Biological Molecules: Carbohydrates

Question 1

Why is water a polar molecule?

Answer 1

due to uneven distribution of charge
- hydrogen atoms are more positive than O2 atoms so one end is more + than the other

Question 2

Why is water an important molecule?

Answer 2

• It is a metabolite - for hydrolysis and condensation
• solvent where metabolic reactions occur

Question 3

Properties of water?

Answer 3

solvents - allows substances needed for body to dissolve/be transported around body e.g glucose
- high heat specific capacity - more energy needed to warm up water so less temp fluctuations
- provide stable habitat/optimum temp for enzyme activity
- large latent heat of vaporisation - cooling effect with Iittle water loss
- strong cohesion - molecules ‘stick tgt’ by hydrogen bonds - effective transport of water in tube like transport cells (surface tension at the air-water boundary is high)/ allows pond skate to float
- max density is at 4 degrees - ice will be less dense/float creating insulating layer , so prevents organisms from freezing

Question 4

How does water act as a solvent?

Answer 4

• water is polar, so positive parts of water molecule will be attracted to negative parts of solute and vice versa
• water molecule then surrounds the charged parts of solute/ion —> leads to solute dissolving

Question 5

What are monomers and polymers?

Answer 5

Monomers - smaller units from which larger molecules are made

Polymers - molecules made from a large number of monomers joined together in a chain

Question 6

What are macromolecules?

Answer 6

Very large molecules
- contain 1000 or more atoms /have high molecular mass

Question 7

What is a condensation reaction?

Answer 7

• occurs when monomers combine together by covalent bonds to form polymers or macromolecules (lipids) / water is removed

Question 8

What is hydrolysis?

Answer 8

-covalent bonds are broken when water is added.

Question 9

Covalent bond for carbohydrates/proteins and lipids?

Answer 9

Glycosidic
Peptides
Ester

Question 10

Covalent bond for nucleic acids

Answer 10

Phosphodiester

Question 11

What do carbs, lipids, proteins and nucleic acids contain?

Answer 11

Carbon and hydrogen
→carbon can form 4 covalent bonds - make compound very stable

Question 12

Why are carbon atoms key to organic compounds ?

Answer 12

→carbon can form 4 covalent bonds - make compound very stable
→ carbon atoms can form covalent bonds with oxygen, nitrogen and sulfur
→ carbon atoms can form straight chains , branched chains and rings

Question 13

Carbs functions?what elements do they contain?

Answer 13

Source of energy - glucose used for energy release in respiration
store of energy - glycogen stored in muscles/liver
structurally important - cellulose in cell walls of plants

Contains C, H, O
→ H and O Are present in 2:1 ratio

Question 14

What are Monosaccharides, give an example and function ?

Answer 14

Single sugar monomer, all are reducing sugars
E.g : glyceraldehyde (3C)
Ribose (5C)
Glucose (6C)

Function : source of energy in respiration / building blocks of polymers

Question 15

What are disaccharides , example and functions ?

Answer 15

A sugar formed from 2 monosaccharides joined by a glycosidic bond in a condensation reaction

E.g maltose : alpha glucose + alpha glucose
Sucrose : alpha glucose+ fructose
Lactose : alpha glucose + beta galactose

Function : - sugar found in germinating seeds (maltose)
- mammal milk sugar (lactose)
- sugar in sugar canes (sucrose)

Question 16

Polysaccharides definition, eg. And function?

Answer 16

Polymer formed by many monosaccharides joined by glycosidic bonds in a condensation reaction.

Examples: cellulose: beta glucose
Starch: alpha glucose ( amylose and amylopectin)
glycogen: alpha glucose

Function: energy storage ( plant-starch and
Animals - glycogen)
→ structural -cell wall

Question 17

What do proteins contain and function?

Answer 17

C, H, N ,O and some proteins have sulphur

Functions: → cell growth and Repair
→ structural
→ carrier molecules in cell membranes , antibodies, enzymes and hormones

Question 18

Nucleic acids contain and Function?

Answer 18

C, H, O, N AND P (phosphorus )
Functions:→ carry genetic code in organisms
→ control cellular processes

Question 19

What are reducing sugars?

Answer 19

→ can donate elections
→ reducing agent
→ can be detected by Benedict’s test

Question 20

What are non reducing sugars?

Answer 20

→ cannot donate electrons → cannot be oxidised.
→ detected by hydrolysis to break into monosaccharides then Benedict’s test

Question 21

3 types of monosaccharides?

Answer 21

Trisoses (3C)
Pentoses (5C)
Hexoses (6C)

Question 22

Function of glucose?

Answer 22

→ energy source

→ soluble, so transported is water

Question 23

What is an ISOMER?

Answer 23

Molecules that have the same molecular formula but different structures —> different properties

Question 24

Why is ribose and deoxyribose important?

Answer 24

• Pentose sugars found in nucleotides that make up RNA and DNA

Question 25

How are glycosidic bonds formed?

Answer 25

Two **hydroxyl (-OH) groups interact** to form strong covalent bond called **glycosidic bond** to form disaccharides/polysaccharides - water is removed

Question 26

How are glycosidic bonds broken?

Answer 26

HYDROLYSIS —> Disaccharides and polysaccharides are broken down - catalysed by enzymes/ water is added

Question 27

Examples of polysaccharides/what bonds do they contain?

Answer 27

STARCH - glycosidic bonds between **alpha glucose** molecules (1,4 and 1,6 - depends if amylose or amylopectin) GLYCOGEN- glycosidic bonds between **alpha glucose** molecules ( 1,4 and 1,6 BONDS = **BRANCHED**) CELLULOSE - glycosidic bonds between **beta glucose** molecules (1,4 Glycosidic bonds ) - beta glucose is an ISOMER of alpha glucose, so is rotated 180 degrees to form glycosidic bonds

Question 28

What is starch constructed of and what are their differences ?

Answer 28

AMYLOSE - **unbranded chain with 1,4** glycosidic bonds - **helix** shape is more compact so resistant to digestion AMYLOPECTIN - **branched chain with 1,4 and 1,6** glycosidic bonds

Question 29

Function of starch, glycogen and cellulose?

Answer 29

STARCH - storage polysaccharide in plants - stored as granules in plastids Amylose NOT BRANCHED - no need to rapid release of glucose in plants - amylopectin has branches so can be **easily hydrolysed** for use in cell respiration GLYCOGEN - storage polysaccharide of animals/fungi - **more branched** than amylopectin so more compact so animals can **store more/take up less space** - **easily condensed/hydrolysed** - release glucose quickly - **insoluble** - won’t affect WP CELLULOSE - main structural component of **cell walls** due to high strength due to hydrogen bonds between chains

Question 30

Structural differences between lactose and maltose?

Answer 30

LACTOSE: glucose + galactose monomer Contains alpha glucose Beta glycosidic bond Sugars are in opposing orientation MALTOSE : both monomers are glucose Alpha glucose Alpha glycosidic bond Both monomers are in same direction

Question 31

How does the structure if galactose allow it to be used a respiratory substrate?

Answer 31

- bonds within molecule contain energy - bonds are broken by enzymes - galactose is soluble so can move within cell

Question 32

Properties of cellulose?

Answer 32

Insoluble High tensile strength Form hydrogen bonds with neighbouring chains

Question 33

Describe method to measure concentration of lactose in unknown sample?

Answer 33

**Zero** the colorimeter Use **red filter** in colorimeter Use a series of known concentrations of lactose - prepare a **serial dilution**, add **reagent** to test (eg Benedict’s )/**test in colorimeter** Use results from known concs to **produce calibration curve** Test unknown sample/use graph to determine concentration

Question 34

Test for reducing/non reducing sugars?

Answer 34

REDUCING : add Benedict’s reagent (contains copper II sulphate ions) - heat sample in water bath - if reducing sugar is present , a **coloured precipitate** will form as copper (II) sulfate (2+) is reduced to copper (I) oxide (1+) which is **insoluble in water** (colour changes from BLUE to green, yellow,orange to brown/brick red depending on conc of reducing sugar NON REDUCING : **add dilute HCl (hydrolysis)** /heat in water bath - **neutralise** solution with sodium hydrogen carbonate (use indicator to see when it’s neutralised) /add a little more to create **alkaline conditions** - carry out above process to test (if colour changes, reducing sugars are present)

Question 35

Test for starch?

Answer 35

Add iodine dissolved in potassium iodide solution If starch is present goes brown/orange —> blue/black

Question 36

Test for glucose?

Answer 36

Use **test strips coated in reagent** /dip in solution you’re testing - **change colour** if glucose is present Colour change **compared to chart** to show concentration of glucose present

Question 37

What is the mobile and stationary phase in chromatography?

Answer 37

Mobile - where molecules can move - normally liquid solvents is mobile phase Stationary : where molecules can’t move Stationary phase is the chromatography paper /layer of gel,glass or plate

Question 38

Using paper chromatography to identify unknown amino acids?

Answer 38

1. Draw **pencil line** near bottom of chromatography paper /put **concentrated spot of mixture** of amino acids on it 2. Add **small amount of solvent** to beaker /dip bottom of paper into it (BUTAN-1-OL , GLACIAL ETHANOIC ACID /WATER used for amino acids) DO IN FUME CUPBOARD/cover with lid to stop solvent evaporating 3. As solvent spreads up paper, different amino acids move with it - at **different rates** so separate out 4. Mark **solvent front** once solvent nearly reached top /leave paper to dry 5. Spray paper with **ninhydrin solution** to turn amino acids **purple** otherwise can’t see tem - FUME CUPBOARD/GLOVES 6. Use **Rf vales to identify amino acids** - compare values to database/table to identify amino acids

Question 39

What is a biosensor ?

Answer 39

Device that uses a biological molecule such as an enzyme to detect a chemical - biological molecule produces a signal which is converted to electrical signal by transducer Electrical signal is processed

Question 40

How do glucose biosensors work?

Answer 40

Used to determine conc of glucose in solution - uses enzyme GLUCOSE OXIDASE/ELECTRODES Enzyme catalyses oxidation of glucose at electrodes - creates a charge which is converted to electrical signal by electrodes - electrical signal is processed to work out initial glucose conc

Question 41

When using a TLC plate why should you make sure the plate doesn’t touch the sides of the jar anywhere else?

Answer 41

Condensation on walls of jar may affect movement of spots