1. carbohydrates, polymers, sugars exam qs

What is a polymer?

Large molecule made of repeating units called monomers

Example of a polymer + monomer

Starch is a POLYMER, consisting of repeating glucose MONOMERS

What are the 5 main functional groups?

Aldehyde, alcohol, ester, ketone, carboxylic acid

What is a monosaccharide?

Single sugar

What is a disaccharide?

double sugar

What is a polysaccharide?

Polymers of sugar units

General formula for simple sugars?

(CH2O)n

What can ‘n’ be in the formula for simple sugars?

6, 5, 3

If a sugar has 6 carbons, what is it called?

Hexose

If a sugar has 5 carbons, what is it called?

Pentose

If a sugar has 3 carbons, what is it called?

Triose

What is the difference between alpha-glucose and beta-glucose?

OH and H are switched on C1 for beta-glucose

How is a disaccharide formed?

Joining 2 monosaccharides

What is formed in a glycosidic bond +what is the reaction called?

Water, condensation reaction

What is condensation the opposite of?

Hydrolysis

What does alpha-glucose + alpha-glucose make?

Maltose

What does alpha-glucose + galactose make?

Lactose

What does alpha-glucose and fructose make?

Sucrose

Function of maltose?

Breakdown product of starch

Function of lactose?

Sugar in mammalian milk

Function of sucrose?

Transport sugar in plants

What tests for starch?

Iodine test

How to perform iodine test?

Put 2cm cubed test solution into test tube, add 2 drops iodine solution, positive result = blue/black

What is the test for sugars? (reducing/ non reducing)

Benedict’s test

How to test for REDUCING SUGARS

2cm cubed test solution into test tube, add equal quantity benedict’s reagent, shake + heat for a few minutes in 95 degree water bath, positive result = green, brown or red

How to test for NON-REDUCING SUGARS

2cm cubed test solution into test tube, add equal quantity of dilute HCL, boil for a few mins to hydrolyse glycosidic bonds, neutralise- add small amounts of solid sodium-hydrogen-carbonate until it stops fizzing, positive result = green, brown or red

What is the positive result for sugars?

green = little sugar, brown = progressively more sugar, red = lots of sugar present

What does the emulsion test test for?

Lipids

How to perform emulsion test?

Shake some test material with 4cm cubed ethanol, filter liquid into test tube of water, leaving any solids behind, positive result: lipids precipitate in water, cloudy-white emulsion

What does the biurets test test for?

Proteins

How to perform biurets test?

2cm cubed test solution into test tube, add equal volume biuret solution down side of test tube, POSITIVE RESULT = blue ring at surface, disappears upon shaking, solution turns lilac-purple

What are the 3 polysaccharides?

Starch, cellulose, glycogen

4 similarities between glucose, cellulose and glycogen?

• Polysaccharides

• formed from monosacs to disacs to polysacs by a series of condensation reactions

• polymers of repeated sugar monomers,

• have the formula (C6H10O5)n

What is the function of starch?

energy storage in plants

What is the function of glycogen?

Energy storage in animals

What is the function of cellulose?

Used in cell walls

What is starch?

A large polymer of alpha-glucose monomers

3 properties of amylose? (area of starch)

Unbranched, helical, joined by 1,4 glycosidic bonds

2 properties of amylopectin?

Branched, has both 1,4 and 1,6 glycosidic bonds

Why does amylase work better on amylopectin?

it is branched- many ends for amylase to hydrolyse

What do 1,6 glycosidic bonds let us do?

Branch

What do 1,4 glycosidic bonds let us do?

Continue in length

How is starch adapted to it’s function? (3)

helical and branched- compact, store lots of glucose in a small space.

branching- many ends for amylase to hydrolyse, producing maltase faster.

very large molecule- insoluble, no osmotic effect on cell, doesn’t leave cell by diffusion

Why can’t starch dissolve in water?

Large molecule so it can’t fit between H20

Is glycogen branched or unbranched?

Branched

Is glycogen more or less branched than starch?

More branched

Glycogen is more branched than starch. What does this mean? (2)

• more ends means more hydrolysis, essential for animals which have a higher respiratory rate than plants.

• more compact means even more glucose can be stored in a small space

What is cellulose?

polysaccharide

B-glucose monomers

joined by 1,4 glycosidic bonds

Why are alternating glucose units flipped in cellulose?

OH and H on C1 are flipped for B-glucose, so alternate glucose units must 'flip ‘upside down’ for the bonds to form.

Why are cellulose chains straight?

Each bond angle is slightly over 180, but since it is alternating, it is corrected by the next unit.

Is cellulose branched or unbranched?

Unbranched

What bonds hold together many cellulose chains ?

Hydrogen bonds

What is a microfibril?

Lots of cellulose chains held together by hydrogen bonds

How does the structure of cellulose relate to its function? (2)

• many cellulose chains held together by hydrogen bonds to form microfibrils.

• laid down in different orientations in the plant cell wall, gives it high tensile strength in all directions.

• so, cell can swell up and become turgid without bursting.

What is a hydrogen bond?

Weak attractions between slightly negative and slightly positive areas of adjacent molecules

Why is water a polar molecule, and what does this mean about their bonds to each other?

Because one end is slightly positive and one end is slightly negative, so they are attracted to each other by hydrogen bonds

Give 2 examples of triglycerides.

Fats and oils

What are fats at room temperature?

solids

What are oils at room temperature?

liquids

What is a triglyceride?

3 fatty acids, 1 glycerol

What is lost in the formation of triglycerides?

3 water molecules

What bond forms in the formation of triglycerides?

Ester bond

Which sugar is non-reducing?

Sucrose

Which 2 sugars are semi-reducing?

Maltose, lactose

Which 3 sugars are reducing?

glucose, fructose, galactose

Are disaccharides reducing or non reducing?

Semi or non-reducing

Are monosaccharides reducing or non reducing?

Reducing

Which 2 factors affect the properties of lipids?

Fatty acid chain length, saturated/unsaturated fatty acids

How does fatty acid chain length affect the melting point of fats? (incl chain, forces, energy)

Larger chain, stronger intermolecular forces, takes more energy to melt, higher melting point, e.g fats.

How does a fatty acid being unsaturated affect the properties of lipids? (inlc mass, forces, mp)

Unsaturated fats lower molecular mass

weaker intermolecular forces,

ess energy is needed to break these forces

lower melting point

Why do unsaturated fats have a lower molecular mass?

Have less hydrogens as 2 are lost to form a double carbon bond

What fatty acids do oils have?

Short + unsaturated fatty acids

What type of fatty acids do fats have?

Long + saturated fatty acids

What are phospholipids compared to triglycerides, what makes them different?

Same as triglycerides, except 1 fatty acid is replaced by a phosphate group

In a phospholipid, which bit is hydrophobic and which bit is hydrophilic?

Head = hydrophilic, tail = hydrophobic

What are the 7 functions of lipids?

Waterproofing, insulation, buoyancy, energy store, membranes, mechanical protection, steroid hormones

What is a glycosidic bond?

Bond between sugars

What is starch?

polysaccharide made by plants from alpha glucose

What is amylose?

Unbranched component of starch

What is glycogen + where is it found?

Highly branched glucose storage polysaccharide, found in liver + muscle

What is cellulose?

Structural polysaccharide of plant cell walls, consisting of beta glucose monomers

What is a condensation reaction?

A type of reaction that joins 2 monosaccharides

What is hydrolysis?

A type of reaction that will break 2 monosaccharides

Why is starch osmotically inactive?

It is insoluble

This shape means that amylose is compact and therefore more easily stored.

Helical

Starch is made up of…

amylose and amylopectin

Salivary amylase digests starch into what?

maltose

During benedict’s test, Cu 2+ is reduced to what?

Cu+

What is a serial dilution?

Making a range of concentrations

What is a calibration used for?

Finding the concentration of an unknown substance

A colorimeter gives what type of data?

Quantitative

Describe how the structure of glucose relates to its function(4)

• Insoluble in water so doesn’t affect water potential

• branched- makes the molecule compact

• more ends for fast breakdown

• large molecule so can’t cross the cell membrane