MIDDLETOWN HIGH SCHOOL SOUTH BIOLOGY BOOKLET 10 NAME: CLASS: 1 S.Tagore Middletown South High School March 2013
LEARNING OUTCOMES The role and production of ATP (a) Importance, role and structure of ATP (b) Regeneration of ATP from ADP and inorganic Phosphate. (c) Energy from ATP comes from the breaking of the bond between the second and third inorganic phosphates Glycolysis (c) The location and significance of Glycolysis (d) Describe what happens during Glycolysis. (e) State that Glycolysis does not require Oxygen Krebs (Tricarboxylic Acid, Citric Acid) Cycle (f) The location and significance of Krebs cycle (g) Describe what happens during Krebs cycle (h) Krebs cycle only occurs in the presence of oxygen Cytochrome System (i) The location and significance of the cytochrome system (j) Describe what happens during cytochrome system. (k) Describe the role of oxygen in the cytochrome system Aerobic and Anaerobic Respiration (l) Distinguish between Aerobic and Anaerobic Respiration with reference to the levels of ATP production and final metabolic products in plant and animals. 2 S.Tagore Middletown South High School March 2013
ADENOSINE TRIPHOSPHATE ATP or Adenosine triphosphate is a high-energy molecule that stores the energy we need to do just about everything. ATP is made up of one adenosine group and three inorganic phosphates. Energy is stored in this bond ATP is made from two low energy molecules called ADP and Pi or adenosine diphosphate and one inorganic phosphate. The combining of ADP + Pi to make ATP is an energy consuming process. This is because the energy is stored in the bond between inorganic phosphate 2 and 3. + energy The breakdown of ATP to ADP + Pi is an energy releasing process. This occurs when the bond between inorganic phosphate 2 and 3 is broken. The energy required for the formation of ATP from ADP + Pi comes from the respiration of glucose. ATP is the energy source for: o Muscle contraction o Cell division o Building up (synthesis) of proteins o Transmission of nerve impulses 3 S.Tagore Middletown South High School March 2013
When ATP is broken down into ADP + Pi, energy is released. This energy is transferred to another molecule so a chemical process can take place, for example, a muscle contracting. 1 ATP ADP + Pi 3 2 Muscle Contraction Stage 1: ATP is being broken down into ADP + Pi. The bond between the terminal inorganic phosphate and the second is broken. This releases energy. Stage 2: The energy released from ATP is transferred into another cellular process. In this example it is the contract of muscle fibres. Stage 3: If there is energy present, ADP + Pi can become bonded back together again to form ATP. This process requires energy and will no t occur without it. This shows that the formation of ATP from ADP + Pi is a reversible process KEY FACTS Respiration is a chemical process in which energy is released from food molecules in cells. The cell s main energy source is glucose. Energy is released from glucose using a series of enzymes to control each stage of the breakdown process. Enzymes are needed so that our cells do not use all their energy at once or release it too slowly. The energy released from glucose is converted into high energy ATP molecules, which are recharged from ADP + Pi. 4 S.Tagore Middletown South High School March 2013
AEROBIC RESPIRATION Aerobic respiration is the process by which energy is released from glucose in cells using oxygen. There are two stages involved in the breakdown of glucose. The first stage is the splitting of glucose this is known as glycolysis. Glycolysis occurs in the cytoplasm of a cell. Glucose is a 6-carbon sugar. In respiration, it is broken down in a series of enzyme catalysed reactions, to two 3-carbon molecules called pyruvic acid. To start the process of splitting glucose apart, energy is needed. The body uses energy in the form of ATP molecules. The series of reactions eventually produces four ATP molecules, so there is a net gain of two ATPs from glycolysis. During the transformation of glucose into pyruvic acid, the hydrogen that is removed is bound to a substance known as a co-enzyme called NAD (nicotineamide adenine dinucleotide) which is reduced to NADH2. In a later process of cell respiration, the energy from the NADH2 will be used to produce ATP. The co-enzyme NAD is a molecule that acts as a hydrogen acceptor and carrier. The process of glycolysis in an anaerobic process. This means that it does not require oxygen. 5 S.Tagore Middletown South High School March 2013
Task 3: Complete the questions that follow. Make sure that you check with your teacher to ensure you have the correct answers. 1. Using the notes on the previous page, complete the flow diagram of glycolysis. 2. What is the role of NAD? 3. Where does glycolysis take place in a cell? 4. What is the total number of ATP produced in glycolysis? 5. Why is there only a net gain of two ATP molecules? 6. What does the term glycolysis mean? 7. Glycolysis requires anaerobically. What does the term anaerobic mean? 6 S.Tagore Middletown South High School March 2013
THE KREBS CYCLE In the presence of oxygen, cell respiration continues on from glycolysis in the mitochondria of the cell. Mitochondria are ideally suited to their function in cell respiration as their inner membrane is highly folded to form cristae, presenting a large surface area for the reactions of Krebs cycle to occur. In addition, the fluid-filled interior of a mitochondrion (the matrix) is packed with the enzymes that are required for the process. The site of ATP production in the mitochondria is proved by particles on the cristae. Since mitochondria are the 'energy producing ' organelles of cells, they are present in large numbers in cells that require lots of energy, such as muscle cells, liver cells, sperm cells, and nerve cells. The events of the Krebs cycle (also known as the tricarboxylic acid cycle or the citric acid cycle) are summarised below. Pyruvic acid (produced in glycolysis) diffuses into the matrix of the mitochondrion where it is converted into a 2C carrier called acetyl coenzyme A (acetyl CoA) The conversion of pyruvic acid to acetyl CoA releases hydrogen that is bound to NAD to form NADH 2. Each acetyl CoA combines with a 4C molecule to form a 6C molecule called citric acid. 7 S.Tagore Middletown South High School March 2013
THE KREBS CYCLE During the Krebs cycle, citric acid is converted through a series of enzyme-catalysed reactions back into the 4C molecule. In the process, both carbon (in the form of carbon dioxide) and hydrogen are released. Hydrogen becomes bound to NAD to form NADH 2. This will be used in the next stage of respiration to release energy for ATP production. (In one case, the hydrogen becomes bound to a coenzyme called FAD rather than NAD.) Carbon dioxide diffuses out the cell as a waste product that is expired from the organism by breathing out or by diffusion over the body surface. 8 S.Tagore Middletown South High School March 2013
Task 4: Complete the questions that follow. Make sure that you check with your teacher to ensure you have the correct answers. 1. Complete the diagram of the Krebs cycle below using the boxes on the right of the page. Use your notes to help you. 2. The diagram below shows a mitochondrion surrounded by cytoplasm. Where does glycolysis take place? 9 S.Tagore Middletown South High School March 2013
3. In respiration, the sequence of reactions resulting in the conversion of glucose to pyruvic acid is called a. the Krebs cycle b. the citric acid cycle c. glycolysis d. the cytochrome chain. 4. The diagram below represents a summary of respiration in a mammalian muscle cell. Which box represents ATP? 5. The diagram below shows an outline of respiration in yeast cells. (a) State the location of glycolysis in yeast cells. 10 S.Tagore Middletown South High School March 2013
(b) Name one substance, other than glucose, which must be present for glycolysis to occur. (c) Name compounds R. (d) What is the name of the stage of aerobic respiration that follows on from glycolysis and where does this stage take place? Name Site (e) What is the name of the 6-carbon compound formed during the middle phase of aerobic respiration? (f) What does the term aerobic respiration refer to? (g) What is the function of the molecule NAD? 11 S.Tagore Middletown South High School March 2013
THE CYTOCHROME SYSTEM This third and final stage of aerobic respiration occurs on the stalked particles, called the cristae of the mitochondrion. Most of the energy produced during respiration is made by the cytochrome system. In this stage of aerobic respiration, the NADH 2 molecules produced during glycolysis and the Krebs cycle transfer the hydrogen ions to the cytochrome system. This is a system of hydrogen carriers located on the cristae of the mitochondrion and this stage also requires oxygen, which acts as the final hydrogen acceptor. The oxygen and the hydrogen combine to form metabolic or respiratory water. If oxygen is not present to act as the final hydrogen acceptor, the hydrogen cannot pass through the system and complete oxidation cannot take place 12 S.Tagore Middletown South High School March 2013
Task 5: Complete the questions that follow. Make sure that you check with your teacher to ensure you have the correct answers. 1. (a)the diagram shows the role of the cytochrome system in aerobic respiration. (i) State the exact location of the cytochrome system in a cell. (ii) Name the carrier that brings the hydrogen to the cytochrome system. (b) Name molecules X, Y and Z. X Y Z 13 S.Tagore Middletown South High School March 2013
2. The diagram below represents stages in aerobic respiration in mammalian liver cells. (a) Name the storage carbohydrate in liver cells. (b) Other than carbohydrate, name an alternative respiratory substrate. (c) State the exact location within a liver cell of: 1. Glycolysis 2. Krebs cycle (d) State the net gain of ATP molecules from the breakdown of a glucose molecule to pyruvic acid. 14 S.Tagore Middletown South High School March 2013
3. The pathway below represents an outline of stages in respiration in a mammalian cell. (a) Complete the table below by inserting the number of carbon atoms present in each substance. Substance Glucose Pyruvic acid Acetyl group Number of carbon atoms (b) Explain why the gain of 2ATPs in STAGE I is described as being a net gain. 15 S.Tagore Middletown South High School March 2013
(c) Name cycle X in STAGE II Name (d) Name the carrier that transfers hydrogen to the cytochrome system. Name (e) Name the final hydrogen acceptor in STAGE III. Name 16 S.Tagore Middletown South High School March 2013
ANAEROBIC RESPIRATION When anaerobic respiration occurs there is no oxygen to act as the final hydrogen acceptor and so the hydrogen cannot pass through the cytochrome system. As a result, both the Krebs cycle and the cytochrome system stages cannot take place: The only ATP produced is formed during glycolysis, that is, 2 ATP. During glycolysis, glucose is partially broken down to pyruvic acid and releases only two ATP molecules. THE FATE OF THE PYRUVIC ACID DIFFERS ACCORDING TO ORGANISM In plants and fungi, the pyruvic acid is converted to ethanol and carbon dioxide (a process also known as fermentation). In plants: pyruvic acid Ethanol (2C) + Carbon Dioxide (CO 2 ) In animals, pyruvic acid is converted to lactic acid. In animals: pyruvic acid Lactic Acid (3C) During the formation of lactic acid in animal cells, an oxygen debt accumulates that is repaid when oxygen becomes available and the lactic acid is reconverted to pyruvic acid. 17 S.Tagore Middletown South High School March 2013
SUMMARY OF ATP PRODUCTION Type of respiration Does glycolysis occur? Does the Krebs cycle occur? Does the cytochrome system occur? Total number of ATP produced per 1 glucose molecule Aerobic (oxygen present) Yes Yes Yes 36 Anaerobic (animals) (NO oxygen present) Anaerobic (plants and yeast) (NO oxygen present) Yes No No 2 Yes No No 2 18 S.Tagore Middletown South High School March 2013
Task 6: Complete the questions that follow. Make sure that you check with your teacher to ensure you have the correct answers. 1. Complete the summary of anaerobic respiration below using the boxes at the bottom of the page. Use your notes to help you. 2. Which line in the table describes correctly both aerobic respiration and anaerobic respiration in human muscle tissue? Aerobic Respiration Anaerobic Respiration A There is a net gain of ATP Carbon dioxide is not produced B There is a net gain of ATP Oxygen is required C Carbon dioxide is produced There is a net loss of ATP D Lactic acid is formed Ethanol is formed 19 S.Tagore Middletown South High School March 2013
3. During anaerobic respiration in muscle fibres what is the fate of pyruvic acid? a. It is converted to lactic acid b. It is broken down by the mitochondria c. It is broken down to carbon dioxide and water d. It is converted to citric acid 4. Three different strains of yeast each lacked a different respiratory enzyme involved in the complete breakdown of glucose. Strain X- cannot produce carbon dioxide from pyruvic acid Strain Y cannot form pyruvic acid Strain Z cannot reduce oxygen to form water Which of the strains could produce ethanol? a. Strains X and Y b. Strains X and Z c. Strain Y only d. Strain Z only 20 S.Tagore Middletown South High School March 2013
5(a) The diagram below shows the pathway of anaerobic respiration in human muscle tissue. Glucose Process X Pyruvic acid Compound S Name Process X and Compound S. Process X Compound S (b) Complete the boxes in the diagram to show the number of carbon atoms present in glucose and pyruvic acid. (c) Aerobic respiration in human muscle tissue involves the Krebs cycle and the cytochrome system. For each statement in the table below, tick ( ) a box to show the process to which it applies. Statement Krebs cycle Cytochrome system Carbon dioxide is produced Occurs on the cristae of the mitochondria Involves the formation of NADH 2 Involves the formation of citric acid 21 S.Tagore Middletown South High School March 2013
6. The diagram shows a mitochondrion from a human muscle cell. (a) Name regions A and B. A B (b) The table shows some substances involved in respiration. (i) Complete the table by inserting the number of carbon atoms present in each substance. Substance Pyruvic acid Acetyl group Citric acid Number of carbon atoms present (ii) To which substance is the acetyl group attached before it enters the citric acid cycle? (c) In region B, hydrogen is passed through a series of carriers in the cytochrome system as shown in the diagram below. (i) Name carrier X. 22 S.Tagore Middletown South High School March 2013
(ii) Name the final acceptor of hydrogen. (iii) Describe the importance of ATP cells. (iv) The quantity of ATP present in the human body remains relatively constant yet ATP is continually being broken down. Suggest an explanation for this observation. (v) Name the final metabolic product of anaerobic respiration in a muscle cell. 23 S.Tagore Middletown South High School March 2013
Task 7: Your teacher will assess your knowledge of the following key terms. Make sure you understand what these words mean. Adenosine Triphosphate (ATP) Supplies chemical energy for cellular processes Respiration A chemical process in which energy is released from food molecules in cells Glucose The cell s main energy source Aerobic respiration The process by which energy is released from glucose in cells using oxygen Anaerobic respiration The process by which some energy is released from glucose in cells in the absence of oxygen Pyruvic acid Formed as a result of the first stage of the respiration of glucose Glycolysis Stage of respiration that occurs in the cytoplasm and does not require oxygen Krebs cycle Cytochrome system Stage of respiration that occurs in the matrix of the mitochondria and does require oxygen Also known as the electron transport chain. The stage of aerobic respiration where the majority of ATP are synthesised from ADP and Pi Oxygen The final hydrogen acceptor Carbon dioxide and ethanol The products of anaerobic respiration in plants and yeast cells 24 S.Tagore Middletown South High School March 2013
Lactic Acid The product of anaerobic respiration in animals. This can be reversed when oxygen is present. Oxygen debt The build up of lactic acid causes this 25 S.Tagore Middletown South High School March 2013