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Unit 2 Cell structure Cheat Sheet (DRAFT) by

ap bio unit 2 cell structure and function

This is a draft cheat sheet. It is a work in progress and is not finished yet.

plasma membrane

select­ively permeable, fluid mosaic model.
amphip­athic: both hydrop­hobic and hydrop­hilic
Nonpolar molecules, such as hydroc­arbons, carbon dioxide, and oxygen, are hydrop­hobic, so dissol­ve/­cross in the lipid bilayer without membrane proteins

proteins in plasma membrane functions

transport, enzymatic activity, signal transd­uction, cell-t­o-cell recogn­ition, cell-t­o-cell attach­ments, ATTACHMENT TO THE CYTOSK­ELETON AND EXTRAC­ELLULAR MATRIX:

Passive vs. Active Transport

Passive Transport: requires no energy, high to low
Ex: diffusion and osmosis
Osmosis: diffusion of free water across a select­ively permeable membrane
simple diffusion: no protein channel, nonpolar molecules, water; ex "­cou­nte­rcu­rrent exchan­ge" to maximaize the rate of simple diffusion
Facili­tated diffusion: a hydrop­hilic protein channel to speed up, water, ions, polar molecules
Hypertonic: more solute, less solvent
Hypotonic: less solute, mor solvent
Isotonic: two solutions containing equal concen­tration of solutes
water potential: the addition of solute lowers water potential
Water diffuses toward the hypertonic area (higher solute). Solutes diffuse to more hypotonic
Aquaporins: large quantities of water move via aquapo­rins, special water channel proteins that facilitate diffusion, function as gated channels (open and close)
Active Transport: requires energy (ATP), ions, polar molecules
1. Pumps or carriers carry particles across the membrane by active transport. Ions (charged particles) such as potassium and sodium can cross cell membranes only through certain proteins embedded in the membrane.
a. sodium­-po­tassium pump: pumping two K+ ions for every three Na + ions.
b. Proton pumps: H+
c. Cotran­sport: sucrose in plants against a gradient in the company of protons.
2. Contra­ctile Vacuole: pumps out excess water
3. Exocytosis: releas­e/s­ecrete macrom­ole­cules, vesticles containing macrom­ole­cules within the cell fuse with plasma membrane, releasing contents into external enviro­nement.
4. Endocy­tosis: takes in macrom­ole­cules, engulfing to form an intrac­ellular vesicle.
a) Phagoc­ytosis: engulfing into a vacuole.
b) Receptor mediated endocy­tosis: ligand binds to receptor, into a coated vesicle. ex: Choles­terol
Bulk flow movement is always from source (where it origin­ates) to sink (where it is used).
Osmolarity: total solute concen­tration in a solution
Osmore­gul­ation mainatains water balance and allows organisms to control their internal solute compos­ition

Cell Membrane Receptors (first messenger)

Ion Channel receptors
open and shut a gate in a membrane, allowing an influx of ions, such as Na + , K+ , Ca 2+ , or Cl – ions.
G protei­n-c­oupled receptors (GPCR)
ligand binds, changes confor­mation, activates G protein, bonds to GTP, activates the enzyme adenylyl cyclase, convert ATP to cAMP
Receptor Tyrosine Kinases (RTKs)
enzymatic activity, catalyzes the transfer of phosphate groups from ATP to the amino acid tyrosine. After binding, the individual units aggregate and activate the tyrosine kinase region, which bonds to ATP..

Intrac­ellular Receptor

intrac­ellular recpetor
hydrop­hobic, non polar: steroids, thyroid hormones, and NO, nitric oxide, a gas
Transd­uction
Signal transd­uction pathway, a cascade effect, advantage is more opport­unities to amplify the signal greatly.
Response
1. They are charac­terized by a signal, a transd­uction, and a response. 2. They are highly specific and regulated. 3. One signal molecule can cause a cascade effect, releasing thousands of molecules inside a cell. 4. They regulate cellular activity, altering gene expres­sion, protein activity, or protein synthesis. 5.These pathways evolved millions of years ago in a common ancestor.

Apoptosis - programme cell death

1. During embryonic develo­pment, when cells or tissues are no longer needed, they die and are engulfed by neighb­oring cells.
2. too much genetic damage that could lead to cancer.
3. defense against infection by fungus and bacterium. dying so no living tissue to spread infection inside the plant.
4. In mammals, including humans, several different pathways involving enzymes called caspases carry out apoptosis.
 

plasma membrane

Passive and Active Transport

Hypotonic, Hypert­onic, Isotonic solution

cell commun­ication

Quorom Sensing
bacteria to monitor their population density to control gene expres­sion. ex: biolum­ine­scence
Direct Contact
gap junctions permit the passage of materials directly from the cytoplasm of one cell to the cytoplasm of an adjacent cell. ex: Plasmo­desmata
Local Signaling
paracrine signaling: short distance, one layer induces a nearby layer. Synaptic Signaling:nerve cell releases neurot­ran­smi­tters.
Long Distance Signaling
Plant use hormones for long-d­istance signaling.

Three stages of Cell signaling

Ion Channel Receptor

G protein coupled receptor

RTKS

Origins of Cell Compar­tme­nta­liz­ation

Theory of endosy­mbiosis: a previously free-l­iving prokar­yotes (bacteria) was engulfed by another cell through endocy­tosis. After living together symbio­tically for some tme, the once free-l­iving prokaryote lost its indepe­ndent functi­onality and gave rise to either the mitoch­ondria or the chloro­plasts.
Evidence supporting the evolution of mitoch­ondria and chloro­plasts via endosy­mbiosis includes the presense of double membranes, circular DNA, and ribosomes in both organe­lles.