Biochemistry - carbohydrates

Question 1

what are the three groups of carbs?

Answer 1

monosaccharides
disaccharides
polysaccharides

Question 2

what are monosaccharides?

Answer 2

monomers that join together to make larger carbohydrates
e.g. glucose, galactose, fructose

Question 3

what is a disaccharide?

Answer 3

two monosaccharides joined together by a condensation reaction
e.g. maltose, sucrose, lactose

Question 4

what is a polysaccharide?

Answer 4

many monosaccharides joined together by condensation reactions
e.g. cellulose, starch, chitin, glycogen

Question 5

how do you make maltose?

Answer 5

glucose + glucose

Question 6

how do you make sucrose?

Answer 6

glucose + fructose

Question 7

how do you make lactose?

Answer 7

glucose + galactose

Question 8

what bond forms between two monosaccharides?

Answer 8

glycosidic bond

Question 9

what are the isomers of glucose

Answer 9

alpha glucose and beta glucose

Question 10

what is an isomer?

Answer 10

a molecule with the same molecular formula but differently arranged

Question 11

what is the difference between alpha-glucose and beta-glucose

Answer 11

the position of the hydroxyl group
ABBA

Question 12

structure and function of glycogen?

Answer 12

f: energy store in ANIMAL cells
s: alpha glucose
C1-C4 and C1-C6 glycosidic bonds
branched

Question 13

why is branching of glycogen good?

Answer 13

can be rapidly hydrolysed to release glucose for respiration providing energy

Question 14

structural advantages of glycogen?

Answer 14

large molecule so cannot leave cells
insoluble in water - water potential of cell not affected

Question 15

function and structure of starch ?
and what are the two types?

Answer 15

f: energy store in PLANT cells
s: alpha glucose
mixture of amylose (unbranched) and amylopectin (branched)

Question 16

structural advantages of starch ?

Answer 16

helical compact storage in cells
large molecules so cannot leave cell
insoluble in water doesn’t affect water potential of cell

Question 17

function and structure of cellulose ?

Answer 17

f: strength and structural support to PLANT cell walls
s: beta glucose (every other is rotated 180 deg)
long, straight unbranched chain

Question 18

structural advantages of cellulose ?

Answer 18

many H bonds link parallel strands (crosslinks ) to form micro fibrils (strong fibres)
h bonds are very strong in abundance

Question 19

what are reducing sugars?

Answer 19

all monosaccharides e.g. glucose and some disaccharides e.g. maltose/ lactose

Question 20

what are non-reducing sugars?

Answer 20

some disaccharides e.g sucrose

Question 21

whats the test for reducing sugars ?

Answer 21

benedict’s regent - heat
positive = green/yellow/orange/red precipitated (reducing sugar presence)

Question 22

how to test for non-reducing sugars?

Answer 22

hydrochloric acid -heat - neutralise with sodium bicarbonate - then add Benedict’s regent - heat
positive = green/yellow/orange/red precipitate

Question 23

test for starch?

Answer 23

iodine dissolved in potassium iodide - shake
positive = blue -black colour

Question 24

how to determine glucose concentration?

Answer 24

1) dilution series (known concentrations)
2) benedict’s test on each sample
3) using colorimeter measure absorbance of each sample and plot a calibration curve
4) repeat with unknown sample and use graph to determine glucose conc.

Question 25

function and structure of chitin ?

Answer 25

f: primary component of cell walls in fungi, exoskeletons of arthropods (crustaceans/insects)
s: long-chain polymer of an amide derivative of glucose (modified glucosamine)
unbranched

Question 26

what is the general formula of a monosaccharide ?

Answer 26

Cn(H2O)n)

Question 27

what are the functions of a monosaccharide ?

Answer 27

source of energy in respiration
building blocks of larger molecules
intermediates in reactions