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Metabolism worksheet with answers
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Exam of 13 pages for the course Biomedical science, BIOC 192 at Biomedical science, BIOC 192
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BIOC 192 Metabolism Worksheet Answers1. Define catabolism.
Catabolism is the breakdown of complex molecules to gain energy.
2. Define anabolism.
Anabolism is the build-up of complex molecules to store energy.
3. Describe the perfect energy balance.
Where Einput = Eoutput.
4. Is someone storing energy in positive or negative energy balance? Positive.
5. What is the equation used to describe energy intake and output?
Einput = Eoutput + Estored.
6. What chemical is used to feedback to the brain to stop eating? What happens with
this chemical in obese people?
Leptin feeds back to the brain to indicate that no more intake is needed. Obese
people tend to have high leptin levels, but they are leptin-resistant.
7. How many joules is one calorie equal to? 4.184J.
8. What method is used to measure the energy content in food?
Bomb calorimetry. It involves burning of food and measurement of heat released to
determine how much energy is contained within the food.
9. What are Atwater factors? Why are they adjusted?
Factors describing the energy from food. They are adjusted to account for the energy
in food that is not available to us (e.g. cellulose).
10. Describe the two processes used to measure energy output:
Direct calorimetry: uses a full body calorimeter to determine heat output.
Indirect calorimetry: measures gas exchange using respirometers to
determine the amount of CO2 produced and O2 consumed.
11. Which of these is best for determining basal metabolic rate? Direct.
12. Which of these is best for measuring respiration exchange ratio? Indirect.
13. What is the equation for calculation respiration exchange ratio?
RER = CO2 produced/O2 consumed.
14. How can RER be used to determine what kind of fuel is being used?
Carbohydrates have an RER of 1, fatty acids have an RER of 0.7.
, 15. Identify some factors that affect basal metabolic rate.
Genetics, age, sex, body size, fever, drugs, training, sleep, malnutrition,
hyperthyroidism, and hypothyroidism.
16. What is the effect of hypothyroidism and hyperthyroidism on basal metabolic
rate?
Hyperthyroidism involves an increase in basal metabolic rate, while hypothyroidism
decreases basal metabolic rate. This is because thyroxine affects Na +/K+ ATPase.
17. Describe carbohydrate digestion in the following stages:
In the mouth: Salivary amylase in saliva breaks polysaccharides down into
oligosaccharides by hydrolysing 1-4 and 1-6 glycosidic bonds.
In the stomach: The amylase is denatured. There may be some mechanical
digestion to break down carbohydrates here.
In the small intestine: Pancreatic amylase hydrolyses 1-4 and 1-6 glycosidic
bonds, breaking oligosaccharides down into disaccharides. On the luminal
surface of enterocytes, Disaccharidases (lactase, maltase, isomaltase, and
sucrase) break these down into monosaccharides.
Absorption: SGLT1 is used for secondary active symport of Na+ with glucose.
The sodium gradient is set up by Na+/K+ ATPase on the basolateral
membrane. Glucose is then passively transported out of the enterocyte and
into the blood by GLUT2.
18. Describe the process of fat digestion in the lumen.
Fat digestion involves solubilisation by bile salts and lecithin. They form micelles in
the lumen and lipase can hydrolyse the triacylglycerols to MAGs and fFAs with the
help of colipase. These are then passively absorbed across the luminal membrane.
19. What does bile contain?
Bile salts, lecithin, water, electrolytes, phospholipids, and bilirubin.
20. How are bile salts created?
Cholesterol is hydroxylated in the liver to make it more hydrophilic on one side.
21. What causes gall stones?
High concentrations of cholesterol leading to precipitation into gall stones.
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