BIOLOGICAL MOLECULES TOPIC 1 (CHAPTER 1)I Flashcards

Question

How is lactose formed ?

Answer 1

Glucose + galactose =/forms lactose

Answer 2

When the monosaccharides join, a molecule of water is removed and the reaction is therefore called a condensation reaction

Answer 3

A glycosidic bond ( a covalent bond formed between two monosaccharides)

Answer 4

C12H22O11 (glucose + glucose = maltose. And the chemical formula for glucose is C6H12O6). Maltose is a condensation reaction, so water (H20) is removed, so there are less H and O elements, therefore there are 22H not 24H and it is O11, not O12 in C12H22O11.

Answer 5

Water is added to a disaccharide , which breaks the glycosidic bond. This releases constituent monosaccharides. This addition of water to cause breakdown is called hydrolysis

Answer 6

Lactose + water ~~~> glucose + galactose

Answer 7

They are polymers, formed by combining together many monosaccharide molecules. (The monosaccharides are joined by glycosidic bonds that were formed by condensation reactions)

Answer 8

- are very large molecules, so are insoluble ~~~> this feature makes them good for storage - When they are hydrolysed, polysaccharides break down into disaccharides or monosaccharides - some polysaccharides, such as cellulose, are not used for storage but give structural support to plants cells

Answer 9

1. Place 2cm^3 of the sample being tested into a test tube 2. Add two drops of iodine solution and shake/stir 3. The presence of starch is indicated by a blue -black coloration (Colour changes from yellow to blue-black)

Answer 10

From yellow to blue-black

Answer 11

- Main role of starch is energy storage - found in plants -is an energy source in most animal diets - made up of chains of alpha glucose monosaccharides linked by glycosidic bonds that are formed by condensation reactions

Answer 12

-it is insoluble, doesn’t affect water potential, so water is not drawn into the cells by osmosis - being large and insoluble,does not diffuse out of cells - it is compact, so a lot of it can be stored in a small place - when starch is hydrolysed, it forms a-glucose, which is both easily transported and readily used in respiration - the branched form has many ends, each of which can be acted on by enzymes simultaneously meaning that glucose monomers are released very rapidly

Answer 13

Monomer: alpha glucose Found in : plants Advantage of coiling : The unbranched chain is wound into tight coils that make the molecule compact (The OH groups are pointing inwards + these form hydrogen bonds)

Answer 14

Monomer : alpha-glucose Found in : plants Advantage of branching : it has many ends which can be acted on by enzymes simultaneously, of which glucose molecules are released rapidly

Answer 15

Monomer : alpha glucose Found in : animals and bacteria, but never plants - in animals, it is stored as small granules mainly in the liver and muscles -Fat is the main storage molecule in animals

Answer 16

- insoluble, so does not affect osmosis -it does not diffuse out of cells -can be compact so a lot can be stored in a small space - highly branched so it can acted on simultaneously by enzymes for a quick release of glucose (important for respiration) - Very similar structure to starch but has shorter chains with more branches

Answer 17

Monomer : beta glucose Found in : plants Function : strengthens the cell Structure: rather than coiling like starch, cellulose has straight unbranched chains that run parallel to one another allowing hydrogen bonds to form cross- linkages between them.

Answer 18

- Each hydrogen bond is weak, but in large numbers, they are collectively strong. This makes it a great structural material - cellulose molecules group together to form micro fibrils, which in turn are arranged in parallel groups called fibrils

Answer 19

- insoluble in water - soluble in organic solvents such as alcohols and acetone - Main groups of lipids are triglycerides (fats and oils) and phospholipids

Answer 20

-Triglycerides (fats and oils) and phospholipids

Answer 21

Fats are solid at room temperature (in animals) Oils are liquid at room temperature (in plants)

Answer 22

- In the cell membranes - source of energy - waterproofing - insulation - protection

Answer 23

Phospholipids contribute to the flexibility of membranes ( cholesterol regulates the fluidity of the cell membrane ) and transfer of lipid - soluble substances across them

Answer 24

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

Answer 25

- lipids are insoluble on water, therefore useful as water proofing - both plants +insects have waxy, lipid cuticles that conserve water, while mammals produce an oily secretion from the sebaceous glands in the skin

Answer 26

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

Answer 27

- fat is often stored around delicate organs, like the kidney

Answer 28

- three (tri) fatty acids combined with glycerol (glyceride)

Answer 29

Each of the three fatty acid forms an ester bond with one glycerol in a condensation reaction. There is a removal of three molecules of water. Hydrolysis of a triglyceride therefore produces glycerol and three fatty acids

Answer 30

No double bonds between carbon atoms

Answer 31

A single double bond between carbon atoms (Double bonds cause the molecule to bend. They therefore cannot pack together so closely making them liquid at room temperature)

Answer 32

More than one double bond between carbon atoms

Answer 33

- they have a high ratio of energy-storing carbon-hydrogen bonds to carbon atoms and are therefore an excellent source of energy - they have a low mass to energy ratio, so they can store lots of energy in a small volume (benefits animals as it reduces the mass they have to carry as they move around) - non-polar molecules, so insoluble in water, so their storage does not affect water potential /osmosis in cells - they have a high ratio of hydrogen to oxygen atoms, so they release water when oxidised. This is why animals in desserts can use fat as a source of water

Answer 34

- similar to lipids except they have one less fatty acid, which is replaced with a phosphate molecule

Answer 35

Whereas fatty acid molecules repel water(hydrophobic), phosphate molecules attract water (hydrophilic). So phospholipid made up of two parts: 1. A hydrophilic ‘head’, which interacts with water (attracted to it) but not with fat 2. A hydrophobic ‘tail’, which orients itself away from water but mixes readily with fat

Answer 36

- they are polar molecules (hydrophilic head, hydrophobic tail) , means that in an aqueous environment, phospholipid molecules form a bilayer within cell surface membranes - hydrophobic barrier formed - The hydrophilic phosphate ‘heads’ of phospholipid molecules help to hold at the surface of the cell-surface membrane - The phospholipid structure allows them to form glycolipids by combining with carbohydrates within the cell-surface membrane. (Glycolipids important in cell recognition)

Answer 37

1. Take a completely dry and grease -free test tube 2. To 2cm^3 of the sample being tested, add 5cm^3 of ethanol 3. Shake the tube thoroughly to dissolve any lipid in the sample 4. Add 5cm^3 of water and shake gently 5. A milky - white emulsion indicates the presence of a lipid 6. As a control, repeat the procedures using water instead of the sample; the final solution should remain clear

Answer 38

Milky-white colour

Answer 39

Essential:are obtained from protein -rich foods Non-essential - they are synthesised naturally in your body

Answer 40

1. Enzymes 2. Antibodies 3. Transport proteins - located on the surface of cell membranes 4. Structural proteins

Answer 41

R R | H2N —————- C —————— COOH | H Amine group (H2N) - a basic group from which the amino part of the name amino acid is derived Carboxyl group (COOH) - an acidic group which gives the amino acid the acid part of its name Hydrogen atom (H) R - is the R group. It is 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

Answer 42

A chemical bond that is formed by joining the carboxyl group of one amino acid to the amino group of another

Answer 43

Hydrolysis reaction

Answer 44

Two amino acid monomers bond to form a dipeptide bond via a peptide bond.

Answer 45

A condensation reaction - the removal of a water molecule. (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)

Answer 46

Polymerisation - joining of many amino acids through condensation reactions A polypeptide is formed (the resulting chain of many hundreds of amino acids)

Answer 47

- sequence of amino acids joined by peptide bonds - bonds created via condensation reactions between the carboxyl and amino groups of adjacent amino acids - In the polypeptide chain, the sequence of amino acids is determined by the sequence of bases in DNA

Answer 48

-Hydrogen bonds form between the amino acids in the chain, and the polypeptide is no longer a straight chain. It starts to change the shape of the polypeptide as the chain folds. - Alpha helices and beta sheets are created by the folds

Answer 49

-The coiled or folded chain that we saw in the secondary structure is then folded and coiled even further - For proteins that are formed from just one polypeptide chain, this can be the final 3D protein structure. (e.g. enzymes) - In addition to hydrogen bonds, we start to see: Ionic bonds Disulfide bonds Hydrogen bonds

Answer 50

- formed between any carboxyl and amino groups that are not involved in forming peptide bonds. - They are weaker than disulfide bond and are easily broken by changes in pH [Attractions between negative and positive charges on different parts of the molecule ]

Answer 51

- these bonds form when two cysteine amino acids come together. Cysteine contains a sulfur atom which will bind to the sulfur atom of the other cysteine molecule [Disulfide bridges - are fairly strong and therefore not easily broken ]

Answer 52

- This is the final 3D structure for proteins made of more than one polypeptide chain, held together by hydrogen bonds - The chains come together and are folded to perform their special function. - E.g insulin, haemoglobin, collagen

Answer 53

- 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 (as the test solution needs to be alkaline) - Add a few drops of very dilute copper (II) sulfate solution (Biuret solution ) and mix gently - A purple coloration indicates the presence of peptide bonds and hence a protein. If no protein is present, the solution remains blue

Answer 54

Changes from blue to purple

Answer 55

They are biological catalysts of metabolic reactions

Answer 56

The minimum amount of energy needed to activate the reaction (as many reactions require an initial amount of energy to start)

Answer 57

Enzymes work by lowering the activation energy level. [In this way enzymes allow reactions to take place at a lower temperature than normal. ] This enables some metabolic processes to occur rapidly at the human body temperature of 37°C

Answer 58

Due to the tertiary structure of the protein

Answer 59

-A specific region of the enzyme is functional - active site -it is made up of relatively small number of amino acids - It forms a small depression within the much larger enzyme molecule

Answer 60

The molecule on which the enzyme acts. This fits neatly into this depression and forms an enzyme-substrate complex. [The substrate molecule is held within the active site by bonds that temporarily form between certain amino acids of the active site and groups on the substrate molecule]

Answer 61

-The lock and key theory suggested that the enzyme shape is a rigid structure - The induced fit model shows enzyme is flexible so not a rigid structure

Answer 62

1. The enzyme+ substrate enters the active site 2. The substrate binds to the active site, and the active site is complementary to the substrate, which suggests the enzyme has a rigid structure [enzyme/substrate complex] 3. Enzyme/product complex 4. Enzyme + product leaving the active site

Answer 63

- it is considered to be a rigid structure. However, scientists had observed that other molecules could bind to enzymes at sites other than the active site, so structure was not rigid but flexible.

Answer 64

- the active site forms as the enzyme and substrate interact. - A change in the environment of the enzyme leads to a change in the enzyme that forms the functional active site

Answer 65

- The enzyme is flexible and can mould itself around the substrate (like glove moulds itself to the shape of a hand) - The enzyme has a certain general shape, and alters in the presence of the substrate -As it changes it’s shape,the enzyme puts a strain on the substrate molecule - The strain distorts a particular bond/bonds in the substrate and consequently lowers the activation energy needed to break the bond - Any change in an enzyme’s environment is likely to change its shape ~~~> functional active site

Answer 66

Active site is not complementary to substrate. Shape of active site changes as substrate binds / enzyme- substrate complexes are formed

Answer 67

1. By measuring the release/presence of a product over time 3. By measuring the disappearance of a substrate over time

Answer 68

- At first there is a lot of substrate but no product - 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 -Becomes more difficult for the substrate molecules to come into contact with the enzyme molecules due to fewer substrate molecules - so takes longer for substrate molecules to be broken down by the enzyme , its rate of disappearance slows - The rate of reaction continues to slow until there is so little substrate that any further decrease in its concentration cannot be measured - The graphs flatten out because all the substrate has been used up ( so no new product can be produced)

Answer 69

Because all the substrate has been used up (no new product can be produced)

Answer 70

Gradient = change in y/ change in x

Answer 71

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

Answer 72

The increase in kinetic energy

Answer 73

-causes the hydrogen and other bonds in the enzyme, including its active site to change shape. -At first, the substrate fits less easily into this changed active site, slowing the rate of reaction

Answer 74

The shape of the enzyme changes too much (it is so disrupted) and is no longer complementary to the substrate. This is called denaturation. [ denaturation is a permanent change and once it has occurred, the enzyme does not function again]

Answer 75

- other proteins start to denature at 40°C -Need to produce more energy to heat ourselves up by another 3°C ~~> consuming more food - If you become ill, your temperature increases so there is a buffer to allow for this - Although higher body temperatures would increase the metabolic rate slightly, the advantages are offset by the additional energy (food) that would be needed to maintain the higher temperature

Answer 76

A measure of the concentration of H+ ions

Answer 77

pH= -log10 [H+]

Answer 78

H+ ions increase 10x

Answer 79

The OH- ions increase 10x

Answer 80

Use a buffer, a buffer withstands changes to pH

Answer 81

- A change in pH alters the charges on the amino acids that make up the active site of an enzyme. As a result, the substrate can no longer become attached to the active site and so the enzyme-substrate complex cannot be found - Depending on how significant the change in pH is,it may cause the bonds maintaining the enzyme’s tertiary structure to break. The active site therefore changes shape

Answer 82

The hydrogen and ionic bonds between -NH2 and -COOH groups of the polypeptides that make up the enzyme. [The change in H+ ions affects this bonding, causing the active site to change shape]

Answer 83

They are far more likely to reduce an enzyme’s activity than to denature it

Answer 84

You will achieve a higher likelihood of collision and the formation of enzyme- substrate complexes. [so, you only need a small concentration of enzymes for the reaction to happen. One enzyme can act upon millions of substrate molecules]

Answer 85

Adding more enzymes will not increase activity

Answer 86

An increase in enzyme concentration will have no effect on the rate of reaction. The rate of reaction will therefore stabilise at a constant level, meaning the graph will level off.

Answer 87

Low enzyme concentration: -There are too few enzyme molecules to allow all substrate molecules to find an active site at one time. -The rate of reaction is therefore only half the maximum possible for the number of substrate molecules available.

Answer 88

Intermediate enzyme concentration : - 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 doubled to its maximum because all active sites are filled

Answer 89

High enzyme concentration : - 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

Answer 90

The rate of reaction increases in proportion to the concentration of substrate

Answer 91

This is because at low substrate concentrations, the enzyme molecules have only a limited number of substrate molecules to collide with, and therefore the active sites of the enzymes are not working to full capacity

Answer 92

The active sites gradually become filled, until the point where all of them are working as fast as they can

Answer 93

Addition of more substrate will have no effect on the rate of reaction (there aren’t enough active sites available). - When there is an excess of substrate, the rate of reaction levels off

Answer 94

Low substrate concentration : - There are too few substrate molecules to occupy all the available active sites - The rate of reaction is therefore only half the maximum possible for the number of enzyme molecules available

Answer 95

Intermediate substrate concentration: - With twice as many substrate molecules avail, all the active sites are occupied at one time. -The rate of reaction has doubled to its maximum because all the active sites are filled

Answer 96

High substrate concentration : -The addition of further substrate molecules has no effect as all active sites are already occupied at one time. -There is no increase in the rate of reaction

Answer 97

Lactose = a type of sugar Lactase = an enzyme Lactose is a type of sugar found in milk and milk products. Our bodies produce an enzyme called lactase, which helps us digest lactose properly.

Answer 98

A molecule which reduces the rate of an enzyme controlled reaction

Answer 99

An inhibitor which binds to the active site of the enzyme, not the substrate. ( So substrate molecule unable to occupy the active site)

Answer 100

An inhibitor which binds to the enzyme at another site (allosteric site ) other than the active site

Answer 101

Penicillin

Answer 102

They must have a very similar structure

Answer 103

Less enzyme-substrate complexes can be formed, slowing the rate of enzymatic activity

Answer 104

The effect of the inhibitor is reduced

Answer 105

By adding extra substrate to increase the chance of enzyme-substrate collisions and therefore complexes

Answer 106

The inhibitor alters the shape of the enzyme and thus its active site in such a way that substrate molecules can no longer occupy it, and so the enzyme cannot function.

Answer 107

The substrate and the inhibitor are not competing at the same site

Answer 108

It will make no difference

Answer 109

- make maltose solutions of known/different concentrations (and carry out quantitive Benedict’s test on each) - use colorimeter to measure colour value of each solution and plot calibration curve - find concentration of sample from calibration curve