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Eukaryotic Cell Parts And Functions Pdf

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2.3: Eukaryotic Cell: Structure and Function

Goodman, Steven R. Last reviewed: March The microscopic functional and structural unit of all living organisms. Cells can be separated into prokaryotic and eukaryotic categories. Eukaryotic cells contain a nucleus. They include two classes of bacteria: eubacteria including photosynthetic organisms, or cyanobacteria , which are common bacteria that inhabit soil, water, and larger organisms; and archaebacteria, which grow under unusual conditions.

All eubacteria have an inner plasma membrane that serves as a semipermeable barrier Fig. The plasma membrane, which is a lipid bilayer, utilizes transmembrane transporter and channel proteins to facilitate the movement of these molecules. See also: Cell membranes. Eubacteria can be further separated into two classes based on their ability to retain the dye crystal violet.

Gram-positive cells retain the dye; their cell surface includes the inner plasma membrane and a cell wall composed of multiple layers of peptidoglycan. Gram-negative bacteria are surrounded by two membranes: the inner plasma membrane and an outer membrane that allows the passage of molecules of less than dalton Da molecular weight through porin protein channels.

The peptidoglycan-rich cell wall and the periplasmic space are located between the inner and outer membranes. Eubacteria contain a single circular double-stranded molecule of deoxyribonucleic acid DNA , or a single chromosome.

Because prokaryotic cells lack a nucleus, this genomic DNA resides in a central region of the cell Fig. Bacterial replication requires accurate duplication of this chromosomal DNA, with both copies attaching by cross-wall formation to the plasma membrane, allowing the formation of two identical daughter cells by binary fission. The bacterial genome contains all the information necessary to maintain the structure and function of the cell.

Many bacteria are able to move from place to place, or are motile. Their motility is based on a helical flagellum composed of an interwoven protein called flagellin. The flagellum is attached to the cell surface through a basal body and propels the bacteria through an aqueous environment by rotating this action is similar to that of a propeller on a motorboat.

The movement is reversible, allowing the bacteria to move toward chemoattractants and away from chemorepellents. See also: Cilia and flagella. In a light microscopic view of a eukaryotic cell, a plasma membrane can be seen that defines the outer boundaries of the cell, surrounding the cell's protoplasm or contents.

The protoplasm includes the nucleus, where the eukaryotic cell's DNA is compartmentalized away from the remaining contents of the cell the cytoplasm ; therefore, the protoplasm includes the nucleus and the cytoplasm.

In addition, the cytoplasm contains other organelles specialized subcellular structures that carry out a specific function , including the mitochondrion, endoplasmic reticulum, Golgi apparatus, lysosome, peroxisome, cytoskeleton, and plasma membrane Fig. The organelles occupy approximately half the total volume of the cytoplasm. The remaining compartment of cytoplasm minus the organelles is referred to as the cytosol or cytoplasmic ground substance.

Eukaryotic cells also have a cytoskeleton that gives the cell its shape, its capacity to move, and its ability to transport organelles and vesicles from one part of the cell cytoplasm to another. The cytoskeleton is composed of microfilaments 7—8 nm in diameter , intermediate filaments 10 nm in diameter , microtubules 25 nm in diameter , and a spectrin-based membrane skeleton.

Eukaryotic cells are generally larger than prokaryotic cells and thus require a cytoskeleton and membrane skeleton to maintain their shape. See also: Cell organization ; Cytoplasm. Therefore, whether a cell becomes a muscle fiber or a neuron depends on the expression of muscle-specific genes or neuron-specific genes although both are present.

See also: Gene ; Protein. The plasma membrane serves as a selective permeability barrier between a cell's environment and its cytoplasm. The fundamental structure of plasma membranes as well as organelle membranes is the lipid bilayer, formed as a result of the tendency of amphipathic phospholipids to bury their hydrophobic fatty acid tails away from water.

Human and animal cell plasma membranes contain a varied composition of phospholipids, cholesterol, and glycolipids. Although lipids determine the bilayer structure, membrane proteins are primarily responsible for membrane function. Both the lipids and proteins of the plasma membrane are distributed asymmetrically across the bilayer. This creates a membrane topography in which selected membrane domains can have differing protein and lipid composition and also function.

The so-called lipid rafts constitute one of these domains, comprising a cholesterol-rich region of the lipid bilayer containing specific proteins such as flotillin and stomatin. See also: Cholesterol ; Lipid ; Lipid rafts membranes ; Phospholipid. The cytoskeleton is involved in establishing cell shape, polarity, and motility, as well as in directing the movement of organelles within the cell. The cytoskeleton includes microfilaments, microtubules, intermediate filaments, and the two-dimensional membrane skeleton that lines the cytoplasmic surface of cell membranes.

See also: Cytoskeleton. One of the most prominent organelles within a eukaryotic cell is the nucleus. The nuclear compartment is separated from the rest of the cell by a specialized membrane complex built from two distinct lipid bilayers, referred to as the nuclear envelope. However, the interior of the nucleus maintains contact with the cell's cytoplasm via nuclear pores. These structures form holes or channels in the nuclear envelope that are responsible for the selective uptake of nuclear components and the release of components destined for the cell cytoplasm.

The primary function of the nucleus is to house the genetic apparatus of the cell; this genetic machinery is composed of DNA arranged in linear units called chromosomes , ribonucleic acid RNA , and proteins.

Nuclear proteins aid in the performance of nuclear functions and include polypeptides that have a direct role in the regulation of gene function and those that give structure to the genetic material. The complex of DNA and structural proteins is known as chromatin, which can be either highly compacted heterochromatin or dispersed euchromatin within the nucleus.

A specialized region within the nucleus that is visible in interphase cells is the nucleolus, which functions in the production and assembly of ribosomal subunits. The endoplasmic reticulum is composed of membrane-enclosed flattened sacs or cisternae. The enclosed compartment is called the lumen. See also: Endoplasmic reticulum. The final modifications of proteins and glycolipids occur within a series of flattened membranous sacs comprising the Golgi apparatus.

Vesicles that bud from the endoplasmic reticulum fuse with a specialized region of the cis Golgi compartment called the cis Golgi network. Modifications occur first in the cis compartment and then in the medial and trans Golgi network compartments. In each case, the membrane transfer occurs by the blebbing of coated vesicles from one compartment and their fusion with the next. In the trans Golgi network, proteins and lipids are sorted into transport vesicles destined for lysosomes, the plasma membrane, or secretion.

See also: Golgi apparatus. The lysosome is a membrane-bound organelle with a luminal pH of 5. Found in animal cells and not plant cells , the lysosome is responsible for degrading materials brought into the cell by endocytosis or phagocytosis, or by autophagocytosis of spent cellular material. See also: Lysosome. The mitochondrion contains a double membrane: the outer membrane, which contains a channel-forming protein named porin; and an inner membrane, which contains multiple infolds called cristae.

The porin channel allows molecules of less than 10,Da molecular weight free passage between the cytoplasm and the intermembrane space. The inner membrane, which contains the protein complexes responsible for electron transport and oxidative phosphorylation, is folded into numerous cristae that increase the surface area per volume of this membrane.

The transfer of electrons from nicotinamide adenine dinucleotide NADH or flavin adenine dinucleotide FADH 2 down the electron-transfer chain to oxygen causes protons to be pumped out of the mitochondrial matrix into the intermembrane space. Within the peroxisome, hydrogen atoms are removed from organic substrates, and hydrogen peroxide is formed.

The enzyme catalase can then utilize the hydrogen peroxide to oxidize various substrates, including alcohols, formaldehydes, and formic acid, in detoxifying reactions. See also: Peroxisome. Plant cells are distinguished from other eukaryotic cells by various features Fig. For example, plant cells have an extremely rigid cell wall outside their plasma membrane. This cell wall is composed of cellulose and other polymers and is distinct in composition from the cell walls found in fungi or bacterial cells.

The plant cell wall expands during cell growth, and a new cell wall partition is created between the two daughter cells during cell division. Similar cell walls are not observed in animal cells. Most plant cells contain membrane-encapsulated vacuoles as major components of their cytoplasm.

These vacuoles contain water, sucrose, ions, nitrogen-containing compounds formed by nitrogen fixation, and waste products.

The amount of osmotic particles within the vacuoles is much higher than in the cytosol or extracellular fluid. The encapsulating membrane is permeable to water, but impermeable to the molecules within the vacuole.

Therefore, water rushes into the vacuole, the vacuole expands, and a hydrostatic pressure or turgor is created within the cell. This turgor is resisted by the cellulose-containing cell wall; however, as the cell wall stretches, the plant grows.

See also: Vacuole. Chloroplasts are the other major organelles in plant cells that are not found in other eukaryotic cells. Like mitochondria, they are constantly in motion within the cytoplasm. One of the pigments found in chloroplasts is chlorophyll, which is the molecule that absorbs light and gives the green coloration to the chloroplast.

Chloroplasts, like mitochondria, have outer and inner membranes. Within the matrix of the chloroplast, there is an intricate internal membrane system. The internal membranes are made up of flattened interconnected vesicles, called thylakoid vesicles, which take on a disklike structure.

The thylakoid vesicles are stacked to form structures called grana, which are separated by a space called the stroma. Within the stroma, carbon dioxide fixation occurs, in which carbon dioxide is converted to various intermediates during the production of sugars.

Chlorophyll is found within the thylakoid vesicles; it absorbs light and, with the involvement of other pigments and enzymes, generates ATP during photosynthesis. See also: Cell plastids ; Chlorophyll ; Photosynthesis. To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.

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Cell biology Article by: Goodman, Steven R. Key Concepts Hide A cell is the microscopic functional and structural unit of all living organisms. Eukaryotic cells have a nucleus and multiple, compartmentalized molecules of linear DNA.

Different Cell Organelles and their Functions

By definition, eukaryotic cells are cells that contain a membrane-bound nucleus, a structural feature that is not present in bacterial or archaeal cells. In addition to the nucleus, eukaryotic cells are characterized by numerous membrane-bound organelles such as the endoplasmic reticulum, Golgi apparatus, chloroplasts, mitochondria, and others. In previous sections, we began to consider the Design Challenge of making cells larger than a small bacterium — more precisely, growing cells to sizes at which, in the eyes of natural selection, relying on diffusion of substances for transport through a highly viscous cytosol comes with inherent functional trade-offs that offset most selective benefits of getting larger. In the lectures and readings on bacterial cell structure, we discovered some morphological features of large bacteria that allow them to effectively overcome diffusion-limited size barriers e. As we transition our focus to eukaryotic cells, we want you to approach the study by constantly returning to the Design Challenge.

Goodman, Steven R. Last reviewed: March The microscopic functional and structural unit of all living organisms. Cells can be separated into prokaryotic and eukaryotic categories. Eukaryotic cells contain a nucleus. They include two classes of bacteria: eubacteria including photosynthetic organisms, or cyanobacteria , which are common bacteria that inhabit soil, water, and larger organisms; and archaebacteria, which grow under unusual conditions. All eubacteria have an inner plasma membrane that serves as a semipermeable barrier Fig.


Eukaryotic cells are typically microns in diameter. -A large cell requires "​much more" in terms of the cellular components. -Uptake from the environment is​.


1.2.1 Eukaryotic Cell Structures & Functions

The structure of the cell surface membrane — although the structure looks static the phospholipids and proteins forming the bilayer are constantly in motion. The cell wall is freely permeable to most substances unlike the plasma membrane. The nucleus of a cell contains chromatin a complex of DNA and histone proteins which is the genetic material of the cell.

Organelles make up the subunits of a cell. There are numerous each with their own function. The plasma membrane is the organelle that encapsulates the contents of the cell. Apart from encapsulating cell contents, the plasma membrane also plays a vital role in regulating the movement of substances in and out of the cell.

Sources and Helpful Eukaryotic Cell Links. Becker, W. Pearson Benjamin Cummings. Inside a Cell , interactive cell diagram from University of Utah.

Cell (biology)

Eukaryotic Cell Structure and Function PDF

A eukaryotic cell has a true membrane-bound nucleus and has other membranous organelles that allow for compartmentalization of functions. Like a prokaryotic cell, a eukaryotic cell has a plasma membrane, cytoplasm, and ribosomes. However, unlike prokaryotic cells, eukaryotic cells have:. They allow different functions to be compartmentalized in different areas of the cell. Typically, the nucleus is the most prominent organelle in a cell. The nuclear envelope is a double-membrane structure that constitutes the outermost portion of the nucleus. Both the inner and outer membranes of the nuclear envelope are phospholipid bilayers.

The cell from Latin cella , meaning "small room" [1] is the basic structural, functional, and biological unit of all known organisms. Cells are the smallest units of life, and hence are often referred to as the "building blocks of life". The study of cells is called cell biology , cellular biology, or cytology.

Oluwole O. An organelle is a specialized functional subunit within cells carrying out specific functions. These compartments which may or may not be enclosed in a lipid bilayer are found in microorganisms. All microbes have compartments common to them like the nucleic acids, protein, ribosomes as well as unique intracellular structures found only in microbial subgroups. Such compartments include the mitochondria, endoplasmic reticulum, golgi apparatus amongst others unique to all eukaryotic cells only. Prokaryotes contain some micro-compartments unique to them including the carboxysomes, lipid bodies, polyhydroxybutyrate granules.


Relate the forms of different cell structures to their functions. Compare and contrast the structure and function of organelles found in animal and plant cells. Page 2.


A tour of the cell

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Eukaryotic cell structure and function pdf Prokaryotic versus eukaryotic cells y y. Structural and functional organization of eukaryotic cells. Overview of model. What do you call the small structures in eukaryotic cells that carry out specific functions? What is the function of the nucleus? Keywords: cell theory, cell diversity, eukaryote cell structure, nucleus. Amongst eukaryotic cells, as well as to look at the general structural and functional.

At this point, it should be clear that eukaryotic cells have a more complex structure than do prokaryotic cells. Organelles allow for various functions to occur in the cell at the same time. Before discussing the functions of organelles within a eukaryotic cell, let us first examine two important components of the cell: the plasma membrane and the cytoplasm. What structures does a plant cell have that an animal cell does not have? What structures does an animal cell have that a plant cell does not have? Like prokaryotes, eukaryotic cells have a plasma membrane Figure 2 made up of a phospholipid bilayer with embedded proteins that separates the internal contents of the cell from its surrounding environment.

Anyone can learn for free on OpenLearn, but signing-up will give you access to your personal learning profile and record of achievements that you earn while you study. Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available. In eukaryotic cells many activities are compartmentalised within the organelles. The different organelles serve different functions, although in fact each type of organelle e. Some activities, for example the production and processing of proteins, involve different parts of the cell, or several organelles, as you will see.

Section Summary

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Abby D. 27.12.2020 at 00:12

Identify the three filaments that make up the cytoskeleton of eukaryotic cells and describe their functions. Page The Cytoplasm of Eukaryotes. • Consists of​.

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