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FoundSci I Unit 3 > Protein Synthesis > Flashcards

Protein Synthesis Flashcards

1
Q

Coding Regions

A

Regions of DNA that contain genes that encode proteins.

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2
Q

Noncoding DNA

A

Regions of DNA that do not code for proteins but has instructions for tRNA, rRNA, regulatory DNA/RNA, and structural DNA

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3
Q

What are the 3 main RNA?

A

mRNA - messenger RNA

tRNA - transfer RNA

rRNA - ribosomal RNA

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4
Q

mRNA - messenger RNA

A

Coding RNA. template for protein synthesis taken from DNA

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5
Q

tRNA - transfer RNA

A

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

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6
Q

rRNA - ribosomal RNA

A

RNA component of small and large ribosomal subunits

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7
Q

What are the important process of protein synthesis? Explain briefly how they contribute

A

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

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8
Q

What happens if there are errors during replication, transcription, or translation?

A

Dysfunctional Proteins

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9
Q

What are the ribosomal subunits and when do they combine?

A

Small ribosomal subunit
Large ribosomal subunit
Unite to form a ribosome at the start of translation

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10
Q

What are ribosomes? What do they do?

A

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

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11
Q

Where can ribosomes form? (x4)

A
  1. Floating free in cytosol
  2. Within mitochondria
  3. Near/On cytosolic side of RER
  4. Near/On cytosolic side of outer nuclear membrane
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12
Q

Describe how the ribosome forms and how it reads mRNA

A

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

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13
Q

Polyribosomes

A

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

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14
Q

What makes polyribosomes beneficial?

A

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

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15
Q

Can ribosomal subunits be seen in TEM or LM?

A

No

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16
Q

How can we visualize ribosomes?

A

TEM. They appear as e- dense dots and polyribosomes look like spirals or clusters.

LM. Ribosomes contribute to basophilia of cytoplasm

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17
Q

What are the functions of the rough endoplasmic reticulum?

A

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.

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18
Q

Where are ribosomes and polyribosomes located on RER?

A

Cytosolic side

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19
Q

Describe the structure of the RER

A

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

20
Q

Where is RER extensive?

A

In cells specialized for protein secretion. It will appear in TEM as big stacks of flat sacs

21
Q

What are the functions of the Golgi apparatus?

A

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”

22
Q

Describe the structure of the Golgi apparatus?

A

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)

23
Q

Describe movement of protein through Golgi?

A

RER - CGN - Medial - TGN - destination

24
Q

Which way does the cis side curve on the golgi?

A

Convex

25
Q

Which way does the trans side of the golgi curve?

A

Concave

26
Q

Can Golgi’s be resolved in LM?

A

Yes! But need a special stain

27
Q

Golgi ghosts

A

Negative staining rxn in H&E - golgi is uncharge so it is not stained by either H or E

Cells with lots of protein secretion have basophilic cytoplasm (lots of RER) and lots of unstained Golgis which creates ghostly outline

28
Q

What are proteins that quality check the protein and help with initial folding?

A

Chaperonins (chaperone proteins)

29
Q

How and where are ribosomal subunits assembled?

A

DNA is transcribed to rRNA in nucleolus
The small and large ribosomal subunits exit the nucleus as separate entities and travel through cytosol in search of mRNAs

30
Q

Where does translation NEVER occur?

A

The nucleus

31
Q

What protein governs the ribosomal subunit assembly process in the nucelolus?

A

Nucleolin

32
Q

What is the function of the small ribosomal subunit?

A

Has binding sites for mRNA and tRNA. Ensures the correct pairing between mRNA codon and tRNA anticodon

33
Q

What is the function of the large ribosomal subunit?

A

Has enzymes that catalyze peptide bond formation

34
Q

What proteins are made on the surface of the outer nuclear membrane by ribosomes? Where are they sent?

A

Integral membrane proteins for nuclear envelope - Inner and outer nuclear membranes

35
Q

What proteins are made in the mitochondria by ribosomes? Where are they sent?

A

Proteins specific to the mitochondria - Stay in mitochondrion or its membranes

36
Q

What proteins are made in the cytosol by ribosomes? Where are they sent?

A

All not destructive so not delivered in vesicles
1. Cytoskeletal proteins - stay in cytosol

  1. Peripheral membrane proteins - stay in cytosol
  2. Proteins used in nucleoplasm and nucleolus - Nucleus via membrane transport through nuclear pores
  3. Proteins used in most organelles’ lumens - Organelles via membrane transport
37
Q

What proteins are made on the surface of the RER by ribosomes? Where are they sent? Where are they kept?

A

All of these are kept in the RER, Golgi, or in a vesicle from the moment they are made to protect the cell

Proteins that will be secreted - Outside the cell

Lysosomal proteins - lysosomes and late endosomes

Integral membrane proteins for the cell membrane and cytoplasmic organelle membranes - inserted into a membrane (many are receptors that can bind cytoplasmic structures)

38
Q

What proteins carry the proteins synthesized in the cytosol?

A

Translocator proteins

39
Q

What are the basic steps of protein synthesis in the RER?

A

Ribosomes on RER surface translate mRNA into polypeptide chain

RER sequesters the chain into its lumen as its growing

Chaperonins in the RER lumen, check, modify, and fold the new protein

Goligi further modifies the protein, sorts it, and pack it into a vesicle for shipment

40
Q

How does initial translation occur near the RER?

A

mRNA that needs to be translated at RER includes an RER specific signal sequence

The signal sequence encodes a single peptide that binds an RER specific signal recognition particle in the cytosol (SRP)

SRP binds to receptor in RER membrane - brings ribosome and chain close

Opens pore in RER membrane - polypeptide chain is fed through a pore and into the lumen of RER cistern

41
Q

Co-translational Translocation

A

One end of the polypeptide chain is being pulled into the RER lumen while the other end is still being assembled at the RER surface

42
Q

What happens after the entire polypeptide chain is inside the lumen of the RER cistern?

A

Post-translational modification in the RER lumen.

Initial (core) glycosylation - an oligosaccharide is attached

Protein folding - moderated by chaperone proteins and resident enzymes of RER lumen

43
Q

What protein modifications occur within the Golgi?

A

Glycosylation

Sulfation

Phosphorylation

Proteolysis

44
Q

Glycosylation

A

Addition of carbohydrate to protein

45
Q

Sulfation

A

Addition of sulfur to protein

46
Q

Phosphorylation

A

Addition of phosphate to protein

47
Q

Proteolysis

A

Cleavage of peptide bonds

FoundSci I Unit 3 (13 decks)

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