Bioenergetics

1. Bioenergetics Introduction to Bioenergetics

2. Next Topics: Biology, Bioenergetics, Biomechanics • In this lecture block we will look in more detail at biological processes and understand how the biological systems use food (fuel) and convert it into useful work. • To understand the processes involved, we will cover topics including: • Cell structure and function • Energy and energy usage in the context of biological systems (Bioenergetics) • Biotechnology • Biomechanics

3. Comparison between mechanical and biological work • The aim of this exercise is to identify some key differences between the way in which man-made process use fuel to drive a mechanical movement and the way biological systems do this. • Calculate the energy required to fly from Auckland to Wellington and compare it to the energy required if cycling. • Is mechanical work more efficient than biological work?

4. Data for the calculations • Distance: 658 km By Air: • Airbus, A320, 128 passengers • 3,500kgof jet fuel AKL-WGN • Jet Fuel; energy value = 36.8 x106J/litre; density = 0.802 kg/litre. By Bicycle: • Average Energy required, 80 kg person: • 2,000 kJ/hour cycling moderately • 292 kJ/hour resting • Assume it will take 4 days and 3 nights to cycle, cycling for 8 hours during each day.

5. Beyond the call of duty

6. Garmin Rimutaka hill 28 hrs cycling

7. Data for the calculations • Distance: 658 km By Air: • Airbus, A320, 128 passengers • 3,500kgof jet fuel AKL-WGN • Jet Fuel; energy value = 36.8 x106J/litre; density = 0.802 kg/litre. By Bicycle: • Average Energy required, 80 kg person: • 2,000 kJ/hour cycling • 292 kJ/hour resting • Assume it will take 7 days, cycling for 4 hours each day.

8. Calculation of energy to fly (mechanical)

9. Calculation of energy to cycle (biological)

10. Comparison between flying and cycling • Flying • Fast • Less efficient conversion of chemical energy into work • High Temperatures • Uncontrolled combustion reactions • Cycling • Slow • More efficient conversion of chemical energy into work • Low Temperatures • Controlled series of complex reactions to convert glucose into CO2 and H20

11. 1. 2. 3. Net Reaction: C6H12O6 + 6 O2→ 6 CO2 + 6H2O

12. Handout: Intro to Biological Molecules In order to understand the workings of cells and therefore living things, a knowledge of the molecules found in cells will be useful. The four main categories of biological molecules are: • Carbohydrates • Lipids • Proteins • Nucleic Acids A handout with information on each of these types of molecules is available on CECIL.

13. Unifying principles of biology • Biological organisms are made up of cells • Biological organisms obey the laws of physics and chemistry • Biological organisms require energy for life, and are able to convert energy from one form to another.

14. Introduction to cells CELLS ARE THE FUNDAMENTAL FUNCTIONING UNITS OF ALL LIVING THINGS. EVERY SINGLE THING THAT YOU DO IS DUE TO PROCESSES OCCURRING AT THE CELLULAR LEVEL. As humans we are made up of trillions of cells with different specialised roles within the body. The white blood cell on this slide is part of your immune system - in contrast to muscle cells which move your limbs. Some organisms, such as bacteria, function as just one cell.

15. Seeing cells The invention of MICROSCOPES was essential to providing an understanding of cells. 1665: First cell described by Robert Hooke when examining cork under a microscope. 1800’s: All organisms under the microscope had cells = CELL THEORY (all living things are made up of cells). 1950’s: Electron Microscopes reveal the parts of cells.

16. The size of cells The logarithmic scale to the left of the diagram places the following biological structures according to size: • Bacteria • Molecules • Plant & animal cells • Viruses • Some nerve cells • Atoms

17. The two types of cells All the cells that are found in all the organisms on Earth can be placed in one of two categories: • PROKARYOTIC CELLS • Bacteria • EUKARYOTIC CELLS • Plants • Animals • Fungi • Protists (everything else!)

18. Contrasting prokaryotic and eukaryotic cells

19. Eukaryotic cells – plant and animal cells We will focus on general animal (and plant) cells and become familiar with the major parts of these cells and their functions. • Both plant and animal cells have a thin outer layer called the PLASMA MEMBRANE. • (Plant cells also have a thicker CELL WALL) • Eukaryotic cells have an obvious NUCLEUS that contains the cell’s genetic material (DNA). • The region between the nucleus and plasma membrane is called the CYTOPLASM and is made up of a fluid called CYTOSOL. The parts of cell called ORGANELLES are found suspended in the cytosol.

20. The plasma membrane GENERAL FUNCTION: The plasma membrane separates the living cell from its non-living environment. Even though the membrane is only 7 to 9 nm thick, it controls the passage of chemicals into and out of the cell. GENERAL STRUCTURE: The plasma membrane and other membranes are made up of mostly lipids (fats) and proteins. The lipids have a phosphate group attached and are therefore called phospholipids. The phospholipids form a double layer called the PHOSPHOLIPID BILAYER.

21. Outside Cell Cytoplasm (Inside Cell) The phospholipid bilayer The phospholipids and proteins are free to drift within the membrane: “fluid mosaic model”

22. Functions of membrane proteins

23. Permeability of membrane Plasma membranes are selectively permeable. This means that some substances can pass into and out of the cell easily while the passage of other substances is blocked. For example: • Oxygen can pass freely into the cell and carbon dioxide out of the cell through the membrane. • Glucose can only be transported into the cell using a transport protein.

24. The Nucleus The nucleus contains DNA which provides the code to make proteins. Proteins do most of the work of the cell. (This will be gone into in greater detail in subsequent lectures.) STRUCTURE AND FUNCTION: • Nuclear envelope – double membrane enclosing nucleus • Chromatin – long DNA molecules plus proteins • Ribosomes – small dots for making proteins

25. The Nucleus

26. Mitochondria MITOCHONDRIA are the organelles in which food is converted into chemical energy. This process, called RESPIRATION will be covered in detail in later lectures. The higher the energy requirements of a cell, the more mitochondria – a heart muscle cell has many large mitochondria.

27. Bioenergetics The Working Cell Introduction to Bioenergetics

28. Plasma Membrane Cytoplasm Eukaryotic cells

29. Introduction to the Working Cell We are familiar with the various parts or ORGANELLES of the cell. We now need to cover some of the processes that occur within cells that are necessary for life. Two general processes will be covered in the next two lectures: • The energy driving cellular work • Enzyme activity

30. Energy Energy is required to make a cell work just as it is required for the working of a car. DEFINITION: Energy can be defined as the capacity to do work. Work has occurred when an object has been moved against an opposing force. CONSERVATION OF ENERGY: It is not possible to create or destroy energy; energy can only be converted from one form to another.

31. HEAT HEAT Conversions of Energy

32. Chemical Energy Question: Where does a working cell get its energy? Answer: The energy-rich structures of carbohydrates and fats provide energy to cells in the form of CHEMICAL ENERGY. Question: What is the process called whereby cells harvest this chemical energy from food molecules? Answer: CELLULAR RESPIRATION in the MITOCHONDRIA of cells is the process whereby food molecules are broken down to release energy.

33. Mitochondria MITOCHONDRIA are the organelles in which food is converted into chemical energy in a process called RESPIRATION. .

34. Food Energy Energy Content (kJ) 1500 1275 1090 757 700 605 525 502 234 184 130 Energy (kJ) consumed per hour by a 70kg person* 3620 2505 2240 2150 845 711 660 305 255 117

35. Example • Estimate how high a ladder could a 70kg person climb fuelled by a Cadbury Moro bar. • assume muscle is 24% efficient • nutritional content of a 65g moro bar is: • 10g fat, 45g sugar, 3g protein • energy content of • Fat: 39 kJ/g • Glucose: 16 kJ/g • Protein: 18 kJ/g • you can assume acceleration due to gravity is 9.8m/s2

36. Example, cont’d • Calculation: • Energy in moro bar: • 10g x 39kJ/g + 45g x 16kJ/g + 3 x 18kJ/g = 1164 kJ • Energy required to climb 1 metre: • Force = 70kg x 9.8m/s2 = 686N • Work done to climb 1m = 686 x 1 = 686J • Energy expended at 24% efficiency = 686/0.24 = 2860J • Total 1m climbs possible: • 1164 kJ / 2.86 kJ = 407m

37. Heat Energy Heat Energy Cellular Work Cellular Respiration About 40% of the chemical energy harnessed from food molecules is used for cellular work and the rest generates body heat. Cellular respiration will be covered in detail in subsequent lectures.

38. Thermodynamics of Biological Systems • Biological systems exchange heat and matter with their surroundings • open systems • Biological systems operate under conditions of • constant temperature (37°C) • constant pressure (1 atm)

39. Thermodynamics of Biological Systems • Under what conditions does a biochemical reaction occur spontaneously? Reminder: Enthalpy change ΔH is the maximum amount of thermal energy that can be released for the reaction at constant pressure • Does ΔH tell us if a reaction will go? Reminder: ΔU = Ufinal – Uinitial = q + w • ΔH < 0: exothermic reactions release heat • ΔH > 0: endothermic reactions absorb heat • But some endothermic reactions are spontaneous, so ΔH is not sufficient to determine whether a reaction will go.

40. Thermodynamics of Biological Systems • Consider a gas released into a vacuum: • the gas spontaneously expands into the volume, while the total energy is unchanged • but the disorder of the system increases • Consider a block of ice melting at room temperature: • A spontaneous, but endothermic process (heat is removed from surrounding air) • liquid water is more disordered than solid ice ‘Entropy’ is a measure of how disordered a system is

41. Gibbs Free Energy • For processes occurring at constant temperature T and pressure, we combine the Enthalpy change ΔH and the Entropy change ΔS in the Gibbs Free Energy change ΔG = ΔH – TΔS ΔG ≤ 0 for a spontaneously occurring reaction at constant temperature and pressure • Gibbs Free Energy is the ‘potential energy’ for biochemical reactions • Reactions with ΔG ≤ 0 (‘exergonic’) occur spontaneously • Reactions with ΔG > 0 (‘endergonic’) must be driven by input of free energy

42. Gibbs Free Energy • Some biologically important reactions are exergonic: e.g. combustion of glucose C6H12O6 + 6O2→ 6CO2 + 6H2O ΔH = −2808 kJ/mol ΔG = −2862 kJ/mol i.e. increase in entropy provides 54 kJ/mol free energy • Some are endergonic: e.g. two simple (monosaccharide) sugars are combined in the sugar cane plant to produce a disaccharide sugar glucose + fructose → sucrose + H2O ΔG = +23 kJ/mol

43. ATP – The Energy Currency Endergonic reactions must have energy supplied in order for them to take place. The chemical energy stored in the structures of carbohydrate and fat molecules must be released to supply working cells. Carbohydrates and fats can not directly supply energy to the cell. The process of cellular respiration breaks down these molecules releasing their energy by making the energy carrier ATP. ATP (adenosine triphosphate) molecules directly provide the working cell with energy.

44. The phosphate groups are the energy supplying part of the molecule. When a phosphate group is released the free energy can be used to drive endergonic reactions. This leaves behind ADP or adenosine diphosphate. ADENOSINE P P ATP – The Energy Currency STRUCTURE: ATP consists of the organic compound adenosine with three phosphate groups attached. ADENOSINE P P P

45. Coupled Reactions • The splitting (hydrolysis) of ATP is exergonic ATP + H2O → ADP + phosphate ΔG= −29 kJ/mol • Cells power reactions with ΔG > 0 by coupling them to the hydrolysis of ATP e.g. in the sugar cane plant, the overall reaction in which two monosaccharides are combined to form the disaccharide sucrose is glucose + fructose → sucrose + H2O ΔG = +23 kJ/mol • The free energy change for coupled reactions is found by adding the free energy change for the individual reactions glucose + fructose + 2 ATP → sucrose + 2 ADP + 2 phosphate + 2×(−29 kJ/mol) = −35 kJ/mol We will now look at the molecule ATP in more detail

46. ATP and ADP When ATP energises other molecules in a cell the phosphate group is transferred to those molecules. The phosphate transfer assists the cell in three main types of work: • Mechanical work • Transport Work • Chemical Work

47. ATP Driving Cellular Work

48. The ATP Cycle Cells are constantly using ATP. Cellular respiration is constantly making new supplies of ATP to be used during cellular work. The ATP Cycle: A working muscle cell consumes and regenerates about 10 million ATP molecules every second. The average human recycles 100-150 moles of ATP daily, which is around 50-75 kg!

49. Bioenergetics The Working Cell Enzyme Kinetics

50. Overview • In the previous lecture we discussed the thermodynamics of biochemical reactions. Thermodynamics can be used to show whether a reaction occurs spontaneously. However, it does not tell us how fast it occurs. • The field that investigates the rates of reactions is called chemical kinetics. In this lecture we will consider factors which affect the rate of a reaction, and how cells increase the rate of cellular reactions. • In contrast to many man-made processes, in particular combustion processes, biochemical reactions are typically: • slow • energetically efficient • highly controlled – Enzyme Catalysis