Biological molecules (monomers,polymers,carbs)

Question 1

Define monomers (name examples)

Answer 1

smaller units that join together to for larger molecules
.monosaccharides
.amino acids
.nucleotides

Question 2

Define polymer name examples

Answer 2

molecules formed when many monomers join together
.polysaccharides
.proteins
.DNA/RNA

Question 3

What happens in a condensation reaction?

Answer 3

A chemical bond forms between 2 molecules and a molecule of water is produced

Question 4

What happens in a hydrolysis reaction?

Answer 4

A water molecule is used to break a chemical bond between 2 molecules

Question 5

Name 3 monosaccharides

Answer 5

.glucose
.fructose
.galactose
molecular formular C6H12O6

Question 6

Name the type of bond formed when monosacharides react

Answer 6

(1,4 or 1,6) glycosidic bond
2 monomers=1 chemical bond=disaccharide
multiple monomers=many chemical bonds=polysaccharide

Question 7

Name 3 disaccharides. Describe how they form.

Answer 7

condensation reaction forms glycosidic bond between 2 monosacchardies

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

molecular formula=C12H22O11

Question 8

Describe the structure and functions of starch

Answer 8

.storage polymer of alpha gluose in plant cells
.insoluble=no osmotic effect on cells
.large=doesn’t diffuse out of cells
MADE FROM AMYLOSE:
.1,4 glycosidic bonds
.helix with intermolecular H-bonds=compact
MADE FROM AMYLOPECTIN:
.1,4 and 1,6 glycosidic bonds
.branched=many terminal ends for hydrolysis into glucose

Question 9

Describe the structure and functions of glycogen

Answer 9

main storage polymer of alpha glucose in animal cells (also found in plant)
.1,4 and 1,6 glycosidic bonds
.branched=many terminal ends for hydrolysis
.insoluble=no osmotic effect and doesn’t diffuse out of cells
.compact

Question 10

Describe the structure and fucntions of cellulose

Answer 10

polymer of beta glucose gives rigidity to plant cells (prevents bursting under turgor pressure.holds stem up)
.1,4 glycosidic bonds
. straight-chain, unbranched molecule
.alternate glucose molecules are rotated 180°
.H-bond crosslinks between parallel strands form microfibrils = high tensile strength

Question 11

Describe the Benedict’s test for reducing sugars

Answer 11

1-Add an equal volume of Benedict’s reagent to a sample
2-Heat the mixture in an electric water bath at 100 degrees for 5 minutes
3-Positive=colour change from blue to orange and brick red precipitate

Question 12

Describe the Benedict’s test for non-reducing sugars

Answer 12

1- Negative result: Benedict’s reagent remains blue
2-Hydrolyse non-reducing sugars e.g. sucrose into their monomers by adding 1cm³ of HCI. Heat in a boiling water bath for 5 mins.
3-Neutralise the mixture using sodium carbonate solution.
4-Proceed with the Benedict’s test as usual.

Question 13

Describe the test for starch

Answer 13

1-Add iodine solution
2-Positive result=colour change from orange to blue-black

Question 14

Outline how colorimetry could be used to give qualitative results for the presence of sugars and starch.

Answer 14

1-Make standard solutions with known concentrations.
Record absorbance or % transmission values.
2- Plot calibration curve: absorbance or % transmission (y-axis), concentration (x-axis).
3- Record absorbance or % transmission values of unknown samples. Use calibration curve to read off concentration