Cell Bio Unit 1

hsp-70

binds hydrophobic portions, prevents aggregation

hsp

heat-shock protein (dramatically increase after brief exposure to elevated temperatures)

HSP-60

When cap is added, the barrel structure
changes to tuck away the hydrophobic residues and expose hydrophilic regions. This promotes the protein to
bury its hydrophobic regions and fold properly

Protein disulfide isomerase (PDI)

Located in the endoplasmic reticulum
• Disulfide bonds are typical of secreted proteins
and some membrane proteins
• Cytosol = reducing environment → maintains
cysteine in its reduced form (-SH)

Transcription

The process by which DNA is copied into a primary RNA transcript in the nucleus.

RNA processing

Modifications including 5' capping, splicing out introns, and 3' polyadenylation to produce mature mRNA.

Translation

The decoding of mRNA into a polypeptide chain by ribosomes in the cytoplasm.

mRNA Export

The transport of processed mRNA from the nucleus to the cytoplasm through nuclear pores.

ER Signal Sequence

A short peptide that directs the ribosome to the rough ER for protein synthesis.

Targeting Sequence

Specific amino acid sequences that direct proteins to organelles like mitochondria, peroxisomes, or chloroplasts.

Secretory Pathway

The route proteins take from the ER through the Golgi apparatus to the plasma membrane or extracellular space.

Primary structure

The linear sequence of amino acids in a polypeptide chain.

Secondary Structure

Local folding patterns such as α-helices and β-sheets stabilized by hydrogen bonds.

Tertiary Structure

The overall 3D shape of a single polypeptide, formed by interactions among side chains.

Quaternary Structure

The assembly of multiple polypeptide subunits into a functional protein complex.

Polar amino acids

Amino acids with side chains that can form hydrogen bonds; includes Ser, Thr, Asn, Gln, Tyr.

Nonpolar Amino Acids

Amino acids with hydrophobic side chains; includes Val, Leu, Ile, Met, Phe.

Charged Amino Acids

Includes positively charged (Lys, Arg, His) and negatively charged (Asp, Glu) side chains.

Co-translational Folding

Folding of the N-terminal domain begins while the polypeptide is still being synthesized.

Molecular Chaperones

Proteins that assist in the proper folding of other proteins without being part of the final structure.