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A Level Biology Paper 1 > Biological Molecules > Flashcards

Biological Molecules Flashcards

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1
Q

Monomer

A

Small molecules
Joins to other similar or identical monomers
To form larger complex molecules
Called polymers

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2
Q

Polymers

A

Large complex units
Consisting of repeating chains of 3 or more similar or identical monomers
Joined together by chemical bonds

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3
Q

Condensation reaction

A

Anabolic process
Making large molecules from smaller ones
New chemical bond joining molecules as a molecule of water is released

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4
Q

Hydrolysis reaction

A

Catabolic process
Breaks large molecules into small ones
Chemical bond broken as a molecule of water is added

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5
Q

What is the difference between chitin and other polysaccharides

A

Chitin is nitrogenous

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6
Q

How does amylose make starch adapted for its function

A 
Carbon 1:4 glycosidic bonds
Form long linear chains 
That coil into a helix
Compact
So good for storage
Can store a lot in a small space
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7
Q

What is starch

A

A carbohydrate of 2 polysaccharides of alpha glucose called amylose and amylopectin

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8
Q

How does amylopectin make starch adapted for its function

A 
Branched chain
Branches caused by carbon 1:4 and 1:6 glycosidic bonds
Large surface area
Rapid hydrolysis by enzymes
To release glucose for respiration
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9
Q

Starch adaptations

A

Insoluble so doesn’t affect the water potential of cell
Large molecule so doesn’t diffuse out of cell
Helical/compact so stores a lot in a small space
Branched so large surface area and rapid hydrolysis

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10
Q

How do glycogen and starch act as energy stores

A

Can be hydrolysed to glucose

Glucose using to release energy through respiration

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11
Q

Glycogen adaptations

A

Highly branched structure for large surface area for rapid hydrolysis by enzymes to release Glucose for respiration

Insoluble so doesn’t affect the water potential of cells

Large so doesn’t diffuse out of cells

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12
Q

What is cellulose

A

A beta glucose polysaccharide
Formed from condensation reactions to form long unbranched chains of beta glucose
Joined by beta 1:4 glycosidic bonds

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13
Q

Cellulose structure

A 
Long unrbanched chains
Joined by beta 1:4 glycosidic bonds
Every other molecule inverted 180°
To allow weak hydrogen bonds to form between straight chains
Making strong macrofibrills
Wound together to make cellulose fibres
Providing strength and support in plant cell walls
Resist turger pressure, osmotic pressure
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14
Q

Why can’t humans digest cellulose

A

Human digestive system cannot break down the beta 1:4 glycosidic linkage in cellulose
Since it requires a specific enzyme absent in humans

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15
Q

What is a triglyceride

A

Type of lipid
Made of one molecule of glycerol joined by ester bonds to 3 fatty acids
Not a polymer since not made of similar monomers

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16
Q

Where are triglycerides found

A

Waxy cuticle of plants and insects (waterproof)

Aquatic organisms (less dense than water so organisms can stay buoyant)

Blubber in whales/seals (thermal insulator conducts heat slowly and reduces heat loss)

Stored around delicate organs (for shock absorption to protect organs from internal damage)

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17
Q

Saturated fatty acid

A

Fatty acid with no double bonds/only single bonds between carbon atoms of the hydrocarbon chain
Maximum number of hydrogen and so chain lies flat/no kink

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18
Q

Unsaturated fatty acid

A

One or more double bonds between carbon atoms in the hydrocarbon chain of a fatty acid
Causing a kink in the chain and not the maximum number of hydrogens
Can’t pack together tightly

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19
Q

Saturated vs unsaturated fatty acids

A

Both have a hydrogen chain

Saturated fatty acids only have single bonds between carbons
Unsaturated have one or more double bonds between carbons

Saturated are fully saturated with hydrogen/have maximum number of hydrogen
Unsaturated not fully saturated with hydrogen and don’t have maximum number of hydrogens

Double bond causes a kink in the chain of unsaturated fatty acids but saturated lies flat

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20
Q

What lipids are solids at r.t.p

A

Saturated lipids
Single bonds means no kinks in hydrocarbon tail
So lie flat and can pack tightly together as solids

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21
Q

What lipids are liquid at r.t.p

A

Unsaturated lipids with one or more double bonds in fatty acid tail/hydrocarbon chain
Because the kink causes the chains to be unable to pack tightly together hence liquid
E.g oil

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22
Q

Phospholipid

A

A type of lipid
Consisting of a molecule of glycerol
Bonded to a phosphate group
And go two molecules of glycerol by ester bonds

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23
Q

Phospholipid function

A

Main component of cell membranes

Forming the phospholipid bilayer

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24
Q

Explain the structure and interaction of phospholipids

A

Phosphoglycerol head is hydrophilic because it is polar (-ve) and so attracts water
The fatty acids are hydrophobic and so repel water

In water they form small droplet called micelles
The hydrophobic tails orientate into the middle and the hydrophilic heads outwards towards the water

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25
Test for reducing sugars
Benedicts test Add 2cm³ benedicts solution to sample Heat to 95°C Colour change from blue to green/yellow/orange/red/brick red precipitate indicates presence of reducing sugar Stronger colour change means more reducing sugar present No colour change means no reducing sugar but may be a non reducing sugar
26
Test for non reducing sugars
Modified benedicts test Add 2cm³ benedicts solution to sample Heat to 95°C Colour change from blue to green/yellow/orange/red/brick red precipitate indicates presence of reducing sugar Stronger colour change means more reducing sugar present No colour change means no reducing sugar but may be a non reducing sugar Boil a fresh sample with dilute hydrochloric acid for a few minutes to hydrolyse glycosidic bonds Neutralise by adding small solid pieces of sodium hydrogen carbonate Repeat benedicts test Colour change (like a reducing sugar) means non reducing sugar is present Since the sucrose has been hydrolysed, it can react with the benedicts solution to give a positive result
27
Reducing sugars
``` Glucose Fructose Lactose Maltose Galactose ```
28
Non reducing sugars
Sucrose
29
Monosaccarides
Glucose Lactose Fructose
30
Disaccharides
Maltose (Glucose+Glucose) Sucrose (Glucose+Fructose) Galactose (Glucose+Galactose)
31
What elements do amino acids contain
Nitrogen Carbon Hydrogen Oxygen Some contain Sulphur
32
List the parts of an amino acid
``` Amino/amine group (NH2) Carboxylic acid group (COOH) Variable side chain (R) Hydrogen (H) All attached to centre carbon (alpha) ```
33
Explain the ends of an amino acid
N terminal ~ Amine group at the end | C terminal ~ Carboxyl group at the opposite end
34
How do amino acids bond
Via condensation reactions A molecule of water is released as a peptide bond produced Between the amine and carboxyl group The water is from the hydroxyl group of one amino acid and hydrogen from the amine of the other
35
What makes amino acids different
The different R groups (variable side chains)
36
Primary structure
``` Type Number Order Of amino acids in polypeptide chain Held together by peptide bonds (C-N) from condensation reactions ```
37
Secondary sturcture
The way the polypeptide chain folds into a beta pleated sheet Or coils into an alpha helix (H bond every 4th AA) Held together by weak hydrogen bonds
38
Tertiary structure
Further folding of peptide chain into a specific complex 3D structure R groups determine how it folds Held together by ionic bonds between ionised oppositely charged R grouos Hydrogen bonds between R groups Disulphide bridges between cysteine amino acids Final 3D structure for proteins made of one polypeptide
39
Quaternary structure
The way multiple polypeptide chains assemble themselves Held together by ionic, hydrogen and disulphide bonds Some van der waals Bonds between different polypeptide polypeptides Final 3D structure for proteins made of more than 1 polypeptides
40
Where do hydrogen bonds occur in proteins
Secondary structure Tertiary structure between H and O atom of different hydroxyl groups Quaternary between H and O atom of different polypeptides
41
Where do ionic bonds form in proteins
Tertiary Between opoisitely charged R groups of different amino acids Quaternary Between oppositely charged R groups of different polypeptide chains
42
Where do disulphide bridges form in proteins
Tertiary Between sulphur and hydrogen of adjacent variable R groups Usually cysteine amino acid Quaternary Between sulphur and hydrogen of suffering polypeptides amino acids R groups
43
What are van der waals and where are they found
Hydrophobic interactions | Between R groups that are both water hating
44
List 3 types of globular proteins
Transport proteins Enzymes Hormones
45
Examples of the globular transport proteins
Haemoglobin Carrier proteins Channel proteins
46
Examples of the globular protein enzymes
Lipase DNA polymerase ATP synthase
47
Examples of the globular protein hormones
Insulin Oestrogen Thyroxine
48
What is a globular protein
A type of protein that is spherical in shape | And soluble in water
49
3 types of structural protein
Collagen Keratin Silk
50
Explain the 3 types of structural protein
Collagen: Connective tissue e.g tendons/cartilage Keratin: Hair and nails Silk: In spiders webs
51
Structural protein
Type of protein that is strong, tough and insoluble in water Made of elongated or fibrous polypeptide chains 3 polypeptides
52
Why are enzymes only specific to one substrate
Enzymes have a specific 3D tertiary structure Which determines the shape of active site so it is only complementary to one substrate Therefore it can only form an Enzyme Substrate Complex with the one substrate complementary to its active site So can only catalyse one type of reaction
53
Test for proteins
Biuret test for proteins Detects peptide bonds Add equal volumes of sample and biuret solution to a test tube Colour change of blue to purple/violet = protein present No colour change, stays blue = no protein present
54
What are enzymes
Globular proteins That are biological catalysts Increase the rate of reaction by lowering the activation energy By stretching/distorting/weakening substrate bonds Not used up in the reaction and remain unchanged
55
Explain the lock an key model
Active site is rigid and does not change shape Substrate enters and binds to enzymes active site Substrate fits exactly into it - complementary Products are formed and no longer fit into active site So released Enzyme free to take part in another reaction
56
Explain the induced fit model
Substrate enters enzymes active site and binds to it to form enzyme substrate complex Binding induces a change in shape of active site Slight change in shape of 3D specific tertiary structure of active site causes stress/distorts substrates bonds Lowering the activation energy of reaction When substrate leaves, active site returns to original shape
57
Compare and contrast globular and fibrous proteins
Both have peptide, hydrogen and ionic bonds Same bank of 20 amino acids makes them up Globular round and spherical/Fibrous elongated Globular compact and folded/Fibrous strong and tough Globular soluble in water/Fibrous insoluble in water Globular involved in metabolic reactions/Fibrous involved in forming structures
58
How does temperature affect enzyme activity
T^ to optimum, so does rate Increases kinetic energy of substrates molecules More likely to successfully collide and react More ESC/second Beyond optimum Atoms within amino acids vibrate faster because more kinetic energy Causes weak hydrogen bonds and ionic bonds between neighbouring amino acids to break 3D tertiary structure changes and coukd alter active site No longer complementary to substrate No ESC Denatured and no longer catalyses any chemical reactions
59
How does denaturation occur
Beyond optimum Atoms within amino acids vibrate faster because more kinetic energy Causes weak hydrogen bonds and ionic bonds between neighbouring amino acids to break 3D tertiary structure changes and coukd alter active site No longer complementary to substrate No ESC Denatured and no longer catalyses any chemical reactions
60
How does pH affect enzyme activity
pH is a measure of hydrogen ion concentration If pH is changed from optimum (more acidic or more basic) The charge on the R groups of amino acids are altered Ionic bonds and weak hydrogen bonds are broken in tertiary structure Active site changes shape Substrate no longer complementary Less/no ESC formed Rate decreases Enzyme denatured
61
What is pH
Measure of hydrogen ion concentration
62
2 types of inhibitors
Competitive | Non competitive
63
What are inhibitors
Substances that decrease the rate of reaction by binding to enzyme at active site or allosteric site
64
What is a competitive inhibitor
Similar structure to substrate Binds to active site Prevents substrate from binding Fewer ESC/second Reduced rate Some product still formed if not all enzymes occupied Takes longer for all substrate to form products as opposed to no inhibition
65
What is a non competitive inhibitor
Binds to enzyme away from active site at allosteric site Causes a change in shape to enzyme and active site Substrate no longer complementary to active site Fewer ESC/second Fewer products
66
How does substrate concentration affect the rate of reaction
When substrate concentration is low so is the rate of reaction because there are few collisions So few ESC/second Substrate is the limiting factor As concentration increases, more active sites filled and more ESC/second (substrate still a limiting factor) Plateaus when all enzymes active sites are saturated and enzyme is new limiting factor Rate falls to 0 when all substrate converted into product
67
What 4 things can R groups be
Hydrophobic (repels water) Hydrophilic (attracts water) Negatively charged Positively charged
68
What is the optimum temperature
Temperature at which enzymes perform best at (fastest rate) | Maximum kinetic energy that can be applied to molecules before the hydrogen and ionic bonds start to break
69
Why can a protein be a substrate for 2 different enzymes
Different parts of protein have different amino acid sequence and different shapes Each enzymes active site has a specific shape And 2 different enzymes can be completely to different parts of the same protein
70
2 types of amino acids
Essential | Non essential
71
What are essential amino acids
Obtained from food and diet
72
What are non essential amino acids
Can be synthesised by the body
73
Example of essential amino acids
Valine Leucine Tryptophan
74
Examples of non essential amino acids
Glycine Tyrosine Serine
75
Where does the condensation reaction between 2 monosaccharides occur
Between the OH hydroxyl groups on C4 of one monosaccharide | And the OH hydroxyl groups on the C1 of another
76
Isomer
Same chemical formula | Different atom arrangement
77
Sources of glucose
Fruit and veg Honey Dairy
78
Sources of galactose
Fruit and veg | Dairy
79
Sources of fructose
Fruit and veg | Honey
80
Sources of maltose
Fermentation | Found in germinating seeds
81
Lactose sources
Found in milk of lactating female mammals
82
Sources of sucrose
Transported in the phloem of plants
83
Why are hydrogen bonds important in cellulose
Holds chain/molecules together to form cross links between chains called microfibrills Providing strength and rigidity to cellulose cell wall Weak hydrogen bonds provide strength in large numbers
84
Hydrolysis of disaccharide equation
C12H22O11 + H2O >>> C6H12O6 + C6H12O6
85
Condensation reaction for a disaccharide
C6H12O6 + C6H12O6 >>> C12H22O11 + H2O
86
Features of sugars and features of polysaccharides
Sugars: sweet, soluble, white crystalline Polysaccharides: Not sweet, insoluble
87
What is a precipitate
A solid suspended in a lipid
88
2 different reducing sugars of same concentration both produce red precipitates After 10 minutes one had twice as much precipitate Why
One solution was a disaccharide that was at the same concentration as the monosaccharide The enzyme hydrolysed the glycosidic bond in the disaccharide Releasing two monosaccharides The two monosaccharides are both reducing sugars So there is double the amount of reducing sugars Meaning double the precipitate in benedicts test
89
How would you determine the concentration or an unknown solution
Make up different known concentrations of 'x' Carry out the correct test on each sample Take readings of absorbance/transmission Using a colorimeter Plot readings to produce a graph called a calibration curve With concentration on x and absorbance on y Draw a line of best fit Read unknown sample absorbance/transmission from the calibration curve Read off corresponding concentration of solution
90
How can an acidic pH make proteib active
Change in ionic and hydrogen bonds/breaks them | So changes the tertiary structure

A Level Biology Paper 1 (16 decks)

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