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What is quorum sensing?
A process where cells detect and respond to signaling molecules (ligands) to coordinate behavior.
What are the types of chemical signaling?
1. Autocrine: Cell targets itself.
2. Paracrine: Targets nearby cells.
3.Gap Junctions/Plasmodesmata: Direct cytoplasmic connections between adjacent cells.
4. Endocrine: Targets distant cells through the bloodstream.
What happens during the response phase of signaling?
The cell changes its activity or function in response to the signal.
What happens in signal reception?
A ligand binds to a receptor, causing a conformational change that initiates signaling.
What are the four types of receptors?
1. Ligand-Gated Ion Channels: Open/close ion channels when ligands bind.
2. G-Protein Coupled Receptors (GPCRs): Activate G-proteins, leading to signal cascades.
3. Receptor Tyrosine Kinases (RTKs): Activate phosphorylation cascades using ATP.
4. Intracellular Receptors: Nonpolar ligands act as transcription factors.
What is transduction?
The process of transferring a signal from the receptor to target molecules inside the cell.
What is signal amplification?
A single ligand-receptor interaction activates multiple downstream molecules.
What are second messengers? Give examples.
Small molecules like cAMP and ions (e.g., calcium) that propagate the signal.
What are phosphorylation cascades?
Processes where kinases phosphorylate proteins, altering their activity.
What are the key cellular responses to signals?
Gene Expression: Activates transcription of specific genes.
Enzyme Activation: Turns on enzymes like kinases.
Apoptosis: Programmed cell death.
What are the two types of feedback mechanisms?
Negative Feedback: Reduces the pathway’s output to restore balance.
Positive Feedback: Amplifies the pathway’s response.
What are the three main reasons cells divide?
1. Asexual reproduction.
2. Growth and development.
3. Tissue renewal.
What is the genome?
All the DNA in a cell.
What is a chromosome?
A DNA-protein complex organized for division.
What are homologous chromosomes?
Chromosome pairs containing the same types of genes but possibly different alleles.
What are sister chromatids?
Identical copies of a chromosome, joined at the centromere.
What is the cell cycle?
The series of events that cells go through as they grow, replicate DNA, and divide.
What are the main phases of the cell cycle?
1. Interphase: Cell growth and preparation for division.
2. Mitotic (M) Phase: Includes mitosis and cytokinesis.
What steps are in interphase
G1, S, and G2
G₁ Phase
Cell grows and performs metabolic activities.
S Phase
DNA replication occurs.
G₂ Phase
chromosomes tightly coil using motor proteins, centrioles replicate, tublin synthesis occurs
What are the steps of mitosis?
prophase, pro metaphase, metaphase, anaphase, telophase
prophase
Chromosomes condense; spindle forms.
Prometaphase
Chromosomes attach to spindle microtubules; nuclear envelope disassembles.
Metaphase
Chromosomes align at the metaphase plate
Anaphase
Sister chromatids separate and move to opposite poles.
Telophase
Nuclear envelopes reform, chromosomes decondense.
What is cytokinesis?
Cytokinesis is cytoplasmic division.
How does it differ in animal and plant cells?
Animal cells: Cleavage furrow constricts the membrane.
Plant cells: Vesicles form a cell plate, which matures into a cell wall.
What is binary fission?
The process by which prokaryotes divide, involving chromosome replication and division into two cells.
What is the function of checkpoints in the cell cycle?
Checkpoints regulate progression through the cell cycle, ensuring proper DNA replication and division.
G₁ Checkpoint
Checks if the cell is ready for DNA replication, if not send it back to G0
G₂ Checkpoint
Verifies proper DNA replication.
M Checkpoint
Ensures all chromosomes are attached to microtubules.
What happens if checkpoint regulation fails?
Uncontrolled cell division can occur, leading to cancer.
How do “checkpoints” work in the cell
the checkpoints are regulated by proteins
what are the 2 main check point proteins coding genes
tumor suppressor gene, proto - oncogenes
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