1. CHEMICAL ELEMENTS & WATER
Topic 3.1
IB Biology
Miss Werba

2. 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
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3. THINGS TO COVER Common chemical elements in living things
Structure of water molecules
Properties of water
Uses of water in living organisms
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4. 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
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5. CHEMISTRY REVISION Protons Neutrons Electrons Positive charge
In the nucleus
Neutrons
No charge
In the nucleus
Electrons
Negative charge
Orbit the nucleus
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6. CHEMISTRY REVISION Covalent bonds: atoms share electrons
Ionic bonds: where electrons are transferred from one atom to another, forming positively or negatively ions
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7. 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
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8. 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
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9. 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
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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 :
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
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11. 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
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12. 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
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13. STRUCTURE OF WATER Command term = DRAW and LABEL
3.1.4
STRUCTURE OF WATER Command term = DRAW and LABEL
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14. 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
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15. 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
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16. 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
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17. 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
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18. 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!
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19. 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
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20. 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
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21. 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
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22. Sample questions
Q1. Which diagram represents the polarity of a water molecule?
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23. Sample questions
Q2. Which diagram best illustrates the interactions between water molecules?
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24. Sample questions
A1. B
A2. B
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25. Sample questions
Q3. Explain how the properties of water are significant to living organisms.
(9 marks)
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26. 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
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