Unit 1 AP Biology Insta-Review (Chemistry of Life)

Front

What type of bond is found in water molecules?

Back

Covalent

Answer explanation

Bonds between hydrogen and oxygen in water are covalent bonds. The two atoms are sharing their valence electrons.

Recall: This is a POLAR covalent bond since it is unequal sharing of the electrons

Front

What water property is responsible for the movement of water up the stem?

Back

Adhesion and cohesion

Answer explanation

Adhesion is the attraction of water molecules to other polar substances. The water is hydrogen bonded to the walls of the capillary tubes (xylem) of the plant.

Cohesion is the attraction of water molecules to other water molecules. The water is hydrogen bonded to another water molecule creating a “string” of like when you connect a barrel of monkeys.

Front

Which property of water is responsible for evaporative cooling?

Back

Specific heat

Answer explanation

Specific heat involves the amount of heat absorbed or released to increase or decrease the temperature of the substance by 1 degree Celsius.

Water has a high specific heat, and the water (sweat) will absorb the heat to cool off the animal.

Front

Which property of water allows life in lakes to survive during winter?

Back

Less dense as a solid

Answer explanation

Due to the hydrogen bonds, water molecules are unable to compact tightly which leaves space between the molecules and causes it to expand upon freezing making it less dense. This causes water to float to the surface creating a buffer to inhibit the lake from freezing which preserves life during winter.

Front

What type of bond is found between water molecules?

Back

Hydrogen

Answer explanation

The bond WITHIN water between the oxygen and hydrogen is a covalent bond since the atoms are sharing electrons from their valence shells. This causes a partial positive charge at the hydrogen and a partial negative charge at the oxygen. Those partial charges lead to hydrogen bonds BETWEEN water molecules as the oxygen of one water is attracted to a hydrogen of another water.

Front

What property of water is responsible for allowing rocks to skip on a pond?

Back

Cohesion

Answer explanation

Cohesion is due to the water molecules being attracted to other water molecules. These water molecules create a surface to the pond. Due to the large number of hydrogen bonds, the water has a high surface tension which is why the rock skips on the pond. Not enough force to break the bonds.

Front

What property of water allows aquatic life to survive during winter?

Back

Less Dense as Solid

Answer explanation

Due to the hydrogen bonds, water molecules are unable to compact tightly which leaves space between the molecules and causes it to expand upon freezing making it less dense. This causes water to float to the surface creating a buffer to inhibit the lake from freezing which preserves life during winter.

Front

What property of water is utilized by organisms during sweating?

Back

Evaporative Cooling

Answer explanation

Evaporative cooling is the act of water molecules absorbing the heat from the surface causing the water to evaporate (and taking the heat energy away from the organism).

Front

Where are hydrogen bonds in proteins? Note: Focus on the place where ONLY hydrogen bonds exist.

Back

Between backbone

Answer explanation

Hydrogen bonds are attractive bonds between an electronegative atom (e.g. O or N) and a hydrogen bonded to an electronegative atom. The backbone consists of the repeated amino and carboxyl groups. The amino has a nitrogen/hydrogen that is attracted to the carbonyl of the carboxyl group.

Front

Where are hydrogen bonds found in nucleic acids?

Back

Between nitrogenous bases

Answer explanation

Hydrogen bonds are attractive bonds between an electronegative atom (e.g. O or N) and a hydrogen bonded to an electronegative atom. The nitrogenous bases have the nitrogen/hydrogen attracted to the oxygen of the carbonyl or nitrogen of another nitrogenous base.