ATP, Inorganic Ions And Water

Question 1

What is energy required for in all organisms

Answer 1

In anabolic reactions – building larger molecules from smaller molecules

To move substances across the cell membrane (active transport) or to move substances within the cell
In animals, energy is required:

For muscle contraction – to coordinate movement at the whole-organism level
In the conduction of nerve impulses, as well as many other cellular processes

Question 2

What does ATP stand for and what does it do?

Answer 2

Adenosine triphosphate (ATP) is the energy-carrying molecule that provides the energy to drive many processes inside living cells.

Question 3

What is ATP?

Answer 3

ATP is another type of nucleic acid and hence it is structurally very similar to the nucleotides that make up DNA and RNA
It is a phosphorylated nucleotide

ATP is described as a universal energy currency
Universal: It is used in all organisms
Currency: it can be used for different purposes (reactions) and is reused countless times

Question 4

What can the nucleotide adenosine combine with?

Answer 4

Adenosine (a nucleoside) can be combined with one, two or three phosphate groups
One phosphate group = adenosine monophosphate (AMP)
Two phosphate groups = adenosine diphosphate (ADP)
Three phosphate groups = adenosine triphosphate (ATP)

Question 5

What type of molecule is ATP

Answer 5

ATP is a small and soluble molecule that provides a short-term store of chemical energy that cells can use to do work

It is vital in linking energy-requiring and energy-yielding reactions

Question 6

What reasons is ATP as an energy currency beneficial for?

Answer 6

The hydrolysis of ATP can be carried out quickly and easily wherever energy is required within the cell by the action of just one enzyme, ATPase
A useful (not too small, not too large) quantity of energy is released from the hydrolysis of one ATP molecule - this is beneficial as it reduces waste but also gives the cell control over what processes occur
ATP is relatively stable at cellular pH levels

Question 7

The energy released by ADP

Answer 7

As ADP forms free energy is released that can be used for processes within a cell eg. DNA synthesis

Removal of one phosphate group from ATP releases 30.8 kJ mol -1 of energy, forming ADP

Removal of a second phosphate group from ADP also releases 30.8 kJ mol-1 of energy, forming AMP

Removal of the third and final phosphate group from AMP releases 14.2 kJ mol-1 of energy, forming adenosine

Question 8

The hydrolysis of ATP

Answer 8

Hydrolysis of ATP to adenosine diphosphate (ADP) and an inorganic phosphate group (Pi) is catalysed by the enzyme ATP hydrolase sometimes called ‘ATPase’

Question 9

The hydrolysis of ATP can be coupled to energy-requiring reactions within cells such as:

Answer 9

The active transport of ions up a
concentration gradient

Enzyme controlled reactions that require energy

Muscle contraction and muscle fibre movement

Question 10

What is the other product of the hydrolysis of ATP other than ADP?

Answer 10

The inorganic phosphate released during the hydrolysis of ATP can be used to phosphorylate other compounds, often making them more reactive

Question 11

The synthesis of ATP

Answer 11

Organisms cannot build up large stores of ATP and it rarely passes through the cell surface membrane

ATP is formed when ADP is combined with an inorganic phosphate (Pi) group by the enzyme ATP synthase

This is an energy-requiring reaction
Water is released as a waste product (therefore ATP synthesis is a condensation reaction)

Question 12

Types of ATP synthesis

Answer 12

Types of ATP synthesis
ATP is made during the reactions of respiration and photosynthesis
All of an animal’s ATP comes from respiration

ATP can be made in two different ways:
Substrate-linked phosphorylation (occurs in the glycolysis stage of respiration)

Chemiosmosis (occurs in the electron transport chain stage of respiration)

Question 13

The balance of electrons in water

Answer 13

Although water as a whole is electrically neutral the sharing of the electrons is uneven between the oxygen and hydrogen atoms
The oxygen atom attracts the electrons more strongly than the hydrogen atoms, resulting in a weak negatively charged region on the oxygen atom (δ-) and a weak positively charged region on the hydrogen atoms(δ+), this also results in the asymmetrical shape

Question 14

Why is there a separation of charge in water?

Answer 14

This separation of charge due to the electrons in the covalent bonds being unevenly shared is called a dipole. When a molecule has one end that is negatively charged and one end that is positively charged it is also a polar molecule

Water is a polar molecule

Question 15

What properties of water molecules do hydrogen bonds contribute to

Answer 15

An excellent solvent – many substances can dissolve in water
A relatively high specific heat capacity
A relatively high latent heat of vaporisation
Water is less dense when a solid
Water has high surface tension and cohesion
It acts as a reagent

Question 16

Hydrogen bonds in water molecules

Answer 16

Hydrogen bonds form between water molecules
As a result of the polarity of water hydrogen bonds form between the positive and negatively charged regions of adjacent water molecules

Hydrogen bonds are weak, when there are few, so they are constantly breaking and reforming. However when there are large numbers present they form a strong structure

Question 17

Water as a solvent

Answer 17

As water is a polar molecule many ions (e.g. sodium chloride) and covalently bonded polar substances (e.g. glucose) will dissolve in it

This allows chemical reactions to occur within cells (as the dissolved solutes are more chemically reactive when they are free to move about)

Metabolites can be transported efficiently (except non-polar molecules which are hydrophobic)

Question 18

What is specific heat capacity

Answer 18

Specific heat capacity is a measure of the energy required to raise the temperature of 1 kg of a substance by 1oC

Question 19

Why does water have a high specific heat capacity

Answer 19

The high specific heat capacity is due to the many hydrogen bonds present in water. It takes a lot of thermal energy to break these bonds and a lot of energy to build them, thus the temperature of water does not fluctuate greatly

Water has a high specific heat capacity of 4200 J / Kg oC

Question 20

What is the advantage for living organisms that water has a high specific heat capacity?

Answer 20

Provides suitable habitats

Is able to maintain a constant temperature as water is able to absorb a lot of heat without big temperature fluctuations

This is vital in maintaining temperatures that are optimal for enzyme activity

Question 21

The role of water in the blood plasma

Answer 21

helping to maintain a fairly constant temperature

As blood passes through more active (‘warmer’) regions of the body, heat energy is absorbed but the temperature remains fairly constant

Water in tissue fluid also plays an important regulatory role in maintaining a constant body temperature

Question 22

Adavntage of waters high latent heat of vapourisation

Answer 22

In order to change state (from liquid to gas) a large amount of thermal energy must be absorbed by water to break the hydrogen bonds and evaporate

This is an advantage for living organisms as only a little water is required to evaporate for the organism to lose a great amount of heat

This provides a cooling effect for living organisms, for example the transpiration from leaves or evaporation of water in sweat on the skin

Question 23

What is cohesion

Answer 23

Hydrogen bonds between water molecules allows for strong cohesion between water molecules

This allows columns of water to move through the xylem of plants and through blood vessels in animals

Question 24

Cohesion and surface tension

Answer 24

This also enables surface tension where a body of water meets the air, these hydrogen bonds occur between the top layer of water molecules to create a sort of film on the body of water (this is what allows insects such as pond skaters to float)

Question 25

What is adhesion

Answer 25

Water is also able to hydrogen bond to other molecules, such as cellulose, which is known as adhesion

This also enables water to move up the xylem due to transpiration

Question 26

What is an ion

Answer 26

An ion is an atom (or sometimes a group of atoms) that has an electrical charge
An ion that has a +ve charge is known as a cation
An ion that has a -ve charge is known as an anion

Question 27

What is an inorganic ion

Answer 27

An inorganic ion is an ion that does not contain carbon
Inorganic ions play an important role in many essential cellular processes

Question 28

When do inorganic ions occur

Answer 28

Inorganic ions occur in solution in the cytoplasm and body fluids of organisms
Some occur in high concentrations and others in very low concentrations

The concentration of certain ions can fluctuate and can be used in cell signalling and neuronal transmission

Question 29

Hydrogen ions (H+)

Answer 29

Hydrogen ions are protons
The concentration of H+ in a solution determines the pH

There is an inverse relationship between the pH value and the hydrogen ion concentration

The more H+ ions present, the lower the pH (the more acidic the solution)
The fewer H+ ions present, the higher the pH (the more alkaline the solution)

Question 30

Why is the concentration of (H+) ions important for enzyme controlled reactions.

Answer 30

The maintenance of this normal pH is essential for many of the metabolic processes that take place within cells

Changes in pH can affect enzyme structure

For example, abnormal levels of hydrogen ions can interact with the side-chains of amino acids and change the secondary and tertiary structures of the proteins that make up enzymes

This can cause denaturation of enzymes

Question 31

Why are iron ions essential for binding oxygen

Answer 31

Haemoglobin is the large protein in red blood cells that is responsible for transporting oxygen around the body

Haemoglobin is made up of four polypeptide chains that each contain one Fe2+

This Fe2+ is a key component in haemoglobin as it binds to oxygen

Myoglobin in muscles functions in a similar way (it is an oxygen-binding protein) but is only made up of one polypeptide chain (containing one Fe2+)

Question 32

The different versions of iron ions

Answer 32

There are actually two versions of iron ions (known as oxidation states)

Iron (II) ions, also known as ferrous ions (Fe2+)

Iron (III) ions, also known as ferric ions (Fe3+)

Question 33

How are iron ions essential for the transfer of electrons

Answer 33

Iron ions are an essential component of cytochromes (that are themselves a component of electron transport chains)

Cytochrome c contains an iron ion that is essential to its function

During the electron transport process, this iron ion switches between the Fe3+ and Fe2+ oxidation states, which allows for electrons to be accepted and donated

Question 34

What roles does the Na+ ion have?

Answer 34

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

Na+ is also required for the transmission of nerve impulses, muscle contraction and regulating fluid in the body

Question 35

Na+ role in co-transport

Answer 35

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

This process is known as co-transport

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 36

Phosphate Ions PO43- as essential components of DNA, RNA and ATP

Answer 36

In DNA and RNA, the phosphate groups allow individual nucleotides to join up (to form polynucleotides)

In ATP, the bonds between phosphate groups store energy

These phosphate groups can be easily attached or detached

When the bonds between phosphate groups are broken, they release a large amount of energy, which can be used for cellular processes

Question 37

Where else are phosphate ions found

Answer 37

Phosphates are also found in phospholipids, which are key components of the phospholipid bilayer of cell membranes

Question 38

Ca2+ being essential in the movement of organisms:

Answer 38

Ca2+ is essential in the movement of organisms:
In synapses, calcium ions regulate the transmission of impulses from neurone to neurone

Question 39

Ca2+ also stimulating muscle contraction

Answer 39

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 40

What can Ca2+ ions help regulate

Answer 40

protein channels, which affects the permeability of cell membranes

Question 41

Why are Ca2+ ions these ions key regulators in many biological reactions

Answer 41

Many enzymes are activated by Ca2+

Question 42

Potassium ions K+

Answer 42

• important to generate nerve impulses, muscle contraction and regulating fluid balance in the body
• activating essential enzymes needed for photosynthesis and plant cells.

Question 43

Hydrogen ions (H+)

Answer 43

Affects PH of substances (more conc = more acidid)

Also important for photosynthesis reaction that oocur in thylkaloid membranes inside chloroplasts

Question 44

Ammonium (NH4+)

Answer 44

Absorbed from the soil by plants and is an important source of nitrogen (which is then used to make eg amino acids nucleic)

Question 45

Hydrogen carbonate (HCO3-)

Answer 45

Acts as a buffer which helps maintain the PH of blood

Question 46

Chloride (Cl-)

Answer 46

Involved in the chloride shift which helps maintain the ph of blood during gas exchange

Acts as a cofactor for the enxyme amylase

Involves in some nerve pulses

Question 47

Hydroxide (OH-)

Answer 47

Affects ph pf substances (more concentrated = more alkali)