carbohydrates

Question 1

define monomer and polymer. Give some examples

Answer 1

• monomer - smaller units that join together to form larger molecules - monosaccharides, amino acids, nucleotides
• polymer - molecules formed when many monomers join together - polysaccharides, proteins, DNA/RNA

Question 2

name the elements found in carbohydrates, lipids, proteins and nucleic acids

Answer 2

carbohydrates and lipids - CHO
proteins - CHONS
nucleic acids - CHONP

Question 2

why happens in a condensation and hydrolysis reaction

Answer 2

condensation: chemical bond forms between 2 molecules and a molecule of water is produced
hydrolysis - a water molecule is used to break a chemical bond between 2 molecules

Question 3

describe the properties of alpha glucose

Answer 3

small and water soluble - easily transported in bloodstream
complementary shape to antiport for co-transport for absorption in gut
complementary shape to enzymes for glycolysis - respiratory substrate

Question 4

what type of bond forms when monosaccharides react

Answer 4

1,4 or 1,6 glycosidic bond
2 monomer = 1 chemical bond = disaccharide
multiple monomers = many chemical bonds = polysaccharides

Question 5

name three disaccharides. describe how they form

Answer 5

maltose = a glucose + a glucose
lactose = b glucose + galactose
sucrose = fructose + a glucose

Question 6

describe the structure and function of starch

Answer 6

storage polymer of alpha glucose in plant cells
insoluble = no osmotic effect on cells
large = does not diffuse out of cells

Question 7

what are the two types of starch

Answer 7

amylose
amylopectin

Question 8

describe the structure and function of glycogen

Answer 8

main storage polymer of alpha glucose in animal cells
1,4 and 1,6 alpha glycosidic bonds
branched = many terminal ends for hydrolysis
insoluble = no osmotic effect and does not diffuse out of cells
compact

Question 9

describe the structure and function of cellulose

Answer 9

polymer of beta glucose
gives rigidity to plant cell walls (prevents bursting under turgor pressure, holds stem up)
1,4 beta glycosidic bond
straight chain, unbranched molecule
alternate glucose molecules are rotated 180 degrees
H bonds crosslinks between parallel strands form microfibrils = high tensile strength
- cannot be stretched, stops the cell bursting

Question 10

what is the difference between reducing and non-reducing sugars

Answer 10

reducing sugars can donate their electrons - the sugars become the reducing agent, thus reducing sugars can be detected using Benedict’s test as they reduce the soluble copper sulphate to insoluble brick-red copper oxide
non-reducing sugars cannot donate their electrons therefore they cannot be oxidised. it has to be hydrolysed first to break the disaccharides into its two monosaccharides before a Benedict’s test can be carried out.

Question 11

what are some examples of reducing and non-reducing sugars

Answer 11

reducing - galactose, glucose and fructose
non-reducing - sucrose

Question 12

what are 2 functions of glucose

Answer 12

as an energy source - it is the main substance used in respiration, releasing energy for the production of ATP
soluble and so can be transported in water

Question 13

what are the 2 different forms of glucose

Answer 13

alpha (α) glucose and beta (β) glucose

Question 14

what is an isomer

Answer 14

organic molecules with the same molecular formula but different structure which results in different properties
e.g. alpha (α) glucose and beta (β) glucose

Question 15

what is the difference between ribose and deoxyribose

Answer 15

deoxyribose has lost one oxygen atom at carbon number 2

Question 16

what are the advantages of have monosaccharides bonded together

Answer 16

more suitable for transport
storage - more compact
cell osmolarity - polysaccharides and disaccharides have less -OH groups

Question 17

what are 3 common disaccharides

Answer 17

maltose: the sugar formed in the production and breakdown of starch
sucrose: the main sugar produced in plants
lactose: a sugar found in milk

Question 18

what are 3 examples of polysaccharides

Answer 18

starch
glycogen
cellulose

Question 19

amylose
1. name of bond
2. name of monosaccharide
3. shape + why

Answer 19

1,4 alpha glycosidic bond
alpha glucose
helix shape (twisted) caused by the hydrogen bonds between the -OH groups of the molecules

Question 20

amylopectin
1. name of monosaccharides
2. name of bond
3. structure

Answer 20

alpha glucose
1,4 alpha glycosidic and 1,6 alpha glycosidic bonds
branched (1,6 bonds create a branch)
branches can store lots of glucose molecules for when the body needs it
many terminals/ends of glucose units allows the rapid release / hydrolysis of glucose
make molecules compact so it can be stored in a small space

Question 21

what are the similarities of glycogen and amylopectin and what are the differences

Answer 21

glycogen has a similar structure to amylopectin but has more branches
glycogen is the animal storage molecule of alpha glucose and as animals, we have a higher metabolic rates and respire more and have a higher glucose requirement

Question 22

what are the 4 properties of a good storage molecule and what are the disadvantages

Answer 22

compact - not much volume by being coiled or branched
insoluble if they were soluble they would be able to dissolve in water instead of staying in the cell. due to condensation reaction, polysaccharides have less -OH groups
no osmotic effect - when polymerisation occurs, the glucose no longer attracts/pulls water into the cell due to less -OH groups
easy to hydrolyse/polymerise - lots of -OH groups that form H bonds

Question 23

amylopectin and glycogen have very similar structures and functions.
list the structural features shared by both amylopectin and glycogen and explain how they relate to their function

Answer 23

1,6 alpha glycosidic bond - branches - rapid release or digestion of glucose
lots of alpha 1,4 and 1,6 bonds - easy to polymerise / hydrolyse
insoluble + no osmotic effect - efficient
polysaccharides of alpha glucose - storage of alpha glucose