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AS BIO - BIOLOGICAL MOLECULES > C1 - BIOLOGICAL MOLECULES > Flashcards

C1 - BIOLOGICAL MOLECULES Flashcards

monomers and polymers carbohydrates polysaccharides lipids proteins enzymes water ions

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1
Q

explain how biological molecules are evidence for evolution

A

all cells are made from bio molecules, ex - amino acids, which is indirect evidence for the theory ev

all organisms on earth have descended from one-a few common ancestors BECAUSE all organisms share some similar biochem

biochem = same nucleic acids, ex - DNA/RNA

despite sharing some same biochem, they have diversified over time due to EVOLUTION

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2
Q

what are monomers

A

small and basic units

many of them bonded form polymers

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3
Q

examples of monomers

A

amino acids

monosaccharides

nucleotides

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4
Q

what are polymers

A

large and complex molecules that are made of many (more than 2) monomers

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5
Q

examples of polymers

A

proteins

carbohydrates

nucleic acids (DNA/RNA)

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6
Q

monomers -> polymers

A

condensation reaction

loss of water molecule

creation of a chemical bond

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7
Q

polymers -> monomers

A

hydrolysis reaction

use of a water molecule to break down polymer into its constituent monomers

chemical bond is broken

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8
Q

what are sugars

A

‘carbohydrates’

sugar is the general term for monosaccharides and disaccharides

all carbohydrates are made of only C, H and O

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9
Q

what is the monomer of sugars/carbs

A

monosaccharides

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10
Q

examples of monosaccharides

A

glucose

fructose

galactose

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11
Q

what is glucose

A

monosaccharide

hexose sugar, 6 carbon atoms

2 isomers - alpha+beta glucose

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12
Q

what is the difference between alpha and beta glucose

A

the hydrogen and hydroxyl group are inverted on the carbon 1 atom of BETA glucose

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13
Q

what are dissacharides

A

molecules made of 2 monosaccharides

condensation reaction between 2 monosaccharides + the formation of a GLYCOSIDIC bond

formation involves the loss of a water molecules because it is a CONDENSATION reaction

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14
Q

examples of dissacharides

A

maltose = glucose+glucose (alpha)

sucrose = glucose+fructose

lactose = glucose+galactose

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15
Q

describe the benedicts test for REDUCING sugars

A

heat sample WITH benedicts reagent (heat by adding to a boiling water bath)

positive result = sample forms a brick red, orange, yellow or green precipitate

negative result = sample stays blue

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16
Q

what does a negative result on the benedicts test for REDUCING sugars mean

A

no reducing sugars

non reducing sugars may be present

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17
Q

how do you measure the concentration of reducing sugars

A

the higher the concentration of reducing sugar, the further the colour change AND the closer it is to brick red, the higher the conc of reducing sugar

filter the solution and weigh the precipitate

remove the precipitate and use a colorimeter to measure the absorbance of benedicts remaining

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17
Q

describe the benedicts test for NON REDUCING sugars

A

heat a new sample with HYDROCHLORIC ACID and then neutralise this with SODIUM HYDROGENCARBONATE

heat this sample WITH benedicts reagent

positive result = sample forms a brick red, orange, yellow or green precipitate

negative result = sample stays blue, no reducing or non reducing sugars present in sample

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18
Q

what are polysaccharides

A

carbohydrates (sugars)

made of more than 2 monosaccharides joined

monosaccharides -> polysaccharide via condensation reaction

polysaccharide -> monosaccharide via hydrolysis reaction

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19
Q

what is the chemical bond formed for polysaccharides

A

glycosidic

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20
Q

give an example of a polysaccharide and its monomers

A

amylose - poly

alpha glucose/ glucose molecules - mono

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21
Q

name the 3 main polysaccharides

A

starch

glycogen

cellulose

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22
Q

describe the function of starch

A

how plants store excess glucose

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23
Q

describe starch

A

alpha glucose

in PLANTS

made of amylose and amylopectin

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24
Q

describe amylose

A

long unbranched chains of alpha glucose

helical/cylindrical structure due to angles of glycosidic bonds

very compact and therefore its a good molecule for storage as you can fit a lot into a small space

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25
Q

describe amylopectin

A

long branched chains of alpha glucose

loads of side branches allow for easier access for enzymes, to hydrolyse the glycosidic bonds which would release energy

allows for a quick release of energy/glucose

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26
Q

name the features of starch that help its function

A

amylose is a cylindrical/compact molecule, which makes it good for storage as you can fit more into a small space

amylopectin is highly unbranched which allows for enzymes to have easier access to the glycosidic bonds and hydrolyse them for a QUICKER release of glucose

starch is insoluble in water, therefore water cant enter the cells via osmosis and cause them to swell

starch is a large molecule and can’t leave the cell

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27
Q

describe glycogen and its function

A

how ANIMALS store excess glucose/ acts as an energy store

alpha glucose

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28
Q

name the features of glycogen that help its function

A

extremely branched, allows for a quick release of stored glucose as enzymes have easier access to hydrolysing the glycosidic bonds

very compact molecule, so its good for storage

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29
Q

describe cellulose and its function

A

used for structural support, ex in the cell walls of plants

beta glucose

beta glucose molecules form straight cellulose chains, these are joined by (weak) hydrogen bonds which form MICROFIBRILS (strong fibres)

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30
Q

name the features of cellulose that help its function

A

cellulose is made of strong fibres/ microfibrils which provide structural support for cells, ex - in plant cell walls

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31
Q

describe the iodine test for STARCH and how to identify a positive and negative result

A

add iodine dissolved in potassium iodide to the test sample

+ result = blue black colour, starch = present in test sample

  • result = browny orange colour, starch = not present in test sample

the colour change from browny orange to blue black is for a POSITIVE result only

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32
Q

describe lipids

A

fats/oils

found in all cells

they aren’t polymers as they aren’t made of monomers, they are made of LONG CHAINS OF HYDROCARBONS

ex, hormone testosterone = lipid

2 types of lipids = triglycerides and phospholipids

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33
Q

describe the structure of triglycerides

A

one molecule of glycerol and 3 fatty acids

chemical bond = ester bond

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34
Q

describe the structure of phospholipids

A

one phosphate group, one molecule of glycerol, 2 fatty acids

phosphate group = hydrophilic

chemical bond = ester bond

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35
Q

describe fatty acids

A

have long hydrocarbons tails which cause lipids to be insoluble in water BECAUSE the tails are hydrophobic

structure = RCOOH
R = variable group
COOH = carboxyl/ carboxylic acid

can be saturated or unsaturated

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36
Q

saturated vs unsaturated acids

A

saturated = no double bond between the carbon atoms

‘saturated’ with hydrogen

unsaturated = double bond/s between carbon atoms

causes the chain to kink

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37
Q

what are properties of triglycerides

A

ENERGY STORAGE
hydrocarbon tails of fatty acids contain lots of chemical energy
a large amount of energy released when broken down
because of the fatty acid tails, lipids have 2x energy per gram compared to carbohydrates

INSOLUBLE IN WATER
no effect of the water potential of the cell
if there was an effect on cell WP, then water could enter the cell via osmosis and cause the cell to swell

INSOLUBLE IN WATER
triglycerides bundle together as insoluble droplets because fatty acid tails are hydrophobic, therefore the tails face inwards to shield themselves from water

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38
Q

what are the properties of phospholipids

A

CELL MEMBRANES
form the phospholipid bilayer
function - control what enters and leaves the cell
phospholipid head = hydrophilic
phospholipid tails = hydrophobic

causes the formation of a double layer and also causes the centre of the bilayer to be hydrophobic and water soluble substances cant easily pass AND the membrane acts as a barrier

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39
Q

describe emulsion test and how to identify a POSITIVE and NEGATIVE result

A

shake the test substance with ethanol for a minute

pour into water

+ result = milky emulsion and more milky = more lipids present

  • result = NO milky emulsion
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40
Q

what if the test sample if food for an emulsion test

A

dissolve the food in ethanol

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41
Q

name a precaution for the emulsion test

A

ethanol is flammable, therefore do the test away from any open flames

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42
Q

what are proteins

A

made of 1 or more polypeptide chains

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43
Q

what are the monomers of proteins

A

amino acids

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44
Q

what is a dipeptide

A

2 amino acids joined

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45
Q

what is a polypeptide

A

more than 2 amino acids joined

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46
Q

describe the general structure of amino acids

A

central carbon is attached to R, COOH and H2N
R - variable group
COOH - carboxyl group/ carboxylic acid
H2N - amino group/amine

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47
Q

how many total amino acids are there

A

total of 20 amino acids amongst all living things, differ through their R/variable group

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48
Q

describe the formation of dipeptides and polypeptides

A

for dipeptides, amino acid+amino acid = dipeptide

join together via a condensation reaction, involving the loss of a water molecule and the formation of a peptide bond

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49
Q

describe the condensation reaction between 2 amino acids to form a dipeptide

A

the hydroxide from the carboxyl group from one amino acid AND the hydrogen from the amine, is released to release a water of molecule

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50
Q

describe how the dipeptide would look like after a condensation reaction, showing the peptide bond

A

central carbon bonded to a double bond O, on top as the hydroxide from the amino acid was lost through condensation

H on top of N in the second amino acid, as one of the hydrogen atoms was lost in the condensation reaction

peptide bond represented by the line between the C double bonded to the O, from the first amino acid, to the N in the second amino acid

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51
Q

what are the 4 levels in the structure of protein

A

primary
secondary
tertiary
quaternary

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52
Q

describe the primary structure of a protein

A

the sequence/order of amino acids in the polypeptide chain

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53
Q

describe the secondary structure of a protein

A

hydrogen bonds form between the amino acids in the polypeptide chain

the PP chain either coils into an alpha helix or folds into a beta pleated sheet

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54
Q

describe the tertiary structure of a protein

A

further coiling or folding

hydrogen and ionic bonds and disulfide bridges form

final 3D structure of a protein only made of 1 PP chain

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55
Q

how do disulfide bridges form

A

when 2 molecules of the amino acid ‘cysteine’ come close together, the sulfur atom in one molecule of cysteine and the sulfur atom in the other molecule of cysteine

D bridge is between 2 sulfur atoms

SULFur = diSULFide

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56
Q

describe the quartnery structure of a protein

A

how multiple, more than 1, PP chains are assembled

held together by different bonds

final 3D structure for proteins made of more than 1 PP chain

ex, insulin, collagen and haemoglobin

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57
Q

describe the relationship between the shape of the protein and its function

A

the shape of a protein determines its function

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58
Q

how is the relationship between shape and function demonstrated by HAEMOGLOBIN

A

shape - compact + soluble

function - good for carrying oxygen around the body

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59
Q

how is the relationship between shape and function demonstrated by ENZYMES

A

shape - spherical shape as the PP chains are tightly folded + soluble

have roles in metabolism, ex - digestive enzymes break down large molecules (soluble)

some enzymes help in the synthesis of large molecules

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60
Q

how is the relationship between shape and function demonstrated by ANTIBODIES

A

shape - made of 2 light (short) and 2 heavy (long) PP chains bonded + have variable regions where the amino acid sequences vary greatly

function - found in the blood and involved in the immune response

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61
Q

how is the relationship between shape and function demonstrated by TRANSPORT PROTEINS

A

shape - contain hydrophobic and hydrophilic amino acids which causes the protein to fold up and form a channel

function - to transport molecules and ions across the membrane + found in the cell membranes

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62
Q

how is the relationship between shape and function demonstrated by STRUCTURAL PROTEINS

A

shape - long PP chains lying parallel to eachother with cross links between them + physically strong

function - ex, in collagen (protein found in connective tissue) there are 3 PP chains tightly coiled together which causes the so be strong and allows them to be great supportive tissue

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63
Q

describe the process of a biuret test for proteins

A

add a few drops of sodium hydroxide - ensures the test sample is alkaline

add copper (||) sulfate solution

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64
Q

how do you identify a positive result in a biuret test

A

if the solution turns purple

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65
Q

how do you identify a negative result in a biuret test

A

if the solution stays blue

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66
Q

what are enzymes

A

proteins

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67
Q

describe the function of enzymes

A

act as biological catalysts to speed up chemical reactions

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68
Q

what are the 2 levels enzymes can catalyse metabolic reactions

A

cellular, ex - respiration

organism as a whole - ex, digestion in mammals

69
Q

how can enzymes affect structures in an organism

A

they are involved in the production of collaged which is an important protein in the CONNECTIVE TISSUES of animals

70
Q

how can enzymes affect the functions in an organism

A

they are involved in redox reactions in respiration

71
Q

name the 2 types of enzymes action

A

intracellular - within cells

extracellular - outside of cells

72
Q

describe the importance of the active site in enzymes

A

the active site has a specific shape

substrate molecules bind to the active site of the enzyme

73
Q

what level of structure in proteins causes enzymes to be highly specific

A

the tertiary structure

it determines the shape of the active site

74
Q

what is the minimum amount of chemical energy needed to start the reaction

A

activation energy

75
Q

how is activation energy usually provided

A

as heat

76
Q

what do enzymes do to the activation energy and what impact does this have on the reaction

A

enzymes decrease the amount of activation energy needed

causes reactions to happen at a lower temperature, because activation energy is usually provided as heat, compared to without an enzyme

this speeds up the reaction

77
Q

what forms when a substrate fits into the active site of an enzyme

A

an enzyme-substrate complex

78
Q

give and explain 2 ways how the formation of an enzyme substrate complex lowers the activation energy

A

if 2 substrate molecules need to be joined, being attached to the enzymes holds them closer together which REDUCES any repulsion between the substrate molecules which allows them to bond more easily

if the enzyme is catalysing a breakdown reaction, then the substrate fitting into the active site puts a strain on bonds in the substrate which causes the substrate molecule to break up more easily

79
Q

describe the lock and key model of enzyme action

A

enzyme = lock
substrate = key

substrate fits into the enzyme perfectly as their shapes are COMPLEMENTARY to each other

the substrate is able to attach to the active site of the enzyme through random successful collisions, which forms a enzyme-substrate complex

when the products are released, the active site shape goes back to how it originally was and is able to create a new enzyme substrate complex

80
Q

what new evidence brought to light caused scientists to come up with a new model of enzyme action

A

they realised the lock and key model didnt present the full story

new evidence - showed the E-S complex changed shape slightly to complete the fit, to lock the substrate even more tightly to the enzyme

81
Q

what is the name of the current enzyme action model

A

the ‘induced fit’ model

82
Q

describe the induced fit model

A

the substrate and active site aren’t completely complementary, the shape of the active site slightly changes shape to be fully complementary

the formation of the E-S complex involves the enzyme moulding around the substrate which puts a strain on the bonds and lowers the activation energy

when the products are removed, the active site of the enzyme returns to its original shape and can bind to the next substrate molecule

83
Q

why are enzymes very specific

A

their properties are related to their tertiary structure

enzymes are very specific as they will usually only catalyse one reaction, ex - maltase only breaks down maltose BECAUSE only one complementary substrate will fit into the active site

this is because each different enzyme has a different tertiary structure and therefore a different shaped active site

84
Q

what would happen if the substrate shape doesn’t match the shape of the active site

A

an E-S complex wont be formed

the reaction wont be catalysed

85
Q

what determines the active sites shape

A

the enzymes tertiary structure, which is determined by the enzymes primary structure

86
Q

what happens if the tertiary structure of the protein is altered in any way

A

the shape of the active site will change, this would cause the substrate to no longer fit into active site

no E-S complex will be created and enzyme can no longer carry out its function

87
Q

name factors that can alter the tertiary structure

A

changes in pH

changes in temperature

a mutation occurring in the gene that determines the primary structure of the protein

88
Q

how does temperature affect enzyme activity

A

too low - not enough kinetic energy for successful collisions between the enzyme and substrate, no E-S complex formed so the reaction cant be catalysed

too high - the enzymes molecules vibrate and this vibration breaks some of the bonds that hold the enzymes in shape, the active site changes shape and no E-S complex can be created and the enzyme is DENATURED

88
Q

name and describe the 2 ways enzyme activity can be measured

A

HOW FAST THE PRODUCT IS MADE - the product is different molecules than what the reaction starts with,

by measuring the amount of end product present at different times of the experiment the rate of reaction can be measured

HOW FAST THE SUBSTRATE IS BROKEN DOWN - to produce end products in a reaction the substrate molecules have to be used up,

measuring the amount of substrate molecules left at different times during the experiment the rate of reaction can be calculated

89
Q

what does denatured mean

A

it no longer functions as a catalyst

it is a permanent change in most cases

not only if temp, pH is too high but also if its too low

90
Q

what is the optimum pH value for human enzymes

A

most human enzymes work best at the pH of 7

however, the enzyme PEPSIN works best at pH 2 and is a human enzyme found in the stomach

90
Q

what is the optimum temperature of enzymes in humans

A

around 37 degrees c

some enzymes, like those in biological washing powders can work well at 60 degrees c

91
Q

what is the effect of pH being too low or too high, on enzyme activity

A

the H+ and OH- ions found in acids and alkalis, can disrupt the ionic and hydrogen bonds which hold the enzymes tertiary structure in place

causes the enzyme to become denatured and the active site shape to change

92
Q

what is the effect of the substrate concentration being too low or too high

A

the higher the substrate concentration, the faster the reaction AS more substrate molecules means more successful collisions between the substrate and enzyme, therefore more active sites are occupied by substrate molecules

having a low substrate concentration means not all active sites are occupied and the rate of reaction is low

only has an effect until a ‘saturation’ point - where all the active sites are occupied

after the saturation point is reached, all the active sites are full and adding more substrate molecules makes no difference

93
Q

what is the effect of enzyme concentration being too low or too high

A

the more enzyme molecules present in a solution, the more likely there is to be a successful collision between the E and the S and forming an E-S complex

increasing the concentration of the enzyme increases the rate of reaction

if the amount of substrate is limited, then there will be a point when there’s enough enzyme molecules to deal with all the available substrate, adding more enzyme has no effect

94
Q

what is the effect of enzyme inhibitors

A

preventing enzyme activity

do this by binding to the enzyme they inhibit

95
Q

what are the 2 types of enzyme inhibition

A

competitive

non-competitive

96
Q

describe how competitive inhibitors decrease the rate of reaction

A

have a similar shape to the shape of substrate molecules

they compete with the substrate molecules to bind to the AS of the enzyme, and no reaction takes place

they block the AS, so no substrate molecules fit in

97
Q

the amount of inhibition of the enzyme is dependent on what 2 factors

A

the relative concentration of inhibitor

the relative concentration of substrate

98
Q

what is the effect of there being a high concentration of inhibitor - COMPETITIVE INHIBITOR

A

will occupy nearly all the AS

low amount of substrate will get to the enzyme

low rate of reaction

99
Q

what is the effect of there being a high concentration of substrate - COMPETITIVE INHIBITOR

A

increased chance of the substrate getting to the AS, before the inhibitor BECAUSE the substrate will out-compete the inhibitor for the AS

increasing the concentration of substrate will increase the rate of reaction, to a certain point

100
Q

explain the way the non-competitive inhibitors function

A

bind to the enzyme AWAY from its AS - binds to the allosteric AS

this causes the AS to change shape, so the substrate molecules can no longer bind to the AS

101
Q

why dont non competitive inhibitors compete with the substrate molecules, to bind to the AS

A

because the substrate and non-competitive inhibitors are different shapes

102
Q

what is the effect of increasing substrate concentration on non-competitive inhibition

A

no effect

enzyme activity is still inhibited, because the AS has changed shape (due to the non-competitive inhibitor binding to the allosteric site) and substrate molecules are no longer complementary and wont fit in and no E-S complexs can be formed

103
Q

what is the purpose of DNA and RNA

A

needed for the function of living organisms

104
Q

what type of biological molecule is DNA and RNA

A

nucleic acids

105
Q

where are DNA and RNA found

A

all living cells

106
Q

what do DNA and RNA carry

A

info

107
Q

DNA function

A

DNA = deoxyribonucleic acid

used to store genetic info (all instructions needed to grow and develop from a fertilised egg -> a fully grown adult)

108
Q

RNA function

A

RNA = ribonucleic acid

similar in structure to DNA

transfer genetic info form DNA -> ribosomes

109
Q

function of ribosomes

A

bodys ‘protein factories’

read RNA to make polypeptides = translation

110
Q

what are ribosomes made of

A

RNA and proteins

111
Q

what is the monomer of DNA and RNA

A

nucleotides

112
Q

what are nucleotides made of (DNA/RNA)

A

phosphate group

pentose sugar (sugar with 5 carbon atoms)

nitrogen containing base

113
Q

how does the pentose sugar in nucleotides differ for DNA and RNA

A

for DNA, the pentose sugar is DEOXYRIBOSE

for RNA, the pentose sugar is RIBOSE

114
Q

name the nitrogen containing bases for DNA

A

adenine - A

thymine - T

cytosine - C

guanine - G

115
Q

name the nitrogen containing bases for RNA

A

adenine - A

uracil - U

cytosine - C

guanine - G

116
Q

describe polynucleotide structure

A

many nucleotides join together to form polynucleotide strands/chains

nucleotides join via a condensation reaction

condensation reaction between PHOSPHATE GROUP of one nucleotide and the PENTOSE SUGAR of the other nucleotide

chemical bond formed = phosphodiester bond, 2 ester bonds joined to the phosphate group

loss of water molecule as it is a condensation reaction

chain of phosphates and sugars = sugar-phosphate backbone

117
Q

describe the structure of DNA

A

double helix, DNA molecule = 2 separate strands wind around eachother to form a spiral

DNA strands = polynucleotides, = lots of polynucleotides joined up together in a long chain

very long and coiled up tightly, = lots of genetic info can fit into a small space in the cells nucleus

118
Q

what is the structure of the DNA nucleotide

A

phosphate group
pentose sugar - deoxyribose
nitrogen containing base - A, T, C or G

A = adenine
T = thymine
C = cytosine
G = guanine

119
Q

describe complementary base pairing

A

the 2 DNA polynucleotide strands join together by hydrogen bonds between bases

each base can only pair to their complementary base, A - T and C - G

always equal amounts of A+T and C+G in the DNA molecule

complementary base pairing = specific base pairing

120
Q

how many hydrogen bonds are between adenine and thymine

A

2

121
Q

how many hydrogen bonds are between cytosine and guanine

A

3

122
Q

why are the 2 polynucleotide strands antiparallel

A

they run in opposite directions so they can twist to form a DNA double helix

123
Q

describe the structure of RNA

A

made of RNA nucleotides, = contain RIBOSE sugar, a phosphate group and 4 diff bases (A, U, C and G)

form a polynucleotide strand with a sugar-phosphate backbone

124
Q

how is the structure of RNA different to the structure of DNA

A

RNA nucleotides contain RIBOSE as their pentose sugar, while DNA nucleotides contain DEOXYRIBOSE as their pentose sugar

bases in RNA are A, U, C and G
bases in DNA are A, T, C and G

RNA is a SINGLE polynucleotide chain, DNA is a DOUBLE helix (2 polynucleotide chains wrapped around eachother)

RNA strands = much shorter than DNA polynucleotide strands

125
Q

describe how DNA is the carrier of the genetic code

A

DNA was first observed in the 1800s, but the majority of scientists doubted it could carry the genetic code because of its simple chemical composition

some scientists argued that the genetic code must be carried by proteins and they had more chemical variation

1953 - experiments had shown that DNA was the carrier of the genetic code

126
Q

which scientists determined the structure of DNA

A

watson and crick

127
Q

is dna able to replicate itself

A

yes and it does so regularly

128
Q

why does DNA replicate

A

replicates before cell division, mitosis, so each new cell has the full amount of DNA

129
Q

what is the name of the method by which DNA replicates

A

semi - conservative replication

130
Q

why is it called semi conservative replication and what does that mean

A

half the strands in the NEW DNA molecule are from the ORIGINAL DNA molecule

ensures there is GENETIC CONTINUITY between generations of cells, ex -> the cells produced by cell division inherit their genes from their parent cells

131
Q

how is dna replicated

A

DNA helices BREAKS the hydrogen bonds between the bases on the 2 DNA strands

helix unwinds to form 2 single strands

each single strand = template for new strand

free floating DNA nucleotides are attracted to their complementary exposed bases (A-T and C-G) on the template strand via COMPLEMENTARY BASE PAIRING

condensation reactions join the nucleotides of the new strand together, catalysed by DNA POLYMERASE - HYDROGEN bonds form between the bases on the ORIGINAL and NEW DNA strands

each new DNA molecule = one strand from ORIGINAL DNA molecule + one NEW strand

132
Q

describe the action of DNA polymerase

A

each end of DNA is slightly different in structure, one end = 3’ and the other end = 5’

3’ = 3 prime
5’ = 5 prime

during DNA replication, the active site of the enzyme DNA POLYMERASE is only complementary to the 3’ end = DNA nucleotides can only be added to the 3’ end

new strand is made in a 5’ to 3’ friction and DNA POLYMERASE moves down the strand in a 3’ to 5’ direction

133
Q

describe the action of DNA polymerase in the DNA molecule during DNA replication

A

the strands in the double helix are anti-parallel, the DNA polymerase working on one template strand, moved in the OPPOSITE direction as the DNA polymerase working on the other template strand

134
Q

which experiment validated watson and cricks theory of the structure of DNA and WHOs experiment was it

A

the semi-conservative method by meselson and stahl validated watson and cricks theory AND also showed how dna replication takes place

135
Q

what would happen if dna was conservative, not semi conservative

A

the original DNA strands would stay together and the new DNA molecules would contain 2 new strands

no genetic continuity

136
Q

describe meselson and stahls experiment proving DNA replication is semi-conservative

A

they used 2 isotopes of nitrogen, as DNA contains nitrogen (nitrogen containing bases)

2 isotopes - heavy nitrogen = 15N
light nitrogen = 14N

2 samples of bacteria were grown for many generations, one in a nutrient broth containing LIGHT nitrogen and the other was grown in a nutrient broth containing HEAVY nitrogen

as the bacteria reproduced (replicated), they took up nitrogen from the broth to make NUCLEOTIDES for the NEW DNA

nitrogen became part of the bacterias DNA

a sample of DNA was taken from each batch of bacteria and spun in a CENTRIFUGE

DNA from HEAVY nitrogen settled lower down in the centrifuge, compared to the DNA from the LIGHT nitrogen BECAUSE ITS HEAVIER

the bacteria grown in the HEAVY nitrogen was taken out and put in a broth containing only LIGHT nitrogen and was left for ONE round of DNA replication

a DNA sample was taken from this and spun in the CENTRIFUGE

if replication was conservative, the original HEAVY DNA would still be together and settle at the bottom while the new LIGHT DNA would settle at the top

if replication was semi conservative, the new bacterial DNA would contain ONE HEAVY DNA STRAND and ONE LIGHT DNA STRAND - and it would settle between where the original light and heavy DNA strands settled in the centrifuge

the DNA settled out in the middle, showing DNA molecules contained a mix of both HEAVY and LIGHT nitrogen meaning the bacterial DNA had replicated semi conservatively in the light nitrogen

137
Q

what is required for all processes and what is the adaption plants and animals made

A

energy is required for ALL life processes

plants and animals are able to store and release energy for this, very IMPORTANT

138
Q

what do plant and animal cells need for biological processes to occur

A

energy

139
Q

why is energy important for plants

A

active transport - transport solutes from their leaves

DNA replication

cell division

protein synthesis

140
Q

why is energy important for animals

A

active transport - to absorb glucose from ileum epithelium -> bloodstream

DNA replication

cell division

protein synthesis

141
Q

describe the purpose of ATP

A

plants and animal cells release energy from glucose through respiration

a cell cant get its energy directly from glucose

in respiration, energy released from glucose is used to make ATP

142
Q

describe the structure of ATP

A

nucleotide base ADENINE

ribose sugar (pentose sugar = 5 carbons)

3 phosphate groups

143
Q

why is ATP called a ‘nucleotide derivative’

A

because ATP is a modified form a nucleotide

144
Q

where does ATP diffuse when its made

A

to the part of the cell that needs energy

145
Q

where is the energy stored in ATP

A

stored in the HIGH ENERGY BONDS between the phosphate groups

146
Q

how is energy released in ATP

A

via hydrolysis reaction

147
Q

describe how ATP is broken down for its use

A

when energy is needed by a cell

ATP broken down via hydrolysis reaction

ATP broken down into ADP (adenosine diphosphate) + Pi (inorganic phosphate)

phosphate bond broken and energy is released

hydrolysis reaction catalysed by enzyme ATP HYDROLASE

148
Q

what are other uses of ATP when its been hydrolysed

A
  • can be ‘coupled’ to other reactions that require energy
  • allows released energy to be used directly to make the coupled reaction happen, INSTEAD of ATP being lost as heat/thermal energy
  • the released inorganic phosphate can be used
  • Pi can be added to another compound
  • ‘phosphorlylation’
  • often makes the compound more reactive
149
Q

describe the resynthesis of ATP

A

ATP can be resynthesised in a condensation reaction between ADP and Pi

happens during respiration and photosynthesis

catalysed by ATP synthase

150
Q

define ATP

A

ATP IS NOT ENERGY

ATP = store of energy

energy is used to make ATP

energy is released when ATP is hydrolysed to ADP and Pi

151
Q

what is water essential for

A

life

152
Q

describe the importance of water

A

vital to living organisms and makes up around 80% of a cells contents

metabolite in important reactions - ex, condensation and hydrolysis

solvent so some substances dissolve in it and most metabolic reactions take place in solution - ex, cytoplasm of eukaryotic and prokaryotic cells

has a high latent heat of vaporisation and high specific heat capacity - helps with temperature control

water molecules are very cohesive (stick together), helps transport in plants and transport in other organisms

153
Q

describe the structure of water

A

shape of a water molecule is assymetrical

molecule is dipole, oxygen atom carries a small NEGATIVE charge while the hydrogen atoms carry a small POSITIVE charge

negative and positive charges balance, water overall has NO net charge, BUT water is still a polar (dipole) molecule

154
Q

what does dipole mean

A

di = 2
pole = charge

2 different charges
H+ = slight positive charge
O = slight negative charge

155
Q

name the 5 properties of water

A

important metabolite

good solvent

high latent heat of vaporisation

can buffer changes in temp

very cohesive

156
Q

how is water an important metabolite and how this is important for organisms

A

most metabolic reactions involve condensation or hydrolysis

hydrolysis - requires a molecule of water to break a bond

condensation - releases a molecule of water as a new bond forms

ex, amino acids joined together to make polypeptides via CONDENSATION reaction

ex, energy from ATP is released via HYDROLYSIS reaction

157
Q

describe how water is a good solvent and how this is important for organisms

A

a lot of important substances in biological reactions are ionic, ex - salt

ionic - made from one positive ion and one negative ion

water = polar, slightly positive charged end will be attracted to the negative ion WHILE the slightly negative charged end will be attracted to the positive ion

ions will be surrounded by water, therefore they will dissolve

living organisms can take up useful substances, like mineral ions, dissolved in water AND these dissolved substances can be transported around the organisms body

158
Q

describe waters high latent heat of vaporisation and how this is important for organisms

A

water evaporates/vaporises when the hydrogen bonds holding water molecules together are BROKEN, this allows water molecules on the surface of water to escape into the air as a GAS

takes a LOT of energy (heat) to break the hydrogen bonds between water molecules, a lot of energy is used for water to evaporate

useful for living organisms because it means they can use water loss through evaporation to cool down, without losing too much water

when water evaporates it carries away heat energy from a surface, this means it cools the surface and helps to lower the temperature

ex- when humans sweat to cool down

159
Q

describe how water can buffer/resist changes in temp and how this is important for organisms

A

H bonds give water a HIGH SPECIFIC HEAT CAPACITY, = energy needed to raise temp of 1 gram of substance by 1 degree c

when water is heated a lot of the heat energy is used to break the H bonds between the water molecules, = less heat energy available to increase the temp of water

it takes a lot of energy to heat up water

useful for living organisms as it means water doesn’t experience rapid temp changes, = makes water a good habitat as temp under water would be more stable than temp on land

water in organisms also remains fairly stable, = helps maintain a constant internal body temp

160
Q

describe how water is very cohesive and how this is important for organisms

A

cohesion = attraction between molecules of the same type, ex - 2 water molecules

water molecules are very cohesive (stick together) because they are polar

strong cohesion helps to make water flow, makes it good for transporting substances - ex, how water travels in columns up the xylem in plants

strong cohesion also means water has HIGH SURFACE TENSION when it comes into contact with air

this why sweat forms droplets which evaporate from the skin to cool the organism down

reason why pond skaters and other insects can ‘walk’ on the surface of a pond

161
Q

what is an ion

A

an atom or a group of atoms that has an electric charge

162
Q

what is the name of an ion with a positive charge and what are examples

A

cation

sodium, Na+
calcium, Ca 2+

163
Q

what is the name of an ion with a negative charge and what are examples

A

anion

chlorine, CL-
phosphate, PO4 3-

164
Q

what is an inorganic ion

A

one that doesn’t contain carbon, there are some exceptions

found in the cytoplasm of cells and in the body fluids of organisms

each ion has a specific role depending on its properties

an ions role determines whether its found in high or low concentrations

165
Q

what ions are in haemoglobin and what’s their role

A

iron ions = Fe 2+

  • haemoglobin is a large protein which carries oxygen around the body, in red blood cells
  • made of 4 PP chains, each chain has a iron ion in the centre
  • Fe 2+ that actually binds to the oxygen in haemoglobin
  • when oxygen is bound, the Fe 2+ ion temporarily becomes an Fe 3+ ion UNTIL the oxygen is released
166
Q

what is the role of hydrogen ions

A

hydrogen ions = H+

  • pH is calculated based on the concentration of hydrogen ions in the environment
  • more H+ ions present = lower the pH = more acidic the environment
  • enzyme controlled reactions are all affected by pH
167
Q

what is the role of sodium ions

A

sodium ions = Na+

  • a molecule of glucose or an amino acid can be transported into a cell, across cell membrane, with sodium ions
  • process called co-transport
168
Q

what is the role of phosphate ions

A

phosphate ions = PO4 3-

  • when a phosphate ion is attached to another molecule, its called a phosphate GROUP
  • DNA, RNA and ATP all contain phosphate groups
  • the bonds between phosphate groups store energy in ATP, which is released when ATP is hydrolysed
  • the phosphate groups in DNA and RNA allow nucleotides to join up to form the polynucleotides

AS BIO - BIOLOGICAL MOLECULES (4 decks)

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