3.1.2 Carbohydrates Flashcards

1
Q

What is an organic molecule?

A

A molecule that contains carbon

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2
Q

What are the monomers of carbohydrates?

A

Monosaccharides which are soluble

The general formula is (CH2O)n where n is between 3 and 7

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3
Q

What are the common monosaccharides?

A

Glucose, fructose and galactose

All contain 6 carbon atoms

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4
Q

How are monosaccharides joined?

A

A condensation reaction joins two monosaccharides together using a glycosidic bond (an oxygen atom connected diagonally) and produces one molecule of water

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5
Q

What is a disaccharide?

A

Two monosaccharides joined together

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6
Q

What are the main disaccharides?

A

Maltose: two glucose molecules
Sucrose: a glucose molecule and a fructose molecule
Lactose: a glucose molecule and a galactose molecule

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7
Q

What are the isomers of glucose?

A

Alpha and beta

Beta glucose has the OH and H swapped round

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8
Q

What are polysaccharides?

A

Long chains of monosaccharides joined in a condensation reaction

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9
Q

What are reducing sugars?

A

Sugars that donate electrons to other chemicals

All monosaccharides and some disaccharides are reducing sugars

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10
Q

What is the process and result of the Benedict’s test?

A

Benedict’s test: when a reducing sugar in liquid form is heated with Benedict’s reagent (alkaline solution of copper(II) sulphate) it forms an insoluble red precipitate of copper oxide
Blue=none, green=very low, yellow=low, orange=medium, red=high

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11
Q

How are glycogen, starch and cellulose formed?

A

Glycogen + starch = condensation of alpha glucose

Cellulose = condensation of beta glucose

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12
Q

What are the types of glycosidic bond?

A
(1,4) = between carbon 1 on one glucose and carbon 4 on another glucose, forms a straight chain
(1,6) = glycosidic bonds between (1,4) chains, called branching
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13
Q

What is starch?

A

Plant-based
Collective term for amylose (1,4) and amylopectin (1,6)
Amylose coils due to hydrogen bonding of monosaccharides, straight chains of amylopectin also coil
Insoluble- doesn’t affect water potential
Unbranched state forms a spiral coil- compact
Large- doesn’t diffuse out of cells
When hydrolysed it forms alpha glucose- easily transported and readily used in respiration
Branched form has many ends- many enzymes can act simultaneously so that glucose is released rapidly

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14
Q

What is glycogen?

A

Animal based
Insoluble- doesn’t draw water out of the cell by osmosis
Compact- a lot can be stored in a small space
More branched than starch- glucose monomers are released more rapidly

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15
Q

What is cellulose?

A

Plant based
Only exits in straight chains- stacks to form a dense cell wall that stops the plant cell from bursting
Lots of hydrogen bonds: very strong structure even though single hydrogen bonds are very weak
Cellulose molecules group to form microfibrils then group to form fibres- very strong

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16
Q

How do you test for starch?

A

Iodine test: iodine turns starch black

17
Q

What is the structure of alpha and beta glucose?

A

See card

18
Q

What is the name of the test for reducing sugars?

A

Benedict’s test

19
Q

How do you test for a non reducing sugar?

A

Same as Benedict’s test but:
Add hydrochloric acid of equal volume to the sample to hydrolyse the sample
Then add sodium hydrogen carbonate solution to neutralise the acid
Benedict’s reagent does not work in acidic conditions