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Biology A-Level > Topic 1 - Biological Molecules (B) > Flashcards

Topic 1 - Biological Molecules (B) Flashcards

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1
Q

What are monomers

A

Smaller units that larger molecules (polymers) are made from

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2
Q

What are the three examples of monomers

A

Amino acids, monosaccharides and nucleotides

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3
Q

What are polymers?

A

Molecules formed from a large number of monomers joined together

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4
Q

What are the three examples of polymers

A

DNA, Starch, proteins

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5
Q

What is a condensation reaction

A

A reaction which joins two molecules together with the formation of a chemical bonds and a molecule of water.

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6
Q

What is a hydrolysis reaction

A

The breaking down of polymers. A water molecule is added and the chemical bond is broken, resulting in two monomers.

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7
Q

What are monosaccharides

A

monomers which larger carbohydrates are made from

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8
Q

What are common monosaccharides

A

Glucose, fructose and galactose

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9
Q

Outline glucose’s structure

A

Has 6 carbon atoms in each molecule, 6 oxygen atoms and 12 hydrogen.

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10
Q

What are the glucose isomers and how are they different (You must be able to draw these)

A

Alpha and beta.
Alpha - H OH
Beta - OH H

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11
Q

What happens when two monosaccharides undergo a condensation reaction

A

-A disaccharide is formed
-Joined together by glycosidic bonds

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12
Q

Outline maltose as a disaccharide

A

Formed with the condensation of two alpha glucose molecules

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13
Q

Outline sucrose as a disaccharide

A

Formed by the condensation of a glucose molecule and a fructose molecule

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14
Q

Outline lactose as a disaccharide

A

Formed by the condensation of a galactose and glucose molecule

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15
Q

What are polysaccharides

A

Formed by the condensation of many glucose units

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16
Q

What is the monomer and polysaccharides of starch

A

-The monomer is alpha glucose
-The polysaccharides are called amylose and amylopectin

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17
Q

What is the structure of a starch polysaccharide

A

-Large and insoluble
-Branched
-Coiled

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18
Q

What is the function of starch polysaccharide

A

To store glucose in plants for respiration to take place

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19
Q

How does the structure of starch help with its function? (3)

A

-It’s a large molecule so it’s insoluble so doesn’t effect the water potential of the cell
-Branched so has more “ends” so glucose easily released for respiration
-Coiled so compact so more can be stored

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20
Q

What is the monomer of glycogen

A

alpha glucose

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21
Q

Outline the structure of glycogen polysaccharides

A

-Large and insoluble
-More branched than starch
-Coiled to a degree

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22
Q

What is the function of glycogen

A

In liver and muscle cells to store glucose for respiration

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23
Q

How does glycogens structure help it with its function (3)

A

-Highly branched so more “ends” so glucose can be released quickly for respiration
-Large so insoluble so doesn’t affect water potential
-Coiled so compact so more can be stored

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24
Q

Outline the method for testing for reducing sugars and what precautions/hazards

A

-Add some benedict’s solution to the sample you’re testing
-Heat the sample to above 90°C
-The hazard is copper sulphate and to mitigate this wear safety goggles and wash hands after you’re done

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25
Q

What results will you see if the benedict’s test is positive initially and what does this prove

A

-It will turn from blue > green > yellow > orange > brick red precipitate depending on the concentration
-Proves the presence of a reducing sugar

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26
Q

What are the examples of reducing sugars

A

All monosaccharides and all disaccharides apart from sucrose

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27
Q

If you’re testing for sugars and the reducing sugar test is negative what method do you carry out?

A

-Add the sample into a boiling tube and add 1cm^3 of hydrochloric acid and swirl it to mix
-Place to the tube into the water bath to heat for 5 minutes and remove the tube using tongs and allow it to cool
-Apply two spatulas of the sodium hydrogen carbonate to the tube and wait until the fizzing stop
-Add 1cm^3 of the Benedict’s solution and heat it in the water bath for 5 minutes.
-Check for colour change and record the results/observations

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28
Q

What are the non-reducing sugar examples

A

Sucrose

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29
Q

Why do you add hydrochloric acid solution to a sample when undertaking the benedict’s test for non-reducing sugars

A

You need to neutralise the sample as benedict’s doesn’t work for samples with acidic conditions

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30
Q

what is the monomer of cellulose

A

beta glucose

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31
Q

Outline the structure of a cellulose polysaccharide

A

-Microfibrils are long chains of cellulose molecules
-Between the layers are hydrogen bonds (weak)
-The molecules are alternately flipped

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32
Q

what is the function of cellulose

A

Cellulose makes up cell wall which makes the cell strong

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33
Q

How is the structure of cellulose related to its function

A

Cellulose molecules held by lots of hydrogen bonds so strong for the cell wall

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34
Q

Outline the test for starch

A

-Add 2-3 drops of iodine to sample
-Blue-black predicate

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35
Q

What type of reaction is the one that breaks disaccharides down into monosaccharides

A

hydrolysis

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36
Q

What type of reaction forms glycogen, polysaccharides and cellulose

A

Polymerisation/condensation

37
Q

What group are triglycerides and phospholipids in

A

Two groups of lipid

38
Q

How are triglycerides formed

A

A condensation reaction between three fatty acids and one glycerol

39
Q

Why are lipids insoluble in water

A

-Fatty acid moleucles have hydrophobic tails made of hydrocarbons

40
Q

Outline the structure of fatty acids

A

-Double bond oxygen to carbon
-The carbon has a single bond between an HO group and a variable ‘R’
-The variable ‘R’ can be a saturated or unsaturated hydrocarbon tail
-RCOOH

41
Q

Outline saturated fatty acids

A

Don’t have any double bonds between their carbon atoms. The fatty acid is saturated with hydrogen.

42
Q

Outline unsaturated fatty acids

A

Have double bonds between carbon atoms, which cause the chain to kink

43
Q

Outline what happens when a triglyceride is formed

A

-An ester bond forms between the fatty acid and glycerol, releasing a molecule of water
-This process happens twice more to form a triglyceride

44
Q

How are phospholipids formed

A

-A glycerol is attached to two fatty acids and one phosphate group
-Attached by ester bonds

45
Q

What are the properties of triglyceride

A

-Mainly storage molecules as long hydrocarbon tails of fatty acids contains lots of chemical energy so is released when they are broken down
-Insoluble so don’t affect water potential of cell and cause water to enter cells by osmosis (which would make them swell)
-They bundle together as insoluble droplets in cells as the tails face inwards shielding the water with their glycerol heads

46
Q

What are the properties of phospholipids

A

-Make up the bilayer of cell membranes which control what enters and leaves a cell.
-Phospholipid heads are hydrophilic and their tail are hydrophobic and the double layer has their heads facing out towards the water on either side. The centre of the bilayer is hydrophobic, so water-soluble substances can’t easily pass through it - the membrane acts as a barrier to those substances

47
Q

Outline test for lipids (emulsion)

A

-Shake the test substance with ethanol for about a minute then pour the solution into water
-Any lipid will show up as a milky emulsion
-The more lipid there is, the more noticeable the milky colour will be

48
Q

What is a single molecule of adenosine triphosphate (ATP) made from

A

Ribose, a molecule of adenine and three phosphate groups

49
Q

Outline hydrolysis of ATP

A

-Catalysed by ATP hydrolase
-Forms ADP and Pi (Inorganic phosphate group)

50
Q

Outline condensation to ATP

A

-Catalysed by ATP synthase
-From ADP + Pi > ATP

51
Q

What are the functions of ATP

A

-Release energy
-Provide inorganic phosphate to other molecules which become more reactive

52
Q

Where is ATP made and why

A

-Made in respiration (to release energy)
-Made in photosynthesis (to be used in photosynthesis)

53
Q

Why is ATP useful

A

-Hydrolysis of ATP releases small packets of energy which is perfect amount for chemical reaction in cells
-ATP hydrolysis only one step reaction = energy released quickly

54
Q

Outline H-bonds

A

-Form between molecules and cause many of water’s characteristics
-Weak (stronger than IMFs) but lots of them can give strength (e.g. cellulose)

55
Q

Outline water as a temperature buffer

A

Water has a high specific heat capacity so a lot of energy is needed to change the temperature of water, so it has a reasonably constant temperature

56
Q

Why is water an ideal habitat for many organisms

A

-The ocean is a thermally stable habitat, as it has little temperature fluctuation in a large volume so aquatic creatures can live in a stable environment.

57
Q

Outline water as a metabolite

A

-Water is an important metabolite and is often a reactant necessary to start a metabolic reaction and is also often a byproduct of metabolic reactions.
-Key metabolite in condensation and hydrolysis reactions.

58
Q

Outline water as a solvent

A

Polar solvent for many biological molecules. Many ions and covalently bonded polar substances will dissolve in it. This allows chemical reactions to occur within cells (as the dissolved solutions are more chemically reactive when they are free to move about).

59
Q

Outline waters latent heat of evaporation

A

-To change state a large amount of thermal energy must be absorbed by water to break the hydrogen bonds and evaporate.
-This is an advantage for living organisms as only a little water is required to evaporate for the organisms to lose a great amount of heat
-This provides a cooling effect for living organisms, for example the transpiration from leaves or evaporation of water in sweat on the skin.

60
Q

Outline water as a cohesive

A

-Hydrogen bonds between water molecules allows for strong cohesion between molecules
-This allows columns of water to move through the xylem of plants and through blood vessels in animals
-Enables surface tension where a body of water meets the air, these hydrogen bonds occur between the top layer of water molecules to create a sort of film on the body of water.
-Water can also hydrogen bond to other molecules such as cellulose which is known as ‘adhesion’. This allows water to move up the xylem due to transpiration.

61
Q

Outline phosphate ions

A

-In ATP
-In phospholipid bilayer
-DNA, RNA

62
Q

Outline hydrogen ions

A

-H+ or proton
-More H+ = lower pH

63
Q

Outline iron ions

A

-Fe2+
-In haemoglobin

64
Q

Outline sodium ions

A

-Through sodium potassium pump 2K+ moves in and 3Na+ moves out.
-Active transport > energy release > in respiration
-Less oxygen = less energy release = less active transport

65
Q

What is the monomer of a protein

A

Amino acid

66
Q

Outline the structure of an amino acid

A

NH2 group, COOH group, R group and H bond all attached to a central carbon atom

67
Q

How many different amino acids are there and what are the differences in them

A

-There are 20 different amino acids
-The difference is in the R group that makes up the amino acid

68
Q

What is the amino acid with the R group ‘H’

A

Glycine

69
Q

What is the amino acid with the R group ‘CH3’

A

Alanine

70
Q

What re the two amino acids that have an ‘S’ atom in the R group

A

-Methionine
-Cysteine

71
Q

What is a polymer with two amino acids called

A

Dipeptide

72
Q

What is a polymer with many amino acids called

A

Polypeptide

73
Q

How are polypeptide and di peptides formed and what are the bonds holding therm together

A

-Condensation reaction between amino acids
-Peptide bonds

74
Q

What does the structure of a protein determine

A

The proteins function

75
Q

Outline the primary structure of a protein

A

-Polypeptide bond/sequence of amino acids
-Contains peptide bonds
-Sequence of AAs determines where bonds form and therefore the 3D structure of the protein

76
Q

Outline the secondary structure of a protein

A

-Alpha helix or beta pleated sheet
-Hydrogen bonds between NH and CO groups

77
Q

Outline the tertiary structure of a protein

A

-How the secondary structure is folded/specific 3D shape of the protein
-Contains H-bonds, disulphide bridges and ionic bonds

78
Q

Outline the quarternary structure of a protein

A

-2 or more polypeptides linked together
-Contains H-bonds, disulphide bridges and ionic bonds

79
Q

Outline enzymes as a biological catalyst

A

-Increases rate of reaction by lowering activation energy
-Biological catalysts can be used over and over again as not used up in the reaction.

80
Q

Why is the induced-fit hypothesis better than the lock and key theory

A

-It explains how the substrate and products can both fit into the active site when they are different shapes
-How the activation energy is lowered (ie strain is put onto the bonds of the substrate to lower the activation energy(

81
Q

Outline the induced fit theory

A

In this model the enzyme and substrate interact with each other:
-The enzyme and its active site (and sometimes the substrate) can change shape slightly as the substrate molecule enters the enzyme
-This ensures an ideal binding arrangement between the enzyme and substrate is achieved
-This maximises the ability of the enzyme to catalyse the reaction

82
Q

How are enzymes specialised?

A

Each enzyme is specialized for one substrate, which is specialized for one type of reaction or for a few reactions.

83
Q

How are enzyme substrate complexes formed

A

The properties of an enzymes relate to the tertiary structure of its active site and its ability to combine with complementary substrates to form an enzyme-substrate complex

84
Q

How does enzymes concentration affect the rate of reaction

A

-Initially increases rate of reaction as the rate of substrate and enzyme collisions increase.
-If the substrate concentration is kept constant the rate of reaction will eventually stop increasing.
-If supply of substrate is continuously increased the rate will not stop increasing as you increase the enzyme concentration.

85
Q

How does temperature affect rate of reaction

A

-Low temperatures mean particles have less kinetic energy so less collisions = slow rate of reaction
-As you increase the temperature particles have more kinetic energy so more collisions between reactant particles meaning rate of reaction is increased and more substrate-enzyme complexes are formed
-Enzymes have an optimum temperature which is the temperature they catalyse reactions at maximum rate
-As the temperature increases over optimum pH the enzymes begin to denature and rate of reaction drops sharply as bonds begin to break changing the shape of the active site, meaning substrate-enzyme complexes can’t be formed

86
Q

How does pH affect enzyme rate of reaction

A

-All enzymes have an optimum pH where they catalyse reactions at the fastest rate
-Enzymes are denatured at extremes of pH as bonds hold the tertiary structure of the enzyme
-Below and above the optimum pH of an enzyme, solutions with an excess of H+ ions and OH- ions can cause these bonds to break, this alters the shape of the active site which means enzyme-substrate complexes form less easily and eventually enzyme-substrate complexes can no longer form at all

87
Q

Outline competitive inhibitors

A

-Similar shape as substrates and fit into the active site therefore competing with the substrate
-Increasing substrate concentration is able to increase rate of reaction as more substrate molecules can collide with the enzymes active sites to form substrate-enzyme complexes

88
Q

Outline non-competitive inhibitors

A

-Inhibitors bind to the enzymes at an alternative site which alters the shape of the active site so the substrates can no longer fit in, and no more substrate-enzyme complexes can be formed
-Increasing the substrate concentration cannot increase the rate of reaction as the site of the active site remains changed from the inhibitors and enzyme-substrate complexes are still unable to be formed.

89
Q

What is the test for proteins and what results would you get

A

-Biurets reagent
-Blue to lilac is positive

Biology A-Level (5 decks)

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