Unit 2 - Biological Elements & Water Flashcards
Specification reference 2.1.2
All living things are made primarily from which four key elements?
Carbon (C) Hydrogen (H) Oxygen (O) Nitrogen (N)
In addition to the four key elements all living things are made primarily from, what other two elements play important roles in the biochemistry of cells ?
Phosphorus (P) Sulphur (S)
Five cations (+ve ions) that play important roles in organisms
Calcium ions (Ca2+) - Nerve impulse transmission and muscle contractions
Sodium ions (Na+) - Nerve impulse transmission and kidney function
Potassium ions (K+) - Nerve impulse transmission and stomatal opening
Hydrogen ions (H+) - Catalysis of reactions, proton pump in photosynthesis, pH determination.
Ammonium ions (NH4+) - Production of nitrate ions
Five anions (-ve ions) that play important roles in organisms
Nitrate ions (NO3-) - Nitrogen supply to plants for amino acid and protein formation
Hydrogen carbonate ions (HCO3-) - Maintenance of blood pH
Chloride ions (Cl-) - Balance positive charge of sodium and potassium ions in cells
Phosphate ions (PO43-) - Cell membrane formation, nucleic acid and ATP formation, and bone formation
Hydroxide ions (OH-) - Catalysis of reactions, pH determination
Which elements are found in carbohydrates?
Carbon, hydrogen and oxygen.
Which elements are found in lipids?
Carbon, hydrogen and oxygen.
Which elements are found in proteins?
Carbon, hydrogen, oxygen, nitrogen and sulphur.
Which elements are found in nucleic acids?
Carbon, hydrogen, oxygen, nitrogen and phosphorus.
Define the term ‘polar’ in relation to molecules.
Molecules that have regions or negativity and regions of positivity
This is due to the way in which electrons are distributed between elements joined by a covalent bond.
Explain how polar molecules like water interact with each other.
The positive and negative regions of the molecules attract each other and form hydrogen bonds.
These bonds give water its cohesive properties - it moves as one body because the molecules are attracted to each other.
These bonds also give water its adhesive properties - it molecules are attracted to other surfaces.
Explain how the ‘skin’ of surface tension of water enables a pond skater to inhabit the surface of water?
The skin is caused by water molecules are more strongly cohesive to each other than to air, this skin supports the pond skater.
Hydrogen bonds are…
Relatively weak interaction that form and break between the constantly moving water molecules.
There are large numbers of then though, which give water its unique characteristic that are essential for life on Earth.
What are the unique characteristics of water that are essential for life on Earth?
- Unusually high specific heat capacity (boiling point).
- Becomes less dense when it freezes.
- Cohesive properties
- Adhesive properties
- ‘Skin’ of surface tension
Why is it good that water has a high specific heat capacity?
Keeps habitats stable for living things as a lot of energy is needed to change it by a degree.
What makes it more difficult for water to become a gas?
Hydrogen bonding between molecules