Protein Synthesis Flashcards
Coding Regions
Regions of DNA that contain genes that encode proteins.
Noncoding DNA
Regions of DNA that do not code for proteins but has instructions for tRNA, rRNA, regulatory DNA/RNA, and structural DNA
What are the 3 main RNA?
mRNA - messenger RNA
tRNA - transfer RNA
rRNA - ribosomal RNA
mRNA - messenger RNA
Coding RNA. template for protein synthesis taken from DNA
tRNA - transfer RNA
Adapter RNA. Binds amino acids and carries them to mRNA. Anticodons match mRNA codons and amino acid. Transfers amino acids to the growing polypeptide chain
rRNA - ribosomal RNA
RNA component of small and large ribosomal subunits
What are the important process of protein synthesis? Explain briefly how they contribute
Replication - not technically part of protein synthesis but copy of DNA is made
Transcription - DNA gene is copied into mRNA
Translation - Ribosomes make polypeptide based off mRNA
What happens if there are errors during replication, transcription, or translation?
Dysfunctional Proteins
What are the ribosomal subunits and when do they combine?
Small ribosomal subunit
Large ribosomal subunit
Unite to form a ribosome at the start of translation
What are ribosomes? What do they do?
Non-membrane bound organelles made of mostly rRNA.
Assembled polypeptides from amino acids brought in by tRNA
Based on genetic sequence that is specifically written in mRNA
Where can ribosomes form? (x4)
- Floating free in cytosol
- Within mitochondria
- Near/On cytosolic side of RER
- Near/On cytosolic side of outer nuclear membrane
Describe how the ribosome forms and how it reads mRNA
The small and large ribosomal subunits meet at the start of translation when they hook onto mRNA
Ribosome travels down mRNA from 5’ to 3’ direction and adds amino acids as it goes
Ribosome reaches a stop codon so the chain is done, ribosome falls off, and subunits separate.
Subunits find new mRNAs to translate
Polyribosomes
When a more ribosomes start translating at the 5’ end before the first one reaches the 3’ end. Forms a chain of ribosomes bound to one strand of mRNA
What makes polyribosomes beneficial?
Polyribosomes improve translation efficiency by making many copies of a protein from same mRNA template. Efficient because fewer mRNA templates needed, reduces # of errors of DNA so there are fewer transcription errors
Can ribosomal subunits be seen in TEM or LM?
No
How can we visualize ribosomes?
TEM. They appear as e- dense dots and polyribosomes look like spirals or clusters.
LM. Ribosomes contribute to basophilia of cytoplasm
What are the functions of the rough endoplasmic reticulum?
A site where ribosomes and polyribosomes translate mRNA into proteins.
RER sequesters polypeptides into its lumen as they are translated for initial modification of proteins and to monitor protein quality.
Where are ribosomes and polyribosomes located on RER?
Cytosolic side
Describe the structure of the RER
Made up of interconnected cisterns or flattened sacs and covered with ribosomes on cytosolic side.
Cistern membranes are continuous throughout and with the smooth ER and outer nuclear membrane
Cistern lumens are continuous with each other and the lumen of SER cisterns and the perinuclear space
Where is RER extensive?
In cells specialized for protein secretion. It will appear in TEM as big stacks of flat sacs
What are the functions of the Golgi apparatus?
Protein sorting and distribution
Modify proteins produced in RER
Package proteins into vesicles for intracellular transport or for secretion
Attaches vesicles to microtubules
Adds chemical “shipping label”
Describe the structure of the Golgi apparatus?
Has 3-10 cisterns so not as extensive as RER. Bigger lumens. Cistern attached to microtubules and in close association with vesicles.
Has cis-Golgi network (CGN), medial golgi cisterns, and trans golgi network (TGN)
Describe movement of protein through Golgi?
RER - CGN - Medial - TGN - destination
Which way does the cis side curve on the golgi?
Convex
