Water and Macromolecules

Question 1

What is the cell theory?

Answer 1

1. The cell is the smallest living unit in all organisms.
2. All living organisms are composed of cells.
3. All cells come from pre-existing cells.

Question 2

Why is water important?

Answer 2

1. Serves as the universal solvent in biological systems (living organisms)
2. Makes up 70% or more of the weight of most cells
3. Creates an aqueous extracellular environment for organisms and cells to survive

Question 3

What is the molecular structure of water?

Answer 3

• Two hydrogen atoms in water are covalently bonded to the one oxygen atom at an angle of 104.5°
• Electronegativity (O is strongly electronegative (attracts e-), H is electropositive (donates e-))
• Unequal distribution of charges; water molecule as a whole is uncharged (O has δ−, H has δ+)
• Polar molecule (two ends of molecule have opposite charges)

Question 4

What is a hydrogen bond?

Answer 4

A bond formed between a hydrogen atom and an electronegative atom (F,O,N) that belongs to another chemical group.

Question 5

Why are hydrogen bonds important?

Answer 5

Crucial in maintaining the structure and function of biological molecules. (Eg. Carbohydrates, proteins, nucleic acids)

Question 6

Properties of hydrogen bonding.

Answer 6

• δ+ region of one molecule comes close to δ− region of another molecule, electrical attraction between them result in a weak bond
• hydrogen bonding is much weaker than covalent bonds, but combined effort of many weak bonds is highly significant
• occurrence of hydrogen bonding is not unique to water; it can be found in other biological molecules
• 1 water molecule
• each oxygen atom can form hydrogen bond to two hydrogen atoms
• both hydrogen atoms can form hydrogen bonding with oxygen atoms of adjacent molecules