6H12O6)

A monosaccharide.

structure: 1 hydroxl below plane (C), 3 hydroxyls above plane (C)

Fructose (C6H12O6)

A monosaccharide.

structure: pentameric with 2 carbonyls

Disaccharides

Carbohydrates formed by the union of two monosaccharides.

Maltose

A disaccharide composed of 2 glucose molecules, joined by a glycosidic bond

One glucose has 2 hydroxyls below plane, other glucose has 1 hydroxyl on each side of plane

Lactose

A disaccharide composed of galactose and glucose, joined by a glycosidic bond

Glucose is flipped

Sucrose

A disaccharide composed of glucose and fructose, joined by a glycosidic bond

Polysaccharides

Polymers of glucose

Cellulose

A polysacharide in unbranched chains so stacks very easily and linked by glycosidic bonds

Starch

A polyssacharide that is a mixture of unbranched (amylose) and branched (amylopectin) polymers. Linked by alpha-1,4-glycosidic bonds

Glycogen

A polysaccharide that is highly branched and is the short-term storage molecule of glucose

Glycosidic bond

A type of covalent bond that joins a carbohydrate molecule to another molecule.

Nucleic acids

Biomolecules essential for all known forms of life, includes DNA and RNA.

Nucleotides

The building blocks of nucleic acids, composed of a phosphate group, pentose sugar, and nitrogenous base.

Phosphodiester bond

The bond that links nucleotides in a nucleic acid.

DNA (deoxyribonucleic acid)

Exists as 2 strands of polynucleotides called a double-helix. Each strand connected via H-bonding. Wraps around histones.

Consists of a phosphate group, deoxyribose sugar, nitrogen base (A, C, G or T), linked by phosophodiester bonds forming a polynucleotide.

Found only in nucleus and stores genetic information. Exists as genes (sections of DNA that contain the code for all proteins)

Phosphate group always bound to _

5’ aka 5 prime (5th carbon)

Ends of DNA have a _

Free 5’ (free 5 prime) phosphate and free 3’

A binds to _ as they both can have 2 H-bonds

C binds to _ as they both can have 3 H-bonds

Purines

Adenine, Guanine aka A, G

Pyrimidines

Cytosine, Thymine, Uracil aka C, T, U

number of base pairs

3 billion

number of protein coding genes

20,000

number of proteins

120,000

RNA (ribonucleic acid)

A nucleic acid involved in protein synthesis, single-stranded, significantly shorter than DNA (RNA is a copy of a gene not a chromosome)

Contains a phosphate group, ribose sugar, nitrogen base (A, C, G or U), linked by phosophodiester bonds forming a polynucleotide.

mRNA

messenger RNA, code for proteins

rRNA

ribosomal RNA, forms basic structure of ribosome and catalyses protein synthesis

tRNA

transfer RNA, brings specific amino acids to the ribosome during translation based on the mRNA codon.

Codon

A sequence of three nucleotides that encode a specific amino acid.

Protein synthesis

making proteins

What do all proteins start with?

amino acid methionine (AUG)

Transcription

1st step of protein synthesis

1. DNA unwinds and a section (gene) is transcribed into anti-sense strand (opposite of original)

2. pre-mRNA synthesised by changing T to U

3. pre-mRNA spliced (introns removed, extrons spliced/joined)

4. mRNA moves from nucleus towards ribosomes

Translation

2nd step of protein synthesis

5. mRNA attaches to ribosome

6. tRNA brings amino acid to mRNA

7. ribosome moves along mRNA as amino acids are added to the growing peptide chain

8. complete protein is released

Stop codons

Nucleotide triplets that signal the termination of translation.

Mutation

A permanent change to the nucleotide sequence in DNA. Can arise by exposure to radiation/chemicals or genetic disease

Silent substitution mutation

nucleotide substitution but same codon

Missense substitution mutation

nucleotide substitution making different codon

Nonsense substitution mutation

nucleotide substitution making a stop codon

Chromosomal mutations

deletion, duplication, inversion, insertion or translocation of chromosome

Deletion mutations

Deletion of a single nucleotide which produces incorrect amino acid sequence

Frameshift mutations

by addition: adding extra nucleotide

by deletion: removing nucleotide