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Why do organisms need energy? (Describe which processes an organism requires energy for)

-Metabolism/ metabolic processes
-Movement- muscle contraction, circulation of blood
-Active transport of substances against their concentration gradient
-Maintenance, repair and division of cells
-Production of substances (eg hormones, enzymes)
-Maintenance of body temperature (in endotherms)


What are the three stages of energy flow through living systems?

-Light energy from the sun converted into chemical energy through photosynthesis
-Chemical energy from photosynth. (in the form of organic molecules) is converted into ATP during respiration
-ATP used by cells to perform useful work


How does ATP store energy?

The bonds between the phosphate groups in ATP are unstable and therefore have a low activation energy (bonds are easily broken). When they do break, they release a considerable amount of energy.


Describe the hydrolysis reaction in which water causes energy to be released.

ATP + water --> ADP + Pi + energy


Describe how ATP can be synthesised through a condensation reaction.

Opposite of hydrolysis of ATP reaction.


What are the three ways in which ATP is formed from ADP? (Hint- what are the three types of phosphorylation?)

-Phosphorylation- takes place in chlorophyll containing plant cells during photosynthesis
-Oxidative phosphorylation- occurs in the electron transport chain
-Substrate level phosphorylation- occurs in both plant and animal cells. When phosphate groups are transferred from donor molecules to ADP to form ATP (eg in the formation of pyruvate at the end of glycolysis)


Which 5 processes is ATP the source of energy for?

-Metabolic processes- the energy is needed to build up macromolecules from their basic units
-Movement- muscle contraction
-Active transport- change of shape of carrier proteins in plasma membranes
-Secretion-ATP needed to form lysosomes necessary for the secretion of cell products
-Activation of other molecules- when a phosphate is added to another molecule it makes it more reactive


Why is ATP a better immediate energy source than glucose?

-Each ATP releases less energy than a molecule of glucose- smaller and more manageable quantities

-Hydrolysis of ATP to ADP is a single reaction that releases immediate energy- breakdown of glucose takes longer through a long series of reactions



(6 marks)
Plants produce ATP in their chloroplasts during photosynthesis. They also produce
ATP during respiration. Explain why it is important for plants to produce ATP during
respiration in addition to during photosynthesis.

1. In the dark no ATP
production in
2. Some tissues unable to
3. ATP cannot be moved from
cell to cell/stored;
4. Plant uses more ATP than
produced in photosynthesis;
5. ATP for active transport;
6. ATP for synthesis of named substance


Describe how ATP is made in mitochondria.

1. Substrate level
phosphorylation / ATP
produced in Krebs cycle;
2. Krebs cycle/link reaction
produces reduced
NAD/reduced FAD;
3. Electrons released from
reduced /coenzymes/
4. (Electrons) pass along
carriers/through electron
transport chain/through series
of redox reactions;
5. Energy released;
6. ADP/ADP + Pi;
7. Protons move into
intermembrane space;
8. ATP synthase;


ATP is useful in many biological processes. Explain why.

1. Releases energy in small /
manageable amounts;
2. (Broken down) in a one step /
single bond broken;
3. Immediate energy
compound/makes energy
available rapidly;
4. Phosphorylates/adds
5. Makes (phosphorylated
substances) more reactive /
lowers activation energy;
6. Reformed/made again;