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alevel bio > Chap 2; Bio Molecules(carbs +water) > Flashcards

Chap 2; Bio Molecules(carbs +water) Flashcards

1
Q

2.2) point 1
Give the names of the different types of monosaccharides, including
Trisoses
Pentoses
Hexoses

A

Trisoses; glyceralderhyde
Pentoses; ribose
Hexoses; glucose, fructose, galactose

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2
Q

2.2) point 1
Describe the main difference between a glucose and b glucose

A

A glucose has the oh group below the ring,
But b glucose has the oh group above the ring
(On carbon one)

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3
Q

2.2) point 1
What is the relationship between between glucose and galactose,
And what is different about them

A

Both of them are isomers of each other
But for glucose, the OH group on the fourth carbon atom is above the ring
But for galactose, the OH group on the fourth carbon atom is below the ring

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4
Q

2.2) point 2
Defintion of a monosaccharide

A

A single sugar monomer

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5
Q

2.2) point 2
4 properties a of monoscarchides

A

-sweet tasing
-crystalline
-Dissolve in water
-small molecules which can move across membranes

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6
Q

2.2) point 2
2 functions of monosaccharides

A

-source of energy in respiration
-building blocks for polymers

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7
Q

2.2) point 2
Defintion of a monomer

A

Smallest units from which larger molecules are made from

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8
Q

2.2) point 2
Defintion of a polymer

A

Molecules made from a large number of monomers joined together in a chain

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9
Q

2.2) point 2
Defintion of a macromolecule

A

Large size organic molecules made up of smaller molecules
All consist of carbon
And most of which are polymers

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10
Q

2.2) point 2
Defintion of a disaccharide

A

A sugar,
joined together by 2 monosaccharides by a glycoidic bond
In a condensation reaction

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11
Q

2.2) point 2
Give the name of 3 disaccharides

A

Maltose
Sucrose
Lactose

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12
Q

2.2) point 2
What makes maltose,
And give the glycosidic bonding

A

a-glucose plus a-guvose
1,4 glycolic bonding

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13
Q

2.2) point 2
What makes sucrose,
Amd give the glycosidic bonding

A

A-glucose plus fructose
1,2 glycosidic bonding

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14
Q

2.2) point 2
What makes lactose,
And give the glycosidic bonding

A

A-glucose plus b-galactose
1-4 glycosidic bonding

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15
Q

2.2) point 2
Defintion of a polysaccharide

A

Macromolecules that’s are polymers,
Formed by many monosaccharides
Joined by a glycosidic bond in a condensation reaction
To form chains

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16
Q

2.2) point 3
What is an organic compound and why are they stable

A

Compounds that contain carbon and hydrogen, which are stable because carbon forms 4 strong covalent bonds

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17
Q

2.2) point 3
What are carbs made from
And give the general formula

A

Carbon, hydrogen, oxygen
Cn(h20)y

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18
Q

2.2) point 3
What is a covalent bond

A

Sharing of 2 or more electrons between 2 atoms

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19
Q

2.2) point 4. Which sugars are reducing sugars and which sugars are non reducing

A

All monosaccharides are reducing sugars,
So glucose, fructose and galactose

The only disaccharide that is a reducing sugar is maltose

The only non reducing sugar is sucrose which is a dissacharide

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20
Q

2.2) point 5
What is a condensation reaction

A

Reaction where monomers join together by covalent bonds to form polymers
And water is removed

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21
Q

2.2) point 5
How is a glycolic bond formed

A

It is a strong covalent bond, formed when two hydroxyl groups from different saccharides interact

And every glycolic bond formed, results in a water molecule being released

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22
Q

2.2) point 5
How are disaccharides formed

A

-In a condensation reaction
-Where 2 monosaccharides join together by a glycosidic bond
-Where the glycolic bond forms when two hydroxyl groups interact to form a strong covalent bond
-And a water molecule is released

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23
Q

2.2) point 6
What is hydrolysis

A

Reaction where polymers break down into monomers by breaking a covalent bond
When water is added

So a glycosidic bond is broken down using enzymes

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24
Q

2.2) point 6
Give 2 examples of where hydrolysis occurs

A

-digestion of food in the alimentary canal
-breakdown of stored carbohydrates in muscle and liver cells for respiration

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25
Q

2.2 point 5)
How do you form maltose, and give the bonding

A

Alpha glucose plus alpha glucose
1,4 glycolic bonding

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26
Q

2.2) point 5
How do you form sucrose, and give the bonding

A

Alpha glucose plus fructose
1.2 glycosidic bonding

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27
Q

2.2) point 5
How do you form lactose, and give the bonding

A

Alpha glucose plus beta galactose
1.4 glycosidic bonding

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28
Q

2.2)point 5
Explain whaat is a polysaccharide
And how a polysaccharides are formed

A

A macro elude which is a polymer

Formed when many monosaccharides
Take part in a condensation reaction
And join together by glycolic bonds
(Which are string covalent bonds
Which occur when 2 hydroxyl groups interact
And water is removed)
To form chains

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29
Q

2.2)point 5
What are the three types of chains that polysaccharides can form

A

Straight
Folded
Branched or unbranched

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30
Q

2.2) point 5
Name the storage polysaccharides and give the criteria that they must have;

A

Starch and glycogen

Inert
Insoluble, so that there is no osmotic effect
Compact, so that large quantities can be stored

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31
Q

2.2) point 7
Where is starch stored

A

Starch is the storage polysaccharide in plants and is stored in granules in plastids (such as chloroplasts)

32
Q

2.2) point 7
Describe the structure of amylose

A

-not branched
-forms 1,4 glycosidic bonds between alpha glucose molecules
-coiled/helix shaped, so it allows it to be more compact so that it can store a large amount of energy in a small place

33
Q

2.2) point 7
Describe the structure of amylopectin

A

-branched
-forms 1,4 glycolic bonds between alpha glucose molecules, but also 1,6 glycolic bonds ,

34
Q

2.2) point 7
How does the structure of amylopectin relate to its function

A

Because it is branched,
This means that terminal glucose molecules can be easily hydrolyzed for uses during cellular repsiration

(Bc there are more ends, and the ends are where the enzyme amylase binds to each one to break it down into amylose)

35
Q

2.2) point 7
What monomers are amylose and amylopectin made up of

A

Alpha glucose monomers

36
Q

2.2) point 7
Which organism is glycogen stored in

A

It is the storage polysaccharide in animals and fungi

37
Q

2.2)point 7
Give the structure of glycogen and explain how these structures relate to its function

A

-highly branched, more than amylopectin
Which allows for both condensation and hydrolysis reactions to occur more rapidly, as there are more terminal glucose Molecules. So glucose can therefore either be removed or released depending on the demands of the cell
-forms 1-4 glycosidic bonds between alpha glucose molecules, but also 1,6 glycocidic bonds

38
Q

2.2) point 7
Where is glycogen stored and why

A

In liver and muscle cells because cellular respiration is high here,
So because glycogen is highly branched, it means that condenstaiona nd hydrolysis reactions can occur rapidly and thus release for remove glucose, depending on the demands of the cell

39
Q

2.2) point 8
Describe the sturtcure of cellulose

A

-not branched
-forms 1,4 glycolic bonds between beta glucose molecules
-forms straight chain due to beta glucose inversions
-beta glucose molecules rotate 180 degrees to each other, which means that many hydrogen bonds form between ther chains

40
Q

2.2) point 7
Which monomers is glycogen made from

A

Alpha glucose monomers

41
Q

2.2) point 8
Which monomers is cellulose made from

A

Beta glucose monomers

42
Q

2.2) point 7
What type of bonds form between cellulose chains and explain why these bonds form

A

Hydrogen bonds
Because this is due to the inversion of the beta glucose molecules,
Which occurs because beta glucose is an isomer of alpha glucose,
So inorder tof rom the 1,4 glycolic bonds, beta glucose monomers need to be rotated 180 degrees to each other
-so this means that a straight chain formed
-straight chain means that chains can be parralel to each other
-so oh groups can be in close promxity to each other
-and so hydrogen bonds can form

43
Q

2.2) point 8
Give three properties of cellulose and explain why these properties occur

A

Rigidity
High tensile strength
And a straight chain rather than curved

All occur because of the hydrogen bonds that occur between the chains, due to the inversion of the beta glucose monomers

44
Q

2.2) point 8
Explain how the arrangement of cellulose molecules contributes to the function of plant cell walls and the cell membrane

A

-high tensile strength;
inversion of beta glucose molecules keeps cellulose in a straight chain
-which allows many chain to packed closely together each other so OH groups in close proximity and so allows hydrogen bonds to form between chains
-so cross linkages form which allow microfibrils and fibres to form
-and this wrapping of fibres in multiple layers provides additional strength

-also has high tensile strength due to the many hydrogen bonds which provide strength

-freely permeable;
-cellulose fibres are freely permeable because they have gaps between them bc they are made up of fibrils and fibres

45
Q

2.2)point 8
Why can cellulose act as a form of fibre

A

Because few enzymes have the enzyme cellulase to hydrolyse cellulose
So it can therefore act as a form of fibre as it is not digested

46
Q

Why is it an advantage that glycogen is branched

A

Contains many terminal glucose molecules
So ti allows for rapid hydrolization to produce energy for respiration

47
Q

How could you test that starch has been digested

A

-use Benedict’s test, to give a brick red precipitate
Bc if it is digested, it will break down into maltose, which is a reducing disaccharide

48
Q

Why is the Benedict’s test semi quantitative

A

Although the degree of colour change can give an indication of the concentration of reducing sugar present, it is still qualitative because you are just observing colour chnages
And you can only tell by the colors if a solution contains more or less reducing sugar, not the exact concentration

49
Q

How to determine the presence of reducing sugar in unknown solution (using a calorimeter)

A

Use a standard solution of known glucose concentration e.g. 10 mmol dm-3; [1 mark]
Perform a serial dilution to produce intermediate concentrations e.g. 0, 2, 4, 6, 8 and 10 mmol dm-3; [1 mark]
Perform Benedict’s test on all the solutions; [1 mark]
Measure absorbance using a colorimeter; [1 mark]
Plot a calibration curve AND measure the unknown solution’s absorbance against that curve; [1 mark]

50
Q

2 properties of water that make it a good solvent

A

Polar substance, so it can be attracted to and thus dissolve ions and otehr polar substances
Hydrogen bonding, allows it to surround other solute molecules to keep it dissolved

51
Q

Why can water resist temperture changes

A

Because it contains many hydrogen bonds
Between water molecules
So large amount of energy reuqired to break them
So large amount of energy required to change the temperture
So it therefore has a high specfic heat capacity

52
Q

what r the two types of bonds present in amylose

A

hydrogen bonds and 1-4 alpha glycoside linkages

53
Q

Why is water called a dipole

A

This is due to the uneven distribution of charge, (it has two different regions which are charged), this is because electrons are more strongly attracted to the oxygen atom rather than the hydrogen atom,
So oxygen has a partially negative charge and hydrogens have a partially positive charge

54
Q

A hydrogen bond is weaker than a …. But stringer than most…

A

Covalent bond,
Intermolecular forces

55
Q

State 6 properties of water

A

-less dense as a solid
-can act as a reagent
-good solvent
-high specific heat capacity
-high latent heat of vaoporisation
-has high surface tension ( due to cohesion )

56
Q

Explain why water acts as a good solvent and describe for which type of substances this is

A

-a good solvent for hydrophilic substances (such as ions or polar substances like glucose and amino acids0, due to its polarity and ability to form hydrogen bonds
-because water molecule will be attracted to polar or charged susbstances and due to its hydrogen bonding can surround it,
So the substance will become dissolved

57
Q

Explain why it is biologically important that water is a good solvent

A

Because this means that metabolites can be transported around efficiently and so chemical reactions can easily occur

58
Q

What are the type of substances for which water is not a good solvent

A

Hydrophobic substances such as uncharged or non polar substances like lipids

59
Q

Explain why water has a high specific heat capacity and explain how this is biologically important

A

-because due to the large amounts of hydrogen bonds present, a large amount of thermal energy is required to break these bonds,
-therefore a lot of heat entry is required to increase the temperature
-this means that the temperature does not fluctuate greatly
-and so a constant internal body temperature can be maintained(eg enzymes can have optimal temperature)

60
Q

Explain why water has a high latent heat of vaporisation

A

Because due to the many hydrogen bonds present, this causes water molecules to stick together
-so therefore a large amount of thermal heat energy is required to break these hydrogen bonds so that the molecules can escape as a gas and so vaporize
-this means that a large amount of heat energy can be lost even when a small amount of water is evaporated
-so provides a cooling effect (sweating and transpiration of leaves), without losing too much water
-and also means an organism will not freeze, because it is therfore unlikely yo change form a liquid into a solid (bc inorder for this got occur, organism must lose large amounts of heat energy )

61
Q

Explain what is meant by cohesion and what is meant by adhesion

A

Cohesion is the attraction between molecules of the same type
(Which is why water molecules are attracted to eachother through hydrogen bonding)
-an example of how the transpiration stream works, which is when water is continuously drawn upwards against pull of gravity
-and an example of how surface tension occurs

But adhesion is the attraction between different molecules that are not the same (eg water can be attracted to other polar or charged surfaces such as cellulose)
-allows for capillary action ot occur, eg when water moves up glass against force of gravity

62
Q

Explain how surface tension occurs

A

Water molecules are more strongly attracted to each other than to air
-so they are pulled inwards and towards each other which creates a ‘skin’ like surface, creating tension
-which allows pond skaters to travel on

63
Q

Explain how to conduct the simple Benedict’s test

A

1) add Benedict’s reagent to test tube and equal volume of sample solution
2)heat in a water bath for two mins
3)positive test result shows colour change from blue to brick red

64
Q

What is the purpose of perfuming a serial dilution

A

It creates standards to compare unknown concentrations against, because the concentration decreases by the same amount each time

65
Q

Explain how to conduct a serial dilution

A

1)Label 7 test tubes and then place 10% of a stock solution (known concentration) into test tube 1,
2)Take 1cm cube out of this and place into test tube 2. Then add 9cm of distilled water and mix
3) continue for each solution but for the last solution take away 1cm3 so that it has a total of 9cm3
4) perform bendnocts test on each tube, using same volume of Benedict’s reagent
5) the colour change can be attributed to the concentration of reducing sugar present so you can now compare the unknown solution with these

66
Q

Give four sources of error in the Benedict’s test

A

-colour change is qualitative
-if solutions left too long in the water they can all turn the same colour
-rate of colur change is dependant upon the temperature of the water bath however this is likely to fluctuate
-the colour will continue to change even after being removed from the water bath

67
Q

Give 3 ways to improve accuracy in the semi quantitative Benedict’s test

A

-use a graduated pipette instead of a measuring cylinder to improve precision
-perform serial dilutions on larger volumes in order to reduce % error
-use a colourimetrr to provide purely qunattive results

68
Q

Give one way to improve reliability in the Benedict’s test

A

—repeat the Benedict’s test for each dilution and then take an average

69
Q

Explain how a colourimter works

A

Light passes through the sample and depending on the concentration within the sample, different amounts of light are detected.
For a high concentration sample, a lot of light is absorbed in the sample, therfore less light is detected. So it therefore has a lower % transmission.
For a low concentration sample, a small amount of light is absorbed in the sample therfore a large amount is detected so it therfore has a higher % transmission

70
Q

Explain how to use a colourimter to find concentration of an unknown solution

A

-Perform serial dilutions and then Benedict’s test on each sample
-Use colourimter to find % transmission for each sample
-plot a calibration curve with x axis as conc of reducing sugar and y axis as % transmission
-measure transmission of unknown solution and then use the curve on the graph to find its conc

71
Q

Explain the difference between reducing and non reducing sugars and give examples of them

A

Reducing sugars can donate electrons but non reducing sugars can not
-all monosaccharides are reducing sugars, so glucose, fructose and galactose
-and maltose is the only disaccharide that is a reducing sugar

-sucrose is a non reducing sugar (and is a disaccharide)

72
Q

Explain the chemistry behind how reducing sugars work

A

Reducing sugars donate electrons and so are oxidized themselves( oilrig so lose electrons), therefore acting as a reducing agent.

73
Q

Explain in terms of chemistry why there is a colour change when Benedict’s is added to a reducing sugar

A

Benedicts reagent is a source of CU2+ ions, and so when reducing sugar is added, it donates electrons, recuing Cu2+ to Cu+. So the blue Cu (ii) becomes an insoluble red predicate of Cu(i) oxide

74
Q

Explain why non reducing sugars need to be hydrolyzed before reducing sugars can be detected

A

Non reducing sugars can not donate electrons
So They need to be hydrolyzed to break the glycocidic bond
To therfore break the dissachride into its two monosaccharides, where all monosaccharides are reducing sugars

75
Q

Explain how to perform Benedict’s test on non reducing sugars

A

-first perform the Benedict’s test as normal to see if a colour change happens and if a reducing sugar is present
-if there is no colour chanhe, either no sugar is present or then a reducing sugar is present
-add hydrochloric acid to the solution and heat in water bath for 2 mins, (bc the acid will hydrolyze the carb and break the glycolic bond)
-neutralize the solution by adding sodium hydrogencarbinate( bc Benedict’s will only work on an alkali solution), and can test this by adding red litmus
-carry out Benedict’s test and colour change to brick red means reducing sugar is present

76
Q

Explain which feature of the resulting monosaccharides (which have formed form breaking the glycodic bond in a non reducing sugar test), are responsible for colur change in Benedict’s test

A

The resulting monoscarchides have aldehyde or ketone functional groups which can donate an electron to Cu(ii) sulfate

77
Q

Give 3 roles of water in a cell

A

-Acts as a medium for chemical reactions to occur
-acts as a solvent for ions and polar substances to dissolve
-keeps temperature relatively constant since that reactions can happen at a constant rate

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