AP Bio Unit 4: Cell Communication and Cell Cycle

Steps of Communication

Steps of Communication

Chemical SIgnal → Reception → transduction → response

Different types of Ligands, Chemical Signals

• Steroid Hormone - is a ligand and will bind to intraceullular receptors because it can simple diffuse. ex: tesosterone

• Peptide Hormones - it is released by exocytosis and it is received by an extraceullular receptor ex: insulin

• Neurotransmitters -

• Factors - proteins that are associated with the name -

• Cytokines

Receptors

• Intracellular receptors, - accept steroid based hormones - no secondf messenger (the receptor hormone complex can do the things)

• ligand-gated ion channels,- in neurons

• G protein-coupled receptors-

• receptor tyrosine kinases. (enzyme) - monomers → dimer

Receives the specific ligands, and will bind to it

Transduction

• second messenger like cAMP or Caclium ion (smooth ER) - prelavent in muscles

• Phosphorylation Cascades - relays protein kinases

  • Amplification

  • enzymes - kinase and phosphatateses

Responeses

• cell grwoth

• secretion of molecules

• gene expression

• alter gene function

• apoptosis

Quourum Sensing

The ability of bacteria to sense the presence of other bacteria via secreted chemical signals. This allows the members of the population to match up their activities

created biofilm

What does communication by direct cellular contact entail?

In animal cells, gap junctions connect two cells, allowing them to exchange materials such as signals, vitamins, ions, amino acids, sugars, and water
In plant cells, plasmodesmata connect two cells

Cell-cell contact recognition

Whats its usage

An infected cell will inject a pathogen using phagocytosis and present an antigen with its MHC to a T-Cell

Long vs. Short Distance Communication

Long: -Use of bloodstream
-Involves Endocrine system
Short:-nervous system
-Local signaling
-factors

Cell Cycle Stages

Interphase→ Mitosis

Interphase

• G0 nothing happening, “chilling”

• Has the G1 (duplication of organels and synthesis of proteins, RNA, etc)

• Synthesis - replication of genetic material (DNA Polymerase)

• G2 - synthesis if Proteins and RNA and oragnells

Mitosis

Each Phade and their Role

• Prophase → metaphase → anaphase → telophase

• Prophase- prepare, chromatids condense and pair on their centromeres, nuclear envelope disengrates

• Metaphase - sister chromatids align in the middle and microtibles attach

• Anaphase - pulling apart - spindles pull apart, kinetocore “handle" that spindles holdon to

• Telophase- 2 nuclei are formed

• Cytokinesis - the division and cell plates

Spindles

Sprindles plus microtubles pull apart the sister crhomatids and they attactch to kinetoshore proteins

Checkpoints and Regulation

G1 check - determines wether it should start, activated by a growth factor, adequate reserves, and checks for DNA Damage

G2 - check if all DNA is replicated without errors. For example if there is DNA damage, p53 will; be produced and activate a CDK inhibitor

End Checkpoint Metaphase - make sure that sister chromatids are attached

if failure: then it might go to the apoptosis or back to G0

Cyclin and CDK

Proteins that regulate the cellcycle

Cyklin is a protein that will be made and will bind the CDK to activate the kinases Maturation Promoting Factor

these kinases activate the key enzymes and proteins for cell division etc

cdk is constant, the cyclin is built and broken down

Nervous System

• Chemical signal (dendrites) → Electrical action potential (axon) → Chemical (synapse)

  • Chemical = neurotransmitters

  • Electrical = ions and their corresponding charges 

• 1: Resting State: Na+ and K+ voltage-gated channels closed. Inside more negative than outside.

• 2: Depolarization: A stimulus causes Na+ channels to open, and Na+ enters. This depolarizes the membrane. If the depolarization reaches the threshold (about -55 mV), then an action potential occurs

• 3: Rising Action Potential: Depolarization causes a chain reaction of Na+ channels opening. The influx of Na+ makes the inside of the cell more positive with respect to the outside.

• 4: Falling Action Potential: The Na+ channels close, and the K+ channels begin to open, causing an outflux of K+ and the inside of the membrane more negative.

• 5: Undershoot: The Na+ channels are still closed (though unblocked), and the K+ channels are still letting K+ out of the cell. This causes a bit of an undershoot in negative membrane potential, after which the Na+/K+ pump restores the membrane resting potential by pumping K+ in and Na+ out.

• Synapses: the end of the axon, the space in between, and the beginning of the dendrites

  • Neurotransmitters are transmitted & received

  • Ca2+ releases neurotransmitters, leads to vesicles fusing with the membrane and releasing

• presypnatic and post sypnatic

type one diabities signaling

and mutation

-like insulin and glucagon towards sugar stimulus

• high blood glucose levels → insulin → lower glucose and put it into the muscles →

• low blood glucose → glucagon → break glycogen → increase blood sugar

• antigonisitc hoRMONES

Signaling - the insulin binds to receptor and a signaling cascade is sent and then a channel opens allowing the glucose in

mutations that affect it will prevent the glucose intake

positive and negative feedback

protoonco genes and onco genes

tumor supresosr genes

-protoonco genes - normal genes that affect cell growth and proliferation, but can become oncogenes when their expression changes because a mutation

-Tumor supresor prevent too much growth

Cancer is the unsupressed growth or mitosis due to mutations

• example: a g-protein is consistently active, or the signal is stuck,

Anchoring junctions

Tight junctions

Gap junctions “communicating”

1. Protein attatchments and filaments that hold cells together and keep structure

2. Tightly stitched seams that prevents passage between cells, so they have to go through them Instead - form movement of solutes etc between cells- prevent leaks

3. Allows transfer of materials, solute, messengers, and connects cytoplasm