Cell Signaling
What is a ligand?
A ligand is a signaling molecule.
What is the function of a kinase versus a phosphatase?
A kinase is an enzyme that phosphorylates (adds a phosphate group to) a protein.
A phosphatase is an enzyme that dephosphorylates ( takes a phosphate group off of) a protein.
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 is apoptosis?
Apoptosis is programmed cell death (can be a response in cell signaling).
What are the main functions of microtubules?
- Transport
- Division
- Structure
What are telomeres? What is their purpose?
Bonus: What enzyme extends telomeres?
Telomeres are protective caps at the ends of chromosomes made of repetitive DNA sequences. They prevent the loss of DNA at chromosome ends.
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.
Cyclic AMP and Calcium Ions are an example of what in signal transduction?
Signal amplifiers
- They amplify the initial signal to give more of a robust response.
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 the difference between a somatic and germline mutation?
A somatic mutation occurs in body cells (may be involved in cancer) but is not passed onto offspring. A germline mutation occurs in the gametes and is passed onto offspring.
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.
What is the role of phosphodiesterase in G Protein Coupled Receptor signaling?
Phosphdiesterase converts cAMP to AMP, which stop stops the phosphorylation and activation of the target protein (stopping response).
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.
Describe the function of these 3 DNA replication enzymes:
1) Helicase
2) Topoisomerase
3) Ligase
Helicase: Unwinds parental DNA
Topoisomerase: Relieves tension on replication fork
Ligase: Joins DNA fragments
Describe the difference between nonsense mutations and silent/synonymous mutations
A nonsense mutation introduces a premature stop codon and a silent/synonymous mutation changes the nucleotide sequence into a sequence that codes for the same amino acid (ultimately, no protein change).