1.1 chemical elements and biological compounds

Question 1

what are the four key inorganic ions?

Answer 1

magnesium, iron, phosphate, calcium.

Question 2

what is magnesium
needed for in plants? why?

Answer 2

it is essential for photosynthesis as it is a constituent of chlorophyll.

Question 3

what is iron a constituent of?

Answer 3

haemoglobin.

Question 4

what is phosphate used to make?

Answer 4

it is used to make nucleotides such as ATP, DNA, and RNA.

Question 5

what is phosphate a constituent of?

Answer 5

phospholipids found in biological membranes.

Question 6

what do phosphate and calcium do to bones (and teeth for calcium)?

Answer 6

harden them.

Question 7

why is calcium in plant cells?

Answer 7

it strengthens the cell wall.

Question 8

what is a polar molecule? an example?

Answer 8

a molecule that has no overall charge due to it having both a positively charged end and a negatively charged end. water molecules are polar (often called dipole).

Question 9

what kind of bonds form to make a molecule of water and where?

Answer 9

hydrogen bonds form between the + on a hydrogen atom of one molecule and the - on the oxygen atom of another molecule.

Question 10

what is an organic ion?

Answer 10

a molecule that has a high proportion of carbon and hydrogen atoms.

Question 11

what is an inorganic ion?

Answer 11

a molecule or ion that has no more than one carbon atom.

Question 12

what is a micronutrient? some examples?

Answer 12

minerals needed in minute concentrations, e.g copper and zinc.

Question 13

what is a macronutrient?

Answer 13

minerals needed in small concentrations.

Question 14

why is water a good solvent?

Answer 14

because of their polarity, water molecules are attracted to other water molecules and charged particles. this helps charged particles dissolve in water.

Question 15

why is water referred to as the universal solvent?

Answer 15

a large number of substances can easily dissolve in water.

Question 16

why is water a metabolite?

Answer 16

it is used in many biochemical reactions as a reactant.

Question 17

what does high specific heat capacity mean?

Answer 17

a large amount of heat energy is needed to raise its temperature.

Question 18

why does water have a high specific heat capacity?

Answer 18

hydrogen bonds between water molecules restrict their movement, resisting an increase in kinetic energy so the temperature does not increase.

Question 19

why is it beneficial that water has a high specific heat capacity?

Answer 19

it prevents large fluctuations in water temperature to keep aquatic habitats stable and to allow enzymes to work efficiently in cells.

Question 20

what does high latent heat of vaporisation mean?

Answer 20

a lot of heat energy is needed to change water from a liquid to a vapour.

Question 21

why is it beneficial that water has a high latent heat of vaporisation?

Answer 21

it is important in temperature control - heat is used to vaporise water from sweat on the skin/leaf’s surface. the surface cools as sweat evaporates.

Question 22

how is water cohesive?

Answer 22

water molecules attract eachother, forming hydrogen bonds. the large amount of hydrogen bonds stick the molecules together to form a lattice.

Question 23

what is a benefit of water being cohesive?

Answer 23

it allows volumes of water to be drawn up xylem vessels.

Question 24

how and why does water have a high surface tension?

Answer 24

cohesion between water molecules at the surface of a body of water produce tension to support the bodies of insects.

Question 25

why does water have a high density?

Answer 25

it provides support and buoyancy as a habitat for aquatic organisms.

Question 26

at what temperature is water’s maximum density?

Answer 26

4°C.

Question 27

why is ice less dense than water?

Answer 27

hydrogen bonds in ice hold the molecules further apart.

Question 28

why does water need to be transparent?

Answer 28

to allow light to pass through so plants can photosynthesise.

Question 29

what is the single monomer unit of a carbohydrate?

Answer 29

a monosaccharide.

Question 30

what is the name of 2 monosaccharides bonded together?

Answer 30

a disaccharide.

Question 31

what happens in a condensation reaction?

Answer 31

a molecule of water is removed from 2 monosaccharides and a glycosidic bond forms between them, creating a disaccharide.

Question 32

what is hydrolysis?

Answer 32

a molecule of water is added to a disaccharide to break the glycosidic bond and split it back into 2 monosaccharides.

Question 33

where is the hydroxyl group on an alpha glucose molecule?

Answer 33

on the bottom of carbon 1.

Question 34

where is the hydroxyl group on a beta glucose molecule?

Answer 34

on top of carbon 1.

Question 35

what is maltose made up of? what is it used for?

Answer 35

2 alpha glucose molecules. it is used in germinating seeds.

Question 36

what is sucrose made up of? what is it used for?

Answer 36

glucose + fructose. it is used in transport in phloem of flowering plants.

Question 37

what is lactose made up of? where is it found?

Answer 37

glucose + galactose. it is found in mammalian milk.

Question 38

how do you test for a reducing sugar?

Answer 38

equal volumes of solution and Benedict’s reagent are heated to 70°C. if a reducing sugar is present, it will change from blue to brick-red.

Question 39

how do you detect a non-reducing sugar?

Answer 39

the solution must be heated with HCl to break it into its monosaccharides. then Benedict’s reagent and an alkali are added, and the solution will turn brick-red if a non reducing sugar is present.

Question 40

what are 3 features of polysaccharides that make them most suitable for storage?

Answer 40

they are insoluble - osmotically inert, they are compact molecules, and carry a lot of energy in their C-H and C-C bonds.

Question 41

what is starch made up of?

Answer 41

it is made up of a-glucose molecules and contains the 2 polymers amylose and amylopectin.