1. AP Bio Exam Review: Unit 2 – Cells & Cell Communication

2. Comparisons of Scopes Visible light passes through specimen
Compound Light
Electron
Visible light passes through specimen
Light reflects light so specimen is magnified
Magnify up to 1000X
Specimen can be alive/moving
color
Focuses a beam of electrons through specimen
Magnify up to 1,000,000 times
Specimen non-living
Black and white

3. Prokaryote Vs. Eukaryote
“before” “kernel”
No nucleus
DNA in a nucleoid
Cytosol
No organelles other than ribosomes
Small size
Primitive
i.e. bacteria
“true” “kernel”
Has nucleus and nuclear membrane
Cytosol
Has organelles with specialized structure and function
Much larger in size
More complex
i.e. plant/animal cell

4. Parts of plant & animal cell p 108-109

6. Cells must remain small to maintain a large surface area to volume ratio
Large S.A. allows increased rates of chemical exchange between cell and environment

13. Animal cells have intercellular junctions:
Tight junction = prevent leakage
Desmosome = anchor cells together
Gap junction = allow passage of material

14. Cell Membrane

15. 6 types of membrane proteins

16. Passive vs. Active Transport
Little or no Energy
Moves from high to low concentrations
Moves down the concentration gradient
i.e. diffusion, osmosis, facilitated diffusion (with a transport protein)
Requires Energy (ATP)
Moves from a low concentration to high
Moves against the concentration gradient
i.e. sodium/potassium pumps, exo/endocytosis

17. hypotonic / isotonic / hypertonic

18. Apoptosis = cell suicide
Cell is dismantled and digested
Triggered by signals that activate cascade of “suicide” proteins (caspase)
Protect neighboring cells from damage
Animal development & maintenance

19. Sodium potassium pump
Endocytosis
Exocytosis

20. Exocytosis and Endocytosis transport large molecules
3 Types of Endocytosis:
Phagocytosis (“cell eating” - solids)
Pinocytosis (“cell drinking” - fluids)
Receptor-mediated endocytosis
Very specific
Substances bind to receptors on cell surface

21. Cell Communication

22. Multicellular Organisms
Behave as a community – “Cells talk”
Neighbors carry on private conversations
Messages are sent over distances
Phone
Mail
Public announcements are made
Alarms are rung when there is danger

23. Signal Transduction Pathways
Conversions of signals from one form to another in a cell
Verbal instructions  written text   voice mail  action
Eventually a response will occur due to the original signal

24. Communication Signal cell  Target cell Cell to cell recognition
Cell Junctions
Local Regulators
Distance Regulators

25. Cell to cell recognition
Glycoproteins, glycolipids, and other molecules on plasma membranes serve as recognition markers.
Important for immune response and embryonic development

26. Cell Junctions Plasmodesta – plant cells Gap Junctions – animal cells
Allow communication between the cytoplasm of neighboring cells.
Plasma membranes
Plasmodesmata
between plant cells
Gap junctions
between animal cells
Figure 11.3
(a) Cell junctions. Both animals and plants have cell junctions that allow molecules
to pass readily between adjacent cells without crossing plasma membranes.

27. Local Regulators Communicate and influence cells in close proximity
Figure 11.3
(b) Cell-cell recognition. Two cells in an animal may communicate by interaction
between molecules protruding from their surfaces.
Communicate and influence cells in close proximity
Growth factors – cause multiplication and growth of target cells
Paracrine Signaling – simultaneous response by more than one cell
Synaptic Signaling – Nervous system
Neurotransmitters diffuse from one nerve cell to stimulate the next

28. diffuses across synapse
(a) Paracrine signaling. A secreting cell acts on nearby target cells by discharging molecules of a local regulator (a growth factor, for example) into the extracellular fluid.
(b) Synaptic signaling. A nerve cell releases neurotransmitter molecules into a synapse, stimulating the target cell.
Local regulator
diffuses through
extracellular fluid
Target cell
Secretory
vesicle
Electrical signal
along nerve cell
triggers release of
neurotransmitter
Neurotransmitter
diffuses across synapse
is stimulated
Local signaling
Figure 11.4 A B

29. Long-distance signaling
Distance Regulators
Hormone travels
in bloodstream
to target cells
(c) Hormonal signaling. Specialized endocrine cells secrete hormones into body fluids, often the blood Hormones may reach virtually all body cells.
Long-distance signaling
Blood
vessel
Target
cell
Endocrine cell
Figure 11.4 C
Hormones
Carried in the bloodstream of animals
Endocrine System  Circulatory System
Carried in the vesicles of plants

30. Relay molecules in a signal transduction pathway
Cell Signaling
EXTRACELLULAR
FLUID
Receptor
Signal
molecule
Relay molecules in a signal transduction pathway
Plasma membrane
CYTOPLASM
Activation
of cellular
response
Figure 11.5
Reception
Transduction
Response
1. Reception – detection of message by a receptor protein on a target cell (several different receptors)
2. Transduction – receptor changes and initiates a cascade of events
3. Response – activation of target

31. Plasma Membrane Receptors
G-protein-linked receptor
Receptor tyrosine kinase (kinase is an enzyme that phosphorylates other proteins to activate them)
Ligand-gated ion channel

32. a) G-Protein-Linked Receptor
Signal molecule attaches to receptor and activates
G-protein is activated
G-protein activates an enzyme which triggers a cascade in the cell to the target.
Used for vision and smell
60% of medicines activate G-proteins
Secondary structure

33. b) Tyrosine Kinase Receptor
Signal molecule
Signal-binding sitea
CYTOPLASM
Tyrosines
Signal molecule
Helix in the
Membrane
Tyr
Dimer
Receptor tyrosine kinase proteins (inactive monomers) P
Cellular response 1
Inactive relay proteins
Activated relay proteins
Cellular response 2
Activated tyrosine-
kinase regions
(unphosphorylated
dimer)
Fully activated receptor
tyrosine-kinase
(phosphorylated
6 ATP ADP
Figure 11.7

34. c) Ligand-Gated Ion Channels
Cellular response
Gate open
Gate close
Ligand-gated
ion channel receptor
Plasma Membrane
Signal molecule (ligand)
Figure 11.7
Gate closed
Ions
Signal molecule attached to ligand opening a gate for specific ions
Once Ions enter specific reactions take place
Na+
Ca+

35. Transduction Cascade Step 1 step 2  step 3  step 4  reaction
Activated by phosphorylation
ATP  ADP + P
Protein Kinases
Deactivated by dephosphorylation
P removed
Protein phosphatases

36. Second Messengers Small, non protein, water soluble, ions Cyclic AMP
Levels regulate gene expression in bacteria
Calcium Ions – Ca2+
Receptors on the outside of the membrane are the 1st messengers

37. Cyclic AMP Created from ATP from adenyl cyclase Used with G proteins
1st or 2nd messenger
Figure 11.9 O –O N O P OH
CH2
NH2
ATP
Ch2
H2O HO
Adenylyl cyclase
Phoshodiesterase
Pyrophosphate
Cyclic AMP
AMP i

38. Response
Reception
Transduction
Response
mRNA
NUCLEUS
Gene P
Active
transcription
factor
Inactive
DNA
Phosphorylation
cascade
CYTOPLASM
Receptor
Growth factor
Figure 11.14
Signals are amplified as they are sent from messenger to messenger.
Signals are specific to target cells and enzymes
Not all cells respond to a signal

39. Amoeba sisters cell-to-cell communication video