Cell Communication

·      Direct Contact

o   Plants-Plasmodesmata

o   Animals-Gap Junction

o   Example: Immune Cells- T Cells and antigen presenting cells

·      Local Signaling

o   Paracrine

o   Synaptic-Neurotransmitters

·      Long Distance

o   Endocrine system

o   Example: Hormones (Insulin)

About ¾ Questions on this section

Cell Signaling

1.        Reception- Ligand (anything that binds) binds to the receptor- changes its shape (which will activate something else) initiates transduction

2.        Transduction-

o   Plasma membrane receptors (outside of cell)- Polar, water soluble (hydrophilic), or large molecules

o   Intracellular (inside of cell)- Nonpolar, Hydrophobic, Steroid/Gases/Lipids

o   Protein Kinase- Phosphorylate- Keeps the pathway going.

o   Phosphatase- Dephosphorylates- Stops the pathway

o   Second Messenger- cyclic AMP. Amplifies signal, Activates multiple proteins

3.        Response-

o   Alter membrane permeability

o   Activate an enzyme which changes a metabolic process

o   Gene Expression (turning genes on and off,  Allowing transcription to happen now)

Two Examples:

·      GPCRs: know steps:

o   Ligand binds on GPCR extracellular side

o   Causes the cytoplasmic side to change shape

o   G protein binds to GPCR- becomes active

o   GPD becomes GTP

o   Allows part of G protein to bind to an enzyme and the enzymes actives the pathway and the signal amplifies.

·      Ion Channels:  (Used in the nervous system)

o   “gate” opens when the ligan bind and allows ion to flow through the channel

About 7/8 Questions on this

Positive and Negative Feedback

·      Negative Feedback- If something is too high or low something will occur to bring it back to normal (Example: Glucose and Insulin. Blood sugar(glucose) to low Glucagon increase, if too high Insulin will bring you down)

·      Positive Feedback- Increases the effect of the stimulus, stray farther from the set point. (Examples: Child Labor, Blood Clotting, Fruit Ripening)

About 1 question on each of these

Cell Cycle and Cancer

·      Know the phases, in order- G1, S, G2, Prophase, Prometaphase, Metaphase, Anaphase, Telophase, Cytokinesis

o   G1- Cell growing

o   S-DNA replicates

o   G2- Chemical reactions

o   Prophase- Chromosomes condense, Spindles (microtubules) start to form, Centrosomes start to separate.

o   Prometaphase- Nuclear Membrane start to dissolve, spindle attaches to some of the kinetochores (centromeres of chromosomes, where spindle attaches) on chromosomes.

o   Metaphase- Spindles will all attaches, the spindles put them in the middle

o   Anaphase- Chromatids are pulled apart

o   Telophase- Nucleus starts to reform, spindle dissolve, difference between plants and animals. Plants have a cell plate that form because of the cell wall (made of pectin). (The cleavage furrow).

o   Cytokinesis- two identical daughter cells that are diploid

·      What phases look like. Look up onion root tip.

·      Checkpoints:

o   G1- cell size, growth factors, DNA Damage. If G1 stops the pathway you enter G0 which means you cannot divide at all.

o   G2- Checking for completion of DNA replication. If stopped it will go through apoptosis

o   M- Microtubule (spindle) connection to the chromosomes at kinetochores at the end of metaphase. If it stops the pathway it can slow it down to correct the connection or go to apoptosis.

·      Cyclins bind to the CDK (cyclin dependent kinase)- Cyclin binds and activates CDK which phosphorylates a step (target proteins) in the cycle.

·      Normal conditions- Cyclins will fluctuate but CDK’s will remain constant. (Cyclins will break down and be recycled through

Not a lot of Questions about Cyclins on Multiple Choice but there is a lot on the FRQ