module 5 - 18.6 respiratory substrates

Question 1

what are respiratory substrates?

Answer 1

molecules that can be used as an energy source to allow the production of ATP from ADP and Pi

Question 2

what is the normal respiratory substrate?

Answer 2

glucose

Question 3

what other respiratory substrates are there (not glucose)

Answer 3

• triglycerides
• proteins

Question 4

what can the fatty acids in a triglyceride molecule lead to?

Answer 4

formation of 50 acetyl CoA molecules and form up to 500 ATP molecules

Question 5

what happens to triglycerides?

Answer 5

1. triglycerides are hydrolysed into glycerol and 3 fatty acids
2. glycerol converted to pyruvate and enters respiration at link reaction
3. fatty acids hydrolysed to form acetyl groups and enter respiration at krebs cycle

Question 6

what happens to proteins?

Answer 6

1. proteins are digested into individual amino acids by proteases
2. an amino acid is deaminated, the amine group is converted to ammonia and then urea by ornithine cycle
3. remaining molecule is converted to pyruvate, which enters respiration at link reaction

Question 7

what are ketone bodies?

Answer 7

• molecules that contain a ketone group
• produced when fatty acids are broken down for respiration during a period of long calorific restriction (e.g. starvation)
• brain uses ketone bodies to synthesise fatty acids

Question 8

what does the words ‘ketone’ mean?

Answer 8

breakdown bodies from proteins

Question 9

what are RQ values?

Answer 9

• respiratory quotient values
• unitless value that is the ratio of volume of carbon dioxide produced to volume of oxygen consumed
• expressed as a single value
• indicate what is the respiratory substrate

Question 10

what is the equation for RQ?

Answer 10

CO2 produced
_______________
O2 consumed

Question 11

what is the RQ for a carbohydrate, protein, lipid or tryglyceride and anaerobic respiration?

Answer 11

1. carbohydrate: RQ = 1.0
2. protein: RQ = 0.9
3. lipid or triglyceride: RQ = 0.7
4. anaerobic respiration: RQ = above 1.0

Question 12

why is the RQ value of glucose 1.0?

Answer 12

because the volume of oxygen required to metabolise glucose in aerobic respiration is equal to the volume of carbon dioxide released from the body

Question 13

what is respiratory quotient measured with?

Answer 13

respirometer

Question 14

why do lipids/trigylcerides have a smaller RQ value?

Answer 14

• they contain more carbon-hydrogen bonds than glucose so they can produce more reduced NAD and reduced FAD and more ATPs
• this means they need less oxygen than glucose so have smaller RQ

Question 15

what does a normal human metabolism produce an RQ value of?

Answer 15

0.8-0.9 indicating a mixture of all respiratory substrates

Question 16

the respiratory quotient was calculated at intervals for a flask of germinating seeds, the RQ decreased over time from 0.1 to 0.7, why?

Answer 16

the respiratory substrate changed from carbohydrate to lipid

Question 17

what is a respirometer used for?

Answer 17

measures the rate of respiration and can be used to obtain data to calculate RQ value

Question 18

what is the potassium hydroxide/soda lime used for in a respirometer?

Answer 18

absorbing CO2 gas

Question 19

why is the apparatus a closed system?

Answer 19

separated internal and external atmosphere

Question 20

what does the apparatus measure?

Answer 20

oxygen consumption that equals CO2