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Biological Molecules Flashcards

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1
Q

Describe what a mole is and what is meant by a molar solution

A

A mole is unit for measuring the amount of a substance

A molar solution contains one mole of a solute in one litre of solution

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2
Q

Explain bonding and the formation of molecules

A

Atoms combine to form molecules in three ways:
Covalent bonding - atoms share a pair of electrons from their outer shell to become more stable
Ionic bonding - Ions with opposite charges attract, this is an electrostatic attraction
Hydrogen bonding - polar molecules have an uneven distribution of charge, weak electrostatic bonds form between the negatively charged region of one molecule and the positively charged region of another

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3
Q

Describe polymerisation and describe what macromolecules are

A

Polymerisation is the process of forming polymers from a chain of monomers.
Macromolecules are large biological polymers

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4
Q

Describe condensation and hydrolysis

A

Condensation - a reaction that produces water (such as when joining monomers)
Hydrolysis - breaking of bonds in polymers using water

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5
Q

Describe metabolism

A

All of the chemical processes taking place in living organisms

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6
Q

Describe how carbohydrates are constructed

A

Carbohydrates are constructed from carbon, hydrogen and oxygen. Carbon forms the backbone to which the other molecules are attached

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7
Q

Describe the structure of monosaccharides

A

A monsaccharide is a sugar with the general formula CH2O(n) where n is any number between 3 and 7. The atoms can be arranged in many ways to form isomers

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8
Q

Describe how to carry out the Benedict’s test for reducing sugars

A

Grind sample in water
Add equal volume of Bendicts reagent
Heat in boiling water bath
Positive result for reducing sugar: red/orange/brown precipitate

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9
Q

Explain how monosaccharides are linked together to form disaccharides

A

Disaccharide formed from two monsaccharides linked by a condensation reaction. Water is removed to form a glycosidic bond

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10
Q

Describe how alpha glucose molecules are linked to form starch

A

Many alpha glucose molecules are linked by 1-4 glycosidic bonds to form the polysacchride starch

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11
Q

Describe the test for non-reducing sugars

A

Grind sample in water
Heat with Benedicts reagent
Blue colour indicates no reducing sugar present
Grind new sample in water
Add hydrochloric acid and heat
Neutralise with sodium hydrogen carbonate
Heat with Benedicts reagent
Positive result for non reducing sugar: red/orange/brown precipitate

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12
Q

Describe the test for starch

A

Add iodine solution to sample of food

Positive result for starch: blue/black

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13
Q

Explain how alpha glucose molecules are arranged to form the polymers of starch and glycogen

A

Starch: alpha glucose form glycosidic bonds to make both branched and unbranched chains. Unbranched chains form an alpha helix
Glycogen: alpha gluocose forms glycosidic bonds to make highly branched chains

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14
Q

Explain how beta glucose molecules are arranged to form the polymer cellulose

A

Beta glucose forms glycosidic bonds to make straight unbranched chains. Each adjacent beta glucose is rotated by 180 degrees. These staright chains form hydrogen bonds with other parallel chains. Groups of cellulose molecules form microfibrils. Parallel groups of microfibrils form fibres of cellulose.

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15
Q

Explain how the molecular structures of starch, glycogen and cellulose relate to their function

A

STARCH: coiled, unbranched chains and branched chains.
Insoluble - does not affect water potential and therefore no osmosis in to cells
Large - does not move out of cells
Compact - lots can be stored in a small space
Branched form has many ends - release glucose rapidly as enzymes can act simulaneously
GLYCOGEN: highly branched chains
Insoluble - does not affect water potential and therefore no osmosis in to cells
Insoluble - does not diffuse out of cells
Compact - lots can be stored in a small space
Highly branched - enzymes act simultaneously to release glucose molecules for respiration
CELLULOSE: parallel cross linked enbranched chains
Cross linked parallel chains - strength
Microfibrils and fibres - strength

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16
Q

Describe the structure of triglycerides and how this relates to their function

A

Structure: Triglycerides are made from a glycerol molecule and three fatty acids. The fatty acids form ester bonds with the glycerol through condensation reactions. Fatty acids vary in length and whether they have double bonds between carbon atoms (unsaturated) or not (saturated)
Function:
- source of energy due to many carbon - hydrogen bonds
- storgae due to low mass to energy ratio
- do not affect osmosis due to large, insoluble nature
- source of water due to high number of hydrogen to oxygen atoms which can release water when oxidised

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17
Q

Describe the roles of lipids

A

Source of energy - when oxidised lipids release twice the energy as the same mass of carbohydrate
Waterproofing - insoluble in water and therefore idea as a waterproof cuticle (plants) or secretions (animals)
Insulation - slow conductor of heat so reduce heat loss. Electrical insulator (myelin sheath around neurones)
Protection- around delicate organs

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18
Q

Describe the structure of phospholipids and how this relates to their function

A

Structure: Glycerol molecules with two fatty acids and one phosphate group attached via condensation reactions. Phospholipds are polar molecules - fatty acid tails repel water (hydrophobic), phosphate heads attract water (hydrophilic)
Function:
Form hydrophobic barrier around cells - polar phospholipids arrange themselves in a bilayer with hydrophilic heads pointing outwards
Cell recognition - the phosphate heads can combine with carbohydrates to form glycolipids

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19
Q

Describe the test for a lipid

A 
Mix sample with ethanol
Shake
Add water
Shake
Positive result for lipid: cloudy white
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20
Q

Explain how amino acids are linked to form polypeptides – the primary structure of proteins

A

Amino acids form dipeptides and then polypeptides via condensation reactions between forming peptide bonds. The water is formed from the OH of the carboxyl group on one amino acid with the H on the amine group of the other amino acid. The sequence of amino acids is called the primary structure

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21
Q

Explain how polypeptides are arranged to form the secondary structure and then tertiary structure of a protein

A

Secondary structure: hydrogen bonds form between the H of the amine groups and the OH of the carboxyl groups causing the chain to be twisted into an alpha helix or beta pleated sheet
Tertiary structure: the specific 3D structure of a protein - formed by disulphide bridges, ionic bonds and hydrogen bonds

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22
Q

Explain how the quaternary structure of a protein is formed

A

The large protein molecule formed from more than one polypeptide chain and additional prosthetic (non-protein) groups

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23
Q

Describe the test for proteins

A

Add sample to sodium hydroxide
Add very dilute copper sulphate and mix
Positive result for protein: purple

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24
Q

Explain how enzymes speed up chemical reactions

A

Reactions can only occur when an activation energy level is overcome, enzymes lower the activation energy level allowing reactions to take place at a lower temperature than normal

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25
Q

Describe how the structure of an enzyme molecule relates to their function

A

The active site is the specific functional part of an enzyme. It’s shape is determined by the primary (and therefore tertiary) structure of the protein. The substrate and active site are complementary to each other and form enzyme substrate complexes.

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26
Q

Explain the lock and key model of enzyme action

A
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27
Q

Explain the induced fit model of enzyme action

A
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28
Q

State two examples of biological monomers.

A

monosaccharides; glucose, fructose and galactose, amino acids, nucleotides

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29
Q

State two examples of biological polymers.

A

polysaccharides - starch, cellulsoe and glycogen, polypeptides, DNA

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30
Q

Name the type of reaction that occurs when two monomers are joined together.

A

condensation reaction

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31
Q

What molecule is always made (released) when two monomers are joined together?

A

water

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32
Q

Name the type of reaction that occurs when a polymer is broken down into a monomer.

A

hydrolysis reaction

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33
Q

What molecules is needed for hydrolysis reaction?

A

water

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34
Q

What three elements are found in monosaccharide?

A

carbon, hydrogen and oxygen

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35
Q

Name the two isomers of glucose.

A

alpha glucose and beta glucose

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36
Q

Draw the two isomers of glucose, high-lighting where they are structurally different.

A
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37
Q

Name two other monosaccharides.

A

fructose and galactose

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38
Q

Describe the test for reducing sugars, including positive and negative results.

A

Add benedicts reagent (blue) and heat. Negative result = stays blue. Postitive result = coloured precipitate formed, red, orange, yellow or green.

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39
Q

Describe how you can find out how much reducing sugar is present (quantitative).

A

Dry and weigh the precipitate, use a colourimeter.

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40
Q

What are the advantages of using a colourimeter to measuring concentration of reducing sugar?

A

Standardised method, not subjective, quantitiative.

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41
Q

What is a disaccharide and describe how one is formed?

A

A disaccahride is formed when two monosaccharides are joined together in a condensation reaction.

42
Q

Name the chemical bond that is present in a disaccharide.

A

Glycosidic bond

43
Q

Which monosaccharides are found in maltose?

A

alpha glucose

44
Q

Draw a molecule of maltose and label the glyosidic bond.

A
45
Q

Write a word equation for the formation of maltose, sucrose and lactose.

A

aplha glucose + alpha glucose => maltose + water. glucose + fructose => sucrose + water glucose + galactose => lactose + water

46
Q

Name the two disaccharides that are reducing sugars.

A

Maltose and lactose

47
Q

Describe the test for non-reducing sugars.

A

Add benedicts reagent (blue) and heat. Negative result = stays blue. Get a new sample and add dilute HCl and boil, then neutralise it with sodium hydgrogencarbonate. Then add benedicts reagent and heat. Negative result = stays blue. Postitive result = coloured precipitate formed, red, orange, yellow or green.

48
Q

What is a polysaccharide and name three examples.

A

Many monosaccharides joined - Starch, glycogen and cellulose.

49
Q

Draw a polysaccharide made up from 4 α-glucose molecules, label all glycosidic bonds.

A
50
Q

Describe the structure of starch.

A

Starch is a mix of amylose and amylopectin, Amylose is a ling, unbracnhed chain of alpha-glucose. It has a coiled structure making it very compact. Amylopectin is a long branched chain of alpha-glucose molecules, it’s side branches (caused by 1, 6, glycosidic bonds)

51
Q

What is the function of starch?

A

Starch is the main energy store in plants.

52
Q

How is the structure of starch linked to its function?

A

“Compact - fit lots in a cell.
Branches in amylopectin - allow easy access to enzymes to allow quick hydrolysis of glycosidic bonds to release energy.
Insoluble in water - does not affect water potential, meaning it does not cause water to enter cells by osmosis (would make cells swell) making it good for storage.”

53
Q

Describe the biochemiclal test for starch.

A

Add iodine - blue/black= starch present

54
Q

Describe the structure of glycogen.

A

Glycogen is highly branched chain of alpha-glucose molecules (lot more branches than amylopectin = lots of 1,6, glycosidic bonds)

55
Q

What is the function of glycogen?

A

Glycogen is the main energy store in animals

56
Q

How is the structure of glycogen linked to its function?

A

Glycogen is very highly branched meaning stored glucose can be released very quickly - important as animals have a higher metabolic rate than plants. It is very compact and is also insoluble in water making it good for storage.

57
Q

Describe the structure of cellulose.

A

Cellulsoe is a long, straight, unbranched chain of beta-glucose. These chains are linked together by hydrogen bonds to form strong fibres called microfibrils.

58
Q

What is the function of cellulose?

A

Structural support for cells (cellulsoe cell wall)

59
Q

How is the structure of cellulose linked to its function?

A

Hydrogen bonds between chains form microfibrils which are strong.

60
Q

Draw and label a simple diagram of a triglyceride.

A

Glycerol and three fatty acids

61
Q

Draw the general structure of a fatty acid.

A
62
Q

What is a saturated fatty acid?

A

Saturated fatty acids do not have any carbon=carbon double bonds, the hydrocarbon tail is ‘saturated’ with hydrogen atoms

63
Q

What is an unsaturated fatty acid?

A

Unsaturated fatty acids do have at least one carbon=carbon double bond in the htdrocarbon tail, causing the chain to kink.

64
Q

Draw a triglyceride, using the general structure of a fatty acid, label all chemical bonds.

A
65
Q

Name the chemical bond formed between glycerol and a fatty acid.

A

Ester bond

66
Q

Define hydrophobic and hydrophilic.

A

hydrophobic = water repelling. hydrophilic = water loving

67
Q

Which part of a triglyceride is hydrophobic?

A

fatty acid

68
Q

Describe how the structure of a triglyceride is linked to its structure.

A

Triglycerides are energy storage molecules. The hydrocarbon tails of the fatty acids contain lots of chemical energy that is released when they are broken down. They are also insoluble in water and so do not affect water potential of the cell (no osmosis).

69
Q

Describe the general structure of a phospholipd.

A

glycerol, 2 fatty acids and phosphate head.

70
Q

Describe how the structure of a phospholipid is linked to its structure.

A

Phospholipds form lipid bilayer of cell membranes (and membrane bound organelles). Function of a cell membrane is to control what enters and leaves the cell, it does this becuase the hydropilic phosphate headsface out towards water (both insoide and outside of the cell) and the hydrophobic tails face inwards, forming a double layer. This means that water soluble substances can not easily pass though the middle of the bilayer - controlling movement through the membrane.

71
Q

Draw the general structure of an amino acid.

A
72
Q

Describe the biochemical test for lipids.

A

Add ethanol to test substance and shake, then pour into water. Positive result = milky emulsion.

73
Q

Name the chemcial bond that is formed between two amino acids during a condenstaion reaction

A

peptide bond

74
Q

Draw a didpeptide and label the peptide bond.

A
75
Q

Describe the biochemcial test for proteins, including a negative and positive test result.

A

Add sodium hydroxide solution to test sample, then add copper sulfate solution. Negative result = solution stays blue. Positive result = turns purple.

76
Q

Describe the primary structure of a protein.

A

Sequence of amino acids

77
Q

Describe the secondary structure of a protein.

A

chain coils into an alpha helix or folds into a beta sheet - held in place by hydrogen bonds.

78
Q

Name the three chemcical bonds found in the tertiary structure of a protein.

A

Hydrogen bonds, ionic bonds and disulphide bridges

79
Q

Describe the quarternary structure of a protein.

A

Two or more polypeptide chains held together by bonds.

80
Q

Name two examples of protens with quarternary structures.

A

Insulin, Haemoglobin, collagen, antibodies

81
Q

What is an enzyme?

A

Biological catalysts that speed up chemical reactions without being used up in the reaction.

82
Q

What is activation energy?

A

Energy needed for a reaction to start.

83
Q

How do enzymes lower the activation energy of a chemcial reaction?

A

By forming an enzyme-substrate complex, this either holds two substrate molecules close together, reducing any repulsion between moelcules allowing bonds to form more easily, OR by putting a strain on bonds allowing substrate molecules to break apart more easily.

84
Q

What is an enzyme-substrate complex?

A

It is when a substrate molecule fit’s into an enzymes active site. This relies upon the shape of the substrate bing complementary to the shape of the enzyme’s active site.

85
Q

Describe the ‘lock and key’ model of enzyme action.

A

The shape of the substrate is an exact fit the shape of the enzyme’s active site allowing it to fit into the active site.

86
Q

Describe the ‘induced fit’ model of enzyme action.

A

The shape of the substrate is comlementary to the shape of the enzyme’s active site, on binding to the active site, the substrate triggers the enzyme’s active site to change shape slightly, forming an enzyme-substrate complex.

87
Q

Explain why the enzyme maltase can only breakdown maltose and not starch.

A

This is because enzymes are specific, only maltose has a shape that is complementary to maltase’s active site, forming an enzyme-substrate complex.

88
Q

Explain why a mutation in the gene that codes for an enzyme could potentially result in the formation of a non-functional enzyme.

A

The sequence of bases in a gene detrmines the primary structure of a protein - the sequence of amino acids. If the sequemce of bases in a gene changes, then the sequence of amino acids in the primary structure of a protein could also change, if the primary structure changes then the tertiary structure could change. Any change in the tertiary structure could change the shape of the active site, meaning the substrate is no longer complmentary in shape to the active site, meaning no enzyme -substrate complexes can be formed.

89
Q

Sketch a graph to show the effect of temperature on the rate of an emzyme-catalysed reaction.

A
90
Q

Explain why an increase in temperature can increase the rate of an enzyme-catalysed reaction.

A

An increaser in temperature increases the kinetic energy of the enzyme and substrate molecules, meaning the molecules are moving faster. This means that the chance of a successful collision between the substrate molecule and the enzymes active site is higher, resulting in more enzyme-substrate complexes being formed = a faster rate of reaction.

91
Q

Explain why an increase in temperature can decrease the rate of an enzyme-catalysed reaction.

A

Above optimum temperature, increasing the temperature makes the enzyme vibrate more, these vibrations break the hydrogen bonds and ionic bonds in the tertiary structure of the enzyme, causing the active site to change shape. This means the substrate is no longer complmentary in shape to the active site, meaning no enzyme -substrate complexes can be formed. The enzyme is denatured.

92
Q

Sketch a graph to show the effect of pH on the rate of an enzyme-catalysed reaction.

A
93
Q

Explain the effects of any deviation away from the optimum pH on the rate of an emzyme-controlled reaction.

A

Any deviation above or below an enzymes optimum pH will reduce the rate of reaction. This is because the H+ ions and OH- ions in acids and alkalis can break the hydrogen bonds and the ionic bonds in the tertiary structure of the enzyme, causing the active site to change shape. This means the substrate is no longer complmentary in shape to the active site, meaning no enzyme -substrate complexes can be formed. The enzyme is denatured.

94
Q

Describe and explain the effect of increasing substrate concentration on the rate of an enzyme-catalysed reaciton.

A

Intitially as the concentration of substrate increases there is an increase in the rate of reaction, this is because increasing the number of substrate molecules increases the chance of a successful collision with an enzyme, resulting in the formation of an enzyme-substrate complex. Above a given concentration of substrate, the rate of reaction plateau’s, this is because all of the active sites are full with substrate molecules, and so adding more substrate molecules makes no difference. At this point enzyme concentration is the limiting factor.

95
Q

Describe and explain the effect of increasing enzyme concentration on the rate of an enzyme-catalysed reaciton.

A

Intitially as the concentration of enzyme increases there is an increase in the rate of reaction, this is because increasing the number of enzyme molecules increases the chance of a successful collision with a substrate, resulting in the formation of an enzyme-substrate complex. Above a given concentration of enzyme, the rate of reaction plateau’s, this is because the concentration of substrate is the limiting factor.

96
Q

Explain how a compeitiive inhibitor works.

A

Competitive inhibitor molecules have a similiar shape to the substrate molecule. They compete with the substrate for the active site, and will temporarily bind to the active site stopping the substarte from binding, reducing the rate of reaction. Increasing the concentration of the substrate will increase of the rate of reaction.

97
Q

Explain how a non-competitive inhibitor works.

A

Non-competitive inhibitor molecules bind to the enzyme away from the active site, this causes the active site to change shape, meaning the shape of the substrate is no longer complementary to the active site and so can not bind and form an enzyme-substrate complex. Increasing the concentration of the substrate will no impact of the rate of reaction.

98
Q

Describe two ways in which you can measure the rate of an enzyme-catalysed reaction.

A

You can measure the rate of a reaction by measuring how quickly the substrate is broken down OR how quicxkly the product is made.

99
Q

Describe how you can calculate the initial rate of a rection from a graph.

A

Draw a tangent on the curve using a ruler at time = 0. Then caqlculate the dradient of the tangent = change in y/change in x

100
Q

If you are testing the effect of temperature on an enzyme-catalysed reaction, what other variables would you keep the same?

A

pH (use a buffer), substrate concentration and enzyme concentration.

Biology (20 decks)

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