Respiration How cells release energy You must be

Respiration How cells release energy

You must be able to: • State that glucose is a source of energy in cells. • State that the energy in glucose is released by a series of enzyme controlled reactions called respiration.

Need for energy • Why do we need energy?

Energy gain • Where do we get the energy from? Food • What type of energy does it contain? Chemical

Energy gain • What organisms make the food? • How? Green plants

Energy gain • What food is made by plants? Glucose formed and changed to starch • How do humans get the energy from the plants?

Energy in cells • The chemical energy in glucose cannot be used directly by cells. • RESPIRATION = the process that releases energy from food to be used by cells.

Controlling respiration • Respiration is a series of chemical reactions. • What controls the rate of the chemical reactions in respiration? • Respiration is enzyme-controlled.

You must be able to: • State the units energy content of food is measured in. • Compare the energy content of different foods.

Energy in food • Look at any food or drink wrapper. • What units is energy content measured in? joules [J] or kilojoules [k. J]

Measuring energy in food • Content measured in kilojoules (k. J). • Unit of heat energy. • How can we compare the energy content of three different crisps?

Energy content of food practical

Aim • To measure the energy content of food Method described could be used

Method 1. Put 20 cm 3 of cold water into a boiling tube. 2. Measure the starting temperature with a thermometer. 3. Place boiling tube into a clamp and stand. Heatproof mat 4. Place bunsen onto a heat proof mat and light.

Method 5. Hold food in tongs. 6. Set the food on fire and place it underneath the boiling tube until it is completely burnt. 7. Measure the final temperature of the water. 8. Repeat this process using fresh water with the same type of food.

Results • Use the following sum to calculate the change in temperature: final temperature starting = temperature rise in temperature

Aim • To compare the energy content of 3 different types of crisp.

Comparing energy in crisps Design an experiment to compare the energy content. Available apparatus: • • • Clamp and stand Heat proof mat. Boiling tube. 3 types of crisp. Measuring cylinder. • • Bunsen burner. Tongs. Water. Thermometer.

Feed back ideas Collect: • Clamp and stand • Heat proof mat. • Boiling tube. • 3 types of crisp. • Bunsen burner. • Tongs. • Water. • Thermometer. • Measuring cylinder. • Goggles

Method 1. Put 20 cm 3 of cold water into a boiling tube. 2. Measure the starting temperature with a thermometer. Complete first 2 columns in results table. 3. Place boiling tube into a clamp and stand. Heatproof mat

Method 4. Place bunsen onto a heat proof mat and light. 5. Hold one of the crisps in tongs. 6. Set the crisp on fire and place it underneath the boiling tube until it is completely burnt.

Method 7. Measure the final temperature of the water and write it into the results table. 8. Repeat this process using fresh water with the same type of crisp. 9. Repeat the process for the other two crisps.

Results • Use the following sum to calculate the change in temperature: final temperature starting = temperature rise in temperature

Results • Work out the average rise for each of the 3 types of crisp. • How do you work out an average?

Questions 1 Which type of crisp caused the greatest temperature increase? 2 Which type of crisp contained the least energy? 3 Why is it unlikely that this technique gives a very accurate measure of energy content.

Measuring energy in food • To make an experiment fair you can only change one variable at a time. • What variable have we changed? • Type of crisp.

Comparing energy in food • What variables were kept the same? Controlled variables: • • • Volume of water. Position of thermometer. Position of flame underneath. Crisp is completely burnt. Mass of crisp.

A Food Calorimeter. This equipment makes results more reliable because: Stirrer Enclosed vessel Oxygen supply Chimney

Comparing energy in food • How were the results made more reliable?

Revision • What type of energy is in food? Chemical • What process allows this energy to be released to be used by cells? Respiration • What unit do we use when discussing the energy content of food? joules

You must be able to: • State that energy released from the breakdown of glucose is used to synthesise ATP from ADP and Phosphate. • State that ATP can then be used by the cell as an energy source.

Respiration • A series of enzyme controlled reactions. • Involves the breakdown of respiratory substrates like glucose. • Glucose is rich in energy

Respiration Results in: • Release of waste products. • Release of ENERGY.

Respiration • Energy release gradual to avoid cell damage. Can be converted to: • Heat energy or Chemical energy. • Chemical energy stored in ATP molecules.

ATP • Adenosine triphosphate. • Found in all cells. • Transfers chemical energy that all cells can use immediately.

ATP Composed of: • A molecule of adenosine. • 3 inorganic phosphate (Pi) molecules. • Bonds between molecules contain energy.

ATP breakdown When the end Phosphate is removed by an enzyme: • ADP (adenosine diphosphate) is formed. ENERGY RELEASE • Phosphate is released. • ENERGY is released – can be used by cells.

ATP synthesis When energy becomes available: • ATP is synthesised. • Phosphate is used up. • ENERGY is stored. Energy Stored

Summary • Breakdown – energy is released as the bonds break. • Synthesis – energy is stored as bonds form.

Revision • • • What does ATP stand for? ATP is made of Adenosine and 3____? What is stored in the bonds? What is the function of ATP? Describe what happens when ATP breaks down.

You must be able to: • State what energy is used for in cells.

Energy transfer ATP transfers energy from respiratory substrates (glucose) to cells allowing: Cell Division Synthesis of Proteins Muscle Contraction Transmission of nerve impulses

Energy transfer Respiration Energy transfer Cell processes Energy releasing reactions Energy transferred by ATP Energy consuming reactions glucose ADP + Pi Energy Waste Products Muscular contraction Energy ATP Or Cell Division

ATP pupil demo Pi released as bonds break ADP Respiration Releases energy y em nerg e l a ic s ch r e f s n tra ATP Energy used to add extra Pi Energy requiring reaction

ATP pupil demo You will need: • 1 pupil to represent Adenosine • 6 pupils to represent Phosphates • 1 pupil to represent respiration (with 3 energy vouchers) • 1 pupil to represent an energy requiring reaction

ATP pupil demo • Stick the appropriate cards on each volunteer. • Sit respiration and energy requiring reaction at opposite ends of the room. • Form ADP (3 pupils holding hands).

ATP pupil demo • ADP travels to the respiration reaction and second phosphate picks up energy voucher. • This energy is used for a third Pi to join on = ATP. • ATP transfers the energy to the energy requiring reaction.

ATP pupil demo • As the bond between the second and third phosphates break, energy is made available for the reaction. • The final Pi breaks off, leaving ADP ready to start again.

Collect handout and make poster • Cut out these key points in ATP production. • Use them to make a poster that shows the synthesis and breakdown of ATP.

Describe the structure, formation and breakdown of ATP (5) • ATP is composed of 1 adenosine and 3 inorganic phosphate molecules • Joined by chemical bonds which contain energy • Respiration releases chemical energy from food • Formation occurs when this energy is used to join ADP and Pi together to make ATP • ATP transfers chemical energy • Breakdown involves final chemical bond breaking to release energy • Leaving ADP + Pi

Revision • Why is respiration important? • Name a substance that can be broken down to release energy • What does ATP stand for? • What is the function of ATP? • Where is the energy stored? • When ATP breaks down what is left? • Give 2 examples of energy consuming reactions within a cell.

You must be able to: • State that aerobic respiration yields 38 ATP molecules per glucose molecule • State that anaerobic respiration yields 2 molecules of ATP per glucose molecule

Types of respiration 2 types of respiration: • Anaerobic • Aerobic What is the difference?

Aerobic respiration • Oxygen is required. • Respiratory substrate completely broken down. • Large amount of energy released. • 38 ATP are synthesised from 1 glucose molecule.

Anaerobic respiration • Oxygen is not required. • Respiratory substrate not completely broken down. • Small amount of energy released. • 2 ATP are synthesised from 1 glucose molecule.

Questions • Why is respiration important? • What are the 2 types of respiration? • How many ATP molecules are gained in aerobic respiration? • How many ATP molecules are gained from anaerobic respiration?

Chemistry of respiration

You must be able to: • Describe the pathway of aerobic respiration. • Describe GLYCOLYSIS (the first stage of respiration) as the breakdown of glucose to form pyruvic acid. • State that glycolysis takes place in the cytoplasm.

Glycolysis • Takes place in the cytoplasm. • Requires no oxygen.

Glycolysis Glucose is broken down in a series of enzyme controlled reactions to pyruvate. • A little energy is released. Glucose Enzyme controlled reactions 2 ADP + Pi + Energy 2 ATP Pyruvic Acid Enough energy is released to give a net gain of 2 ATP

Revision • What is respiration that uses oxygen called? • What is the net gain of ATP from the breakdown of 1 glucose molecule in anaerobic respiration? • What is the first stage of respiration called? • What is glucose converted to? • What is the net gain of ATP?

You must be to: • State that after glycolysis, pyruvic acid is broken down to carbon dioxide and water in the presence of oxygen.

Fate of pyruvic acid • Fate of Pyruvic acid depends on whether oxygen is present or absent. • In which case do you think more energy will be released?

Fate of pyruvic acid if O 2 present Each molecule of pyruvic acid enters a mitochondrion.

Oxygen present Aerobic respiration takes place. • Pyruvic acid completely broken down to CO 2 and water. • CO 2 is a poisonous waste which is quickly removed. • Energy released to synthesise further 36 ATP molecules.

Aerobic respiration Pyruvate Many Enzyme controlled reactions in mitochondrion 36 ADP + Pi + Energy 36 ATP CO 2 + water • How many ATP molecules are gained in total? Write on boards

Aerobic respiration • 2 ATP from Glycolysis • 36 ATP from Pyruvic acid = 38 ATP

Anaerobic respiration • No oxygen present. • Pyruvic acid stays in the cytoplasm.

Anaerobic respiration • Oxygen is absent Pyruvic acid • Pyruvic acid not completely Many Enzyme broken down. controlled reactions in cytoplasm • NO EXTRA ENERGY. • Waste products are poisonous and not easily removed. • May cause cell damage (lactic acid in animals) No Extra energy Poisonous waste

Anaerobic respiration • How many ATP Molecules are gained in total? ? Write on board

Anaerobic respiration • 2 ATP from Glycolysis • 0 ATP from Pyruvic acid = 2 ATP

Revision • What is the first stage of respiration called? • What are the 2 products? • What substance must be present to allow aerobic respiration to proceed? • How many molecules of ATP are gained from the complete breakdown of 1 glucose molecule in aerobic respiration? • Name the additional products of this aerobic pathway? • What is the function of ATP?

Anaerobic respiration in animal cells

You must be able to: • Describe the reversible anaerobic conversion of pyruvic acid to lactic acid in animals • State that the build up of lactic acid leads to muscle fatigue. • Explain oxygen debt.

Anaerobic respiration in animal cells • Occurs when no oxygen is available or when oxygen runs out. • e. g. vigorous exercise. • Pyruvic acid converted to lactic acid.

Anaerobic respiration in animal cells Lactic acid causes: • Muscle weakness (fatigue) • Muscle damage (stiffness)

Removal of lactic acid Removed from cells by converting it back to pyruvic acid. Requires extra oxygen. Supplied by breathing heavily.

Removal of lactic acid • The extra oxygen required to remove lactic acid is called the: • OXYGEN DEBT

Removal of lactic acid • Anaerobic respiration in animals is reversible. Pyruvic acid Oxygen absent Oxygen debt Oxygen present repaid Oxygen debt Builds up Lactic acid

Describe anaerobic respiration in animals (5) • • • Enzyme controlled Glucose converted to pyruvate This is called glycolysis Glycolysis occurs in cytoplasm Energy is released to produce two ATP No oxygen present Pyruvate converted to lactic acid Oxygen debt builds up Incomplete breakdown of glucose/reversible

Anaerobic respiration in plants

You must be able to: • Describe the irreversible anaerobic conversion of pyruvic acid to ethanol and carbon dioxide in plants and yeast. • State that another name for anaerobic respiration is fermentation.

Anaerobic respiration in plants • In plant cells fermentation occurs when no O 2 is available. • Pyruvate is broken down to ethanol and CO 2.

Anaerobic respiration in plants • Both are poisonous but the CO 2 is easily and quickly removed. • How does it leave cells?

Anaerobic respiration in plant cells • Accumulation of ethanol will kill the cell. • Anaerobic respiration in plant cells is irreversible. Pyruvic acid ethanol and carbon dioxide

Describe anaerobic respiration in plants (5) • • Enzyme controlled Glucose converted to pyruvate This is called glycolysis Glycolysis occurs in cytoplasm Energy is released to produce two ATP No oxygen present Pyruvate broken down to carbon dioxide and ethanol • Incomplete breakdown of glucose/irriversible

Revision • Give another name for anaerobic respiration. • When does fermentation occur. • What are the products of fermentation in plants? • Give a use for each product. • Is fermentation in plants reversible?

You must be able to: • Describe where the different stages of aerobic respiration and fermentation occur. • Give examples of cells that require large numbers of mitochondria.

Mitochondrion • Plural = mitochondria. • Cell organelles involved in the process of respiration.

Sites of respiration Anaerobic respiration (fermentation) occurs in the cytoplasm. Aerobic respiration starts in the cytoplasm and is completed in the mitochondron.

Numbers of mitochondria Large numbers are found in cells which require large amounts of energy. • e. g. Muscle cells for contraction, liver cells for metabolic processes and sperm cells for movement.

Revision • Where in a cell does anaerobic respiration occur? • Name the stage of aerobic respiration that occurs in the cytoplasm. • Where is aerobic respiration completed? • What type of cells require many mitochondria? • Give an example of such a cell.

Lactic acid build up practical

Aim • To find out the effect of repeated exercise on muscle strength.

Method • Using 2 hands, squeeze the set of bathroom scales with as much force as possible. • Write down the reading.

Method • Hold your hands out in front of you. • Raise them into a waving position with fingers stretched back. • Clench them into tight fists. • Repeat this for 1 minute. • Squeeze the scales again and write down the reading.

Percentage change • To work out a percentage decrease: • Work out the difference between the initial (first) and final (second) squeeze. • Do this by: Initial – Final.

Percentage change • Divide the difference you have just worked out by the initial (first) squeeze. • Multiply the answer by 100.

Results • What did you find out? • Why did you muscles have less force the second time?

Conclusion • A lack of oxygen during exercise leads to the build up of Lactic acid. • Lactic acid makes your muscles ache and reduces their strength. • This is called muscle fatigue. • Fill in conclusion.

Make a colourful poster to show the differences between aerobic and anaerobic respiration in humans G O CO W E • 1 Glucose + oxygen CO 2 + Water + 38 ATP • 1 Glucose Lactic acid + 2 ATP

You must be able to: • State that without oxygen, only a little energy can be released from food. • State that in yeast cells, alcohol and carbon dioxide are also made. • Describe industrial uses of the products of fermentation.

Products from yeast • Yeast is a living organism. • It is a single-celled fungus. • Yeast uses glucose as a food source to release energy. • Yeast carries out aerobic respiration in the same way as all other living things.

Anaerobic respiration in yeast • Yeast cells can also break down glucose to release energy without using oxygen. • The products in this case are very useful. • Do you know any industries where yeast is used in this way?

Anaerobic respiration in yeast The products of anaerobic respiration in yeast are used in: • Beer making. • Wine making. • Bread making. • But what are these products?

Anaerobic respiration in yeast Yeast + glucose CO 2 + Ethanol + energy This process is also called fermentation.

Match product to use Rising dough Gassy beer Wine Fuel - Gasohol Yeast + Glucose CO 2 + Ethanol + energy

You must be able to: • Describe how fermentation is used to produce yoghurt.

How is yoghurt made?

Lactic acid bacteria • Bacteria. • Added to milk. • Milk contains lactose sugar.

Lactic acid bacteria • Bacteria carry out fermentation. • Convert lactose sugar to lactic acid. • Produces yoghurt.

Revision • Describe yeast. • What is the fermentation (anaerobic respiration) equation in yeast? • Give 2 uses of the products of fermentation in yeast. • Which type of sugar is in milk? • Describe how do bacteria make yoghurt?

Summary of respiration Aerobic respiration In all organisms Glycolysis (cytoplasm) Reactions if. . End Products Energy yield Breakdown of glucose Anaerobic respiration in animals Anaerobic respiration in plants/yeast glucose 2 ATP Pyruvic acid Pyruvate Oxygen 36 ATP Oxygen present CO 2 & Water glucose absent Lactic acid 38 ATP 2 ATP Complete Incomplete 2 ATP Pyruvate Oxygen absent Ethanol + CO 2 2 ATP Incomplete

• Matching • Make cards • Torrance multichoice