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Option B. Human Biochemistry B.1. all living things require the input of energy to exist – this energy is used to drive the thousands of biochemical reactions.

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Presentation on theme: "Option B. Human Biochemistry B.1. all living things require the input of energy to exist – this energy is used to drive the thousands of biochemical reactions."— Presentation transcript:

1 Option B. Human Biochemistry B.1

2 all living things require the input of energy to exist – this energy is used to drive the thousands of biochemical reactions that occur to allow the organism to grow, reproduce and sustain life – this energy comes almost always from the Sun, in the first instance – energy from sunlight is captured by photosynthetic organisms (e.g. plants, algae, certain bacteria) and converted into carbohydrates. these are then broken down by a process called cellular respiration, to produce energy-rich molecules (e.g. adenosine triphosphate, or ATP) that release energy to drive biochemical reactions. – photosynthetic organisms can by ingested by nonphotosynthetic animals, and the carbohydrates (and other biomolecules) can be broken down and used for cellular respiration – in general an average man requires about 10,500 kilojoules (2500 kilocalories) per day, while an average woman needs approximately 8400kJ (2000 kcal) per day Introduction

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5 a food (or bomb) calorimeter can be used, which measures the heat of combustion a known mass of a particular food is ignited and completely burnt in the presence of oxygen. Energy value of food using enthalpy of combustion data

6 energy contained in the food can be calculated using the following equation: q = mcΔT – q = heat evolved (J) – m = mass of water (g) – c = specific heat capacity of water (4.18 J g −1 K −1 or 4.18 J g −1 °C −1 ) – Δ T = temperature change of the water (in °C or K)

7 Worked example When 1.00 g of tomato soup was burnt in a food calorimeter containing 100 g water, it raised the temperature of the water from 20.4 °C to 28.0 °C. Calculate the energy content of 100 g of tomato soup. – q = mcΔT m = 100 g of water c = 4.18 J g −1 K −1 ΔT = 7.6 °C – therefore: q = 100 × 4.18 × 7.6 = J or 3.18 kJ – so, in 100 g of tomato soup… there will be 3.18 kJ(100g) of tomato soup = 318 kJ


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