Quiz true or false

Question 1

Regarding body fluids: The volume of the extracellular fluid (ECF) is determined by total body sodium.

Answer 1

TRUE
-The activity of the sodium-potassium pump means that sodium is the major non-penetrating solute in the extracellular fluid. Total body sodium therefore controls the osmolarity, and hence the volume, of the extracellular fluid.

Question 2

The chemical process in which the peptide bond is formed is a condensation reaction.

Answer 2

TRUE
-A condensation is a reaction in which the linking of two molecules is accompanied by the formation of a molecule of water. The process is the reversal of a hydrolysis.
The reactions in which the monomers of nucleic acids, polysaccharides and proteins are linked are all, technically, condensations.

Question 3

Biosynthetic reactions are referred to as amphibolic processes

Answer 3

FALSE
- They are called anabolic processes.
‘Amphibolic’ means both anabolic and catabolic.
The citric acid cycle is sometimes regarded as being amphibolic.

Question 4

Catabolic processes are often accompanied by ATP synthesis.

Answer 4

TRUE
-Some of the potential energy ‘released’ when a complex is broken (catabolised) may sometimes be ‘saved’ as the potential energy of ATP formed by phosphorylation of ADP.

Question 5

ATP, NAD, NADP and FAD all contain adenine.

Answer 5

TRUE

-All these molecules contain the base adenine.

Question 6

A decrease in [H+] is accompanied by an increase in pOH.

Answer 6

FALSE
- A decrease in [H+] means an increase in pH ( as pH is defined as -log10[H+] ) As (pOH + pH) always equals 14, when one changes, the other changes inversely. So, if pH increases, pOH must decrease.

Question 7

The rough and smooth forms of endoplasmic reticulum are so-called because the former has and the latter lacks attached ribosomes.

Answer 7

TRUE
- Rough endoplasmic reticulum looks ‘rough’ in the microscope because of the ribosomal particles attached to the otherwise ‘smooth’ membranes.

Question 8

Concerning osmolarity and tonicity:
Osmosis is the process by which water moves from a compartment of low solute concentration to a compartment of high solute concentration

Answer 8

TRUE
-A compartment with low solute concentration will have a high water concentration. Water will therefore tend to move out of this compartment down its concentration gradient.

Question 9

Deoxyribose differs from ribose in not having a hydroxyl group attached to carbon 2 of the sugar.

Answer 9

TRUE
- The sugar is more precisely called ‘2-deoxyribose’. Instead of the hydroxyl at position 2, it has a hydrogen atom, and so is lacking an oxygen atom (and is thus ‘deoxy’) at this position.

Question 10

A process at equilibrium is said to be in a dynamic steady state.

Answer 10

FALSE
- At equilibrium, the rate of conversion of A into B is equal to the rate of conversion of B into A (so, although there may be inter-conversion of A and B, there is no net gain (or loss) of either A or B). In contrast, if B is formed from A, and converted into C, then when the rate of formation of B from A equals the rate at which B is converted into C, then B is said to exist in a dynamic steady state. So a dynamic steady state is not the same as an equilibrium.

Question 11

Fatty acids cannot be catabolised to yield ATP by substrate-level phosphorylation.

Answer 11

TRUE
-Only hexoses (6-carbon sugars like glucose) can be broken under anaerobic conditions to yield ATP by substrate-level phosphorylation. Fatty acid catabolism takes place only in the presence of oxygen.

Question 12

Fatty acids, but not glucose, can be broken partially to yield ATP in the absence of oxygen.

Answer 12

FALSE
- It’s the other way around. Only hexoses like glucose can be broken in the absence of oxygen to yield some ATP. Fatty acid degradation to yield ATP requires the presence of oxygen.

Question 13

FADH is the reduced form of FAD.

Answer 13

FALSE
-When the redox co-substrate FAD is reduced, 2 electrons and 2 protons associate with the molecule, so that it becomes FADH2. Compare this with the reduction of the redox co-substrates NAD+ and NADP+, where 2 electrons but only 1 proton associate with the molecule, producing NADH and NADPH.

Question 14

If the pKa of the dissociation of H2PO4- to HPO42- is 6.9, and the total concentration of (H2PO4- and HPO42-) in a solution at pH 6.9 is 25 mmol/L, then the concentration of H2PO4- is 12.5 mmol/L and the concentration of HPO42- is 12.5 mmol//L.

Answer 14

TRUE
-Applying the Henderson-Hasselbalch equation
(pH = pKa + log10 [A-]/[HA]), 6.9 = 6.9 + log10[HPO42-]/[ H2PO4-],
so log10[HPO42-]/[H2PO4-] = 0,
and [HPO42-]/[ H2PO4-] = antilog10 0 = 1.
Thus, if [HPO42-] = [H2PO4-]
and ([HPO42-] + [H2PO4-]) = 25 mmol/L,
then [HPO42-] = [H2PO4-] = 12.5 mmol/L.

Question 15

Endocytosis and exocytosis involve, respectively, diffusion of molecules into and out of cells.

Answer 15

FALSE
- Endocytosis and exocytosis involve, respectively, the use of membrane-bound vesicles to move molecules into and out of cells.

Question 16

Penicillins kill bacteria rather than host cells because in the latter the antibiotic is rapidlt degraded in lysosomes.

Answer 16

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.