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biological molecules Flashcards

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1
Q

what are the three different ways that atoms can combine with each other

A
  1. covalent bonding
  2. ionic bonding
  3. hydrogen bonding
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2
Q

what are covalent bonds

A

covalent bonding is when atoms share a pair of electrons in their outer shells. As a result the outer shell of both atom is filled and a more stable compound is formed

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3
Q

what is ionic bonding

A

Ions with opposite charges attract one another. This electrostatic attraction is known as an ionic bond. Ionic bonds are weaker than covalent bonds

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4
Q

what is hydrogen bonding

A

electrons within a molecule are not evenly distributed but tend to spend more time at one position. This region is more negatively charged than the rest of the molecule.
A molecule with an uneven distribution of charge is said to be polarised - it is a polar molecule
The negative region of one polarised molecule and positively charged region of another attract each other.

Weak electrosatic bonds are formed between each other

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5
Q

what are macro molecules

A

very large molecules formed by smaller chemical structures ( e.g. monomers)

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6
Q

how are macro molecules formed

A

certain molecules (monomers) can be linked together to form long chains. These long chains are called polymers. The process they are formed is therefore called polymerisation

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7
Q

what are monomers usually based on

A

The monomers of a polymer are usually based on carbon

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8
Q

what polymers are industrially made

A

polyethene

polyester

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9
Q

what polymers occur naturally in living organisms

A

polysaccharides

polypeptides

polynucleotides

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10
Q

what is the basic - unit of a polysaccharide

A

monosaccharide or single sugar e.g. glucose

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11
Q

what is the basic sub unit of polynucleotides

A

mononucleotides

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12
Q

how are polypeptides formed

A

polypeptides are formed by linking together peptides that have amino acids as their basic sub- unit

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13
Q

what are condensation reactions

A

in the formation of polymers by polymerisation in organisms, each time a new sub unit is attached a molecule of water is formed.

Reactions that
produce produce water this way are termed condensation reactions

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14
Q

what is hydrolysis

A

if a molecule of water is produced every time a new sub unit is attached, polymers can be broken down through the addition of water.

Water molecules are used when breaking the bonds that link the sub - unit of a polymer, thereby splitting the molecule into its consituent parts.

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15
Q

what is metabolism

A

all chemical processes that take place in living organisms are collectively called the metabolism

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16
Q

what are carbohydrates

A

carbohydrates are carbon molecules (carbo) combined with water (hydrtae). Some carbohydrates molecules are small while others are large

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17
Q

what does the phrase “life based on carbon”

A

carbon atoms have an unusual feature . They can readily form bonds with other carbon atoms. This allows a sequence of carbon atoms of various lengths to be attached.

This permits a large number of different types and sizes of molecules all based on carbon.

Therefore the variety of life exists on earth are all based the versatile carbon atom

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18
Q

what are carbon containing molecules called

A

carbon containing molecules are known as organic molecules.

In living organisms, there are a relatively few other atoms that attach to carbon

this means life is therefore based on a small number of chemicals

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19
Q

what are monomers

A

Many organic molecules are made up of a chain of individual molecules. Each of the individual molecules that make up these chains is given the general name monomer

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20
Q

name some examples of monomers

A

monosaccharides
amino acids
nucleotides

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21
Q

name some examples of polymers

A

carbohydrates

protein

( these polymers are based on a surprisingly small number of atoms - carbon , hydrogen, oxygen, nitrogen|)

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22
Q

what is the basic monomer unit for carbohydrates

A

in carbohydrates, the basic monomer unit is sugar, otherwise known as a saccharide

a single monomer is a monosaccharide

a pair can combine to form a disaccharide

a large number of them chemically combined together to form polysaccharides

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23
Q

what are monosaccharides

A

monosaccharides are sweet tasting, soluble substances that have the general formula (CH2O)n where n can be any number between 3 to 7

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24
Q

what are some examples of monosaccharides

A

glucose

galactose

fructose

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25
Q

what is the structure of glucose

A

glucose is a hexose (6 - carbon) sugar

formula (C6H12O6)

atoms of carbon, hydrogen and oxygen can be arranged in many different ways
e.g.glucose has two isomers
alpha glucose and beta glucose

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26
Q

what are reducing sugars

A

reduction is a chemical reaction involving the gain of electrons or hydrogen.
A reducing sugar is therefore a sugar that can donate electrons to another chemical
(it can reduce other chemicals).

We can use this quality to identify if sugars are reducing using Benedict’s reagent

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27
Q

what are some examples of reducing sugars

A

monosaccharides and disaccharides (e.g. maltose)

are reducing sugars

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28
Q

how do we test for reducing sugars

A

we use the Benedict’s test

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29
Q

what chemical do we use in the Benedict’s test

A

Benedict’s reagent

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30
Q

what is Benedict’s reagent

A

Benedict’s reagent is an alkaline solution of copper (II) sulfate. When a reducing sugar is heated with Benedict’s reagent it forms an insoluble red percipitate of copper (I) oxide

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31
Q

how do we carry out the Benedict’s test

A

Add 2cm3 of food sample to be tested to a test tube. If the sample is not already in liquid form, grind it up in water

Add an equal volume of Benedict’s reagent to the test tube

Heat the mixture in a gently boiling tube for five minutes and wait for colour change

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32
Q

what is the relationship between the concentration of reducing sugar and the colour of the solution and the precipitate

A

blue (none)

green (very low)

yellow (low)

orange (medium)

red (high)

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33
Q

what are some disaccharides

A

-glucose joined to glucose forms maltose

glucose joined to fructose forms sucrose

glucose joined to galactose forms lactose

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34
Q

what happens when a monosaccharide joins together

A

when a monosaccharide join, a molecule of water is removed and the reaction is therefore called a condensation

The bond formed is called a glycocidic bond

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35
Q

what happens when water is added to a disaccharide

A

when water is added to a disaccharide it breaks down (under suitable conditions) releasing the consituent monosaccharides. This is called hydrolysis (addition of water that causes breakdown)

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36
Q

what are non reducing sugars

A 
some disaccharides (e.g. sucrose) are known as non - reducing sugars 
This is because they do not change the colour of Benedict's reagent when heated with it
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37
Q

how do we test for non reducing sugars

A

To test for non reducing sugars we must hydrolyse it into its monosaccharides components by hydrolysis

If the sample is not in liquid form it must be ground up in water first

method:
Add 2cm3 of the food sample being tested to 2cm3 of Benedict’s reagent in a test tube and filter

place test tube in a gently boiling water bath for 5 mins. If the Benedict’s regent does not change colour (solution remains blue) , then a reducing sugar is not present

Add another 2cm3 of the food sample to 2cm3 of hydrochloric acid in a test tube and place the test tube in a gently boiling water bath for 5 mins. The dilute hydrochloric acid will hydrolyse any disaccharide present into its consituent monosaccharide

Slowly add sodium hydrogencarbonate solution to the test tube in order to neutralise the hydrochloric acid. Test with pH paper to check that the solution is alkaline

Re- test the solution by heating with 2cm3 of Benedict’s reagent in a gently boiling water bath for 5 mins

if non- reducing sugar was present in the original sample the reagent should turn orange - brown. This is due to the reducing sugars that were produced from the hydrolysis of the non - reducing sugar

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38
Q

what are polysaccharides

A

polysaccharides are polymers formed by combining together many monosaccharide molecules

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39
Q

what are some features of polysaccharides

A

very large molecules

they are insoluble molecules. This feature makes them suitable for storage

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40
Q

what happens when polysaccharides are hydrolysed

A

they are broken down into disaccharides/monosaccharides

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41
Q

name some polysaccharides

A

starch

cellulose

glycogen

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42
Q

what is starch and where is it stored

A

starch is a polysaccharide that is found in many parts of plants in the form of small grains

especially large amount occur in seed and storage organs (potato tubers)

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43
Q

how is starch formed

A

starch is formed by joining 200 and 100000 together alpha glucose molecules by glycosidic bonds in a series of condensation reaction

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44
Q

how do we test for starch

A

starch is easily detected by its ability to change colour of the iodine in potassium iodide solution from yellow to blue black

method
Place 2cm3 of the sample being tested into a test tube (or add two drops of the sample into a depression on a spotting tile)

add two drops of iodine solution and shake or stir

the presence of starch is indicated by a blue black coloration

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45
Q

what makes larger molecules different from one another

A

the various different ways they combine with the smaller molecules to form them

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46
Q

why is starch so important

A

it forms an important component of food and is the major energy source in most diets

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47
Q

what is the structure of starch

A

made up of chains of alpha glucose

the chains may be branched or unbranded

unbranded chains are wound into a tight coils that makes the molecules compact

The OH groups are pointing inwards and these form hydrogen bonds that hold the helix in place

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48
Q

how does the structure of starch relate to the function

A

insoluble
therefore water is not drawn into the cells by osmosis

large and insoluble
does not diffuse out of the cells

compact
a lot of it can be stored into a small space

when hydrolysed it forms alpha glucose which is both easily transported and readily used in respiration

branched form has many ends, each of which can be acted on by enzymes simultaneously meaning that glucose are released very rapidly (for respiration)

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49
Q

where is starch found

A

starch is never found in animal cells

so it is found in plant cells

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50
Q

where is glycogen found

A

glycogen is found in animal and bacteria cells but never plant cells

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51
Q

what is the structure of glycogen

A

the structure of glycogen is similar to starch but has many shorter chains and is highly branched

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52
Q

what is the function of glycogen

A

major carbohydrate storage of animals

the mass of carbohydrates is relatively small because fat is the main storage in animals

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53
Q

where is glycogen stored

A

in animals it is stored as small granules mainly in the muscles and liver

54
Q

how does glycogen structure relate to its structure

A

similar to starch except it is more highly branched than starch. Therefore it has more ends that can be acted on simultaneously by enzymes. This means more rapidly hydrolysed to form glucose monomers which are used in respiration.

This is important to animals which have a higher metabolic rate and therefore respiratory rate than plants because they are more active

55
Q

how is cellulose different from glycogen and starch

A

cellulose is made from beta glucose. This produces a fundamental difference in the structure and function of the polysaccharide
e.g. rather than forming a coiled chain like starch, cellulose has straight, unbranded chains

56
Q

what is the structure of cellulose

A

has straight unbranded chains. These run parallel to one another, allowing hydrogen bonds to form cross linkages between adjacent chains

the OH group occur on both sides of the molecule so it can form hydrogen bonds with other chains on both sides

57
Q

what do the hydrogen bonds in cellulose do

A

while each individual hydrogen bond adds very little to the strength of the molecule, the sheer overall number of them makes considerable contribution to strengthening cellulose

This contributes to strengthening cellulose

58
Q

what is the function of cellulose

A

cellulose molecules group together to form microfibrils which in turn are arranged in parallel groups called fibres

cellulose is a major component of plant cell walls and provides rigidity to the plant cell.

The cellulose cell wall also prevents the cell from bursting as water enters by osmosis

59
Q

how does the cell wall prevent the cell from bursting when the water enters it by osmosis

A

it does this by exerting an inward pressure that stops any further influx of water. As a result, living plant cells are turgid and push against one another, making woody parts of the plant semi rigid

This is especially important in maintaining stems and leaves in a turgid state so that they can provide the maximum surface area for photosynthesis

60
Q

what is the relation between the structure and function of cellulose

A

chains run parallel with each other and are crossed linked by hydrogen bonds which add collective strength

these molecules are grouped to form fibres all of which adds more strength

61
Q

what are lipids

A

lipids are varied group of substances that share certain characteristics

62
Q

what are some characteristics that all lipids share

A

they contain carbon, hydrogen and oxygen

they are insoluble

They are soluble in organic solvents such as alcohols and acetone

Fats are solid at room temp (10-20 C) whereas oils are liquid

63
Q

what is the main group for lipids

A

the main groups of lipids are triglycerides (fats and oils) and phospholipids

64
Q

what are some of the roles of lipids

A

lipids have many roles :

IN MEMBRANES

SOURCE OF ENERGY

WATERPROOFING

INSULATION

PROTECTION

65
Q

what is the lipids role in the cell membrane

A

IN MEMBRANES
one role of lipids is in the cell membranes (cell - surface membranes and membranes around organelles).
Phospholidpids contribute to the flexibility of membranes and the transfer lipid soluble substance across them

66
Q

how are lipids a good source of energy

A

SOURCE OF ENERGY

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

67
Q

how are lipids good at waterproofing

A

WATERPROOFING
lipids are insoluble in water and therefore useful as a waterproofing. Both plants and insects have waxy , cuticles that conserve water, while mammals only produce oily secretion from the sebaceous glands in the skin

68
Q

how are lipids good at insulation

A

fats are slow conductors of heat and when stored beneath the body surface help to retain body heat. They also act as electrical insulators in the myelin sheath around the nerve cells

69
Q

how are lipids good for protection

A

fat is often stored around delicate organs, such as the kidney

70
Q

what are triglycerides

A

triglycerides are a type of lipids

three (tri) fatty acids

combined with glycerol (glyceride)

71
Q

how are triglycerides formed

A

in triglycerides, each fatty acids forms an ester bond with glycerol in condensation reaction. Three water molecules are produced. The fatty acids may not all be identical

(hydrolysis of this lipid produces glycerol and three fatty acids)

72
Q

what makes certain triglycerides different from one another

different properties

A

as the glycerol molecule in all triglycerides are the same, the difference in the properties of different fats and oils come form variations in the fatty acids

73
Q

how many fatty acids are there

A

over 70 different fatty acids

all have a carboxyl (-COOH-) group with a hydrocarbon chain attached to it

74
Q

what does the terms saturated, mono unsaturated and polyunsaturated

A

If the hydrogen chain has no carbon- carbon bonds, the fatty acids is then described as saturated (all the carbon atoms are linked to the maximum possible number of hydrogen atoms)

a single double bond is mono- unsaturated

more than one double is present, it is polyunsaturated

75
Q

how does the structure relate to the properties of triglycerides

A

triglycerides have a high ratio of energy storing carbon - hydrogen bonds to carbon atoms therefore they are an excellent source of energy

low mass to energy ratio, making them good storage molecules . This is especially beneficial to animals as it reduces the mass they have to carry as they move around

large, non polar molecules, triglycerides are insoluble on water. This means their storage does not affect osmosis in cells or the water potential of them

76
Q

what are phospolipids

A

phospholipids are similar to triglycerides except that one of the fatty acid molecules is replaced by a phosphate molecule

77
Q

what are the the two parts phospholipids are made up of

A

whereas fatty acid molecules repel water (are hydrophobic) phosphate molecules attract water (are hydrophilic)

therefore a phospholipid is made of two parts:
1. a hydrophilic head interacts with water (is attracted to it) but not with fat

2.a hydrophilic tail that orients itself away from water but mixes with fat

78
Q

what are molecules that have two ends called

A

we say that the molecule is polar

79
Q

what happens when these polar phospholipid molecules are placed in water

A

they position themselves so that the hydrophilic heads are close to the water as possible and the hydrophobic tails are as far from the water as possible

80
Q

how does the structure of phospholipids relate to their properties

A

phospholipids are polar molecules . This means that in an aqueous environment, phospholipids molecules form a bilayer within cell surfaced membranes . As a result, a hydrophobic barrier is formed between the inside and outside of a cell

the hydrophilic phosphate heads of phospholipid molecules help to hold the surface of cell- surface membrane

phospholipid structure allows them to form glycolipids by combining with carbohydrates within the cell surface membrane. These glycolipids are important in cell recognition

81
Q

how do we test for lipids

A

take a completely dry and grease free test tube

take 2cm3 of the sample being tested, add 5cm3 of ethanol

  1. shake the test tube thoroughly to dissolve any lipids in the sample
  2. Add 5cm3 of water and shake gently
  3. a milky - white emulsion indicates the presence of a lipid
  4. as a control, repeat the procedures using water instead of the sample; the final solution should remain clear
82
Q

what are proteins

A

are large molecules that are made up of chains of polypeptides. Polypeptides basic sub unit are amino acids

83
Q

what are amino acids

A

amino acids are the basic monomer units which combine to make up a polymer called a polypeptide. Polypeptides can combine to form proteins

84
Q

how many amino acids have been identified

A

about 100 amino acids have been identified, of which 20 occur naturally in proteins

  • the fact that the same 20 amino acids in all living organisms provides indirect evidence for evolution
85
Q

what is the structure for amino acids

A

all of these groups are attached to a single carbon atom

amino group (-NH2) from which the amino part of the name amino acid is derived

the carboxyl group (-COOH) an acidic group which gives the amino acid the acid of its name

hydrogen atom (-H)

R (side) group - a variety of different chemical groups. Each amino acid has a different R group. These 20 naturally occurring amino acids differ only in their R (side) group

86
Q

what is the primary structure of protiens

A

the primary structure is the sequence of amino acids found in a polypeptide chain.

This process happens through a series of condensation reactions where many amino acid monomers join together to form a polypeptide chain.

87
Q

what determines the sequence of amino acids in a polypeptide chain

A

this sequence is determined by DNA

88
Q

how many different types of primary protein structures are there

A

as polypeptides have many (usually hundreds) of the 20 naturally occurring amino acids joined in different sequences, it follows that there is an almost limitless number of possible combinations, and therefore types of primary protein structure

89
Q

what determines the shape of the protein and its function

A

the primary structure of the amino acid determines the proteins ultimate shape and therefore its function

90
Q

what happens if the primary structure of the protein changes

A

a change in just a single amino acid in the primary sequence can lead to a change in the shape of the protein and may stop it carrying out its function less well, or differently

91
Q

what is the secondary structure of proteins

A

the secondary structure of a protein is the shape which the polypeptide chain forms as a result of hydrogen bonding. This shape is a spiral known as a helix (alpha helix)

92
Q

why does the long polypeptide chain twist

A

The linked amino acids that make up a polypeptide possess both -NH and -C=O groups on either side of every peptide bond.
The hydrogen of the -NH group has an overall positive charge while the O of the -C=O group has an overall negative charge. These two groups therefore readily form weak bonds called hydrogen bonds. This causes the long polypeptide chain to be twisted into a 3-D shape - alpha helix.

93
Q

what is the tertiary structure of a protein

A

the tertiary structure of a protein is the bending and twisting of the polypeptide helix into a compact
structure

The alpha-helices of the secondary protein structure can be twisted and folded even more to give the complex and often specific 3-D structure of each protein. This structure is maintained by a number of different bonds.
Where these bonds occur depends on the primary structure of the protein

94
Q

what are the bonds that help maintain the tertiary structure of the protein

A

disulfide bridges - fairly strong and are not easily broken

ionic bonds - normally forms between the carboxyl groups and amino groups that are not involved in forming peptide bonds.
Are weaker than disulfide bridges and are easily broken by changing the pH

hydrogen bonds - numerous but easily broken

95
Q

why is the 3D shape of the protein important

A

It is the 3D shape of a protein that is important when it comes to how it functions.
It makes each protein distinctive and allows it to recognise and be recognised by other molecules.

It can then interact with these molecules in a very specific way

96
Q

what is the quaternary structure of a protein

A

the quaternary structure is the combination of a number of different polypeptide chains and associated non - protein (prosthetic) groups into a large, complex protein e.g. haemoglobin

large proteins often form complex molecules containing a number of individual polypeptide chains that are linked in various ways. It may also contain prosthetic groups associated with the molecules e.g. iron-containing haem group in haemoglobin

97
Q

what determines the 3D shape of the protein

A

it is the sequence of the amino acids in the primary structure that determines the 3D shape in the first place

98
Q

how do peptide bonds form

A

through a series of condensation reactions which is essentially the removal of water.

The water is made by combining an -OH from the carboxyl group of one amino acid with an -H from the amino group of another amino acid.
The two amino acids then become linked by a new peptide bond between the carbon atom of one amino acid and the nitrogen atom of the other

99
Q

how can this peptide bond be broken

A

the peptide group can be broken by the addition of water (hydrolysis).
The dipeptide would be broken into its two constituent amino acids

100
Q

how do we test for proteins

A

the most reliable test for proteins is the Biuret test. The biuret test detects peptide bonds

METHOD:
1. place a sample of the solution to be tested in a test tube and add an equal volume of sodium hydroxide solution at room temperature

  1. add a few drops of very dilute (0.05%) copper (II) sulfate solution and mix gently
  2. a purple colouration indicates the presence of peptide bonds and hence a protein. If no protein is present, the solution remains blue
101
Q

what are enzymes

A

enzymes are globular proteins that act as catalyst

They alter the rate of a chemical reaction without undergoing permanent changes themselves.

They can be reused repeatedly and are therefore effective in small amounts

102
Q

how do enzymes alter the rate of a chemical reaction

A

enzymes lower the activation energy of an reaction .
Therefore enzymes allow the reaction to take place at a lower temperature than normal

This enables some metabolic processes to occur rapidly at the human temperature 37C which is relatively low in terms of chemical reactions

103
Q

what must happen in order for a reaction to happen

A

for reactions to happen naturally a number of conditions must be satisfied:

  1. molecules must collide with sufficient energy to alter the arrangement of their atoms
  2. free energy of the products must be less than that of the substrates (exothermic reaction)
  3. many reactions require an initial amount of energy to start. This energy is the minimum amount of energy required to start the reaction (activation energy)
104
Q

what is the activation energy

A

the activation energy is like an energy barrier, which must initially be overcome before the reaction can proceed

105
Q

what would happen if our body didn’t have enzymes

A

without enzymes, reactions happening in our body would proceed too slowly to sustain life as we know it

106
Q

what is the structure of an enzyme

A

enzymes being globular proteins, have a specific 3D shape that is the result of amino acids

enzymes also have a specific region known as the active site

107
Q

what is the structure of the active site

A

the active site is made up of a relatively small number of amino acids

The active site forms a small depression within the much larger enzyme molecule

108
Q

what happens at the active site

A

the substrate molecule neatly fits into this depression (active site) and forms an enzyme- substrate molecule ( E-S complex)

The substrate is held within the active site by the bonds temporarily formed between amino acids of the active site and groups on the substrate molecule

109
Q

what is the induced fit model

A

induced fit model of enzyme action proposes that the active site forms as the enzyme and substrate interact ( a change in the environment of the enzyme)

In other words, the enzyme is flexible and can mould itself around the substrate in the way that a glove mould itself to the shape of the hand e.g. enzymes has general shape, like a glove, but alters in presence of the substrate

110
Q

what happens as the enzyme changes shape

A

as it changes shape, the enzyme puts a strain on the substrate molecule.

the strain distorts a particular bond or bonds in the substrate and consequently lowers the activation energy needed to break the bond

111
Q

what happens to the enzyme when the environment changes

A

any change in the enzyme’s environment will result to change in its shape.

The very act of colliding with its substrate is a change in its environment so its shape changes - induced fit

112
Q

what is one limitation of the lock and key model

A

the enzyme, like a lock, is considered to be rigid structure.

This is not the case as an enzyme shape can be altered. In other words, its structure was not rigid but flexible.

Scientists therefore modified the lock and key model to the induced fit model

113
Q

what must happen in order for enzymes to work

A

for enzymes to work it must:

  • come into physical contact with its substrate
  • have an active site which fits the substrate

almost all factors that influence the rate at which enzyme works do so affecting on or both of the above

114
Q

how do we measure enzyme catalysed reactions

A

to measure the progress of an enzyme - catalysed reaction we usually measure its time - course

that is how long it takes for a particular event to run its course

The changes most frequently measured are:
-formation of the products of the reaction

-disappearance of the substrate

115
Q

describe the shape of a graph that follows the formation of a products in a reaction/ disappearance of a substrate

A

at first there is a lot of substrate but no product

it is very easy for substrates to come into contact with empty active sites on the enzyme molecules

all enzyme active sites are filled at any given moment and the substrate is rapidly broken down into its products. The amount of substrate decreases as it is broken down, resulting in an increase in the amount of product

as the reaction proceeds, there is less and less substrate and more product

It becomes more difficult for the substrate to come into contact with the enzyme molecules because there are fewer substrate molecules and also the product molecules may “ get in the way” of substrate molecules and prevent them reaching and active site

Therefore it takes longer for the substrate molecule to be broken down by the enzyme and so it’s rate of disappearance slows down and consequently the rate of the formation of products slows down also slows

rate of reaction continues to slow until there is so little substrate that any further decrease in its concentration cannot be measured

the graph flattens out because the substrate has been used up and so little substrate that any further decrease in its concentration cannot be measured

OR
the graph flattens out because all the substrate has been used up and so no product can product can be produced

116
Q

what is the effect of temperature on enzyme action

A

the rise in temp increases kinetic energy of molecules
As a result of, the molecules move around more rapidly and collide with each other more often

In enzyme catalysed reactions, this means that the enzyme and substrate molecules come together more often in a given time

117
Q

how would the effect of temperature look like on a graph

A

on a graph, the effect of temperature gives a rising curve

118
Q

what happens to the enzymes as the temperature begins to rise

A

on rising temperature also begins to cause the hydrogen and other binds in the enzyme molecule to break down

This results in the enzyme, including its active site changing shape

For many humans this begin to happen at temperatures around 45C

119
Q

what happens when the enzyme and the active site changes shape

A

at first, the substrate fits less easily into this changed active site, slowing the rate of the reaction.

120
Q

what does it mean when we say an enzyme has denatured

A

at some point, usually around 60C, the enzyme is so disrupted that it stops working altogether.

The enzyme is said to have denatured which is a permanent change and once occurred, the enzyme does not function

121
Q

how would the graph look when an enzyme has denatured

A

their will be a falling curve on the graph

122
Q

why has our body evolve to have a temperature of 37C

A

the optimum temperature differs from enzyme to enzyme. Our body temperature has evolved to 37C this may be related to the following:

  • although higher body temperatures would increase the metabolic rate slightly, the advantages are offset by the additional energy (found) that would be needed to maintain the higher temperature
  • other proteins, apart from enzymes, may denature at higher temps
  • at higher temps, any further rise in the temp e.g. during illness, might denature the enzymes
123
Q

why do different organisms have different body temperatures

A

different animals have different body temps,

e.g. 40C for birds because they have a high metabolic rate for the higher energy requirement of flight

124
Q

what is the pH of a solution

A

the pH of a solution is a measure of its hydrogen ion

125
Q

what happens to an enzyme when the pH moves away from optimum

A

it affects the rate of enzyme action

An increase or decrease in pH reduces the rate of enzyme action

If the pH is more extreme, then beyond a certain pH,, the enzyme becomes denatured

126
Q

how does the pH affect enzymes

A

a change in pH alters the charges on the amino acids that make up the active site of an enzyme.
This causes the substrate to no longer become attached to the active site and the enzyme - substrate complex cannot be formed

  • depending on how significant the change in pH is, it may cause the bonds maintaining the enzymes tertiary structure to break causing the active site to change shape
127
Q

what determines the arrangement of the active site

A

the arrangement of the active site is partly determined by the hydrogen and ionic bonds between -NH2 and COOH groups of the polypeptide that make up the enzyme

The H+ ions ( from the changing of the pH) affects this bonding, causing the active site to change shape

128
Q

what happens to a reaction when there is a low enzyme concentration

A

there are too few enzyme molecules to allow substrate molecules to find an empty active site. The rate of the reaction is therefore only half the maximum possible for the number of substrate molecules available

129
Q

what happens to a reaction when there is an intermediate enzyme concentration

A

with twice as many enzyme molecules available, all the substrate molecules can occupy an active site at the same time .

The rate of reaction has doubles to it’s maximum because all active sites are filled

130
Q

what happens to the reaction when there is a high enzyme concentration

A

the addition of further enzyme molecules has no effect as there are already enough active sites to accommodate all the available substrate molecules

There is no increase in the rate of reaction

biology a levels (9 decks)

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