C2.1 Chemical Signalling

Quorum Sensing

A change in the behaviour of a colony when its population density reaches a certain threshold

Endocrine glands

Secrete hormones into the bloodstream throughout body

State where neurotransmitters travel in

Only in small space between neurons

Cytokines

Proteins that act as chemical messages within cells

Muscle fibres

Calcium ions bind to a protein on actin to allow myosin heads to attach

Neurons

Causes the release of neurotransmitters from the presynaptic neuron

Similarities between hormones and neurotransmitters

• small

• water soluble

• have a shape compatible with its receptor

Outline what hormones can consist of

• Steroids

• Amines

• Peptides

Outline what neurotransmitters can consist of

• Amines

• Amino Acids

• Esters

• Gases

Esters

Organic compounds that react with water to produce alcohols

Localised Effect

Molecules are closer together

Distant Effect

Molecules are far away from each other

State some structural characteristics of a signalling molecule being able to enter a cell

• Receptor protein is located in cytoplasm/nucleus (inside the cell)

• Intracellular

• Surface of receptor is covered in hydrophilic amino acids

State some structural characteristics of a signalling molecule being unable to enter a cell

• Receptor protein located on the plasma membrane

• Transmembrane

• It has hydrophilic (heads) and hydrophobic (tails) amino acids

Transduction pathway

Sequence of interactions initiated by the ligand binding to the receptor

Intracellular pathways

Ligand enters the cell, binds to receptor

Transmembrane pathway

Ligand binds with the receptor, receptor changes shape

GPCR

G-protein couples receptors (transmembrane receptor proteins)

GDP

Guanosine diphosphate

GTP

Guanosine triphosphate

Explain the binding of the Gs

• When GDP is bound to a G protein, it is inactive

• When a ligand binds to the receptor, GDP is replaced by GTP

Epinephrine =

Adrenaline

Explain the formation of Epinephrine

• Hormone produced by the adrenal glands

• Binds with a G protein

• ATP converted into secondary messenger molecule

• Amplifies the effect

Kinase

Enzyme that removes a phosphate group from ATP and adds it to molecule

Tyrosine kinase

Enzyme that transfers a phosphate from ATP to tyrosine in a protein

Explain how oestradiol affects target cells

• Hypothalamus releases GnRH to pituitary glands

• Pituitary glands releases LH and FSH

• Oestradiol travels through cells of hypothalamus

• Positive feedback

Characteristics of negative feedback loop

• Maintains stable internal conditions (homeostasis)

• Opposes initial stimulus to restore balance

• Automatically adjusts body processes

Characteristic of positive feedback loop

Final product triggers even more production of the product