cell communication Flashcards
what is the role of protein kinases and protein phosphates in signal transduction?
protein kinases: transfer phosphates from ATP to protein in a process called phosphorylation, turning on most proteins
protein phosphatases: remove phosphates from proteins in a process called dephosphorylation, which usually inactivates the protein
examples of signal transduction pathways stimulating a cytoplasmic response?
turning enzymes on/off, opening/closing channels
examples of signal transduction pathways stimulating a nuclear response?
turning gene transcription on/off, regulating synthesis of enzymes or other proteins
what are some examples of specificity of cell signalling?
- different cells produce different proteins
- different proteins allow different cells to detect and respond to different signals
- also means that the same signal can lead to different responses in different cell types (eg. adrenaline can increase heart rate, open airways, increase blood flow in some vessels, decrease blood flow in other vessels)
why is signal termination important in cell signalling?
- allows cell to receive new signals, prevents excessive responses which can lead to disease states (eg. excessive stimulation of growth and cell division leads to cancer)
when does signal termination happen?
- when the signal molecule leaves the receptor and the receptor reverts to its inactive state
- it is now ready for another incoming signal
what is apoptosis?
- programmed or controlled cell death that infected or damaged cells undergo
how does apoptosis work?
the cell digests its cellular components by packaging them into vesicles, which are removed by white blood cells without inflammation. this prevents enzymes from leaking out of dying cells and damaging neighbouring cells.
purpose of apoptosis?
maintain healthy tissue, development and growth, immune system regulation.
functions of cell wall?
- protects plant cell
- maintains cell shape
- prevents excessive uptake of water
what are the layers of a cell wall and their features?
- primary cell wall (relatively thin and flexible)
- middle lamella (between primary walls, glues adjacent cells together)
- secondary wall (woody plants. between plasma membrane and primary cell wall, very strong)
what is the plasmodesmata? function?
- channels between adjacent plant cells that allows the cells to communicate.
- allows passage of water, small solutes, and sometimes proteins and RNA between cells.
what makes up the ECM?
proteins, protein fibers, glycoproetins
what are the functions of the ECM?
support, adhesion, movement, regulation
describe tight junctions
- membrane proteins fuse adjacent cell membranes together (like layers of quilt stitched together)
- prevents fluid from leaking between cells
- eg. prevents stomach acid from reaching tissues
describe desmosomes
- integral proteins reinforced by cytoskeleton
- strong connection resists stretching, twisting
- eg. skin held together in strong sheets
describe gap juntions
- channel proteins called connexins connect cells like a grommet
- allow exchange of small molecules and ions
- allows for communication between cells
describe local signalling between two cells in contact
- occurs directly between two adjacent cells by passing signalling substances through cell junctions (e.g. coordination of cardiac muscle contraction)
- cell-cell recognition, which is contact between integrins/cell recognition proteins.
describe local signalling across short distances (2 types)
- occurs between cells via local regulators (chemical messengers)
1. paracrine signalling
2. synaptic signalling
what are the chemicals involved in long-distance signalling?
hormones
what is long-distance signalling called in animals?
endocrine signalling
what happens at the reception stage of cell signalling?
- the ligand binds with the receptor (cell surface or inside the cell)
- receptor activates relay molecules
what happens at the transduction stage of cell signalling
- relay molecules connect signal to inner cell
- amplification of the signal
- secondary messengers involved (cAMP, IP3, calcium ions)
- protein kinases transfer phosphate groups from ATP to proteins (phosphorylation)
- protein phosphatases remove phosphates (dephosphorylation)
what happens at the cellular response stage
- specific events turned on or off (gene transcription)
- ion channels opened or closed
- enzymes activated or deactivated
List the two general locations a receptor might be located (what properties will the ligand have to bind to
each?)
- receptor could be on/in cell membrane or in cytoplasm/nucleus.
- ligand must be lipid-soluble to be able to enter cell and bind to receptors inside
- water-soluble ligands cannot enter, therefore bind with membrane protein receptors
Define second messenger and describe two different types
=small non-protein, water-soluble molecules or ions.
two types: cAMP (cyclic), calcium ions
