Biological Molecules - Water, ATP + Ions

Question 1

What does ATP stand for?

Answer 1

Adenosine Triphosphate

Question 2

What type of molecule is ATP?

Answer 2

a phosphorylated macromolecule

Question 3

What are the 3 parts of ATP?

Answer 3

Adenine

Ribose

Chain of 3 phosphates

Question 4

Why is ATP the immediate energy source?

Answer 4

because a cell is incapable of releasing energy directly from glucose

Question 5

Give an example of endosymbiotic theory

Answer 5

Mitochondria are unicellular organisms that live inside of eukaryotic cells -> they even have their own DNA and a plasma membrane separate from the cell

Question 6

Which organelles can produce ATP?

Answer 6

Mitochondria and Chloroplasts

Question 7

What happens to ATP once produced by mitochondria?

Answer 7

it diffuses out to the rest of the cell to power other cellular processes

Question 8

Where is the available energy in ATP stored?

Answer 8

In the bonds between the phosphate groups

these bonds are unstable and so have low activation energy

when they break they release a substantial amount of energy

Question 9

How many phosphates are removed during the breakdown of ATP?

Answer 9

1

Question 10

What is the symbol equation for the breakdown of ATP?

Answer 10

ATP + H₂0 -> ADP + P_i + E

Question 11

What is the word equation for the breakdown of ATP?

Answer 11

Adenoside Triphosphate + Water -> Adenoside Diphosphate + inorganic phosphate + energy

Question 12

What type of reaction is the breakdown of ATP?

Answer 12

As a water molecule is used, it is a hydrolysis reaction

Question 13

What enzyme catalyses the breakdown of ATP?

Answer 13

Hydrolase

Question 14

How can the hydrolysis of ATP be ‘coupled’ with another reaction?

Answer 14

It can be coupled with an endothermic reaction, as the hydrolysis is exothermic

Instead of the energy being lost as heat, it is instead used to power the coupled reaction

The released phosphate molecule can also be used to phosphorylate another molecule in order to make it more reactive

Question 15

What is the % of water in a cell’s mass?

Answer 15

70%

Question 16

What are the 4 main properties of water?

Answer 16

Dipolar due to bent shape

Strong surface tension and cohesive

High specific heat capacity

Good solvent

Question 17

What is a use of the high specific heat capacity of water?

Answer 17

It acts as a buffer against rapid temperature changes, making aqueous environments relatively stable

Question 18

Why is water a good solvent?

Answer 18

The dipolarity means that ionic compounds can dissolve as the positive ions are attracted to the O^- and the negative ions are attracted to the H⁺

Question 19

Explain why water has surface tension and is cohesive

Answer 19

Due to the dipolarity, water molecules have strong intermolecular bonds as O^- attracts H⁺

This causes the molecules to stick together

The hydrogen bonds allows water to be drawn up through tubes, forming a miniscus

Question 20

Describe the function of iron ions in haemoglobin

Answer 20

each of the 4 polypeptide chains making up haemoglobin has an Fe²⁺ ion in the centre

this is the part of haemoglobin that bonds to oxygen

whilst oxygen is bonded to the ion, it temporarily becomes Fe³⁺

Question 21

Describe a use of hydrogen ions

Answer 21

H⁺ ions are sometimes concentrated to facilitate certain enzyme reactions eg there are more hydrogen ions in the stomach

Question 22

Describe a use of sodium ions

Answer 22

sodium ions can travel relatively easily through, taking larger molecules such as glucose or amino acids with them that need to be transported too

this is called co-transport

Question 23

What is the food test for non-reducing sugars?

Answer 23

Place a tube in boiling water and add HCl in a 1:1 ratio

Boil for 5 mins

Use sodium hydrocarbonate to neutralise the solution

test with benedict’s solution

Question 24

What is the food test for starch?

Answer 24

Add iodine

orange turns blue/black

Question 25

What is the test for proteins?

Answer 25

Biuret test:

crush solid food, add deionised water and decant the liquid

add equal amounts of sample liquid and NaOH solution

gently mix in a few drops of copper sulphate solution

positive result -> blue to purple