1. Cell Communication
John Girard
Project Opening Doors

2. Cell Communication Cells communicate by chemical “messengers”
Animal and plant cells have cell junctions that directly connect the cytoplasm of adjacent cells
In local signaling, animal cells and unicellular organisms may communicate by direct contact, called cell-cell recognition

3. Cell Communication
Animal cells communicate using local regulators, messenger molecules that travel only short distances
In long-distance signaling, plants and animals use chemicals called hormones

4. Local and Long-Distance Cell Communication in Animals

5. Local and Long-Distance Cell Communication in Animals

6. Local and Long-Distance Cell Communication in Animals

7. Communication by Direct Contact between Cells

8. Communication by Direct Contact between Cells

9. Cell Communication
A signal transduction pathway is a series of steps by which a signal on a cell’s surface is converted into a specific cellular response
Cells receiving signals go through three processes:
Reception
Transduction
Response

10. Overview of Cell Signaling

11. Overview of Cell Signaling

12. Overview of Cell Signaling

13. Receptors in the Plasma Membrane
There are three main types of membrane receptors:
G protein-coupled receptors
Tyrosine kinase receptors
Ion channel receptor

14. The Structure of a G-Protein-coupled Receptor

15. The Functioning of a G-Protein-coupled Receptor

16. The Functioning of a G-Protein-coupled Receptor

17. The Functioning of a G-Protein-coupled Receptor
These biochemical pathways include developmental pathways, sensory perception in vision and smell.
Bacteria that often cause disease by secreting toxins. These toxins may interfere with G-protein functions. 60% of all medicines exert their effect by influencing G-protein pathways.

18. The Functioning of a G-Protein-coupled Receptor Activity: Pathways with Friends
Instructions
Form groups of 6 people each
Create space for your group to interact without bumping into each other
Rules:
Each person in the group will get a card
Do not let others in your group know what your card says
When prompted, follow the instructions on the card

19. The Functioning of a G-Protein-coupled Receptor Activity: Pathways with Friends

20. The Functioning of a G-Protein-coupled Receptor Activity: Pathways with Friends

21. The Functioning of a G-Protein-Coupled Receptor Activity:

22. The Functioning of a G-Protein-Coupled Receptor Activity:

23. Receptors in the Plasma Membrane
Tyrosine-kinase receptors are membrane receptors that attach phosphates to tyrosines
A tyrosine-kinase receptor can trigger multiple signal transduction pathways at once
A major class of membrane proteins having enzymatic activity
A kinase is a class of enzymes that catalyzes the transfer of phosphate groups

24. The Structure and Function of a Tyrosine-Kinase Receptor

25. The Structure and Function of a Tyrosine-Kinase Receptor
When activated, tyrosine-kinase receptors can activate more than one signal-transduction pathway at one time.
This is important when an event like cell reproduction requires a number of biochemical pathways to be activated at once.

26. The Structure and Function of a Tyrosine-Kinase Receptor
Activity:

27. The Structure and Function of a Tyrosine-Kinase Receptor
Activity:

28. A Ligand-Gated Ion-Channel Receptor

29. A Ligand-Gated Ion-Channel Receptor

30. A Ligand-Gated Ion-Channel Receptor

31. Steroid Hormone Interacting with an Intracellular Receptor
(testosterone)
Receptor
protein
Plasma
membrane
EXTRACELLULAR
FLUID
DNA
NUCLEUS
CYTOPLASM
Steroid Hormone Interacting with an Intracellular Receptor
Signal must be lipid soluble to make into the cytosol.
These signals are usually steroid hormones, thyroxine, and nitric oxide.
Testosterone enters the cell and binds with a receptor protein found in the cytoplasm. This complex now moves to the nucleus where is acts a transcription factor and helps transcribes certain genes.

32. Steroid Hormone Interacting with an Intracellular Receptor
protein
Hormone
(testosterone)
EXTRACELLULAR
FLUID
Plasma
membrane
Hormone-
receptor
complex
DNA
NUCLEUS
CYTOPLASM
Steroid Hormone Interacting with an Intracellular Receptor
Signal must be lipid soluble to make into the cytosol.
These signals are usually steroid hormones, thyroxine, and nitric oxide.
Testosterone enters the cell and binds with a receptor protein found in the cytoplasm. This complex now moves to the nucleus where is acts a transcription factor and helps transcribes certain genes.

33. Steroid Hormone Interacting with an Intracellular Receptor
(testosterone)
EXTRACELLULAR
FLUID
Receptor
protein
Plasma
membrane
Hormone-
receptor
complex
DNA
NUCLEUS
CYTOPLASM
Steroid Hormone Interacting with an Intracellular Receptor
Signal must be lipid soluble to make into the cytosol.
These signals are usually steroid hormones, thyroxine, and nitric oxide.
Testosterone enters the cell and binds with a receptor protein found in the cytoplasm. This complex now moves to the nucleus where is acts a transcription factor and helps transcribes certain genes.

34. Responses to Other Signals
Inner
chamber
Outer
–90 mV
140 mM
5 mM
KCI K+
Cl–
Potassium
channel
(a) Membrane selectively permeable to K+
(b) Membrane selectively permeable to Na+
+62 mV
15 mM
NaCI
150 mM
Na+
Sodium

35. Responses to Other Signals
CYTOPLASM
Reception
Plasma
membrane
Cell
wall
Phytochrome
activated
by light
Light
Transduction
Second messenger
produced
cGMP
NUCLEUS 1 2
Specific
protein
kinase 1

36. Responses to Other Signals
CYTOPLASM
Reception
Plasma
membrane
Cell
wall
Phytochrome
activated
by light
Light
Transduction
Second messenger
produced
cGMP
Specific
protein
kinase 1
NUCLEUS 1 2
kinase 2
Ca2+ channel
opened
Ca2+

37. Responses to Other Signals
CYTOPLASM
Reception
Plasma
membrane
Cell
wall
Phytochrome
activated
by light
Light
Transduction
Second messenger
produced
cGMP
Specific
protein
kinase 1
NUCLEUS 1 2
kinase 2
Ca2+ channel
opened
Ca2+
Response 3
Transcription
factor 1
factor 2
Translation
De-etiolation
(greening)
response
proteins P

38. Signal Transduction Pathways
Protein kinases transfer phosphates from ATP to protein, a process called phosphorylation
A major class of membrane proteins having enzymatic activity
A kinase is a class of enzymes that catalyzes the transfer of phosphate groups

39. Signal Transduction Pathways
Protein phosphatases remove the phosphates from proteins, a process called dephosphorylation
This phosphorylation and dephosphorylation system acts as a molecular switch, turning activities on and off
A major class of membrane proteins having enzymatic activity
A kinase is a class of enzymes that catalyzes the transfer of phosphate groups

40. A Phosphorylation Cascade
Signaling molecule
Receptor
Activated relay
molecule
Serine and threonine of the two amino acids that receive the phosphate group on the receiving protein.
Approximately 1% of all our genes code for various protein kinases.

41. A Phosphorylation Cascade
Signaling molecule
Receptor
Activated relay
molecule
Inactive
protein kinase 1
Active
protein
kinase

42. A Phosphorylation Cascade
Signaling molecule
Receptor
Activated relay
molecule
Inactive
protein kinase 1
Active
protein
kinase 2
ATP
ADP P PP i
Protein kinases are proteins that transfer phosphate groups from ATP to another protein.
Serine and threonine of the two amino acids that receive the phosphate group on the receiving protein.
Approximately 1% of all our genes code for various protein kinases.
Protein phosphatases remove a phosphate group from proteins and can deactivate a protein kinase.

43. A Phosphorylation Cascade
Signaling molecule
Receptor
Activated relay
molecule
Inactive
protein kinase 1
Active
protein
kinase 2
ATP
ADP P PP 3 i

44. A Phosphorylation Cascade
Signaling molecule
Receptor
Activated relay
molecule
Inactive
protein kinase 1
Active
protein
kinase 2
ATP
ADP P PP 3 i
Cellular
response
Phosphorylation cascade

45. Second Messengers
The extracellular signal molecule that binds to the receptor is a pathway’s first messenger
Second messengers are small, nonprotein, water-soluble molecules or ions that spread throughout a cell by diffusion
A major class of membrane proteins having enzymatic activity
A kinase is a class of enzymes that catalyzes the transfer of phosphate groups

46. Second Messengers
Cyclic AMP (cAMP) is one of the most widely used second messengers
Adenylyl cyclase, an enzyme in the plasma membrane, converts ATP to cAMP in response to an extracellular signal
A major class of membrane proteins having enzymatic activity
A kinase is a class of enzymes that catalyzes the transfer of phosphate groups

47. cAMP as a Second Messenger
First messenger
G protein
Adenylyl
cyclase
GTP
ATP
cAMP
Second
messenger
Protein
kinase A
G protein-coupled
receptor
Cellular responses

48. Epinephrine Transduction Pathway
cAMP
Second
messenger
Adenylyl
cyclase
G protein-coupled
receptor
ATP
GTP
G protein
Epinephrine

49. Epinephrine Transduction Pathway
cAMP
Second
messenger
Adenylyl
cyclase
G protein-coupled
receptor
ATP
GTP
G protein
Epinephrine
Inhibition of
glycogen synthesis
Promotion of
glycogen breakdown
Protein
kinase A

50. cAMP as a Second Messenger Activity:

51. cAMP as a Second Messenger Activity:

52. Calcium Ions
Calcium ions (Ca2+) act as a second messenger in many pathways
Calcium is an important second messenger because cells can regulate its concentration
A major class of membrane proteins having enzymatic activity
A kinase is a class of enzymes that catalyzes the transfer of phosphate groups

53. The Maintenance of Calcium Ion Concentrations in an Animal Cell
High Ca++
Low Ca++
Some signal molecules in animals induce responses by increasing the amount of Ca++ in the cytosol
This is used in muscle and nerve cells

54. Inositol Triphosphate
Pathways leading to the release of calcium involve inositol triphosphate (IP3) and diacylglycerol (DAG) as additional second messengers

55. Calcium and Inositol Triphosphate in Signaling Pathways
EXTRA-
CELLULAR
FLUID
G protein
GTP
Phospholipase C
PIP2
DAG
Endoplasmic
reticulum (ER)
Ca2+
CYTOSOL
Signaling molecule
(first messenger)
IP3
IP3-gated
calcium channel
(second messenger)
G protein-coupled
receptor

56. Calcium and Inositol Triphosphate in Signaling Pathways
G protein
PIP2
EXTRA-
CELLULAR
FLUID
Signaling molecule
(first messenger)
GTP
IP3
DAG
IP3-gated
calcium channel
Endoplasmic
reticulum (ER)
Ca2+
CYTOSOL
Phospholipase C
(second messenger)
(second
messenger)
G protein-coupled
receptor
DAG = diacylglycerol
IP3 = inositol triphosphate

57. Calcium and Inositol Triphosphate in Signaling Pathways
DAG
Various
proteins
activated
Cellular
responses
Ca2+
(second
messenger)
Endoplasmic
reticulum (ER)
CYTOSOL
IP3-gated
calcium channel
PIP2
IP3
(second messenger)
GTP
G protein
G protein-coupled
receptor
EXTRA-
CELLULAR
FLUID
Signaling molecule
(first messenger)
Phospholipase C
DAG = diacylglycerol
IP3 = inositol triphosphate

58. Growth factor
Receptor
Phosphorylation
cascade
Reception
Transduction
Active
transcription
factor
Response P
Inactive
CYTOPLASM
DNA
NUCLEUS
mRNA
Gene
Nuclear Response to a Signal: The Activation of a Specific Gene by a Growth Factor

59. Signal Amplification: Stimulation of Glycogen Breakdown by Epinephrine

60. Is Signal Transduction Important?
Androgen Insensitivity
Syndrome:
Genetic male (XY) without androgen receptors
The gene for the syndrome is on the X chromosome in band Xq11-q12.
The gene codes for the androgen receptor.
Result: No signal transduction!

61. Cell Communication Free-Response Questions
1992
2. Biological recognition is important in many processes at the molecular, cellular, tissue, and organismal levels. Select three of the following, and for each of the three that you have chosen, explain how the process of recognition occurs and give an example.
Organisms recognize others as members of their own species.
Neurotransmitters are recognized in the synapse.
Antigens trigger antibody responses.
Nucleic acids are complementary.
Target cells respond to specific hormone

62. Cell Communication Free-Response Questions
1999
2. Communication occurs among the cells in a multicellular organism. Choose THREE of the following examples of cell-to-cell communication, and for each example, describe the communication that occurs and the types of responses that result from this communication.
Communication between two plant cells
Communication between two immune-system cells
Communication either between a neuron and another neuron, or between a neuron and a muscle cell
Communication between a specific endocrine-gland cell and its target cell

63. Cell Communication Free-Response Questions
2007
1. Membranes are essential components of all cells.
Identify THREE macromolecules that are components of the plasma membrane in a eukaryotic cell and discuss the structure and function of each.
Explain how membranes participate in THREE of the following biological processes:
Muscle contraction
Fertilization of an egg
Chemiosmotic production of ATP
Intercellular signaling

64. Cell Communication Free-Response Questions
2008
1. The physical structure of a protein often reflects and affects its function.
Describe THREE types of chemical bonds/interactions found in proteins. For each type, describe its role in determining protein structure.
Discuss how the structure of a protein affects the function of TWO of the following.
Muscle contraction
Regulation of enzyme activity
Cell signaling
Abnormal hemoglobin is the identifying characteristic of sickle cell anemia. Explain the genetic basis of the abnormal hemoglobin. Explain why the sickle cell allele is selected for in certain areas of the world.