1.6.4 Inorganic Ions

Question 1

An ion is

Answer 1

an atom (or sometimes a group of atoms) that has an electrical charge

Question 2

An ion that has a +ve charge is known as

Answer 2

a cation

Question 3

An ion that has a -ve charge is known as

Answer 3

anion

Question 4

An inorganic ion is an ion that does not contain

Answer 4

carbon

Question 5

Inorganic ions occur in solution in

Answer 5

the cytoplasm and body fluids of organisms

Question 6

The concentration of certain ions can fluctuate and can be used in

Answer 6

cell signalling and neuronal transmission

Question 7

You should know the following inorganic ions, as well as their properties and roles in the body:

Answer 7

• hydrogen ions (H+)
• iron ions (Fe2+/Fe3+)
• sodium ions (Na+)
• phosphate ions (PO43-)
• calcium ions (Ca2+)

Question 8

Hydrogen ions are

Answer 8

protons

Question 9

The concentration of H+ in a solution determines

Answer 9

the pH

Question 10

There is an inverse relationship between

Answer 10

the pH value and the hydrogen ion concentration

Question 11

The more H+ ions present, the

Answer 11

lower the pH (the more acidic the solution)

Question 12

The fewer H+ ions present, the

Answer 12

higher the pH (the more alkaline the solution)

Question 13

The concentration of H+ is therefore very important for

Answer 13

enzyme-controlled reactions, which are all affected by pH

Question 14

The fluids in the body normally have a pH value of approximately

Answer 14

7.4

Question 15

The maintenance of this normal pH is essential for many of

Answer 15

the metabolic processes that take place within cells

Question 16

Changes in pH can affect

Answer 16

enzyme structure

Question 17

For example, abnormal levels of hydrogen ions can interact with

Answer 17

the side-chains of amino acids

Question 18

For example, abnormal levels of hydrogen ions can interact with the side-chains of amino acids and change

Answer 18

the secondary and tertiary structures of the proteins that make up enzymes

Question 19

Changes in pH can affect enzyme structure, for example, abnormal levels of hydrogen ions can

Answer 19

interact with the side-chains of amino acids and change the secondary and tertiary structures of the proteins that make up enzymes

Question 20

This can cause

Answer 20

denaturation of enzymes

Question 21

There are two versions of iron ions known as

Answer 21

oxidation states

Question 22

Iron (II) ions, also known as

Answer 22

ferrous ions (Fe2+)

Question 23

Iron (III) ions, also known as

Answer 23

ferric ions (Fe3+)

Question 24

Iron ions are essential as they can

Answer 24

bind oxygen

Question 25

Haemoglobin is the large protein in red blood cells that is responsible for

Answer 25

transporting oxygen around the body

Question 26

Haemoglobin is made up of

Answer 26

four polypeptide chains that each contain one Fe2+

Question 27

This Fe2+ is a key component in haemoglobin as it

Answer 27

binds to oxygen

Question 28

Myoglobin in muscles functions in a similar way (it is an oxygen-binding protein) but is only made up of

Answer 28

one polypeptide chain (containing one Fe2+)

Question 29

Iron ions are also essential as they are involved in

Answer 29

the transfer of electrons during respiration and photosynthesis

Question 30

Iron ions are an essential component of

Answer 30

cytochromes (that are themselves a component of electron transport chains)

Question 31

Cytochrome c contains an iron ion that is essential to its function, during the electron transport process, this iron ion switches between

Answer 31

the Fe3+ and Fe2+ oxidation states

Question 32

During the electron transport process, this iron ion switches between the Fe3+ and Fe2+ oxidation states, which allows

Answer 32

for electrons to be accepted and donated

Question 33

Na+ is required for

Answer 33

the transport of glucose and amino acids across cell-surface membranes (e.g. in the small intestine)

Question 34

Glucose and amino acid molecules can only enter cells (through carrier proteins) alongside

Answer 34

Na+

Question 35

Glucose and amino acid molecules can only enter cells (through carrier proteins) alongside Na+, this process is known as

Answer 35

co-transport

Question 36

Co-transport: first

Answer 36

Na+ is actively transported out of the epithelial cells that line the villi

Question 37

Co-transport: then

Answer 37

the Na+ concentration inside the epithelial cells is now lower than the Na+ concentration in the lumen of the small intestine

Question 38

Co-transport: finally

Answer 38

Na+ now re-enters the cells (moving down the concentration gradient) through co-transport proteins on the surface membrane of the epithelial cells, allowing glucose and amino acids to enter at the same time

Question 39

Co-transport process

Answer 39

- first, Na+ is actively transported out of the epithelial cells that line the villi - the Na+ concentration inside the epithelial cells is now lower than the Na+ concentration in the lumen of the small intestine - Na+ now re-enters the cells (moving down the concentration gradient) through co-transport proteins on the surface membrane of the epithelial cells, allowing glucose and amino acids to enter at the same time

Question 40

Na+ is also required for

Answer 40

the transmission of nerve impulses

Question 41

PO43- attaches to other molecules to form

Answer 41

phosphate groups

Question 42

PO43- attaches to other molecules to form phosphate groups, which are an essential component of

Answer 42

DNA, RNA and ATP

Question 43

In DNA and RNA, the phosphate groups allow

Answer 43

individual nucleotides to join up (to form polynucleotides)

Question 44

In ATP, the bonds between phosphate groups

Answer 44

store energy

Question 45

In ATP, the bonds between phosphate groups store energy, these phosphate groups can be easily

Answer 45

attached or detached

Question 46

When the bonds between phosphate groups are broken

Answer 46

they release a large amount of energy, which can be used for cellular processes

Question 47

Phosphates are also found in

Answer 47

phospholipids

Question 48

Phosphates are also found in phospholipids, which are key components of

Answer 48

the phospholipid bilayer of cell membranes

Question 49

Ca2+ is essential in

Answer 49

the movement of organisms

Question 50

In synapses, calcium ions regulate

Answer 50

the transmission of impulses from neurone to neurone

Question 51

Ca2+ also stimulates

Answer 51

muscle contraction

Question 52

Ca2+ also stimulates muscle contraction, when an impulse reaches a muscle fibre

Answer 52

Ca2+ is released from the sarcoplasmic reticulum

Question 53

When an impulse reaches a muscle fibre, Ca2+ is released from the sarcoplasmic reticulum, this Ca2+ binds to

Answer 53

troponin C, removing the tropomyosin from myosin-binding sites on actin

Question 54

When an impulse reaches a muscle fibre, Ca2+ is released from the sarcoplasmic reticulum, this Ca2+ binds to troponin C, removing the tropomyosin from myosin-binding sites on actin, this allows

Answer 54

actin-myosin cross-bridges to form when the muscle fibre contracts

Question 55

Muscle contraction process

Answer 55

- when an impulse reaches a muscle fibre, Ca2+ is released from the sarcoplasmic reticulum - this Ca2+ binds to troponin C, removing the tropomyosin from myosin-binding sites on actin - this allows actin-myosin cross-bridges to form when the muscle fibre contracts

Question 56

Ca2+ can also help to regulate

Answer 56

protein channels,

Question 57

Ca2+ can also help to regulate protein channels, which affects

Answer 57

the permeability of cell membranes

Question 58

Many enzymes are activated by

Answer 58

Ca2+, making these ions key regulators in many biological reactions

Question 59

The presence of Ca2+ is also necessary for the formation of

Answer 59

blood clots (it is known as a clotting factor)