Unit 4: Cell Communication and Cell Cycle, AP Biology Flashcards
What is the relationship between insulin and glucagon in homestasis?
When blood glucose is too high, insulin is released to lower it by storing it as glycogen
When blood glucose is too low, glucagon is released to increase it by releasing glucose from storage
What is the relationship between calcitonin and PTH in homeostasis?
If blood calcium is too high, calcitonin is released by the thyroid to decrease calcium levels by turning calcium into bone and decreasing absorption by intestines + kidneys
If blood calcium is too low, PTH is released by the parathyroid to increase calcium levels by taking calcium from bones and increasing absorption by intestines + kidneys
What is binary fission?
The process of prokaryotes dividing
The prokaryote elongates until it is double its size, then pinches in and separates into two identical daughter cells
What is the cell cycle?
A series of events that takes place in eukaryotic cells as they grow and eventually divide
What are the four main stages of the cell cycle?
G₁, S, G₂ , and M
What is the G₁ phase in the cell cycle?
First growth phase where the cell grows larger, copies organelles, and makes molecular building blocks it will need later
What is the S phase in the cell cycle?
Second stage of the cell cycle where the cell creates a complete copy of its DNA in its nucleus
(also duplicates the centrosome, which helps separate DNA during the M phase)
What is the G₂ phase?
Third stage of the cell cycle where the cell grows more, makes proteins and organelles, and begins to reorganize itself to prepare for mitosis
What is the M phase?
The final stage of the cell cycle where the cell divides its DNA and cytoplasm to make two new cells
(two phases: mitosis and cytokinesis)
What is interphase in the cell cycle?
The first three stages (G₁ phase, S phase, and G₂ phase) that are in between the previous M phase and the next
Stages of the Cell Cycle
- G₁ phase: {{c1::Grows larger, copies organelles, and makes molecular building blocks}}
- S phase: {{c2::Copies the entire DNA in the nucleus and copies the centrosome}}
- G₂ phase: {{c3::Grows more, makes proteins and organelles, and reorganizes its contents for mitosis}}
- M phase: {{c4::Divides its DNA and cytoplasm to make two new cells}}
How long does it take for a cell to go through the cell cycle?
Varies based on the type of cell
(skin cells go very quickly, whereas nerve cells don't go through it at all as they are amitotic)
What is chromatin?
The material that makes up chromosomes and is made of RNA and DNA
(exists in all organisms other than bacteria)
What is prophase?
First phase of cell division where the chromosomes condense, the mitotic spindle starts to form, and the nuclear envelope breaks down
What is metaphase?
Second stage of cell division where the sister chromatids line up in the middle of the cell and prepare to split apart
(line up at the metaphase plate)
What is anaphase?
Third step of cell division where the sister chromatids move via the microtubules to opposite poles of the cell, leaving each pole with a complete set of chromosomes
Microtubules push the poles apart
What is telophase?
Fourth phase of cell division where the cell is nearly done dividing and the cell starts to re-establish its normal structures
(miotic spindle is broken down; two new nuclei form for each set of chromosomes; chromosomes decondense)
What is cytokinesis?
The division of cytoplasm during M phase to create two new cells
(creates a cleavage furrow in animal cells using a "drawstring" called actin; creates a cell plate in plant cells, since their cell walls prohibit them from bending)
What is a cell plate?
A structure in plant cells during cytokinesis that allows the plant cell to split
(constructed in the Golgi apparatus)
What is the cleavage furrow?
A groove formed in animal cells between the two daughter cells, that pinches the two cells apart during cytokinesis
What are kinetochores?
Protein complexes found on the centromere of each sister chromatid where the microtubules bind
Necessary for chromosome positioning and movement
What is the G₁ checkpoint?
A checkpoint between the G₁ and S phases where the cell checks if it...
- Size: is large enough
- Nutrients: has enough nutrients
- Molecular Signals: is receiving molecular signals (e.g., growth factors) from neighbors
- DNA Integrity: has undamaged DNA
What is the G₀ phase?
A resting state for cells where they are not actively dividing
(some cells stay here temporarily, while others stay here forever; cells who fail the G₁ checkpoint often move here until conditions improve)
What is the G₂ checkpoint?
A checkpoint between the G₂ and M phases, where the cell checks if...
- DNA integrity: any of the DNA is damaged
- DNA replication: all of the DNA was copied during the S phase
What happens if errors/damage is detected at the G₂ checkpoint?
The cell will pause and try to complete the DNA replication, or repair the replicated DNA
If the damage is irreparable the cell will die via apoptosis, which is important for preventing cancer
What is the spindle checkpoint (M checkpoint)?
A checkpoint during the M phase where the cell checks if all the sister chromatids are correctly attached to the spindle microtubules
(anaphase is irreversible, so this is important)
What is density-dependent inhibition?
A feedback mechanism that stops cells from growing when there are too many in a given area (they are too dense)
Cancer cells have often lost this, so they keep reproducing
What is a cyclin?
Important cell-cycle regulators that drive the cell-cycle forwards by interacting with cyclin-dependent kinases (Cdks)
(as cyclins attach to Cdks, the Cdks are activated and directed to target the next phase (e.g., M cyclins send Cdks to M phase targets, making the nuclear membrane break down))
What is negative feedback in hormones?
When a hormone attempts to inhibit more of that hormone from being produced
(when blood glucose is too high, the pancreas secretes insulin, which lowers the blood glucose level and stops the secretion of insulin)
What is positive feedback in hormones?
When a hormone promotes more of its secretion
What are microtubules?
Fundamental structures of the spindle apparatus that are essential for cell division
What are motor proteins?
Proteins in kinetochores that move chromosomes during anaphase in mitosis
(in animal cells they can also be used to pinch the cell in two and generate the cleavage furrow)
What are actin filaments?
Linear polymers that assemble at the cytokinesis site to generate the force to pinch the cell in two
Interact with myosin motor proteins
How do cells communicate?
Generating, transmitting, receiving, and responding to chemical signals
What is cell signaling?
Process of cells communication with each other in the body
(driven by the release of ligands which are detected by receptors)
What is a ligand?
Any type of signalling molecules that cells use to communicate
(detected by receptors)
What are receptors?
Proteins on cells that ligands bind to
(can be located on the cell membrane for hydrophilic ligands, or inside the cell for hydrophobic ligands that are small enough to cross the membrane)
What is direct cell-to-cell signaling?
Type of cell signaling that involves direct physical contact between cells during communication
(signaling molecules flow through water-filled channels; gap junctions in animal cells and plasmodesmata in plant cells)
What is paracrine signaling?
Type of signaling where cells are close to each other and release a short-lived signal that will induce changes in a nearby cell
(especially important during development; only works over short distances)
What is synaptic signalling?
Unique example of paracrine signaling, where nerve cells transmit ligands called neurotransmitters over the synapse
What is autocrine signaling?
Type of signaling where the cell signals to itself, releasing a ligand that binds to its own receptors
(in many cases a signal can be both autocrine and paracrine; important in cancer)
What is endocrine signaling?
Type of cell signaling where distant cells communicate using hormones that are transmitted through the bloodstream
Types of Signaling in Cells:
- Paracrine Signaling: {{c1::Nearby cells release a short-lived signal into a localized area}}
- Synaptic Signaling: {{c2::Type of paracrine signaling where nerve cells transmit neurotransmitters}}
- Autocrine Signaling: {{c3::The cell releases ligands that its own receptors detect}}
- Endocrine Signaling: {{c4::The cell releases long-distance hormones into the bloodstream that reach far-away targets}}
- Direct cell-to-cell Signaling: {{c5::Cells are in almost direct contact and communicate with water-filled channels}}
What happens after a ligand binds to a receptor on a cell?
The cell relays the message through a series of reaction, creating a response from the cell
What is a signal transduction pathway?
A chain of molecules that relay signals inside cells
What are kinases?
Enzymes that catalyze the phosphorylation of proteins
(catalyze the addition of phosphate groups to proteins)
What are phosphatases?
Enzymes that catalyze the dephosphorylation of proteins
(catalyze the removal of phosphate groups from proteins)
Why are kinases and phosphatases important?
They can often be used to turn on/off proteins
(many proteins are activated when phosphorylated by kinases, and deactivated when dephosphorylated by phosphatases)
Why is calcium important for cell signaling?
Some proteins have binding sites for calcium and change shape/function when calcium binds
(calcium is used in muscles to start muscle contraction; calcium= Loading KaTeX...