bIOL exam 3

Mitogen-Activated Protein Kinase

• Enter the nucleus

• Activate transcription factors

• Regulate gene expression

ligase

helicase

girase

primase

a.) Seals the "nicks" or gaps in the sugar-phosphate backbone of DNA.

b.) Unzips the DNA double helix at the replication fork

c.) Relieves tension ahead of the replication fork

d.) syntehsizes a short RNA

dna polymrease I

Remove RNA primers (from Okazaki fragments on the lagging strand

2. Replace primers with DNA nucleotides

dna polymerase III

Adds nucleotides to the growing DNA strand

first teps of g protien

• ligand binds to a GPCR on the cell surface.

• GPCR undergoes a conformational change and activates a G protein by exchanging GDP for GTP

second steps

• Effector proteins (like adenylate cyclase) trigger cellular responses via second messengers (e.g., cAMP).

• The signal is turned off when GTP is hydrolyzed to GDP, and the subunits reassociate.

phosphrylkation

• Signal binds receptor – A ligand (like a hormone) activates a receptor.

• Kinase activation – The receptor or nearby protein activates a protein kinase (an enzyme).

• Phosphorylation – The kinase adds a phosphate group (PO₄³⁻) to a target protein.

• Protein changes – Phosphorylation activates or inactivates the target protein.