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carbohydrates Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

carbohydrates

A

contain C, H and O

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2
Q

how are H and O atoms present

A

ratio 2:1

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3
Q

3 types of carbohydrates

A

mono, di, polysacchardies

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4
Q

monosaccharide

A

single sugar molecule (all reducing suagrs)
e.g. glyceraldehyde (3C), ribose (5C), glucose (6C)
- source of energy in respiration
-building blocks for polymers)

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5
Q

disaccharide

A

sugar formed from 2 monosaccharides joined by a GB in a condensation reaction
e.g maltose (sugar found in germinating seeds) , sucrose (sugar stored in sugar cane) , lactose (mammal milk sugar)

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6
Q

polysaccharide

A

polymer formed by many monosaccharides joined by GB in a condensation reaction
e.g cellulose (structural cell wall) , starch (energy storage in plants), glycogen (energy storage in animals)
-insoluble in water

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7
Q

covalent bonds

A

very stable as high energies required to break bonds

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8
Q

condensation reaction

A

monomers combined by covalent bonds to form polymers (polymerisation) or macromolecules (lipids) and h2o removed
(also known as dehydration synthesis- ‘to put together while losing water’)

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9
Q

hydrolysis reaction

A

‘hyrdo’ = water
‘lyse’ = break
covalent bonds broken when water is added

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10
Q

covalent bonds of carbs

A

GB C-O-C

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11
Q

covalent bonds of proteins

A

peptide bonds O=C-N-H

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12
Q

covalent bonds of lipids

A

ester bonds O=C-O-C

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13
Q

covalent bonds of nucleic acids

A

phosphodiester bonds PO42- PO42- OH

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14
Q

reducing and non-reducing sugars

A

dependent on their ability to donate electrons

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15
Q

reducing sugars

A

can donate electrons (carbonyl group becomes oxidised), sugars become the reducing agent
TEST: benidicts test as they reduce the soluble copper II sulphate(blue) to insoluble brick-red copper oxide(precipitate)
1) add benidicts
2) heat in water bath
3) if present, coloured precipitate forms

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16
Q

examples of reducing sugars

A

glucose, fructose, galactose
-fructose and galactose have same molecular formula as glucose but dif. structural formula
-the dif. arrangement of atoms in the monosaccharide give them slightly dif. properties

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17
Q

non- reducing sugars

A

can’t donate electrons therefore can’t be oxidised
to be detected: must first be hydrolysed to break the dissacharide into its 2 monosaccharides ( will have an aldeyde or ketone functional group which can donate electrons to copped II sulfate- reducing it) before a Benidict’s test can be carried out
e.g. sucrose
1) add dilute HCL (hydrolyse any GB) + heat in water bath
2)neurtalise solution with sodium hydrogencarbonate
3) use red litmus paper to identify when it’s been neuralised (conditions need to be alkaline)
4) carry out test

18
Q

different types of monosaccharide formed from molecules with varying numbers of carbon atoms

A

trioses (3C) e.g. glyceraldehyde
pentoses (5C) e.g. ribose
hexoses (6C) e.g. glucose

19
Q

isomer

A

exists in 2 structually dif. forms
alpha and beta

20
Q

different polysaccharides are formed from the 2 isomers of glucose

A

starch= alpha
glycogen= alpha
cellulose= beta

21
Q

glycosidic bond (o2 link holding 2 molecules together)

A

formed by condensation (one h2o molecule removed)
strong covalent bond formed when 2 hydroxyl -OH groups (on dif. saccharides) interact to form: di + polysaccharides

22
Q

why are monosaccharides bonded together to form disaccharides and polysaccharides

A

to make monosaccharides more suitable for transport, storage and to have less influence on a cell’s osmolarity

23
Q

catalysing the glycosidic bond

A

each glycosidic bond is catalysed by enzymes specific to which OH groups are interacting

24
Q

types of glycosidic bonds table

A

maltose = alpha 1,4
sucrose = alpha 1,2
cellulose = beta 1,4
amylose = alpha 1,4
amylopectin = alpha 1,4 and 1,6

25
Q

breaking the glycosidic bond

A

broken when water is added in a hydrolysis reaction

26
Q

hydrolytic reactions

A

catalysed by enzymes, different to those present in condensation reactions

27
Q

what are broken down in hydrolysis reactions

A

disaccharides and polysaccharides

28
Q

Examples of hydrolytic reactions

A

digestion of food in the alimentary tract and the breakdown of stored carbohydrates in muscle and liver cells for use in cellular respiration

29
Q

what happens when sucrose is heated with HCL

A

this provides the water that hydrolyses the glycosidic bond resulting in two monosaccharides that will produce a positive Benedict’s test

30
Q

how do you calculate the chemical formula of a disaccharide

A

add all the carbons, hydrogens and oxygens in both monomers then subtract H20

31
Q

formula of 3 common disaccharides

A

C12H22011

32
Q

common disaccharides and their monosaccharide monomers

A

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

33
Q

the chains in polysaccharides may be

A

Branched or unbranched
Folded (making the molecule compact which is ideal for storage eg. starch and glycogen)
Straight (making the molecules suitable to construct cellular structures e.g. cellulose) or coiled

34
Q

Starch and glycogen are storage polysaccharides because they are…

A

Compact (so large quantities can be stored)
Insoluble (so will have no osmotic effect, unlike glucose which would lower the water potential of a cell causing water to move into cells, cells would then have to have thicker cell walls - plants or burst if they were animal cells)

35
Q

starch- alpha glucose

A

storage polysaccharide of plants (stored as granules in plastids e.g. chloroplasts)

36
Q

why does starch take longer to digest than glucose

A

it has many monomers

37
Q

starch is constructed from 2 dif. polysaccharides:

A

amylose (10-30%)
-1,4 GB between alpha glucose molecules
-unbranched
-helix (compact + more resistant to digestion)

amylopectin (70-90%)
-1,4 GB between alpha glucose molecules but also 1,6 GB making it
-branched
-not helix shape
-branches result in many terminal glucose molecules that can be easily hydrolysed for use during cellular respiration or added to for storage

38
Q

glycogen- alpha glucose

A

-storage polysaccharide of animals and fungi
-highly branched and not coiled (helix)
-more branched than amylopectin making it more compact which helps animals store more
-Liver and muscles cells have a high concentration of glycogen, as visible granules, as the cellular respiration rate is high in these cells (due to animals being mobile)
- branching enables more free ends where glucose molecules can either be added or removed - thus the storage or release of glucose can suit the demands of the cell 1,4 + 1,6

39
Q

cellulose structure

A

-long chains of beta glucose
-1,4 GB ; consecutive β-glucose molecules must be rotated 180° to each other
-Due to the inversion of the β-glucose molecules many H bonds (found between the parallel chains of microfibrils) form between the long chains giving cellulose it’s strength

40
Q

cellulose function

A
  • main structural component of cell walls due to its strength
    -high tensile strength so can be stretched without breaking so cell walls can withstand turgor pressure
    -cellulose fibres and other molecules (eg. lignin) form a matrix which increases the strength
  • strengthened cell walls provides support
    -Cellulose fibres freely permeable- water and solutes can leave or reach the cell surface membrane
    -As few organisms have the enzyme (cellulase) to hydrolyse cellulose it is a source of fibre
41
Q

iodine test for starch

A

-add a few drops of orange/brown iodine in potassium iodide solution to the sample
(iodine is in potassium iodide solution as iodine is insoluble in water)
-blue/black is +ve result

biology (12 decks)

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