ATP +water +ions

Question 1

what are the uses of energy?

Answer 1

1. active transport (any named process) : glucose absorption, ion uptake at roots etc.
2. muscle contraction : for movement
3. protein synthesis : for growth and repair
4. phosphorylation : making molecules more reactive by lowering their activation energy

Question 2

what is ATP?

Answer 2

the energy from respiration takes the form of a nucleotide called adenosine triphosphate (ATP)

Question 3

Describe the structure of ATP

Answer 3

● Ribose bound to a molecule of adenine
(base) and 3 phosphate groups
● Nucleotide derivative (modified nucleotide)

Question 4

how is energy released?

Answer 4

-the bonds between the outer phosphate groups in ATP are unstable, so have a low activation energy
-a single hydrolysis reaction can remove a phosphate. The phosphate can form bonds with other molecules which releases energy (phosphorylation)

Question 5

Describe how ATP is broken down

Answer 5

● ATP (+ water) → ADP (adenosine diphosphate) + Pi (inorganic phosphate) + energy
● Hydrolysis reaction, using a water molecule
● Catalysed by ATP hydrolase (enzyme ATPase)

Question 6

Give two ways in which the hydrolysis of ATP is used in cells

Answer 6

● Coupled to energy requiring reactions within cells (releases energy)
○ eg. active transport, protein synthesis
● Inorganic phosphate released can be used to phosphorylate
(add phosphate to) other compounds, making them more reactive

Question 7

Describe how ATP is resynthesised in cells

Answer 7

● ADP + Pi → ATP (+ water)
● Condensation reaction, removing a water molecule
● Catalysed by ATP synthase (enzyme)
● During respiration and photosynthesis

Question 8

Suggest how the properties of ATP make it a suitable immediate source of energy for cells

Answer 8

• Releases energy in (relatively) small, manageable amounts / little energy lost as heat
• broken down in a single reaction / one bond hydrolysed to release energy (so immediate release)
  -phosphorylation lowers the activation energy needed for biological molecules to react
• rapidly formed
  -solution - most biological reactions take place in solution; cytoplasm
  -Cannot pass out of cell

Question 9

where does the energy come from?

Answer 9

1.light - results in photophosphorylation
2.respiration - oxidation phosphorylation
3. doner molecule - substrate level phosphorylation

Question 10

what are the disadvantages of ATP?

Answer 10

• ATP cannot be moved from cell to cell/ stored because it is so reactive

Question 11

true or false “ATP has 3 phosphorus groups.”

Answer 11

false
ATP has 3 phosphate groups

Question 12

true or false “ATP hydrolysis creates energy.”

Answer 12

false
Energy cannot be created - only transferred / released.

Question 13

true or false “ATP can be stored.”

Answer 13

false
ATP is too unstable to be stored within cells.

Question 14

true or false “The only use of ATP is energy release.”

Answer 14

false
The inorganic phosphate can be used to phosphorylate other
compounds, making them more reactive.

Question 15

what are the differences between the nucleotide in ATP (nucleotide derivative) and the nucleotides in DNA

Answer 15

1. ATP has 3 phosphates DNA 1 phosphate group per nucleotide
2. ATP has ribose, DNA deoxyribose
3. ATP - base always adenine, DNA it varies

Question 16

Why is glucose not a good immediate energy source for a cell?

Answer 16

-Stable so energy is released slowly.
-Large amount of energy released - difficult to manage.
-Many reactions required to release energy.

Question 17

compare ATP and carbs

Answer 17

Question 18

Explain how hydrogen bonds occur between water molecules

Answer 18

● Water is polar molecule (electrons have uneven distribution)
● Slightly negatively charged oxygen atoms attract slightly positively
charged hydrogen atoms of other water molecules
- 2 hydrogen atoms covalently bonded to 1 oxygen atom

Question 19

describe the H bonds in water molecules

Answer 19

• form between polar molecules containing hydrogen
• they do not result in a permanent structure, bonds break and reform as water molecules move around

Question 20

how is the water property metabolite important?

Answer 20

Used in condensation / hydrolysis / photosynthesis / respiration

Question 21

how is water property Solvent (can
dissolve solutes) important?

Answer 21

1. Allows metabolic reactions to occur (faster in solution)
2. Allows transport of substances eg. nitrates in xylem, urea in blood

Question 22

how is the water property (Relatively) high
specific heat
capacity important?

Answer 22

● Buffers changes in temperature
● As can gain / lose a lot of heat / energy without changing temperature
1. Good habitat for aquatic organisms as temperature more stable than land
2. Helps organisms maintain a constant internal body temperature

Question 23

how is the water property (Relatively) large
latent heat of
vaporisation important?

Answer 23

● Allows effective cooling via evaporation of a small volume (eg. sweat)
● So helps organisms maintain a constant internal body temperature

Question 24

how is the water property Strong cohesion
between water
molecules important?

Answer 24

1. Supports columns of water in tube-like transport cells of plants
   eg. transpiration stream through xylem in plants
2. Produces surface tension where water meets air, supporting small
   organisms (to walk on water)

Question 25

name some properties of water

Answer 25

polar, solvent, reactive

Question 26

Why is it useful to living organisms that water is polar?

Answer 26

can act as a universal solvent (chemical reaction happens faster in solutions)

Question 27

why is it useful to living cells that water is reactive?

Answer 27

takes place in hydrolysis and condensation reactions

Question 28

true or false “Water is cohesive which aids transpiration.”

Answer 28

Transpiration is the loss of water vapour from leaves. The transpiration stream is the constant movement of water through the plant. Cohesion aids the transpiration stream.

Question 29

Where are inorganic ions found in the body?

Answer 29

In solution in cytoplasm and body fluid, some in high concentrations and others in very low concentrations

Question 30

Describe the role of hydrogen ions

Answer 30

● Maintain pH levels in the body → high concentration = acidic / low pH
● Affects enzyme rate of reaction as can cause enzymes to denature

Question 31

describe the role of iron ions

Answer 31

● Component of haem group of haemoglobin
● Allowing oxygen to bind / associate for transport as oxyhaemoglobin

Question 32

describe the role of sodium ions

Answer 32

1. Involved in co-transport of glucose / amino acids into cells
2. Because sodium moved out by active transport
3. Creates a sodium concentration/diffusion gradient;
4. Affects osmosis/water potential;
5. Involved in action potentials in neurons

Question 33

describe the role of phosphate ions

Answer 33

1. Component of nucleotides, allowing phosphodiester bonds to form in DNA / RNA
2. Component of ATP, allowing energy release
3. Phosphorylates other compounds making them more reactive
4. Hydrophilic part of phospholipids, allowing a bilayer to form

Question 34

how do water and ions enter cells?

Answer 34

they can move down a concentration gradient
both move through channel proteins
ions can move against a concentration gradient by active transport