What Is The Function Of Organelles In Eukaryotic Cells – Have you ever heard the phrase “form follows function?” This is a philosophy practiced in many industries. In architecture, this means that buildings must be constructed to support the activities that take place within them. For example, a skyscraper should be built with several elevator banks; Hospital emergency rooms should be built in such a way that they are easily accessible.

Our natural world has given rise to the principle of form following function, particularly in cell biology, and this will become clear as we explore eukaryotic cells. Unlike prokaryotic cells, eukaryotic cells have: (1) a membrane-bound nucleus; (2) numerous membrane-bound organelles—such as the endoplasmic reticulum, Golgi apparatus, chloroplasts, mitochondria, and others; and (3) multiple, rod-shaped chromosomes. The nucleus of a eukaryotic cell is often called the “true nucleus” because it is surrounded by a membrane. The word “organelle” means “small organ,” and, as mentioned earlier, organelles perform specialized cellular functions, just as organs in your body perform specialized functions.

What Is The Function Of Organelles In Eukaryotic Cells

What Is The Function Of Organelles In Eukaryotic Cells

Figure 1. These figures show the major organelles and other cell components of (a) a typical animal cell and (b) a typical eukaryotic plant cell. Plant cells have a cell wall, chloroplasts, plastids, and a central vacuole—structures not found in animal cells. Plant cells do not have lysosomes or centrosomes.

How The Endomembrane System Of Eukaryotic Cells Evolved

Before we begin looking at individual organelles, we need to briefly address the matrix in which they reside: the cytoplasm. The part of the cell called the cytoplasm is slightly different in eukaryotes and prokaryotes. In eukaryotic cells, which have a nucleus, the cytoplasm is everything between the plasma membrane and the nuclear envelope. In prokaryotes, which do not have a nucleus, the cytoplasm is everything inside the plasma membrane.

A major component of the cytoplasm in both prokaryotes and eukaryotes is the gel-like cytosol, a water-based solution that contains ions, small molecules, and macromolecules. In eukaryotes, the cytoplasm also contains membrane-bound organelles, which are suspended in the cytosol. The cytoskeleton, the network of fibers that supports the cell and gives it shape, is also part of the cytoplasm and helps organize cellular components.

Although the cytosol is mostly water, it has a semi-solid, jello-like consistency because of the many proteins suspended in it. The cytosol contains a rich broth of macromolecules and small organic molecules, including glucose and other simple sugars, polysaccharides, amino acids, nucleic acids and fatty acids. Ions of sodium, potassium, calcium and other elements are also found in the cytosol. Many metabolic reactions, including protein synthesis, take place in this part of the cell.

Figure 2. The nucleus stores chromatin (DNA plus protein) in a gel-like substance called the nucleoplasm. The nucleolus is a compact region of chromatin where ribosome synthesis takes place. The boundary of the nucleus is called the nuclear envelope. It consists of two phospholipid bilayers: an outer membrane and an inner membrane. The nuclear membrane is continuous with the endoplasmic reticulum. Nuclear pores allow substances to enter and leave the nucleus.

What Is An Organelle?

) holds the cell’s DNA and directs the synthesis of ribosomes and proteins. Let’s look at this in more detail (Figure 2).

The nuclear envelope is a double-membrane structure that forms the outer part of the nucleus (Figure 2). The inner and outer membranes of the nuclear envelope are phospholipid bilayers.

The nuclear envelope is punctuated with pores that control the passage of ions, molecules, and RNA between the nucleoplasm and cytoplasm. Nucleoplasm is the semi-solid fluid inside the nucleus, where we find chromatin and the nucleolus.

What Is The Function Of Organelles In Eukaryotic Cells

To understand chromatin, it is useful to first consider chromosomes. Chromosomes are structures within the nucleus that are made of DNA, the hereditary material. In prokaryotes, DNA is organized into single circular chromosomes. In eukaryotes, chromosomes are linear structures. Each eukaryotic species has a fixed number of chromosomes in the nucleus of its body cells. For example, in humans, the chromosome number is 46, while in fruit flies, it is eight. Chromosomes can only be seen and distinguished from each other when the cell is ready to divide. When a cell is in the growth and repair phases of its life cycle, proteins are attached to chromosomes, and they look like a strange, jumbled bunch of threads. These unwound protein-chromosome complexes are called chromatin (Figure 3); Chromatin describes the material that makes up chromosomes in both condensed and decondensed states. We will focus on chromatin and chromosomes in more detail later.

What Are Organelles? — Definition & Overview

Figure 3. (a) This image shows the different levels of organization of chromatin (DNA and protein). (b) This image shows paired chromosomes. (Credit B: work modified by NIH; scale-bar data from Matt Russell)

We already know that the nucleus directs the synthesis of ribosomes, but how does it do this? Some chromosomes contain segments of DNA that encode ribosomal RNA. A darkly stained area within the nucleus called the nucleolus (plural = nucleoli) stores ribosomal RNA with associated proteins that assemble ribosomal subunits that are then transported to the cytoplasm through pores in the nuclear envelope.

Figure 4. Ribosomes are composed of a large subunit (top) and a small subunit (bottom). During protein synthesis, ribosomes assemble amino acids into proteins.

Ribosomes are cellular structures responsible for protein synthesis. When viewed through an electron microscope, ribosomes appear as clusters (polyribosomes) or as single, small dots that float freely in the cytoplasm. They can be attached to the cytoplasmic side of the plasma membrane or the cytoplasmic side of the endoplasmic reticulum and the outer membrane of the nuclear envelope. Electron microscopy has shown us that ribosomes, which are large complexes of protein and RNA, are composed of two subunits, called large and small (Figure 4). Ribosomes receive their “orders” for protein synthesis from the nucleus where the DNA is transcribed into messenger RNA (mRNA). The mRNA moves to ribosomes, which translate the code provided by the sequence of nitrogenous bases in the mRNA into a specific order of amino acids in a protein. Amino acids are the building blocks of proteins.

Comparing Prokaryotic And Eukaryotic Cells

Because protein synthesis is an essential function of all cells, ribosomes are found in practically every cell. Ribosomes are especially abundant in cells that synthesize large amounts of protein. For example, the pancreas is responsible for creating many digestive enzymes and the cells that produce these enzymes contain many ribosomes. Thus, we see another example of function following the form.

) are often called the cell’s “powerhouse” or “energy factory” because they are responsible for making adenosine triphosphate (ATP), the cell’s main energy-carrying molecule. ATP represents the cell’s short-term stored energy. Cellular respiration is the process of making ATP using the chemical energy found in glucose and other nutrients. In the mitochondria, this process uses up oxygen and produces carbon dioxide as a waste product. In fact, the carbon dioxide that you exhale with every breath comes from cellular reactions that produce carbon dioxide as a byproduct.

In keeping with our form following function theme, it is important to point out that muscle cells have a very high concentration of ATP-producing mitochondria. Your muscle cells need a lot of energy to keep your body moving. When your cells don’t get enough oxygen, they don’t make as much ATP. Instead, the small amount of ATP they make in the absence of oxygen is accompanied by the production of lactic acid.

What Is The Function Of Organelles In Eukaryotic Cells

Figure 5. This electron micrograph shows a mitochondrion viewed with a transmission electron microscope. This organ consists of an outer membrane and an inner membrane. The inner membrane has folds, called cristae, that increase its surface area. The space between the two membranes is called the intermembrane space, and the space within the inner membrane is called the mitochondrial matrix. ATP synthesis occurs in the inner membrane. (Credits: work modification by Matthew Britton; scale-bar data from Matt Russell)

Answered] For Each One Of The Eukaryotic Organelles Structures…

Mitochondria are oval-shaped, double-membrane organelles (Figure 5) that contain their own DNA and ribosomes (we’ll talk about these later!) Each membrane is embedded with a phospholipid bilayer protein. The inner layer consists of layers called cristae. The area surrounded by the layers is called the mitochondrial matrix. The cristae and the matrix have different roles in cellular respiration.

Peroxisomes are small, round organelles surrounded by a single membrane. They carry out oxidation reactions that break down fatty acids and amino acids. They also detoxify many toxins that may enter the body. Many of these oxidation reactions produce hydrogen peroxide, H

, which will be harmful to cells; However, when these reactions are confined to peroxisomes, the enzymes safely break down H

In oxygen and water. For example, alcohol is detoxified by peroxisomes in liver cells. Glyoxysomes, which are specialized peroxisomes in plants, are responsible for converting stored fat into sugar.

Lecture 2 Cell Biology Eukaryotic Cell Structure: Structure And Function Of Cell Organelles Prepared By Mayssa Ghannoum.

Figure 6. Membrane and secretory proteins are synthesized in the rough endoplasmic reticulum (RER). The membrane of the RER sometimes contains modified proteins. (Credit: Modification of work by Magnus Manske)

= “inside”) in eukaryotic cells is a group of membranes and organelles (Figure 6) that work together to modify, package, and transport lipids and proteins. These include the nuclear envelope, lysosomes, vesicles, and the endoplasmic reticulum and Golgi apparatus, which we will cover shortly.

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