Molecules and Cells Flashcards
what is the dissociation constant of an acid
where the acid dissociates to hydrogen ions and a base, the rate at which they dissociate to produce protons
how can the Ka be calculated
ka = conc of H x conc of OH divided by acid conc
what acids have a higher Ka
strong acids have a higher Ka as the dissociate quicker in solution
when is buffering most effective
when equilibrium is reached, so half dissociation, when pH = pKa, due to concentration of base and acid = so in equation, only pKa left
how does histidine have 3 buffering capacities
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
what is the goal of buffers
to restrict changes in pH
what acids are important in oral health
lactic acid, formic acid, acetic acid
how are acids formed in oral cavity
plaque bacteria ferments carbohydrates which releases acids
how does the production of acids result in tooth decay
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
what is the difference between tooth decay and erosion
erosion involves acids directly from food and drink, decay involves fermentation of carbohydrates
what are chelating agents
in certain fruit juices, mop up free calcium ions, therefore causing a shift of the equilibrium to the right to restore this concentration
what do buffers normally consist of
weak acid or weak base and one of its salts
why is bicarbonate the main buffer in saliva
pka value of around 6.7, so max buffering capacity around 7 perfect for oral cavity
what are the common secondary structures of proteins
alpha helix or beta pleated sheet
what is collagens unique structure
triple helix, 3 alpha helices wrapped around one another, rope like structure giving it strength and water insoluble
how is the tertiary structure of proteins formed and what protein is this found in
binding between R side chains, often giving globular appearance, myoglobin
describe the structure of haemoglobin
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
what is maltose composed of
2 glucose molecules joined by an alpha 1-4 glycosidic bond
how does the structure of starch and glycogen differ
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
what is the structure of a di-glyceride and where can this be found
2 glycerol molecules are bounded to fatty chains, but the other is bonded to a phosphate molecule - found in cell membrane
name 3 biological roles of proteins
enzymes, receptors, movement
what is the structure of an amino acid
one central carbon, one amine group, one carboxyl group, one R side chain and one H ion
how can amino acids act as buffers
can ionise to either release H ions from COOH group or accept at NH3 group
how is a protein formed
through condensation reaction between amino acids, NH2 and COOH groups bind together to lose water
define homeostasis
the act of maintaining ideal conditions in the body to allow functions
what 2 mechanisms mainly control homeostasis
negative feedback and feed forward control
define negative feedback
increasing the concentration is detected by receptors, this then feeds to a central control which responds by decreasing stimulation or activating inhibition
what is feed-forward control
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
give an example of electrical communication between cells
through gap junctions, spreading electrical transmission - intercalated discs in the cardiac muscle
what are the 3 types of chemical communication between cells
one to one - synapse
one to many cells - exocrine
many to many - endocrine
compare nerves to hormones
nerves are fast acting but effect is short lived, hormones are slower to act but last longer
how do steriods exert their effects
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
how to peptide hormones exert their effects
lipophobic so cannot travel through membrane, binds to receptors on cell surface, activates G protein which activates second receptor to produce proteins
how does cAMP act as a second messenger
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
what are the 2 ways in which enzymes work
lock and key, induced fit model
what is denaturating an enzyme and how does it occur
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
what is the activation energy of a reaction and how do enzymes alter this
the energy required for the reaction to occur, enzymes lower this energy to increase rate of reaction
what is free energy
the difference between the initial energy in the reactants and the final energy in the products
what is the Km of an enzyme
its affinity for the substrate, this is inverse, a high Km is a low affinity
how does the Km alter the rate of reaction
a low Km will mean that low concentrations of substrate are required for a high rate of reaction
what is the difference between nucelotide and nucleoside
both have sugar and a base but nucleotide also has a phosphate molecule
what are the two types of bases and how do they differ
purine and pyrimidine, purine has 9 nitrogen molecules, pyrimidine only has 6
what bases have a purine ring structure
adenine and guanine
what bases have a pyrimidine ring structure
cytosine, thymine and uracil
what sugars may be present in a nucleotide
ribose sugar or deoxyribose sugar
give an example of a nucleotide
ATP - adenosine triphosphate
what is the structure of DNA
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
name 3 differences between RNA and DNA
ribose sugar instead of deoxyribose sugar, single stranded instead of double, uracil instead of thymine
what are the different types of RNA
ribosomal, translational and messenger
what are the stages in protein production
transcription and translation
what occurs at the transcription phase of protein production
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
what occurs at the translation phase of protein production
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
what can be the result of DNA mutation
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
how is a specific gene isolated in gene cloning
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
how can a specific gene be inserted into a plasmid in gene cloning
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
why is a plasmid with a gene inserted into a bacterium in gene cloning
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
how can it be checked if the plasmid took up the gene in gene cloning
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
how can it be checked if the bacterium accepted the plasmid
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
what is the sanger technique useful for
DNA sequencing
what is required for the sanger technique
strand of DNA, primer, deoxynucleotides, di-deoxynucleotides
how do di-deoxynucleotides differ from deoxynucleotides
contains H on carbon 3 instead of OH, preventing it from bonding to phosphate on another nucleotide, prevents elongation of the chain
describe how the sanger technique works for DNA sequencing
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
what do modern techniques use for DNA sequencing
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
