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biological molecules Flashcards

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1
Q

what is hydrogen bonding? (biological molecules)

A
  • electrons are not evenly distributed & spend more time in one position
  • this region is more negatively charged than rest of the molecule
  • a molecule with uneven distribution of charge is polarised
  • negative region of one polarised molecule & positive region of another attract
  • a weak electrostatic bond is formed between the two
  • each bond is individually weak but are strong together
  • can alter physical properties of molecules
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2
Q

what is polymerisation? (biological molecules)

A
  • monomers joining together to create polymers
  • monomers are usually based on carbon
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3
Q

what is the basic subunit of a polysaccharide? (biological molecules)

A
  • a monosaccharide (e.g. glucose)
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4
Q

what is the basic subunit of a polynucleotide? (biological molecules)

A
  • mononucleotide subunits
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5
Q

what is the basic subunit of polypeptides? (biological molecules)

A
  • peptides that have amino acids as their basic subunit
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6
Q

what is a condensation reaction & what is an example? (biological molecules)

A
  • a reaction that produces water as a byproduct
  • e.g. the formation of a polypeptide from amino acids
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7
Q

what is a hydrolysis reaction & what is an example?

A
  • reactions that use water to split up molecules
  • e.g. polypeptides can be hydrolysed into amino acids
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8
Q

what is metabolism? (biological molecules)

A
  • all of the chemical processes that take place in living organisms
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9
Q

what are the rules for a peptide bond? (biological molecules)

A
  • carbon has 4 bonds
  • nitrogen has 3 bonds
  • water is removed when the amino & carboxyl groups join together
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10
Q

draw the structure of an amino acid & label the groups (biological molecules)

A

H H O
\ I //
N — C — C
/ I \
H R OH

  • H
    \
    N = amino group (NH2)
    /
    H
  • O
    //
    C = carboxyl group (COOH)
    \
    OH
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11
Q

draw a peptide bond (biological molecules)

A

H
I
N
/
C
II
O

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12
Q

draw a protein (biological molecules)

A

H R H O
\ / I II
H C N C H
\ / \ / \ / \ /
N C C O
I II / \
H O R H

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13
Q

what is a condensation reaction also known as? (biological molecules)

A
  • glycosidic bond
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14
Q

what is a disaccharide? (biological molecules)

A
  • 2 monosaccharides joined by a glycosidic bond
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15
Q

what are the three main monosaccharides? (biological molecules)

A
  • (alpha) glucose
  • fructose
  • galactose
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16
Q

what are the disaccharides & what monosaccharides are they made up of? (biological molecules)

A
  • glucose + glucose = maltose
  • glucose + fructose = sucrose
  • glucose + galactose = lactose
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17
Q

what is the basic monomer unit in a carbohydrate? (biological molecules)

A
  • sugar
  • also known as a saccharide
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18
Q

what is the general formula for monosaccharides? (biological molecules)

A
  • (CH2O)n
  • n can be any number between 3 & 7
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19
Q

what is a reducing sugar? (biological molecules)

A
  • a sugar that can donate electrons to another chemical
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20
Q

what is the method to test for a reducing sugar? (biological molecules)

A
  • add 2 cm cubed of the food sample to be tested to a test tube (is it is not already in liquid form then grind it up with water)
  • add an equal volume of Benedict’s reagent
  • heat the mixture in a water bath at 75˚C for 5 minutes
  • check colour of the solution to see the concentration of sugar
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21
Q

what do results from a reducing sugars test look like? (biological molecules)

A
  • blue = no sugar presence
  • green = very little sugar presence
  • yellow = low sugar presence
  • orange = medium sugar presence
  • brick red = high sugar presence
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22
Q

why is the Benedict’s test (reducing sugar) semi-quantitative? (biological molecules)

A
  • because the concentration of the reducing sugar present determines the colour change of the solution
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23
Q

what is the only structural difference between alpha & beta glucose? (biological molecules)

A
  • their hydroxyl groups are flipped
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24
Q

why is glucose a hexose sugar? (biological molecules)

A
  • because it has 6 carbons
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25
Q

draw the structure of alpha glucose (biological molecules)

A
  • refer to structures worksheet
  • OH should be on the bottom of final branch
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26
Q

draw the structure of beta glucose (biological molecules)

A
  • refer to structures sheet
  • OH should be on the top of the final branch
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27
Q

what is the bond between monosaccharides called? (biological molecules)

A
  • glycosidic bond
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28
Q

what is the test for a non-reducing sugar? (biological molecules)

A
  • carry out a normal Benedict’s test and achieve a negative result
  • hydrolyse the sample by adding 1cm cubed of hydrochloride acid & boiling for 2 - 3 minutes
  • neutralise solution by adding sodium hydrogen carbonate to make the solution alkaline (Benedict’s solution only work in alkaline conditions)
  • redo the Benedict’s test & a orange/red precipitate will form if it is positive
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29
Q

what is the test for starch? (biological molecules)

A
  • place 2 cm cubed of sample into a test tube or add two drops of sample into a depression on a spotting tile
  • add two drops if iodine solution & shake/stir
  • the presence of starch is indicated by a blue/black colouration
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30
Q

what are the two types of starch? (biological molecules)

A
  • amylose
  • amylopectin
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31
Q

where are amylose & amylopectin found? (biological molecules)

A
  • in plants
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32
Q

what is the function of amylose & amylopectin? (biological molecules)

A
  • main storage polysaccharide in plants (energy)
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33
Q

why are amylose & amylopectin suited for their job? (biological molecules)

A
  • insoluble so doesn’t affect water potential (water is not drawn into the cell via osmosis)
  • large so doesn’t diffuse out of cells
  • compact so a lot of it can be stored in a small space
  • (amylopectin) when hydrolysed it forms alpha glucose which is easily transported & used in respiration
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34
Q

what is the monomer for amylose? (biological molecules)

A
  • alpha glucose
  • 200 - 10 000 alpha glucose molecules
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35
Q

what is the monomer for amylopectin? (biological molecules)

A
  • alpha glucose
  • 100 000 - 200 000 alpha glucose molecules
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36
Q

what bonds are found in amylose? (biological molecules)

A
  • alpha -1,4 glycosidic bonds
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37
Q

what bonds are found in amylopectin? (biological molecules)

A
  • alpha - 1,4 glycosidic bonds
  • occasional alpha - 1,6 glycosidic bonds
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38
Q

what is the shape of amylose? (biological molecules)

A
  • tightly coiled helical structure
  • OH groups point inwards forming hydrogen bonds that hold the helix in place
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39
Q

what is the shape of amylopectin? (biological molecules)

A
  • branches linear chains
  • 20 glucose units per chain
  • branches are easily hydrolysed to release enzymes
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40
Q

where is glycogen found? (biological molecules)

A
  • in animals & bacteria
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41
Q

what is the function of glycogen? (biological molecules)

A
  • energy storage in animals
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42
Q

how is glycogen suited for its job? (biological molecules)

A
  • insoluble so does not draw water into the cell via osmosis & doesn’t diffuse out of cells
  • compact so lots of it can be stored in a small space
  • more highly branched than amylopectin so has more ends that can be acted on by enzymes (is rapidly broken down to form glucose monomers)
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43
Q

what is the monomer in glycogen? (biological molecules)

A
  • alpha (D) glucose
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44
Q

what bonds are found in glycogen? (biological molecules)

A
  • alpha -1,4 glycosidic bonds
  • alpha - 1,6 glycosidic bonds
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45
Q

what is the shape of glycogen? (biological molecules)

A
  • shorter chains that are more highly branched
  • humans have a higher metabolic rate than plants because they are more active so glycogen needs to be able to be hydrolysed quickly
46
Q

where is cellulose found? (biological molecules)

A
  • in plant cell walls
47
Q

what is the function of cellulose? (biological molecules)

A
  • provides rigidity to plant cells
  • prevents cell from bursting as water enters via osmosis
48
Q

how is cellulose suited for its job? (biological molecules)

A
  • made up of beta glucose so forms long unbranched chains
  • chain run parallel & are cross linked by hydrogen bonds which add strength
  • molecules are grouped to from microfibrils which also provide strength
49
Q

what is the monomer in cellulose? (biological molecules)

A
  • beta glucose
50
Q

what bonds are found in cellulose? (biological molecules)

A
  • beta - 1,4 glycosidic bonds
51
Q

what is the shape of cellulose? (biological molecules)

A
  • straight unbranched chains that run parallel
  • cross linked by hydrogen bonds
  • grouped into microfibrils
52
Q

what is the function of lipids? (biological molecules)

A
  • energy is stored in the body as fat
  • phospholipid bilayer in cell membranes
  • waterproofing (e.g. skin, feathers)
  • insulation to retain heat
  • protection of vital organs from damaging blows
53
Q

what type of reaction are triglycerides & phospholipids made from? (biological molecules)

A
  • condensation reaction
54
Q

how is the structure of a triglyceride related to its properties? (biological molecules)

A
  • good source of energy as have a high ratio of energy storing carbon-hydrogen bonds to carbon atoms
  • good storage molecules as have a low mass to energy ratio
  • insoluble in water (as they are large & non-polar) so don’t affect water potential
  • important source of water has they have a high ratio of hydrogen to oxygen atoms & release water when oxidised
55
Q

define the term hydrophobic (biological molecules)

A
  • repels water
56
Q

define the term hydrophilic (biological molecules)

A
  • attracted to water
57
Q

what part of a phospholipid is hydrophobic? (biological molecules)

A
  • the fatty acid ‘tail’
58
Q

what part of a phospholipid is hydrophilic? (biological molecules)

A
  • the phosphate group ‘head’
59
Q

what happens to phospholipids when they are placed in water? (biological molecules)

A
  • they position themselves so that the hydrophilic phosphate groups are as close to the water as possible & the hydrophobic fatty acids are as far away from the water as possible
60
Q

how is phospholipid structure suited to their properties? (biological molecules)

A
  • they are polar so create a hydrophobic barrier between the inside & outside of cells
  • the hydrophilic phosphate groups help to hold at the surface of the cell-surface membrane
  • allows them to form glycolipids by combining with carbohydrates in the cell-surface membrane (important for cell recognition)
61
Q

what is a saturated fatty acid? (biological molecules)

A
  • a fatty acid that has no carbon-carbon double bonds
62
Q

what is an unsaturated fatty acid? (biological molecules)

A
  • a fatty acid that has at least 1 carbon-carbon double bond
63
Q

why do unsaturated fatty acids have a lower melting point than saturated fatty acids? (biological molecules)

A
  • double bonds cause kinks in the fatty acids chain
  • this weakens the intermolecular bonds in the molecule
  • this causes them to have a lower melting point than
64
Q

name some properties of saturated fats (biological molecules)

A
  • origin = animals
  • solid at room temperature
  • no C=C bonds
  • chains are closely packaged
  • contain strong bonds
65
Q

name some properties of unsaturated fats (biological molecules)

A
  • origin = plants
  • liquid at room temperature
  • C=C bonds present
  • chains are not closely packaged together
  • contain weak bonds
66
Q

why are lipids insoluble in water? (biological molecules)

A
  • there are no spare oxygen molecules for water to form hydrogen bonds with
67
Q

give some similarities between triglycerides & phospholipids (biological molecules)

A
  • both are insoluble in water
  • both contain glycerol
  • both form ester bonds
  • both are a result of condensation reactions
  • both have fatty acid chains
  • can contain both saturated & unsaturated fatty acids
68
Q

give some differences between triglycerides & phospholipids (biological molecules)

A
  • phospholipids only have 2 fatty acid chains but triglycerides have 3
  • phospholipids have a phosphate group
  • phospholipids exist in cell membranes
  • triglycerides release 3 water molecules
  • triglycerides are the main water source in the human body
69
Q

give the method for testing for lipids (biological molecules)

A
  • take a completely dry & grease-free test tube
  • to 2 cm cubed of the sample being tested add 5cm cubed ethanol
  • shake the tube thoroughly to dissolve any lipid in the sample
  • add 5 cm cubed water & shake gently
  • a cloudy emulsion will indicate the presence of lipids
  • as a control repeat same procedures with water instead of a sample (final solution should remain clear)
70
Q

why does the test for lipids turn cloudy? (biological molecules)

A
  • any lipid is finely dispersed in the water to form an emulsion
  • light passing through emulsion is refracted at it passes from oil droplets to water droplets (this causes cloudiness)
71
Q

what type of reaction is the formation of a peptide bond? (biological molecules)

A
  • condensation reaction
72
Q

draw the structure of a dipeptide (biological molecules)

A
  • structure of amino acid x2
  • water should be removed
  • bond between C & N from two different amino acids
73
Q

is the R group involved in the formation of a dipeptide? (biological molecules)

A
  • no
74
Q

what is formed when many amino acids join together via condensation reaction? (biological molecules)

A
  • a polypeptide
75
Q

what groups in amino acids are slightly positively & negatively charged? (biological molecules)

A
  • slightly positive = amino groups
  • slightly negative = carboxyl groups
76
Q

what type of bond form when the slightly positive amino group & slightly negative carboxyl group of amino acids interacts? (biological molecules)

A
  • hydrogen bonds
77
Q

what do hydrogen bonds do in terms of polypeptides? (biological molecules)

A
  • they are weak but many of them form
  • this means that they can hold the polypeptide chain tightly together to form the structure of a protein
78
Q

what amino acids to disulphide bonds form with? (biological molecules)

A
  • form with specific types of amino acid
79
Q

describe the type of reaction that takes place to create a disulphide bond & the molecules that it occurs between (biological molecules)

A
  • an oxidation reaction occurs between the two sulfur containing groups
  • this forms a covalent bond
80
Q

are disulphide bonds stronger or weaker than hydrogen bonds? (biological molecules)

A
  • they are much stronger than hydrogen bonds
81
Q

what types of amino acids to ionic bonds form between? (biological molecules)

A
  • strongly positive & strongly negative amino acids
  • any carboxyl & amino groups that are not involved in forming peptide bonds
82
Q

what are ionic bonds between amino acids also known as? (biological molecules)

A
  • salt bridges
83
Q

are ionic bonds between amino acids strong & are they common? (biological molecules)

A
  • they are strong bonds
  • are not as common as other bonds
84
Q

what does the hydrolysis of a dipeptide produce? (biological molecules)

A
  • its two constituent amino acids
85
Q

in what process do amino acids join together? (biological molecules)

A
  • polymerisation
86
Q

what is a polypeptide? (biological molecules)

A
  • a chain of hundreds of amino acids that have joined together via polymerisation
87
Q

outline the primary protein structure (6 points) (biological molecules)

A
  • the sequence of amino acids in a polypeptide chain form the primary structure of any protein
  • there are limitless types of primary protein structure as polypeptides have many of the 20 naturally occurring amino acids joined in different sequences
  • these amino acid sequences are determined by DNA
  • primary structure also determines a protein’s ultimate shape & function
  • a change in a single amino acid can change a protein’s shape & stop it from carrying out its function
  • a single protein may consist of a single polypeptide chain but it is more common for a protein to be made up of a number of polypeptide chains
88
Q

outline the secondary protein structure (4 points) (biological molecules)

A
  • the linked amino acids that make up polypeptide have both a -NH & -C=O group on either side of every peptide bond
  • the hydrogen on the -NH group has an overall positive charge & the oxygen of the -C=O group has an overall negative charge
  • the two groups form hydrogen bonds
  • this causes the long polypeptide chain to be twisted into a 3D alpha helix shape or beta pleated sheets
89
Q

what is are the overall charged of the H in the -NH group & O in the -C=O group of amino acids? (biological molecules)

A
  • H = overall positive charge
  • O = overall negative charge
90
Q

outline the tertiary protein structure (3 points) (biological molecules)

A
  • the alpha helixes of secondary protein structures can be twisted even more to give the complex 3D structure of a protein
  • the tertiary structure is maintained by several different types of bond (disulphide, ionic, hydrogen)
  • where these bonds occur is dependent of the protein’s primary structure
91
Q

what 3 types of bond does the tertiary protein structure contain? (biological molecules)

A
  • disulphide bonds
  • ionic bonds
  • hydrogen bonds
92
Q

are the types of bond found in the tertiary protein structure easily broken? (biological molecules)

A
  • disulphide bonds are fairly strong & are therefore not easily broken
  • ionic bonds are easily broken by changes in pH
  • hydrogen bonds are numerous but easily broken
93
Q

outline the quaternary protein structure (3 points) (biological molecules)

A
  • arises from the combination of a number of different polypeptide chains & associated non-protein groups into a large & complex protein molecule
  • the polypeptide chains are linked in various ways
  • the sequence of amino acids determines the 3D shape
94
Q

describe the test from proteins (biological molecules)

A
  • biuret test
  • place a sample of the solution to be tested in a test tube & add an equal volume of sodium hydroxide at room temperature
  • add a few drops of very dilute (0.05%) copper (II) sulfate solution & mix gently
  • a purple colouration indicated the presence of a peptide bond & hence a protein
  • is no protein is present the solution remains blue
95
Q

name the three types of protein (biological molecules)

A
  • globular proteins
  • conjugated proteins
  • fibrous proteins
96
Q

what are globular proteins? Give an example (biological molecules)

A
  • proteins that fold into a 3D globular/spherical shape
  • they are water soluble because the hydrophilic R group is on the outside
  • most enzymes are globular proteins
  • e.g. insulin
97
Q

why are globular proteins water soluble? (biological molecules)

A
  • because the hydrophilic R group is on the outside
98
Q

what are conjugated proteins? Give examples (biological molecules)

A
  • globular proteins that contain a non-protein component called a prosthetic group
  • e.g. haemaglobin, catalase
99
Q

what are the non-protein components in conjugated proteins called? (biological molecules)

A
  • a prosthetic group
100
Q

what are fibrous proteins? Give an example (biological molecules)

A
  • regular sequences of amino acids that are repeated many times
  • they are insoluble & strong
  • they are structural & fairly unreactive
  • e.g. keratin, elastin, collagen
101
Q

what is the role of insulin? (biological molecules)

A
  • causes glucose to move from blood into cells
102
Q

outline the structure of insulin (4 things) (biological molecules)

A
  • has a combination of hydrogen bonds & disulphide bridges that cause its globular shape
  • weak interactions between subunits in the insulin polypeptide help to stabilise the overall quaternary structure
  • has two long polypeptide chains
  • two disulphide bridges covalently bond chains A (21 amino acids long) & B (30 amino acids long)
103
Q

what is the role of haemoglobin? (biological molecules)

A
  • transporting oxygen
104
Q

outline the protein structure of haemoglobin (5 things) (biological molecules)

A
  • contains four polypeptide chains that surround a central haem group
  • has two alpha & two beta polypeptide chains
  • alpha polypeptide = 141 amino acids long & beta polypeptide = 146 amino acids long
  • is also globular
  • can bind to protons & carbon dioxide
105
Q

what is the role of catalase? (biological molecules)

A
  • breaks down hydrogen peroxide into hydrogen & water
  • H2O2 is produced by certain reactions in cells & is lethal, so it is broken down into H2 & O2 (these are safe for the cells)
106
Q

outline the protein structure of catalase (4 things) (biological molecules)

A
  • is an intracellular enzyme
  • has 4 polypeptide chains
  • each polypeptide chain is 500 amino acids long
  • each polypeptide chain has its own haem group
107
Q

what is the role of keratin? (biological molecules)

A
  • provides structure to nails & hair
108
Q

outline the protein structure of keratin (4 things) (biological molecules)

A
  • has more than 20 known polypeptides
  • composed of 18 amino acids
  • can either be alpha keratin or beta keratin
  • poly peptide chains are arranged in parallel & anti parallel pleated sheets
109
Q

what is the role of elastin? (biological molecules)

A
  • allows tissues in the body to stretch out & shrink back
110
Q

outline the protein structure of elastin (5 things) (biological molecules)

A
  • repeated sequences of 3-9 amino acids
  • has a beta spiral secondary structure
  • has a triple helix structure (similar to collagen)
  • contains multiple polypeptide chains
  • does not have a tertiary structure
111
Q

what is the role of collagen? (biological molecules)

A
  • provides structural support to the extra cellular speakers between connective tissues
112
Q

outline the protein structure of collagen (biological molecules)

A
  • has three parallel polypeptide chains
  • has a triple helix structure
  • does not have a tertiary structure
  • each polypeptide chain is over 1400 amino acids long

biology 🧬 (3 decks)

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