Chapter 1 demo Flashcards
(11 cards)
What are the three types of RNA and their functions?
mRNA (messenger RNA): Carries genetic information from DNA to ribosomes.
rRNA (ribosomal RNA): Forms the ribosome and helps catalyze protein synthesis.
tRNA (transfer RNA): Delivers specific amino acids to ribosomes during translation.
Why is the genetic code considered universal and degenerate?
Universal: The same codons specify the same amino acids in all organisms.
Degenerate: Multiple codons can code for the same amino acid.
What are the steps in gene expression?
- Transcription (in the nucleus)
RNA polymerase binds to the promoter region of a gene.
DNA is unwound, and one strand is used as a template.
Complementary RNA nucleotides pair with the template strand, forming pre-mRNA. - RNA Processing (post-transcriptional modification in eukaryotes)
Introns (non-coding regions) are removed by spliceosomes.
Exons (coding regions) are spliced together to form mature mRNA.
A 5’ methyl cap and a poly-A tail are added to protect from enzyme attack and stabilise
3.Translation (at the ribosome in the cytoplasm)
Ribosome reads mRNA codons.
tRNA brings specific amino acids to the ribosome.
Peptide bonds form between amino acids, creating a polypeptide chain.
What are the key regions of a gene?
Exons: Coding regions that determine the amino acid sequence of a protein.
Introns: Non-coding regions that are removed during RNA processing.
Promoter: The DNA sequence where RNA polymerase binds to initiate transcription.
-regulates gene expression
Operator (in prokaryotic genes): A regulatory sequence where repressor proteins can bind to control gene expression.
regulatory region:
codes for a repressor protein controls of operator gene. when a repressor protein binds to the operator it blocks the promoters binding site for RNA polymerase and prevents transcription
How does the trp operon regulate gene expression in prokaryotes?
When tryptophan is absent, the repressor is inactive, and transcription occurs. Enzymes needed for tryptophan synthesis are produced.
When tryptophan is present, it binds to the repressor protein, activating it. The repressor binds to the operator, blocking RNA polymerase and stopping transcription.
What are the four levels of protein structure?
Primary: The linear sequence of amino acids in a polypeptide.
Secondary: Alpha-helices and beta-pleated sheets stabilized by hydrogen bonds.
Tertiary: The overall 3D structure of the protein due to interactions between R groups (e.g., ionic bonds, disulfide bridges, hydrophobic interactions).
Quaternary: Multiple polypeptide chains interacting to form a functional protein (e.g., hemoglobin).
What is a proteome?
The complete set of proteins expressed by a cell, tissue, or organism at a given time.
What is the role of the rough ER, Golgi apparatus, and vesicles in protein export?
Rough Endoplasmic Reticulum (RER):
-Ribosomes on the RER synthesize proteins.
-proteins intended for export from the cell at the ribosomes attached to the rough ER. From there they move through the channel network of the lumen of the rough ER toward Golgi
Golgi Apparatus:
-Further modifies proteins .
-Sorts and packages proteins into vesicles.
-proteins are delivered the cis side of the Golgi from the RER and they move through the Golgi
Vesicles:
-proteins are released from the Golgi in vesicles that bud off from the trans face
- the vesicles bud off the Golgi can diffuse to their target location over very short distances over long distances they are carried by motor proteins along the microtubules of cell cytoskeleton
-Transport proteins to their final destinations (either within the cell or for secretion via exocytosis).
features of a nucleic acids
5’ end=phosphate end
3’ end=hydroxyl end (pentose sugar)
A–T= 2 Hbonds
G–C= 3 Hbonds
operons
linked structural genes with a common promoter and operator that is transcribed as a single unit. Its expression is controlled by regulator genes that produce repressor protein
