Carbohydrates & Sugars Flashcards
what are carbs made of?
carbon, hydrogen + oxygen = HC
uses of carbs
- energy store in all organisms (starch/glycogen)
- structural material in cell walls/membranes (cellulose+glycoproteins)
- animal skeletons (mainly chitin)
general formula for carbs?
(CH2O)n
define monosaccharides
single sugar units -> 1 monomer unit only
building blocks for larger carbs
vary according to no. of carbon atoms + way atoms are arranged in the molecules
define polysaccharides
polymers with many monomer chains (1000s) bonded by glycosidic bonds
formed by condensation reactions
what’s a glycosidic bond?
type of covalent bond that joins a carb (sugar) molecule to another group which may or may not be another carb
monosaccharides examples
glucose fructose ribose deoxyribose galactose
polysaccharaides examples
starch (plants) -> energy store cellulose (plants) -> structure glycogen (animals) -> energy store amylose amylopectin *CHECK NOTES FOR TABLE*
general formula of carbs?
(CH2O)n
common monosaccharides
CHECK MINI TABLE IN NOTES
what direction/order are the carbon atoms labelled?
clockwise
define qualitative estimation + give an example
use of non-quantifiable/quantitative methods
e.g. benedict’s test
benedict’s test -> stays blue
no simple sugar
or a simple sugar but a non-reducing sugar
benedict’s test -> green
low conc. of reducing sugar
benedict’s test -> yellow/orange
medium conc. of reducing sugar
benedict’s test -> red
high conc. of reducing sugar
what does a non-reducing sugar need to do to test +ve by benedict’s reagent?
be boiled with HCl
monosaccharide properties
- monomers cant be broken down into simple sugars
- suagars -> all taste sweet
- soluble in water
- show isomerism -> exist in more than 1 form
whats a carbohydrate?
group of substances used as both energy sources + structural materials in organisms
general formula for polysaccharides/many carbs?
(CxH2O)y
3 main carb groups?
monosaccharides -> simple sugars
disaccharides -> double sugars (2 monos…)
polysaccharides -> large molecules (many monos…)
describe glucose
abundant + important monos... hexose sugar -> 6 carbon atoms major energy source for most cells very soluble main form in which carbs are transported in animals *CHECK NOTES FOR DIAGRAMS*
describe glucose’s structure
forms 6 membered ring when OH group on carbon 5 adds to aldehyde group on carbon 1
how to tell the difference between alpha + beta hexose sugars
isomers on the far right
alpha -> H + OH
beta -> OH + H
has major effect on their biological roles
examples of hexose sugars
glucose
galactose
examples of pentose sugars
fructose
ribose
describe fructose
pentose
very soluble
main sugar in fruits/nectar
sweeter than glucose
describe galactose
hexose
less soluble than glucose
important role in production of glycolipids + glycoproteins
describe the structure of a pentose sugar
5 carbon atoms
long enough to form a ring
general formula for disaccharides
Cn (H2O) n-2
examples of common disaccharides?
sucrose
lactose
maltose
isomaltose
how are polymers formed?
monomers join together by condensation to form a polymer
describe the process of how polymers are made by condensation and hydrolysis
water molecule removed by condensation
hydrolysis broken down with addition of water molecule
how is maltose formed?
2 glucose molecules undergo condensation + join by an alpha 1-4 glycosidic bond
how is sucrose formed?
glucose + fructose join by alpha 1-4 glycosidic bond
how is lactose formed?
galactose + glucose join by beta 1-4 glycosidic bond
define reducing sugar
any carb that can be oxidised + cause reduction of other substances w/o being hydrolysed first
define non-reducing sugar
any carb that can’t be oxidised or reduce substances w/o being hydrolysed first
generally, why can all free monos… be oxidised?
they have a free aldeyde or hydroxylketonic group
after oxidation they can reduce substances -> they’re reducing sugars
what do fehling and benedict’s solution carry out?
oxidation
explain reducing sugars in terms of groups + ions
- have free CHO (aldehyde) + (CO) ketonic group
- able to reduce curpic (copper 2+) ions of benedict’s sol. to cuprous (copper 1+) ions
what’s an aldehyde group?
CHO
what’s a ketonic group
CO
explain non-reducing sugars in terms of groups + ions
- DONT have free CHO (aldehyde) or (CO) ketonic group
- CANT reduce curpic (copper 2+) ions of benedict’s sol. to cuprous (copper 1+) ions
main uses of polysac…?
- energy store
- structural components of cells
major polysac…?
starch
cellulose
glycogen
describe starch
mixture of 2 polysaccharides of a-glucose - amylose -> 20-30%, 1-4 g.b. - amylopectin -> 70-80%, 1-4 + 1-6 g.b. branched H-bonds form interior of helix
how is starch a better alternative to glucose?
compact + insoluble alternative to storing 1000’s of glucose molecules for energy storage
in plants
where is starch found?
in small grains in many parts of a plant in plastids
large amounts in seeds + storage organs
describe the structure of starch
a-glucose monosaccharides chains linked by glycosidic bonds from condesnation react. branched chain wounds into tight coil/spiral to make molecule compact
held together by H-bonds
describe role of starch for energy storage
insoluble -> wont affect osmotic balance or diffuse out
compact -> can be stored in small places
forms a-glucose when quickly hydrolysed -> readily y=used for respiration if needed
what type of suspensions do polysac… form unlike momosac…?
colloidal suspensions
describe amylose structure
formed by a series of condensation react. that bond a-glucose molecules together into long chain
many glycosidic bonds formed
coils into helix
describe amylopectin structure
straight chain of a-glucose units
branch points approx. at every 12th glucose unit
branch points form when carbon 6 of glucose molecule in chain forms glycosidic bond with a carbon 1 from a glucose molecule above
what’s a plastid
membrane-bound organelle found in plant cells
how is starch produced?
from glucose made during photosynthesis
broken down during resp.
source of carbon
what’s glycogen?
carbs stored as glycogen in small granules in muscles + liver
in animals
describe glycogen’s structure
1-6 glycosidic bonds -> branched structure
how is glycogen different to starch?
less dense + more soluble than starch
breaks down faster -> animals need higher metabolic rate than plants
shorter chains than starch -> more readily hydrolysed to a-glucose
describe structure of cellulose
beta glucose
straight unbranched chains -> parallel to eachother
OH groups protrude outwards
H-bonds form across adjacent strands between cellulose molecules
lattic struc. -> rigid -> good for cell walls + SA for photosyn.
many H-bonds make it strong
how are b- and a- glucose diff. in terms of structure?
alpha -> H group on top, OH group on bottom
beta -> OH group on top, H group on bottom
how do you link 2 b-glucose molecules together?
one must rotate 180 degrees
why is cellulose strong?
many H-bonds
makes plant rigid
what do cellulose molecules group together to form?
microfibrils
arranged in parallel groups called fibres
why are humans considered heterotrophs?
we digest + absorb carbs formed from energy from sun
all energy comes from sun
REVISE FOOD TEST STEPS
IN NOTES
general formula of monosaccharides?
Cn H2n On
e.g. of triose
pyruvate
e.g of pentose
ribose
deoxyribose
e.g. of heroes
glucose
define disaccharide
2 monosaccharides joined together by glycosidic bonds
