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A Level Biology Paper 1 > Section 1 - Chapter 1: Biological Molecules > Flashcards

Section 1 - Chapter 1: Biological Molecules Flashcards

1
Q

What is a monomer? + example

A
  • Smaller units from which larger molecules are made.
  • e.g amino acid, monosaccharides, nucleotides
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2
Q

What is a Polymer?

A
  • Molecules made from a large number of monomers
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3
Q

What is Polymerisation?

A

The process by which polymers are formed

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4
Q

What is the process called when Polymers turn to Monomers? (splits)

A

Hydrolysis -

  • Breaks the chemical bond between 2 molecules and involves the use of water
  • Disaccharides are split into monosaccharides
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5
Q

What is the process called when Monomers turn to Polymers?

A

Condensation

  • Monomers join together to form a polymer
  • Joins 2 molecules together with the formation of a chemical bond and involves the elimination of a water molecule
  • A covalent bond is formed
  • e.g 2 monosaccharides forms a disaccharide
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6
Q

What is a Monosaccharide? + example

A
  • Single Sugar, sweet tasting/soluble
  • Contain Carbon, Hydrogen and Oxygen
  • Formula (CH2O)n
  • Play an important role in cell reactions
  • e.g fructose, glucose, galactose
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7
Q

What is a Disaccharide? + examples

A
  • 2 Monosaccharides joined together
  • E.g Maltose, Sucrose, Lactose
  • C12H22O11
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8
Q

What is a Polysaccharide + examples?

A
  • Lots of Monosaccharides joined together in a condensation reaction
  • e.g glycogen, starch, cellulose
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9
Q

What is a Carbohydrate?

A
  • Organic Molecules
  • Containing 3 elements: carbon, hydrogen, oxygen
  • The general formulae is (CH2O)n
  • Ratio: C:H:O= 1:2:1
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10
Q

What is the structure of a Alpha glucose?

A

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11
Q

What are the reactive groups in a Monosaccharide?

A
  • Carboxyl group: C=O
  • Hydroxyl group: OH
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12
Q

What is the function of carbohydrates?

A
  • Great source of energy
  • Used commonly as a substrate for respiration
  • Forms cell walls
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13
Q

What is the Structure of a Beta Glucose?

A
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14
Q

What are some examples of Carbohydrates?

A
  • Pasta
  • Rice
  • Bread
  • Starch
  • Fructose
  • Glucose
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15
Q

What are the characteristics of lipids?

A
  • Contain carbon, hydrogen and oxygen
  • Proportion of oxygen to carbon and hydrogen is smaller
  • Insoluble in water
  • Soluble in organic solvents (e.g alcohol)
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16
Q

What are some examples of lipids?

A
  • Oils
  • Triglycerides
  • Waxes
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17
Q

What is the function of Nucleic Acids?

A
  • To carry the genetic code for the production of proteins
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18
Q

What are some examples of Nucleic Acid?

A
  • DNA
  • RNA
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19
Q

What are the functions of protein

A
  • Forms the structual components in plasma membranes
  • Required for the structure, function, and regulation of tissues and organs
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20
Q

What are some examples of proteins

A
  • Insulin
  • Amylase
  • Haemoglobin
  • Keratin
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21
Q

What are the roles of lipids

A
  1. Source of energy - oxidised provides more than twice the energy as the same mass of carbohydrate + releases valuable water
  2. Waterproofing - insoluble in water
  3. Insulation - fats are slow conductors of heat. Below body surface = retains body heat
  4. Protection - Fat is often stored around delicate organs
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22
Q

What is the structure of triglycerides and what causes variation.

A
  • Have 3 fatty acids combined to a glycerol molecule. Each fatty acid forms an ester bond with glycerol in a condensation reaction
  • Glycerol molecule in triglycerides are the same but properties (variation) depends on the fatty acid tails: chain
    • All fatty acid tails have carboxyl group + hydrocarbon chain
    • No double bonds = saturated
    • 1 double bond = monounsaturated, 2 more polyunsaturated
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23
Q

What is the structure of phospholipids

A
  • Similar to triglyceride but 1 fatty acid is replaced by a phosphate
  • Phospholipid made of 2 parts:
    • Hydrophilic head - attracted to water
    • Hydrophobic tails - orientates away from water
  • When polar phospholipid molecules are placed in water they position so heads face water and tails are away from water
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24
Q

How is the structure of triglycerides suited to its function

A
  1. High ratio of energy storing carbon - hydrogen bonds - excellent source of energy
  2. Low mass to energy ratio - good storage molecule, energy stored in a smaller volume, animals dont carry much
  3. Large, Non-polar molecules - insoluble in water, storage is not affected by osmosis (water potential)
  4. High ratio of hydrogen to oxygen atoms- triglycerides release when oxidised, provides a source of water
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25
Q

How is the structure of phospholipids related to their properties

A
  • Polar molecules - in aqueous environments form bilayers within cell-surface membranes
  • Hydrophilic head helps hold the surface of the cell membrane
  • The phospholipid structure helps to form glycolipids combining carbohydrates with the surface - Important in cell recognition
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26
Q

What are the 2 types of lipids

A
  • Triglycerides and phospholipids
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27
Q

Where is Glycogen found

A
  • Animals and bacteria (never plants)
  • It is stored as small granules in muscles and liver
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28
Q

What is the monomer of glycogen and what is its bonds

A
  • Alpha glucose
  • 1-4, 1-6 glycosidic bonds
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29
Q

What is Glycogen’s structure

A
  • Like starch it is branched
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30
Q

How is the structure of glycogen suited to its function

A
  • It is large and insoluble - doesnt draw water into the cell by osmosis and doesnt diffuse out
  • Complex/Helical structure - a lot stored in a small space, compact shape
  • More highly branched than starch - has more ends that can be acted on simultaneously by enzymes, rapidly broken into glucose monomer and used in respiration
31
Q

Where is starch found

A
  • Plants (small grains) - large amounts in seeds and tubers
32
Q

What is the monomer of starch and what is its bonds

A
  • Alpha glucose
  • 1-4, 1-2 glycosidic bonds
33
Q

What is starchs structure

A
  • Chains can be branched or unbranched
  • Unbranched wound into a tight coil making it compact
34
Q

How is the structure of starch suited to its function

A
  • Large and insoluble - so doesnt affect water potential (no osmotic effect)
  • Coiled/helical shape - a lot stored in a small space - compact
  • Rapidly hydrolysed to a-glucose- it is easily and readily used in respiration
  • Branched form has many ends - which can be acted on by enzymes simultaneously
35
Q

Where is cellulose found

A
  • Found in plant cell walls
36
Q

What is the monomer of cellulose and what is its bonds

A
  • Beta glucose
  • Hydrogen bonds form cross linkages between adjacent chains. The sheer overall number of chains = strength
  • Cellulose molecules group together to form microfibrils
  • Joined by 1-4 glycosidic bonds
37
Q

How is the structure of cellulose suited to its function

A

Major component of plant cell walls

  • Straight unbranched chains
  • Made of Beta glucose - so can form long straight unbranched chains
  • The cellulose chains run parallel- and are crossed linked by hydrogen = add collective strength
  • Cellulose molecules are grouped to form mocrofibrils - provides more strength
38
Q

What is Metabolism

What is Catabolism

What is Anabolism

A
  • All the chemical processes that take place in a living organism
  • Breakdown of large molecules into smaller ones
  • Building of small molecules into large ones
39
Q

What is the test for starch

A
  1. Place 2cm3 of sample into test tube or 2 drops into a depression on a spotting tile
  2. Add 2 drops of iodine solution + shake
  3. Presence of starch is indicated by a blue-black
40
Q

What is a reducing sugar

A
  • A sugar that can donate an electron to reduce another chemical (Benedicts reagent)
41
Q

What is the method for testing for a reducing sugar

A
  1. 2cm3 of sample in a clean test tube
  2. An equal volume of Benedict’s reagent added
  3. The solution is heated in a bath for 3-5 mins
  4. If reducing sugar is present :
    1. They will reduce Cu2+ in copper sulfate to form an orange- red percipitate copper oxide
    2. The colour of the mixture can be used to estimate the initial concentration of reducing sugars
42
Q

What is the structure of cellulose

A
  • Straight, unbranched chains
  • Run parallel
  • Overall number of hydrogen bonds adds strength
43
Q

What is the structure of cellulose suited to its function

A
  • Made with beta glucose so form long straight unbranched chains
  • Cellulose molecules run parallel and cross linked with hydrogen bonds - adds collective strength
  • These molecules are grouped to form microfibrils - grouped again to form fibres to provide more strength.
44
Q

What is the test for non-reducing sugars.

(What do you have to do first to make a non-reducing sugar into a reducing sugar)

A
  1. Add dilute hydrochloric acid to the sample - to break it down into its monosaccharides
  2. The test tube is heated in a boiling water bath for 3-5 mins
  3. Sample is neutralised with sodium hydrogencarbonate solution
  4. Heat sample with benedicts
45
Q

What is the lipid test (emulsion test)

A
  1. Get a dry/ grease free test tube
  2. Add 2cm3 of sample add 5cm3 of ethanol
  3. Shake to dissolve lipid
  4. Add 5cm3 of water and shake
  5. A milky white emulsion indicates a positive result.
46
Q

What is the monomer of protein

A

Amino acid

47
Q

How is a dipeptide formed. How is a polypeptide formed

A
  1. Formed when 2 amino acids join together in a condensation reaction
  2. Formed when more than 2 amino acids are joined together in a condensation reaction
48
Q

What is the structure of an amino acid

A
  • A carboxyl group (-COOH)
  • An amine group/amino group (-NH2)
  • An R-group: a variable side group) a variety of different chemical groups. Each amino acid has a different R-group. There are 20 amino acids found in living organisms.
  • Hydrogen atom - H
49
Q

How are amino acids combined and what do they form

A
  • Amino acids are linked together in condensation reactions to form dipeptides and polypeptides
    • A water molecule is released (combined from -OH from carboxyl group and -H from amino group)
  • The bonds formed between amino acids is a peptide bond (between C and N atoms)
  • These bonds can be broken by the addition of water (hydrolysis) into amino acids
50
Q

What is the Primary Structure of an amino acid

A
  • The sequence, number and type of amino acids in the polypeptide chain
  • It is the primary structure that determines its ultimate shape and function - a change to a single amino acid can lead to a change in the shape and function.
51
Q

What is the Secondary Structure of proteins

A
  • The hydrogen of the -NH group has an overall positive charge
  • Whilst O of -C=O has a negative charge
  • These 2 groups form weak bonds called hydrogen bonds between amino acids in the chain.
  • This causes the polypeptide chain to be coiled into alpha helix or folded into beta-pleated sheets
52
Q

What is the Tertiary Structure of proteins

A
  • The coiled or folded chain of amino acids can be coiled or folded further to give the complex and specific 3D structure of each protein
  • This structure is maintained by bonds:
    • Disulfide bridges - fairly strong
    • Ionic bonds - formed between carboxyl and amine groups that aren’t involved in formation of peptide bond. Weaker/broken by changes in pH
    • Hydrogen bonds - numerous but easily boken.
53
Q

How are proteins folded

A
  • The folding ensures the R-groups that are polar and hydrophilic are on the outside of the molecule
  • The non-polar/hydrophobic groups are on the inside
    • This allows arrangement to be more stable
54
Q

What is the Quaternary Structure

A
  • Large proteins often form complex molecules containing a number of individual polypeptide chains.
  • The quaternary structure is the way the polypetide chains are assembled together.
  • The quaternary structure is the protein’s final 3D structure
55
Q
  1. What does a proteins shape determine
  2. Put examples of proteins
A
  1. Determines its functions
  2. Globular (e.g enzymes and haemoglobin) - soluble, carry out metabolic functions, transport proteins
  • Fibrous (e.g keratin - hair/nails and collagen - found in connective tissue) - consist of long polypeptide chains lying parallel to eachother with cross links. Very stable.
  • Antibodies are enxamples of proteins.
56
Q

What is the test for proteins

A
  • The biuret test - detects peptide bonds
  1. Place a sample of solution in a test tube and add an equal volume of sodium hydroxide solution (make alkaline)
  2. Add a few drops of very dilute copper sulfate solution and mix gently
  3. A purple colouration indicates presence of peptide bonds. Stays blue if no protein is present.
57
Q
  1. What part of an enzyme is functional
  2. What is the molecule called that an enzyme acts on
A
  1. The active site
    1. Made of relatively small number of amino acids.
  2. Substrate
    1. This fits into depression to form an enzyme-substrate complex
    2. The substrate is held within the site by bonds formed between amino acids on the active site and the substrate.
58
Q

What is the model called for enzyme action

A

The induced fit model. - helps to explain why enzymes are so specific an bond to a particular substrate.

  • When an enzyme and substrate interact - the proximity of the substrate ( a change in the environment of the enzyme) leads to a change in the enzyme that forms the active site.
  • As it changes shape, the enzyme puts a strain on the substrate molecule. The strain distorts bonds in the substrate which lowers the activation energy
59
Q

Explain why the induced fit model is a better explanation of enzyme action than lock and key

A
  • Key operates on a lock which is specific - a substrate will fit in only 1 particular active site
  • A limitation - the enzyme like a lock is considered as a rigid structure. Scientists observed that other molecules could bind to the enzyme at sites other than the active site.
  • This suggested the enzyme’s shape was being altered by the binding molecule - structure is flexible not rigid.
60
Q

What are catalysts

A
  • Catalysts lower the activation energy/ alter the rate of a reaction but are chemically unchanged at the end, They can be reused repatedly and are effective in small amounts.
  • Enzymes are globular proteins and acts as catalysts.
61
Q

What are the conditions for reactions to take place

A
  • Molecules must collide with sufficient energy to alter the arrangement of their atoms to produce product
  • The free energy of the products must be less than that of the substrates
  • Many reactions require an initial amount of energy to start. The minumum energy needed to activate the reaction - activation energy
62
Q

How do enzymes work to catalyse the reaction. How does it lower the activation energy

A
  • Enzymes work by lowering the actibvation energy :
    • If 2 substrate molecules need to be joined, being attached to the enzyme holds them together. Reducing repulsion so they can bond easily
    • Fitting into the active site puts strains on the bonds of the substrate. So it breaks more easily.
63
Q

For an enzyme to work it must

A
  • Come into physical contact with its substrate
  • Have an active site which fits the substrate.
64
Q

How do you measure the progress of an enzyme-catalysed reaction

A
  • Usually measure its time course - how long it takes for a particular event to run its time course
  • Changes most frequently measure are
    • The formation of products
    • The disappearance of substrate
65
Q

Give an explanation about an enzyme catalysed reaction using graphs

A
  • At first there ia a lot of substrate and no product.
    • It is very easy for substrate to come into contact with the empty active sites on the enzymes
  • All active sites are filled at any moment and the substrate is rapidly broken down into its products.
  • The amount of substrate decreases - resulting in an increase of product formed
  • It becomes difficult for the substrate to come into contact with the enzyme because there are fewer substrate and product ‘gets in the way’ - prevents from reaching
  • It therefore takes longer for substrate to be broken down - rate of disappearance slows
  • The graph flattens because all substrate is used up and no new product can be produced
66
Q

How do you measure the rate of change at a point on a graph

A
  • Measure gradient at a chosen point
  • Draw a tangent on the curve and finding the gradient.
67
Q

What is the effect of temperature on the rate of enzyme action

A
  • A rise in temperature increases kinetic energy of molecules.
  • In an enzyme-catalysed reaction - this means more enzyme and substrate molecules come together to form enzyme-substrate complexes more often
    • On a graph - this gives a rising curve
    • The temperature rise also begins to cause the hydrogen bonds to break - active site changes
    • The enzyme becomes disrupted (denatured - permanent change)
68
Q

What is the effect of pH on enzyme action

A
  • A change in pH away from the optimum reduces enzyme action.
  • If the change is more extreme = denatured
  • A change in pH alters ionic and hydrogen bonds of the active site that hold the tertiary structure - as a result no enzyme substrate complexes can be formed
69
Q

What is the effect of enzyme concentration on the rate of reaction

A
  • The more enzyme molecules there are, the more likely a substrate molecule will collide with one to form enzyme substrate complex
  • As long as there is an excess of substrate - increasing enzymes leads to a proportionate increase in rate
70
Q

What is the affect of substrate concentration on the rate of enzyme action

A
  • If concentration of enzyme is fixed, then the rate of reaction is propotionate to the concentration of substrate.
  • At low concentrations, enzyme has limited number of substrates to bind to - active sites arent at full capacity
  • They are gradually filled as substrate conc is increased.
  • After that substrate wont have any effect - levels off
71
Q

What are the enzyme inhibitors and what are the 2 types

A
  • Are substances that directly or indirectly interfere with the functioning of the active site of an enzyme and reduce its activity.
  • Competitive inhibitors: bind to active site
  • Non-competitive: bind to position other than active site
72
Q

What are Competitive inhibitors

A
  • Have a molecular shape similar to substrate
  • Allows them to occupy active site of enzyme and compete with substrate.
  • It is the difference between concentration of inhibitor to concentration of substrate that determines effect on enzyme activity
    • Substrate conc increased - inhibitor effecr reduced.
73
Q

What is a Non-Competitive inhibitor

A
  • They attach themselves to an enzyme at a binding site which isnt the active site.
  • Upon attaching to the enzyme, the inhibitor alters the shape of the enzyme’s active site so substrate can’t occupy it (enzyme can’t function)
  • Increase in substrate = doesnt decrease effect of inhibitor (not competing for same site)

A Level Biology Paper 1 (15 decks)

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