Wk 1 Flashcards
Cell to Cell Communication (27 cards)
What are the two types of cell signalling?
Intercellular (between cells) and Intracellular (within cell)
What are the types of cell to cell communication?
Direct (electrical) and Indirect (chemical)
What is direct communication?
Contact dependent communication and gap junctions (tiny water-filled channels that directly connect neighbouring cells)
What is indirect communication?
Extracellular messengers, chemicals and chemical messengers (ligands)
What are the types of cell to cell junctions for direct communication?
Tight Junctions - impermeable seals (proteins; occludin, claudin)
Adherens Junctions - below tight junctions (proteins; actin, anchor proteins)
Desmosomes - cell to cell adhesion (cadherin protein)
Gap Junctions - connect cytoplasm of two cells (gap junction channel, direct communicating channel)
What are the types of indirect communication?
Autocrine - messenger acts on the same cell
Paracrine - messenger acts on another cell (closer to the release site)
Endocrine - messenger released into blood (acts on cells far away from the release)
Neurocrine - messenger synthesised and released from neurone
What is the cell to cell communication pathway?
- Signal molecule (ligand)
- Receptors (Intracellular - cytoplasm or nucleus, Extracellular - cell membrane)
- Ligand + receptor complex (activates intracellular responses)
- Cell response
- cell growth
- cell division
- cell differentiation
- cell secretion
- cell metabolism
What is the role of a chemical messenger?
- Secreted from the cell
- Travels in ECF/blood
- Binds to specific receptor
- Receptor on the target cell
- Brings about cellular response
Most long distance communication is the responsibility of which systems?
Nervous system and Endocrine system
What is the type of long distance communication used by the nervous system?
Neurotransmitters
- electrical signals from the neuron
- neuron to neuron
- ‘nerve impulses’ for long distance communication
What are the types of long distance communication used by the endocrine system?
Hormones
- hormones from endocrine gland
- chemical messengers
- distant target cells
Neurohormones
- neurohormones from neuronal endings
- secreted like transmitters
- secreted into blood
- hormone like release
What are the types of neurotransmitters?
Excitatory
- stimulates next neuron
- depolarization of the membrane potential (Na+ influx)
- E.g. Acetyl chlorine, Norepinephrine, Epinephrine
Inhibitory
- inhibits next neuron
- hyperpolarization of the membrane potential (K+ influx, Cl- influx)
- E.g. GABA, Glycine
What is the cell signal pathway?
- Ligand
- Receptor (outside cell)
- Enzyme activation
- Messenger synthesis (inside the cell)
- Enzyme activation
- Phosphorylation of proteins
- Cell response
What are the types of receptors?
- Nervous system (modified nerve ending)
- Membrane receptors (attached to cell membrane)
- Cytosolic/Nuclear receptor (receptor in cytosol)
What is lipophobic?
- Not lipid soluble
- Receptors on the cell membrane
- Does not cross cell membrane
- E.g. Epinephrine, Insulin, Glucagon
What is lipophilic?
- Lipid soluble
- Cross cell membrane
- Intracellular receptors
- E.g. Steroids, Cortisol, Thyroid hormones
What are second messengers?
Small molecules or ions that relay signals received by cell surface receptors to effector proteins.
- amplify the signal
- they are intracellular
- activate intracellular signal pathway
- activate or inhibit cell response
How is the second messenger formed?
- Ligand or the chemical (first messenger)
- Ligand binding (alters protein conformation of the receptor)
- Forms second messenger inside the cell
- Second messengers are used for:
- disseminating information
received from cell surface
receptors - may also be produced for
stimuli within the cells
- disseminating information
What are the types of second messengers?
- Cyclic AMP (cAMP)
- Cyclic GMP (cGMP)
- Calcium ions (Ca++)
- Inositol Triphosphate (IP3)
- Diacyl Glycerol (DAG)
What are the types of membrane receptors?
- Receptor - ion channel
- G-Protein Coupled Receptor (GPCR)
- Receptor Enzyme (Tyrosine Kinase)
- Integrin Receptor
What are the types of Ion Channel receptors?
Ionotropic Membrane Receptor
- Signal molecule binds to ion channel
- Open/close ion channel gate
- Movement of ion across the membrane
Metabotropic Membrane Receptor
- Receptor binding with ligand
- Change in metabolic pathway
- Activation or inactivation of enzymes
- E.g. (GPCR, Tyrosine Kinase)
What are the steps for G Protein Receptor?
- Ligand binds to GPCR
- Alpha subunit exchanges GDP to GTP
- Alpha subunit activates an amplifier enzyme (adenylate cyclase)
- Activates the second messenger
- Second messenger in involved in creating its next action (e.g. protein phosphorylation and chemical secretion)
What occurs when cAMP is the second messenger?
- Adenylyl cyclase (AC) is activated
- Converts ATP to cAMP , which then can activate PKA
- Activates Protein Kinase A
- Phosphorylates proteins
- Cellular response
What occurs when IP3 is the second messenger?
- Phospholipase C (PLC) is activated
- Converts PIP2 to IP3
- Release Ca++ from intracellular stores
- Increase of cytosolic Ca++
- Cellular response
