Lecture 7 Flashcards
Ribosomes (6)
It makes proteins
It’s roughly spherical
In both eukaryotes and prokaryotes
It is made of rRNA and ribosomal proteins
NO MEMBRANE
Two subunits work together to translate mRNA into polypeptide chain.
Function of ribosomes in protein synthesis
What do they do? When added to MRNA what does it make?
It translates mRNA using TRNA that has appropriate amino acids as codons.
Ribosomes can simultaneously translate the same mRNA
Ribosomes + MRNA is a polyribosome.
What does tRNA do?
It Allianz amino acids along mRNA
AT ONE END THEY HAVE A SPECIFIC ANTICODON FOR MRNA
OTHER END AMINO ACID FOR THAT CODON.
Codon in mRNA goes to anticodon in TRNA
MRNA function?
Encodes amino acid sequence for polypeptide being synthesised
How is aminoacyl trna formed?
Before an amino acid is incorporated the carboxyl end of the AA attaches to the tRNA
Aminoacyltrnasynthase- activates amino acid, covalently links aa to trna
How does the ribosome catalyse peptide bond formation?
3 bonding sites:
Peptidyl trna bonding site
Holds trna molecule at the end of pp chain
Aminoacyl trna bonding holds incoming trna molecule with the aa
What are the three stages of protein synthesis?
Initiation- mRNA couple to small ribosomal unit and to aminoacyltrna
Elongation- polypeptide chain is elongated by covalent bonding in sequence ofamino acids
Termination and polypeptide release
Indicated by stop codons in MRNA
4 functions of ROUGH ER
Protein translocation- folding and transporting proteins
Glycosylation attachmenr of okigosaccharfies
Disulfise bond formation
Membrane synthesis
Smooth ER
Synthesis of lipids (of adrenal cortex) and of lipids
Metabolism of carbohydrates
Major storage and release site of intracellular calcium
Drug detoxification
Transitional Er transport vesicles
What is the Golgi apparatus made of?
What are the three functional regions called.
What surrounds the …….?
Stacks of sacs called cristernae
It has three functional regions called cis medial and trans face.
Surrounding the cisternae are speherical vesicles. Fuse with cis equals transport vesicles and fuse with trans cisternae is secretory vesicles
What type of structure is Golgi?
Polarised structure
Resembles a treadmill transport (movement of substances)
Wat happens to the Golgi cisternae?
I) transition vesicles from the ER converge to form CGN. There are enzymes here
2) cis cisterna transforms to medial and then to transitional
3) transitional forms vesicles containing cargo which is targeted for different destinations
Golgi functions
Modify substances by glycoslilation and phosphorylation
Synthesised mucopollysacharides
Labels with a signal sequence that shows the final destination of molecules
Sort and package
Makes lysosomes
