1- ATP, Water, Inorganic ions

What is ATP?

Adenine triphosphate

Describe the structure of ATP

• Ribose bound to a molecule of adenine (base) and 3 phosphate groups

• Nucleotide derivative (modified nucleotide)

Describe how ATP is broken down

ATP (+ water)—> ADP (adenosine diphosphate) + Pi (inorganic phosphate)

• Hydrolysis reaction, using a water molecule

• Catalysed by ATP hydrolase (enzyme)

Give 2 ways in which the hydrolysis of ATP is used in cells

• Coupled to energy requiring reactions within cells (releases/ provides energy) - e.g. active transport, protein synthesis

• Inorganic phosphate released can be used to phosphorylate (add phosphate to) other compounds, making them more reactive

Describe how ATP is resynthesised in cells

• ADP + Pi—> ATP (+water)

• Condensation reaction, removing a water molecule

• Catalysed by ATP synthase (enzyme)

• During respiration and photosynthesis

Suggest how the properties of ATP make it a suitable immediate source of energy for cells

• releases energy in (relatively) small amounts/ little energy lost as heat

• single reaction/ one bond hydrolysed to release energy (so immediate release)

• cannot pass out of cell

What is water?

a major component of cells

Explain how hydrogen bonds occur between water molecules

• water is a polar molecule

• slightly negatively charged oxygen atoms attract slightly positively charged hydrogen atoms of other water molecules

What are the 5 properties of water?

• metabolite

• solvent (can dissolve solutes)

• high specific heat capacity

• large latent heat of vaporisation

• strong cohesion and surface tension between water molecules

What is the importance of water being a metabolite?

used in condensation/ hydrolysis/ photosynthesis/ respiration

What is the importance of water being a solvent (can dissolve solutes)?

• allows metabolic reactions to occur (faster in solution)

• allows transport of substances e.g. nitrates in xylem, urea in blood

What is the importance of water having high specific heat capacity?

• buffers changes in temperature

• as can gain/ lose a lot of heat/ energy without changing temperature

• good habitat for aquatic organisms as temperature more stable than land

• helps organisms maintain a constant internal body temperature

What is the importance of water having large latent heat of vaporisation?

• allows effective cooling via evaporation of a small volume (e.g. sweat)

• so helps organisms maintain a constant internal body temperature

What is the importance of water having strong cohesion and surface tension between water molecules?

• supports columns of water e.g. transpiration stream through xylem in plants

• produces surface tension, supporting small organisms (to walk on water)

Where are inorganic ions found in the body?

in solution in cytoplasm and body fluid, some in high concentrations and others in very low concentrations

Describe the role of hydrogen ions

• maintain pH levels in the body—> high conc= acidic/ low pH

• affects enzyme rate of reaction as can cause enzymes to denature

Describe the role of iron ions

• component of haem group of haemoglobin

• allowing oxygen to bind/ associate for transport of oxyhaemoglobin

Describe the role of sodium ions

• involved in co-transport of glucose/ amino acids into cells

• involved in action potentials in neurons

• affects water potential of cells/ osmosis

Describe the role of phosphate ions

• component of nucleotides. allowing phosphodiester bonds to form in DNA/ RNA

• component of ATP, allowing energy release

• phosphorylates other compounds making them more reactive

• hydrophilic part of phospholipids, allowing a bilayer to form