Paper 1 and 3: Biological Molecules Flashcards
(150 cards)
1
Q
Monomer [definition]:
A
A molecular subunit that combines to form polymers
2
Q
Polymer [definition]:
A
Large molecule made of smaller subunits called monomers
3
Q
Polymerisation [2]:
A
- The formation of polymers in an organism
- It is a condensation reaction
4
Q
Covalent bonding[2]:
A
- Atoms share a pair of electrons in their outer shells
- Both atoms are filled, making a more stable compound
5
Q
Ionic Bonding [2]:
A
- Ions with opposite charge attract one another
- The ionic bond is the electrostatic attraction between them
6
Q
Hydrogen bonding [4]:
A
- The electrons within a molecule are not evenly distributed but tend to spend more time at one region
- This region becomes more negatively charged than the rest of the molecule
- This means the molecule is polarised/ a polar molecule
- Negative and positive regions attract each other forming a weak bond
7
Q
Hydrogen bonds are…
A
WEAK
8
Q
Condensation reactions [definition]:
A
Molecules react together to form a more complex molecule, a molecule of water is formed in the process
9
Q
Hydrolysis reactions [definition]:
A
The breaking down of large molecules into smaller molecules by the addition of a water molecule
10
Q
Metabolism [definition]:
A
All the chemical processes taking place in a living organism
11
Q
Carbohydrates [definition]:
A
Carbon molecules combined with water
12
Q
What elements are in carbohydrates? [3]:
A
- Carbon
- Hydrogen
- Oxygen
13
Q
Monosaccharide [definition]:
A
Monomers from which larger carbohydrates are made
14
Q
What are some examples of common monosaccharides? [3]:
A
- Glucose
- Galactose
- Fructose
15
Q
What bond is formed in a condensation reaction between two monosaccharides?
A
A glycosidic bond
16
Q
What are some examples of common disaccharides? [3]:
A
- Maltose
- Sucrose
- Lactose
17
Q
Maltose =
A
glucose + glucose
18
Q
Sucrose =
A
glucose + fructose
19
Q
Lactose =
A
glucose + galactose
20
Q
Glucose has two isomers. What is meant by isomer?
A
Same molecular formula but different arrangement of atoms in the molecule
21
Q
What are the isomers of glucose? [2]:
A
- α-glucose
- β-glucose
22
Q
For beta glucose…
A
OH is at the top
23
Q
How are polysaccharides formed?
A
They are formed by the condensation of many glucoes units
24
Q
Testing for reducing sugars [4]:
A
- Add 2cm³ of the food sample to a test tube
- If a sample is not in liquid form grind it up in water
- Add an equal volume of benedict’s solution
- Heat mixture in a gently boiling water bath for 5 mins
25
What is Benedict's reagent/solution?
AN alkaline solution of copper (II) sulphate
26
What happens when a reducing sugar is heated with benedict's reagent?
It forms an insoluble red precipitate of copper (I) oxide
27
Results in benedict's test [2]:
```
Positive= brick red
negative= no colour change
```
28
Testing for non-reducing sugars [5]:
- Use benedict's test, if no result then proceed
- Add 2cm³ of sample to 2cm³ of dilute hydrochloric acid in a test tube
- Add tube to gently boiling water bath for 5 minutes
- Slowly add some hydrogencarbonate solution to the test tube to neutralise the acid
- Re-test using benedict's method
29
Iodine test for starch [3]:
- Place 2cm³ of the sample into a test tube
- Add 2 drops of iodine solution and shake/stir
- The presence of starch is indicated by a blue-black colour
30
Starch structure [5]:
- Alpha glucose
- Amylose 1-4 bonds and few 1-6 amylopectin bonds
- A few branches in the chains of glucose
- Chains make a helix coil
- Insoluble
31
Starch functions and explanations [3]:
- Coils make it a compact molecule, easily stored
- Insoluble,does not affect osmotic balance
- Branches means it is easily hydrolysed
32
Glycogen is also known as...
animal starch
33
Glycogen structure [4]:
- Alpha glucose
- 1-4 bonds of amylose and more 1-6 bonds of amylopectin than in starch
- Highly branched molecule
- Insoluble
34
Glycogen functions and explanations [3]:
- Compact, can store a lot of glucose molecules in a small space
- Chains make it easily hydrolysed
- Insoluble, does not affect osmotic balance
35
Cellulose structure [5]:
- Beta glucose
- 1-4 bonds with amylose
- Alternating glucose molecules by 180 degrees
- Straight chains are unbranched
- Microfibrils bound by hydrogen bonds
36
Cellulose functions and explanations [3]:
- Makes cell wall
- Straight chains make it strong and rigid to support the cell
- Hydrogen bonds between chains make it strong
37
What are the characteristics of lipids? [3]:
- Contain C, H, O
- insoluble in water
- soluble in organic solvents (alcohol, acetone)
38
What are the main groups of lipids? [2]:
- Triglycerides
| - Phospholipids
39
Roles of lipids [4]:
- Good source of energy when oxidised
- Insoluble in water, so waterproof
- Slow conductors heat & electricity, so good insulators
- Protect delicate organs
40
What are the components of triglycerides? [2]:
- 3 fatty acids (tri, duh)
| - Glycerol
41
Draw alpha glucose
```
CH₂OH
|______O Put extra H on everything but top O
/ . \
OH OH
\ /
OH__OH
```
42
How are triglycerides formed? [2]:
- 3 fatty acids form an ester-bond with glycerol
| - Condensation reactions
43
What causes different triglycerides to have different properties?
Variation in the fatty acids
44
Triglycerides [2]:
- 70+ different fatty acids
| - All have carboxyl group (-COOH)
45
What does it mean when a triglyceride is described as saturated? [2]:
- It has no carbon-carbon double bond
| - All carbons are linked to the maximum possible number of hydrogens, it is saturated with hydrogen atoms
46
What makes a triglyceride unsaturated?
Carbon-Carbon double bond
| C=C
47
Triglyceride properties related to structure [4]:
- Good energy source cus high ratio of energy-storing carbon-hydrogen bonds : carbon atoms
- Low energy : mass makes them good storage molecules
- Large, non-polar molecules are insoluble, no affect osmosis
- Release a lot of water when oxidised, good water source
48
Phospholipid components [3]:
- 2 fatty acids
- Glycerol
- phosphate group
49
Phospholipid structure and explanation [4]:
- Phosphate molecules attract water forming a
- Hydrophilic head interacts with the water but not with fat
- Fatty acid molecules repel the water forming a
- Hydrophobic tail orients itself away from water but mixes readily with fat
50
What does a condensation reaction form?
An ester bond
51
Phospholipid structure related to their properties [3]:
- Polar molecule. Hydrophilic head and hydrophobic tail make it able to be in an aqueous environment
- Hydrophilic phosphate head hold it at the surface of the cell membrane
- Phospholipid structure allows it to form glycolipids when reacting with carbohydrates at cell membrane
52
What are glycolipids important for?
cell recognition at the cell-surface membrane
53
Emulsion test for lipids [4]:
- Select grease-free test tube
- Add 5cm³ of ethanol to 2cm³ of sample
- Shake thoroughly to dissolve any lipid in the sample
- Add 5cm³ of water and shake gently
54
Lipid test results [2]:
- Lipid present = milky-white emulsion
| - No lipid = should remain clear
55
Amino acid [definition]:
The basic monomer units which combine to make a polypeptide
56
Amino acid structure [5]:
- Central carbon
- Amine group (-NH₂)
- Carboxyl group (-COOH)
- Hydrogen atom (-H)
- R group
57
The formation of a peptide bond [3]:
- The -OH from one carboxyl group bonds with the H from the other amino acid
- This is a condensation reaction that forms a molecule of water
- A peptide bond is formed between the carbon atom of one amino acid and the Nitrogen atom of the other
58
The primary structure of proteins:
The sequence of amino acids in a polypeptide chain
59
The secondary structure proteins:
α-helices and β-pleated sheets
60
What causes the secondary structure of proteins? [2]:
- Form as a result of hydrogen bonding between different amino acid chains.
- Hydrogen bonds can form between the amine and carboxyl groups or amine and hydroxyl groups
61
Tertiary structure of proteins [2]:
- The 3D structure of protein
| - Bonds in tertiary structure depend on the primary structure primary structure
62
Bonds in tertiary structure of protein [3]:
- Disulfide bridges
- Ionic bonds
- Hydrogen bonds
63
Disulfide bridges in tertiary structure [2]:
- Fairly strong bonds
| - Not easily broken
64
Ionic bonds in tertiary structure [3]:
- Formed between carboxyl group and amino acid
- Weaker than disulfide bonds
- Easily broken by changes in pH
65
Hydrogen bonds in tertiary structure;
Numerous but easily broken
66
Quaternary structure of protein;
The association of several protein chains or subunits into a closely packed arrangement
67
How are dipeptides formed?
By condensing 2 amino acids
68
How are polypeptides formed?
By condensing many amino acids
69
Functional proteins may contain one or more...
polypeptide
70
The biuret test for proteins [3]:
- Place sample in a test tube
- Add an equal volume sodium hydroxide solution
- Add a few drops of dilute copper (II) solution and mix gently
71
Protein test results [2]:
- positive (peptide bond present) = violet
| - negative = solution stays blue
72
What is the function of proteins? [4]:
- Repairs and builds your body's tissues
- Enzymes are proteins
- Antibodies are proteins
- Proteins are a major class of hormones
73
Enzyme [definition]:
Globular proteins that are biological catalysts that speed up the rate of a chemical reaction without getting used up
74
Fibrous proteins [4]:
- They form long chains or fibres
- They have primary, secondary, tertiary and quaternary structures
- Fibrous nature makes them insoluble in water which makes them useful for structure and support
- Fibres form a triple-helix of polypeptide chains. These chains are held together by hydrogen bonds
75
How do enzymes catalyse reactions? [2]:
- They lower the activation energy by creating a different reaction pathway.
- This increases the number of successful collisions = more enzyme-substrate complexes
76
Active site [2]:
- Made up of a relatively small number of amino acids
| - It forms a small depression within the much larger enzyme
77
Substrate [definition]:
The molecule on which the enzyme acts
78
The properties of an enzyme relate to...
the tertiary structure of its active site and its ability to combine with complementary substrate to form an enzyme-substrate complex
79
Specificity of enzymes;
Enzymes are specific and complimentary to the substrate
80
Lock and key model [2]:
- The active site fits perfectly with the substrate
| - The binding of the substrate to the active site is a rigid interaction
81
The induced fit model [3]:
- The active site forms as the enzyme and substrate interact
- The proximity of the substrate leads to a change in the enzyme which forms a functional active site
- The enzyme is flexible and can mould itself around the substrate
82
Factors that affect enzyme action [5]:
- Temperature
- pH
- Enzyme concentration
- Substrate concentration
- Inhibitors
83
Temperature's effect on enzyme activity [4]:
- More effective collisions resulting in more enzyme-substrate complexes being formed
- The rate of reaction increases
- Hydrogen bonds in enzyme begin to break
- This results in the active site changing shape/ denaturing (ROR begins to plateau)
84
Effect of pH on enzyme action [3]:
- A Change in pH alters the charges of the amino acids that make up the enzyme active site
- Substrate can no longer become attached to the active site (enzyme-substrate complexes cannot be formed)
- If there is a significant change in pH the bonds maintaining the enzyme's tertiary structure break, causing the active site to change shape
85
What is the pH a measure of?
A solution's hydrogen ion concentration
86
Effect of enzyme concentration on the rate of reaction [2]:
- As long as there is an excess of substrate the increase of enzyme leads to an increase in the ROR
- If the substrate is limiting then an increase in enzyme will have no effect on the rate of reaction
87
Effects of substrate concentration on the rate of reaction [2]:
- If the enzyme concentration is fixed and substrate concentration is slowly increased the ROR increases in proportion to the substrate increase
- This is because there are many substrates for the enzyme to react with creating more enzyme-substrate complexes
88
Competitive inhibitors [4]:
- They have a molecular shape similar to that of the substrate
- This allows them to occupy the active site of the enzyme
- They compete with the substrates for available active sites
- The inhibitor is not permanently bound to the active site, which means all substrate molecules will eventually occupy an active site
89
Non-competitive inhibitors [3]:
- They attach themselves to the enzyme at a binding site which is NOT the active site
- Upon attaching to the enzyme the inhibitor alters the shape of the enzyme and thus the active site
- As the substrate and inhibitor are not competing for the same site increasing the substrate concentration does not decrease the effect of the inhibitor
90
What does DNA stand for?
Deoxyribonucleic acid
91
Nucleotide structure [3]:
- A pentose sugar
- A phosphate group
- Nitrogen-containing organic base
92
What are the nitrogen-containing organic bases? [5]:
- Cytosine (C)
- Guanine (G)
- Thymine (T)
- Adenine (A)
- Uracil (U)
93
The nitrogen bases are...
specific and complimentary
94
What does A pair up with in DNA?
T
95
What does A pair up with in RNA?
U
96
What does C pair up with?
G
97
What does G pair up with?
C
98
What does T pair up with?
A
99
What are the components of DNA [3]:
- Deoxyribose sugar
- Organic nitrogen base
- Phosphate
100
What is the nitrogen and carbon containing molecule comprising a two ring structure?
Purine
101
What is the nitrogen and carbon containing molecule comprising a one ring structure?
Pyrimidine
102
What are the weak bonds formed between complementary bases?
Hydrogen bonds
103
What is the arrangement of complimentary polynucleotides in the double helix?
Antiparallel in a clockwise direction
104
What are the strong bonds formed between adjacent nucleotides in a polynucleotide?
Phosphodiester bonds
105
What is the number of hydrogen bonds between adenine and thymine?
2
106
What is the number of hydrogen bonds between cytosine and guanine?
3
107
DNA function [2]:
- DNA is an important information-carrying molecules.
| - In all living cells, DNA holds genetic information and passes it from generation to generation
108
DNA structure [2]:
- Specific and complementary base pairing
| - Double helix (2 polynucleotide chains being twisted)
109
The history of DNA:
- In 1953 James Watson and Francis Crick discovered the structure of DNA, following Rosalind Franklin's work on the x-ray
110
Pyrimidine bases [2]:
- Thymine
| - Cytosine
111
Purine bases [2]:
- Adenine
| - Guanine
112
What is the bond between two mononucleotides?
Phosphodiester bonds
113
RNA components [3]:
- Ribose sugar
- Phosphate group
- Nitrogen-containing organic bases
114
What replaces thymine in RNA strands?
Uracil
115
What is the function of RNA? [3]:
- mRNA molecules carry the coding sequences for protein synthesis and are called transcripts
- rRNA molecules form the core of a cell's ribosomes
- tRNA molecules carry amino acids to the ribosomes during protein-synthesis
116
RNA structure [2]:
- It is a single, relatively short, polynucleotide chain
| - has uracil instead of thymine
117
How is DNA adapted to suit its function? [3]:
- Very stable molecule, passes from generation to generation without significant change
- Base pairing leads to DNA being able to replicate and transfer info as mRNA
- Two polynucleotide strands joined by hydrogen bonds, allows them to separate during DNA replication
118
What are the requirements for semi-conservative DNA replication to take place? [4]:
- Enzyme DNA polymerase
- the four types of bases with their pairs
- Chemical energy source
- Both strands of DNA to act as a template
119
Semi-conservative DNA replication ensures...
genetic continuity between generations of cells.
120
Erwin Chargaff [2]:
- Base pairings rule
| - Ratio of base pairs is specific to the species
121
Semi-conservative replication [5]:
- Enzyme DNA helicase breaks down hydrogen bonds that link base pairs of DNA
- Double helix strands unwind
- Polynucleotide strands then act as a template for free base pairs to bind to
- Nucleotides are held together by the condensation of the DNA polymerase to form missing polynucleotide
- Each new dna molecule contains one of the original strands
122
What does ATP stand for?
Adenosine triphosphate
123
Components of ATP [3]:
- Adenine
- Ribose sugar
- 3 Phosphate groups
124
What enzyme catalyses the hydrolysis of ATP to adenosine diphosphate (ADP) and an inorganic phosphate group (Pi) ?
ATP hydrolase
125
Hydrolysis of ATP [2]:
- The hydrolysis of ATP can be coupled to energy-requiring reactions within cells.
- The inorganic phosphate released during the hydrolysis of ATP can be used to phosphorylate other compounds, often making them more reactive.
126
ATP is re-synthesised [2]:
- Re-synthesised by the condensation of ADP and Pi.
| - This reaction is catalysed by the enzyme ATP synthase during photosynthesis, or during respiration
127
Properties of water [5]:
- Metabolite
- Solvent
- Temperature control
- Cohesion
- Surface tension
128
Water as a metabolite;
metabolite in many metabolic reactions, including
| condensation and hydrolysis reactions
129
Water as a solvent;
Its an important solvent in which metabolic reactions occur
130
Cohesion in water molecules [2]:
- Water molecules ‘stick’ together. This helps transport water in plants and other organisms
- Water cohesion leads to surface tension
131
Temperature control in water [4]:
- Has a high latent heat of vaporization
- High specific heat capacity
- This water in and around our cells absorbs a lot of heat energy without its temperature increasing much.
- The water ‘buffers’ the heat change
132
Surface tension in water [3]:
- Because of its hydrogen bonds, water has a high surface tension
- Makes water behave as if there is a skin where the water meets air.
- This allows small animals to live on the surface of water bodies
133
Where are inorganic ions found?
Inorganic ion occur in cytoplasm and bodily fluids, some in high concentration and some in low concentration
134
Sodium ions [2]:
- Na⁺
| - Important in helping other molecules move across membranes (co-transport)
135
Iron ions [2]:
- Fe²⁺, Fe ³⁺
| - Important in haemoglobin, cus they carry oxygen
136
Phosphate ions [3]:
- PO₄³⁻
- Used in ATP (atp contains phosphate groups)
- RNA & DNA have reactions with phosphate groups to form polynucleotides
137
Ester bonds =
Between fatty acid and glycerol
138
Glycosidic bonds=
Between carbohydrates
139
DNA transcription step 1
DNA helicase moves along the strand breaking H bonds btwn complementary bases, to separate the strands
140
DNA transcription step 2
mRNA polymerase moves along, joining free RNA nucleotides to DNA template via complementary base pairing
141
DNA transcription step 3
Phosphodiester bonds form between RNA nucleotides by condensation reaction
142
DNA transcription step 4
Splicing of pre-RNA
143
DNA transcription step 5
Hydrogen bonds reform btwn complementary bases
144
DNA translation step 1
mRNA attaches to ribosomes
145
DNA translation step 2
mRNA has a codon (triplet bases that determine amino acid sequence)
146
DNA translation step 3
tRNA binds to complementary anticodon cus complementary base pairing (a-u c-g)
147
DNA translation step 4
A 2nd trna with complimentary anticodon binds to 2nd codon on mrna by complementary base pairing
148
DNA translation step 5
Peptide bond forms btwn 2 aminoacids by condensation reaction (energy is required)
149
DNA translation step 6
1st tRNA is removed & process repeats until it reaches a stop codon
150
Where does the protein go after translation?
To the rough endoplasmic reticulum
