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Biology Alevel > Biological Molecules( Biological Molecules ) > Flashcards

Biological Molecules( Biological Molecules ) Flashcards

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1
Q

What are the four elements amino acids are made up from

A

Carbon , hydrogen ,oxygen and nitrogen

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2
Q

What do amino acids often contain (2 elements )

A

Sulphur and phosphorus

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3
Q

What test detects proteins

A

Buiret test detects the prescience of peptide bonds .

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4
Q

What is a dipeptide

A

Two amino acids

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5
Q

How are dipeptides created

A

Condensation of two amino acids forms a dipeptide bond held by a peptide bond

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6
Q

What happens when a dipeptide is created

A

The peptide bond is formed between the CH (carboxyl) group on first amino acid and amino group on second amino acid which also releases water

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7
Q

What is the name for the reaction breaking the disaccharide

A

Hydrolysis reaction splits apart the disaccharide leaving 2 monosaccharides

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8
Q

What is polymerisation (amino acids)

A

Dipeptides can become polypeptides in repeated condensation reactions

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9
Q

Example peptide bond question : if you have 383 amino acids , how many peptide bonds do you have?

A
  1. (-1 as 3 amino acids only has 2 peptide bonds )
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10
Q

What does the primary structure of a protein determine

A

It’s shape and function

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11
Q

What is the primary structure protein

A

It’s a chain of amino acids joined in condensation reactions by peptide bonds , creating a specific sequence of amino acids . Which therefore dictates its bonds and therefore structure and function

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12
Q

What is the secondary structure protein

A

Either alpha helix or beta pelted sheet , hydrogen bonds form which causes the long polypeptide chain to be twisted into a 3D shape.

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13
Q

What is the tertiary structure of proteins

A

Can be twisted and folded into more complex 3D shapes which is maintained by a number of different bonds

Hydrogen bonds -between amino and carboxyl to maintain shape
But easily broken
Ionic bonds -are easily broken by changes in ph . Polar interactions of the R groups maintain shape
Disulphide bridges -fairly strong not easily broken .

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14
Q

Why is the 3D shape of a protein so important

A

It makes each protein distinctive and allows it to recognise and be recognised by other molecules , it can then interact with them in a very specific way.

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15
Q

What is the quaternary structure

A

Quaternary protein structures are made of 2 or more tertiary proteins joined together by all the same bonding as tertiary

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16
Q

How is haemoglobin a quaternary structure

A

Haemoglobin consists of 4 tertiary structures bonded together with iron in the middle

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17
Q

what is the structural formula for glucose

A

CH2OH (C6H12O6)
c o
c h oh h c h oh
h c c c
ho h oh

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18
Q

describe how hydrolysis works with a disaccharide?

A

when water is added to a disaccharide under suitable conditions it breaks the glycocidic bond releasing the monosaccharides.

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19
Q

what is a monosaccharide

A

a simple sugar molecule( one unit of carbohydrate)

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20
Q

what elements do all carbohydrates contain?

A

all carbohydrates contain only carbon , hydrogen and oxygen

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21
Q

give 3 examples of monosaccharides

A

glucose , galactose , fructose

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22
Q

are monocaccharides soluble or insoluble

A

soluble

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23
Q

what is the general formula of a monosaccharide

A

(Ch20)n

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24
Q

what do monosaccharides end in

A

‘ose’

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25
Q

what is hexose

A

hexose is a sugar which contains 6 carbon atoms glucose is an example of a hexose

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26
Q

in alpha glucose the OH on carbon 1 is on the bottom how is it in beta glucose?

A

it is flipped so the OH (carboxyl) group is above

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27
Q

how do disaccharides form?

A

through condensation reactions which water is removed and a glycocidic bond is formed between c1 and c4

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28
Q

examples of disaccharides

glucose + glucose =

A

maltose (malt sugar) 2 glucose molecules joined by an alpha 1-4 glycocidic bond

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29
Q

glucose + fructose =

A

sucrose . joined by an alpha 1-4 glycocidic bond

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30
Q

galactose + glucose =

A

lactose (milk sugar) . joined by a 1-4 glycocidic bond

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31
Q

what are the 2 main functions of monosaccharides

A

they are used as a primary energy source for fuelling metabolism and joining together to form ccarbohydrate macromolecules

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32
Q

what are isomers

A

isomers are compounds with the same chemical formula but different arrangements of atoms so have different properties. for example glucose - alpha and glucose -b are both c6h12o6 but the oh and h are flipped round

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33
Q

give 3 examples of polysaccharides and state if they are in plant or animals

A

starch (plant) , glycogen (animal) and cellulose(plant)

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34
Q

why are polysaccarides insoluble

A

because they are very large molecules

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35
Q

what are the two types of starch

A

amylose and amylopectin

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36
Q

describe amylose

A

amylose is unbranched and monomers are connected by an alpha 1-4 glycocidic bond and is wound into a tight coil which makes it compact

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37
Q

describe amylopectin

A

amylopectin is branched with 1-4 and 1-6 bonds

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38
Q

describe glycogen

A

glycogen is branched 1-4 bonds and 1-6 bonds it is insoluble , compact .

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39
Q
A
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40
Q
A
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41
Q

What are the two types of proteins and what they have and an example

A

Fibrous have structural functions eg collagen and globular have metabolic functions eg enzymes and haemoglobin

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42
Q

Describe fibrous proteins

A

Fibrous proteins form long chains which run parallel to one another . These chains are linked by cross bridges and so form very stable molecules.

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43
Q

Why are fibrous proteins generally insoluble in water

A

Fibrous proteins have a large proportion of amino acids with hydrophobic r groups , this means unlike globular proteins , fibrous proteins are insoluble in water

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44
Q

What is the shape of fibrous proteins

A

Long and narrow

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45
Q

What is the shape of globular proteins

A

Round / spherical

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46
Q

What is the acid sequence of fibrous proteins

A

Repetitive amino acid sequence

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47
Q

What is the acid sequence of globular proteins

A

Irregular amino acid sequence

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48
Q

How durable are fibrous proteins

A

They are less sensitive to changes in PH, TEMP etc than globular

49
Q

How durable are globular proteins

A

More sensitive to changes in PH , temp etc than fibrous

50
Q

Give 6 examples of fibrous proteins

A

Collagen , myosin , fibrin , actin , keratin , elastin

51
Q

Give 4 examples of globular proteins

A

Enzymes , haemoglobin , insulin , immunoglobulin

52
Q

Are globular proteins soluble or insoluble in water

A

Generally soluble in water

53
Q

What are enzymes structure

A

A chain of amino acids in a globular tertiary structure

54
Q

How do enzymes speed up a reaction

A

Reduces the activation energy

55
Q

What is the word for bond breakage

A

Catabolic

56
Q

What is the word for bond formation

A

Anabolic

57
Q

What is the word for inside cell reactions

A

Intracellular

58
Q

What is the word for outside cell reactions ( eg tissue fluid , blood )

A

Extracellular

59
Q

What is the induced fit theory

A

Active site does not fit substrate so The active site can be partially flexible enzyme active site changes shape slightly so they are complementary , and therefore enzyme-substrate complex forms and so a substrate can bind even when it’s not a perfect fit .
Therefore bending bonds in substrate leading to a reaction

60
Q

What is the lock and key theory

A

Random movement causes the enzyme and substrate to collide , and the substrate enters the active site . Enzyme - substrate complex forms . Charged groups attract distorting the substrate and aiding catabolic or anabolic . Then products are released from the active site leaving the enzyme unchanged and ready to accept another substrate molecule

61
Q

What does it mean when an enzyme is denatured

A

The active site of an enzyme changes shape and can no longer fit the substrate

62
Q

How are enzyme reactions affected

A

Temperature , ph , enzyme concentration , substrate concentration and the presence of inhibitors

63
Q

Define a catalyst

A

A substance that alters the rate of a chemical reaction without undergoing permanent change

64
Q

what is an inhibitor

A

they are subtances that directly or indirectly interfere with the functioning of the active site of an enzyme and so reduce its activity

65
Q

define a competitive inhibitor

A

a substance which binds to the active site of an enzyme

66
Q

define a non competitive inhibitor

A

a substance which binds to an enzyme at a postition other than the active site

67
Q
A
68
Q

What is a reducing sugar

A

One which can donate an electron to another molecule

69
Q

What’s the test for a reducing sugar

A

Add 2cm^3 sample to a test tube , if not already liquid grind add water and filter , add 2cm^3 Benedict’s reagent 3. Ensure the solutions are mixed by gently tilting , heat the mixture in a water bath for 5 min

70
Q

Test for non reducing sugars

A

Add 2 cm^3 sample to a test tube then add 2cm^3 of dilute hydrochloric acid and heat for 5 min in a water bath to hydrolyse the glycosidic bonds then add sodium hydrogen carbonate solution drop by drop to neutralise the acid (it will fizz) , test with universal indicator paper to ensure it has neutralised if not keep adding solution . Then add 2cm^3 Benedict’s reagent and heat in a water bath

71
Q

what are the two types of lipids

A

triglycerides and phospholipids

72
Q

how are triglycerides made

A

made up of 2 different molecules , glycerol and 3 fatty acids . 3 condensation reactions (releasing h20) forming ester bonds

73
Q

where are the ester bonds in a triglyceride

A

between the carbons and oxygen from fatty acids and glycerol

74
Q

what are the functions of lipids

A

buoyancy in marine mammals , cell membranes , energy storage , insulation , metabolic water and protection of organs

75
Q

how can lipids be a source of energy

A

when oxidised lipids provide more than twice the energy as the same mass of carbohydrate and release valuble water

76
Q

how do triglycerides provide metabollic water for eg camels

A

as they have a high ratio of hydrogen to oxygen atoms triglycerides release water when oxidised and therefore provide an important source of water

77
Q

how are lipids good at waterproofing

A

lipids are insoluble in water and therefore useful as a waterproofing

78
Q

what is ther r group on the fatty acids

A

the straight chain of carbon atoms

79
Q

what does it mean if the lipid is saturated

A

The fatty acid hydrocarbon chain has only single bonds between carbons . they tend to be solid at normal temps because they can be tightly packed

80
Q

what does it mean if the lipid is unsaturated

A

The fatty acid hydrocarbon chain consists of at least one double bond between carbons . doesnt have enough hydrogens . normally liquid

81
Q

what is a phospholipid made of

A

phosphate , glycerol and fatty acids

82
Q

why is phospholipids polar

A

They have two charged regions .they have a hydrophillic head and a hydrophobic tail therefore they can position themselves so that the hydrophillic heads are as close to the water as possible and hydrophobic as far away as possible

83
Q

what is the bond between fatty acids and glycerol called

A

ester bond

84
Q

what is the test for lipids

A

emulsion test .

  1. take a completely dry and grease free test tube
  2. if sample is sold break up into very small peices . if liquid just add 2 cm 3 of sample . then add 5cm3 ethanol
  3. shake the tube thoroughly to dissolve any lipid in the sample
    4.add 5cm3 of water and shake gently add distilled water
  4. a milky white emulsion indicates the prescence of a lipid if its clear none prescent
    6.as a control repeat proceedures using water instead of the sample and this should stay clear
85
Q

why is there a cloudy colour

A

the cloudy colour is due to any lipid in the sample being finely dispersed in the water. to form a emulsion light passing through the emulsion is refracted as it passes from oil to water droplets making it appear cloudy

86
Q

What kind are animal lipids and what do they occur as

A

Animal lipids are saturated and occur as fats eg butter

87
Q

What kind are plant lipids and what do they occur as

A

Plant lipids are unsaturated and occur as oils eg olive oil

88
Q

What is the initial rate of a reaction

A

The instantaneous rate at the start of the reaction

89
Q

Why is rate initially high

A

Lots of substance , rate slows down over time as amount of substance decreases

90
Q

what is collagen an example of

A

a fibrous protein

91
Q

what is the primary structure of collagen

A

an unbranched polypeptide chain

92
Q

what is the secondary structure of collagen

A

very tightly wound polypeptidechain

93
Q

how does collagen pack closely

A

it has lots of the amino acid glycine

94
Q

what is the tertiary structure of collagen

A

the chain is twisted into a second helix

95
Q

what is the quaternary structure of collagen

A

three polypeptide chains would together to form a triple helix. these make microfibrils and fibrils and these are staggerd so there are no weak spots and furtheer strengthened by cross links between triple helical molecules

96
Q

state two properties of collagen which make it suitable for ligaments (bones to bones)

A

strong and insoluble (also flexible but does not stretch)

97
Q

what is it called when a graph levels off

A

reaches plateau

98
Q

What’s the location of starch

A

Plants as starch grains

99
Q

What’s the location of starch

A

Plants as starch grains

100
Q

How does the structure of starch relate to its function

A

Helix shape can compact to fit a lot of glucose into a small space. Branched structure increases surface area for rapid hydrolysis from starch to glucose . Additionally it’s insoluble so won’t affect water potential so water is not drawn into cells by osmosis and it itself cannot diffuse out of cells

101
Q

What is the structure of cellulose

A

Long straight chains , which run parallel with hydrogen bonds in between to form fibrils. monomers of beta glucose . cellulose molecules alternate .

102
Q

How does cellulose structure relate to its function

A

Many hydrogen bonds collectively provides strength to cell wall as many hydrogen bonds is difficult to break. cellulose can resist turgor pressure

103
Q

How does glycogen structure relate to its function

A

It’s very highly branched and therefore a lot of free ends and faster hydrolysis back to glucose , this is important because animals have a high metabolic rate and therefore need glucose for respiration and this can be rapidly converted to glucose as it’s highly branched additionally insoluble so won’t affect water protein tusk

104
Q

Where is glycogen found

A

Muscle and liver cells

105
Q

Describe two differences between the structure of a cellulose molecule and a glycogen molecule.

A

1.Cellulose is made up of β-glucose (monomers) and glycogen is made up of α-glucose (monomers);
2. Cellulose molecule has straight chain and glycogen is branched;

106
Q

Describe and explain two features of starch that make it a good storage molecule.

A

Insoluble (in water), so doesn’t affect water potential;
2. Branched / coiled / (α-)helix, so makes molecule compact;
OR
Branched / coiled / (α-)helix so can fit many (molecules) in
small area;
3. Polymer of (α-)glucose so provides glucose for respiration;
4. Branched / more ends for fast breakdown / enzyme action;
5. Large (molecule), so can’t cross the cell membrane

107
Q

What’s the tips for polysaccharide questions

A

Say about glucose being used for respiration and say they are polysaccharides

108
Q

What are the reducing sugars

A

Glucose , fructose , galactose , lactose and maltose

109
Q

What are the non reducing sugars

A

Sucrose

110
Q

Why would an animal use lipids instead of carbohydrates as an energy store

A

Lipids provide more than twice as much energy than carbohydrates when oxidised as they have a low mass to energy ratio making them good storage molecules as more energy can be stored in a smaller volume

111
Q

In the secondary structure protein how do the hydrogen bonds form

A

They form between the NH group and C=O group ( as water has been removed )

112
Q

Two proteins have the same number and type of amino acid but different tertiary structures, explain why

A

Different sequence of amino acids , so different primary structure and therefore hydrogen bonds , ionic and disulphide Bridges form in different places

113
Q

What is one difference between competitive and non competitive inhibitors

A

Non competitive , increase in substrate concentration does not change enzyme activity / high substrate conc does not overcome inhibition / maximum rate not retained

114
Q

Why does an unsaturated fatty acid increase the fluidity of the membrane

A

Increase in fluidity caused by increased unsaturated fatty acids as contain double bonds which cause kinks in fatty acid tail therefore phospholipids further apart

115
Q

Why does an unsaturated fatty acid increase the fluidity of the membrane

A

Increase in fluidity caused by increased unsaturated fatty acids as contain double bonds which cause kinks in fatty acid tail therefore phospholipids further apart

116
Q

What must you remember with the induced fit model

A

Active site changes shape not the substrate

117
Q

State how enzymes help reactions to proceed quickly at lower temps

A

Lower the activation energy

118
Q

why does maltose lower water potential

A

because it is soluble in water

Biology Alevel (19 decks)

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