biological molecules Flashcards
1
Q
Monomer
A
The smaller units from which larger molecules are made
2
Q
Polymer
A
Molecules made from a large number of monomers joined together
3
Q
Monosaccharide
A
The monomers from which larger carbohydrates are made
e.g. glucose, fructose, galactose
4
Q
Disaccharide
A
Formed by the condensation of two monosaccharides
- held together by a glycosidic bond
e.g. maltose, sucrose, lactose
5
Q
Cellulose
A
Polysaccharide in plant cell walls formed by the condensation of β-glucose
5
Q
Polysaccharide
A
Formed by the condensation of many glucose units
- held by glycosidic bonds
e.g. starch, glycogen, cellulose
6
Q
Glycogen
A
Polysaccharide in animals formed by the condensation of
α-glucose
7
Q
Starch
A
- Polysaccharide in plants formed by the condensation of α-glucose
- contains two polymers - amylose and amylopectin
8
Q
Glycosidic bond
A
C–O–C link
- between two sugar molecules formed by a condensation reaction
- it is a covalent bond
9
Q
Amylose
A
Polysaccharide in starch
- made of α-glucose
- joined by 1,4-glycosidic bonds
- coils to form a helix
10
Q
Amylopectin
A
Polysaccharide in starch
- made of α-glucose
- joined by 1,4 and 1,6-glycosidic bonds
- branched structure
11
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
12
Q
Hydrolysis reaction
A
- A reaction that breaks a chemical bond
- between two molecules
- involves the use of a water molecule
13
Q
Fibrils
A
Long, straight chains of β-glucose
glucose held together by many hydrogen bonds
14
Q
Triglyceride
A
Formed by the condensation of one molecule of glycerol and three molecules of fatty acids
- forming 3 ester bonds
15
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
16
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
17
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
18
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
19
Q
Primary structure
A
The sequence of amino acids on a polypeptide chain
20
Q
Secondary structure
A
- The folding or coiling
- to create a β pleated sheet or an α helix
- held in place by hydrogen bonds
21
Q
Tertiary structure
A
The further folding
- to create a unique 3D shape
- held in place by hydrogen, ionic and sometimes disulfide bonds
22
Q
Quaternary structure
A
More than one polypeptide chain in a protein
23
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
24
What is the effect of temperature on enzyme-
controlled reaction
- 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.
25
What is the effect of pH on enzyme-controlled
reaction
- 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
26
What is the effect of substrate concentration on enzyme-controlled reaction
- 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
27
What is the effect of enzyme concentration on enzyme-controlled reaction
- 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.
28
Hydrophilic
The ability to mix, interact or
attract water
29
Ester bond
–COO– chemical bond
formed between glycerol and fatty acids
30
Hydrophobic
The tendency to repel and not mix with water
31
Glucose
Monosaccharide that exists as two isomers
β glucose and α glucose
32
Galactose
An example of a monosaccharide that forms lactose
33
Fructose
An example of a monosaccharide that forms sucrose
34
Isomer
Molecules with the same molecular formula
- but the atoms are arranged differently
35
Maltose
Disaccharide
formed by the condensation of two glucose molecules
36
Lactose
Disaccharide
formed by the condensation of a glucose molecule and a galactose molecule
37
Sucrose
Disaccharide
formed by the condensation of a glucose molecule and a fructose molecule
38
Polypeptide
Polymer chain of a protein
- made up of amino acids
- bonded together by peptide bonds following condensation reactions
39
Amino acid
The monomer of a protein formed from C,H,O,N
contains a carboxyl group, amine group and an R group
40
Carboxyl group
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
41
Amine group
NH2 group found on amino acids
42
R group on amino acids
The variable group
the part of each of the 20 amino acids that is different
43
α helix
A secondary structure in proteins
- a coiled shape held in place by hydrogen bonds
44
β pleated sheet
A secondary structure in proteins
- a folded, pleated shape
- held in place by hydrogen bonds
45
Hydrogen bonds
Weak bond
- forms between H and O
- in many biological molecules e.g. proteins, water, DNA, tRNA
46
Ionic bonds
A bond that forms between the R groups of different amino acids
- in the tertiary structure of proteins
47
Disulfide bonds
A strong covalent bond
- between two sulfur atoms in the R groups of different amino acids
- in the tertiary structure of proteins
48
Active site
Unique-shaped part of an enzyme that the substrate binds to
49
Activation energy
The minimum amount of energy required for a reaction to occur
50
Enzyme-substrate complex
forms when an enzyme and substrate collide and bind resulting in a lowered activation energy
51
Enzyme-inhibitor complex
The structure that forms when an enzyme and inhibitor collide and bind
- prevents enzyme-substrate complexes from forming
51
Saturated fatty acid
A long hydrocarbon chain with a carboxyl group at one end
only **single bonds** between carbon atoms
52
Unsaturated fatty acid
A long hydrocarbon chain with a carboxyl group at one end
at least one **double bond** between carbon atoms
53
Polar molecule
A molecule that has an uneven distribution of charge
54
Phospholipid bilayer
- Phospholipids have two charged regions
- in water, they are positioned so that the heads are exposed to water and the tails are not
55
Plasma membrane
- Phospholipid bilayer
- cell surface membranes and organelle membranes
56
Reducing sugar
sugars that can reduce Cu ions
add Benedict’s reagent to Cu ions in the form of copper (I) oxide
- which forms a brick-red precipitate
57
Test for reducing sugar
* Add Benedict's reagent
* heat
* observe green/yellow/orange/brick red precipitate
58
How does the structure of a triglyceride relate to it's function?
- 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
- have a relatively low mass
59
How does the structure of a phospholipid relate to it's function?
- 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.
60
How does the structure of a triglyceride and phospholipid differ?
A phospholipid has one less fatty
acid chain
- which is replaced by a phosphate group
61
Non-reducing sugar
a sugar unable to reduce Cu2+
- the glycosidic bond must be hydrolysed to expose the reducing group
e.g. sucrose
62
Test for non-reducing sugar
- Following a negative Benedict's test
- boil sample in acid and then neutralise with alkaline
- add Benedict's reagent and heat
- observe orange/brick red colour
63
Test for starch
Add iodine
turns blue/black
64
Test for lipids
Add ethanol and shake to dissolve
then add water
white emulsion forms
65
Test for protein
Add biuret
- turns purple
66
Nucleotide
The monomer of DNA and RNA
- contains a pentose sugar, a phosphate group and a nitrogenous base
67
Nitrogenous base
Part of a nucleotide
adenine, guanine, cytosine, thymine and uracil
68
DNA nucleotide
The monomer of DNA
- contains a deoxyribose sugar, a phosphate group and a nitrogenous base
69
Polynucleotide
- DNA polymer
- many nucleotides joined together via a condensation reaction
- joined by phosphodiester bonds
70
Complementary base pairs
The base pairs that align opposite each other and form hydrogen bonds
adenine and thymine/uracil guanine and cytosine
70
Phosphodiester bond
Bond joining two nucleotides together
- forms between a phosphate group and the pentose sugar
71
Ribose
pentose sugar
found in RNA nucleotide and ATP
72
Uracil
Nitrogenous base
found in RNA instead of thymine
73
mRNA
a copy of a gene
- single-strand polymer of RNA
74
tRNA
found only in the cytoplasm
- single-stranded but folded to create a shape that looks like a cloverleaf
- held in place by hydrogen bonds
75
rRNA
rRNA combines with protein to make ribosomes
76
DNA template strand
- 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
77
DNA polymerase
An enzyme in DNA replication
joins together adjacent nucleotides
78
Semi-conservative replication
DNA replication is semi- conservative replication
one strand is from the parental DNA and one strand is newly synthesised
79
DNA helicase
- 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
80
Large latent heat of vaporisation
- 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
81
High specific heat capacity
- 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
82
Metabolite
Water is involved in many reactions such as photosynthesis, hydrolysis, and condensation reactions
83
Solvent
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
84
Strong cohesion
- 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
85
ATP synthase
Enzyme that catalyses the synthesis of ATP from ADP + Pi
86
ATP hydrolase
Enzyme that catalyses the hydrolysis of ATP into ADP +Pi
86
Phosphorylation
The addition of a phosphate group to a molecule
making the molecule more reactive/it gains energy
87
Structure of water
Water is a polar molecule
the oxygen atom is slightly negative
the hydrogen atoms are slightly positive
88
RNA nucleotide
monomer of RNA
composed of a phosphate group, ribose and a nitrogenous base has the base uracil instead of thymine
88
Dipeptide
Two amino acids bonded together by a peptide bond
formed by a condensation reaction
89
Role of hydrogen ions
determine the pH
- the more hydrogen ions, the more acidic the conditions are
- an important role in chemiosmosis in respiration and photosynthesis
90
Role of iron ions
a compound of haemoglobin involved in oxygen transport
91
Role of sodium ions in co-transport
involved in co-transport for absorption of glucose and amino acids in the ileum
92
Role of phosphate ions
as a component of DNA, RNA and ATP
phosphodiester bond in DNA and RNA forms between the phosphate group and the pentose sugar
