3.1- Biological Elements

Question 1

What determines bonding?

Answer 1

Bonding is determined by the number of unpaired electrons present in the outer orbitals of different elements:

• carbon atoms can form 4 bonds with other atoms.
• nitrogen atoms= 3 bonds.
• oxygen atoms= 2 bonds
• hydrogen atoms = 1 bond

Question 2

What is an ion?

Answer 2

An atom or molecule in which the total number of electrons is not equal to the total number of protons.

Cation= +ion
Anion= -ion

Electrolytes = ions in a solution

Question 3

Explain ionic bonding.

Answer 3

One atom in the pair donates an electron and the other receives it. This forms positive and negative ions held together by the attraction of opposite charges.

Question 4

What are the 5 main cations and their roles?

Answer 4

• calcium ions (Ca2+): nerve impulse transmission. Muscle contraction.
• sodium ions (Na+): nerve impulse transmission. Kidney function.
• potassium ions (K+): nerve impulse transmission. Stomatal opening.
• hydrogen ions (H+): catalysis of reactions. pH determination.
• ammonium ions (NH4+): production of nitrate ions by bacteria.

Question 5

What are the 5 main anions and their roles?

Answer 5

• 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 +charges of sodium and potassium ions in cells.
• phosphate ions (PO4*3-): cell membrane formation. Nucleic acid & ATP formation. Bone formation.
• hydroxide ions (OH-): catalysis of reactions. pH determination.

Question 6

What are the elements present in each of the 4 main biological molecules?

Answer 6

• carbohydrates: carbon, hydrogen, oxygen.
• Lipids: carbon, hydrogen, oxygen.
• Proteins: carbon, hydrogen, oxygen, nitrogen, sulfur.
• Nucleic acids: carbon, hydrogen, oxygen, nitrogen, phosphorus.

Question 7

What are polymers and monomers?

Answer 7

Polymers are long chains made up by the linking of multiple individual molecules (monomers) in a repeating pattern.

Monomers that are sugars= saccharides

Question 8

What monomers and polymers make up carbohydrates, proteins and nucleic acids?

Answer 8

Carbohydrates:

• monomer = monosaccharides (eg. Glucose)
• polymer= polysaccharides.

Proteins:

• monomer= amino acids (eg. Histidine)
• polymer= polypeptide, protein, enzyme.

Nucleic acids:

• monomer= nucleotides ( eg. Guanine)
• polymer= DNA, RNA.