A6- ATP, Water and Inorganic Ions

are inorganic ions soluble or insoluble in water

soluble

give 4 roles of phosphate ions

1. makes hydrophilic part of phospholipids, for cell membranes, allowing bilayer to form

2. component of nucleotides, allowing phosphodiester bonds to form in DNA and RNA

3. component of ATP and ADP, allowing energy release

4. to phosphorylate other substances, making them more reactive

give 2 roles of nitrate ions

1. make amino acids, which join to make proteins

2. make nitrogenous bases for DNA/RNA/ATP/ADP

give 1 role of iron ions

1. make haemoglobin, which binds to oxygen to transport it around the body

give 1 role of hydrogen ions

1. maintain pH levels in the body → high conc = acidic

2. affects enzyme rate of reaction as can cause enzymes to denature

give 3 roles of sodium ions

• for co transport of glucose and amino acids into cells

• involved in action potentials in neurones

• affects water potential of cells / osmosis

describe the structure of ATP

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

• nucleotide derivative

learn to draw a labelled diagram of adenosine triphosphate

okay

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

• coupled to energy requiring reactions within cells (e.g. active transport, protein synthesis)

• inorganic phosphate released can be used to phosphorylate other compounds, making them more reactive

how is ATP hydrolysed

1. ATP breaks down to ADP and Pi

2. in a hydrolysis reaction

3. using ATP hydrolase and a water molecule

4. releasing energy

what can the inorganic phosphate (Pi) released during hydrolysis of ATP be used for?

to phosphorylate other compounds, making them more reactive

describe how is ATP re-synthesised in cells

1. ADP + Pi → ATP (+water)

2. in a condensation reaction, removing water molecule

3. catalysed by ATP synthase

4. during respiration and photosynthesis

when does ATP synthesis occur

during photosynthesis and respiration

• during photosynthesis, light energy is converted into chemical energy through the formation of ATP

• the chemical energy in glucose is converted into chemical energy in ATP during respiration

give 4 uses of ATP

1. active transport

2. muscle contraction

3. protein synthesis

4. cell division

why is ATP so useful? (5)

1. releases energy in small manageable amounts

2. broken down in a one step process

3. makes energy available rapidly

4. phosphorylates substances making them more reactive

5. it cant pass out of cell

contrast the structures of ATP and a nucleotide found in DNA to give 2 differences

1. ATP has ribose whereas DNA nucleotide has deoxyribose

2. ATP has 3 phosphate groups where as DNA nucleotide has 1 phosphate group

3. ATP always has a base adenine whereas DNA nucleotide can have adenine, thymine, guanine or cytosine

learn to draw a labelled diagram of adenosine diphosphate

okay

what is the difference between ATP and ADP

ATP has one more inorganic phosphate

explain how hydrogen bonds occur between water molecules

• water is polar molecule

• slightly negative charged oxygen atoms attract slightly positive charged hydrogen atoms of other water molecules

name 5 properties of water that are important in biology

1. metabolite

2. solvent

3. high specific heat capacity

4. large latent heat of vaporisation

5. strong cohesion between water molecules

explain how these 5 properties of water are important in biology

1. metabolite

2. solvent

3. high specific heat capacity

4. large latent heat of vaporisation

5. strong cohesion between water molecules

1. used in condensation / hydrolysis / photosynthesis / respiration

2. allows metabolic reactions to occur

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

• buffers changes in temperature

• as can gain/ lose heat energy without changing temperature

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

• helps organisms maintain constant internal body temp

4. allows effective cooling via evaporation of a small volume

• so helps organisms maintain a constant internal body temp

5. supports columns of water in tube like transport cells of plants e.g. transpiration stream through xylem vessels

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

define cohesion

the attraction between same-type molecules, particularly water molecules, due to hydrogen bonds, causing them to stick together and form continuous columns

define adhesion

he attraction between molecules of different substances, particularly water molecules sticking to other polar surfaces like the cellulose walls of xylem vessels