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Molecular Building Blocks Flashcards

1
Q

Monosaccharides

A

One hydroxyl group
Generally exist as ring structure (cyclised)
Aldose has an aldehyde
Ketose has a ketone

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2
Q

Glycosidic bond

A

Hydroxyl group of a monosaccharide can react with an OH or NH to form a glycosidic bond

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3
Q

O-glycosidic bonds form…

A

Disaccharides, oligosaccharides and polysaccharides

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4
Q

N-glycosidic bonds found in…

A

Nucleotides in DNA

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5
Q

Disaccharides

A

Contain 2 monosaccharides joined by an o-glycosidic bond

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6
Q

Oligosaccharides

A

Contain 3-12 monosaccharides
Product of digestion of polysaccharides or part of a complex protein/lipid

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7
Q

Polysaccharides

A

Formed by thousands of monosaccharides joined by glycosidic bonds

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8
Q

Glycogen

A

Branched polysaccharides formed by glucose residues

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9
Q

Nucleotides

A

Made from nitrogenous base, sugar and phosphate
Bonds between bases hydrogen bonds
Bonds between nucleotides = phosphodiester bonds

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10
Q

Triglycerides

A

3 fatty acids bound to glycerol
Straight carbon chains with a methyl group and a carboxyl group at ends
Tends to be hydrophobic
Contain no oxygen in main chain

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11
Q

Unsaturated fatty acids

A

Double bonds are commonly cis, spaced at 3C intervals

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12
Q

Proteins

A

Amino acids linked by peptide bonds
Protein - if it is functional and synthesised by a cell
Peptide - bit of protein broken off

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13
Q

Folding of proteins

A

Linear chains fold in different shapes to form 3D structures
Determined by charged interactions, flexibility, amino acid sequence and physical dimensions

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14
Q

Primary structure

A

Linear sequence of amino acids

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15
Q

Secondary structure

A

Alpha helix or beta pleated sheets formation due to H+ bonds between amino acids-
Determine by local interactions between side chains and sequence of amino acids

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16
Q

Tertiary structure

A

Overall 3D conformation of a protein
Can change with temperature or pH

bonds between R -groups:
Disulfide bonds - strong covalent bonds that form between 2 cysteine R groups. Strongest within a protein so most resistant to temperature+pH changes but can be broken by oxidation
Ionic bonds - form between any carbonyl and amino R group weaker so broken by pH changes
Hydrogen bonds- form between strongly polar R groups
Hydrophobic interactions- form between hydrophobic non-polar R groups within interior of protein
It creates specific and flexible binding sites for ligands
Some conformational domains occur repeatedly and include barrels, bundles and saddle

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17
Q

Alpha helix

A

hydrogen bonds between each carbonyl oxygen atom and the amino hydrogen of an amino acid residue located 4 residues farther down the chain. Core of helix is tightly packed. Proline breaks the helix (ring and no H). Side chains look outwards

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18
Q

Beta pleated sheet

A

hydrogen binding between regions of separate neighbouring polypeptide strands aligned parallel to each other. Bonds are at an angle in the parallel beta-sheets (parallel if the polypeptide strands run in the same direction (as defined by their amino and carboxyl terminals)) are weaker than in the anti parallel beta-sheet (Antiparallel strands are often the same polypeptide chain folded back on itself, with simple hairpin turns or long runs of polypeptide chain connecting the strands)

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19
Q

Quaternary structure

A

proteins that contain more than one polypeptide chain joined by same bonds as in tertiary structure
Many proteins function in the cell as dimers, tetramers, or oligomers, proteins in which two, four, or more subunits, respectively, have combined to make one functional protein.

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20
Q

Proteoglycans

A

long unbranched polysaccharide radiating from a core protein, form (along with proteins such as collagen) the extracellular matrix cells exist on

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21
Q

Monosaccharide isomers

A

Asymmetric so have a chiral carbon- enantiomers. Monosaccharide stereoisomers are designated D or L based on position of hydroxyl group farthest from the carbonyl carbon that matches D or L glyceraldehyde

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22
Q

Sugar derivatives

A

Animosugars: contain an amino group instead of a hydroxyl group on one of the carbons (usually carbon 2)- often acetylated to form an N-acetylated sugar eg. Glucosamine
Alcohol sugars eg sorbitol
Sulfate groups eg Heparin, chondroitin sulphate
Phosphorylated at terminal carbons, which prevents transport out of cells eg Glucose-6-phosphate

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23
Q

Water

A

universal solvent (can dissolve ionic and polar substances)
• polarity leading to hydrogen bonding
• liquid range from O to 100 °C
• max density at 4°C
• Doesn’t interact with non-polar substances, lipids, aromatic groups - hydrophobic compounds
Hydrogen bonding = electronegative atoms such as O or N can attract hydrogen atoms from other molecules. Partial sharing of this proton leads to a mutual attraction between the 2 atoms. Weak on its own but strong in a collective

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24
Q

steroids

A
  • contain a 4 ring structure called steroid nucleus. Can be synthesised from Acetyl Co-A. Hydrophobic and fat soluble. Cholesterol is the steroid precursor in human cells for steroid hormones and critical role in cell signalling - it is converted to amphipathic water-soluble bile salts such as cholic acid. Bile salts line surfaces of micelles in lumen of intestine where they keep the droplets emulsified in the aqueous environment.
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25
Q

sphingolipids

A

formed from sphingosine (serine and palmitate) instead of glycerol. Sphingomyelin contains a phosphorylcholine group attached to ceramide and is a component of cell membranes and myelin sheath

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26
Q

Eicosanoids

A

synthesised from 20 C atoms. Acids with. 3,4,5 double bonds. biological functions

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27
Q

acylglycerols

A

comprise of glycerol with one or more fatty acids attached through ester linkages. Can be phosphorylated to form phosphoacylglycerols

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28
Q

Lipid aggregates

A

Micelle, Bilayer formed due to hydrophilic and hydrophobic interactions

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29
Q

Organisation

A

atoms → molecules → macromolecules (large molecules formed from simple molecules)

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30
Q

Water

A

universal solvent (can dissolve ionic and polar substances)
• polarity leading to hydrogen bonding
• liquid range from O to 100 °C
• max density at 4°C
• Doesn’t interact with non-polar substances, lipids, aromatic groups - hydrophobic compounds
Hydrogen bonding = electronegative atoms such as O or N can attract hydrogen atoms from other molecules. Partial sharing of this proton leads to a mutual attraction between the 2 atoms. Weak on its own but strong in a collective

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31
Q

Proteoglycans

A

long unbranched polysaccharide radiating from a core protein, form (along with proteins such as collagen) the extracellular matrix cells exist on

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32
Q

Amino sugars

A

contain an amino group instead of a hydroxyl group on one of the carbons (usually carbon 2)- often acetylated to form an N-acetylated sugar eg. Glucosamine

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33
Q

Alcohol sugars

A

Sorbitol

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34
Q

Sulfate groups on sugars

A

Heparin, chondroitin sulphate

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35
Q

Carbohydrate enantiomers

A

Asymmetric so have a chiral carbon- enantiomers. Monosaccharide stereoisomers are designated D or L based on position of hydroxyl group farthest from the carbonyl carbon that matches D or L glyceraldehyde

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36
Q

Lipids

A

straight chain C compounds (mostly 16-20) with a methyl group and a carbonyl group
• Melting point decreases with degree of unsaturation (fluidity) as kink prevents surface contact but increases with chain length
• Double bonds are commonly cis (hydrogen on same side of double bond) and spaced at 3 C intervals- trans fatty acids produced by hydrogenation of polyunsaturated fatty acids in vegetable oils

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37
Q

Nomenclature of lipids

A

18:1, (triangle)9
18 = number of carbon atoms
1 = number of double bonds
Triangle = the position of double bond (between 9th and 10th Carbon)

Also classified by distance of double band closest to w end eg
W-6 20:4 (triangle) 5,8,11,14

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38
Q

Amino acids

A

compounds that contain an amino group and a carboxylic acid group
• 20 naturally occurring
• Most naturally occur in L form
• Charge determined by R group, amino group and carboxylic acid group which changes with pH
• Polarity determined by R group
• At different pH, carboxylic and amino group (and some R groups) are ionised
• peptide bond formed by condensation reaction- cleaved by proteolysis enzymes (proteases or peptidases)
• very stable
• flexibility around C not involved in bond so multiple conformations

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39
Q

Zwitterion

A

React intramolecularly to form a zwitterion = both positively and negatively charged. Because of this, there are strong intermolecular forces of attraction between amino acids so they are soluble crystalline solids

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40
Q

Amino acids

A

Act as protein buffers as can accept or donate H+

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41
Q

Peptide bond

A

very stable
• Cleaved by proteolysis enzymes- proteases or peptidases
• Partial double bond
• Flexibility around C atom not involved in bond, allows multiple confirmations
• Usually one preferred native conformation, determined mainly by side chain and sequence of amino acids

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42
Q

Glycine

A

simplest amino acid R group= -H

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43
Q

Polypeptide starts at…

A

amine group and amino acids added to carboxylate group (N-terminus)

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44
Q

Globular proteins

A

compact, roughly spherical in shape+ soluble in water
Non-polar R groups orientate inwards with polar R groups on outside so are soluble and easily transported and involved in metabolic reactions.
Specific shapes and some are conjugated (prosthetic group) e.g. Enzymes + immunoglobulins

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45
Q

Fibrous proteins

A

long strands of polypeptide chains that have hydrogen bond cross-linkages
Insoluble due to large number of hydrophobic R groups
Repetitive sequence of amino acids eg. Collagen

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46
Q

How is protein structure determine

A

X-ray diffraction of protein crystals

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47
Q

How are protein structures represented

A

• backbone (line of peptide bonds- no side groups)
• cartoon (shows fundamental secondary structures)

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48
Q

Collagen structure

A

structural protein that’s a component of connective tissue in vertebrates (eg tendons, skin, cartilage)
Insoluble fibrous protein formed from 3 polypeptide chains closely held together by hydrogen bonds to form a triple helix- tropocol lagen
Each chain is a helix shape and every 3rd amino acid is glycine and chains are offset allowing then to be arranged closely together
Covalent bonds form cross-linkages between R groups in parallel to form fibrils
Fibrils are positioned so that they are staggered to form fibres that are lined up with forces they are withstanding.

49
Q

Collagen function

A

Many hydrogen bonds within triple helix results in great tensile strength - can withstand large pulling forces
Staggered ends of fibrils provide strength
Insoluble as too long

50
Q

Haemoglobin

A

Globular protein with a quaternary structure
4 polypeptide chains (2 alpha-globins and 2 beta-globins)
Each subunit has a prosthetic haem group- porphyria ring which holds an iron atom
Held together by disulfide bonds and arranged so hydrophobic R groups face inwards (preserving 3D shape) and hydrophilic R groups face outwards (preserving solubility)
Prosthetic haem group = contains Fe2+ ion that can reversible combine with O2
Each haemoglobin molecule has 4 haem groups so can carry 4 oxygen molecules
Role of Hb- transport oxygen around body in red blood cells (erthrocytes)

51
Q

Factors influencing haemoglobin saturation as modify structure and affect its affinity for oxygen:

A

• temperature
• H+
• CO2 concentration

52
Q

Vaso-occlusive crisis

A

occurs when the microcirculation is obstructed by sickled RBCs, causing ischemic injury to the organ supplied and resultant pain. Endothelial damage causes multicellular (platelets, white cells) aggregates which occlude the capillary- cause inflammation

53
Q

S-shaped oxygen-dissociation curve

A
  1. Gradient of curve initially shallow = the shape of Hb means it is difficult for the first O2 molecule to bind to a subunit as they are closely united. So at low ppO2, little oxygen binds to Hb
  2. The binding of O2 changes the tertiary structure of Hb, causing it to change shape and create another binding site. So it takes a smaller increase in ppO2 for the second O2 to bind - positive cooperativity (ensures rapid intake of O2 in lungs)
  3. Gradient reduces and curve plateaus = 4th O2 molecule is hard to bind as less empty sites to bind to as molecule becomes saturated
    Where ppO2 is low (e.g. Respiring tissue) Hb has a low affinity for oxygen which means it unloads O2 rather than loads it - % saturation is low
    Where ppO2 is high (e.g. Lungs) Hb has a high affinity for oxygen so readily loads O2 - % saturation is high
54
Q

Bohr effect

A

Hb has a reduced affinity for O2 in the presence of CO2. The greater the concentration of CO2, the more readily the Hb releases its oxygen - the curve shifts right
At the gas exchange surface - CO2 is constantly being removed and so the pH is slightly raised due to the low pCO2. The higher pH changes the shape of Hb into one that enables it to readily load oxygen. The shape also increases Hb affinity for oxygen so it is not released while being transported in the blood to tissues
At the tissues- CO2 is produced by respiring cells and so the blood pH is lowered. The lower pH changes the shape of Hb so it has a lower affinity for oxygen. Hb releases its oxygen into respiring tissues
High rate of respiration→ more CO2 produced → lower pH→ greater change in Hb shape → more readily unloads oxygen→ more oxygen available for respiration

55
Q

Sickle cell anaemia

A

Autosomal recessive genetic disorder characterised by the formation of hard, sticky, sickle-cell shaped red blood cells in contrast to the biconcave-shaped red blood cells found in ‘normal’ individuals
The gene defect is a single nucleotide polymorphism (GAG to GTG) of the beta-globin gene which results in glutamic acid being substituted by valine at position 6. Haemoglobin S with this mutation is referred to as HbS. This is normally. Benign mutation, causing no apparent effects on the structure of haemoglobin in normal oxygen concentrations. But at low ppO2 eg hypoxia, HbS polymerises and forms fibrous precipitates because the deoxy form of haemoglobin exposes a hydrophobic patch on the protein between the E and F helices. The amino acid change causes polymerization of this mutant hemoglobin (hemoglobin S [HbS]) to form fibers upon deoxygenation in the tissues, the root cause of the pathology of the disease. The fibers make the red blood cells less flexible and distort the shape of the cells, a process typically referred to as sickling.

56
Q

Treatment of sickle cell anaemia

A

• hydroxyurea- stimulates bone marrow to make foetal haemoglobin
• Embolising drugs
• Plasma exchange to reduce number of sickle cells

57
Q

Sickle cell anaemia pain

A

Early presentations can be pain in the hands and feet with severe pain in bones such as femur, humerus, ribs and pelvis occurring in older children. These are due to vaso-occlusive events in the small vessels. Repeated events in the bones can lead to chronic infarcts.

58
Q

Enzymes as disease markers

A

Liver function: acid phosphatase/ alanine aminotransferase
Prostate cancer: alkaline phosphorylase
Pancreas function: amylase
Renal function: angiotensin converting enzyme
Liver function: aspartame aminotransferase
Myocardial infatuation: creatinine kinase

59
Q

Protein denaturation

A

the loss of tertiary (and/or secondary) structure within a protein, which can be caused by heat, acid, or other agents that interfere with hydrogen bonding and usually causes a decrease in solubility (precipitation).

60
Q

Enzymes

A

Biological catalysts = speed up rate of reaction by providing an alternative reaction pathway with a lower activation energy without being used up or changed
Globular proteins with a specific active site where specific substrates bind, forming an E/S complex
• intracellular enzymes= produced and function inside cell
• extra cellular enzymes = secreted by cells + catalyse reactions outside cells e.g. Bacteria release proteases to digest protein so can absorb amino acids for growth

61
Q

catabolic reactions (breakdown)

A

fitting into active site puts stresses + strains on bonds in substrate so bonds more likely to break

62
Q

anabolic reactions (forming)

A

being attached to the enzyme holds then closer together, reducing any repulsion so they can bond more easily

63
Q

Lock + key model- 1890s by Emil Fischer

A

Both enzymes and substrates are rigid structures that lock into each other exactly. Comments on specificity but not how activation energy is lowered

64
Q

Induced fit hypothesis

A

the enzyme’s active site can change shape slightly as the specific substrate molecule enters the enzyme (conformational changes) so they are complementary. The substrate molecule temporarily bonds with amino acids in the active site and, as it changes shape, it places stresses and strains on bonds in the substrate making it more likely to react. The temporary E/S bonds then break + products expelled as enzyme returns to its original shape
If active site altered by temperature, pH or mutation in base sequence, E/S complexes can not form

65
Q

How are enzymes regulated

A

Can be regulated by altering concentration of substrates, products, inhibitors or activators as well as phosphorylation of the enzyme

66
Q

Isoenzymes

A

enzymes that have a different structure and sequence but catalyse the same reaction

67
Q

Coenzymes

A

cannot in themselves catalyse a reaction but can help enzymes to do so- bind with enzyme protein molecules to form active enzymes

68
Q

Antigen recognition

A

• very close proximity of the antibody CDR regions and the antigen surface
• Intimate contact allows the combination of relatively weak interactions to produce a strong binding surface
• CDR loops have a sequence of amino acids that complement the surface of the antigen

Hydrogen bonds, charge, bulk (CDR can form a pocket to interact with and bury the bulky group), CDRs can form a compatible hydrophobic surface which affect recognition

69
Q

Epitope

A

portion of antigen bound

70
Q

Antibodies

A

Proteins (immunoglobulins) with specific binding sites complementary to a specific antigen synthesised by B cells (plasma cells)
Composed of 4 polypeptide chains: 2 long heavy chains and 2 short light chains- joined by disulphide bonds
Each antibody has a specific binding site that fits precisely onto a specific antigen to form an antigen-antibody complex- Van der Waals forces hold together (instantaneous dipole)

71
Q

Variable region

A

primary sequence forms a specific tertiary structure, resulting in a specific binding site

72
Q

Hinge region

A

gives flexibility which allows the antigen-binding site to be placed at different angles when binding to antigens, so allows it to bind to 2 antigens at once

73
Q

How do antibodies lead to the destruction of antigens

A

• agglutination of cells - clumping then together, making it easier for phagocytes to locate and engulf them
• opsonisation - serve as markers that stimulate phagocytosis
• can act as anti-toxins, neutralising them
• can attach to flagella of bacteria, making them less active so phagocytosis easier
• can combine with viruses and toxins to block them from entering or damaging cells
• complement activation - can create holes in cell wall, causing them to burst (lysis) when water moves in by osmosis - work inconjunction with other proteins

74
Q

How do antibodies lead to the destruction of antigens

A

• agglutination of cells - clumping then together, making it easier for phagocytes to locate and engulf them
• opsonisation - serve as markers that stimulate phagocytosis
• can act as anti-toxins, neutralising them
• can attach to flagella of bacteria, making them less active so phagocytosis easier
• can combine with viruses and toxins to block them from entering or damaging cells
• complement activation - can create holes in cell wall, causing them to burst (lysis) when water moves in by osmosis - work inconjunction with other proteins

75
Q

Clinical uses of antibodies

A

pregnancy testing, cancer treatment, diagnosing diseases

76
Q

Professional antigen-presenting cells

A

B cells, dendritic cells, macrophages

77
Q

What is the final stage of collagen assembly

A

Cross-linking of collagen fibres through the formation of strong collagen cross-links between lysine residues

78
Q

What component of haemoglobin is affected by sideroblastic anaemia

A

Haem

79
Q

Transcription

A

RNA polymerase binds to the promoter sequence and unwinds part of a DNA molecule by breaking the hydrogen bonds between complementary base pairs, exposing the gene to be transcribed. Free activated RNA nucleotides pair up via hydrogen bonds with their complementary bases on the template antisense strand of the ‘unzipped’ DNA molecule. RNA polymerase then joins the RNA nucleotides together by condensation reactions, forming phosphodiester bonds in the 5’ to 3’ direction. Terminators signal RNA transcription is complete so the hydrogen bonds break between the DNA and mRNA molecules and the double-stranded DNA reforms. The pre-mRNA is then spliced - introns are removed and exons are joined together, resulting in mature mRNA which exits nucleus via a pore

80
Q

mRNA splicing

A

during and after transcription, introns in the precursor (pre) mRNA are excised, and the noncontiguous coding exons are spliced together to form a shorter mature mRNA before its transportation to the ribosomes. The boundary between the exons and introns consist of a 5’ donor GT dinucleotide and 3’ acceptor AG dinucleotide. These, along with surrounding short splicing consensus sequences, another intronic sequence (branch site), small nuclear RNA (snRNA) molecules and associated proteins are necessary for splicing

81
Q

5’ capping

A

the 5’ cap is thought to facilitate transport of the mRNA to the cytoplasm and attachment to the ribosomes, as well as protect the RNA transcript from degradation by endogenous cellular exonucleases. After 20-30 nucleotides have been transcribed, the nascent mRNA is modified by the addition of a guanine nucleotide to the 5’ end of the molecule by an usual 5’ to 5’ triphosphate linkage. A methyltransferase enzyme then methylates the N7 position of the guanine, giving the final 5’ cap

82
Q

Polyadenylation

A

transcription continues until specific nucleotide sequences are transcribed that cause the mRNA to be cleaved and RNA polymerase II to be released from the DNA template. Approx. 200 adenylate residues are added to the mRNA (poly(A) tail), which facilitates nuclear export and translation

83
Q

Where does transcription occur

A

Nucleus

84
Q

Control of transcription

A

The regulatory elements in the promoter region are cis-acting- they only affect the expression of the adjacent gene on the same DNA duplex, whereas the transcription factors are trans-acting, acting on both copies of a gene on each chromosome being synthesized from genes that are located at a distance.

85
Q

Transcription factors

A

proteins which bind to DNA (the promoter sequence) and increase/decrease the transcription of genes
Enter nucleus from cytoplasm and are activated through a signalling pathway

86
Q

Mechanism of transcription factors

A
  1. The transcription factor binds to the promoter sequence of DNA (a section of DNA upstream of the coding region) near to the gene to be activated
  2. RNA polymerase binds to the DNA-transcription factor complex and is activated, which causes it to move away from the complex along the gene
  3. RNA polymerase transcribes the strand of DNA until it reaches a terminator sequence- gene is expressed
    If not expressed, the transcription factor inhibits RNA polymerase from binding

A transcription complex forms around the TATA box 5’ of first exon
Helix opens, DNA strand separation
RNA Pol II builds mRNA

87
Q

Factors turning off expression

A

• activation of depressors (inhibitors of RNA polymerase binding)
• Each step of RNA transcription or processing finds no longer actively produced transcription an processing proteins
• Complexes do not form anymore for lack of phosphorylation
• Enzymes no longer activities
• RNA stability

88
Q

Translation

A

After leaving the nucleus, the mRNA molecule attaches to a ribosome. A tRNA molecule (carrying a specific amino acid), with an anticodon complementary to the first mRNA codon, attaches itself to the mRNA by complementary base pairing. First amino acid is always methionine, codon = AUG on mRNA. Second tRNA molecule attaches itself to the next mRNA codon in the same way. The two specific amino acids attached to the tRNA molecules are joined by a condensation reaction forming a peptide bond using ATP. The first tRNA molecule moves away, leaving its amino acid behind. The ribosome moves along the mRNA in the 5’ to 3’ direction. A third tRNA molecule binds to the next mRNA codon, bringing a specific amino acid, which binds to the first two amino acids and the second tRNA moves away. This continues producing a polypeptide chain until there is a ‘stop’ codon (UAG, UAA, UGA) on the mRNA molecule. The polypeptide chain moves away from the ribosome

89
Q

tRNA

A

incorporation of amino acids into a polypeptide chain requires amino acids to be covalently bound by reacting with ATP to the specific tRNA molecule by the activity of the enzyme aminoacyl tRNA synthetase.
• the ribosome, with its associated rRNAs, moves along the mRNA, the amino acids linking up by the formation of peptide bonds through the action of the enzyme peptidyl transferase to form a polypeptide chain

90
Q

Where does translation occur

A

Cytoplasm

91
Q

Polymerase chain reaction (PCR)

A

in vitro method of amplifying DNA
1. Add to the thermocycler: piece of DNA to be copied, primers (a short section of single-stranded DNA that is complementary to the DNA interested in. 2 different primers are needed as the sequences at the ends of the target DNA are different. They keep the 2 DNA strands separate and create a double-stranded section for Taq DNA polymerase to bind to), nucleotides, Taq DNA polymerase (thermostable as from bacteria found in a hot spring - thermophilic) and buffer solution
2. Denaturation - heat up to 95°C to break hydrogen bonds between 2 DNA strands
3. Annealing - cool to 55°C to anneal the primers
4. Extension - heat to 72°C and Taq DNA polymerase will attach to the DNA strand and synthesise complementary DNA to produce new identical double-stranded DNA molecules (stops when all DNA nucleotides used up)

92
Q

Sequence of temperatures in PCR

A

95 —> 55 —> 72

93
Q

Northern blotting

A

technique to look at gene expression by detection of RNA

94
Q

What is initially added to the thermocycler in PCR

A

piece of DNA to be copied, primers (a short section of single-stranded DNA that is complementary to the DNA interested in. 2 different primers are needed as the sequences at the ends of the target DNA are different. They keep the 2 DNA strands separate and create a double-stranded section for Taq DNA polymerase to bind to), nucleotides, Taq DNA polymerase (thermostable as from bacteria found in a hot spring - thermophilic) and buffer solution

95
Q

Viral replication: retrovirus

A
  1. A virus uses attachment proteins on its surface to bind to complementary receptors on the surface of a host cell
  2. The virus injects its DNA/RNA into the host and it is replicated by the cell
  3. The host cell uses its nucleic acids and ribosomes to produce new viral proteins (i.e. capsid)
  4. The new viral particles are released either when the host cell bursts or viral particles leave individually through the host cell membrane via budding - forming the lipid envelope

Attachment →penetration →reverse transcriptase →integration →translation →assembly →budding →release

96
Q

Replication of HIV

A
  1. Following infection, HIV enters the bloodstream and circulates around the body. A protein on HIV readily binds to a CD4 receptor on a helper T cell
  2. The capsid fuses with the cell surface membrane and so the RNA and enzymes of HIV enter the helper T cell
  3. The reverse transcriptase converts the viral RNA into DNA which is inserted into the cell’s DNA by DNA intergrase
  4. The HIV DNA in the nucleus creates mRNA which exists through a nuclear pore and synthesises new HIV particles at a ribosome
  5. HIV particles ‘bud’ from the helper T cell eventually killing it
97
Q

Recombinant DNA technology

A

• vaccines
• production of therapeutic proteins eg insulin and growth hormone - Recombinant DNA corresponding to the A-chain of human insulin was prepared and inserted into plasmids that were used to transform Escherichia coli cells. The bacteria then synthesized the insulin chain, which was purified. A similar process was used to obtain B-chains. The A- and B-chains were then mixed and allowed to fold and form disulfide bonds, producing active insulin molecules.
• Production of complex human proteins eg Factor VIII
• production of siRNA to reduce expression of a particular gene
• production of monoclonal antibodies used in targeted drug treatment, diagnosis
• Gene therapy:
Ex vivo- adult stem cells removed, virus vector altered to contain desired gene, patent’s cells altered after exposure to virus then grown in the lab, transgenic cells injected into patient
In vivo- liposome or adenovirus inject DNA into cell’s DNA
e.g. Severe combined immunodeficiency (SCID)- created by ex vivo somatic gene therapy as a virus transfers a normal allele for ADA into T-lymphocytes
• Screening patients: Genetic screening can help identify individuals who are carrying an allele at a gene locus for a particular disorder e.g. CF or breast cancer
• DNA fingerprinting
• Transgenic animals
• Proteomics is the study of proteins expressed by a cell. Differences in protein expression between normal and cancer cells can be used to identify potential targets for future therapy. CNS

98
Q

Ex vivo gene therapy

A

adult stem cells removed, virus vector altered to contain desired gene, patent’s cells altered after exposure to virus then grown in the lab, transgenic cells injected into patient

99
Q

In vivo gene therapy

A

liposome or adenovirus inject DNA into cell’s DNA
e.g. Severe combined immunodeficiency (SCID)- created by ex vivo somatic gene therapy as a virus transfers a normal allele for ADA into T-lymphocytes

100
Q

Production of therapeutic proteins

A

eg insulin and growth hormone - Recombinant DNA corresponding to the A-chain of human insulin was prepared and inserted into plasmids that were used to transform Escherichia coli cells. The bacteria then synthesized the insulin chain, which was purified. A similar process was used to obtain B-chains. The A- and B-chains were then mixed and allowed to fold and form disulfide bonds, producing active insulin molecules.

101
Q

Proteomics

A

study of proteins expressed by a cell. Differences in protein expression between normal and cancer cells can be used to identify potential targets for future therapy. CNS

102
Q

Diagnostic uses of monoclonal antibodies

A

study of proteins expressed by a cell. Differences in protein expression between normal and cancer cells can be used to identify potential targets for future therapy. CNS

103
Q

Therapeutic uses of monoclonal antibodies

A

prevention of blood clots, autoimmune therapies, targeting drugs…
1. Monoclonal antibodies are produced that are specific to antigens on cancer cells
2. Antibodies are given to a patient and bind to receptors on cancer cells, blocking the chemical signals which stimulate uncontrolled growth e.g. Herceptin
3. OR involves attaching a radioactive or cytotoxic drug so when the antibody attaches to the cancer cell, it kills them

104
Q

IgM antibodies

A

Circulating tetramers made at the beginning of infection.

105
Q

IgG antibodies

A

Monomer highly specific antibodies targeting single epitopes.

106
Q

IgE antibodies

A

Likely to have developed in response to parasitic threats. Implicated in allergy, particularly alongside eosinophils

107
Q

IgA antibodies

A

Expressed in mucosal tissue. Forms dimers. Protects the neonatal gut (expressed in breast milk)

108
Q

IgD antibodies

A

Monomers, induction of antibodies in B cells, activates basophils and mast cells

109
Q

Sickle cell anaemia

A

Sickle cell haemoglobin is caused by a mutation that replaces glutamic acid at residue 6 in beta-globin with valine leading to the formation of linear polymers of deoxygenated HbS. The valine residue on the surface binds to the free complementary O2 site, linking the 2 tetramers together. As more tetramers become linked, linear polymers form converting normally flexible red blood cells into stiff, sickle-shaped cells which plug the capillary beds.
The change in a single nucleotide (GAG to GTG) in the gene that codes for the beta-globin molecule on chromosome 17, results in a change in the primary structure of the polypeptide (glutamic acid is substituted by valine). Glutamic acid has a hydrophilic negatively charged side chain whereas valine has a hydrophobic side chain. As a result in low ppO2, as the amino acid is on the surface, the beta - 6 valine becomes buried in a hydrophobic pocket on an adjacent beta-globin chain, joining the molecules together to form insoluble polymers.

110
Q

Where is the mutation for sickle cell anaemia

A

Chromosome 17

111
Q

What is the single nucleotide substitution for sickle cell anaemia haemoglobin S

A

GAG to GTG

112
Q

What is the amino acid substitution for sickle cell anaemia haemoglobin S

A

glutamic acid is substituted by valine

113
Q

How is sickle cell anaemia inherited

A

Sickle cell anemia is a autosomal recessive condition meaning that you must inherit a mutated haemoglobin gene (haemoglobin S) from both the maternal and paternal DNA. It can also occur by compound heterogeneity when a child inherits one haemoglobin S gene and another faulty haemoglobin gene (eg beta thalasdemia, haemoglobin C/D/E). If both parents are carriers, the child has a 25% chance of homozygosity.

114
Q

Sickle cell trait

A

produces both types of haemoglobin so conditions worse in cold, wet environments due to vasoconstriction

115
Q

Treatment of sickle cell anaemia

A

• hydroxyurea- stimulates bone marrow to make foetal haemoglobin
• Embolising drugs
• Plasma exchange to reduce number of sickle cells

116
Q

Symptoms of sickle cell anaemia

A

• anemia as sickle cells break apart easily and die
• episodes of pain which develops when sickle-shaped red blood cells block blood flow through capillaries in chest, abdomen or joints
• swelling of hands and feet caused by sickle-shaped blood cells blocking circulation in the hands and feet
• frequent infections as it can damage the spleen, increasing vulnerability to infections- encapsulated bacteria eg pneumonia
• delayed growth or puberty
• vision problems due to a damaged retina from reduced blood supply as a result of blocked blood vessels
• Pulmonary hypertension due to reduced oxygen carrying capacity of blood
• Avascular necrosis eg in head of femur

117
Q

Which cells produce elastin?

A

Fibroblasts

118
Q
  1. Which 2 proteins are involved in the generation of ciliary movement?
A

Tubulin
Dynein

119
Q
  1. What happens to abnormal HbS in hypoxia or deoxygenated states?
A

HbS polymerises and crystallises

IMMS (6 decks)

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