The following exercises are available in this section
A respiratory physiology practical class - and beyond
By the end of this exercise you should be able to:
- Explain in outline how oxygen is consumed and how carbon dioxide and water are produced in the oxidation of metablic fuels
- Explain how oxygen reaches tissues where it is required
- Describe in outline how metabolites may undergo oxidation
- Explain what is meant by a metabolic pathway
- Explain how it is possible to ensure unideirectional flux through a pathway even when all enzyme-catalysed reactions are reversible
An early morning jog
By the end of this exercise you should be able to:
- Define the respiratory quotient (RQ) and explain how it can be used to determine the amounts of fat and carbohydrate being metabolised
- State what are the main fuels being oxidised in the fed and fasting states
- Explain in outline how plasma glucose is maintained in the fasting state
- State the sources of fatty acids available to tissues in the fed and fasting states
Starving to slim
By the end of this exercise you should be able to:
- Define body mass index (BMI) and the desirable range
- Calculate the energy yield of adipose tissue and maximum possible rate of sustained weight loss with energy deficit
- Explain why there is an initial rate of weight loss that is greater than calculated
- Describe the processes that contribute to resting energy expenditure (the resting metabolic rate)
- Describe the main changes in plasma metabolic fuels from the fed state into fasting and starvation
- Explain how the blood concentration of glucose is maintained in fasting and starvation, and the importance of maintaining an adequate supply of glucose
- Explain the importance of ketone body synthesis and describe in outline the role of ketone bodies
- Explain how changes in the urinary excretion of urea in fasting and starvation provide information about tissue protein breakdown
Poisoned by unripe ackee fruit
By the end of this exercise you should be able to:
- Explain why a very low blood glucose concentration causes loss of consciousness
- Explain why the brain has a relatively large requirement for metabolic energy
- Describe how sodium and potassium ions can be transported against their concentration gradient and explain the role of ATP in this process
- Describe how endothermic reactions can be driven in the thermodynamically unfavoured direction linked to the hydrolysis of ATP to ADP and phosphate
- Describe the role of ATP in muscle contraction
- Explain the role of coenzyme A in metabolism
- Explain how it is that sequestering coenzyme A can lead to severe metabolic disturbance and profound hypoglycaemia
Overheating after overdosing on E - and slimming by taking dinitrophenol
By the end of this exercise you should be able to:
- Describe the process of oxidation of metabolic fuels to carbon dioxide and water linked to the phosphorylation of ADP to ATP
- Relate the obligatory linkage of phosphorylation of ADP to ATP to the oxidation of coenzymes and reduction of oxygen to water
- Explain why some substrates have a P:O ratio of ~2.5 and others of ~1.5
- Name the different types of coenzymes in the mitochondrial electron transport chain and differentiate between electron carriers and hydrogen carriers
- Explain why the overall process of oxidative phosphorylation requires intact mitochondrial membrane vesicles
- Explain how electron transport creates a proton gradient across the mitochondrial inner membrane and how this is coupled to the phosphorylation of ADP to ATP
- Explain how physical activity controls the rate at which metabolic fuels are oxidised
- Explain the actions of uncouplers and the biochemical basis of non-shivering thermogenesis.
Summary - why do we need to eat and how do we survive between meals?
By the end of this exercise you should be able to:
- Explain why there is a need for metabolic energy even when at rest
- Define Basal and Resting Metabolic Rate (BMR and RMR)
- Define Physical Activity Ratio (PAR) and Physical Activity Level (PAL)
- Explain how to measure BMR and energy expenditure in physical activity and how they can be measured
- Explain how measurement of oxygen consumption and carbon dioxide production permits estimation of the mixture of metabolic fuels being metabolised
- Explain how it is possible to measure total energy expenditure using dual isotopically labelled water
- Explain why there is an increase in metabolic rate after a meal
- Explain why women have a lower BMR than men of the same age and body weight, and why BMR falls with increasing age, even if body weight remains constant
- List the main metabolic fuels available to tissues in the fed and fasting states
- State the desirable proportions of carbohydrate, protein and fat in the diet, and explain how to calculate the percentage of energy derived from each
- Describe in outline the metabolic fate of the glucose coming from dietary carbohydrates in the fed state
- Explain how the blood concentration of glucose is maintained in the fasting state, and which alternative fuels are provided to tissues to spare glucose for tissues that absolutely require it
- Explain why free (non-esterified) fatty acids are transported in the bloodstream bound to serum albumin
- Name the ketone bodies and explain their importance in the fasting state and starvation; explain why acetoacetate is largely reduced to hydroxybutyrate in the liver.
- Describe in outline how insulin and glucagon act to regulate metabolic processes in the fed and fasting states
- Explain how extra-hepatic tissues are prevented from taking up glucose in the fasting state, so sparing it for the brain and red blood cells