3.1 Biological molecules - water, ATP, ions

Question 1

what does ATP stand for?

Answer 1

adenosine triphosphate

Question 2

what is the structure of ATP?

Answer 2

a molecule of adenine bonded to a molecule of ribose, a chain of 3 phosphate groups also bonded to the ribose

Question 3

How does ATP store energy?

Answer 3

It is a nucleotide and has 3 phosphate groups
The bonds between these groups are unstable and have a low activation energy, so they are easily broken

Question 4

what is ADP?

Answer 4

adenosine diphosphate - 2 phosphate groups

Question 5

how does the hydrolysis of ATP form?

Answer 5

ADP and an inorganic phosphate group (Pi)

Question 6

what enzyme catalyses the hydrolysis?

Answer 6

ATP hydrolase (ATPase)

Question 7

What happens when the bonds between the phosphate groups in an ATP break?

Answer 7

They release a considerable amount of energy

Question 8

What kind of reaction is the conversion of ATP to ADP and hence, what does this mean?

Answer 8

Reversible so energy can be used to add an inorganic phosphate to ADP to re-form ATP (synthesis of ATP)

Question 9

What is the synthesis of ATP catalysed by?

Answer 9

The enzyme ATP synthase

Question 10

what is the role of ATP?

Answer 10

it is the immediate energy source of a cell (not long term due to instability of phosphate bonds)

Question 11

describe the polarity of water

Answer 11

the shared negative hydrogen electrons are pulled towards the oxygen atom leaving the other end of the hydrogen atom with a slight positive charge, the unshared negative electrons on the oxygen atom gives it a slight negative charge making water a polar molecule

Question 12

what kind of bonding occurs in water?

Answer 12

hydrogen bonds - they are weak bonds between a slightly positively charged hydrogen atom in one molecule and a slightly negatively charged atom in another molecule

Question 13

water is an important metabolite what does that mean?

Answer 13

many metabolic reactions involve a condensation (releases water) or a hydrolysis reaction (requires water)

Question 14

water is a good solvent. why and why is it useful?

Answer 14

waters polarity makes it a useful solvent making it possible for living organisms to take up useful substances dissolved in water which can then be transported around the body of the organism

Question 15

water has a high latent heat of vaporisation. what does that mean?

Answer 15

water vaporises (evaporates) when the hydrogen bonds between the molecules break. this uses up a lot of energy (heat) - lots of heat is used to change it from a liquid to gas

Question 16

how is water having a high latent heat of vaporisation useful for living organisms?

Answer 16

Organisms can cool down by losing water through evaporation. When water evaporates from a surface, it takes heat energy with it. This removes heat from the surface, which helps to lower its temperature. Because water has a high latent heat of vaporisation, only a small amount of water needs to be lost to remove a lot of heat — so organisms can cool down without losing too much water

Question 17

water can buffer (resist) changes in temperature. what does this mean?

Answer 17

Hydrogen bonds between water molecules give water a high specific heat capacity. This means water can absorb a lot of energy before its temperature increases. As a result, water does not experience rapid temperature changes

Question 18

what is specific heat capacity?

Answer 18

the amount of energy needed to raise the temperature of a substance

Question 19

why is water being able to buffer changes in temperature useful for living organisms?

Answer 19

This is useful for living organisms because it helps to maintain a stable environment (e.g., inside cells), which is important for enzyme function and other biological processes

Question 20

water is very cohesive what does this mean?

Answer 20

cohesion- attraction between molecules of the same type
Water molecules are polar and can form hydrogen bonds with each other.
These hydrogen bonds hold the water molecules together, making them strongly attracted to one another

Question 21

why is strong cohesion in water useful?

Answer 21

helps water flow making it great for transporting substances
means water has high surface tension when it comes into contact with air - this is why sweat forms droplets which evaporate from skin to cool down an organism and why some insects are able to walk on the surface of water

Question 22

what is an ion?

Answer 22

atom with an electric charge

Question 23

what is a cation?

Answer 23

a positive ion

Question 24

what is an anion?

Answer 24

a negative ion

Question 25

what does inorganic mean?

Answer 25

no carbon

Question 26

where are inorganic ions found?

Answer 26

they occur in solution in the cytoplasm and body fluids of organisms

Question 27

where are iron ions (Fe2+) found?

Answer 27

haemoglobin

Question 28

what is the role of iron ion in haemoglobin?

Answer 28

haemoglobin is a large protein that carries oxygen around the body in red blood cells its made up of 4 polypeptide chains with an iron ion at the centre of each one. the iron ion binds to oxygen to temporarily create Fe3+ until the oxygen is released

Question 29

how is pH calculated in an environment?

Answer 29

based on the concentration of H+ (Hydrogen ions) present

Question 30

what is the relationship between concentration of H+ ions and pH?

Answer 30

the higher the concentration of H+ ions present the lower the pH

Question 31

what ions help glucose and amino acids to cross cell membranes via co-transport?

Answer 31

sodium ions (Na+) - a molecule of glucose or an amino acid can be transported into a cell alongside sodium ions

Question 32

when a phosphate ion (PO4 3-) is attached to another molecule what is it known as?

Answer 32

a phosphate group

Question 33

what is the role of phosphate ions in ATP?

Answer 33

the bonds between the phosphate groups store energy

Question 34

what is the role of phosphate ions in DNA and RNA?

Answer 34

the phosphate groups allow nucleotides to bond to form polynucleotides