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Biology A Level > Topic 1 - Biological Molecules And Nucleic Acid > Flashcards

Topic 1 - Biological Molecules And Nucleic Acid Flashcards

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1
Q

Monomer

A

The smaller units from which larger molecules are made

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2
Q

Polymer

A

Molecules made from a large number of monomers joined together

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3
Q

Monosaccharide

A

The monomers from which larger carbohydrates are made
e.g. glucose, fructose, galactose

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4
Q

Disaccharide

A

Formed by the condensation of two monosaccharides
held together by a glycosidic bond
e.g. maltose, sucrose, lactose

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5
Q

Polysaccharide

A

Formed by the condensation of many glucose units
held by glycosidic bonds
e.g. starch, glycogen, cellulose

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6
Q

Cellulose

A

Polysaccharide in plant cell walls formed by the condensation of
β-glucose

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7
Q

Glycogen

A

Polysaccharide in animals
formed by the condensation of
α-glucose

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8
Q

Starch

A

Polysaccharide in plants
formed by the condensation of α-glucose
contains two polymers - amylose and amylopectin

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9
Q

Glycosidic bond

A

C–O–C link
between two sugar molecules formed by a condensation reaction
it is a covalent bond

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10
Q

Amylose

A

Polysaccharide in starch made of α-glucose
joined by 1,4-glycosidic bonds
coils to form a helix

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11
Q

Amylopectin

A

Polysaccharide in starch
made of α-glucose
joined by 1,4 and 1,6-glycosidic bonds
branched structure

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12
Q

Condensation reaction

A

A reaction that joins two molecules together
with the formation of a chemical bond
involves the elimination of a molecule of water

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13
Q

Hydrolysis reaction

A

A reaction that breaks a chemical bond
between two molecules
involves the use of a water molecule

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14
Q

Microfibrils

A

Long, straight chains of β-glucose running parallel to one another
Cross linked by hydrogen bonds
These molecules joined to form microfibrils which in turn are grouped to form fibres

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15
Q

Triglyceride

A

Formed by the condensation of one molecule of glycerol and three molecules of fatty acids
forming 3 ester bonds

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16
Q

Phospholipid

A

Formed by the condensation of one molecule of glycerol and two molecules of fatty acid
held by two ester bonds
a phosphate group is attached to the glycerol

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17
Q

Induced-fit model

A

The enzyme active site is not initially complementary to the substrate
the active site moulds around the substrate
this puts tension on bonds lowers the activation energy

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18
Q

Competitive inhibitor

A

A molecule that is the same/similar shape as the substrate
binds to the active site
prevents enzyme-substrate complexes from forming

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19
Q

Non-competitive inhibitor

A

A molecule that binds to an enzyme at the allosteric site
causing the active site to change shape
preventing enzyme-substrate complexes from forming

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20
Q

Primary structure

A

The sequence of amino acids on a polypeptide chain

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21
Q

Secondary structure

A

The folding or coiling
to create a β pleated sheet or an
α helix
held in place by hydrogen bonds

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22
Q

Tertiary structure

A

The further folding to create a unique 3D shape
held in place by hydrogen, ionic and sometimes disulfide bonds

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23
Q

Quaternary structure

A

More than one polypeptide chain in a protein
Can also have prosthetic group

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24
Q

Peptide bond

A

Covalent bond joining amino acids together in proteins
C–N link between two amino acid molecules
formed by a condensation reaction

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25
Q

What is the effect of temperature on enzyme-controlled reaction

A

At low temperatures, there is not enough kinetic energy for successful collisions between the enzyme and substrate.
At too high a temperature, enzymes denature, the active site changes shape and enzyme- substrate complexes cannot form.

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26
Q

What is the effect of pH on enzyme-controlled reaction

A

Too high or too low a pH will interfere with the charges in the amino acids in the active site.
This breaks the ionic and hydrogen bonds holding the tertiary structure in place
therefore the active site changes shape and the enzyme denatures
Different enzymes have a different optimal pH

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27
Q

What is the effect of substrate concentration on enzyme-controlled
reaction

A

At low substrate concentrations, there will be fewer collisions between the enzyme and substrate.
At high substrate concentrations, the rate plateaus because all the enzyme active sites are saturated.

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28
Q

What is the effect of enzyme concentration on enzyme-controlled
reaction

A

At low enzyme concentrations, there will be fewer collisions between the enzyme and substrate.
At high enzyme concentrations, the rate plateaus because there are more enzymes than the substrate, so many empty active sites.

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29
Q

Ester bond

A

–COO– chemical bond
formed between glycerol and fatty acids

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30
Q

Hydrophilic

A

The ability to mix, interact or attract water

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31
Q

Hydrophobic

A

The tendency to repel and not mix with water

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32
Q

Glucose

A

Monosaccharide that exists as two isomers β glucose and α glucose.
Alpha is -oh group below and beta is -oh group above

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33
Q

Galactose

A

An example of a monosaccharide that forms lactose

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34
Q

Fructose

A

An example of a monosaccharide that forms sucrose

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35
Q

Isomer

A

Molecules with the same molecular formula
but the atoms are arranged differently

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36
Q

Maltose

A

Disaccharide
formed by the condensation of two glucose molecules

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37
Q

Lactose

A

Disaccharide
formed by the condensation of a glucose molecule and a galactose molecule

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38
Q

Sucrose

A

Disaccharide
formed by the condensation of a glucose molecule and a fructose molecule

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39
Q

Polypeptide

A

Polymer chain of a protein
made up of amino acids
bonded together by peptide bonds following condensation reactions

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40
Q

Amino acid

A

The monomer of a protein formed from C,H,O,N
contains a carboxyl group, amine group and an R group

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41
Q

Carboxyl group

A

COOH group
made up of a C with hydroxyl (OH) and carbonyl (double-bonded O) group bonded to it
found in amino acids and fatty acids

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42
Q

Amine group

A

NH2 group found on amino acids

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43
Q

R group on amino acids

A

The variable group
the part of each of the 20 amino acids that is different

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44
Q

α helix

A

A secondary structure in proteins a coiled shape held in place by hydrogen bonds

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45
Q

β pleated sheet

A

A secondary structure in proteins
a folded, pleated shape
held in place by hydrogen bonds

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46
Q

Hydrogen bonds

A

Weak bond
forms between H and O
in many biological molecules e.g. proteins, water, DNA, tRNA

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47
Q

Ionic bonds

A

A bond that forms between the R groups of different amino acids in the tertiary structure of proteins

48
Q

Disulfide bonds

A

A strong covalent bond
between two sulfur atoms in the R groups of different amino acids
in the tertiary structure of proteins

49
Q

Active site

A

Unique-shaped part of an enzyme that the substrate binds to

50
Q

Activation energy

A

The minimum amount of energy required for a reaction to occur

51
Q

Enzyme-substrate complex

A

Forms when an enzyme and substrate collide and bind resulting in a lowered activation energy

52
Q

Denature

A

When the active site changes shape so the substrate can no longer bind

53
Q

Enzyme-inhibitor complex

A

The structure that forms when an enzyme and inhibitor collide and bind
prevents enzyme-substrate complexes from forming

54
Q

Saturated fatty acid

A

A long hydrocarbon chain with a carboxyl group at one end only single bonds between carbon atoms

55
Q

Unsaturated fatty acid

A

A long hydrocarbon chain with a carboxyl group at one end
at least one double bond between carbon atoms

56
Q

Polar molecule

A

A molecule that has an uneven distribution of charge

57
Q

Phospholipid bilayer

A

Phospholipids have two charged regions
in water, they are positioned so that the heads are exposed to water and the tails are not

58
Q

Plasma membrane

A

Phospholipid bilayer
cell surface membranes and organelle membranes

59
Q

Reducing sugar

A

Sugars that can reduce Cu2+ ions in Benedict’s reagent to Cu+ ions in the form of copper (I) oxide
which forms a brick-red precipitate

60
Q

Test for reducing sugar

A

Add Benedict’s reagent
heat
observe green/yellow/orange/brick red precipitate

61
Q

How does the structure of a triglyceride relate to it’s function? (4)

A

Large ratio of energy-storing carbon-hydrogen bonds compared to the number of carbon atoms; a lot of energy is stored in the molecule
High ratio of hydrogen to oxygen atoms they act as a metabolic water source
Do not affect water potentials and osmosis - non polar
Have a relatively low mass

62
Q

How does the structure of a phospholipid relate to it’s function?

A

Phospholipids have two charged regions, so they are polar
In water, they are positioned so that the heads are exposed to water and the tails are not.
This forms a phospholipid bilayer which makes up the plasma membrane around cells.

63
Q

How does the structure of a triglyceride and phospholipid differ?

A

A phospholipid has one fewer fatty acid chain
which is replaced by a phosphate group

64
Q

What is the difference between saturated and unsaturated fatty acid?

A

A saturated fatty acid has no double bonds between carbon atoms
where as unsaturated fatty acids had at least one double bond between carbon atoms

65
Q

Non-reducing sugar

A

a sugar unable to reduce Cu2+
the glycosidic bond must be hydrolysed to expose the reducing group
e.g. sucrose

66
Q

Test for non- reducing sugar

A

Following a negative Benedict’s test boil sample in acid (hydrolyse glycosidic bonds)
and then neutralise with alkaline ( Benedict’s cannot work in acidic conditions)
add Benedict’s reagent and heat observe orange/brick red colour

67
Q

Test for starch

A

Add iodine
turns blue/black

68
Q

Test for lipids

A

Add ethanol and shake to dissolve
then add water
white emulsion forms

69
Q

Test for protein

A

Add biuret (blue)turns purple

70
Q

Nucleotide

A

The monomer of DNA and RNA contains a pentose sugar, a phosphate group and a nitrogenous base

71
Q

Nitrogenous base

A

Part of a nucleotide
adenine, guanine, cytosine, thymine and uracil
Attached to first carbon
Adenine and guanine - purine bases (double ring structure)
Cytosine, uracil and thymine - pyrimidine (single ring structure)

72
Q

DNA nucleotide

A

The monomer of DNA
contains a deoxyribose sugar, a phosphate group(5th carbon) and a nitrogenous base(1st carbon)

73
Q

Polynucleotide

A

DNA polymer many nucleotides joined together via a condensation reaction
joined by phosphodiester bonds

74
Q

Phosphodiester bond

A

Bond joining two nucleotides together
forms between a phosphate group and the pentose sugar

75
Q

Complementary base pairs

A

The base pairs that align opposite each other and form hydrogen bonds
adenine and thymine/uracil (2 H-bonds)
guanine and cytosine (3H-bonds)
Purine (double ring)- pyrimidine (single ring)→complementary base pairs

76
Q

Ribose

A

Pentose sugar
found in RNA nucleotide and ATP

77
Q

Uracil

A

Nitrogenous base
found in RNA instead of thymine

78
Q

mRNA

A

a copy of a gene
single-strand polymer of RNA

79
Q

tRNA

A

Found only in the cytoplasm single-stranded but folded to create a shape that looks like a cloverleaf
held in place by hydrogen bonds

80
Q

rRNA

A

rRNA combines with protein to make ribosomes

81
Q

DNA template strand

A

A DNA strand that is used to make a new DNA copy from
both DNA strands in the double helix are used as templates in DNA replication

82
Q

DNA polymerase

A

An enzyme in DNA replication
joins together adjacent nucleotides by forming phosphodiester bonds

83
Q

Semi-conservative replication

A

DNA replication is semi- conservative replication
one strand is from the parental DNA and one strand is newly synthesised

84
Q

DNA helicase

A

Enzyme that breaks hydrogen bonds between the two chains of DNA in a double helix
causes the two strands to separate involved in DNA replication and transcription

85
Q

Large latent heat of vaporisation

A

A lot of energy is required to convert water from its liquid state to a gaseous state
This is due to the hydrogen bonds, as energy is needed to break these to turn it into a gas
means water can provide a cooling effect

86
Q

High specific heat capacity

A

a lot of energy is required to raise the temperature of the water
because some of the heat energy is used to break the hydrogen bonds
between water molecules
important so water can act as a temperature buffer

87
Q

Metabolite

A

Water is involved in many reactions such as photosynthesis, hydrolysis, and condensation reactions

88
Q

Solvent

A

Water is a good solvent
meaning many substances dissolve in it
polar (charged) molecules dissolve readily in water due to the fact water is polar

89
Q

Strong cohesion

A

Water molecules ‘stick’ together due to hydrogen bonds
results in water moving up the xylem as a continuous column of water
provides surface tension, creating a habitat on the surface of the water for small invertebrates

90
Q

ATP synthase

A

Enzyme that catalyses the synthesis of ATP from ADP + Pi

91
Q

ATP hydrolase

A

Enzyme that catalyses the hydrolysis of ATP into ADP +Pi

92
Q

Phosphorylation

A

The addition of a phosphate group to a molecule
making the molecule more reactive/it gains energy

93
Q

Structure of water

A

Water is a polar molecule
the oxygen atom is slightly negative
the hydrogen atoms are slightly positive

94
Q

Dipeptide

A

Two amino acids bonded together by a peptide bond
formed by a condensation reaction

95
Q

RNA nucleotide

A

monomer of RNA
composed of a phosphate group, ribose and a nitrogenous base
has the base uracil instead of thymine

96
Q

Role of hydrogen ions

A

determine the pH
the more hydrogen ions, the more acidic the conditions are
an important role in chemiosmosis in respiration and photosynthesis

97
Q

Role of iron ions

A

a compound of haemoglobin
involved in oxygen transport

98
Q

Role of sodium ions in co-transport

A

involved in co-transport for absorption of glucose and amino acids in the ileum

99
Q

Role of phosphate ions

A

as a component of DNA, RNA and ATP
phosphodiester bond in DNA and RNA forms between the phosphate group and the pentose sugar
Structural function in DNA - PO4 3-
ATP- for storing energy

100
Q

Fatty acid structure

A

carboxyl group and a long hydrocarbon chain
can be saturated or unsaturated

101
Q

Properties of ATP which makes it good source of energy (6)

A
  • Immediate source of energy as ATP to ADP is a single reaction
    -Bonds in ATP is weak so broken down easily to produce energy
    -Releases energy is small and manageable units so less energy list as heat
    -It’s small and soluble so easily transported in body
    -Can make other molecules more reactive - phosphorylation
    -It cannot pass out of cell so cells always have immediate source of energy
102
Q

3 ways synthesis of ATP occurs

A

Photophosphorylation - photosynthesis
Oxidative phosphorylation - respiration
Substrate level phosphorylation - in plant and animal cells when phosphate groups are transferred from donor groups to ADP

103
Q

Why are DNA strands anti-parallel?

A

The 5’ or 5prime - where phosphate group is attached
3’or 3 prime - where hydroxyl group present.
When DNA forms double helix - they are arranged so one strand runs 5’ to 3’ and the other strand is 3’ to 5’ - antiparallel.
This is because in vivo DNA polymerase which forms DNA molecules can only attach nucleotides to hydroxyl group on 3’ carbon.
DNA polymerase active site is complementary only to the 3’ end of the molecule with hydroxyl group

104
Q

Stability of DNA

A

-The phosphodiester bonds protect the chemically reactive bases from corrruption
- C to G has 3 H-bonds. Larger the no.of C to G more stable the DNA
There are other interactive forces between the bases which holds them together

105
Q

What’s a quantitative and qualitative way of measuring concentration of sugars?

A

Benedict’s colour change with reducing sugars - semi quantitative as colour change depends on concentration of sugars. Blue-> Green->Yellow->Orange->Brick red
Quantitative-
Colorimeter- gives absorbance value
Filter ppt and dry it and weigh it - concentration of sugars

106
Q

What are the two basic types of proteins? Structure

A
  • Fibrous protein - eg collagen carry out structural functions
    -Globular protein -eg enzymes and Hb carry out metabolic functions
107
Q

Basic structure of fibrous protein.

A

-Long, straight chains running parallel to one another
-Cross bridges formed - makes them a very stable molecule
-eg collagen

108
Q

Molecular structure of fibrous protein

A

Primary- sequence of amino acids - unbranched polypeptide
Secondary - polypeptide chain very tightly wound
Lots of amino acids, glycine helps packing them closely
Tertiary-chain is twisted into second helix
Quaternary - 3 polypeptide chains wound together the same way individual fibres are in a rope

109
Q

Where is collagen found

A

-Tendons
-Tendons connect muscles to bones
-As muscles contract bone is pulled in the direction of the contraction
-Individual polypeptides in collagen held together by bonds between amino acids in adjacent chains

110
Q

What is end product inhibition

A

Type of non competitive inhibition
In metabolic pathways
Helps keep steady concentration of particular chemical in a cell
The same chemical often acts as an inhibitor of an enzyme at the start of the reaction
Eg- If concentration of end product is higher than normal, more of enzyme at start inhibited and therefore concentration of chemical back to normal
-If concentration of end product is lower than normal, less of enzyme at start inhibited and therefore concentration of chemical back to normal

111
Q

Why did scientists doubt DNA carried the genetic code

A

It was a relatively simple molecule
Later experiment with mice and bacteria carrying pneumonia was used to prove DNA carried the genetic code
As DNS transformed dead harmful strain bacteria to living harmful ones

112
Q

4 requirements for semi conservative replication of DNA

A

4 types of nucleotides
Enzyme dna polymerase
Both strand acts as a template
Source of chemical energy to drive this process

113
Q

Process of semi conservative replication

A

-DNA helicase breaks the H-bonds between the bases
-Exposes the bases and now both the strands acts as a template strand
-Free nucleotides align with complementary bases
-DNA polymerase runs along the free nucleotides and catalyses the reaction of forming phosphodiester bonds by condensation reaction
-This leaves us with new DNA molecule with one parental and one new strand - semi conservative replication

114
Q

What’s the hypothesis given by Watson-Crick model of DNA replication? What does it mean?
What was his experiment depended on?(3)

A

-They hypothesised that DNA must replicate either conservatively or semi conservatively
This experiment depended on:
-DNA has a nitrogenous base
-Nitrogen has 2 isotopes N14 and N15 (heavier)
-Bacteria will incorporate nitrogen from their growing medium into the DNA
If bacteria grown in N14 medium will only have DNA which only contains this isotope and be lighter
If bacteria grown in N15 medium will only have DNA which only contains this isotope and will be heavier
-When DNA is centrifuged - N14 DNA will settle higher up while N15 will settle further down as its more dense

115
Q

What’s the method of experiment to prove semi conservative replication

A

-Grow normal bacteria-N14 in a growth medium N15 -G0. Centrifuge to measure density
-Transfer this bacteria into growth medium with N14 and let it replicate for one generation -G1. Centrifuge to measure density
- Do the same and let the bacteria replicate for 3 generations - G2 and G3. Centrifuge to measure density
This proves its semi conservative as DNA always has one parental and one newly synthesised DNA.

116
Q

Where are inorganic ions found in the body

A

In solution in the cytoplasm and body fluids

117
Q

5 processes in cells which requires ATP

A

-Metabolic process - used in cells for forming macromolecules from monomers eg starch from glucose or polypeptides from amino acids
-Movement- ATP used in muscle contraction. Gives energy to filaments to slide past one another and shorten the muscle fibre.
-Active transport- Used in changing the shape of carrier molecule which helps in movement against concentration gradient
-Activation of molecules- phosphorylation makes molecules more reactive- lowering activation energy eg Glycolysis
-Secretion- necessary to form lysosomes for cell secretion

Biology A Level (9 decks)

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