Quiz 2

Question 1

The predominant component of human hair is the protein collagen.

Answer 1

FALSE

-The major component of hair is the (water-soluble) protein a-keratin.

Question 2

Glycolysis and the citric acid cycle produce the reduced co-reactants used in fatty acid biosynthesis.

Answer 2

FALSE
-Glycolysis and the citric acid cycle result in generation of NADH, and NADH and FADH2 respectively. The redox co-reactant used in fatty acid biosynthesis is NADPH. A major source of this is the pentose phosphate pathway.

Question 3

Simple epithelia have one layer of cells.

Answer 3

TRUE

-Epithelia with 2 or more layers of cells are known as stratified epithelia.

Question 4

Desmosomes form watertight seals between adjacent lateral borders of epithelial cells in an epithelial sheet.

Answer 4

FALSE
-Tight junctions form watertight seals between adjacent lateral borders of epithelial cells in an epithelial sheet. Desmosomes provide form anchorage points between cells but do not provide for a watertight seal between cells.

Question 5

Concerning neurones: The dorsal root ganglia contain cell bodies of efferent neurones.

Answer 5

FALSE
-The dorsal root ganglia contain the cell bodies of afferent neurones. Motoneurones, the classic example of an efferent neurone, have their cell bodies in the grey matter that forms the ventral horn of the spinal cord.

Question 6

Concerning neurones: Saltatory conduction describes the conduction of membrane potentials that are generated by the movement of Na+ and Cl-.

Answer 6

FALSE
-Saltatory conduction.describes the conduction of an action potential along a myelinated axon in which the axon potential is not generated along the entire length of the axon, but instead jumps from one node of Ranvier to the next. Saltator is Latin for dancer.

Question 7

Regarding basic pharmacology: Each neurotransmitter typically acts on a single type of receptor.

Answer 7

FALSE

-Most neurotransmitters can act on several different receptors, producing a variety of effects.

Question 8

Transaminases require vitamin B2 as a cofactor.

Answer 8

FALSE
-Transaminases use as a cofactor pyridoxal phosphate, which is made from vitamin B6. (B2, incidentally, is riboflavin, essential in the diet for the production of FAD).

Question 9

Addition of an amino group to glutamate produces glutamine.

Answer 9

TRUE
-This is the reaction catalysed by glutamine synthase. The ‘extra’ nitrogen present in glutamine is present in the R group. The R group of glutamate is -(CH2)2COO-, and the R group of glutamine is -(CH2)2CONH2.

Question 10

During fatty acid β-oxidation, water is released.

Answer 10

FALSE

-The process of β-oxidation involves a hydration, not dehydration step.

Question 11

A simple gland is one which has only one type of secretory acinus.

Answer 11

FALSE
-A simple gland is one which has only one duct, not a network of branched ducts. The single duct may have more than one acinus draining into it - both of these may be the same type or be different types.

Question 12

In endocrine glands, the blood capillaries are lined by simple squamous epithelial cells with fenestrae.

Answer 12

TRUE

-The fenestrae allow for the easy passage of hormones from the secretory cells into the blood stream.

Question 13

Regarding electrical signalling by graded potentials: Graded potentials are only suited to signalling over short distances.

Answer 13

TRUE
-Graded (or decremental) potentials quickly decay as they travel along the membrane. To conduct electrical signals over any decent distance requires the use of a self-propagating action potential.

Question 14

With regard to membrane potentials: Excitatory postsynaptic potentials are all-or-none potentials.

Answer 14

FALSE
-They are graded potentials which can vary, for example, according to the amount of neurotransmitter that is released . It is the summation of graded postsynaptic potentials that allows synaptic integration.

Question 15

Transaminases require vitamin B2 as a cofactor.

Answer 15

FALSE
-Transaminases use as a cofactor pyridoxal phosphate, which is made from vitamin B6. (B2, incidentally, is riboflavin, essential in the diet for the production of FAD).

Question 16

Bile salts, used in lipid digestion, are made in the pancreas and stored in the liver before moving to the small intestine.

Answer 16

FALSE

-Bile salts are made in the liver and stored in the gallbladder before use in the small intestine.

Question 17

Tendons are composed of dense irregular connective tissue.

Answer 17

FALSE
-Tendons are composed of dense regular connective tissue - the collagen fibres are orientated in one plane. Skin is an example of where you would find dense irregular connective tissue.

Question 18

Regarding electrical signalling by graded potentials: Graded potentials can signal stimulus intensity in their amplitude.

Answer 18

TRUE
-That is why they are called graded. You can think of a strong stimulus producing a large receptor (or generator) potential at a sensory receptor, or a lot of transmitter release evoking a large postsynaptic potential at a synapse.

Question 19

Amino-acids derived from turned over body protein pass their amino-group nitrogen to oxaloacetate in deamination reactions.

Answer 19

FALSE
-Amino-acids derived from turned-over body protein pass their amino-group nitrogen to α-ketoglutarate in transamination reactions. In so doing, the α-ketoglutarate is converted into glutamate, and the amino-acid is left as a carbon skeleton, that is, the amino-acid’s corresponding α-keto-acid.

Question 20

Oxaloacetate is the α-keto-acid corresponding to aspartate.

Answer 20

TRUE
-An α-keto-acid (also sometimes called an α-oxo-acid) is simply the carbon skeleton of an α-amino-acid. An α-amino-acid has, attached to the α-carbon, an R group, a hydrogen atom, an α-carboxyl group, and an α-amino group. The α-keto acid has exactly the same structure as the corresponding α-amino acid, but has been ‘deaminated’. This means that the α-amino group and the hydrogen atom have been removed, and have been replaced with a =O group. The α-carboxyl group and the R group are still there. The R group for aspartate is -CH2COO-. (It’s very similar to that of glutamate, but that has an extra C in the side chain, to make it –(CH2)2COO-.) If aspartate is deaminated in the way described, then oxaloacetate, the 4-C acceptor of the acetyl group from acetyl CoA in the citric acid cycle, is produced. This means that aspartate and oxaloacetate are inter-converted in a transamination reaction.

Question 21

Sickle-cell haemoglobin, in solution at pH 7, has a greater negative charge than does normal haemoglobin.

Answer 21

FALSE
-Since the mutation to produce sickle-cell haemoglobin causes the protein to be made with valine (an amino-acid with an uncharged R group) in a place normally occupied by glutamate (an amino-acid with a negative charge at pH 7), the mutant protein has a lesser negative charge than does normal haemoglobin.

Question 22

Loss of skin elasticity and increasing brittleness of bone with age is due to changes in elastin structure.

Answer 22

FALSE

-The changes described are largely due to increased covalent cross-linking of collagen fibrils.

Question 23

Concerning synaptic transmission and synaptic integration in the central nervous system: Autoreceptors are located on the presynaptic terminals of neurones.

Answer 23

TRUE
-Autoreceptors bind the same transmitter that the terminal releases. They are often of the g-protein coupled family and are ideally placed to perform a negative feedback role by inhibiting further release of transmitter.

Question 24

Regarding basic pharmacology: Each neurotransmitter typically acts on a single type of receptor.

Answer 24

FALSE

-Most neurotransmitters can act on several different receptors, producing a variety of effects.

Question 25

Metabolism of nitrogen into and through the urea cycle is accompanied by ATP synthesis.

Answer 25

FALSE
-Dephosphorylation of ATP (not its synthesis) occurs during metabolism through the urea cycle. The formation of carbamoyl phosphate from ammonium ion and carbon dioxide requires dephosphorylation of 2 ATP to produce ADP, and the conversion of citrulline to arginosuccinate during the cycle requires conversion of ATP to AMP. So, production of urea for excretion requires an input of energy.

Question 26

Hyperammonaemia is a complication of cirrhosis of the liver.

Answer 26

TRUE
-Processes that compromise liver function interfere with the processing of nitrogen for excretion. Detoxification of ammonium ions is impaired, and elevated ammonium ion concentration in the plasma (hyperammonaemia) is the result.