Eukaryotic cells Essays

Eukaryotes are cells categorized as having a nucleus and a variety of other membrane-enclosed organelles. Eukaryotes include plants, animals, fungi, and protists. Eukaryotic cells have greater mass than prokaryotic cells and have far more internal complexity. Within each eukaryotic cell, internal membranes create multiple compartments. These compartments, called organelles, carry out specific functions through independent chemical reactions. Eukaryotic cells Essays.

In eukaryotic cells, the DNA is separated from the rest of the cell in the nucleus by the nuclear membrane. This separation is important in the regulation of protein synthesis, as the cellular structures that produce proteins are found outside the nucleus. The nuclear membrane limits the type of molecules that can reach the DNA and also limits the type of molecules that can leave the nucleus and reach the protein synthesis machinery of the cell. Eukaryotic cells have more precise regulation of the production of proteins and their RNA intermediates than do prokaryotes, in which the DNA is not sequestered from the rest of the cell.

One feature of eukaryotic cells, particularly within multicellular organisms, is the variety of shapes and sizes of these cells. The shape of the cell is related to the function it performs. Nerve cells, for example, have fingerlike projections that allow them to communicate over a distance. In addition, cells aggregate to form larger structures, such as tissues and organs, that perform specific functions. Eukaryotic cells Essays.

Membrane-Bound Organelles

Junctions and Other Structures

While both animals and plants are composed of eukaryotic cells, their cells have different structures and functions. Plant cells are generally rectangular and tend to be larger than animal cells. Plant cells, like animal cells, join together to form tissues. Plants have far fewer types of tissues than higher order animals, but the basic cell structure of plants (such as algae and a giant sequoia) are the same. Eukaryotic cells Essays.

Plants are autotrophs; they produce their own food and form the primary level in most food chains. Food production occurs because plant cells have specialized membrane-bound organelles called chloroplasts. Chloroplasts contain chlorophyll, which provides the plant’s green hue and is the plant’s means of absorbing light energy from the sun. The sun’s energy is combined with water and carbon dioxide in the plant’s process of photosynthesis. The end products of photosynthesis are sugars and waste oxygen. Eukaryotic cells Essays.

While chloroplasts perform the primary task of food production, other organelles play a role in cellular metabolism. Vacuoles are membrane-bound sacs, much like a bubble, that store nutrients and waste products. Water stored in vacuoles helps keep plant stems, limbs, and branches rigid. The crunch of a carrot comes from the vacuole’s ability to maintain turgor pressure, the pressure of water against the plasma membrane, within each cell. That pressure supports the cell wall and the overall structure of the plant. When the vacuoles do not retain sufficient water, plants wilt. Organelles called peroxisomes have a variety of tasks related to conversion of waste from cellular metabolism. These organelles transform fatty acids into sugars and aid chloroplasts in oxidizing plant sugars.

Plant cells have stiff cell walls that are made of cellulose, which protect both the cell itself, and the plant as a whole. Plant cells join together to form tissues, such as the vascular tissues phloem and xylem. The phloem transports sugars away from the leaves, while the xylem transports water, minerals, and other nutrients upward from the roots. Other types of cells form protective tissue layers to help plants retain water. Eukaryotic cells Essays.

Animal cells are eukaryotic cells enclosed within a plasma membrane and contain a variety of membrane-bound organelles suspended in the cytoplasm. Like plant cells, animal cells have a nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, and ribosomes. They may also have centrioles, cilia or flagella, and lysosomes, which are not usually found in plant cells.

A centriole is made up of a ring of nine groups of fused microtubules, long strands of protein that form tubes. These structures are part of the cytoskeleton, a lattice-like structure that protects cells. In an animal cell, a centrosome consists of two centrioles arranged perpendicular to each other. Centrosomes are organelles that divide and migrate during reproduction Eukaryotic cells Essays. They provide strength to a cell’s structure and pull apart chromatids (threadlike strands containing a double helix of DNA) when cells divide.

Some animal cells also contain cilia or flagella, structures that are anchored in the cell membrane. Cilia and flagella push fluids along the surfaces of cells. Flagella are thin, whiplike tails that assist cells in movement. A sperm cell, for example, has a flagellum to enable it to move to find and fertilize an egg. Giardia is a common protist parasite that has a flagellum. Cilia are tiny hairlike structures found on the surface of unicellular animals, such as paramecia, and function in locomotion. Cilia are also found on the cells lining the human respiratory tract, where they help remove debris from the lungs.

Animal cells contain lysosomes, which are organelles that hold enzymes created by the cell that break down complex molecules such as proteins. Lysosomes fuse with vacuoles that contain material derived from within the cell, such as damaged organelles, or ingested from outside the cell. Once the membranes fuse, the contents of the vacuoles are exposed to the enzymes in the lysosome and are degraded. The components can then be reused by the cell.

Animal cells exhibit a variety of shapes and sizes that are related to their function Eukaryotic cells Essays. Elongated smooth muscle cells, round white blood cells, and spiky neurons all have the same basic cellular components.