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Topic 3.1, 3.2, 7.5: Water, Carbs , Lipids and Proteins

Topic 3.1, 3.2, 7.5: Water, Carbs , Lipids and Proteins. IB BIOLOGY. Elements. Atoms form molecules/compounds Bonds: covalent (atoms share electrons) or ionic (atoms give/receive electrons). H - Hydrogen. C - Carbon. Na - Sodium. Sodium Chloride. Cl - Chlorine. Ions. Methane.

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Topic 3.1, 3.2, 7.5: Water, Carbs , Lipids and Proteins

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  1. Topic 3.1, 3.2, 7.5: Water, Carbs, Lipids and Proteins IB BIOLOGY

  2. Elements • Atoms form molecules/compounds • Bonds: covalent (atoms share electrons) or ionic (atoms give/receive electrons). H - Hydrogen C - Carbon Na - Sodium Sodium Chloride Cl - Chlorine Ions Methane

  3. Elements / Minerals • Most frequent elements: Carbon, Hydrogen, Oxygen and Nitrogen • Other elements: - Sulfur (S): proteins/enzymes, plant growth - Calcium (Ca): teeth, bones, cell wall component, muscle and nerve function - Sodium (Na+): water balance (osmoregulation), muscle contraction, nervous impulse - Potassium (K+): nervous impulse - Iodine (I): thyroid hormones - Phosphorus (P): plant growth, bones/teeth, nucleic acids - Iron (Fe): needed for chlorophyll formation /photosynthesis, red blood cells (hemoglobin)

  4. Water and its properties • POLAR = Oxygen attracts electrons more strongly

  5. Hydrogen Bonds • The water molecules attract each other • Hydrogen bonds form (not real bond – strong attraction force)

  6. Water properties • Transparent: allows plants/algae to survive under water • Strong cohesion forces (polar molecule) = high surface tension (force between molecules at surface) = insects can walk on it/water goes from roots to leaves • Good solvent for polar molecules = good transport medium (ex. blood, plants) + medium for chemical reactions

  7. Water properties • Thermal properties (due to high specific heat, heat of fusion/vaporization) Consequences: 1) can absorb larger amounts of energy and still remain liquid. Ex: large body of water can act as a buffer 2) coolant effect = water absorbs large amounts of heat and cools the body (sweat) • Ice floats, protecting the water below from freezing, allowing organisms to survive

  8. Organic and Inorganic Compounds • Organic = all molecules containing carbon found in living systems exceptions: CO2 and carbonates (salt of carbonic acid - CO32− - ex: calcium carbonate and carbonated water) Main organic substances (macromolecules): • Carbohydrates • Lipids • Proteins • Nucleic Acids • Inorganic = all substances that are not organic

  9. Carbohydrates • Most abundant • Short term energy storage • General molecular formula (CH2O)n • Basic unit: monosaccharides (fructose, glucose, galactose) • Two monosaccharides: disaccharides (maltose, lactose, sucrose) • Anything larger than this: polysaccharides (starch, glycogen, cellulose)

  10. Monosaccharides • Glucose: one of main products of photosynthesis, starts cellular respiration - cell uses it as a source of energy • Galactose: sugar in milk • Fructose: sugar found in honey, fruits, vegetables • Ribose/Deoxyribose: RNA/DNA structure

  11. Disaccharides • Sucrose — common table sugar = glucose + fructose • Lactose — major sugar in milk = glucose + galactose • Maltose — product of starch digestion = glucose + glucose

  12. Polysaccharides • Starches: plant storage (excess glucose) - before starches can enter (or leave) cells, they must be digested. The hydrolysis of starch is done by an enzyme called amylase. • Glycogen: animals storage (excess glucose). -The liver and skeletal muscle are major deposits of glycogen. • Cellulose: plant structure (cell wall). Probably the single most abundant organic molecule in the biosphere. (fibers – paper, cotton) Starch grains in potato cells Cellulose fibers

  13. Condensation/Hydrolysis • Condensation: 2 molecules are joined together + loss of 1 water molecule • Hydrolysis: water helps break two units (monomers)

  14. Lipids/Fats • Glycerol + fatty acid chains • Large number of C - H bonds = non-polar molecules. • Insoluble in water • Functions: • Long term energy storage • Thermal insulation (Arctic animals) • Major component of the cell membrane The fatty "tail" is non-polar (Hydrophobic) The phosphate "head" is a polar (Hydrophilic) phospholipid

  15. Fats • Saturated: full of hydrogens – solid at room temperature • Unsaturated: one or more double bonds connecting carbons – liquid at room temperature

  16. Fats • Cis – Trans • Oil for frying causes some of the cis bonds to convert to trans bonds. Fatty acids with trans bonds are carcinogenic. • All steroids (testosterone, estrogen, progesterone, cortisone…) and Vitamin D need cholesterol to be made. • Cholesterol = controls how fluid the cell membrane will be

  17. Energy content • Animals use fats for energy storage • Fat stores lots of calories in a small space - 9Kca/g - against carbs (4Kcal/g)

  18. Proteins • Made of amino acids • Contain nitrogen • Many functions: • Structural (muscles, collagen, keratin) • Enzymes (metabolism) • Carriers (hemoglobin, albumin) • Antibodies • Hormones (ex. insulin) • Membrane pumps (ATP pumps), receptors, neurotransmitters • Movement (actin, myosin)

  19. Peptide Bond • peptide bond = joins two amino acids

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