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Biology > Water (A1.1) + Nucleic Acids (A1.2) + Carbs and Lipids (B1.1) + Proteins (B1.2) > Flashcards

Water (A1.1) + Nucleic Acids (A1.2) + Carbs and Lipids (B1.1) + Proteins (B1.2) Flashcards

1
Q

Define a hydrogen bond

A

force when a slightly positive hydrogen atom in one polar molecule is attracted to slightly negative atom of another polar molecule

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2
Q

Buoyancy as a physical property of water (2)

A

buoyancy = force exerted upward by fluid which counteracts gravity

density of object < density of liquid = buoyancy force > gravity = object will float

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3
Q

Why does ice float on water (2)

A

ice is less dense as water

pattern of hydrogen bonding of ice is less dense

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4
Q

Viscosity as a physical property of water

A

pure water has low viscosity - hydrogen bonds are weak so not as much internal friction

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5
Q

Define cohesion

A

ability of water molecules to stick together

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6
Q

Cohesion of water for water transport in plants (5)

A

water is sucked upwards in continuous columns

column of water under tension from both ends

tension from roots due to attraction between soil + water

tension from leaves as water lost by evaporation + attraction between water and leaf cell walls

water moves upwards because force in leaves > force in roots

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7
Q

Explain surface tension of water (2)

A

cohesion between water molecules > attraction between water and floating object

object must break hydrogen bonds to break the surface of water

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8
Q

Define adhesion for water (2)

A

hydrogen bonds forming between water + surface of solid composed of polar molecules

allows water to stick to other objects

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9
Q

Define capillary action

A

the ability of a liquid to flow through a narrow tube without external forces

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10
Q

Why water is a good solvent (5)

A

polar nature of water molecule forms shells around both charged + polar molecules

prevents molecules from clumping together so they remain in solution

water’s partially negative oxygen pole attracted to positive ions

water’s partially positive hydrogen pole attracted to negative ions

both dissolve

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11
Q

Define hydrophilic

A

substances chemically attracted to water

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12
Q

Examples of hydrophilic substances (2)

A

glucose

positive or negative ions (e.g sodium + chloride ions)

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13
Q

Define hydrophobic (3)

A

substances not attracted to water

more attracted to other hydrophobic substances

insoluble in water

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14
Q

Examples of hydrophobic substances (2)

A

non-polar molecules (not positive or negative)

lipids

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15
Q

Metabolism in water solvent property (2)

A

solutes can move + interact

allows for substrates to touch the active sites of enzymes

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16
Q

Thermal conductivity as a property of water

A

high thermal conductivity = good at absorbing/transferring heat

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17
Q

Define thermal conductivity

A

the rate at which heat passes through a material

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18
Q

Define viscosity (3)

A

how easily a fluid is able to flow

more viscosity –> more friction + resistance to flow

due to internal friction when on part of a fluid moves faster relative to another part

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19
Q

Applications of water’s thermal conductivity

A

high water content in blood –> can carry heat from parts of body to parts that need more heat or parts that dissipate heat

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20
Q

Define specific heat capacity

A

energy required to raise the temperature of 1g of material by 1 C

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21
Q

Specific heat capacity as a characteristic of water (2)

A

increase in temperature must have hydrogen bonds broken with energy

must lose an equal amount of energy to cool down

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22
Q

Applications of specific heat capacity of water (2)

A

aquatic habitats are more thermally stable

helps mammals maintain constant body temperatures

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23
Q

Why water is able to be retained on earth (2)

A

distance between sun and earth = temperatures are not high enough to vaporize water

strong gravity = oceans is held to surface, gases kept within atmosphere

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24
Q

Define the Goldilocks Zone (2)

A

habitable zone around a star

location depends on size of star, amount of energy it emits, size of planet

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25
Q

Parts of nucleotides (3)

A

pentose sugar with 5 carbon atoms

phosphate group : acidic and negatively charged part of nucleic acids

base that contains nitrogen - has either 1 or 2 rings of atoms in its structure

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26
Q

Phosphate group nucleotide diagram

A

O-
|
O- – P – O –
||
O

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27
Q

Deoxyribose sugar nucleotide diagram

A

– CH2
| O
CH CH – N
CH CH
| |
OH OH

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28
Q

How are nucleotides linked together

A

covalent bonds formed between phosphate of one nucleotide and the pentose sugar of another

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29
Q

What is the DNA and RNA backbone made of

A

chain between sugar and phosphate

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30
Q

Bases in DNA (4)

A

Adenine (A)

Cytosine (C)

Guanine (G)

Thymine (T)

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31
Q

Bases in RNA (4)

A

Adenine (A)

Cytosine (C)

Guanine (G)

Uracil (U)

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32
Q

Links between bases of DNA (2)

A

Adenine forms hydrogen bonds with thymine

guanine forms hydrogen bonds with cytosine

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33
Q

Strands of DNA nucleotides in relation to each other (2)

A

(anti)parallel - parallel but run in opposite directions

one strand ends with phosphate group other ends with deoxyribose (pentose sugar)

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34
Q

Differences between DNA and RNA (3)

A

DNA is double-stranded, RNA is single-stranded

RNA has uracil instead of thymine in DNA

pentose sugar of DNA is deoxyribose, pentose sugar of RNA is ribose

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35
Q

How do RNA nucleotide join together

A

condensation reaction - molecules combine while losing water

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36
Q

What happens in semi-conservative replication of DNA (3)

A

2 strands of double helix separate - hydrogen bonds break

free nucleotides pair with exposed complementary bases

changes 1 DNA molecule into 2 identical ones

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37
Q

Number of possible combinations of DNA bases (2)

A

4^n

where n is the number of bases

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38
Q

Define gene expression (2)

A

process which genetic code in DNA translated into protein

allows DNA to code for proteins

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39
Q

Define codons in genes (2)

A

groups of 3 bases

64 possible codons

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40
Q

Functions of codons in genes (3)

A

most codons specify a particular amino acid

one codon signals that protein synthesis should start

3 codon signal that protein synthesis should stop

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41
Q

Define transcription in genes

A

process where one DNA strand is used as template to produce RNA

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42
Q

How is a gene expressed (3)

A

copying base sequence - copy made using RNA

adenine in RNA pairs with uracil instead of thymine

synthesiszing a protein - base sequence of RNA translated into amino acid sequence of protein

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43
Q

Define translation in DNA

A

process where transcribed RNA is translated by ribosomes to produce proteins

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44
Q

Define a purine (3)

A

Adenine

Guanine

have 2 carbon rings

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45
Q

Number of hydrogen bonds between adenine + thymine

A

2 hydrogen bonds

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46
Q

Number of hydrogen bonds between guanine + cytosine

A

3 hydrogen bonds

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47
Q

Describe the 5’ to 3’ directionality of DNA (3)

A

5 and 3 = 5th + 3rd carbon on pentose

phosphate binds at 5’ and 3’

one strand will start with 5’ and end with 3’, other strand will start with 3’ and end with 5’

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48
Q

Define a pyrimidine (4)

A

Thymine

Cytosine

Uracil

has one ring

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49
Q

Directionality of DNA in DNA replication (2)

A

nucleotides added to the 3’ end of polymer

5’ phosphate of free nucleotide links to 3’ end of growing polymer

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50
Q

Directionality of DNA in DNA transcription (2)

A

nucleotides added to 3’ end of polymer

5’ phosphate of free nucleotide links to 3’ end of growing polymer

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51
Q

Directionality of DNA in DNA translation (3)

A

ribosome reads RNA sequence

ribosome that carries out translation moves along RNA to 3’ end

5’ to 3’ directionality

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52
Q

Why purines are complementary with pyrimidines (3)

A

purine to purine bond length will be too long

pyrimidine to pyrimidine bond length will be too short

complementary base pairing stabilises DNA shape

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53
Q

Appearance of nucleosome (2)

A

length of DNA wrapped twice around cores of 8 histone molecules (2 copies of 4 different histones)

additional histone molecule (H1) reinforces binding of DNA to nucleosome core

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54
Q

How are chromosomes formed from nucleosomes (3)

A

nucleosomes joined together by linker DNA

nucleosomes stacked onto each other

stacks form chromosomes

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55
Q

Purpose of the Hershey-Chase experiment

A

proving that DNA made up genetic material instead of protein

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56
Q

Materials used in the Hershey-Chase experiment (3)

A

virus - T2 bacteriophage

bacteriophage inner DNA coated in radioactive phosphorous

bacteriophage outer protein coated in radioactive sulfur

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57
Q

Hershey-Chase experiment results (3)

A

bacteriophages with radioactive phosphorous infected non-radioactive bacteria, all infected cells became radioactive

next-generation of bacteriophages produced from infected bacteria were all radioactive

bacteriophages coated in radioactive sulfur + virus coats separated = no radioactivity inside infected cell

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58
Q

Describe Hershey-Chase experiment (5)

A

bacteriophage added to bacteria

blender separates bacteriophage capsid from DNA in bacteria

centrifuge separates bacteriophage from virus to allow investigator to detect radiation location

Phosphorous - virus capsid in liquid is not radioactive, bacteria are

Sulfur - viruse capsid in liquid are radioactive, bacteria are not

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59
Q

Chargaff’s experiment (3)

A

extracted DNA from cells + mixed them with acid

acid breaks bonds between pentose sugar + base

bases separated using paper chromatography + concentration of bases measured

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60
Q

Chargaff’s results (2)

A

concentration/amount of adenine equal/similar to thymine

concentration/amount of cytosine equal/similar to guanine

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61
Q

Importance of Chargaff’s experiment (3)

A

hinted at complementary base pairing

helped watson and crick build their double helix model

dispelled tetranucleotide hypothesis

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62
Q

Tetranucleotide hypothesis (2)

A

DNA contains repeating sequence of 4 bases (4 nucleotides occur in equal amounts)

DNA was single-stranded

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63
Q

Define macromolecules

A

molecules composed of a large number of atoms

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64
Q

Main classes of macromolecules in living organisms (3)

A

polysaccharides

polypeptides

nucleic acids

65
Q

Define a disaccharide

A

2 monosaccharides linked together

66
Q

Features of carbon bonds (3)

A

covalent

carbon can bond to 4 atoms

single carbon bonds allow atoms to rotate

67
Q

Shape which chains of carbon atoms can form (2)

A

rings

zig zag shape

68
Q

Condensation Polymerisation (3)

A

two molecules join together

one molecule loses a hydroxyl group (-OH), another loses a hydrogen atom (-H)

causes formation of water

69
Q

Describe a glycosidic bond

A

oxygen atom shared between 2 glucose molecules

70
Q

Define hydrolysis (2)

A

chemical reaction where water is used to break covalent bond between monomers

-OH will attach to one monosaccharide, -H will attach to other

71
Q

Number of carbon atoms for pentose (2)

A

5

e.g ribose

72
Q

Number of carbon atoms for hexose (2)

A

6

e.g glucose, fructose

73
Q

Isomers of glucose (2)

A

alpha-glucose

beta-glucose

74
Q

Orientation of alpha-glucose (2)

A

hydroxyl group (OH) is orientated downward

e.g glycogen + starch

75
Q

Orientation of beta-glucose (2)

A

hydroxyl group (OH) is orientated upward

e.g cellulose

76
Q

Properties of glucose (3)

A

glucose is soluble + small –> easily transported

glucose is chemically stable

yields energy when oxidised

77
Q

Why glucose is soluble (4)

A

soluble because it is polar

contains (-OH) molecules which are polar

oxygen atoms are partially negative

so carbon-hydrogen (C-H) atoms are partially positive

78
Q

Applications of glucose being soluble (2)

A

polar so able to dissolve in water

dissolves in plasma - can be transported in blood, OH groups bond with water in plasma

79
Q

Why is glucose chemically stable (2)

A

ring structure - atoms are bonded to minimise strain + allows for strong covalent bonds

hydroxyl groups - forms bonds with water molecules (stable in aqueous solution) + prevents glucose from undergoing reactions

80
Q

Application of property of glucose being chemically stable (2)

A

improves structural role of cellulose in plants

helpful in starch and glycogen for storage

81
Q

Oxidisation as a property of glucose (3)

A

addition of oxygen to a molecule

loss of hydrogen atom

loss of electrons to another atom/ion

82
Q

Application of glucose property of being easily oxidised (2)

A

oxygen important reactant for cellular respiration

broken down by losing electrons to oxygen to form CO2 and H2O

83
Q

Name 2 types of starch (2)

A

amylose

amylopectin

84
Q

Describe amylose (2)

A

polysaccharide made of glucose monomers linked through alpha-1,4 -glycosidic bonds

helical shaped chain

85
Q

Describe amylopectin (2)

A

polysaccharide made up of glucose monomers linked through alpha-1,4-glycosidic bonds with ocassional 1,6-glycosidic bonds

branched shaped chain

86
Q

Amylopectin property (3)

A

branch shape allows amylopectin to be more packed together - allows for more efficient storage of glucose

adding + removing glucose is quicker since branch shape has more ends

major component of starch

87
Q

Starch properties (2)

A

compact in structure due to branching and coiling - efficient storage for small space

insoluble due to large size - can store lots of glucose, ensures that water is not drawn in

88
Q

Describe maltose

A

disaccharide formed from 2 alpha-glucose molecules joined by a glycosidic bond

89
Q

Describe sucrose

A

alpha-glucose molecule and fructose molecule joined by a glycosidic bond

90
Q

Describe lactose (2)

A

glucose + galactose molecule

joined by glycosidic bond

91
Q

Describe the structure of glycogen (2)

A

linear glucose chains linked through alpha 1,4 glycosidic bonds and 1,6 glycosidic bonds

forms compact coiled structure

92
Q

Features of glycogen (2)

A

insoluble due to large molecular size - does not affect osmotic concentration of cells

branched structure - can be easily hydrolysed to produce glucose

93
Q

Cellulose characteristics (3)

A

structural sugar in plants

strong - hydrogen bonds between chains create lattice structure

1,4 glycosidic bond

94
Q

Cellulose structure (4)

A

straight chain of beta-molecules

B-glucose is inverted so that -OH groups are together

hydrogen bonds form between chains (polarity between O in glycosidic bond + H in glucose)

microfibrils form - bundles of cellulose chains

95
Q

Define glycoproteins

A

proteins that have one or more carbohydrates attached to them

96
Q

Function of glycoproteins (4)

A

Cell-cell recognition

act as receptors on surface of cells

can act as ligands

structural support of cells + tissue

97
Q

Role of glycoproteins in cell to cell recognition (2)

A

acts as markers on the surface of cells so they can be identified

e.g immune cells attack foreign cells with different glycoproteins

98
Q

Role of glycoproteins as receptors (3)

A

act as receptors on cell surfaces

receive signals from other cells or molecules

e.g insulin binds to glycoproteins on surface of body cells

99
Q

Role of glycoproteins as ligands

A

ligands - molecules that bind to receptors to initiate a biological response

100
Q

Glycoprotein role in ABO blood groups (2)

A

red blood cells have glycoproteins : oligosaccharides called O, A, B

blood with glycoprotein A/B will be rejected by a person who does not produce it

101
Q

What blood type does not cause rejection problems and why (2)

A

O

has same structure as A and B but with one monosaccharide less

102
Q

Features of lipids (3)

A

hydrophobic + insoluble in water - non-polar

dissolve in non-polar solvents - non-polar solvents have similar polarity to lipids

contains carbon, hydrogen, oxygen

103
Q

Name of solid lipids at room temperature

A

fats

104
Q

Name of liquid lipids at room temperature

A

oils

105
Q

Define a tryglyceride (4)

A

non-polar macromolecule + most common type of lipid

formed from one molecule of glycerol + 3 fatty acids

glycerol stays the same but there are different fatty acids

fatty acids = carboxyl groups (COOH) with a hydrocarbon tail

106
Q

Name of bond formed between glycerol and fatty acid

A

ester bond

107
Q

Define a phospholipid

A

glycerol molecule with a phosphate group and 2 fatty acids

phosphate head is hydrophilic when fatty acids are hydrophobic

108
Q

Define saturated fatty acids (3)

A

straight shape due to no double bonds between carbon atoms

carbon atom in hydrocarbon bonds to 4 atoms

fatty acids can pack together, forming solid at room temp.

109
Q

Define unsaturated fatty acids (3)

A

hydrocarbons have one or more double bonds

causes bends in shape

liquid at room temp. - bends make it difficult for molecules to pack together

110
Q

Types of unsaturated fatty acids (2)

A

monounsaturated

polyunsaturated

111
Q

Define monounsaturated fatty acids (3)

A

have one double bond in hydrocarbon chain

causes a bend in the chain

liquid state at room temp. - bends make it difficult for molecules to pack together

112
Q

Define polyunsaturated fatty acids (3)

A

have 2 or more double bonds in hydrocarbon chain

causes multiple bends in chain

liquid state at room-temp - bends make it more difficult for molecules to pack together

113
Q

Unsaturated fatty acids vs saturated fatty acids (melting point)

A

U have lower melting points than S - more double bonds = lower melting point

114
Q

Why doe unsaturated fatty acids have lower melting points (2)

A

double bonds disrupt packing of fatty acid molecules

makes them easier to break apart

115
Q

Terms used to describe different arrangement of unsaturated fatty acids (2)

A

cis

trans

116
Q

Define cis unsaturated fatty acids (2)

A

hydrogen atoms attached to carbon atoms around double bond are on same side

creates bend

117
Q

Define trans unsaturated fatty acids (2)

A

hydrogen atoms attached to carbon atoms around double bond are on different sides

linear shape + less flexible than cis

118
Q

Trans fats vs cis fats (2)

A

cis occurs in nature, trans produced artificially

cis has lower melting points than trans

119
Q

Tryglycerides function/characteristics (4)

A

energy storage - chemically stable so energy not lost

used as insulators to retain heat

liquid at body temperature - can act as shock absorbers

release twice as much energy per gram in respiration than carbs

120
Q

Define a phospholipid bilayer (4)

A

double layer of phospholipids

phospholipid bilayers can form when phospholipids are placed in water

hydrophobic fatty acids will orient towards each other

hydrophilic phosphate + glycerol will orient towards water

121
Q

Features of steroids (4)

A

lipids

hydrophobic - as they are mainly hydrocarbons

have 4 carbon rings

able to pass through phospholipid bilayer

122
Q

Functions of steroids (2)

A

provide phospholipid bilayer with stability + flexibility

role in signalling

123
Q

Describe the structure of an amino acid (5)

A

amino group NH2 (basic)

carboxyl group COOH (acidic)

hydrogen atom

central alpha carbon atom

side chains called R groups

124
Q

Features of the R-group in amino acids (2)

A

R-groups vary + make amino acids different from each other

affects the way the amino acid bonds with another amino acid

125
Q

Define a dipeptide

A

2 amino acids linked by a condensation reaction

126
Q

How do amino acids link with one another (2)

A

carboxyl group reacts with amino group

condensation reaction - bond formed between C and N + H2O produced as by-product

127
Q

Name of bond between amino acids

A

peptide bond (type of covalent bond)

128
Q

Number of different amino acids

A

20

129
Q

Define essential amino acids (2)

A

amino acids which the body cannot produced + must be obtained from diet

9/20

130
Q

Define non-essential amino acids (2)

A

amino acids which can be produced by the body

11/20

131
Q

Number of possible amino acid sequences for a polypeptide (3)

A

20^n

20 possible amino acids to be linked

n = number of amino acids

132
Q

Importance of an amino acid order

A

gives the protein its function

133
Q

Why does temperature cause protein denaturation (2)

A

high temperatures can break weak hydrogen bonds holding proteins together

protein will unfold + lose its function

134
Q

Why does pH cause protein denaturation (3)

A

high pH = excess H+ can make it difficult to form hydrogen bonds + affecting electronegativity

low pH = lack of H+ reduce number of hydrogen bonds

denaturation = will alter protein shape

135
Q

Number of codons to code for an amino acid

A

64

136
Q

Different types of R-groups (3)

A

charged R-groups which form ionic bonds

R-groups with sulphur atoms that form disulphide bridges

hydrophilic + hydrophobic - some are polar or charged

137
Q

Describe the primary structure of proteins (3)

A

sequence of amino acids

peptide bonds between carboxyl + amine group

determines shape of protein - sequence determines how polypeptide chain will fold

138
Q

Describe the secondary structure of proteins (2)

A

the folding patterns that occur within the polypeptide chain

hydrogen bonds between O and H atoms on adjacent amino acids form structure

139
Q

Name 2 types of secondary structure (2)

A

alpha helix

beta pleated sheet

140
Q

Features of alpha-helix secondary structure (2)

A

polypeptide chain forms helical shape

hydrogen bond forms between amine hydrogen of one amino acid + carboxyl oxygen of another 4 residues away

141
Q

Features of beta-pleated sheet secondary structure (2)

A

hydrogen bonds form between polypeptide chains parallel to each other

form pleated sheet shape due to tetrahedral bond angles

142
Q

Define the tertiary structure of proteins (2)

A

folding of the polypeptide chain into a 3-dimensional structure

stabilized by interactions between R-groups of amino acids

143
Q

Describe tertiary structure hydrogen bonds between R-groups

A

hydrogen bonds form between slightly positive hydrogen and slightly negative O or N

144
Q

Describe tertiary structure ionic bonds between R-groups (4)

A

ionic bonds between positive + negatively charged R-groups

R-group binding with hydrogen ion = positively charged

R-group losing a hydrogen ion = negatively charged

ionic bonds are more sensitive to pH due to involvement of H+

145
Q

Describe tertiary structure disulphide bonds between R-groups (3)

A

disulphide bond between amino acids with sulphur atoms

e.g cysteine and methionine

strongest covalent bonds

146
Q

Describe tertiary structure hydrophobic interactions between R-groups (3)

A

water forms hydrogen bonds between polar/hydrophilic amino acids

non-polar amino acids will clump in hydrophobic clusters in the interior of the protein

to minimise contact with surround ing water molecules

147
Q

Effect of R-group hydrophilic polarity on tertiary structure (2)

A

R-groups will orient outwards towards water

soluble in water = can allow them to carry out functions in aqueous solution

148
Q

Effect of R-group hydrophobic polarity on tertiary structure (2)

A

R-groups reside in protein interior

stabilises protein - maximises hydrophobic interactions within centre + hydrogen bonding between amino acids on surface + water

149
Q

Define quaternary structure proteins

A

arrangement of 2 or more polypeptide chains to form a protein

150
Q

Define non-conjugated proteins (2)

A

proteins with only polypeptide subunits

e.g collagen + insulin

151
Q

Define conjugated proteins (2)

A

proteins with polypeptide subunits + non-protein (prosthetic group

e.g haemoglobin containing haem to bind to oxygen

152
Q

What happens after a polypeptide chain is synthesised (2)

A

protein folding - adopts specific 3D shape which corresponds to its function

influenced by sequence of amino acids, hydrogen + ionic bonding, hydrophobic interactions

153
Q

Name the types of quaternary structure proteins (2)

A

Globular

Fibrous

154
Q

Define globular proteins (4)

A

spherical shaped proteins with irregular folds

soluble in water

play roles as enzymes, transporters, regulators

e.g insulin, haemoglobin, enzymes

155
Q

Features of insulin as a globular protein (4)

A

has 2 polypeptide chains - alpha and beta

held in 3D shape by hydrogen bonds, hydrophobic interactions, disulphide bonds

has hydrophilic exterior - allows insulin to react with water + other hydrophilic molecules in blood, able to travel through blood + bind to its receptors

has hydrophobic interior - stabilises globular shape, allows insulin to bind to receptor

156
Q

Function of insulin (2)

A

regulates amount of glucose in bloodstream in response to high glucose levels

binds to receptors on cells - allows glucose to enter cells to be used or stored

157
Q

Define a fibrous protein (3)

A

elongated polypeptides - polypetide chains linked together into narrow fibres with hydrogen bonds between them

insoluble in water

designed for strength + stability

158
Q

Collagen as a fibrous protein (2)

A

3 polypeptide chains twisted together in a triple helix shape

held together by hydrogen bonds

159
Q

Collagen function

A

provides structural support to tissues + maintains their shape

Biology (11 decks)

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