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A-LEVEL BIOLOGY > Carbohydrates & Sugars > Flashcards

Carbohydrates & Sugars Flashcards

(71 cards)

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1
Q

what are carbs made of?

A

carbon, hydrogen + oxygen = HC

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2
Q

uses of carbs

A
  • energy store in all organisms (starch/glycogen)
  • structural material in cell walls/membranes (cellulose+glycoproteins)
  • animal skeletons (mainly chitin)
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3
Q

general formula for carbs?

A

(CH2O)n

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4
Q

define monosaccharides

A

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

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5
Q

define polysaccharides

A

polymers with many monomer chains (1000s) bonded by glycosidic bonds
formed by condensation reactions

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6
Q

what’s a glycosidic bond?

A

type of covalent bond that joins a carb (sugar) molecule to another group which may or may not be another carb

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7
Q

monosaccharides examples

A 
glucose
fructose
ribose
deoxyribose
galactose
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8
Q

polysaccharaides examples

A 
starch (plants) -> energy store
cellulose (plants) -> structure
glycogen (animals) -> energy store
amylose
amylopectin
*CHECK NOTES FOR TABLE*
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9
Q

general formula of carbs?

A

(CH2O)n

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10
Q

common monosaccharides

A

CHECK MINI TABLE IN NOTES

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11
Q

what direction/order are the carbon atoms labelled?

A

clockwise

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12
Q

define qualitative estimation + give an example

A

use of non-quantifiable/quantitative methods

e.g. benedict’s test

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13
Q

benedict’s test -> stays blue

A

no simple sugar

or a simple sugar but a non-reducing sugar

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14
Q

benedict’s test -> green

A

low conc. of reducing sugar

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15
Q

benedict’s test -> yellow/orange

A

medium conc. of reducing sugar

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16
Q

benedict’s test -> red

A

high conc. of reducing sugar

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17
Q

what does a non-reducing sugar need to do to test +ve by benedict’s reagent?

A

be boiled with HCl

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18
Q

monosaccharide properties

A
  • monomers cant be broken down into simple sugars
  • suagars -> all taste sweet
  • soluble in water
  • show isomerism -> exist in more than 1 form
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19
Q

whats a carbohydrate?

A

group of substances used as both energy sources + structural materials in organisms

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20
Q

general formula for polysaccharides/many carbs?

A

(CxH2O)y

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21
Q

3 main carb groups?

A

monosaccharides -> simple sugars
disaccharides -> double sugars (2 monos…)
polysaccharides -> large molecules (many monos…)

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22
Q

describe glucose

A 
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*
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23
Q

describe glucose’s structure

A

forms 6 membered ring when OH group on carbon 5 adds to aldehyde group on carbon 1

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24
Q

how to tell the difference between alpha + beta hexose sugars

A

isomers on the far right
alpha -> H + OH
beta -> OH + H
has major effect on their biological roles

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25
examples of hexose sugars
glucose | galactose
26
examples of pentose sugars
fructose | ribose
27
describe fructose
pentose very soluble main sugar in fruits/nectar sweeter than glucose
28
describe galactose
hexose less soluble than glucose important role in production of glycolipids + glycoproteins
29
describe the structure of a pentose sugar
5 carbon atoms | long enough to form a ring
30
general formula for disaccharides
Cn (H2O) n-2
31
examples of common disaccharides?
sucrose lactose maltose isomaltose
32
how are polymers formed?
monomers join together by condensation to form a polymer
33
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
34
how is maltose formed?
2 glucose molecules undergo condensation + join by an alpha 1-4 glycosidic bond
35
how is sucrose formed?
glucose + fructose join by alpha 1-4 glycosidic bond
36
how is lactose formed?
galactose + glucose join by beta 1-4 glycosidic bond
37
define reducing sugar
any carb that can be oxidised + cause reduction of other substances w/o being hydrolysed first
38
define non-reducing sugar
any carb that can't be oxidised or reduce substances w/o being hydrolysed first
39
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
40
what do fehling and benedict's solution carry out?
oxidation
41
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
42
what's an aldehyde group?
CHO
43
what's a ketonic group
CO
44
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
45
main uses of polysac...?
- energy store | - structural components of cells
46
major polysac...?
starch cellulose glycogen
47
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 ```
48
how is starch a better alternative to glucose?
compact + insoluble alternative to storing 1000's of glucose molecules for energy storage in plants
49
where is starch found?
in small grains in many parts of a plant in plastids | large amounts in seeds + storage organs
50
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
51
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
52
what type of suspensions do polysac... form unlike momosac...?
colloidal suspensions
53
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
54
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
55
what's a plastid
membrane-bound organelle found in plant cells
56
how is starch produced?
from glucose made during photosynthesis broken down during resp. source of carbon
57
what's glycogen?
carbs stored as glycogen in small granules in muscles + liver in animals
58
describe glycogen's structure
1-6 glycosidic bonds -> branched structure
59
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
60
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
61
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
62
how do you link 2 b-glucose molecules together?
one must rotate 180 degrees
63
why is cellulose strong?
many H-bonds | makes plant rigid
64
what do cellulose molecules group together to form?
microfibrils | arranged in parallel groups called fibres
65
why are humans considered heterotrophs?
we digest + absorb carbs formed from energy from sun | all energy comes from sun
66
REVISE FOOD TEST STEPS
IN NOTES
67
general formula of monosaccharides?
Cn H2n On
68
e.g. of triose
pyruvate
69
e.g of pentose
ribose | deoxyribose
70
e.g. of heroes
glucose
71
define disaccharide
2 monosaccharides joined together by glycosidic bonds

A-LEVEL BIOLOGY (8 decks)

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