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AQA Biology > Biological Molecules (CARBOHYDRATES) > Flashcards

Biological Molecules (CARBOHYDRATES) Flashcards

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1
Q

Define a monomer

A

monomers are smaller, basic units which can create larger molecules

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2
Q

Give some examples of monomers

A

amino acids, glucose, nucleotides, monosaccharides

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3
Q

Define a polymer

A

molecules from a large number of monomers joined together

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4
Q

Give some examples of polymers

A

DNA, cellulose, starch, glycogen

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5
Q

Define a condensation reaction

A

A reaction which joins 2 molecules (monomers) together with the formation of a chemical bond and the elimination of a water molecule

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6
Q

What is the opposite of a condensation reaction

A

A hydrolysis reaction - breaks a chemical bond between 2 molecules and involves the use of a water molecule

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7
Q

What are monosaccharides

A

Monosaccharides are the monomers from which larger carbohydrates are made (monomers specific to carbohydrates)

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8
Q

Give 3 monosaccharides

A

Glucose
Fructose
Galactose

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9
Q

How are disaccharides formed

A

By the condensation of 2 monosaccharides which forms a glycosidic bond

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10
Q

Give the 3 disaccharides

A

Maltose
Sucrose
Lactose

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11
Q

How is maltose formed

A

Glucose + glucose

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12
Q

How is sucrose formed

A

Glucose + fructose

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13
Q

How is lactose formed

A

Glucose + galactose

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14
Q

What are the 2 isomers of glucose

A

alpha (α) & beta (β) glucose

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15
Q

What is the difference in structure between alpha glucose and beta glucose

A

In alpha glucose, carbon 1 has the H at the top and OH at the bottom whereas the H is at the bottom and OH is at the top in beta glucose

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16
Q

What glycosidic bond does maltose form

A

A 1 -4 glycosidic bond

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17
Q

How are polysaccharides formed

A

Polysaccharides are formed by the condensation of many glucose monomers

18
Q

Give three polysaccharides

A

starch
glycogen
cellulose

19
Q

what monomer is starch formed from

A

alpha glucose - amylose and amylopectin

20
Q

Compare structure of amylose and amylopectin

A

amylose is an unbranched chain of alpha glucose that only has 1-4 glycosidic bonds which gives it a tight, coiled helix structure. This is due to the hydrogen bonding within amylose. Whereas amylopectin has 1-4 and 1-6 glycosidic bonds which gives it a branched structure

21
Q

Where is starch found

A

Only in plant cells (eg: in chloroplasts)

22
Q

what is the function of starch

A

It is an insoluble store of glucose

23
Q

What are the properties of starch that make it suited to its function

A

It is insoluble - doesn’t affect water potential of cell so it doesn’t cause water to enter cell by osmosis which would make the cell turgid.

Helical structure = coiled structure → makes it compact = can fit more into a small space (= good for storage)

The branched structure increases surface area for rapid hydrolysis back to alpha glucose so glucose is easily released for respiration

24
Q

what monomer is glycogen formed from

A

alpha glucose
( Glycogen is a polymer of alpha glucose)

25
Q

where is glycogen found

A

in muscle and liver cells

26
Q

what is the function of glycogen

A

stores excess glucose

27
Q

How is glycogen’s structure related to its function

A

Glycogen has a similar structure to amylopectin, except it has a lot more branches due to more 1 - 6 glycosidic bonds, Loads of branches means glucose can be quickly and easily released in respiration → important for energy releases in animals

It is insoluble and so doesn’t draw water in by osmosis. or affect water potential

It is compact, making it good for storage

28
Q

Despite both starch and glycogen being branched molecules, why is glycogen more branched

A

Glycogen is found in animals and humans - they are more metabolically active than plants - branched structure means glycogen can hydrolysed to alpha glucose and be used in respiration

29
Q

What monomer is cellulose formed from

A

Beta glucose

30
Q

where is cellulose found

A

In cell wall of plant cells

31
Q

What is the function of cellulose

A

Cellulose provides structural strength and support to plant cells

32
Q

Describe the structure of cellulose

A

only contains 1-4 glycosidic bonds which creates long straight chains. These long straight chains lie parallel to each other and are held together by many hydrogen bonds.

33
Q

What do chains of cellulose molecules form

A

Microfibrils which eventually form fibres

34
Q

How is cellulose’s structure related to its function

A

Every other beta glucose molecule is flipped 180 degrees (inverted) so hydrogen bonds can form between cellulose chains. Individual hydrogen bonds are weak but due to the large number of them, collectively they provide strength

35
Q

What is a reducing sugar

A

Sugars that can donate electrons to another chemical e.g. Benedict’s reagent

36
Q

Describe the test for reducing sugars

A

1) Mix equal volumes of test sample and benedicts reagent
2) Heat in water bath at 80 degrees celsius
Positive test result shows solution turn from blue to brick red (brick red means a stronger concentration of reducing sugar present)

37
Q

Describe the test for non reducing sugars

A

1) Do the reducing sugar test
2) Add hydrochloric acid
3) Heat in water bath for 2 mins (short period of time)
4) Add sodium hydroxide (an alkali) for neutralisation
5) Add benedicts reagent
6) Heat in water bath
Positive test result shows solution change to a brick red colour

38
Q

What’s a more accurate way of comparing the amount of reducing sugar in different solutions than colour change

A

Filter solution, dry precipitate and weigh it

39
Q

Why is hydrochloric acid added in the test for non reducing sugar

A

To provide hydrolysis and break the non-reducing sugar (disaccharide) into monosaccharides

40
Q

Give the name of a non reducing sugar

A

Sucrose

41
Q

Describe the test for starch

A

1) Mix iodine/potassium iodide with test solution
2) Positive test result shows solution goes from browny orange to a blue/black colour

AQA Biology (4 decks)

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