Molecular and Cell Biology Lecture 13

What does the basigin gene code for?

2 isoforms

both isoforms are ___________

transmembrane glycoproteins

What are isoforms?

protein variants

What are transmembrane glycoproteins?

embedded proteins that extend from the inner to the outer surfaces of the plasma membrane

What are glycoproteins?

protein that is attached to a carbohydrate

What are cell adhesion molecules?

proteins embedded in the plasma membrane that help cells stick to each other and to the surrounding extracellular matrix

What is the order of the central dogma (flow of genetic information)?

Genes are made of DNA, DNA is transcribed into mRNA, mRNA is translated into protein.

Transcription

process through which mRNA forms on a template of DNA

Exon

sequence present in protein-coding mRNA after completion of splicing

Intron

non-protein-coding intervening sequences that are spliced from mRNA during RNA processing

Splicing

the process of removing introns and reconnecting exons in a pre-mRNA

What 2 things are added to form mature mRNA?

5' guanine cap and 3' poly-A tail

What is a 5' guanine cap?

A modified guanine nucleotide that attaches to the 5' end of the pre-mRNA

What is a 3' poly-A tail?

A long chain of adenine nucleotides that is attached to the 3' end of the pre-mRNA

What is translation?

process through which RNA directs the protein's formation

Proteins are made of _________________

polypeptide chains

Polypeptide chains are made of _________

amino acids

A ______________ is a covalent bond that connects adjacent amino acids in a polypeptide

peptide bond

In their structure, each amino acid has...

An amino group, carboxyl group, and central carbon

peptide bonds form between two ______________

amino acids

how are peptide bonds formed? (what type of rxn)

dehydration reaction

what specific groups between amino acids are peptide bonds formed by?

carboxyl group and amino group

polypeptide

many peptide bonds

what end of the amino acid is N-terminus?

amino end

what end of the amino acid is C-terminus?

carboxyl end

Where is N-terminus positioned?

front

Where is C-terminus positioned?

end

Each _______ of an mRNA molecule "codes" for an amino acid or Stop

codon

what are three consecutive nucleotides in mRNA that specify the insertion of an amino acid or the release of a polypeptide chain during translation?

codons

steps of translation (in order)

initiation, elongation, termination

what happens during initiation

initiation complex forms

what happens during elongation

polypeptide is translated from mRNA

what happens during termination

ribosome finds stop codon and polypeptide is released

during which step is polypeptide synthesized?

elongation

__________ synthesizes polypeptides

ribosomes

what are the subunits during elongation, composed of?

proteins and ribosomal RNA

1. Charged tRNA enters the A-site of the ribosome, matching its anticodon to the mRNA codon.

2. peptide bond forms between the amino acid in the A-site and the growing polypeptide in the P-site.

3. The polypeptide chain transfers to the tRNA in the A-site.

4. The ribosome shifts 3 nucleotides (1 codon) along the mRNA in the 3' direction.

5. The now uncharged tRNA moves from the P-site to the E-site and exits the ribosome.

6. The tRNA carrying the polypeptide moves from the A-site to the P-site.

7. A new charged tRNA w/ the correct anticodon enters the A-site, and the cycle repeats.

steps of elongation

______________ charged w/ an amino acid migrates to ribosome

transfer RNA (tRNA)

tRNA enters the _______

A-site

_________ of tRNA is complementary to the codon of mRNA

anticodon

uncharged tRNA moves from _______ to ______ and exits ribosome

P-site, E-site

tRNA attached to polypeptide moves from _______ to _______

A-site, P-site

next tRNA w/ correct anticodon binds to codon in ______.

A-site

a variant of a protein that differs slightly from another version

isoform

isoforms can arise from _______ __________

alternative splicing

different exons are combined to create distinct proteins from the same gene

alternative splicing

endoplasmic reticulum (ER)

membranous cell organelle outside nucleus

rough ER

ribosome embedded in ER membrane

secretory and membrane bound proteins synthesized at _________

Rough ER

Other proteins (not secretary and membrane bound proteins) are synthesized by freely floating __________ in the cytoplasm.

ribosomes

vesicles carrying proteins bud from the _______________________________

endoplasmic reticulum (ER)

proteins are sorted, tagged with/ carbohydrates (____________), and packaged into ____________ at the _______________

glycosylation, transport vesicles, Golgi apparatus

a transport vesicle from the Golgi apparatus delivers a protein to ______________________________

the plasma membrane

a phospholipid bilayer w/ embedded proteins

plasma membrane

embedded proteins that extend from the inner to the outer surfaces of the plasma membrane

transmembrane proteins (or integral proteins)

glycoprotein

a protein that is attached to a carbohydrate

cell adhesion molecule

proteins that help cells stick to each other and to the surrounding extracellular matrix

cell adhesion molecules are embedded in the __________________

plasma membrane

homotypic binding

between two of the same molecule

heterotypic binding

between two different molecules

the basigin gene ______ for ______ (how many) ________.

codes, 2, isoforms

both isoforms are ______________________

transmembrane glycoproteins

both isoforms function as ________________

cell-adhesion molecules