inorganic ions 1

What are the roles of

inorganic ions in the

body?

occur in cytoplasm and body fluids, in

varying concentrations

H+ ions: affect pH

Fe2+ ions: component of haemoglobin

Na+ ions: involved in co-transport of

glucose and amino acids

PO43− ions: found in DNA and ATP (form

phosphodiester bonds)

Role of

hydrogen ions

determine the pH

the more hydrogen ions, the more

acidic the conditions are

an important role in chemiosmosis

in respiration and photosynthesis

Role of

iron ions

a compound of haemoglobin

involved in oxygen transport

Role of sodium ions

in co-transport

involved in co-transport for absorption of glucose and amino acids in the ileum

Involved in action potentials in neurons

Affects water potential of cells / osmosis

Role of

phosphate ions

1. Component of nucleotides, allowing phosphodiester bonds to form in DNA / RNA

2. Component of ATP, allowing energy release

3. Phosphorylates other compounds making them more reactive

4. Hydrophilic part of phospholipids, allowing a bilayer to form (1.3 / 2.3)

Exam insight: common mistakes ❌

What is an inorganic ion?

A charged atom or molecule that contains no carbon–hydrogen bonds.

Why are inorganic ions essential for biological processes?

They allow critical biochemical and physiological processes to occur.

What does it mean that ions can exist in different concentrations in different locations?

Ion concentrations vary inside/outside cells depending on function.

Why is the specific function of an ion determined by its charge?

Charge determines how ions interact with molecules and enzymes.

What ion is represented by Fe²⁺?

An iron(II) ion.

What is the role of Fe²⁺ ions in haemoglobin?

It forms the central part of each haem group in haemoglobin.

Why is Fe²⁺ essential for oxygen transport?

Fe²⁺ binds oxygen molecules.

What happens to Fe²⁺ when oxygen binds to haemoglobin?

It is temporarily oxidised to Fe³⁺ when oxygen attaches.

How does Fe²⁺ enable reversible oxygen binding?

The iron returns to Fe²⁺ when oxygen is released, allowing reversibility.

What ion is represented by H⁺?

A hydrogen ion.

How do H⁺ ions relate to pH?

pH is a measure of H⁺ concentration.

What does a high concentration of H⁺ ions indicate about pH?

High H⁺ = low pH (acidic).

What does a low concentration of H⁺ ions indicate about pH?

Low H⁺ = high pH (alkaline).

Why is pH important for enzyme activity?

pH affects the shape and charge distribution of enzyme active sites.

How do H⁺ ions affect the tertiary structure of enzymes?

Alters ionic and hydrogen bonding, modifying tertiary structure.

What ion is represented by Na⁺?

A sodium ion.

Why are Na⁺ ions essential in co-transport?

Na⁺ diffusion drives the co-transport of glucose and amino acids.

How does Na⁺ help transport glucose across the intestinal epithelium?

Glucose enters cells coupled to Na⁺ moving down its gradient.

Why is Na⁺ required to maintain the electrochemical gradient for co-transport?

The Na⁺ gradient powers secondary active transport.

How do Na⁺ ions contribute to nerve impulse transmission?

Na⁺ movement contributes to changes in electrical potential across membranes.

What ion is represented by PO₄³⁻?

A phosphate ion.

What is the role of phosphate ions in ATP?

Forms part of ATP and is released as inorganic phosphate (Pi) during hydrolysis.

Why is PO₄³⁻ critical for energy transfer in cells?

Its transfer releases or stores chemical energy.

What role does PO₄³⁻ play in DNA structure?

Forms part of the sugar-phosphate backbone in DNA.

Why is the phosphate group essential in RNA structure?

Also forms the backbone in RNA.

How do phosphate ions contribute to polynucleotide backbone formation?

Provides strong covalent links between nucleotides.

Why are phosphate ions important in phosphorylation reactions?

Adding phosphate can activate molecules and enzymes.

How does PO₄³⁻ help regulate enzyme activity?

It changes shape/energy state of proteins, altering function.

Why are phosphate ions essential for plasma membrane function?

Phosphate forms the hydrophilic head in phospholipids.

How do inorganic ions contribute to maintaining osmotic balance?

Ion movement influences water potential and fluid balance.

Why are ions such as Na⁺ and K⁺ essential for generating membrane potentials?

They generate electrochemical gradients used in signalling and transport.

How do Ca²⁺ ions (though not specifically named in the spec, still part of inorganic ions) contribute to muscle contraction?

Ca²⁺ triggers interaction between actin and myosin in contraction.

Why do different inorganic ions carry out very specific functions despite all being simple charged particles?

Each ion’s charge and size dictate unique biochemical interactions.

Why is the concentration of each ion tightly regulated in cells?

To maintain enzyme function, osmotic balance and membrane potentials.

What happens when ion concentrations deviate from their normal range?

Enzyme failure, disrupted signalling, or osmotic damage may occur.

How does the cell membrane help control ion concentrations?

Through channel proteins, pumps and controlled permeability.

Why is the movement of ions fundamental to homeostasis?

Ion gradients regulate pH, water balance and electrical activity.

How do inorganic ions assist in enzyme-controlled reactions generally?

They act as cofactors or influence charge interactions.

How does the presence of inorganic ions support structural molecules?

Ions stabilise structures such as DNA and proteins.

Why do ions play a role in buffering systems in the body?

They help resist pH changes by binding or releasing H⁺.