Plant cell structure

An explanation plant cell structure and what each part does.

Plant cells are composed of many different elements. The outermost layer of the plant cell is known as the lipid bilayer, due to its compososition. This layer is composed of phospholipid molecules which have hydrophilic (water loving) heads and hydrophobic (water fearing) tails. These tails are attracted to each other, making the hydrophilic heads appear on both the outside and inside of the molecule. Due to these properties, the cell is what is known as selectively permeable.

Selective permeability only allows certain substances into the cell’s membrane. Most of this is determined by the concentration of the substance and its ability to move through membranes. This varies depending on the substance. Also within this layer of the cell are two different kinds of proteins – integral and peripheral.

Contained within this membrane are several organelles, which carry out all of the cell’s functions. These organelles are present only in eukaryotes, of which plants are classified. Not all eukaryotes contain all of these organelles, though all plants do.

Mitochondria are one organelle. It transfers energy from organic compounds to ATP (adendodine triphosphate, which is energy used in chemical reactions within the cell). Ribosomes are other organelles which synthesize proteins. The rough endoplasmic reticulum prepares proteins for export, and the smooth endoplasmic reticulum regulates calcium levels, breaks down toxic substances, and synthesizes steroids. The golgi body (or apparatus) processes and packages substances produced by the cell. The lysosome digests molecules, old organelles, and foreign substances (compare to the digestive and immune systems).

The microfilaments and microtubles contribute to the support, movement, and division of cells. Cilia and flagella are used in transport. Cilia are very short hairs that are attached to a surface to aid things moving though it, while flagella are often the ‘legs’ of microscopic organisms, enabling them to ‘swim.’ The nucleus, the most important part of the cell contains hereditary information in the form of DNA. It also synthesizes RNA and ribosomes.

The organelles in plants that aren’t found in other eukaryotes are the cell wall, which supports and protects a cell; the vacuole, which stores enzymes and waste products; and the plastids, which store food or pigments. Chloroplasts (which give the plants their green color, as well as soaking up the sun’s energy for photosynthesis) are classified as plastids.

All plants have a system to get water from the roots up to the leaves, where it’s needed for photosynthesis and other such processes. Water is ‘sucked’ up tiny tubes, which actually defies gravity. When a plant is separated from its roots, water obviously cannot get to the leaves. Because of osmosis (water having a tendency to move from high concentrations to lower concentrations), water then moves out of the cells, and the plant wilts. This is because the plant’s moisture level is lowered, and its cells cannot maintain their crisp shape. The cells shrivel up, which is viewed by the human eye as wilting.

What gives a plant its structure in the first place is cellulose. This is the substance that the cell wall is made of. The cell wall has two layers – the inner and outer layers. Once the outer layer is formed, the plant cannot grow anymore.

Written by Kate Hillard