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Biology Topic 1- Biological Molecules > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

What do carbohydrates consist of

A

Carbon, hydrogen and oxygen

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2
Q

What are monosaccharides

A

The monomers from which larger carbohydrates are made

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3
Q

What are 3 examples of monosaccharide

A

Glucose, fructose and galactose

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4
Q

What are disaccharides

A

2 monosaccharides joined together by a glycosidic bond which forms during a condensation reaction

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5
Q

What are 3 examples of disaccharides

A

Maltose
Sucrose
Lactose

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6
Q

What does a condensation reaction between 2 monosaccharides form

A

A glycosidic bond

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7
Q

What formula do all monosaccharides have

A

C6H12O6

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8
Q

What are the 2 isomers of glucose

A

Alpha glucose
Beta glucose

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9
Q

What is an isomer

A

Has the same chemical formula but a different structural formula

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10
Q

What is the difference between the structure of an alpha glucose and beta

A

The hydroxyl and hydrogen molecules are inverted

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11
Q

What are disaccharides

A

2 monosaccharides joined together by a condensation reaction which produces a molecule of water

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12
Q

What do all disaccharides have the formula of

A

C12H22O11

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13
Q

How is maltose formed

A

Formed by the condensation of 2 glucose molecules (glucose+glucose)

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14
Q

How is lactose formed

A

By the condensation of glucose + galactose

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15
Q

How is sucrose formed

A

By the condensation of glucose + fructose

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16
Q

What is the equation for a disaccharide reaction

A

C6H12O6 + C6H12O6 —-> C12H22O11 + H2O

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17
Q

How does the disaccharide reaction produce 1 molecule of water

A

Occur between the OH groups on carbon 4 of one monosaccharide and carbon 1 on the other monosaccharide creating 1,4 glycosidic bond

18
Q

What is the equation for hudrolisation with disaccharides

A

C12H22O11 + H2O —-> C6H12O6 + C6H12O6

19
Q

What are polysaccharides

A

Formed by the condensation of many repeating monosaccharides

20
Q

What are the 3 examples of polysaccharides

A

Starch ( formed by alpha glucose)
Glycogen (formed by alpha glucose)
Cellulose (formed by beta glucose)

21
Q

What are the difference between alpha and beta polysaccharides

A

In the cellulose polymer the monomers face in alternate directions rather than in the same way.
This is bc starch and glycogen are polymers of alpha glucose whereas cellulose is a polymer of beta glucose
In beta glucose the position of the hydrogen and hydroxyl groups on carbon atom 1 are inverted

22
Q

How is glycogen similar to starch

A

Both are polymers of alpha glucose
Both coiled into a helix
Both insoluble
Both 1,4 and 1,6 glycosidic bonds

23
Q

How is glycogen different from starch

A

Shorter chains
More highly branched- gives large surface area to be hydrolysed more quickly

24
Q

What are the main properties of glycogen

A

Coiled into a helix so it is compact and can fit into small spaces8
Large but compact molecule thus maximising the amount of energy it can store and doesn’t diffuse across cell membrane and out of cells
Insoluble so doesn’t affect water potential of cells and cannot diffuse out of them
Large number of side branches so energy can be released quickly as enzymes can act simultaneously on these branches

25
Q

What is starch formed by

A

The condensation of many alpha glucose monosaccharides

26
Q

What are the main properties of starch

A

The branches provide a larger surface area for enzymes to access and hydrolyse starch into glucose. Glucose is released more rapidly for resperation
Large molecule so doesn’t diffuse across cell membrane and out of cells
Coiled into helix so compact
Insoluble so doesn’t affect water potential

27
Q

What is cellulose

A

Main component of plant cell walls. Gives the cell support as it’s strong and rigid

28
Q

What are the main properties of cellulose

A

Long straight unbranched chains of beta glucose
Linked together with many hydrogen bonds to form microfibrils. They form hydrogen bonds with other microfibirls to form a cellulose fibres. Woven to form cellulose cell walls
Important in stopping the cell wall from bursting under osmotic pressure because it exerts inward pressure that stops the influx of water. Means that cell stays turgid and rigid to maximise the surface area of plants for PS

29
Q

What can Benedict’s reagent test for

A

Reducing sugars

30
Q

What are the reducing sugars

A

Glucose
Fructose
Galactose
Maltose
Lactise

31
Q

What is the method for testing reducing sugars

A

1) Add Benedict’s solution to the sample
2) heat up to 95 degrees (don’t boil)
3) if reducing sugars are present there will be a colour change from blue to orange/ red - positive resukt

32
Q

What is the only non reducing sugar

A

Sucrose

33
Q

What is method for food tests of non reducing sugars

A

1) do the Benedict’s test if it stays blue then it’s a negative result
2) boil a fresh sample with acid as it hydrolysed sucrose into monosaccharides
3) then neutralise with alkali (sodium hydrogen carbonate)
4) heat with Benedict’s solution at 95 degrees
5) if non reducing sugar is present there will be a colour change from blue to orange/red

34
Q

What is the food test for identifying starch

A

1) add iodine in potassium iodide solution to sample
2) colour change from orange to blue black if starch is present

35
Q

What is the difference in colour of results show

A

That Benedict test is semi quantitative as it can be used to estimate the approximative concentration of reducing sugars in a sample

36
Q

Suggest a war other than comparing colour changed in which different concentrations of reducing sugar could be estimated

A

Filter and dry the precipitate in each sample
Find the mean
The higher the mean of the precipitate the more reducing sugar is present

37
Q

How would you use a graph to determine something

A

Draw a line of best fit and the read the value you need

38
Q

Cotton is a plant fibre used to make cloth. Explain how cellulose gives cotton its strength

A

The many hydrogen bonds found between the parallel chains of microfibrils; [1 mark]
Cellulose fibres and other molecules (eg. lignin) found in the cell wall form a matrix; [1 mark

39
Q

Describe how the results from a colorimeter give fruit juice the higher sugar content

A

Higher absorbance
OR
Lower transmission

40
Q

Suggest why the water potential of apple juice decreases when apples are stored.

A
  1. Starch hydrolysed;
  2. Maltose is soluble, (so reduces Ψ)
    OR
    Starch is insoluble;
41
Q

Use of a colorimeter in this investigation would improve the repeatability of
the student’s results.
Give one reason why

A

Quantitative
OR
(Colour change is) subjective;
Accept: accurate/precise
2. Standardises (the) method;

Biology Topic 1- Biological Molecules (8 decks)

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