Communication between and within cells

Where do cells receive large amounts of information?

- from the ‘non-living’ /physical environment they are surrounded by

- from other living cells that are either touching, close by or distant.

How do cells respond to their environment?

• Secreting (or not secreting) something

• Absorbing (or not) something

• Starting (or stopping) cell division

• By becoming (or not) a specialised cell

• Cells communicate with themselves and with other cells.

How do most communication occur between cells?

Most cellular communication occurs via sending and receiving chemical signals.

What are the seven characteristics that all living organisms share?

Respond to their environment

Grow and change

Reproduce to have offspring

Have a complex chemistry

Maintain homeostasis

Are built from structure called cells

Pass their traits onto their offspring

What are the four basic components of cellular signalling

• Signalling cell

• Signalling compound

• Receptor (usually a protein)

• Responding cell

Describe how the signalling cell works

The signaling cell releases signaling molecules.Then the responding cell has receptor proteins that bind to the signaling molecule.

What are the two forms of cell signaling?

Inter-cellular signalling (Cell to cell communication)

Intra-cellular signalling (Within cell communication)

How can bacteria ‘tell’ how many other bacteria are present?

They produce signaling molecules At low population density, the concentration of the signaling peptide is too low to bind to the receptors and stimulate DNA uptake. And at high population density, the concentration of the signaling peptide is high enough to bind to the receptors and stimulate DNA uptake.

List the four forms of intercellular signalling 

• Contact-dependent signalling (touching)

• Autocrine (self)

• Paracrine (adjacent, side-by-side)

• Endocrine (within the organism, can be over long distances)

Describe contact- dependent signalling 

Describe autocrine signalling  

Each cell is both a signalling and a responding cell but the basic four component pattern remains the same.

Describe paracrine signalling 

Describe endocrine signalling 

Give two examples of interorganism signalling 

Pheromones

Allelochemicals

Describe pheromones 

compounds that are emitted by an organism that affect members within the same species

Describe allelochemicals

compounds that are emitted by an organism that affect other species.

List characteristics of hormones 

• They are peptides, amines or steroids

• Secreted as needed. Not stored, excess is excreted

• Secretion regulated by autonomic nerves and/or by chemical feedback

• Transported in the blood

• Some cause rapid changes (adrenalin/epinephrine)

• Some cause slower, long-term effects like growth, change in behaviour

eg. sex hormones

• Not enzymes and do not catalyse any reactions

• Function by stimulating or inhibiting the target cells /organs.

Describe chemical characteristics of peptide and amine hormones 

Peptide and amine hormones tend to be hydrophilic, they cannot easily diffuse across the plasma membrane. Detected by cell-surface (transmembrane) receptors.

Describe chemical characteristics of steroid hormones

Steroid hormones are membrane permeable, they diffuse freely across the cell

membrane to bind with receptors in the cytoplasm.