Bio - Topic 5 Flashcards
Squid are an order of aquatic animals. Many species of squid show a reflex response to changes in their body position.
* A sensory receptor called a statocyst detects changes in the body position of the squid in their aquatic environment.
* The reflex response corrects the squid’s body position.
Describe the components and events involved in a reflex arc.
1 - action potential / nervous impulse, in sensory neurone
2 - synapse / described
3 - relay / intermediate, neurone
4 - (nervous impulse in) motor neurone, passes to / AW, effector / muscle
Suggest one benefit to the squid of the reflex response described above.
idea of maintains balance / efficiency of movement
A statocyst sensory receptor is shown in Fig. 2.1.
What can you conclude from Fig. 2.1 about the mechanism by which a statocyst acts as a transducer?
1 - kinetic / movement, energy converted
2 - to, electrical energy / action potential
3 - idea of movement of statolith moves sensory hairs
4 - membrane of sensory hairs depolarises
Lobsters and sea cucumbers also have statocysts. From this information, the student concluded:
‘I think this means squids, lobsters and sea cucumbers evolved from a recent common ancestor and are
probably classified in the same phylum.’
Evaluate the extent to which the information about lobsters and sea cucumbers supports the student’s conclusion.
Support is weak because
1 - idea that classification based on phylogeny
2 - statocysts could, have evolved on more than one occasion / be an example of convergent evolution
Use the information in Fig. 2.2 to suggest why naked mole rats do not feel pain when exposed to acid.
1 - no, action potentials / (electrical) impulses (in response to acid stimulus)
2 - (along) sensory neurones / neurones to CNS
3 - (because) no / few, voltage gated (sodium) channels open
4 - less depolarisation (of receptor membrane) / fewer Na+ ions move in
Explain how a pain receptor is an example of a transducer.
converts, chemical / stimulus, to action potential / electrical energy / electrical impulse
Explain why the incomplete breakdown of glucose in anaerobic respiration produces less
ATP than aerobic respiration.
In anaerobic respiration;
1 - glycolysis / conversion of glucose into pyruvate occurs
2 - produces 2 molecules of ATP (net)
3 - (only) substrate level phosphorylation (occurs)
4 - oxygen not available as final electron acceptor
5 - pyruvate / ethanal used to regenerate NAD for glycolysis (to continue)
6 - (Krebs cycle and) electron transport chain / chemiosmosis /
oxidative phosphorylation, do not occur
Respiration can be aerobic or anaerobic.
Certain parasites live in the blood of mammals.
Suggest why, even though blood carries oxygen, these parasites are adapted to respire
anaerobically.
1 - idea that parasites have little access to oxygen
2 - (inaccessible because)
little oxygen dissolved in plasma /
oxygen not very soluble (in plasma)
3 - (inaccessible because) idea that oxygen is, combined with haemoglobin / contained in red blood cells
4 - idea that haemoglobin has greater affinity for oxygen than parasite (pigment)
The anaerobic respiration pathway in animal cells can be reversed, but the anaerobic respiration pathway in yeast cells cannot be reversed.
Explain why, using your knowledge of the differences between the two pathways.
A1 - pyruvate is , converted / reduced to lactate / lactic acid
A2 - can be reversed as no atoms lost / other product formed
A3 - lactate dehydrogenase available
to reverse the reaction
Y1 - pyruvate converted to ethanol (in 2 steps) and carbon dioxide / CO2
Y2 - cannot be reversed as carbon dioxide is / atoms are lost
Y3 - (de)carboxylase enzyme cannot
reverse the reaction
The lactate that enters pathway S is produced by cells, such as muscle cells, undergoing anaerobic respiration.
Suggest why this lactate is converted into pyruvate by the hepatocytes (liver cells) rather than by the respiring cells in which it is produced.
1 - hepatocytes can tolerate , lactate / low pH (which would otherwise be toxic)
2 - hepatocytes have / (other) cells do not have enzymes to metabolise lactate / catalyse this reaction
3 - (conversion of lactate) requires oxygen and muscle cells do not have enough oxygen /
O2 is not available during anaerobic respiration /
O2 is sufficient in hepatocytes
Excess reduced NAD in the liver cells will influence some metabolic pathways by:
* inhibiting the conversion of lactate to pyruvate
* inhibiting fatty acid oxidation
* promoting fatty acid synthesis.
Using this information and the information in Fig. 2.1, suggest the consequences for
liver metabolism if a person has a regular high alcohol intake.
1 - build-up of lactate / prevention of pathway S poisons / kills , (liver) cells
2 - disruption of enzymes as a result of low pH
3 - idea that lack of substrate / fatty acids not available for respiration
4 - lack of (oxidised) NAD for (metabolic) reactions
5 - (some) deamination / ornithine cycle / pathway P /breakdown of (named) hormones / pathway R ,
cannot occur
6 - build-up of fatty acids / more fatty acids present resulting in fat deposits in (liver) cells / fatty liver / cirrhosis
