Protein Synthesis Flashcards
(30 cards)
What is protein synthesis?
The making of protein using amino acids and the code in mRNA.
Where does protein synthesis occur?
Occurs in the cytoplasm on the surface of ribosomes.
What are ribosomes made of?
Ribosomes are made from RNA folded over on itself.
What are some features of RNA?
- Single-stranded.
- Has the base uracil instead of thymine.
Has the sugar ribose.
When does protein synthesis occur?
Protein synthesis is continually occurring in living cells at all times.
What are some examples of when protein synthesis is required?
Metabolic processes that make hair, skin, nails, the linings of the digestive and respiratory systems, tissues that make hormones and enzymes, and white blood cells that make antibodies all require protein synthesis.
What kind of process is protein synthesis?
An anabolic process - it involves small molecules (amino acids) being joined together to make a large molecule (protein).
When is the only time that DNA leaves the nucleus?
During mitosis and during this stage of the cell cycle the DNA is not available for protein synthesis.
What are the three stages of protein synthesis?
- Transcription
- Translation
- Protein folding
What is transcription?
The making of mRNA using a DNA template.
What is translation?
The making of protein using the code in mRNA.
Where does transcription occur?
Nucleus.
What happens to enzymes during transcription?
Enzymes unwind and break the hydrogen bonds between the strands of DNA, exposing nucleotide bases only at the site of the gene to be transcribed.
What is the anabolic enzyme that synthesises mRNA and how?
RNA polymerase. RNA polymerase synthesises mRNA using one of the strands of DNA. Free-floating RNA nucleotides from the cytoplasm bond with their complementary nucleotides on the DNA.
What is mRNA and what is its function?
Messenger RNA. When a cell wants to produce a protein, a chemical message, in the form of RNA, is sent to a ribosome. This is mRNA.
What happens once the RNA polymerase enzyme has transcribed the entire gene?
It detaches from the DNA and moves back to the beginning again, ready for another cycle of transcription.
What happens to the newly synthesised piece of mRNA?
It detaches from the RNA polymerase and diffuses from the nucleus out into the cytoplasm, where it interacts with a ribosome.
Where does translation occur?
Translation occurs on ribosomes in the cytoplasm.
What is rRNA and what is it composed of?
rRNA is ribosomal RNA, and it is composed of two RNA subunits: a small rRNA subunit and a large rRNA subunit. This structure allows the peice of mRNA to slide easily thought the ribosome.
What is a triplet or codon?
A sequence of three bases present on mRNA that codes for one amino acid.
How does mRNA interact with rRNA?
mRNA interacts with rRNA in the ribosome and slides throught it.
Every codon on mRNA will tell the ribosome to carry out one of the following…
- Start codon
- Amino acid
- Stop codon
What is a start codon?
A start codon is a sequence of three bases (such as AUG) present on mRNA that tells the ribosome to begin assembling a protein.
What is an amino acid?
Codons follow the start codon and tell the ribosome to add on a specific amino acid.
