ATP and Water

Question 1

What does ATP stand for?

Answer 1

Adenosine triphosphate

Question 2

What is ATP?

Answer 2

A molecule made of a ribose sugar, an adenine base and 3 phosphate groups.

Question 3

Draw the structure of an ATP molecule.

Answer 3

From left to right…

Rectangle —>
Adenine base

Pentagon (pentose) —>
Ribose sugar

3 Circles —>
Phosphates

Question 4

What does ADP stand for?

Answer 4

Adenosine diphosphate

Question 5

What is ADP?

Answer 5

A molecule made of a ribose sugar, an adenine base and 2 phosphate groups.

Question 6

What is the reaction involving ATP and ADP?

Answer 6

ATP + H2O ⇌ ADP + Pi

Question 7

What are the enzymes involved? Name the exo and endo directions.

Answer 7

ATP hydrolase (forward reaction exothermic)

and

ATP synthase (backward reaction endothermic)

Question 8

What is Pi?

Answer 8

Inorganic phosphate group that is produced.

P = phosphorus
i = Inorganic

Question 9

What does ATP hydrolysis do?

Answer 9

Releases energy.

The energy produced is used to drive an energy-requiring reaction.

Question 10

What processes use the energy released from ATP?

Answer 10

Active transport
Cell division
Muscle contraction
Heat
Synthesis of organic molecules
Secretory activities (glands producing hormones)

Question 11

What is organic and inorganic?

Answer 11

Organic =
Molecule containing carbon

Inorganic =
Molecule not containing carbon.

Question 12

What is an exergonic reaction?

Answer 12

A reaction that releases energy.

Question 13

Give examples of an exergonic reaction.

Answer 13

ATP hydrolysis

Respiration

Question 14

What is an endergonic reaction?

Answer 14

A reaction that requires energy.

Question 15

Give examples of an endergonic reaction.

Answer 15

Photosynthesis

Protein synthesis

Question 16

What is the role of ATP?

Answer 16

1~ ATP hydrolysis is exergonic, so there’s a release of free energy.
2~ Enzymes help couple the energy to endergonic reactions (which absorbs energy)
3~ The molecules in the endergonic reaction are PHOSPHORYLATED and is more reactive than before.
4~ Molecules join together to form product, and Pi is produced (phosphate is removed).
5~ ATP is resynthesised as Pi joins to and ADP to form ATP.

Question 17

What are the advantages of hydrolysing ATP instead of glucose directly?

Answer 17

+ Energy is released very rapidly - only single bond broken, whereas in glucose a number of bonds are broken (which takes more time) - energetically more favourable.

+ Provides energy in small and usable amounts - glucose releases too much energy.

Question 18

What are the features of ATP?

Answer 18

A = amount of energy released is SMALL - can be coupled to energy-requiring reactions (endergonic) which don’t need too much energy - less energy wasted as heat.

T = ta da! Energy is released in a SINGLE reaction - very rapid, less time-consuming.

P = Pi (inorganic phosphate) released during ATP hydrolysis can be used to phosphorylate substances to make them MORE REACTIVE.

= Soluble =
Small & soluble so it can be easily transported around the cell.

= Cannot diffuse =
Can’t diffuse out of cell, meaning the cell will not run out of energy.

Question 19

What does phosphorylation mean?

Answer 19

When a molecule gains a phosphate group.

Question 20

What happens to the ‘Pi’ that’s released?

Answer 20

= Phosphorylation =
Joins to molecules to make them more reactive.

= DNA & RNA =
In the phosphate-sugar backbone of DNA & RNA.

= In Phospholipids =
Make up phospholipids.

Question 21

What is the name of the reaction where ADP is produced?

Answer 21

Hydrolysis

ATP hydrolysis

Question 22

What is the name of the reaction where ATP is produced?

Answer 22

Condensation

ATP synthesis

Question 23

What is the formula for a phosphate ion?

Answer 23

PO₄³⁻

Question 24

What is the water potential of pure water?

Answer 24

0

Question 25

Water moves by…

Answer 25

diffusion & osmosis.

Question 26

Which substances, out of glucose, glycogen, starch and cellulose can dissolve in water?

Answer 26

Glucose can dissolve in water.

Cellulose, starch and glycogen cannot dissolve in water.

Question 27

What happens to the water potential if something dissolves in water?

Answer 27

It decreases to the negatives.

0 is the maximum it can go.

Question 28

Why do water and oil not interact with each other?

Answer 28

Water is polar, and oil is non-polar, so they cannot form hydrogen bonds.

Question 29

What does hydrophobic mean?

Answer 29

Will not mix/interact with water.

Question 30

What does hydrophilic mean?

Answer 30

Will mix/interact with water.

Question 31

What are the properties of water?

Answer 31

Strong cohesion =
H₂O has strong cohesion between water molecules due to H bonding - produces surface tension for small aquatic animals
Strong cohesion also supports columns of water in the transport cells of plants.

Metabolite =
H₂O is a metabolite in many metabolic reactions, including condensation & hydrolysis.

Solvent =
So metabolic reactions occur AND allows transport of substances.

High specific heat capacity =
So good at buffering changes in temperature.

High latent heat of vaporisation =
Provides a cooling effect through evaporation.

Question 32

What is a metabolite?

Answer 32

A product or reactant involved in metabolism.

Question 33

What is metabolism?

Answer 33

The sum of all chemical reactions that occur within living organisms.

Question 34

What reactions use water as a metabolite?

Answer 34

Condensation / Hydrolysis

Photosynthesis / Respiration

Question 35

Give 5 properties of water that are important in biology. Explain the importance of each property you identify. [4 marks]

Answer 35

1 = A metabolite IN condensation/hydrolysis/photosynthesis/respiration.

2 = A solvent SO metabolic reactions can occur and allows transport of substances.

3 = High specific heat capacity SO buffers changes in temperature.

4= Large latent heat of vaporisation SO provides a cooling effect (through evaporation).

5= Strong cohesion (between water molecules) SO provides surface tension supporting (small) organisms.

6 = Strong cohesion SO supports column of water (in plants)

Question 36

Why is solid ice less dense than liquid water?

Answer 36

As water freezes, molecules have less energy - no longer break their H bonds - become locked into a lattice structure - H bonds keep molecules further apart - making it less dense.

Question 37

What are the properties of ice?

Answer 37

Insulator =
Ability of ice to float means it acts as an insulator - prevents water below from freezing and allowing life to exist below the surface and preserves habitats.