AP Bio Unit 4: Cellular Communication

Quorum Sensing

1. Bacteria grow and establish

2. Bacteria release pheromones that serve as a population tracker

3. Once there is a high enough population, start STP with response of releasing pathogenic factors

How to combat quorum sensing?

Inhibit pheromone receptors —> ?? population size —> no pathogen attack

Yeast STP

1. Exchange chemical factors from 2 cells during reception

2. 2 cells combine

3. Response: The combined cell now splits into more cells, promoting genetic diversity

Local Signalling

Type of cell communication through signal transduction pathways between nearby cells. Examples include Quorum sensing and yeast cell division.

plasmodesmata

proteins in the plasma membrane of cells that transport carbs from one cell to another across cell walls.

White Blood Cell STP

1. Reception: White blood cells secrete antibodies, which bind to infected cells

2. Transduction: Through the exchange of cytokines, killer T cells are signalled to the infected cell

3. The T cell forces the infected cell to commit apoptosis

Direct Contact

A type of cell signalling wherein the target cells are directly touching and exchanging molecules. Examples include plasmodesmata and white blood cells and antigens.

Autocrine Signalling

A cell secretes a ligand that binds ontoo a receptor from the same cell, triggering a response in the cell that secreted a ligand. An example includes cancer cells, releasing their own growth hormones to signal the cell to grow and divide.

Paracrine Signalling

The cell secretes a ligand that travels a short distance, eliciting an effect on cells in nearby areas.These ligands are also referred to as local regulators because they only affect cells in the immediate vicinity.

Paracrine

Plants signalling apoptosis for infected cells (PAMP) and cell differentiation are examples of _____ signallining.

Endocrine Signalling

Type of cell signalling that sends ligands long distances to target cells.

Hormones

The ligands in endocrine signalling are called ___

Endocrine

Insulin production in response to increased blood sugar levels, glucagon production in response to low blood sugar levels, ethylene, and human growth hormone are examples of this type of signalling

Positive feedback loop

A chemical pathway wherein its products cause more of the same products to be made, amplifying the response. An example includes ethylene gas ripening bananas and oxytocin in stimulating more uterus contractions for child birth.

Synaptic Signalling

A type of paracrine signalling that uses neurotransmitters as the ligand to communicate between neurons.

Negative Feedback Loop

A metabolic pathway wherein the products of the pathway inhibit production of the same products, in an attempt to return a system to its original state; homeostasis.

ligand

name for signal molecule that attaches to receptor proteins

amplifies signal with each reaction

why have multistep STPs?

hydrophilic, polar, hydrophobic, nonpolar

_____ ligands cannot cross the plasma membrane due to their ____ nature, and as such must bind to receptors located on the outside. ____ ligands are _____, so they can pass the plasma membrane and bind to intracellular receptor proteins, allowing them to eventually cross the nuclear membrane and bind to DNA, impacting gene expression.

1. Reception: aldosterone binds to a receptor within the nucleus

2. Transduction: Transcription of genes to MRNA happens

3. Response: proteins that regulate water and sodium balance are produced

describe the STP for aldosterone

kinase

enzyme that transfers phosphate groups to ther molecules, activating them

phosphatase

enzyme that removes phosphate groups to ther molecules, deactivating them

hormones

first messenger in a signalling pathway

cAMP and Ca2+

second messenger in a signalling pathway

epinephrine and glycogen metabolism

cytoplasmic response examples

aldosterone and gene activation

nuclear response example

receptor protein, specialized

two different tissues can be influenced by the same ligand yet have different responses because they have the same _____ and are _____cells with unique enzymes and genes

diverge

A STP can ___ resulting in two or more cellular response

converge, cross talk

A STP can ___ resulting in one common cellular response. This is called ____

scaffolding proteins

proteins that help other proteins maintain their structure and function.

apoptosis

programmed cell death by receiving an external or internal signal. The lysozyme spills digestive juices and dissolves organelles.

adenylyl cyclase

produces the secondary messenger cAMP. If inhibited the secondary messenger would not be made, stopping rest of pathway

chromosomes

coiled form of DNA, only in this state for cell division

chromatin

uncoiled form of dna, noodle like, must be in this form for gene expression

centromere

region of chromosome where sister chromatids are connected

kinetochore

place on chromosome where spindle fibers attach

46 chromosomes in each, 92 sister chromatids in G2

number of chromosomes and sister chromatids in G1 vs G2

two daughter cells with identical number of chromosomes as parent cell

result of mitosis

binary fission

cell division in prokaryotes: hint loook for chromatin

interphase

prep for cell division phase

G1 phase

Duplicate all raw materials and organelles, 46 non duped chromosomes are present

S phase

all genetic chromosomes are duplicated, resulting in 92 sister chromatids but still 46 chromosomes.

G2 phase

synthesize more proteins and enzymes, copy centrioles for making spindle fibers

interphase

dna is uncoiled in chromatin, G1, S, and G2 happen

prophase

chromatin begins coiling into chromosomes via histone proteins, spindle fibers beegin to form

Prometaphase

nuclear envelope begins dissolving, kinetochore starts forming to attactch to spindle fibers

Metaphase

chromosomes are fully coiled and aligned at metaphase plate (equator of cell), spindle fibers attach to kinetochore and prepare to move to poles

Anaphase

Signals tell cell to move from metaphase to anaphase once spindle is fully formed and connected to kinetochore. Spindles pull sister chromatids to poles

Telophase

nuclear envelope reforms, chromosomes uncoil into chromosomes, spindle dissolves, and two nuclei are formed

Mitosis

Portion of cell division from Prophase to Telophase resulting in nuclear divison. Aka m phase

Cytokinesis

Contractile pinches cytoplasm in half, forming a cleavage furrow in animal cells and a cell plate (new cell wall) in plant cells.

cyclin dependent kinases (CDKs)

enzymes dependent on activation by cyclin. Give go ahead signals at G1 and G2 checkpoints if active, constant concentration but activity depends on cyclin.

cyclins

concentration in cells rises and falls for different stages, but activate cdks

G0 phase

state of limbo in cell division for cells who lack the nutrients or go ahead signal to proceed. Will not divide unless unpaused. Examples include mature nerve cells.

G1 Checkpoint (Restriction Point)

checkpoint between G1 and S. Cell checks to see if there is adequate nutrients, cell size, DNA damage, growth factors/hormones before giving go ahead signal. If check is failed, cells enter G0 until further notice.External Signal

S Checkpoint

checkpoint in between S and G2. Cell checks to see if there is DNA damage or tangling before proceeding. If cells proceed without the go ahead signal, defective genese/gene activation struggles may occur.

G2 Checkpoint

During G2, checks to see if cell is adequate in size and organelles, DNA replication has occurred before proceeding. Internal SIgnal from cyclins and cdks

M Checkpoint

Metaphase checkpoin. Ensures that spindles are fully formed, kinetochores are attaching chromatids to spindle fibers, and aligned in equator of cell. If proceeding without go ahead signal, there may be unequal chromosome count in daughter cells. Internal Signal kinetochores

Anaphase Telophase Checkpoint

Checkpoint between anaphase and telophase. Ensures chromosomes are at the poles before dividing nucleus. If go ahead signal is ignored, chromosome damage may occur during nuclear division.

apoptosis, cancer

If the cell cycle fails to regulate the cell cycle properly, ____ or ___ is a likely outcome

activating genes, enzymes, altering cell shape

Ways to identify response in STP