Chemistry of life - Lesson 1 Flashcards
State the definition of ionic bonding
When 2 or more atoms donate electrons to each other, forming strong ionic bonds, which are forces of attraction that hold the oppositely charged ions together
State the definition of covalent bonding
When 2 or more atoms share electrons, forming strong covalent bonds.
how does covalent bonding form polar molecules
when the electrons in the covalent bonds are not evenly shared, forming a dipole.
what happens to ionic substances when they are in water
they dissolve, as the ions attract the dipoles in the water molecules, forming hydrogen bonds
what is the function of nitrate ions (NO3-)
needed in plants for the formation of amino acids and DNA
what is the function of phosphate ions (PO4-3)
needed in plants and animals for the formation of ATP, ADP, DNA and RNA
what is the function of chloride ions (Cl-)
needed in nerve impulses and many secretory systems
what is the function of hydrogen carbonate ions (HCO3-)
needed for buffering the blood to prevent it from becoming too acidic
what is the function of sodium ions (Na+)
needed in nerve impulses and many secretory systems
what is the function of calcium ions (Ca+2)
needed for the formation of calcium pectate for the middle lamella, for for bone formation and muscle contraction in animals
what is the function of hydrogen ions (H+)
needed in cellular respiration and photosynthesis, and to balance the pH
what is the function of magnesium ions (Mg+2)
needed for production of chlorophyll in plants
why does water have a high melting point
because it takes a lot of energy to overcome the attractive forces of all the hydrogen bonds
what are hydrogen bonds
weak electrostatic intermolecular bonds formed between polar molecules and hydrogen atoms
what are 8 characteristics of water
- a polar solvent
- a transport medium
- maximum density at 4°C
- high specific heat capacity
- cannot be compressed
- cohesive
- adhesive
- high surface tension
why is it important that water is a polar solvent
because many ionic substances and polar molecules dissolve in water. So, many chemical reactions in cells occur in water
why is water an excellent transport medium
because many substances dissolve in water, water can transport molecules easily
why is it important that water has a maximum density at 4°C
as a result, ice is less dense than water and floats, forming an insulated layer and helps to prevent water underneath it from freezing. This means organisms can live under the ice
why is it important that water has a high specific heat capacity
because it takes a lot of energy to break the hydrogen bonds, the temperature doesn’t change that much, making large bodies of water good habitats
why is it important that water cannot be compressed
makes it important for hydraulic mechanisms in organisms
why is it important that water is cohesive
the forces cause water molecules to stick together. This is important for water movement from roots to leaves in plants
why is it important that water is adhesive
they are attracted to other molecules, which is important in plant transport and in surface tension
why is it important that water has a high surface tension
because the attraction between the water molecules (hydrogen bonds) is greater than the attraction between water molecules and air, water molecules form a thin skin of surface tension. This is important for plant transport systems
