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Biology Edexcel B A Level > Topic 1 Biological Molecules > Flashcards

Topic 1 Biological Molecules Flashcards

carbs, lipids, proteins, enzymes, inorganic ions, water

1
Q

What kind of molecule is water?

A

Polar
Meaning electrons aren’t shared equally

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2
Q

Dipole property of water

A

2 poles, oxygen is electronegative (slightly negative) , hydrogen is slightly positive

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3
Q

What atoms are electronegative?

A

Usually
Oxygen nitrogen or fluorine

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4
Q

Why is water a good solvent?

A

Weak hydrogen bonds so water easily disassociates into OH- and H+ to form other bonds
Because it is DIPOLE
pH

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5
Q

Why does water have a high specific heat capacity?

A

Takes a lot of energy to break down a lot of hydrogen bond
Stronger together

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6
Q

What are hydrophobic molecules and their properties

A

Water fearing molecules
Insoluble
Molar is not polar, so cannot form H bonds hence cannot dissolve

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7
Q

What are Hydrophilic molecules and their properties?

A

Water loving
Soluble because molecules are polar, so can form hydrogen bonds with water

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8
Q

Give 3 properties of water

A

-ice floats
-tension, cohesion and adhesion
-water in reactions (pH, solvent, hydrolysis)
-transparency (predators can spot prey)
-water as transport medium
-high SHC, thermal stability
-incompressible

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9
Q

Give 3 properties of water

A

-ice floats
-tension, cohesion and adhesion
-water in reactions (pH, solvent, hydrolysis)
-transparency (predators can spot prey)
-water as transport medium
-high SHC, thermal stability
-incompressible

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10
Q

What are some macromolecules?

A

Proteins, lipids, starch, nucleic acid

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11
Q

Role of nitrate ions in plants?

A
  • supply of nitrogen to synthesize protein, nucleic acids, chlorophyll etc
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12
Q

Nitrate ion deficiency symptoms in plants?

A

Reduced chlorophyll
Leaves turn pale / yellow

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13
Q

Role of Magnesium ions in plants?

A

Make chlorophyll

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14
Q

Symptom of magnesium ion deficiency in plants?

A
  • failure to synthesis chlorophyll
    therefore: Stunt growth, yellowing leaves
    (Since less magnesium = less p/s = less glucose for respiration = less ATP)
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15
Q

Role of calcium ions in plants?

A

Build new cell walls - Form calcium pectate for the middle lamellae

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16
Q

Symptom of calcium ion deficiency in plants?

A

stunted growth bcs of poor cell wall development

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17
Q

Role of phosphate ions in plants?

A

Make DNA, RNA, ATP

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18
Q

What does ATP stand for?

A

Adenosine Triphosphate

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19
Q

Give 3 differences between starch and cellulose

A

Starch / cellulose
Alpha glucose / beta
Is branched / not
Has 1,4-glycosidic bonds and 1,6-glycosidic bonds / 1,4 only
Same orientation / flipped glucose molecules

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20
Q

What is the structure and function of glycogen?

A

Made up of alpha glucose
1,4 and 1,6 - glycosidic bonds
In animal cells
Insoluble so no osmotic effect
Compact and branched, allows quick hydrolysis

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21
Q

What are the structures and functions of cellulose

A

Made up of beta glucose
Straight chains, only 1,4 glycosidic bonds. Alternate Beta glucose flipped 180°
Fibres held together by HYDROGEN bonds
High tensile strength , give plants structure
Polar so allows water to diffuse through

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22
Q

How do triglycerides form

A

Condensation reaction by ester bonds between a glycerol and three fatty acids

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23
Q

Relate structures of triglycerides to their functions

A

• High energy:mass ratio = high calorific value from oxidation (energy storage).
• Insoluble hydrocarbon chain = no effect on water potential of cells & used for waterproofing.
• Slow conductor of heat = thermal insulation e.g.
adipose tissue.
• Less dense than water = buoyancy of aquatic animals.

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24
Q

Functions of phospholipids relate to their structure

A

Barrier to Protect cells from external
glycerol backbone attached to 2 hydrophobic fatty acid tails & 1 hydrophilic polar phosphate head

• forms phospholipid bilayer in water = component of membranes
• tails can splay outwards = waterproofing

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25
Q

what are the 3 monosaccharides?

A

fructose, glucose, galactose

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26
Q

what is maltose made up of?

A

2 alpha glucose

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27
Q

what is sucrose made up of?

A

gluocse + fructose

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28
Q

what is lactose made up of?

A

glucose + galactose

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29
Q

what is a polysaccharide?

A

chain of many monosaccharides

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30
Q

what is starch made up of?

A

chain(polymer) of ALPHA glucose
(Amylose and amylopectin)

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31
Q

what is starch used for?

A

chloroplast stroma
energy storage in plants

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32
Q

what is glycogen made up of?

A

chain(polymer) of alpha glucose

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33
Q

what is glycogen used for?

A

muscle cells
main energy storage

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34
Q

what is cellulose made up of?

A

chain (polymer) of beta glucose

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35
Q

what is cellulose used for?

A

plant cell wall

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36
Q

Name the reaction involved when a disaccharide is formed

A

condensation reaction

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37
Q

name the type of bond formed when disaccharides are formed

A

glycosidic bonds

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38
Q

what is starch made up of?

A

80% amylopectin
20% amylose
v compact

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39
Q

what is amylopectin’s structure?

A

branched
having both α-1,4-glycosidic and α-1,6-glycosidic

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40
Q

what is amylose’s structure?

A

helix structure
only α-1,4-glycosidic bonds

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41
Q

is starch soluble in water?

A

no, it is insoluble

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42
Q

why is amylopectin hydrolysed easier?

A

because it is highly branched with protruding ends, so more SA for enzymes to work on

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43
Q

how to test for starch?

A

iodine test
turns blue black precipitate

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44
Q

how to test for reducing sugars? (e.g. glucose fructose maltose)

A

Benedict’s test
water bath
turns brick red ppt

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45
Q

how to test for non-reducing sugars? (e.g. sucrose)

A

benedict’s reagent + dilute HCl
boil
dnf

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46
Q

what is a triglyceride made up of?

A

1 glycerol + 3 fatty acids

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47
Q

what bond is formed between glycerol and fatty acids?

A

ester bonds

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48
Q

give 3 main functions of lipids

A
  • energy storage
  • thermal insulation
  • waterproofing
  • buoyancy (less dense than water)
  • major component of cell membranes
  • cushion and protection of internal organs
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49
Q

what are some lipid examples?

A

triglycerides
phospholipids
cholesterol

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50
Q

what is the structure of phospholipids?

A

1 phosphate group + 2 fatty acids
Hydrophilic head, hydrophobic tail

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51
Q

is phospholipid soluble in water

A

the head is soluble (bcs can ionise)
but tail is insoluble (non-polar, hydrophobic)

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52
Q

what are 5 structures of the fluid mosaic model

A
  • fluid phospholipid bilayer, movable
  • internal/integral protein
  • external/surface protein
  • cholesterol
  • channel protein
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53
Q

what are saturated fatty acids?

A

only single bonds between carbon atoms
(it is a -COOH carboxylic acid)

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54
Q

what bond is formed between 2 amino acids?

A

peptide bond via condensation

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55
Q

what are two secondary structures of polypeptides?

A

alpha-helix
beta pleated sheet

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56
Q

what are two tertiary structures of protein molecules?

A

globular and fibrous

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57
Q

which 4 bonds are used for peptide folding?

A
  • hydrogen
  • ionic
  • disulfide
  • hydrophilic/phobic
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58
Q

compare globular vs fibrous proteins

A
  • circular vs strands
  • irregular amino acid sequence vs regular
  • functional vs structural
  • generally soluble vs insoluble
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59
Q

what are some examples of globular proteins?

A

haemoglobin, enzymes, insulin

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60
Q

what are some examples of fibrous proteins?

A

collagen, fibrin, actin

61
Q

protein synthesis vs dna replication - what is the diff?

A

Protein synthesis makes proteins, while DNA replication makes DNA

62
Q

what does a nucleotide consist of?

A

phosphate, deoxyribose sugar and nitrogenous base

63
Q

name 4 DNA bases and number of carbon rings they have

A

Adenine
Guanine - Purine - 2
(A-G-POO-TWO)

Cytosine
Thymine - Pyrimidine - 1

64
Q

what bonds are formed between phosphate and deoxyribose sugar ( in DNA )

A

phosphodiester bond

65
Q

How many H bonds between Adenine and Thymine?

66
Q

How many H bonds between Cytosine and Guanine?

67
Q

whats the relationship between A-T and C-G

A

complementary

68
Q

what are the steps (+enzymes) used in DNA replication?

A
  • DNA helicase unwinds & breaks H bonds between complementary bases
  • free nucleotides match complementary bases into Okazaki fragments
  • DNA polymerase adds adjacent nucleotides tgt (5’ to 3’ direction?? CHECK NOTES)
  • DNA ligase seals the gaps between nucleotides
69
Q

what method is used for DNA replication?

A

semi conservative
bcs new DNA consist of 1 new + 1 old strand

70
Q

What is the evidence for the semi-conservative replication?

A

Meselson and Stahl
Replication of Nitrogen using ‘heavy’ isotope 15 N and ‘light’ 14N
1st Gen - each DNA made up of 1 parent + 1 new strand
after replication in 2nd Gen there were 2 layers, one lighter one heavier

71
Q

what structure is DNA?

A

double helix

72
Q

what are the stages of a cell cycle?

A

G1 - cellular contents replicated
S - replication of DNA
G2 - check for errors
M - mitosis
C - cytokinesis

73
Q

what are enzymes?

A

protein that changes rate of chemical reaction without changing itself

74
Q

4 major factors that influence enzyme RoR

A

temp
pH
enzyme conc
substrate conc

75
Q

What is the induced fit hypothesis?

A

shape of active site changes to fit precisely around the substrate

76
Q

What are cofactors? + examples?

A

Helper to enzymes, required to function properly
e.g. coenzymes, inorganic ions and prosthetic groups

77
Q

What is an inhibitor?

A

substance that slows RoR

78
Q

What is a competitive inhibitor?

A

competes with the substrate for the active site of the enzyme

79
Q

is competitive inhibitor reversible or no?

A

reversible

80
Q

what is a non-competitive inhibitor?

A

they bind to allosteric sites of enzymes, changing the active site of enzymes, so fewer/no ES complexes formed

81
Q

what is the change of graph if there are competitive inhibitors?

A

RoR decreases but plateaus at about the same time

82
Q

is non-competitive inhibitor reversible or no?

A

irreversible, permanent change

83
Q

what is the change of graph if there are non-competitive inhibitors?

A

RoR slows
plateaus earlier

84
Q

what is catabolism?

A

breaking large molecules into smaller ones
e.g. digestion

85
Q

what is anabolism?

A

building up smaller molecules to larger ones
e.g. muscle growth

86
Q

why are carbohydrates vital in humans?

A

energy source

87
Q

why are fibres vital in humans?

A

helps w digestion

88
Q

why are proteins vital in humans?

A

muscle growth and repair
found in DNA

89
Q

why are lipids vital in humans?

A

energy storage
thermal insulation
used for plasma membrane

90
Q

why are vitamins and minerals vital in humans?

A

help w immunity, chemical reactions

91
Q

why is water vital in humans?

A
  • temp control
  • transport substances
  • chemical reactions (metabolism)
92
Q

what does DNA polymerase do?

A

line up nucleotides and join them via phosphodiester bonds (condensation reaction)

93
Q

what is the only direction DNA polymerase can travel in?

A

5’ to 3’

94
Q

What breaks hydrogen bonds between complementary bases?

A

DNA helicase

95
Q

in where is Uracil used instead of Thymine?

96
Q

What bond is formed to bind nucleotides together?

A

phosphodiester bond

97
Q

What do ribosomes do in protein synthesis?

A

bind to mRNA, read code 3 bases at a time aka codon

98
Q

what is the shape of tRNA?

A

clover leaf shape

99
Q

what are exons and introns?

A

exons - coding part of gene
introns - non-coding part of gene

100
Q

Why do mutations occur?

A

mutagen exposure in our environment eg UV light
randomly occurs

101
Q

How does one get sickle cell anaemia?

A

base substitution (A replaces T) in beta haemoglobin chain
changing shape of haemo.

102
Q

what is the issue of sickle cell anaemia?

A

haemoglobin stop carrying oxygen so efficiently, causing blockages in small blood vessels

103
Q

why are mutations sometimes good?

A

advantageous mutations allows positive evolution

104
Q

what are monomers?

A

single small molecule that can join together and form a polymer
e.g. nucleic acids

105
Q

What are buffers?

A

they resist changes to pH

106
Q

how to test for proteins?

A

Biuret’s reagent
blue to purple

107
Q

how to test for fat/lipids?

A

dissolve in ethanol
emulsion test
there will be emulsion/greasy patch produced in comparison to water

108
Q

are lipids polar?

A

NO! generally hydrophobic

109
Q

what are the 2 types of fatty acids?

A

saturated and unsaturated

110
Q

How do 2 monosaccharides join together to form a disaccharide?

A

Glycosidic bond forming condensation reaction

111
Q

Compare phospholipids and triglycerides…

A

Phospholipids are polar
Triglycerides are non-polar

112
Q

What bonding is present in both secondary and tertiary structures of proteins?

A

Hydrogen only

113
Q

Give the meaning of a tertiary structure of a protein (2 marks)

A

3D shape of protein
Held together by bonds between R groups

114
Q

What are the steps of translation? (4 marks)

A
  • mRNA attaches to ribosomes
  • tRNA attached to specific amino acids
  • tRNA anticodon binds to mRNA codon
  • peptide bonds form between amino acids
  • process involves start/stop codons
115
Q

What is it meant by secondary structure of protein? 2 marks

A

Folding of primary structure
Into alpha helix or beta pleated sheet
From formation of hydrogen bonds

116
Q

Explain how a primary structure of a hormone determines its’ properties. 4 marks

A
  • sequence of amino acids determining tertiary structure
  • because determines position of R group bonds
  • eg hydrogen, ionic, disulfide
  • final structure has to be specific, complementary to receptor molecules
117
Q

Why are globular proteins soluble in water? (3 marks)

A
  • folded so hydrophilic groups are facing the outside
  • exposed R groups are polar
  • so can form H bonds with water
  • because water is a polar solvent
118
Q

Which enzyme in DNA replication forms phosphodiester bonds?

A

DNA polymerase AND ligase
P-P

119
Q

What are 2 things about calcium pectate?

A

Found in middle lamallae
Hold Cell walls together

120
Q

What ions are needed to make amino acids?

121
Q

What ions are needed to make amino acids?

122
Q

What ions are needed to make amino acid and DNA?

A

Nitrate and phosphate ions

123
Q

how does the dipole nature of water enable muscle layers of worm to push against cavity and change the shape of earthworm? 3 marks

A
  • water is tightly bonded together
  • via H bonds
  • so they are incompressible
  • change body shape since pressure increases, but volume stays the same
124
Q

what components are found in phospholipids?

A

glycerol and phosphate in the head
fatty acid in tail

125
Q

what properties of water result in surface tension? 3 marks

A
  • polar molecules
  • can form H bonds
  • therefore cohesive
126
Q

Why does respiration of lipid generate more energy than carbs?

A

More C-H bonds and H bonds

127
Q

Does amylose or amylopectin hydrolyse quicker? Why?

A

Amylopectin because it is branched with 1,4 and 1,6-glycosidic bonds!

128
Q

What is the relationship between sweating (heat loss) and dipole nature of water?

A

Dipole is H is positively charged, forming weak H bonds between molecules
Lots of energy needed to break this bond
Water evaporate, taking heat w it )(high latent heat evaporation)

129
Q

What happens when you freeze water?

A

Expands
Lots of H bonds

130
Q

Explain how a structure of cellulose is adapted for its function in cell walls. (3 marks)

A
  • straight chain of molecules
  • held tgt by H bonds
  • prevent cell bursting
  • polar, so allows water to diffuse through
131
Q

what are the steps of translation
(+ release)

A
  • mRNA leaves via nuclear pores
  • attach to ribosomes (on rER)
  • codon pair with anticodons on tRNA + brings amino acid
  • peptide bonds formed between amino acids
    (- enter Golgi to modify
  • travel in vesicles
  • exocytosis)
132
Q

what are ribosomes made of?

A

ribosomal RNA and protein

133
Q

what is the role of tRNA in protein synthesis?

A

during translation, it brings a specific amino acid to the ribosome by binding its anticodon to mRNA codon

134
Q

What is the role of a ribosome in protein synthesis?

A

holds mRNA-tRNA complexes tgt
- so condensation reactions can form between amino acids
- peptide bonds can form between carboxylic acid and amine groups

135
Q

what is the difference in structures of mRNA and tRNA?

A

mRNA / tRNA
carry info from genes to produce polypeptides/ transport amino acids to ribosomes
linear / clover shape
larger + size varies / smaller, same size
no amino acid binding site / yes
has codons / has anticodon

136
Q

what are the differences between DNA replication and transcription? (there are 5)

A

DNA rep / transcription
involves DNA polymerase / RNA polymerase
DNA nucleotides / RNA nucleotides
semi conservative / is not
2 template strands / 1
uses double stranded molecule / single

137
Q

Describe the structure of globular proteins. (3 marks)

A
  • 3D spherical shape
  • hydrophilic R groups on the outside
  • hydrophobic on the inside
  • ionic / hydrogen / disulfide
138
Q

Name the covalent bond formed between two polypeptide chains.

139
Q

Describe how a molecule of mRNA is formed during transcription. (4 marks)

A
  • DNA unwinds
  • RNA mononucleotides line up and attach to template
  • between complementary bases
  • form phosphodiester bonds
  • condensation reaction
  • using RNA polymerase, DNA helicase, DNA ligase
  • mRNA detaches from DNA
140
Q

Explain how a poly protein molecule is converted into ten separate molecules. (2 marks)

A
  • hydrolysis of peptide bonds
  • by protease
141
Q

Explain why the non-competitive inhibitor has decreased the maximum rate of reaction. (2 marks)

A
  • due to fewer enzyme substrate complexes formed
  • as some active sites are no longer complementary
142
Q

Give 3 differences between the structure of collagen and haemoglobin. (3 marks)

A

collagen / haemoglobin
fibrous / globular
3 polypeptides / 4
little to no 3° structure / has 4°
doesn’t / has haem group
hydrophobic R group on surface / opposite, hydrophilic

143
Q

What is the role of mRNA in protein synthesis? (2 marks)

A
  • is a copy of antisense
  • made up of codons
  • used in translation
  • binds to ribosomes
144
Q

What is the role of tRNA in protein synthesis? (2 marks)

A
  • transports specific amino acid
  • binds to mRNA
  • bring amino acids together
145
Q

Act D inhibits transcription.
Explain why pollen tubes could still grow in the presence of act D. (2 marks)

A
  • some mRNA in pollen grain
  • so some translation / protein synthesis can take place
146
Q

Describe how monomers are bonded to a polypeptide chain during the synthesis of actin. (2 marks)

A

Peptide bonds formed
Between amino and carboxyl group
By condensation reaction

147
Q

What happens in the rough endoplasmic reticulum?

A

Protein synthesis

148
Q

Explain how the properties of starch make it suitable as an energy store in cell. (2 marks)

A
  • branched
  • so easily hydrolysed to release ATP for respiration
    Or
  • tightly packed
  • a lot can be stored in a small space
    Or
  • insoluble
  • so does not have osmotic effect

Biology Edexcel B A Level (22 decks)

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