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Topic 3: The Chemistry of Life

Topic 3: The Chemistry of Life. Introduction. Organic Chemistry is the chemistry of carbon compound Biochemistry is the branch of organic chemistry which attempts to explain the chemistry in living organisms Four main types of organic molecule Carbohydrates Lipids Proteins Nucleic acids.

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Topic 3: The Chemistry of Life

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  1. Topic 3: The Chemistry of Life

  2. Introduction • Organic Chemistry is the chemistry of carbon compound • Biochemistry is the branch of organic chemistry which attempts to explain the chemistry in living organisms • Four main types of organic molecule • Carbohydrates • Lipids • Proteins • Nucleic acids

  3. Topic 3.1: Chemical elements and water • Assessment statements: • 3.1.1 states that the most frequently occurring chemical elements in living things are carbon, hydrogen, oxygen and nitrogen • 3.1.2 state that a variety of other elements are needed by living organisms, including sulfur, calcium, phosphorus, iron, and sodium • 3.1.3 state one role for each of the elements mentioned in 3.1.2 • 3.1.4 draw and label water molecules to show their polarity and hydrogen bond formation • 3.1.5 outline the thermal, cohesive, and solvent properties of water • 3.1.6 explain the relationship between the properties of water and its uses in living organisms as a coolant, medium for metabolic reactions and transport medium

  4. Elements found in living organisms • Four most common elements found in living things • Carbon, hydrogen, oxygen and nitrogen • These elements are used in the molecular structures of all carbohydrates, proteins, lipids and nucleic acids

  5. Elements found in living organisms

  6. H H Structure of water • Water is the solvent of life • Virtually all cells have water within (cytoplasm) and water in the surrounding environment (intercellular fluid, pond water, etc) • Water is an incredibly abundant substances on Earth and has very interesting properties • Many of these properties depend on the structure of water molecules

  7. Structure of water • The hydrogen and oxygen atoms in a single water molecule are held together by a type of bond called a polar covalent bond • Polar covalent bond results from an unequal sharing of electrons • Results in a slight negative charge at the oxygen end and a slight positive charge at the end of the two hydrogen • Because the two ends of each water molecule have opposite charges, water molecules interact with each other

  8. Properties of water and living organisms • Thermal Properties • High specific heat • This means that water can absorb or give off a great deal of heat without changing temperature greatly • High heat of vaporization • This means that water absorbs a great deal of heat when it evaporates

  9. Properties of water and living organisms • Cohesive Properties • Water molecules are highly cohesive • Is when molecules of the same type are attracted to each other • The attraction is due to the polar covalent bonding • When water cools below the freezing point, molecular motion has slowed to the point where these polar attractions become locked into place and an ice crystal forms

  10. Properties of water and living organisms • This cohesion between liquid water molecules explains a variety of events, including • Why water forms into droplets when spilled • Why water has a surface tension that allows some organisms to ‘walk on water’ • How water is able to move as a column in the vascular tissues of plants • Why water has a high heat capacity and high heat of vaporization

  11. Properties of water and living organisms • Solvent Properties • Water is an excellent solvent of other polar molecules • ‘like dissolves like’ • Most molecules typically found inside and outside of most cells are also polar molecules • Most types of lipids are relatively non-polar

  12. Properties of water and living organisms • Examples of eater as a solvent in plants and animals • Properties of eater makes it an excellent medium for transport • Vascular tissue in plants carries water and a variety of dissolved substances • Xylem carries water and dissolved minerals up from the root system to the leaves of a plant • Phloem then transports dissolved sugars from the leaves to the stems, roots, and flowers of a plant

  13. Properties of water and living organisms • Blood is the most common transport medium in animals and is largely made up of water • Transport medium for red blood cells, white blood cells, platelets, and a wide variety of dissolved molecules • The liquid portion of blood is blood plasma • Some of the more common solutes in blood plasma are • Glucose (blood sugar) • Amino acids • Fibrinogen (protein involved in blood clotting) • Hydrogencarbonate ions (as a means of transporting CO2)

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