2B- Proteins and genetics

COMPLETE

What is the basic structure of an amino acid?

How are polypeptides made?

Amino acids join together in condensation reactions forming peptide bonds between the amine and carboxyl group→also forms water

What is meant by the primary structure of a protein?

Basic amino acid sequence joined by peptide bonds

Describe the secondary structure of a protein

Where the amino acid is folded either into a alpha helix or a pleated beta sheet bonded by simple hydrogen bonds

Describe the tertiary structure of a protein

• Precise 3d coiled shape

• can include helixes + sheets

• Shape depends on sequence of amino acids

• Polar R groups attract other polar molecules so are hydrophilic

What bonds are formed in the tertiary structure? How strong are they?

• Disulfide bonds- Strong

• Ionic bonds- Strong

• Hydrogen bonds- Weak

• Hydrophobic/philic interactions- Weak

Describe the quaternary structure of a protein

• Many proteins made of 2 or more polypeptide chains

Describe a globular protein

• Round and compact

• soluble in water (hydrophilic on outside)

• hydrophilic R groups

• specific shape important to their function E.g enzymes, hormones, glycoproteins, haemoglobin.

Describe a fibrous protein

• Long strands

• Insoluble in water (hydrophobic on outside)

• Structured roles

  E.g Keratin in hair + skin, cartilage, bones, blood vessels

• Collagen forms polypeptide chains form a triple helix creating fibres

Describe the structure of collagen

Described as a repeating amino acid structure with the chains coiled around each other. Bonds are then formed between these chains such as hydrogen, disulfide and ionic bonds.

What is a function of collagen

Provides strength and flexibility

What are the parts of a nucleotide

• Nitrogenous base (A,T,G,C,U)

• Phosphate

• Pentose sugar (ribose/deoxyribose)

Describe transcription

• Hydrogen bonds between the bases are broken

• RNA polymerase lines up free RNA nucleotides to the template strand and complementary base pairs + phosphodiester + hydrogen bonds

• once it finishes assembling at the stop codon the mRNA moves out of the nucleus through nuclear pores → attaches to a ribosome.

Describe translation

• attaches to a ribosome

• tRNA with complementary anticodons attach to the mRNA

• tRNA also transports amino acids to ribosome

• the amino acids on the tRNA are joined by peptide bonds

• the tRNA moves away leaving the amino acid behind.

• repeats forming a polypeptide chain

What is a gene

a sequence of bases in DNA that codes for an amino acid sequence/protein