2.1.2 & 2.1.3 Biological Molecules Part 2 COMPLETE Flashcards
Proteins
Can be structural or functional and they provide building materials.
Also vital in metabolic activity, made up of amino acids
Testing for Proteins
Biuret Solution
Mix with equal volume of the sample, swirl and look for colour changes
The chemicals react with the peptide bonds
Amino Acids
Have an Amine group, an acid group and an R group
Animals and plants use them to make larger proteins
Primary Structures
Condensation occurs in protein synthesis to create amino chains
Hydrolysis breaks them down with the aid of enzymes (Protease) used in ageing, hormone regulation and digestion
Secondary Structure
Polypeptides fold to produce alpha helices or beta plead sheets
H bonds form between the differences in charge and help stabilise the structure.
Not very strong but lots of them, they’re sensitive to temp and pH
Tertiary Strucure
3D shape of the protein, and created by the interaction of alpha helices and beta pleated sheets
Four main type of bonds include: Disulfide, ionic, hydrogen and hydrophobic and phillic interactions. All form between the R groups from the functional group
Quaternary Structure
Determined by the tertiary structure and is the proteins final 3D structure
Either Globular or Fibrous
Globular
Rolled into balls
Precise non repeating amino sequences of equal length
Water soluble
Used in metabolic reactions e.g. enzymes
Fibrous
Form fibres
Often repeating amino sequences with varying length
Usually insoluble
Used for the structures
Examples of Globular proteins
Haemoglobin
Insulin
Pepsin
Examples of Fibrous proteins
Collagen
Keratin
Elastin
Computer Modelling
Predict the structure of proteins using AB initio (based on physical or electrical properties) , or Comparative techniques
TLC
Thin layer chromatography
Used to separate a mixture into its constituents
Has a mobile and stationary phase
Visualisation
Cant always see the molecules used in TLC, can add UV light to see fluorescent parts
Ninhydrin to see amino acids
How TLC works
The speed which a molecule moves along the plate depends on their solubility and polarity. The less polar the faster it’ll travel as won’t stick to the OH groups by forming H bonds
Types of Nucleic Acid
DNA- Deoxyribonucleic Acid
RNA- Ribonucleic Acid
DNA structure
A double helix made of two polynucleotide strands that are antiparallel to each other
They have complimentary base pairs that are attached to the sugar phosphate back bone
Nucleotides
Monomer unit of nucleic acids
Made of three subunits, the Phosphate, a five carbon sugar and a base
DNA Bases
Four types of nitrogenous base two purines (A and G) with two rings, and two pyrimidines (T and C) with one ring
Making DNA
Phosphodiester bonds form in condensation reactions
The DNA is made of a double helix, the strands are made of a sugar phosphate backbone with a nitrogenous base attached
Not at right angles so form a helix
Base Pairing
Hydrogen bonds form between the bases on the polynucleotides
A-T
G-C
They are complimentary
DNA in Eukaryotes
Majority of DNA is in the nucleus
They’re wound around Histone proteins that forms chromosomes
There’s a loop of DNA inside the mitochondria and chloroplast
DNA in Prokaryotes
DNA is a loop within the cytoplasm
There’s no nucleus and its classed as being naked
DNA extraction
Add Ethanol and a strong detergent to the mixture.
To further purify add salts
Semi Conservative Replication
- Double Helix untwists in sections
- The H bonds are broken by DNA helicase and the DNA unzips, exposing the nucleotide bases
- Free nucleotides associate with the exposed ones
- Unzipped strands are used as a template, DNA polymerase is used to catalyse the addition
- Phosphodiester bonds form
Other uses of Nucleotides
- Become phosphorylated, e.g. to make ATP
- Help regulate metabolic pathways
- Be components of coenzymes
Describe Genetic Code
Its universal as the same triplet of bases codes all the amino acids
Triplets as three bases code for one amino acid, rehire called codons
Degenerate all amino acids have more than one base triplet
Non Overlapping as the code is read from a fixed point that ensure they’re read in the correct order
Mutation
Errors sometimes occur when the wrong nucleotide is inserted. They are random and spontaneous
They aren’t always harmful and can be advantageous
How is RNA different to DNA
- Single not double stranded
- Ribose sugar not deoxyribose sugar
- Uracil replaces Thymine
Different forms of RNA
- Messanger RNA
- Ribosomal RNA
- Transfer RNA
Protein Synthesis
Occurs in the ribosome
Has two main stages Transcription and Translation
Instructions for proteins can’t pass out the nucleus so are carried by mRNA
Transcription
mRNA is formed in the nucleus
DNA unzips and the RNA nucleotides form complimentry bases on the template strand
RNA polymerase checks for mistakes
The mRNA breaks off and leaves the nucleus via a pore
Ribosomes
Made in the nucleolus from ribosomal RNA, exits via the pores
Moves into the cytoplasm and two subunits come together
In the groove mRNA is translated into a protein
Transfer RNA
tRNA
Made in the nucleolus and passes into the cytoplasm
Has four prolonged polynucleotides that join with amino acids
Translation
mRNA attaches onto ribosomes with 2 free codons
tRNA in the cytoplasm has a specific amino acid attached to it so the tRNA attaches to the mRNA
The first codon is always AUG
Peptide bonds form requiring ATP
mRNA components are recycled after
