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Chemistry of Life Essential elements and water Elements of living things • Every living thing is made of – atoms are the smallest part of an element – Atoms of different elements group together to form – If an atom loses or gains an electron it becomes charged = – 99% of living matter consists of four elements – Carbohydrates: carbon, oxygen, hydrogen – Lipids: carbon, oxygen, hydrogen – Proteins: consist of amino acids that contain carbon, oxygen, hydrogen and nitrogen Roles of essential elements Element Plants Animals Prokaryotes • In some amino acids • In some amino acids • • Trace elements also existandinproteins the body and proteins Sulphur Calcium • • Cell wall formation between dividing plants Co-factor for certain enzymes • • • In bone Reacts in muscle fiber contraction Cofactor for certain enzymes • • In some amino acids and proteins Helps with heat resistance in of bacterial endospores Co-factor in certain enzymes Phosphorus • Phosphate groups in ATP Phosphate groups in ATP Phosphate groups in ATP Iron • In cytochromes – electron transport molecule • In cytochromes and hemoglobin In cytochromes Sodium • Sodium potassium • pump – part of transporting • molecules across the cell membrane Sodium potassium pump – Sending nerve impulses • Sodium potassium pump to transport molecules Water is an important molecule for life • Plants = 65 – 95% water • Animals = 80% water Water Molecule • Unique structure that gives water some interesting characteristics • Consists of two hydrogen atoms and one oxygen atom • – they share valence electrons • Hydrogen atoms spend most of their time around • Hydrogen atoms are offset giving one side of the molecule a slight charge and the other side the opposite charge – it is a molecule *Annotate the diagram to show which end is positive and negative • Water forms hydrogen bonds – an attraction to other positive and negative charges – Weak bond *Hydrogen bonds give water unique properties Thermal Properties • Water has high specific heat – A lot of heat energy is needed to raise the temperature of water • Temperature is the measure of how quickly molecules are moving in a substance • Hydrogen bonds must be broken before water molecules can move faster • Lakes and ponds don’t change temperature quickly • Hydrogen bonds keep water from vaporizing Evaporation and (evaporating) easily Heat Loss – When organisms evaporate water (transpiration or sweating), heat energy is transferred to the water molecule and carried off in water vapor, cooling the organism Heat Energy and Freezing • A lot of heat energy must be removed from water to turn it to ice • Water in the environment and in cells are Density of Ice • Ice is less dense than water: different from all other materials – Insulates freezing lakes and allows life to thrive under the surface in freezing temps. Cohesive and Adhesive Properties • Cohesion: water sticks to itself through hydrogen bonds – Responsible for surface tension • Adhesion: water sticks to other charged surfaces through • Water can climb narrow tubes necessary to bring water to the uppermost limbs of plants Solvent Properties • Water is a powerful solvent of polar substances – Ionic substances like sodium chloride (Na+Cl-) – Organic molecules (carbon containing molecules that are found in living things) that have ionized (charged) groups Transparency • Water is transparent • Light can penetrate water allowing aquatic photosynthetic plants