Cell Signaling
What is a ligand?
A ligand is a signaling molecule.
1. Ligand binding opens channel
2) Ions flow
3) Response occurs
What is the main function of the extracellular matrix?
Provides structural support, cell adhesion, and signaling.
Cyclin-CDK complexes regulate the progression of the cell cycle. Cyclins bind CDKs (activating them), which drives progression through the cell cycle stages.
What enzyme unwinds DNA during replication?
Helicase
What is the role of a receptor protein in cell signaling?
A receptor protein binds a ligand and coverts that external signal into a cellular response (by changing shape and becoming activated).
What happens to a receptor when a ligand binds to it?
The receptor changes shape (called a conformational change) and becomes activated.
What are the main functions of microtubules?
- Transport
- Division
- Structure
What are telomeres? What is there purpose?
Bonus: What enzyme extends telomeres?
Bonus: Telomerase extends telomeres.
Why does the lagging strand require Okazaki fragments?
Because DNA polymerase only works 5' to 3', the lagging strand must be built in short segments.
List the correct order of the 4 steps of cell signaling.
1) Receptor activation
2) Signal transduction
3) Response
4) Termination
In the G-Protein Coupled Receptor pathway, what molecule replaces GDP to activate the G protein?
GTP
What is one key difference between microfilaments and microtubules?
Microfilaments: Thin, actin, movement
Microtubules: Thicker, tubulin, transport/division
Put the 5 stages of mitosis in order.
1) Prophase
2) Prometaphase
3) Metaphase
4) Anaphase
5) Telophase
What type of mutation shifts the reading frame of a gene?
Frameshift mutation
Describe the differences between the 4 kinds of cell signaling: Endocrine, Paracrine, Autocrine, and Contact-Dependent
Endocrine: Long distance signaling via bloodstream.
Paracrine: Short distance signaling via diffusion to nearby cells.
Autocrine: Cell signals to itself.
Contact-Dependent: Cells signal to adjacent (touching) cells.
A mutation prevents receptor dimerization. Which receptor type is affected?
Receptor kinases (dimerization is a major step in this pathway).
Which type of cytoskeletal filament is primarily made of thin actin?
Microfilaments
What are the 3 major cell cycle checkpoints and what phases do they occur in?
G1: DNA damage check
G2: Replication complete check
M: Spindle attachment
What is base excision repair?
A DNA repair mechanism where single damaged bases are removed and are replaced using DNA polymerase and ligase.
True or False: Nonpolar ligands bind to transmembrane receptors.
Explain your answer.
False
Polar ligands bind to cell surface (transmembrane) receptors, while nonpolar ligands bind to intracellular receptors. Polar ligands cannot cross the hydrophobic (nonpolar) cell membrane.
A signaling molecule binds to a receptor on the cell surface. Shortly after, ion channels open and ions rapidly move across the membrane.
What type of receptor is most likely?
Ion channel-linked receptor
Differentiate between kinesin versus dynein motor proteins.
Kinesin: Motor protein moves cargo towards plus end of microtubule using ATP.
Dynein: Motor protein moves cargo to minus end of microtubule using ATP.
1) Helicase
2) Topoisomerase
3) Ligase
Helicase: Unwinds parental DNA
Topoisomerase: Relieves tension on replication fork
Ligase: Joins DNA fragments
What is the complementary DNA strand for the sequence 5' ATG CCG TAA 3'?
3' TAC GGC ATT 5'