Carbohydrates Flashcards by Jillandra Perriman

What do carbohydrates consist of

Carbon, hydrogen and oxygen

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What are monosaccharides

The monomers from which larger carbohydrates are made

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What are 3 examples of monosaccharide

Glucose, fructose and galactose

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What are disaccharides

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

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What are 3 examples of disaccharides

Maltose
Sucrose
Lactose

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What does a condensation reaction between 2 monosaccharides form

A glycosidic bond

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What formula do all monosaccharides have

C6H12O6

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What are the 2 isomers of glucose

Alpha glucose
Beta glucose

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What is an isomer

Has the same chemical formula but a different structural formula

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

The hydroxyl and hydrogen molecules are inverted

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What are disaccharides

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

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What do all disaccharides have the formula of

C12H22O11

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How is maltose formed

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

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How is lactose formed

By the condensation of glucose + galactose

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How is sucrose formed

By the condensation of glucose + fructose

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What is the equation for a disaccharide reaction

C6H12O6 + C6H12O6 —-> C12H22O11 + H2O

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How does the disaccharide reaction produce 1 molecule of water

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

What is the equation for hudrolisation with disaccharides

C12H22O11 + H2O —-> C6H12O6 + C6H12O6

What are polysaccharides

Formed by the condensation of many repeating monosaccharides

What are the 3 examples of polysaccharides

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

What are the difference between alpha and beta polysaccharides

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

How is glycogen similar to starch

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

How is glycogen different from starch

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

What are the main properties of glycogen

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

What is starch formed by

The condensation of many alpha glucose monosaccharides

What are the main properties of starch

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

What is cellulose

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

What are the main properties of cellulose

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

What can Benedict’s reagent test for

Reducing sugars

What are the reducing sugars

Glucose Fructose Galactose Maltose Lactise

What is the method for testing reducing sugars

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

What is the only non reducing sugar

Sucrose

What is method for food tests of non reducing sugars

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

What is the food test for identifying starch

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

What is the difference in colour of results show

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

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

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

How would you use a graph to determine something

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

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

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

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

Higher absorbance OR Lower transmission

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

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

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

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