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Biology Alevel > Biological Molecules: Carbohydrates > Flashcards

Biological Molecules: Carbohydrates Flashcards

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1
Q

Why is water a polar molecule?

A

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

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2
Q

Why is water an important molecule?

A
  • It is a metabolite - for hydrolysis and condensation
  • solvent where metabolic reactions occur
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3
Q

Properties of water?

A

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

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4
Q

How does water act as a solvent?

A
  • 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
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5
Q

What are monomers and polymers?

A

Monomers - smaller units from which larger molecules are made

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

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6
Q

What are macromolecules?

A

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

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7
Q

What is a condensation reaction?

A
  • occurs when monomers combine together by covalent bonds to form polymers or macromolecules (lipids) / water is removed
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8
Q

What is hydrolysis?

A

-covalent bonds are broken when water is added.

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9
Q

Covalent bond for carbohydrates/proteins and lipids?

A

Glycosidic
Peptides
Ester

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10
Q

Covalent bond for nucleic acids

A

Phosphodiester

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11
Q

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

A

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

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12
Q

Why are carbon atoms key to organic compounds ?

A

→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

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13
Q

Carbs functions?what elements do they contain?

A

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

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14
Q

What are Monosaccharides, give an example and function ?

A

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

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15
Q

What are disaccharides , example and functions ?

A

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)

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16
Q

Polysaccharides definition, eg. And function?

A

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

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17
Q

What do proteins contain and function?

A

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

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

18
Q

Nucleic acids contain and Function?

A

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

19
Q

What are reducing sugars?

A

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

20
Q

What are non reducing sugars?

A

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

21
Q

3 types of monosaccharides?

A

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

22
Q

Function of glucose?

A

→ energy source

→ soluble, so transported is water

23
Q

What is an ISOMER?

A

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

24
Q

Why is ribose and deoxyribose important?

A
  • Pentose sugars found in nucleotides that make up RNA and DNA
25
Q

How are glycosidic bonds formed?

A

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

26
Q

How are glycosidic bonds broken?

A

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

27
Q

Examples of polysaccharides/what bonds do they contain?

A

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

28
Q

What is starch constructed of and what are their differences ?

A

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

29
Q

Function of starch, glycogen and cellulose?

A

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

30
Q

Structural differences between lactose and maltose?

A

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

31
Q

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

A
  • bonds within molecule contain energy
  • bonds are broken by enzymes
  • galactose is soluble so can move within cell
32
Q

Properties of cellulose?

A

Insoluble
High tensile strength
Form hydrogen bonds with neighbouring chains

33
Q

Describe method to measure concentration of lactose in unknown sample?

A

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

34
Q

Test for reducing/non reducing sugars?

A

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)

35
Q

Test for starch?

A

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

36
Q

Test for glucose?

A

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

37
Q

What is the mobile and stationary phase in chromatography?

A

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

38
Q

Using paper chromatography to identify unknown amino acids?

A
  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
39
Q

What is a biosensor ?

A

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

40
Q

How do glucose biosensors work?

A

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

Biology Alevel (26 decks)

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