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B = Biological Molecules & Cells = > Carbohydrates > Flashcards

Carbohydrates Flashcards

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Organic Chemistry 101 flashcards
1
Q

What is a monosaccharide?

A

A small molecule which forms chemical bonds to produce a larger carbohydrate in a condensation reaction.

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2
Q

What is a disaccharide?

A

A carbohydrate that is produced by 2 monosaccharides forming a glycosidic bond in a condensation reaction.

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3
Q

What is a polysaccharide?

A

A carb that is produced when many glucose units form a glyosidic bond in a condensation reaction.

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4
Q

What is a monomer?

A

Smaller units that join together to form larger
molecules.

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5
Q

What are some examples of monomers?

A

Monosaccharides
Amino acids
Nucleotides

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6
Q

What is a polymer?

A

Molecules formed when many monomers join together.

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7
Q

What are some examples of polymers?

A

Polysaccharides
Protein
DNA / RNA

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8
Q

What is a condensation reaction?

A

When small molecules form a chemical bond to produce a larger molecule & water molecule is eliminated,

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9
Q

What is a hydrolysis reaction?

A

When a water molecule is used to break a chemical bond between 2 molecules.

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10
Q

Name the 3 hexose monosaccharides and where they are found.

A

Glucose (food)
Fructose (fruits)
Galactose (milk)

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11
Q

What is the general formula for monosaccharides?

A

C₆H₁₂O₆

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12
Q

What type of bond is formed when monosaccharides react?

A

A 1,4 or 1,6 glycosidic bond

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13
Q

Name 3 disaccharides and how they’re formed.

A

glucose + glucose –> maltose
glucose + fructose –> sucrose
glucose + galactose –> lactose

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14
Q

What formula do all disaccharides have?

A

C6H22O11

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15
Q

Draw the structure of α-glucose.

A

CH2OH at the 6th carbon
H element at both tops
OH ion at both bottoms

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16
Q

Draw the structure of β-glucose.

A

CH2OH at the 6th carbon
1x H element at one top and bottom
1x OH ion at one top and bottom

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17
Q

Describe the structure and function of starch

A

Polymer of α-glucose.
Energy source and storage found in plants.

Insoluble = doesn’t affect water potential (no osmosis)
Large = doesn’t diffuse out of cells.

Made from AMYLOSE and AMYLOPECTIN

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18
Q

Describe the features of amylose

A

Polymer of α-glucose.
Forms ONLY 1-4 glycosidic bonds.

Helix and unbranched structure.
Compact.

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19
Q

Why is it good for a molecule to be insoluble?

A

Won’t affect water potential of cells since it prevents osmosis to occur and water entering the cell which would swell and be damaged

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20
Q

Why is it good for a molecule to be large?

A

It cannot diffuse out of the cell

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21
Q

Why is it good to have a branched structure?

A

Many side branches means enzymes can act simultaneously at the ends of branches and ENERGY is released quickly.

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22
Q

Why is it good to have a compact structure?

A

Maximises the amount of energy it can store (as it fits a large amount in a small space)

23
Q

Describe the features of amylopectin.

A

Polymer of α-glucose.
Forms BOTH 1,4 & 1,6 glycosidic bonds.

Helix and branched structure.
Compact.

24
Q

Describe the structure and functions of glycogen.

A

Polymer of α-glucose.
Main energy source / storage in animals.

Forms BOTH 1,4 & 1,6 glycosidic bonds.

Branched structure.= many terminal ends for hydrolysis to glucose
Insoluble = doesn’t affect water potential
Large = doesn’t diffuse out of cells.
Compact = large energy release.

25
Q

What are the main things to look for in the features of a carbohydrate?

A

1# What type of glucose it’s made from
2# Whether it has both 1,4 & 1,6 glycosidic bonds
3# Whether it’s branched
4# Insolubility
5# Compact
6# Large
7# Fibrils
8# Helix or straight structure

26
Q

Describe the structure and function of cellulose.

A

Polymer of β-glucose.
Found in plant cell walls.
A structural unit = gives rigidity to plant cell walls (prevents bursting & holds stem up)
Hydrogen bonding between adjacent chains is found.

ONLY 1,4 glycosidic bonds
Straight-chain, unbranched structure
Alternate glucose molecules are rotated 180°

Forms microfibrils! = high tensile strength

27
Q

How are microfibrils formed?

A

Hydrogen bonds crosslinks between parallel strands.

28
Q

What is a reducing sugar?

A

Reducing sugars are able to donate electrons to other molecules (hence they reduce that molecule).

They act as reducing agents.

29
Q

What kind of carbohydrates are reducing sugars?

A

ALL monosaccharides are reducing sugars.
SOME disaccharides are reducing sugars.

30
Q

Which functional group do reducing sugars have?

A

O - C - OH

31
Q

What is a non-reducing sugar?

A

A non-reducing sugar cannot donate electrons to other molecules - they are not reducing agents.

32
Q

Describe the Benedict’s test for reducing sugars.

A

1~ Add an equal volume of Benedict’s reagent to food sample.
2~ Heat mixture in water bath at 100°C for 5mins.

Positive result: colour change from blue to green, orange, brick red precipitate forms

33
Q

Why is there a range of colours produced during the Benedict’s test?

A

The colour of the solution depends on the glucose concentration.

Green (0.1 concentration / M)
Orange (0.25 concentration / M)
Red (0.5 concentration / M)

34
Q

Describe the Benedict’s test for non-reducing sugars.

A

Negative result: Benedict’s reagent remains blue.
1~ Add 1cm³ of dilute HCl and boil in water bath for 5mins.
2~ Neutralise mixture with sodium hydrogen carbonate solution.
3~ Proceed with Benedict’s test.

If positive: contains non-reducing sugars.

35
Q

Why do we put a dilute acid (HCl) in the food sample?

A

It hydrolyses the non-reducing sugars disaccharides (e.g. sucrose) into monosaccharides by breaking the bonds between molecules.

Monosaccharides are reducing sugars and can be detected.

36
Q

Why do we neutralise the food sample with sodium hydrogen carbonate?

A

Benedict’s reagent requires an alkaline environment to work properly.

37
Q

Describe the test for starch.

A

1~ Place food sample on spotting tile
2~ Add few drops of iodine solution

Positive result: colour change from orange to blue-black.

38
Q

How can colorimetry be used to give qualitative results for the presence of sugars and starch?

A

1~ Make solutions with known concentrations.
(Record absorbance or (% transmission values)

2~ Plot calibration curve: absorbance / % transmission (y-axis), concentration (x-axis).

3~ Record absorbance / % transmission values of unknown samples.
Use calibration curve to read off concentration.

39
Q

Describe the lipid (emulsion test)

A

1~ Place food sample in test tube.
Add 3cm³ of ethanol.

2~ Shake lidded tube thoroughly to dissolve any lipid in sample.

3~ Add 3cm³ of water and shake gently.

Positive test: solution turns cloudy (white emulsion forms)

40
Q

Which 2 substances are branched molecules?

A

Amylopectin
Glycogen

41
Q

Which 2 substances are unbranched molecules?

A

Amylose
Cellulose

42
Q

A carbohydrate can be…

A

Monosaccharides
Disaccharides
Polysaccharides

43
Q

What are carbohydrates?

A

A molecule consisting of…
carbon
hydrogen
oxygen atoms

44
Q

What type of bond is formed when monosaccharides react?

A

1,4 and/or 1,6 glycosidic bonds.

44
Q

How do you prepare a food test?

A

1~ Grind the food sample with a pestle and mortar while adding distilled water to help dissolve.

2~ Filter the food sample and collect the food sample solution.

3~ Place liquid into a test tube.

45
Q

What is the name given to sugars with 6 carbon atoms? Give examples.

A

Hexose sugars

Glucose
Galactose

46
Q

What is the name given to sugars with 5 carbon atoms? Give examples.

A

Pentose sugars

Fructose
Ribose

47
Q

What is one key feature of monosaccharides?

A

They are hydrophilic and soluble in water due to the many OH (hydroxyl) groups.

48
Q

What is an isomer?

A

Molecules with the same molecular formulas, but different arrangements of atoms / structure.

49
Q

What’s the difference between amylopectin and glycogen?

A

Glycogen is very similar to amylopectin BUT has lots more side branches coming off it + shorter chains

50
Q

What’s the difference between amylopectin and glycogen?

A

Glycogen is very similar to amylopectin BUT has lots more side branches coming off it + shorter chains

51
Q

How do you test for the presence of protein? (Biuret test)

A

Biuret test confirms presence of peptide bonds,

1~ Add equal volume of NaOH to sample at room temp.
2~ Add drops of dilute copper (II) sulfate solution.
Swirl to mix.
Positive result: colour change - blue to purple.
Negative result: solution remains blue.

Steps 1 & 2 make Biuret reagent.

52
Q

What type of data does a Benedict’s solution test produce? What does it mean?

A

Semi-quantitative data =
gives an approximate idea of levels - range of values.

B = Biological Molecules & Cells = (26 decks)

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