TOPIC 3 March 2013
Chemical Elements and Water Edition
The most frequently occurring elements in living things are actually Carbon, Hydrogen, Oxygen, and Nitrogen
A VARIETY OF OTHER ELEMENTS ARE NEEDED BY LIVING ORGANISM LIKE: Sulfur, Calcium, Iron, Phosphorous, and Sodium
Sulfur is found in some amino acids. It
takes part in photosynthesis. Iron binds
is also the reactant for chemosynthetic
well with oxygen for transport. It also
bacteria (chemoautotrophs)- found in
facilitates the movement of electron in
cells, including bacteria.
Calcium is essential in many species.
Phosphorus is essential in the
It is used in the structure of bones and
formation of the phospholipid bilayer:
teeth in animals, as well as in blood
hydrophilic phosphate heads attract water
clotting. Carbon carbonate (CaCO3) is
and hydrophobic hydrocarbon tails repel
used in the production of exoskeletons in
water. Phosphates are also the active
animals and unicellular organisms. Calcium
components in ATP molecules and make
ions (Ca2+) are essential in synaptic
up the â€˜backboneâ€™ of DNA.
transmission. Iron is an important micronutrient in
Sodium is essential in generating an action potential for nerve impulses
living things. In animals, it is the oxygenbinding component of hemoglobin. In plants, it is used to make chlorophyll and
Covalent bonds connect oxygen and hydrogen molecules in individual molecules
Hydrogen bonds are the attractions between polar molecules.
OXYGEN OXYGEN EXERTS A GREATER PULL OVER THE SHARED ELECTRONS. THEY MOVE A LITTLE CLOSER TO THE OXYGEN.THIS 
MEANS THAT OXYGEN IS OVERALL SLIGHTLY NEGATICE. THE HYDROGEN END IS OVERALL SLIGHTLY POSITIVE.
WATER IS THE UNIVERSAL SOLVENT
Thermal, Cohesive, and Solvent Properties of Water A single hydrogen bond is not very strong. A large number of hydrogen bonds is very strong. Each water molecule bonds with four others in a tetrahedral arrangement: because of these hydrogen bonds water is cohesive; the molecules of water stick to each other. Water is also adhesive, so it will stick to other surfaces. These properties lead to capillary actions, which means that water will move up xylem against gravity. Surface tension: the surface of water is strong enough to support insects and cause drops to form. Water has a high specific heat capacity. This means it takes a lot of energy for the temperature of water to change. This is a result of the many hydrogen bonds. This all means that the temperature of water remains relatively stable. Most organisms are adapted to a narrow range of conditions. The slow heating and cooling of water are ideal for these organismthere is less risk of extreme changes. Water cab be stable habitat. Because it takes a lot of energy to make water evaporate, it makes a good coolant- evaporating water removes a lot
of heat energy from organisms. High temperatures damage tissues and denature proteins causing enzymes to cease working. When water evaporates, it removes a lot of energy from the system, and this is felt as a cooling sensation. This also helps aquatic habitats remain at fairly constant temperatures in hot summers. Water is good solvent is because it is a polar molecule. It will dissolve polar solutes easily. Ionic solids dissociate in water. Polar attractions cause water molecules to surround and isolate the solute molecules. Because water is such a good solvent, it is a medium for metabolic reactions. Dissolved particles are able to move around- and diffuse. All metabolic reactions occur in a solution. Membranes and biological surfaces are wet. This allows molecules to dissolve, including gases, so they can diffuse through more easily. Water dissolves nutrients, gases, and wast products.
Organic vs. Inorganic
PROTEINS, LIPIDS, AND CARBOHYDRATES
Compounds containing carbon that are found in living organisms (except hydrogen carbonates, carbonates and oxides of carbon) are regarded as organic. Examples: CO, CO2, HCO3, Na2HCO3, CO32-, CaCO3, Na2CO3.
Condensation and Hydrolysis
MONO, DI, AND POLYSACCHARIDES
Condensation makes bonds by releasing water and hydrolysis breaks bonds by splitting water. Condensation you join two to make one and in hydrolysis you break one into two.
Functions : In animals Glucose: small and easily absorbed sugars, fast release for respiration Lactose: found in milk; ideal for nursing young Glycogen: insoluble storage molecule: excess sugars converted by insulin for storage in the liver
Functions: In animals Fructose: easily absorbed sugars- fast release for respiration Sucrose: soluble but unreactive, so it can be transported around the plant in the phloem Cellulose: large and insoluble makes the plant cell wall
CARBOHYDRATES VS. LIPIDS IN ENERGY STORAGE Carbohydrates and lipids can both be used as energy storage however carbohydrates are usually used for short term storage whereas lipids are used for long term storage. Carbohydrates are soluble in water unlike lipids. This makes carbohydrates easy to transport around the body (from and to the store). Also, carbohydrates are a lot easier and more rapidly digested so their energy is useful if the body requires energy fast. As for lipids, they are insoluble which makes them more difficult to transport however because they are insoluble, lipids do not have an effect on osmosis which prevents problems within the cells in the body. They also contain more energy
per gram than carbohydrates which makes lipids a lighter store Carbohydrates: 17 compared to a kJ g-1 store of Fats: 38 kJ g-1 carbohydrates equivalent in energy. Lipids need more oxygen to release energy. Carbohydrates: 17 kJ g-1 Fats: 38 kJ g-1
FUNCTIONS OF LIPIDS
Lipids can be used for energy storage in the form of fat in humans and oil in plants. Lipids can be used as heat insulation as
fat under the skin reduces heat loss. Lipids allow buoyancy as they are less dense than water and so animals can float in water.