Quiz 1 true or false Flashcards
Regarding the different body compartments: An increase in plasma urea concentration will cause haemolysis of erythrocytes in vivo.
FALSE
-Although there will be an increase in osmolarity, urea is not an effective osmole and so it will not induce osmotic flux of water out of the erythrocytes. Instead urea will equilibrate across the cell membrane. In renal failure when uraemia occurs this does not cause haemolysis.
AZT is a nucleotide analogue.
FALSE
-This drug, which inhibits replication of HIV, is a nucleoside analogue. It is taken up into cells, and phosphorylated (i.e. converted into a nucleotide). It is then incorporated into and inhibits further polymerisation of the DNA of the replicating virus.
The DNA double helix consists of two polydeoxyribonucleotides arranged in a parallel fashion.
FALSE
-‘Polydeoxyribonucleotide’ simply means a DNA polymer, so that part of the statement is OK. However the two polymers are said to be ‘antiparallel’, not parallel. At one end of a linear double helix is the 5’ end of one of the polymers, and the 3’ end of the other. At the other end of the double helix, the same applies, of course. A parallel arrangement would be one in which the 5’ ends of both polymers were at the same end of the double helix (and both 3’ ends at the other end).
Glucose and fats are energy providers in our food by virtue of their highly reduced nature.
TRUE
-These food molecules have high potential energy because they contain large numbers of hydrogen atoms with ‘high energy’ electrons. These would ‘prefer’ to associate with an electronegative entity like oxygen. When they are stripped from the food molecules and allowed to associate with oxygen we breathe in, much of what was the potential energy of the food molecule is released, and some is saved in forming ATP from ADP.
Biosynthetic reactions are referred to as amphibolic processes.
FALSE
-They are called anabolic processes. ‘Amphibolic’ means both anabolic and catabolic. Later in the course you will meet a process (the citric acid cycle) that is sometimes regarded as being amphibolic.
If pH = 8, then [OH-] = 10-6 mol/L.
TRUE
-If pH = 8, then pOH = (14 - 8) = 6.
So -log10[OH-] = 6 and log10[OH-] = -6.
So [OH-] = antilog10 (-6) = 10-6 mol/L .
Penicillins kill bacteria rather than host cells because in the latter the antibiotic is rapidly degraded in lysosomes.
FALSE
-Penicillins are selective in their activity because they interfere with the synthesis of the cell wall of the bacterium, a structure not present in animal cells.
-1 is the logarithm to the base 10 of 0.1.
TRUE
-The logarithm of a number is the power to which the ‘base’ must be ‘raised’ to give the number. 10 must be raised to the power -1 to give 0.1 (or 10-1), so the logarithm to the base 10 of 0.1 is, indeed, -1.
If normal adult blood has a pH of 7.4 and the pKa of the first dissociation of carbonic acid is 6.1, then the molar concentration of bicarbonate in blood exceeds that of the undissociated acid.
TRUE
-Applying the Henderson-Hasselbalch equation (pH = pKa + log10 [A-]/[HA]), 7.4 = 6.1 + log10 [bicarbonate]/[carbonic acid]. So log10 [bicarbonate]/[carbonic acid] = (7.4 – 6.1) = 1.3 and [bicarbonate]/[carbonic acid] = antilog10 (1.3) = about 20. Therefore, the molar concentration of bicarbonate far exceeds that of undissociated carbonic acid.
In both substrate-level phosphorylation and oxidative phosphorylation, the entity being ‘phosphorylated’ is ADP.
TRUE
-Both processes involve ATP formation from ADP.
Forming ATP from ADP is, in isolation, exergonic.
ATP has a more complex structure, and a higher potential energy than ADP. Forming it from ADP is, in isolation, endergonic, the energy for the process being supplied in our bodies by the (indirect) release of the potential energy of food molecules.
If pOH = 7 then [H+] = 107 mol/L
FALSE
-If pOH = 7, then pH = (14 - 7) = 7.
So -log10 [H+] = 7 and log10 [H+] = -7.
So [H+] = antilog10(-7) = 10-7 mol/L (not 107 mol/L).
The three atoms involved in a hydrogen bond lie in a straight line.
TRUE
-The hydrogen atom and the two electronegative atoms on either side of it interact most stably when they lie in a straight line. This contributes, for example, to the specific complementarity seen in the base-pairing of the DNA double helix.
Mitochondria contain DNA, RNA and ribosomes.
TRUE
-Mitochondrial DNA encodes some of the proteins that make up the mitochondrion. It is replicated and transcribed within the mitochondrion, and a few proteins are made inside the organelle on ribosomes that resemble in structure the ribosomes of prokaryotic cells. This semi-autonomous nature of mitochondria ‘fits’, of course, the idea that they are the remnants of prokaryotes ‘captured’ by eukaryotic cells.
A reaction in which energy is released is said to be exothermic
FALSE
-Sometimes the terms exothermic and exergonic are used interchangeably (as are the terms endothermic and endergonic). However, strictly speaking, ‘exothermic’ really means ‘releases heat’ - in other words, one particular type of energy. The term tends to be used by chemists, because spontaneous chemical reactions in test-tubes do generally release heat energy. The term ‘exergonic’ is less specific: it simply means ‘releases energy’. The term tends to be used by biochemists, because they study processes in which spontaneous reactions may release energy in forms other than heat. For example, some exergonic processes pass energy to, and enable, endergonic processes in the cell. So, in summary, an exothermic process is (just) one type of exergonic process
