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bds 1 bams > Molecules and Cells > Flashcards

Molecules and Cells Flashcards

1
Q

what is the dissociation constant of an acid

A

where the acid dissociates to hydrogen ions and a base, the rate at which they dissociate to produce protons

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2
Q

how can the Ka be calculated

A

ka = conc of H x conc of OH divided by acid conc

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3
Q

what acids have a higher Ka

A

strong acids have a higher Ka as the dissociate quicker in solution

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4
Q

when is buffering most effective

A

when equilibrium is reached, so half dissociation, when pH = pKa, due to concentration of base and acid = so in equation, only pKa left

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5
Q

how does histidine have 3 buffering capacities

A

3 equilibria are involved due to the structure, at low pH NH3 can mop up H ions to increase pH, then as pH increases, has 2 groups that can donate H ions to slow the increase down - at pH 6 and 9

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6
Q

what is the goal of buffers

A

to restrict changes in pH

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7
Q

what acids are important in oral health

A

lactic acid, formic acid, acetic acid

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8
Q

how are acids formed in oral cavity

A

plaque bacteria ferments carbohydrates which releases acids

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9
Q

how does the production of acids result in tooth decay

A

acids increase concentration of H ions, this pushes the equilbrium to the right, causing solubilisation of hydroxyapatite - enamel crystals, releases free calcium and phosphate ions

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10
Q

what is the difference between tooth decay and erosion

A

erosion involves acids directly from food and drink, decay involves fermentation of carbohydrates

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11
Q

what are chelating agents

A

in certain fruit juices, mop up free calcium ions, therefore causing a shift of the equilibrium to the right to restore this concentration

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12
Q

what do buffers normally consist of

A

weak acid or weak base and one of its salts

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13
Q

why is bicarbonate the main buffer in saliva

A

pka value of around 6.7, so max buffering capacity around 7 perfect for oral cavity

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14
Q

what are the common secondary structures of proteins

A

alpha helix or beta pleated sheet

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15
Q

what is collagens unique structure

A

triple helix, 3 alpha helices wrapped around one another, rope like structure giving it strength and water insoluble

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16
Q

how is the tertiary structure of proteins formed and what protein is this found in

A

binding between R side chains, often giving globular appearance, myoglobin

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17
Q

describe the structure of haemoglobin

A

4 chains - 2 alpha chains and 2 beta sheets, alpha interacts with beta, each chain contains and Fe group, has a central open channel in the centre

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18
Q

what is maltose composed of

A

2 glucose molecules joined by an alpha 1-4 glycosidic bond

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19
Q

how does the structure of starch and glycogen differ

A

starch - composed only of 1-4 alpha glycosidic bond, glycogen also has this but is much more branched due to some 1-6 glycosidic bonds, this allows for glucose to be released more quickly

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20
Q

what is the structure of a di-glyceride and where can this be found

A

2 glycerol molecules are bounded to fatty chains, but the other is bonded to a phosphate molecule - found in cell membrane

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21
Q

name 3 biological roles of proteins

A

enzymes, receptors, movement

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22
Q

what is the structure of an amino acid

A

one central carbon, one amine group, one carboxyl group, one R side chain and one H ion

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23
Q

how can amino acids act as buffers

A

can ionise to either release H ions from COOH group or accept at NH3 group

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24
Q

how is a protein formed

A

through condensation reaction between amino acids, NH2 and COOH groups bind together to lose water

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25
Q

define homeostasis

A

the act of maintaining ideal conditions in the body to allow functions

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26
Q

what 2 mechanisms mainly control homeostasis

A

negative feedback and feed forward control

27
Q

define negative feedback

A

increasing the concentration is detected by receptors, this then feeds to a central control which responds by decreasing stimulation or activating inhibition

28
Q

what is feed-forward control

A

when the body realises a change will soon happen so alters the levels in the body in preparation - prior to exercising, parasympathetic removed to heart

29
Q

give an example of electrical communication between cells

A

through gap junctions, spreading electrical transmission - intercalated discs in the cardiac muscle

30
Q

what are the 3 types of chemical communication between cells

A

one to one - synapse
one to many cells - exocrine
many to many - endocrine

31
Q

compare nerves to hormones

A

nerves are fast acting but effect is short lived, hormones are slower to act but last longer

32
Q

how do steriods exert their effects

A

are lipophilic - can travel through the cell membrane, enters cytoplasm to bind to its receptor - this complex enters the nucleus to alter gene transcription and produce proteins - takes longer

33
Q

how to peptide hormones exert their effects

A

lipophobic so cannot travel through membrane, binds to receptors on cell surface, activates G protein which activates second receptor to produce proteins

34
Q

how does cAMP act as a second messenger

A

peptide binds to the receptor, activates g protein through GTP, this then activates adenyl cyclase which converts ATP to cAMP. This can activate protein kinase enzyme

35
Q

what are the 2 ways in which enzymes work

A

lock and key, induced fit model

36
Q

what is denaturating an enzyme and how does it occur

A

altering the structure of the active site so the substrate no long fits and it is does not work, occurs at too high a temperature or a pH

37
Q

what is the activation energy of a reaction and how do enzymes alter this

A

the energy required for the reaction to occur, enzymes lower this energy to increase rate of reaction

38
Q

what is free energy

A

the difference between the initial energy in the reactants and the final energy in the products

39
Q

what is the Km of an enzyme

A

its affinity for the substrate, this is inverse, a high Km is a low affinity

40
Q

how does the Km alter the rate of reaction

A

a low Km will mean that low concentrations of substrate are required for a high rate of reaction

41
Q

what is the difference between nucelotide and nucleoside

A

both have sugar and a base but nucleotide also has a phosphate molecule

42
Q

what are the two types of bases and how do they differ

A

purine and pyrimidine, purine has 9 nitrogen molecules, pyrimidine only has 6

43
Q

what bases have a purine ring structure

A

adenine and guanine

44
Q

what bases have a pyrimidine ring structure

A

cytosine, thymine and uracil

45
Q

what sugars may be present in a nucleotide

A

ribose sugar or deoxyribose sugar

46
Q

give an example of a nucleotide

A

ATP - adenosine triphosphate

47
Q

what is the structure of DNA

A

double stranded helix of nucleotide molecules, each strand has a sugar-phosphate backbone, with phosphodiester bond between phosphate molecule of one nucleotide and C3 on sugar above. Hydrogen bonding between base pairs holds the two strands together

48
Q

name 3 differences between RNA and DNA

A

ribose sugar instead of deoxyribose sugar, single stranded instead of double, uracil instead of thymine

49
Q

what are the different types of RNA

A

ribosomal, translational and messenger

50
Q

what are the stages in protein production

A

transcription and translation

51
Q

what occurs at the transcription phase of protein production

A

RNA nucleotides enter nucleus, unwind the DNA helix then base pairing allows nucleotides to bond to DNA, forms mRNA, this then leaves the nucleus to go to ribosome

52
Q

what occurs at the translation phase of protein production

A

the mRNA at ribosome forms codons - 3 bases long, the tRNA then decodes this to form anti-codons, which match the DNA code, the tRNA then recruits amino acids which are coded for by the anti-codons, the sequence of amino acids produces the protein

53
Q

what can be the result of DNA mutation

A

substitution - one base replaced for another, a different amino acid coded for - either conservative or non-conservative
insertion/deletion - causes a frameshift of the DNA sequence, so every amino acid after this is effected

54
Q

how is a specific gene isolated in gene cloning

A

using restriction enzymes, this cuts the DNA producing segments of different lengths. Gel electrophoresis is used to separate the strands. The size of the specific gene will be known so this can be removed

55
Q

how can a specific gene be inserted into a plasmid in gene cloning

A

the plasmid is cut with the same restriction enzymes as the DNA so the ends of the gene and the plasmid are complementary to one another, H bonds then allow them to anneal with DNA ligase bonding them together

56
Q

why is a plasmid with a gene inserted into a bacterium in gene cloning

A

so the bacterium can replicate and produce many more cells, each cell will contain a copy of the specific gene, allowing it to be amplified

57
Q

how can it be checked if the plasmid took up the gene in gene cloning

A

the plasmid will have a gene for tetracycline resistance, but the restriction enzymes will cut through this gene for insertion of the other gene, rendering the resistance gene unable to work, therefore one an agar plate with tetracycline, there will be no growth of the bacteria

58
Q

how can it be checked if the bacterium accepted the plasmid

A

the plasmid will have a gene for ampicilin resistance, therefore the bacteria should be resistant to this if the plasmid is in the bacterium, allowing for growth on an agar plate

59
Q

what is the sanger technique useful for

A

DNA sequencing

60
Q

what is required for the sanger technique

A

strand of DNA, primer, deoxynucleotides, di-deoxynucleotides

61
Q

how do di-deoxynucleotides differ from deoxynucleotides

A

contains H on carbon 3 instead of OH, preventing it from bonding to phosphate on another nucleotide, prevents elongation of the chain

62
Q

describe how the sanger technique works for DNA sequencing

A

ddNTP’s of each base added to separate tubes, in each tube nucleotides and primer is added. heated to a high temperature to allow the strands to separate, primer then bonds to the start of the strand, nucleotides can bond to the single strand of DNA producing a replica. ddNTPs will bond, preventing elongation, this produces chains of several lengths in each tube. the tubes are run through gel electrophoresis, allowing for the lengths to separate and see the order of the bases

63
Q

what do modern techniques use for DNA sequencing

A

use fluoresence or radioactivity for each base, then every time a base is added, a colour is given, the sequence of colours then relates to the sequence of bases

bds 1 bams (13 decks)

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