BRAINCAKEImportant Cations
Cations are positively charged ions. Like anions, they are needed in small amounts but have very specific jobs.
Calcium (Ca2+). Calcium phosphate gives bones and teeth their strength. Ca2+ ions trigger the release of neurotransmitter at synapses, allow muscle contraction by exposing binding sites on actin, and are needed for blood clotting. In plants, calcium pectate helps to hold neighbouring cell walls together.
Sodium (Na+). Sodium ions are pumped out of cells by the sodium–potassium pump. The resulting gradient is used for nerve impulses and to absorb glucose and amino acids in the small intestine by co-transport. Sodium also affects the water potential of body fluids.
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Key terms in this lesson
- co-transport
- The movement of one substance across a membrane linked to, and powered by, the movement of another substance down its concentration gradient.
- resting potential
- The electrical potential difference across the membrane of a neurone when it is not conducting an impulse, about minus 70 mV, inside negative.
More in Chemistry for Life
- Ionic Bonding
- Covalent Bonding
- Important Anions
- Water
- Water as a Polar Solvent
- Water as a Transport Medium
- Water as a Habitat
- Water in Plant Transport Systems
All 10 lessons in Chemistry for Life · All Edexcel AS-level Biology topics