CHEMICAL ELEMENTS & WATER Topic 3.1 IB Biology Miss Werba

CARBS, LIPIDS & PROTEINS 3.5 TRANSCRIPTION & TRANSLATION TOPIC 3 - BIOCHEMISTRY 3.1 ELEMENTS & WATER 3.2 CARBS, LIPIDS & PROTEINS 3.3 DNA STRUCTURE 3.4 DNA REPLICATION 3.5 TRANSCRIPTION & TRANSLATION 3.6 ENZYMES 3.7 CELL RESPIRATION 3.8 PHOTOSYNTHESIS J WERBA – IB BIOLOGY 2

THINGS TO COVER Common chemical elements in living things Structure of water molecules Properties of water Uses of water in living organisms J WERBA – IB BIOLOGY 3

CHEMISTRY REVISION Elements are pure substances that cannot be broken down any further Elements are made up of atoms Some elements exist as molecules – eg. H2, O2 Two or more different atoms can also combine to form molecules – eg. H2O Molecules come together to make compounds J WERBA – IB BIOLOGY 4

CHEMISTRY REVISION Protons Neutrons Electrons Positive charge In the nucleus Neutrons No charge In the nucleus Electrons Negative charge Orbit the nucleus J WERBA – IB BIOLOGY 5

CHEMISTRY REVISION Covalent bonds: atoms share electrons Ionic bonds: where electrons are transferred from one atom to another, forming positively or negatively ions J WERBA – IB BIOLOGY 6

CHEMISTRY REVISION In biological systems, atoms combine by forming covalent bonds Hydrogen (H): forms 1 covalent bond with other atoms Oxygen (O): usually forms 2 covalent bonds with other atoms Carbon (C): - forms 4 covalent bonds with other atoms - also capable of forming long chains with other carbon atoms Nitrogen (N): forms 3 covalent bonds with other atoms J WERBA – IB BIOLOGY 7

CHEMICAL ELEMENTS IN LIVING THINGS Command term = STATE 3.1.1 CHEMICAL ELEMENTS IN LIVING THINGS Command term = STATE The most frequently occurring chemical elements in living things are: Carbon (19%) Hydrogen (10%) Oxygen (65%) Nitrogen (3%) CHON J WERBA – IB BIOLOGY 8

CHEMICAL ELEMENTS IN LIVING THINGS Command term = STATE 3.1.2 CHEMICAL ELEMENTS IN LIVING THINGS Command term = STATE A variety of other elements are also needed by living organisms: Remember: CaFe NaPS Ca – Calcium Fe – Iron Na – Sodium P – Phosphorus S – Sulfur CaFe NaPS J WERBA – IB BIOLOGY 9

CHEMICAL ELEMENTS IN LIVING THINGS Command term = STATE 3.1.3 CHEMICAL ELEMENTS IN LIVING THINGS Command term = STATE A variety of other elements are also needed by living organisms : Ca – calcium – strengthens bones & teeth, enables muscle contraction, vesicle release in neurons Fe – iron – needed to make haemoglobin and transport oxygen, needed to make chlorophyll J WERBA – IB BIOLOGY 10

CHEMICAL ELEMENTS IN LIVING THINGS Command term = STATE 3.1.3 CHEMICAL ELEMENTS IN LIVING THINGS Command term = STATE A variety of other elements are also needed by living organisms : Na – sodium – used in neuron transmission, needed in osmoregulation, used in transport of glucose across membrane P – phosphorus – part of phospholipids, part of nucleotides, part of some sugars S – sulfur – found in two amino acids, helps form tertiary structure in proteins by forming disulphide bonds J WERBA – IB BIOLOGY 11

STRUCTURE OF WATER Chemical formula: H20 Made up of hydrogen & oxygen 3.1.4 STRUCTURE OF WATER δ – δ + Chemical formula: H20 Made up of hydrogen & oxygen Covalent bonds exist between the atoms Oxygen nucleus is larger & more charged than the hydrogen nuclei. This pulls the electron pair in the covalent bond 'closer' to the oxygen This means that water molecules are polar – as one part is more negatively charged than the other This means that water molecules can attract each other J WERBA – IB BIOLOGY 12

STRUCTURE OF WATER Command term = DRAW and LABEL 3.1.4 STRUCTURE OF WATER Command term = DRAW and LABEL J WERBA – IB BIOLOGY 13

STRUCTURE OF WATER Command term = DRAW and LABEL 3.1.4 STRUCTURE OF WATER Command term = DRAW and LABEL Must include: Two water molecules drawn correctly = H2O Polarity O partially negative = δ–; H partially positive = δ+ Hydrogen bonding drawn as a dotted line J WERBA – IB BIOLOGY 14

PROPERTIES OF WATER Thermal properties: 3.1.5 PROPERTIES OF WATER Thermal properties: Water has a high specific heat capacity, a high heat of vaporisation and a high heat of fusion Extensive hydrogen bonding requires considerable thermal energy to break This allows lakes to absorb lots of heat energy & buffer temperature changes for aquatic organisms J WERBA – IB BIOLOGY 15

PROPERTIES OF WATER Cohesive properties: 3.1.5 PROPERTIES OF WATER Cohesive properties: Water molecules are strongly cohesive – ie. they stick to one another They also adhesive – ie. they stick to other molecules that are charged or polar Polarity of water molecule allows it to form hydrogen bonds with substances Creates surface tension & allows small insects to be able to walk on water J WERBA – IB BIOLOGY 16

PROPERTIES OF WATER Solvent properties: 3.1.5 PROPERTIES OF WATER Solvent properties: Water can dissolve many organic and inorganic substances Polar attraction of large quantities of water can overcome intramolecular bonds J WERBA – IB BIOLOGY 17

PROPERTIES OF WATER Other properties: Water is transparent! 3.1.5 PROPERTIES OF WATER Other properties: Water is transparent! allows light to pass through it important for photosynthesis Water floats! expands when frozen, becoming less dense/lighter important for life on earth - oceans don't freeze! J WERBA – IB BIOLOGY 18

3.1.6 USES OF WATER Coolant : Evaporation facilitates cooling (due to high heat of vaporisation) sweating and panting in animals transpiration from leaves in plants Water can also be used to carry heat to cooler places in our bodies J WERBA – IB BIOLOGY 19

USES OF WATER Medium for metabolic reactions: 3.1.6 USES OF WATER Medium for metabolic reactions: Water can dissolve many substances to facilitate chemical reactions (due to polarity) Water can also absorb thermal energy released as a by-product of many chemical reactions J WERBA – IB BIOLOGY 20

USES OF WATER Transport Medium: 3.1.6 USES OF WATER Transport Medium: Water can dissolve substances and use adhesion to move against gravity eg. in plants, minerals from the soil and sugars from the leaves can be transported in water through the xylem and phloem eg. in animals, water in the blood is used to transport oxygen, glucose and urea J WERBA – IB BIOLOGY 21

Sample questions Q1. Which diagram represents the polarity of a water molecule? J WERBA – IB BIOLOGY 22

Sample questions Q2. Which diagram best illustrates the interactions between water molecules? J WERBA – IB BIOLOGY 23

Sample questions A1. B A2. B J WERBA – IB BIOLOGY 24

Sample questions Q3. Explain how the properties of water are significant to living organisms. (9 marks) J WERBA – IB BIOLOGY 25

Sample questions A3. water is transparent / light passes through water; this allows organisms to live below the surface / plants to photosynthesize; hydrogen bonds between water molecules make water cohesive; this gives water a high surface tension allowing animals to live on the surface / maintains lung structure (pleural membranes); helps in water movement through plants/transpiration; water has a high latent heat of vaporization / OWTTE; evaporation/sweating/transpiration leads to cooling; water has a high specific heat capacity / OWTTE; this provides a stable environment for water organisms; water is a universal solvent; can transport materials around organisms/plants/animals; can be a solvent for chemical reactions in organisms; ice is less dense than water / water has a maximum density at 4°C; surface (pond/lake/ocean) freezes first, allowing organisms to survive in the water below; hydrogen bonds between water and other substance makes water adhesive J WERBA – IB BIOLOGY 26