TOPIC 1 Biological Molecules Flashcards
1
Q
Examples of monomers
A
Monosaccharides
Amino acids
nucleotides
2
Q
Examples of polymers
A
Carbohydrates
Proteins
Nucleic acids
3
Q
What type of sugar is glucose
A
Hexose
4
Q
How many types of glucose are there
A
2
5
Q
What are the different types of glucose
A
- Alpha Glucose
- Beta Glucose
6
Q
Condensation reactions join which molecules?
A
Monosaccharides
7
Q
What is a condensation reaction?
A
When 2 molecules join together with the formation of a new chemical bond, releasing a water molecule
8
Q
What type of chemical bond forms between 2 monosaccharides?
A
Glycosidic
9
Q
What is formed when 2 monosaccharides join together?
A
Disaccharide
10
Q
What is Sucrose made from?
A
Alpha glucose and Fructose
11
Q
What 2 molecules make lactose?
A
Alpha glucose and galactose
12
Q
What is a hydrolysis reaction?
A
When 2 molecules are broken apart using a water molecule
13
Q
What is broken down by hydrolysis to form monosaccharides?
A
Carbohydrates
14
Q
Name 3 hexose monosaccharides
A
- Glucose
- Fructose
- Galactose
15
Q
Describe the Benedict’s test for reducing sugars
A
- Add an equal volume of Benedict’s to a sample
- Heat the mixture in an electric water bath at 100°c for 5 minutes
- Positive result: colour change from blue to orange and Brick red precipitate forms
16
Q
Describe the Benedict’s test for Non - reducing sugars
A
- Negative result: Benedict’s reagent remains blue
- Hydrolyse non- reducing sugars e.g sucrose into their monomers by adding 1cm^3 of HCl
- Heat in a water bath for 5 minutes
- Neutralise the mixture using sodium carbonate solution
- Proceed with Benedict’s test as usual
17
Q
Describe the test for starch
A
- Add iodine solution
- Positive result = colour change from orange to blue / black
18
Q
How would colorimetry be used to give qualitative results for the presence of sugars and starch ?
A
- Make standard solutions with known concentrations.
- record absorbance or % transmission values
- plot calibration curve (absorbance - y axis and concentration- x axis)
- record absorbance or % transmission values of unknown samples
- use calibration curve to read off concentration
19
Q
How do you test for lipids ?
A
- dissolve solid samples in ethanol
- Add an equal volume of water and shake
- Positive result = milky white emulsion forms
20
Q
How do triglycerides form?
A
Condensation reactions between 1 molecule of glycerol and 3 fatty acids forms ester bonds
21
Q
What are 3 differences between saturated and unsaturated fatty acids?
A
- Saturated contain only single bonds
whilst unsaturated contains C=C double bonds - Saturated have higher melting points and are solids at room temperatures whilst unsaturated have lower melting point and are liquids at room temperature
- saturated are straight chain molecules that have many contact points
whilst unsaturated are “kinked” molecules that have fewer contact points
22
Q
Relate the structure of triglycerides to their functions
A
- high energy : mass ratio = high calorific value from oxidation
- insoluble hydrocarbon chain = no effect on water potential of cells and used for water proofing
- slow conductor of heat = thermal insulation
- less dense than water = buoyancy of aquatic animals
23
Q
Describe the structure and functions of phospholipids
A
Amphipathic molecule: glycerol backbone attached to 2 hydrophobic fatty acid tails and 1 hydrophilic polar phosphate head
- forms phospholipid bilayer in water = component of membranes
- tails can splay outwards = waterproofing
24
Q
Compare phospholipids and triglycerides
A
• both have glycerol backbone
• both formed by condensation reactions
• both contain the elements C, H , O
25
Contrast phospholipids and triglycerides
• phospholipids have 2 fatty acids and 1 phosphate group attached
triglycerides have 3 fatty acids attached
• phospholipids have a hydrophobic tail and a hydrophilic head
triglycerides are entirely hydrophobic
• phospholipids are used primarily in membrane formation
triglycerides are used primarily as a storage molecule
26
Are phospholipids and triglycerides polymers?
No - they are macromolecules
27
Why is water a polar molecule ?
O is more electronegative than H
so attracts the electron density in the covalent bond more strongly
28
what are 4 important properties of water?
1. high specific heat capacity
2. solvent / metabolite for chemical reactions in the body
3. high latent heat of vaporisation
4. cohesion between molecules
29
why is water significant to living organisms ?
• solvent for polar molecules during metabolic reactions
30
What are organic ions and where are they found in the body ?
• ions that do not contain carbon atoms
• found in cytoplasms and extracellular fluid
• May be in high or very low concentrations
31
Explain the role of hydrogen ions in the body
• High concentration of H+ = low acidic PH
• H+ ions interact with H - bonds and ionic bonds in tertiary structure of proteins, which can cause them to denature
32
Explain the role of iron ions in the body
- Fe2+ bonds to porphyrin ring to form haem group in haemoglobin
- haem group has binding site to transport 1 molecule of O2 around body in bloodstream
- 4 haem groups per haemoglobin molecule
33
Explain the role of sodium ions in the body
• involved in co transport for absorption of glucose and amino acids in lumen of gut
• involved in propagation of action potentials in neurons
34
Explain the role of phosphate ions in the body
Component of:
- DNA
- ATP
- NADP
- cAMP
35
What is the general structure of an amino acid?
- COOH (carboxyl group)
- R variable
- NH2 amine group
36
How do you test for proteins in a sample?
Biuret’s tests :
- confirms presence of peptide bonds
- positive result = colour change from blue to purple
37
How many amino acids are there?
How do they differ?
20
Differ only by their ‘R’ groups
38
How do dipeptides and polypeptides form?
Condensation reaction forms peptide bond and eliminates molecule of water
• dipeptide : 2 amino acids
• polypeptide: 3 or more amino acids
39
How many levels of protein structure are there?
4
40
Define primary structure of a protein?
• sequence, number and type of amino acids in the polypeptide
• Determined by sequence of codons on mRNA
41
Define secondary structure of a protein
• hydrogen bonds form between O- attached to C=O and H + attached to -NH
42
Define the 2 types of of secondary protein structure
alpha helix -
• all N-H bonds on same side of protein chain
• spiral shape
• H-bonds parallel to helical axis
beta pleated sheet -
• N-H & C=O groups alternate from one side to the other
43
Define tertiary structure of a protein.
Name the bonds present
3D structure formed by further folding of polypeptide
• disulphide bridges
• ionic bonds
• hydrogen bonds
44
Describe each type of bond in the tertiary structure of proteins
• disulphide bridges :
strong covalent S-S bonds between molecules of the amino acid cysteine
• ionic bonds :
relatively strong bonds between charged R groups (pH changes cause these bonds to break)
• hydrogen bonds :
numerous and easily broken
45
define quaternary structure of a protein
• functional proteins may consist of more than one polypeptide
• precise 3D structure held together by the same types of bond as tertiary structure
• may involve addition of prosthetic groups
e.g metal ions or phosphate groups
46
Describe the structure and function of globular proteins
• spherical and compact
• hydrophilic R groups face outwards and hydrophobic R groups face inwards = usually water soluble
• involved in metabolic processes e.g enzymes and haemoglobin
47
Describe the structure and function of fibrous proteins
• can form long chains or fibres
• insoluble in water
• useful for structure and support e.g collagen in skin
48
What are enzymes?
• biological catalysts for intra and extracellular reactions
• specific tertiary structure determines shape of active site, complementary to a specific substrate
• formation of enzyme substrate complexes lowers activation energy of metabolic reactions
49
Explain the induced fit model of enzyme action
• shape of active site is not directly complementary to substrate and is flexible
• conformational change enables enzyme substrate complexes to form
• this puts strain on substrate bonds, lowering activation energy
50
How have models of enzyme action changed?
• initially lock and key model:
rigid shape of active site complementary to only 1 substrate
• currently induced fit:
also explains why binding all allosteric sites can change shape of active site
51
what are 5 factors that affect the rate of enzyme-controlled reactions?
- enzyme concentration
- substrate concentration
- concentration of inhibitors
- pH
- temperature
52
Describe competitive inhibitors
• similar shape to substrate = bind to active site
• do not stop reaction: enzyme substrate complex forms when inhibitor is released
• increasing substrate concentration decreases their effect
53
Describe non competitive inhibitors
• bind at allosteric binding site
• may permanently stop reaction: triggers active site to change shape
• increasing substrate concentration has no impact on their effect
54
How do you calculate the rate of reaction from a graph?
• calculate the gradient of line or gradient of tangent to a point
• initial rate: draw tangent at t=0
55
How do you calculate the rate of reaction from raw data?
change in concentration of product or reaction time
56
why is it advantageous to calculate initial rate?
represents maximum rate of reaction before concentration of reactants decreased & ‘end product inhibition’
57
what is the formula for pH?
pH = -log10 [H+]
58
Name the pentose sugars in DNA and RNA
DNA: deoxyribose
RNA: ribose
59
what is the role of DNA in living cells?
Base sequence of genes codes for functional RNA and amino acid sequence of polypeptides
genetic information: determines inherited characteristics = influences structure and function of organisms
60
Define a condensation reaction
joining 2 molecules together creating a chemical bond, eliminating a water molecule
61
Define a hydrolysis reaction
Breaking a chemical bond using water
62
Name 3 monomers
Amino acids
Nucleotides
glucose
63
Name 3 polymers
proteins
DNA
polysaccharides
64
give 2 examples of a hydrolysis reaction
polypeptides into amino acids
lipids into fatty acids and glycerol
65
give 2 examples of a condensation reaction
monosaccharides into polysaccharides
nucleotides into nucleic acid(DNA)
66
What are monosaccharides?
monomers for carbohydrates
67
what is the general formula for a monosaccharide
CH2On
68
What are 3 examples of monosaccharides
glucose
galactose
fructose
69
What is the formula for glucose
C6H12O6
70
What makes
1. Maltose
2. sucrose
3. lactose
1. maltose = glucose + glucose
2. Sucrose = glucose + fructose
3. lactose = glucose + galactose
71
What are polysaccharides
long chains of monosaccharides joined by glycosidic bonds in condensation reactions
72
what is starch
- long chains of alpha glucose
- chains can be coiled into an alpha helix —> compact
- insoluble (no effect on osmosis) —> good for storage
- branched to increase surface area so enzymes can hydrolyse the bonds quickly to provide glucose for respiration
73
Define disaccharides
two monosaccharides joined together by glycosidic bonds
74
what is starch made from and what do they allow regarding the structure?
- amylase for coiling
- amylopectin for branching
75
Describe glycogen
long chains of alpha glucose
shorter and more branched than starch
found in animal cells (liver and muscle cells)
very highly branched so can be broken down quickly for use of alpha glucose in respiration
insoluble
76
Describe cellulose
long chains of beta glucose
straight, unbranched chains that run parallel to each other and are cross linked by hydrogen bonds
in the cell walls of plants
77
Why do we add extra steps when testing for non reducing sugars?
to break the glycosidic bonds and turn the disaccharides back into monomers so that we can carry out the benedicts test
