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ENERGY, ATP AND INORGANIC IONS
ENERGY AND ATP

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All living organisms need energy to stay alive
Comes initially from the sun
o Plants use solar energy to combine water and CO2 into complex organic molecules via
photosynthesis
o Plants and animals then oxidise these organic molecules to form adenosine
triphosphate, the main energy carrier molecule in cells

STRUCTURE OF ATP

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ATP IS A NUCLEOTIDE
Adenine bonded to a ribose sugar (the backbone) bonded to three phosphate groups
The bonds between these phosphates are unstable, low activation energy, easily broken
When they do break, they release a considerable amount of energy
Usually in living cells only the terminal phosphate is removed¸ to form ADP ~
Water is used to convert ATP to ADP, this is a HYDROLYSIS REACTION
It also requires an enzyme- ATPhydrolase or ATPase for short

SYNTHESIS OF ATP

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Conversion of ATP to ADP is a reversible reaction, energy can be sued to add an inorganic
phosphate to ADP to reform ATP and release water
CONDENSATION REACTION
Catalysed by ATP Synthase
Involves the addition of a phosphate group to ADP and can happen in several ways:
o In chlorophyll containing plant cells during photosynthesis, photophosphorylation
o In plant and animal cells during respiration, oxidative phosphorylation
o When phosphate groups are transferred from donor molecules to ADP, substrate level
phosphorylation

ROLES OF ATP

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Instability of phosphate bonds means ATP = GREAT energy donor but a REAL SHIT long term
energy store
o Which is why we still need fats and carbs
ATP = the immediate energy source of a cell

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Only a few seconds supply is maintained, not a problem as ATP is rapidly reformed from ADP
and inorganic phosphate
HERE’S WHY IT’S BETTER THAN GLUCOSE AS AN IMMEDIATE SOURCE OF ENERGY
o Each ATP molecule releases less energy than each glucose molecule- energy is
released in smaller, more manageable quantities, less wasted as heat
o Glucose takes a long series of reactions to break down fully, hydrolysis of ATP is a
single reaction, releases energy immediately
ATP can’t be stored, must be continuously made, hello mitochondria, lots in muscle fibres and
small intestine epithelium cells

ATP IS USED FOR…

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Metabolic processes, building macromolecules, breaking them down
Movement, provides E for filaments of muscles to slide past each other, muscle contraction
Active transport, E for protein carriers to change shape
Secretion, E for formation of lysosomes
Activation of molecules, inorganic phosphate can be used to phosphorylate other
compounds and make them more reactive
o Eg in glycolysis

WATER IS COOL AS
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Major component of cells
Dipolar, forms hydrogen bonds, leads to a number of WEIRD PROPERTIES
Water is a MAJOR RAW MATERIAL IN PHOTOSYNTHESIS
Water is used to break down complex molecules VIA HYDROLYSIS
Water is a solvent, and provides an aqueous medium in which reactions can take place
o Readily dissolves gases
o Dissolves inorganic ions, small hydrophilic molecules such as amino acids,
monosaccharides, ATP
o Enzymes
o Allows molecules to meet and so react,
Water has a high specific heat capacity
o Because of H bonds, water molecules have a lot of cohesion, takes a lot of energy to
break the molecules apart and heat water
o Means water makes a great buffer against sudden temperature change
Water has a high latent heat of vaporisation
o Because of aforementioned cohesion, takes a lot of heat to evaporate water… means
that sweating is a rly effective way of losing heat for mammals
Water has cohesion
o Means water can be pulled up xylem

When water molecules meet air they tend to be pulled back into body of water,
surface tension, allows small organisms to skate across water ~~~
Water is not easily compressed
o Can provide support, hydrostatic skeleton of earthworm, turgour pressure in
herbaceous plants
Water is transparent
o Aquatic plants can photosynthesis
o Light can reach retina through jelly like solution in eye
Water is at its densest at 4 degrees
o Idk why
o But means during ice age, the top layers of water would freeze, NOT SINK and so
insulate the remaining water and allow life to continue
o Pretty neat right
o

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INORGANIC IONS

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Occur in cytoplasm of cells, body fluids, as parts of larger molcules
Occur in varying concentrations
A range of functions
o Iron in haemoglobin plays a role in transport of oxygen
o Phosphates = structural in DNA and ATP
o Hydrogen ions determine pH and therefore FUNCTIONING OF ENZYMES
o Sodium in co-transport of glucose and amino acids across plasma membranes
o Potassium and sodium in maintaining membrane potential in neurones
o Calcium in synaptic vesical migration



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