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biology > Biological molecules - Carbohydrates > Flashcards

Biological molecules - Carbohydrates Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what elements do carbohydrates contain

A

C, H and O

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2
Q

what is the general formula for carbohydrates

A

(CH2O)n

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3
Q

what are the functions of carbohydrates

A

source of energy e.g glucose
store of energy e.g starch and glycogen
structural units e.g cellulose (plants) chitin (insects)
components of nucleic acids, glycolipids

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4
Q

describe the structure of carbohydrates

A

carbohydrates can be monomers or polymers, meaning that they can be single molecules or larger molecules made of the same repeating units

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5
Q

how are carbohydrates classified

A

monosaccharides, disaccharides and polysaccharides

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6
Q

what are the properties of monosaccharides

A

sweet, soluble in water, form crystals

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7
Q

describe the structure of monosaccharides

A

can be straight chain or ring form
triose sugars contain 3 carbons
pentose sugars contain 5 carbons (e.g ribose, deoxyribose)
hexose sugars contain 6 carbons (e.g alpha glucose, beta glucose, galactose)

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8
Q

describe the structural difference between alpha and beta glucose

A

alpha glucose has a hydrogen above the hydroxyl group on carbon 1, whereas beta glucose has the hydrogen below the hydroxyl group on carbon 1

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9
Q

what are the uses of glucose in living organisms

A

reactant in respiration, source of energy, used to make larger molecules e.g glycogen

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10
Q

describe the differences between the structure of alpha glucose and ribose

A

alpha glucose is a hexose sugar whereas ribose is a pentose sugar
ribose has 10 hydrogen atoms whereas alpha glucose has 12
glucose has 4 hydroxyl groups and ribose has 3

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11
Q

what are disaccharides

A

two monosaccharides joined together by a glycosidic bond

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12
Q

what are the properties of disaccharides

A

sweet, soluble in water, form crystals

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13
Q

what is formed from two alpha glucose molecules

A

maltose

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14
Q

what is formed from glucose and fructose

A

sucrose

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15
Q

what is formed from glucose and galactose

A

lactose

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16
Q

which reaction is involved in the formation of disaccharides

A

condensation reactions

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17
Q

describe the formation of disaccharides

A

two hydroxyl groups interact between the monosaccharides - two hydrogen and 1 oxygen are removed and join to form water
a covalent bond called a glycosidic bond forms between carbon 1 and 4 on the glucose molecules.

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18
Q

which reaction is involved in the breakdown of disaccharides

A

hydrolysis reaction

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19
Q

describe the breakdown of disaccharides

A

the reaction needs water and is catalysed by enzymes

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20
Q

what are polysaccharides

A

polysaccharides are polymers - they are made of many repeating units of monosaccharides that have undergone condensation reactions to join them together.

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21
Q

how is the polymerisation of polysaccharides carried out in organisms

A

by enzymes

22
Q

give the properties of polysaccharides

A

not sweet, insoluble in water, can’t be crystallised

23
Q

where is starch found

A

in plants (starch granules)

24
Q

how is starch formed

A

many alpha glucose molecules join by glycosidic bonds during condensation reactions to form two different polysaccharides

25
Q

what are the two polysaccharides that make up starch

A

amylose and amylopectin

26
Q

describe the structure of amylose

A

formed when alpha glucose molecules are joined by 1.4 glycosidic bonds and forms a coiled structure

27
Q

how is the coiled structure of amylose maintained

A

by hydrogen bonds

28
Q

describe the structure of amylopectin

A

formed when alpha glucose molecules are joined by 1.4 glycosidic bonds and forms a coiled structure, but there are also branches formed by 1.6 glycosidic bonds

29
Q

what are the three properties of starch

A

insoluble in water, branched, compact

30
Q

why is it important that starch is insoluble

A

it does not affect the water potential of cells. glucose would lower the water potential and cause water to enter the cells by osmosis.
less likely to be lost from cells

31
Q

why is it important that starch is branched

A

enzymes can be used to remove glucose molecules (hydrolysis reaction). the branched structure of amylopectin means that lots of glucose can be removed quickly for respiration

32
Q

why is it important that starch is compact

A

being compact means starch does not take up a lot of space, making it a good energy storage molecule

33
Q

where is glycogen found

A

in animals (glycogen granules)

34
Q

describe the structure of glycogen

A

many alpha glucose molecules join by 1,4 glycosidic bonds with 1,6 glycosidic bonds forming branches

35
Q

how is glycogen different in structure to amylopectin

A

shorter 1,4 glycosidic chains, more 1.6 glycosidic bonds so more branched and more compact. this means it is easier to remove glucose molecules in glycogen

36
Q

what are the three properties of glycogen

A

insoluble in water, branched, compact

37
Q

why is it important that glycogen is insoluble

A

does not affect the water potential of cells
less likely to be lost from cells

38
Q

why is it important that glycogen is branched

A

enzymes can be used to remove glucose molecules (hydrolysis reaction). the very branched structure of glycogen means that lots of glucose can be released quickly for respiration

39
Q

why is it important that glycogen is compact

A

being compact means it does not take up a lot of space, making it a good energy storage molecule

40
Q

where is cellulose found

A

in plants (cell wall)

41
Q

describe the structure of cellulose

A

cellulose is made of long, unbranched chains of beta glucose molecules joined by 1,4 glycosidic bonds. The cellulose chains are held together by hydrogen bonds, forming strong fibres called microfibrils

42
Q

how are the chains of beta glucose formed in cellulose

A

to form the glycosidic bond, alternate beta glucose molecules are rotated through 180 degrees forming straight chains.

43
Q

how are the microfibrils formed in cellulose

A

the straight chains of beta glucose molecules have lots of hydroxyl groups projecting from carbon2. These form hydrogen bonds with adjacent cellulose molecules, forming microfibrils.

44
Q

what to microfibrils join to form

A

macrofibrils, which join to form fibres, which criss-cross in the cell wall giving extra strength

45
Q

what are the functions of cellulose

A

cell walls and fibre

46
Q

why do microfibrils and macrofibrils have a very high tensile strength

A

because of the glycosidic bonds and hydrogen bonds between chains.

47
Q

why is the high tensile strength of micro and macro fibrils important in the cell wall

A

it prevents plant cells from bursting when they are turgid

48
Q

why else is cellulose useful in the cell wall

A

fibres run in all directions, giving extra strength to the cell wall.
spaces between fibres mean the cell wall is fully permeable, allowing water and mineral ions to pass in and out of plant cells.

49
Q

why are turgid plant cells important

A

they help to support the structure of the whole plant

50
Q

why is cellulose important for fibre

A

cellulose forms the fibre in our diets needed to help maintain a healthy digestive system

51
Q

what makes cellulose good for cell walls

A

very strong and insoluble

biology (24 decks)

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