Different Respiratory Substrates And RQ Values

Question 1

What is a respiratory substrate?

Answer 1

An organic molecule that can be used in respiration to release energy

Question 2

What is the most commonly respired substrate?

Answer 2

-carbohydrate glucose, and some cells can’t respire any other substrate (brain cells, RBC)

Question 3

Explain the respiration of carbohydrates

Answer 3

-monosaccharide glucose is the main carbohydrate used by cells for respiration
-polysaccharides and disaccharides can both be hydrolysed (using enzymes) into monosaccharides and then respired

Question 4

Explain the respiration of lipids

Answer 4

-lipids are very important, especially in muscle cells
-they’re first hydrolysed into fatty acids and glycerol
-glycerol can be converted to Pyruvate and enter the respiratory pathway at that point
-fatty acids combine with coxenzyme A to form a complex, which is then carried into the mitochondrial matrix forming acetyl co A (beta-oxidation pathway) then enters Krebs cycle

Question 5

Explain the respiration of amino acids/ proteins

Answer 5

-these are not usually respired, either used to make important protein structures in the body or converted to urea for excretion
-however if an organism undergoes fasting, starvation or prolonged exercise, then amino acids from proteins hydrolysis may then be respired

Question 6

Explain what an RQ value is and give the equation

Answer 6

-it’s the ratio of carbon dioxide released by a respiring organism to oxygen consumed in a given time
-it tells us what respiratory substrate is being metabolised by an organism and what type of respiration, aerobic or anaerobic is being employed
-as it’s a ratio no units are needed

RQ= Co2 released /
O2 uptake per unit time

Question 7

What are the RQ values of the respiratory substrates glucose, proteins and triglycerides

Answer 7

Glucose = 1.0
Proteins = 0.9
Triglycerides = 0.7

Question 8

How do you know if respiration is aerobic or anaerobic just from the calculated RQ value?

Answer 8

-aerobic respiration will always give an RQ value of 1.0 or less
-anaerobic respiration (or some) will have an RQ value of more than 1.0, because more co2 is produced than oxygen consumed c