1. CELLULAR RESPIRATION

2. WHAT IS IT?  Process by which all living cells break down energy rich molecules (e.g. glucose) to release energy in a useable form (ATP); heat energy is a by product  All living cells respire in order to exist although the substrates they use may vary.

3. WHERE DOES IT OCCUR?  It occurs in the mitochondria of the cells in ALL organisms ALL of the time (day and night)

5. WHAT TYPES ARE THERE?  There are two types:- 1. Aerobic – requires oxygen – produces more energy than anaerobic 2. Anaerobic – does not require oxygen.

6. SIMPLIFIED VERSION Glucose + oxygen carbon dioxide + water +energy C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + ATP

7. WHY DO CELLS NEED ENERGY (ATP)?  ATP is the so-called energy molecule in all organisms and is used to fuel all the chemical reactions in the cell e.g.  Active transport of substances across membranes  Synthesis of molecules – e.g. proteins from amino acids.  Movement – e.g. phagocytosis, action of cilia and flagella, action of muscle fibres  Bioluminescence (light production) in cells of such animals as glow-worms and fireflies.

8. WHAT IS ATP?  ATP is Adenine triphosphate and is made in cells from ADP or adenine diphosphate.  ATP Structure Ribose – a 5-carbon sugar Adenine – a N-base 3 phosphate groups  The energy from glucose breakdown adds a high – energy phosphate bond to ADP to make ATP.

9.  When a cell needs energy, the high-energy phosphate bond is broken and ATP returns to ADP  (think of ADP as the flat battery and ATP as the charged battery)  The process is very rapid and ongoing.  The heat energy produced as a by-product is used in maintaining body temperature in birds and mammals.  video video P+ADPATP Energy from the breakdown of glucose Energy released from the breakdown of ATP

10. THE STORY SO FAR….  What are the different types of respiration found in living organisms?  Where does cellular respiration occur?  What are the end products of cellular respiration?  What is the end product of cellular respiration used for ? Give 2 examples. WHAT ARE THE SPECIFICS OF CELLULAR RESPIRATION?

11. AEROBIC RESPIRATION  Needs oxygen for the complete breakdown of glucose into carbon dioxide and water  ATP and heat are released  3 main enzyme controlled chemical pathways in aerobic respiration o Glycolysis o Kreb’s cycle and o The electron transfer chain

12. GLYCOLYSIS  Occurs in the cytoplasm of the cell  Each glucose molecule is broken into two PYRUVATE molecules  TWO molecules of ATP are produced in the breakdown.  Process is the same in both aerobic and anaerobic respiration.

14. Kreb’s Cycle  Occurs in the matrix of the mitochondria Step 1  Pyruvate (in the form of acetyl CoA) is fed into a complex biochemical cycle. As the pyruvate passes around the cycle, extensive rearrangement occurs, with CO 2 molecules and H atoms being produced. The molecules that make up the cycle are not used up in the reaction.

15. Step 2  CO 2 is the waste product and diffuses out of the mitochondria and the cell. Step 3  H atoms are picked up by a carrier molecule (NAD, a co-enzyme) and taken into the third chemical pathway, the ELECTRON TRANSPORT CHAIN.

16. THE ELECTRON TRANSPORT CHAIN  Occurs on the cristae of the mitochondria 1. H atoms are ionised and their high-energy electrons are ‘bounced’ along a series of acceptor molecules (cytochromes) attached to the cristae. 2. As the electrons are ‘bounced’ along the electron transfer chain, their energy is used to form ATP from ADP 3. At the end of the electron transfer chain, the electrons are returned to the H ions, which become atoms again and combine with O 2 to become H 2 O

17.  It is this third stage of aerobic respiration which produces the most energy. One molecule of glucose that enters glycolysis yields 38 molecules of ATP by the end of the electron transfer chain.  video video

18. The equation for aerobic respiration is: Word equation Glucose + oxygen carbon + water + ATP + heat dioxide Formula Equation C 6 H 12 O 6 + O 2 CO 2 + H 2 O + ATP + heat

19. Factors affecting the rate of respiration  The amount of oxygen present in the cells  The amount of glucose or fat present in the cell  The cell or body’s demand for energy  Temperature: the higher the temperature, the greater the rate of respiration (up to a point)

20. Reading and Questions Read pages 126 – 127 in Excellence in Biology. Answer questions 9 – 16 pages 103 – 104 in your workbook.

21. ANAEROBIC RESPIRATION  Occurs in the absence of oxygen  Only glycolysis takes place, therefore only 2 molecules of ATP are produced from each glucose molecule.

22. ANAEROBIC RESPIRATION IN ANIMALS  Occurs when oxygen is in short supply e.g. during prolonged exercise  The pyruvate formed in glycolysis is broken down into lactic acid.  Lactic acid causes muscle fatigue  The muscles need to stop working to allow replenished supplies of oxygen to continue the breakdown of lactic acid into water and carbon dioxide.

23. ANAEROBIC RESPIRATION IN YEAST AND BACTERIA  In yeast, the pyruvate is broken down into ethanol, C 2 H 5 OH and carbon dioxide  This is also known as fermentation  The small energy yield of 2 ATP molecules is sufficient to meet the lifestyle needs of these organisms.  Word equation Glucose ethanol + carbon dioxide + ATP + heat  Formula equation C 6 H 12 O 6 2C 2 H 5 OH + CO 2 + ATP + heat

24.  Fatty acids and glycerol (from the digestion of fats), and amino acids (from the digestion of proteins), can also be used in respiration (entering the Krebs cycle after prior processing) to generate ATP.

25. RATE OF RESPIRATION Rate of respiration is determined by factors such as: Temperature – increasing temperature increases rate of respiration up to an optimum temperature, the enzymes controlling the reaction denature and can no longer catalyse reactions; respiration ceases and the organism dies. Body’s energy demands – The rate of respiration will increase up to a maximum as the demand by the cells of tissues increases. The amount of O 2 needed and the amount of CO 2 produced increased, and breathing rate increases to compensate. The build up of CO 2 will slow down the rate of respiration.

26. QUESTIONS 1. Distinguish between the following pairs of terms: a. Mitochondria and chloroplasts b. Grana and stroma c. Light dependent and light independent d. Glycolysis and Krebs cycle e. Krebs cycle and electron transfer chain f. Calvin cycle and Krebs cycle

27. 2. Explain the structure of: a. Chloroplasts b. Mitochondria 3. Explain why so much energy is produced in aerobic respiration compared with anaerobic respiration.