MTC Flashcards
(99 cards)
1
Q
Briefly describe the importance of functional groups
A
Functional groups dictate the biological function of drugs by playing a major role in binding (lock and key model)
2
Q
What is polarisation?
A
Different atoms have different electronegativities (electron attractions), this causes different polarities to form in molecules
3
Q
What are the stages of drug action?
A
- Absorption (into bloodstream)
- Distribution (to target sites)
- Binding (to target site)
- Metabolism
- Excretion
4
Q
What qualities does a molecule need to be absorbed and distributed (in blood)?
A
- Non-polar (hydrophobic) to absorb through GIT membrane
- Polar (hydrophilic) to dissolve in aqueous blood
5
Q
What are the two main inhibition modes? Briefly describe
A
- Reversible inhibition: inhibition occurs due to intermolecular interaction– can be reversed
- Irreversible inhibitions: inhibition occurs due to covalent bonding– very difficult to reverse
6
Q
Lipinski’s Rule predicts whether a drug can be orally bioavailable or not. What are the four crietia?
A
- Hydrogen Bond donors (OH, NH) < 5
- Hydrogen Bond acceptors (O, N) <10
- Molecular weight <500g/mol
- Partition coefficient log P <5
7
Q
What is the pKa value?
A
The pKa value is a measure of how readily an acid will dissociate or how readily a base will protonate
8
Q
Differentiate between a strong acid and a weak acid
A
Strong acids differentiate completely in water; weak acids differentiate incompletely in water
9
Q
What does a high and low pKa indicate?
A
High pKa -> strong base
Low pKa -> strong acid
10
Q
Differentiate between pH and pKa
A
pH is a measure of the proton concentration of an environment– this can be altered
pKa is a measure of the strength/weakness of an acid/base– it is a characteristic of molecule or functional group
11
Q
Name one functional group present in an acidic and basic functional group respectively
A
Acidic – carboxylic acid (-COOH)
Basic – amino groups (-NH)
12
Q
In what form do functional groups diffuse across the plasma membrane?
A
Functional groups must be neutral (non-ionised) in order to diffuse through the lipid bilayer
13
Q
Under what conditions can an acidic drug be absorbed?
A
The pH < pKa as the acid would be protonated in this state (HA)
14
Q
Under what conditions can a basic drug be absorbed?
A
The pH > pKa as the base would be deprotonated in this state (B)
15
Q
What is a prodrug?
A
A prodrug is an inactive precursor to the active form that is metabolised into the active drug
16
Q
What is a conformation?
A
A conformation is a geometric change caused by the rotation of a single bond
17
Q
Name the two possible conformations. Which one is the most stable and why?
A
Staggered and eclipsed conformations. Staggered conformations are the most stable geometrical conformation as hydrogens are as far away from each other as possible (minimising electron repulsion)
18
Q
What is isomerism?
A
Isomerism occurs in molecules that have identical molecular formulae but different structures
19
Q
What is stereoisomerism?
A
Stereoisomerism occurs when there is difference in 3D structure in molecules with identical molecular formulae
20
Q
What are enantiomers?
A
Enantiomers are stereoisomers that are mirror images and non-superimposable
21
Q
What defines a chiral centre?
A
A chiral centre is a carbon that has four single bonds, each to unique substituent groups
22
Q
What are diastereoisomers?
A
Stereoisomers that are incomplete mirror images of each other
23
Q
The substituents of an enantiomer increase in priority in a clockwise direction. What enantiomer is this?
A
It is a R-enantiomer (rectus)
24
Q
The substituents of an enantiomer increase in priority in a counter-clockwise direction. What enantiomer is this?
A
It is a S-enantiomer (sinister)
25
What is a racemic mixture?
A mixture of both R and S enantiomers in a varying ratio
26
What defines a D-amino acid and a L-amino acid?
D-amino acids have the amino group (-NH2) on the right side of the Fischer projection
L-amino acids have the amino group (-NH2) on the left side of the Fischer projection
27
What enantiomer of an amino acid occurs naturally?
L-amino acids
28
What defines a D-carbohydrate and a L-carbohydrate?
D-carbohydrates have the hydroxyl (-OH) on the right side of the Fischer projection
L-carbohydrates have the hydroxyl (-OH) on the left side of the Fischer projection
29
What enantiomer of carbohydrates occur naturally?
D-carbohydrates
30
What is an anomer?
A diastereoisomer of cyclic carbohydrates
31
Name the four major compounds in order of energy source prioritisation
Sugars, fatty acids, amino acids and nucleotides
32
What is a condensation reaction and what is its purpose?
A chemical reaction where water is released. Condensation reactions join monomer to create polymers
33
What is hydrolysis and what is its purpose?
A chemical reaction where water is added. Hydrolysis separate polymers into monomers
34
What are monosaccharides, disaccharides, oligosaccharides and polysaccharides?
- Monosaccharides: 3 or more carbon chain sugars (monomers)
- Disaccharides: two monosaccharides linked by glycosidic bond
- Oligosaccharides: 3-20 monosaccharide sugar
- Polysaccharides: polymers made up of hundreds and thousands monosaccharides
35
What is a glycosidic linkage?
A condensation reaction between two monosaccharides that creates a bond (disaccharide)
36
What are fats and oils made up of?
Fats and oils consist of triglycerides: glycerol molecule with fatty acid chains
37
Describe saturated and unsaturated fats
- Saturated: fatty acid hydrocarbon chains have all bonds filled (i.e. all single bonds)
- Unsaturated: fatty acid chains may contain a double bond (i.e. not all carbon bonds filled)
38
How are steroids synthesised?
Steroids are synthesised from cholesterol
39
What are cholesterols, steroids and lipids synthesised from?
They're all synthesised from glucose
40
Name the key constituents of an amino acid
Alpha-carbon, amino group (-NH2), carboxyl group (-COOH), hydrogen and the side chain
41
What monomers create proteins?
Proteins are polymers of amino acid monomers
42
What is primary protein structure and how is it formed?
Primary protein structure is the order of amino acids (peptide chain). This is formed through peptide linkages which occur from condensation reactions
43
What is secondary protein structure and how is it formed?
Secondary protein structure is the organisation of the peptide chains-- it is formed by intermolecular interaction between amino and carboxyl groups
44
What is tertiary protein structure and how is it formed?
Tertiary protein structure is formed by the folding and bending of secondary protein structure to create a 3D subunit structure. This occurs due to intermolecular interaction between the side chains of the amino acids
45
What is quaternary protein structure and how is it formed?
Quaternary protein structure is the macromolecular structure formed by the interaction of protein subunits-- this is facilitated by side chains and intermolecular interactions
46
What is an example of a secondary protein structure?
Alpha helix (tubular structure) or beta pleated sheet (flat shape of parallel peptide chains)
47
What are some factors that can influence protein structure?
Temperature and pH (secondary, tertiary and quaternary structure)
Amino acid sequence (primary structure)
48
What is the biological function of nucleic acids?
To encode and transmit biological information
49
What is a nucleoside?
A nucleoside is made up of a nitrogenous base and pentose sugar (ribose or deoxyribose)
50
What is a nucleotide?
A nucleotide is made up of a nitrogenous base, pentose sugar (ribose or deoxyribose) and phosphate group
51
What are the five nitrogenous bases?
Adenine, Cytosine, Thymine, Guanine, Uracil
52
What are the two main types of nitrogenous bases and how do they differ?
Purines have a two ring structure; pyrimidines have a single ring structure
53
What pairs of bases 'bind' together in DNA?
A--T; C---G
54
Describe the Fluid Mosaic Model
The Fluid Mosaic Model simply describes the mosaic nature of the cell membrane due to all the lipids, proteins, carbohydrates and cholesterol. The composition varies, dependent on function.
55
Name the four types of lipid that make up the membrane
Phosphatidylcholine and sphingolipids; phosphatidylethanonlanine and phosphatidylserine
56
Why is membrane fluidity essential?
Membrane fluidity is essential to function. If too fluid, the cell becomes leaky; if not fluid, there is no movement of solutes across the membrane
57
What occurs to membrane fluidity in hot and cold temperatures?
In hot temperatures, the membrane fluidity increases
| In cold temperature, the membrane fluidity decreases
58
What happens to membrane fluidity when phospholipids possess long or short fatty acid chains?
Long fatty acid chains cause membrane fluidity to decrease
Short fatty acid chains cause membrane fluidity to increase
59
What happens to membrane fluidity in the presence of saturated or unsaturated fatty acids?
Saturated fatty acids cause the membrane fluidity to decrease
Unsaturated fatty acids cause the membrane fluidity to increase
60
How does cholesterol act as membrane fluidity 'buffer' in hot and cold temperatures?
In hot temperatures, cholesterol attracts the phospholipids closer together to prevent excessive fluidity
In cold temperatures, cholesterol prevents clustering of phospholipids to prevent stiffness of the membrane
61
Name three types of membrane proteins. Briefly describe
- Peripheral protein: bind to polar heads of bilayer or to integral proteins (found on one side of the bilayer)
- Integral protein: amphipathic nature allows this protein to integrate into the bilayer (spans across the bilayer)
- Lipid anchored protein: non-polar lipids anchor these proteins into the bilayer
62
What is a glycocalyx?
The glycocalyx is the carbohydrate section of a glycolipid/glycoprotein. It is usually an oligosaccharide
63
What is the function of tight junctions?
Tight junctions prevent substrates from passing inbetween cells-- they must be filtered through cells
64
What is the function of desmosomes?
Desmosomes protect the integrity of body surfaces and organs by forming plaque structures to hold cells tight together
65
What is the function of gap junctions?
Gap junctions have channel proteins (connexions) that allow the movement of ions and small molecules between adjacent cells
66
What are the 4 main processes of membrane transport? Which ones are active/passive?
1. Diffusion -- passive
2. Facilitated diffusion -- passive
3. Primary active transport -- active
4. Secondary active transport -- active
67
How can water enter/exit a cell?
Water can cross the cell membrane either through diffusion (osmosis) or through facilitated diffusion (aquaporin channel proteins)
68
What concentration gradient does water follow when diffusing?
Water will always diffuse towards the highest solute concentration
69
Describe how a uniporter, symporter and antiporter function
Uniporter: transport one type of molecule in a single direction
Symporter: transport multiple types of molecules in a single direction
Antiporter: exchange one type of molecule for another (transport in opposite directions)
70
Briefly describe how a gated ion channel works
A stimulus (ligand or voltage) causes the protein channel to undergo a conformational change to either open/close a pore that allows ions to travel through the cell membrane
71
Define primary active transport
Primary active transport is where energy is directly used by a transporter to transport solutes
72
Define secondary active transport
Secondary active transport relies on primary active transport to establish an ion gradient. This ion gradient is then utilised to concentrate another solute
73
What type of active transport does Na/K-ATPase utilise? Briefly describe its mechanism of action
Primary active transport.
- 3 Na+ bind to the transporter (intracellular)
- Binding causes transporter to undergo a conformational change that releases the sodium ions into the extracellular environment
- 2 K+ bind to the transporter (extracellular)
- Binding causes conformational change that releases potassium ions into intracellular environment
74
What is endocytosis?
Endocytosis is when the cell membrane invaginates to form a pocket around specific molecules. This pocket deepens to eventually form a vesicle which then migrates deeper into the cell
75
What are the 3 main types of endocytosis?
Phagocytosis: cellular eating of large particles (vesicles fuse with lysosomes and contents are digested)
Pinocytosis: cellular drinking of small, dissolved substances
Receptor-mediated endocytosis: receptors on cell surface bind a target material and disconnect once a vesicle is formed
76
Briefly describe the action of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR). Explain its role in Cystic Fibrosis and Cholera.
The CFTR is a Cl- ion channel that is ligand-gated and regulated by phosphorylation.
In CF, the CFTR becomes mutated and can not function. Hence Cl- can not be transported from the cell, which leads to an extracellular buildup of mucus
In cholera, bacterial toxins hyper-activate the CFTR. This causes the cell to rapidly excrete Cl-. This creates a hypertonic osmotic pressure and hence water vacates from cells into the intestinal lumen (dehydration and diarrhea)
77
What is metabolism?
The sum total of chemical reactions in an organism
78
Define a catabolic pathway
A catabolic pathway is where molecules are broken down
79
Define an anabolic pathway
An anabolic pathway is where molecules are synthesised
80
Define an exergonic reaction. Refer to Gibbs Free energy, complexity and entropy.
An exergonic reaction is reaction where Gibbs Free energy is released (-delta G). It is usually catabolic and leads to decrease in complexity (increased entropy)
81
Define an endergonic reaction. Refer to Gibbs Free energy, complexity and entropy.
An endergonic reaction is a reaction where Gibbs Free energy is consumed (+delta G). It is usually anabolic and leads to an increase in complexity (decreased entropy)
82
What is Gibbs Free energy?
Gibbs Free energy is essentially the energy contained within chemical bonds
83
Define activation energy
Activation energy is the initial amount of energy required for a chemical reaction to proceed
84
How do enzymes influence activation energy?
Enzymes effectively decrease the activation energy required for a chemical reaction to proceed
85
In an exergonic reaction, what must the difference in enthalpy (H) be?
Exergonic reactions have negative Gibbs Free energy, hence enthalpy change must be negative
86
In an endergonic reaction, what must the difference in enthalpy (H) be?
Endergonic reactions have positive Gibbs Free energy, hence enthalpy change must be positive
87
What are the 3 basic steps of enzyme action?
1. Enzyme binds target substrate in active site to form enzyme-substrate complex
2. Conversion of enzyme-substrate complex into enzyme-product complex
3. Release of product from enzyme
88
What are some ways in which an enzyme can convert a substrate into a product?
Enzymes can change 3D shape; twist/stretch the substrate; orientate the substrate to expose reactive groups; can bind cofactors to the substrate or can add charges to the substrate to prime it
89
What 2 factors influence the direction of a chemical reaction?
The change in Gibbs Free Energy (-delta G means the reaction will proceed in forward direction)
The concentration of reactants/products
90
Why is ATP so important?
ATP stores a large amount of energy in its chemical bonds, which can be harnessed by the hydrolysis of ATP.
It can also assist in phosphorylation by donating phosphate groups.
Hence, cleavage of ATP and phosphorylation is usually coupled
91
What are oxidation-reduction reactions?
Reactions where energy is transferred via hydride ions (hydrogen ions with two electrons)
92
Define oxidation and reduction
Oxidation is the loss of electrons (loss of charge)
| Reduction is the gain of electrons (gain of charge)
93
Briefly describe the function of NAD and FAD
NAD and FAD can both accept electrons (can become reduced)
94
What is the function of oxidoreductases?
Catalyse redox reactions
95
What is the function of transferases?
Transfers a specific functional group from a donor molecule to an acceptor molecule
96
What is the function of hydrolases?
Catalyse hydrolysis reactions by the addition of H2O in the form of H+ and OH-
97
What is the function of lyases?
Cleaves bonds by means other than hydrolysis and oxidation
98
What is the function of isomerases?
Facilitate intramolecular rearrangements and conformational changes to create isomers
99
What is the function of ligases?
Synthesise bonds in reactions coupled to ATP cleavage or another nucleotide
