- Plant cells have a cell wall.
Plant cells are different from animal cells in a number of ways. Perhaps the most obvious difference is the presence of a cell wall. The cell wall provides strength and support to the plant, much like the exoskeleton of an insect or spider (our skeleton is on the inside of our body, rather than on the outside like insects or spiders).
The plant cell wall is mainly made up of the carbohydrates molecules cellulose and lignin. Cellulose is used extensively by humans for making paper. Cellulose can also be converted into cellulosic ethanol, a type of biofuel. Some animals, such as cows, sheep and goats, can digest cellulose with the help of bacteria in their stomachs. Humans cannot digest cellulose, which passes through our bodies and is better known as dietary fiber, something that we should eat to keep our waste moving as it should! Lignin fills in the spaces between cellulose and other molecules in the cell wall. Lignin also helps water molecules move from one side of the cell wall to the other – an important function in plants.
- Plant cells contain vacuoles.
Most adult plant cells have one large vacuole that takes up more than 30% of the cell’s volume. At certain times and conditions the vacuole takes up as much as 80% of the cell’s volume! In addition to storing wastes and water, the vacuole also helps to support the cell because the liquid inside the vacuole exerts an outward pressure on the cell, much like the water inside of a water balloon. This is called turgor pressure and keeps the cells from collapsing inward.
- Plant cells contain chloroplasts.
Unlike animal cells, plant cells can harness the energy of the Sun, store it in the chemical bonds of sugar and later use this energy. The organelle which is responsible for this is the chloroplast. Chloroplasts contain chlorophyll, the green pigment that gives leaves their colour and absorbs light energy. Cyanobacteria, a type of prokaryote capable of photosynthesis, are considered to be the ancestors of chloroplasts!