Questions

Any two amino acids vary structure by the r-group, otherwise all amino acids are in the same structure. All amino acids have in common carboxyl group -COO , amino group -NH3+ and a hydrogen -H and a r-group which are all bonded to a central carbon.

Yes, plant cells have Mitochondria.

While plant cells have chloroplasts to photosynthesize, they also require ATP for cellular functions, and do use oxygen to break down some of the sugar they produce in order to generate that ATP. They need mitochondria for this.

In particular, at night when there is no light, plants undergo cellular respiration since there is no sunlight to photosynthesize.

They do, however, produce far more sugar and oxygen through photosynthesis than they use up in respiration.

Air pollutants are solid particles, gases, and liquid droplets in the air that can adversely affect ecosystems and the health of humans.

Major ambient air pollutants include toxic metals, polycyclic aromatic hydrocarbons, benzene, particulate matter (PM), nitrogen oxides, sulfur oxides, carbon monoxide, and ozone. Power plants, factories, and vehicle and air traffic are the most important anthropogenic sources of air pollution.

In addition, natural sources such as wildfires and volcanic activity contribute to ambient air pollution.

As water is cooled from 4 deg C to 0 deg C, the water reaches its freezing point and starts forming ice crystals. Then the volume of that ice cubes increases and its density decreases. Hence, it is the reason that ice will float on water as ice has less density than the water.