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Biology: Biological Molecules > Carbohydrates > Flashcards

Carbohydrates Flashcards

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1
Q

What type of molecule is a carbohydrate?

A

A polysaccharide

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2
Q

What is a polysaccharide?

A

molecules made form a large number of monosaccharides joined together

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3
Q

What is a monosaccharide?

A

Monomers from which larger carbohydrates are formed

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4
Q

What are the main monosaccharides?

A

-galactose
-fructose
-alpha glucose
-beta glucose

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5
Q

What bond does a condensation reaction between monosaccharides form?

A

Glycosidic

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6
Q

What is formed when two monosaccharides join together with a glycosidic bond in a condensation reaction?

A

Disaccharide

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7
Q

What are the main disaccharides?

A

-lactose
-sucrose
-maltose

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8
Q

How is maltose formed?

A

Condensation reaction and glycosidic bond of two ALPHA glucose molecules

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9
Q

How is sucrose formed?

A

Condensation reaction and glycosidic bond of a fructose and glucose molecule

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10
Q

How is lactose formed?

A

Condensation reaction and glycosidic bond of glucose and galactose molecule

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11
Q

What are the two isomers of glucose?

A

alpha and beta glucose

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12
Q

What is the structure of an alpha glucose molecule?

A

https://static.aqa.org.uk/assets/image/0018/235440/00055366-DA00046397-DB.png

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13
Q

What is the structure of beta glucose?

A

https://static.aqa.org.uk/assets/image/0008/235439/00055366-DA00046396-DB.png

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14
Q

What type of sugar is glucose?

A

Hexose

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15
Q

What is the formula for glucose?

A

C6H12O6

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16
Q

Which polysaccharides are formed from alpha glucose molecules?

A

Glycogen and Starch

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17
Q

Which polysaccharides are formed from beta glucose?

A

Cellulose

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18
Q

What are reducing sugars?

A

Sugar that can donate electrons or reduce another chemical

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19
Q

What molecules are reducing sugars?

A

all monosaccharides and some disaccharides (maltose)

20
Q

What is the reagent to test for reducing sugars?

A

Benedict’s reagent

21
Q

What is Benedict’s reagent?

A

Alkaline solution of copper (II) sulfate

22
Q

How do we test for a reducing sugar?

A

-Add 2cm3 food sample to test tube
-Add equal volume of Benedict’s reagent
-Gently heat mixture in boiling water bath for 5 minutes

23
Q

What happens to Benedict’s reagent if a reducing sugar is present?

A

Solution from blue to orange-brown colour

24
Q

What is an example of a non reducing sugar?

A

Sucrose

25
Q

How do we test for non reducing sugars?

A

-Add 2cm3 of food sample to 2cm3 Benedict’s reagent in test tube and filter
-Place test tube in gently boiling water bath for 5 minutes
-If Benedict’s reagent doesn’t change colour then a reducing sugar is NOT PRESENT
-Add another 2cm3 food sample to 2cm3 dilute HCl in test tube then in gently boiling water bath for 5 minutes
-Dilute HCl hydrolyse disaccharide into constituent monosaccharides
-Slowly add sodium hydrogen carbonate solution to test tube to neutralise HCl
-Test with pH to check solution is alkaline
-Re-test resulting solution by heating with 2cm3 Benedict’s reagent in gently boiling water bath for 5 minutes
-If non reducing in original sample, Benedict’s reagent will now turn orange-brown

26
Q

Why are polysaccharides suitable for storage?

A

Very large molecules so are insoluble

27
Q

How do we test starch?

A

-Place 2cm3 of sample in test tube
-Add two drops of iodine solution and shake or stir

28
Q

How is starch indicated using iodine?

A

Orange to blue black colouration

29
Q

Where is starch mainly found?

A

In plants as small grains

30
Q

What is starch formed from?

A

Alpha glucose

31
Q

What is the structure of starch?

A

-chains of alpha glucose monosaccharides linked by glycosidic bonds (1,4 and 1,6) formed in condensation reaction
-chains branched and unbranched
-amylose and amylopectin

32
Q

What is the structure of amylose?

A

unbranched chain of glucose molecules joined by 1-4 glycosidic bonds
coiled and compact

33
Q

What is the structure of amylopectin?

A

branched chain of glucose molecule joined by 1,4 and 1,6 glycosidic bonds
side chains

34
Q

What are the features for starch?

A

-insoluble: doesn’t affect water potential, no water drawn in by osmosis
-large/insoluble: doesn’t diffuse out of cells
-compact: a lot stored in small space
-hydrolysed for alpha glucose: transported and readily used in respiration
-branched: enzymes can hydrolysed and glucose monomers released rapidly

35
Q

Where is glycogen found?

A

animals and bacteria

36
Q

What is the structure of glycogen?

A

-chains of alpha glucose joined together by 1,4 and 1,6 glycosidic bonds
-highly branched
-many side branches
-large/compact

37
Q

What are the features of glycogen?

A

-insoluble: doesn’t affect water potential, doesn’t draw in water by osmosis
-insoluble: doesn’t diffuse out of cells
-compact: a lot stored in small space
-highly branched: hydrolysed by enzymes to release glucose for respiration

38
Q

What monosaccharides form cellulose?

A

Beta Glucose

39
Q

What is the structure of cellulose?

A

-long, unbranched chains of beta glucose joined by glycosidic bonds in a condensation reaction
-every other beta glucose is inverted
-1-4 glycosidic bonds
-run parallel to form microfibrils joined by hydrogen bonds

40
Q

How are microfibrils formed?

A

long cellulose chains running parallel to one another joined by hydrogen bonds

41
Q

Where is cellulose used?

A

In the cell walls of plant cells

42
Q

What does cellulose provide?

A

Rigidity

43
Q

What does the cellulose wall prevent?

A

Cell from bursting under osmotic gain

44
Q

How does cellulose prevent cells bursting under osmotic gain?

A

Exerts inward pressure that stops further influx of water, making cells turgid and push against each other

45
Q

How does cellulose provide support and rigidity, what features does it have?

A

-beta glucose form long straight unbranched chains
-cellulose chains run parallel and crossed linked by hydrogen bonds: collective strength
-chains grouped to form microfibrils: further provides strength

Biology: Biological Molecules (8 decks)

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