1.5.2 - ATP

Question 1

What is ATP

Answer 1

• adenosine triphosphate
• a nucleotide in all living cells
• its hydrolysis makes energy available and it is formed when chemical reactions release energy

Question 2

What are the main stores of energy in organisms

Answer 2

• lipids and carbohydrates
• the molecule that makes energy available when it’s needed is adenosine triphosphate (ATP)

Question 3

How do we know ATP is not an energy store?

Answer 3

• we make and break down about 50kg of ATP every day but the body only contains about 5g of ATP, so it is not a store

Question 4

Why is ATP called the universal energy currency of the cell?

Answer 4

• it is involved when energy changes happen in all living organisms
• ATP is synthesised when energy is made available such as in the mitochondria
• it is broken down when energy is needed such as in muscle contraction

Question 5

Describe the structure of ATP

Answer 5

• it is a nucleotide
• based = adenine
• pentose sugar = ribose
• 3 phosphate groups

Question 6

What is ATP described as?

Answer 6

• universal energy currency used in all cells by all organisms

Question 7

Describe how ATP is broken down for energy

Answer 7

• when energy is needed in an organism the enzyme ATPase hydrolyses the bond between the 2nd and 3rd phosphate group, removing the 3rd phosphate group
• the ATP molecule is hydrolysed into adenosine diphosphate and an inorganic phosphate ion with the release of chemical energy

Question 8

When the bond is broken in the hydrolysis of ATP, how much energy is released?

Answer 8

30.6 KJ

Question 9

What is a reaction that releases energy called?
E.g. hydrolysis of ATP

Answer 9

• exergonic reaction

Question 10

Write an equation for the hydrolysis of ATP

Answer 10

………………….. —————>
ATP + Water <————— ADP + Pi ^H = -30.6

^H = delta H
——> = hydrolysis
<—— = condensation

Question 11

Desrcribe the process of ATP synthesis

Answer 11

• in a condensation reaction catalysed by ATP synthetase, ADP and an inorganic phosphate ion can combine to make ATP and water
• this requires an energy input
• every molecule of ATP synthesised requires 30.6 KJ
• a reaction that requires energy input like ATP synthesis is called an ENDERGONIC reaction

Question 12

What is the addition of a phosphate to ADP called?

Answer 12

• phosphorylation

Question 13

What is phosphorylation?

Answer 13

• the addition of a phosphate group

Question 14

What does ATP do?

Answer 14

• transfers energy from energy-rich compounds such as glucose to cellular reactions where it’s needed
• energy transfers are insufficient and some energy is always released as heat
• the uncontrolled release of energy from glucose would produce a temperature increase that would destroy cells
• living organisms release energy gradually in a series of small steps called respiration, producing ATP

Question 15

What are the advantages of using ATP as an intermediate in providing energy compared with using glucose directly?

Answer 15

• hydrolysis of ATP to ADP involves a single reaction that releases energy immediately, breakdown of glucose involves many intermediates and takes longer for energy to be released
• only 1 enzyme is needed to release energy from ATP, many are needed to release energy from glucose
• ATP releases energy in small amounts when and where it’s needed, glucose contain large amounts of energy which would be released all at once (could be insufficient)
• ATP provides a common source of energy for many different chemical reactions, increasing efficiency and control by the cell

Question 16

What are the roles of ATP

Answer 16

ATP provides the necessary energy for cellular activity:
- metabolic processes
- active transport
- movement
- nerve transmission
- secretion (exocytosis)

Question 17

What is the role of ATP in: METABOLLIC PROCESSES

Answer 17

• provides energy to build large complex molecules from smaller simpler molecules
• such as DNA synthesis from nucleotides + proteins from amino acids

Question 18

What is the role of ATP in: ACTIVE TRANSPORT

Answer 18

• provides energy to change the shape of carrier proteins in membranes and allow molecules and ions to move against a concentration gradient

Question 19

What is the role of ATP in: MOVEMENT

Answer 19

• provides energy for muscle contraction, cytokinesis

Question 20

What is the role of ATP in: NERVE TRANSMISSION

Answer 20

• sodium-potassium pumps actively transport sodium and potassium ions across the axon membrane

Question 21

What is the role of ATP in: SECRETION

Answer 21

• ATP provides the energy for packing and transporting secretory products into vesicles in cells

Question 22

Where is ATP synthesised

Answer 22

• in the mitochondria