7.3 Flashcards by Charlotte Favre

When does translation start

when mature mRNA binds to a small ribosomal subunit at the mRNA binding site

How well did you know this?

Not at all

Perfectly

what is the initiation codon for mRNA

AUG (methionine) which can be like to the initiator tRNA

How well did you know this?

Not at all

Perfectly

what happens when a tRNA molecule binds to its corresponding amino acid

it forms a complex called an aminoacyl- tRNA

How well did you know this?

Not at all

Perfectly

what happens at initiation of translation

mRNA binds to a small ribosomal subunit

the anticodon of the initiator tRNA binds to the codon of the mRNA

finally, the large ribosomal subunit joins to complete the assembly o the translation complex

How well did you know this?

Not at all

Perfectly

what are the three different sites

E P and A

How well did you know this?

Not at all

Perfectly

what do the sites E P and A stand for

Exit

peptide - tRNA

Aminoacyl - tRNA binding site,

How well did you know this?

Not at all

Perfectly

what is the E site

where the tRNA moves after transferring its amino acid to the growing polypeptide chain, ready to exit the ribosome

How well did you know this?

Not at all

Perfectly

what is the A site

where the incoming tRNA with its attached amino acid binds, while the P site is where the tRNA from the A site moves after its amino acid forms a peptide bond with the growing polypeptide chain

How well did you know this?

Not at all

Perfectly

What is the P site

where the TRNA from the A site moves after its amino acid forms a peptide bond with the growing polypeptide chain

How well did you know this?

Not at all

Perfectly

where is the tRNA holding the growing polypeptide chain found

at the P site

How well did you know this?

Not at all

Perfectly

what takes place during elongation

involves a repeated cyclic of events

a new aminoacyl tRNA comes in and binds to the A site. this carries a specific amino acid that matches to the codon on the mRNA and the anticodon on the rRNA

then the new amino acid is joined to the existing polypeptide chain by a peptide bond

the tRNA that was bound to the polypeptide chain is now ready to be recycled as it is no longer bound to an amino acid

the ribosome translocates the tRNA holding the growing amino acid chain from the A site to the P site, this shifts the empty tRNA to the E site where it can leave or be recycled and the process starts again until the ribosomes reaches the termination codons

UAG

How well did you know this?

Not at all

Perfectly

what is the final stage of termination

a release factor binds in the A site and causes the disassembly of the components of the translation complex. all of these components can be reused for another translation complex,

How well did you know this?

Not at all

Perfectly

What is the first event to take place in translation in eukaryotes?

The small subunit of the ribosome recognises and attaches to the initiator codon of mRNA

How well did you know this?

Not at all

Perfectly

During which stage of translation does a release factor bind to the ribosome?

termination

How well did you know this?

Not at all

Perfectly

what are ribosomes consisted of

a small and large subunit with three bindings sites for tRNA molecules

How well did you know this?

Not at all

Perfectly

what is tRNA

a single stranded RNA molecule that folds on itself to form a cloverleaf shaped structure with double stranded regions and three hairpin loops.

one of the loops contains a sequence called the anticodon which binds to the mRNA conons.

each tRNA has a corresponding amino acid attached to the 3’ end of CCA.

How well did you know this?

Not at all

Perfectly

what is found at the 3’ end of the tRNA

CCA

How well did you know this?

Not at all

Perfectly

what bond forms between the amino acid and CCA

ester bond

How well did you know this?

Not at all

Perfectly

The triplet of bases at the amino acid binding site of tRNA is:

5’ CCA 3’

How well did you know this?

Not at all

Perfectly

How many permanent loops does a tRNA molecule have?v

How well did you know this?

Not at all

Perfectly

What describes the subunits of eukaryotic ribosomes?

A small subunit which binds mRNA and a large subunit with three tRNA binding sites.

How well did you know this?

Not at all

Perfectly

what is knowns as the tRNA activating enzyme

the enzyme aminoacyl tRNA synthetase

How well did you know this?

Not at all

Perfectly

how many different tRNA activating enzymes are there

20 for each 20 different amino acids

How well did you know this?

Not at all

Perfectly

how does the specificity of the tRNA and the matching anticodon happen

based on the match between the shape of the particular amino acid and the enzyme

How well did you know this?

Not at all

Perfectly

Aminoacylation of a tRNA molecule

hydrolysis of an ATP molecule provides energy fro the reaction ATP + H2O - AMP and PP (pyrophosphate) when phosphates are removed from ATP molecules, energy is released for use by the cell

what is a tRNA called once is is attached to an amino acid

it is called a charged tRNA molecule

what are free ribosomes

produce proteins use mainly within the cell

what are bound ribosomes

synthesis proteins mainly meant for recreation or for use in lysosomes

where are proteins synthesized on the bound ribosomes usually found

in the ER, Golgi apparatus, lysosomes and plasma membrane

when does translation start

once the mRNA attaches itself to the ribosome

what recognizes the signal sequence

signal recognition particle (SRP)

what does the SP do once recognizing the sequence

it binds to the SRP recognition protein on the endoplasmic reticulum allowing the polypeptide to enter the rough ER as it grows in length

what happens when translation ends

the translation complex disassembles, the whole polypeptide is taken into the RER

where does post translational modifications take place

in the lumen of the ER

where are free ribosomes usually found or destined to function in

the mitcohondria, chloroplasts, cytoplasm, nucleus of the cell

where do translation and transcription take place in bacteria

in the same place due to the absence fo a nuclear membrane.

what is a polysome

a structure formed where multiple ribosomes can attach to the same mRNA to produce proteins at a faster rate

What is a function of the signal recognition particle (SRP)?

To help translocate polypeptides across the ER membrane

When translating secretory or membrane proteins, ribosomes are directed to the ER membrane by:

A signal-recognition particle that brings ribosomes to a receptor protein in the ER membrane

Actin and myosin are proteins found in muscle cells. Where would they be synthesised?

Free ribosomes in cytoplasm of muscle cells

how many different amino acids make up a polypeptide

around 20

what is the primary structure of a protein

the sequence and the number of amino acids in the polypeptide

what is the primary structure of a protein

the sequence and the number of amino acids in the polypeptide

what bonds form between amino acids in poly peptides in the primer structure

peptide bonds

what is the secondary structure

formed when the polypeptide chain folds back on itself into a helices or b pleated sheets

how are secondary structures stabilized

by hydrogen bonds between the -NH groups) and the - C=O groups

what is the tertiary structure

further folding, forming a 3 dimensional shape

how is the tertiary structure stabilized

by interactions between the R groups

what r groups will associate together

polar as they are all hydrophilic non polar as they are hydrophobic

what types of interactions happen between polar R groups

ionic interactions between acidic and basic R groups or hydrogen bonds

what bonds form between r groups that contain sulfur

covalent bond also known as disulfide bridges

what amino acids contain sulphur in their r groups

cysteine and methionine

where would covalent bonds form in amino acids

between r groups that contain sulphur

where are the hydrophilic amino acids located in tertiary structures

located on the outside of the protein and the hydrophobic amino acids are located in the center of the protein away from the watery cytoplasm

what is an example of a tertiary strcucture

lysozyme

what bonds appear when the r group contains sulfur

disulfide bonds

what are quaternary structures

more than one polypeptide chains,

example of quaternary structure

hemoglobin - 2 a chains, 2 b pleated chains and four heme groups

what is attached to quaternary proteins

non protein units called a co factor that is tightly attached,

what is the co-factor in hemoglobin

heme - the iron containing prosthetic group

what is a conjugated protein

a protein with a prosthetic groups attached

What aspects of protein structure are stabilised or assisted by hydrogen bonds?

secondary , tertiary and quaternary

Tertiary structure of proteins depends primarily on which structural component of amino acids?

r groups

what is said about termination codons found on mRNA

there are no anticodons that complement termination codons found on mRNA

how many nucleotides code for one specific amino acid

where is initiator tRNA never found in translation

at the A binding site

whats to tRNA activating enzymes do

they bind to the amino acid to the corresponding tRNA by hydrolysis of ATP and gaining one phosphate molecule. The phosphate molecule is released from App through hydrolysis and then added to the enzyme

What does charging tRNAs involve

it is accompanied by pyrophosphate release during the charging cycle

where are amino acids joined together during translation

at the P site by a peptide bond

where does the second tRNA pair with the next codon

at the A site