HESI Readiness Course (Biology): Water

The role of water?

Two important roles of water are to help cells with transport of chemicals or nutrients and to hold shape of cells.

What is a water molecule made of?

2 hydrogen atoms and 1 oxygen atom (H2O)

Which atoms of a water molecule has a positive or negative?

Positive on the hydrogen side

Negative on the oxygen side

What is a Polar Molecule?

An asymmetrical arrangement of the atoms in a water molecule.

Electrons in Hydrogen atoms are strongly attracted to Oxygen atoms that they are actually closer to the oxygen atom’s nucleus than to the nuclei of the hydrogen atoms

Why is water a good solvent?

The Polar quality is the force that causes water molecules to bond so readily with other molecules; meaning its due to its polar structure.

What is required to break hydrogen bonds?

Heat!

Hydrogen bonding releases heat, and heat absorption is required to break hydrogen bonds.

The role of water for maintaining the life on Earth?

Temperature regulation is vital (For both land and water)

Is water denser in its solid form or liquid form?

Liquid Form

Water is densest at 4°C, so what happens when the temp is above this point?

Water expands as it warms and contracts as it cools

Water is densest at 4°C, so what happens when the temp is below this point?

Water expands as it cools and water molecules slow to the point where hydrogen bond forms.

Water is densest at 4°C, so what happens when the temp is 0°C?

Molecules organized in a crystalline structure, which hydrogen bonding keeps them equally spaced at distances far enough apart to make ice less dense than water.

How does water move throughout a plant?

Water moves from one plant cells into leaf pores one molecule at a time.

What is Polar?

Water has two differently charged ends (think of two different ends of a pole) 

What Nonpolar?

Molecules that do not have two differently charged ends (or have a neutral charge) 

What is a Hydrogen Bond?

Due to water's polarity, the positive end of one water molecule (H+) interacts with the negative end of a different water molecule (O+).

What is Phospholipid consisted of?

The membrane has layers of molecules that have both polar end (the head) and non-polar ends (the tails). The polar ends are called hydrophilic (water-loving) because they are attracted to the water (because water is polar) and the non-polar ends are called hydrophobic (water-fearing) because they are repelled by the water.

What are the three states of Matter in Water?

Liquid: In liquid state, the water molecules interact in a state of equilibrium.

Gas: the hydrogen bonds between the molecules break, and water is released in the form of steam.

Solid: The molecules form a crystalline structure that maintains the hydrogen bonding. Unlike other liquids that turn to solid, however, this structure and bonding makes ice less dense than liquid water.