Anaerobic Respiration

Settler Write down 3 things you remember from KS4 anaerobic respiration Feedback to the rest of class

Learning outcomes Success criteria By the end of this lesson All students will know that ethanol and lactate are produced in anaerobic respiration Most students will be able to explain how ethanol and lactate are produced in respiration Some students will know how energy is released in respiration in the absence of oxygen. I will achieve these outcomes by- Consolidate knowledge from KS4 on anaerobic respiration Complete word equations for anaerobic respiration in plants and animals Using keywords write down an explanation of why anaerobic respiration is important and peer assess Complete application for how science works

Starter How much ATP is generated during each stage of respiration? Glycolysis Link reaction Krebs cycle Electron Transport Chain Which stages depend on oxygen (aerobic) and which occur in the absence of oxygen (anaerobic)?

Energy yields from aerobic and anaerobic respiration Glycolysis 2 ATP Link reaction Krebs cycle 2 ATP Electron transport chain 28 ATP Only glycolysis occurs in anaerobic conditions Small amount (2 ATP) of energy released during anaerobic respiration compared to aerobic (32 ATP in total)

Anaerobic respiration Why is oxygen important? Oxygen is important so the H atoms produced in glycolysis and krebs cycle can be converted to water and drive the production of ATP. What happens in the absence of oxygen? Krebs cycle and electron transport chain can’t take place and pyruvate builds up in the cell Anaerobic process of glycolysis is the only source of ATP So what happens to the pyruvate?

Glycolysis Glycogen 2 ATP 4 ADP + 4Pi 4 ATP Triose Phosphate (3C x 2) Pyruvate (3C x2) Glucose (6C) In anaerobic respiration neither Krebs cycle nor ETC can take place so glycolysis is the only source of ATP In order for glycolysis (and so ATP production) to continue, pyruvate must be removed and NAD regenerated This is achieved by reduced NAD reacting with pyruvate to produce NAD and lactate (animals)... NAD Reduced NAD 2 ADP NAD+ + 2H  NADH + H+ (oxidised form ) (reduced form)

Production of lactate in animals Human cells do this by converting pyruvate to lactate. This reaction uses reduced NAD by oxidising it to NAD once more. NAD is now available again to accept electrons and protons so glycolysis continues. If NAD is not regenerated, even glycolysis would have to stop, because there would be no oxidised NAD available to accept these electrons and protons. Write down the word equation to show how lactate is made in anaerobic respiration. Pyruvate + reduced NAD Lactate + NAD

Anaerobic Respiration in animals Oxygen shortage in muscles overcome by using anaerobic respiration e.g. During intense exercise Both forms of respiration are used simultaneously when oxygen demand outweighs supply This builds up an oxygen debt that has to be repaid

Production of ethanol in plants and some microorganisms Pyruvate loses a molecule of carbon dioxide and accepts hydrogen from reduced NAD to produce ethanol. Write down the word equation for this proces Pyruvate + reduced NAD ethanol + Carbon dioxide + NAD

Anaerobic Respiration in microorganisms and plants

Why is anaerobic respiration important? Using the keywords below write down what happens in anaerobic respiration (in animals) and why it is important. pyruvate oxygen debt oxygen glycolysis muscles NAD Glycogen cramp fatigue Reduced NAD lactate Peer assess explanations

What happens in anaerobic respiration and why it is important. Anaerobic respiration occurs mostly in the muscles when oxygen is being used up quicker than it can be supplied, so an oxygen debt occurs. In the absence of oxygen glycolysis would usually stop as there would be a build up of reduced NAD. For glycolysis to continue, reduced NAD must be converted into NAD. This happens when pyruvate takes up 2 hydrogen atoms from reduced NAD to make lactate. Lactate causes cramp and fatigue in muscle tissue so this must be removed. It can be oxidised back to pyruvate or it is taken to the liver and converted to glycogen.

Removing Lactate Lactate is oxidised back to pyruvate If sufficient oxygen is available the pyruvate then enters Krebs cycle and ETC to release lots of ATP OR pyruvate converted to glycogen for storage Why does oxygen uptake remain higher than normal following exercise? Lactate is oxidised back to pyruvate

Plenary – True and False More ATP is produced during anaerobic respiration Anaerobic respiration in yeast has been exploited by humans for the brewing industry. The krebs cycle and electron transport chain can not occur without oxygen NAD is an important product of glycolysis The replenishment of NAD for use in glycolysis is achieved by pyruvate accepting hydrogen from reduced NAD

How Science works task. Unit 5 synoptic paper requires knowledge from AS Biology. Using information from topics 3.1 and 2.7 complete the following application Investigating where certain respiratory pathways take place in cells. Page 60 – answer questions

Class and Homework Tasks Using the textbook complete the summary question on page 59 and the ‘Application and How Science Works’ questions on page 60 Complete the practice exam questions on respiration

Learning outcomes Success criteria By the end of this lesson All students will know that ethanol and lactate are produced in anaerobic respiration Most students will be able to explain how ethanol and lactate are produced in respiration Some students will know how energy is released in respiration in the absence of oxygen. I will achieve these outcomes by- Consolidate knowledge from KS4 on anaerobic respiration Complete word equations for anaerobic respiration in plants and animals Using keywords write down an explanation of why anaerobic respiration is important and peer assess Complete application for how science works