BIOL 605: Review of Cellular Organelles

Golgi Apparatus/ Body/ Complex

(mostly present in eukaryotic cells) which is responsible for the packaging of macromolecules into vesicles so that they can be sent out to their site of action.

Nucleus

-a double membrane-bound structure responsible for controlling all cellular activities as well as a center for genetic materials, and it's transferring. -one of the large cell organelles occupying 10% of total space in the cell. -often termed the "brain of the cell" as it provides commands for the proper functioning of other cell organelles. -clearly defined in the case of a eukaryotic cell; however, it is absent in prokaryotic organisms with the genetic material distributed in the cytoplasm

Microvilli Structure

-bundles of protuberances loosely arranged on the surface of the cell with little or no cellular organelles. -surrounded by a plasma membrane enclosing cytoplasm and microfilaments. -bundles of actin filaments bound by fimbrin, villin, and epsin.

Peroxisome Structure

-compartments within every peroxisome allow the creation of optimized conditions for different metabolic activities. They consist of several types of enzymes with major groups being urate oxidase, D-amino acid oxidase, and catalase

Peroxisomes

-consists of a single membrane and granular matrix scattered in the cytoplasm. -exist either in the form of interconnected tubules or as individual peroxisomes.

ER Function

-contains many of the enzymes required for several metabolic processes, and the surface of the ER is essential for other operations like diffusion, osmosis, and active transport. -synthesis of lipids like cholesterol and steroids. RER allows for the modification of polypeptides emerging out of the ribosomes to prepare secondary and tertiary structures of the protein. -ER also synthesizes various membrane proteins and has a crucial role in preparing the nuclear envelope after cell division -SER associated with post translational modifications

Mitochondrion Structure

-contains two membranes with the outer layer being smooth while the inner layer is marked with folding and finger-like structures called cristae. -The inner mitochondrial membrane contains various enzymes, coenzymes, and components of multiple cycles along with pores for the transport of substrates, ATP, and phosphate molecules. -Within the membranes is a matrix that contains various enzymes of metabolic processes like Kreb's cycle. -In addition to these enzymes, mitochondria are also home to single or double-stranded DNA called mtDNA that is capable of producing 10% of the proteins present in the mitochondria.

Golgi function

-has an essential purpose of directing proteins and lipids to their destination and thus, act as the "traffic police" of the cell. -involved in the exocytosis of various products and proteins like zymogen, mucus, lactoprotein, and parts of the thyroid hormone. -involved in the synthesis of other cell organelles like a cell membrane, lysozymes, among others. -involved in the sulfation (adding sulfur) of various molecules.

Microvilli Functions

-increase the surface area of the cell, thus, enhancing the absorption and secretion functions. -The membrane of microvilli is packed with enzymes that allow the break down of larger molecules into smaller allowing more effective absorption. -act as an anchoring agent in white blood cells and in sperms during fertilization

Nucleus Function

-responsible for storage as well as the transfer of genetic materials in the form of DNA or RNA. -aids in the process of transcription by the synthesis of mRNA molecules. -controls the activity of all other organelles while facilitating processes like cell growth, cell division and synthesis of proteins.

Mitochondria Function

-synthesis of energy in the form of ATP required for the proper functioning of all the cell organelles. -help in balancing the amount of Ca+ ions within the cell and assists the process of apoptosis. -Different segments of hormones and components of blood are built within mitochondria. -Mitochondria in the liver have the ability to detoxify ammonia.

Plant Cell Wall Composition

A cell wall is multilayered with a middle lamina, a primary cell wall, and a secondary cell wall

Cytoskeleton

A number of fibrous structures are present in the cytosol that helps give shape to the cell while supporting cellular transport.

Plasmodesmata Layers

A plasmodesma has three layers: -The plasmodesmata is continuous with the plasma membrane of the cell and has the same phospholipid bilayer. -The cytoplasmic sleeve that is continuous with the cytosol that allows the exchange of materials between two cells. -Desmotubule which is a part of the endoplasmic reticulum that provides a network between two cells and allows the transport of some molecules.

Chloroplast

A type of plastid found in cells of plants and some other organisms (ie algae) that captures the energy from sunlight and converts it into chemical energy

Cell Wall

An additional non-living layer present outside the cell membrane in some cells (ie plant or bacteria) that provides structure, protection, and filtering mechanism to the cell

Plastid Function

Chloroplasts are the center for many metabolic activities, including photosynthesis as it contains enzymes and other components required for it. They are also involved in the storage of food, primarily starch.

Structure of Cell Membrane

Consists of a lipid bilayer with proteins embedded throughout. The lipid bilayer gives tough, flexible structure that forms a strong barrier. Proteins are made of many different kinds of chains of carbohydrates attached to the outer surface of proteins. Proteins form pumps and channels to help materials move into and out of the cell.

Primary Cell Wall

Made of cellulose

Secondary Cell Wall

Made of cellulose and hemicellulose

Function of Storage Granule

Many prokaryotes and eukaryotes store nutrients and reserves in the form of storage granules in the cytoplasm. Sulfur granules are characteristic of prokaryotes that utilize hydrogen sulfide as a source of energy.

Function of Cytoplasm

Most of the vital cellular and enzymatic reactions like cellular respiration and translation of mRNA into proteins occur in the cytoplasm. It acts as a buffer and protects genetic materials as well as other organelles from damage due to collision or change in the pH of the cytosol

Cell Wall Composition

Plant: Cellulose, Hemicellulose, and proteins Fungi: Chitin Bacteria: Peptidoglycan

Functions of Cellular Membrane

Protection, support, communication and passage of substances into and out of the cell.

Other roles of Cilia

Some cilia present in some particular organs may have the function of sense. The cilium in the blood vessels, which helps in controlling the flow of blood is an example.

Rough ER

Studded with ribosomes attached on the cytosolic face of Endoplasmic Reticulum and thus is involved in protein synthesis

Chloroplast Function

The chloroplast is the primary center for light-dependent and light-independent reactions during photosynthesis. Different proteins present in chlorophyll are involved in the regulation of photorespiration

Cytoplasmic Streaming

The motion of cytoplasm in a cell that results in a coordinated movement of the cell's contents. This process helps in the distribution of various nutrients and facilitates the movement of cell organelles within the cell

Eukaryotic Ribosomal Structure

The ribonucleoprotein consists of two subunits. Eukaryotic cells have 80S ribosomes with 60S larger subunit and 40S smaller subunit. Ribosomes are short-lived as after the protein synthesis, the subunits split up and can be either reused or remain broken up.

Prokaryotic Ribosomal Structure

The ribonucleoprotein consists of two subunits. In the case of prokaryotic cells, the ribosomes are of the 70S with the larger subunit of 50S and the smaller one of 30S. Ribosomes are short-lived as after the protein synthesis, the subunits split up and can be either reused or remain broken up.

Plasmodesmata structure

There are 103 - 105 number of plasmodesmata connecting two adjacent cells with 50-60 nm in diameter. A plasmodesma has three layers: The plasma membrane, The cytoplasmic sleeve, The Desmotubul

Storage Granule Structure

These granules are surrounded by a lipid bilayer and are composed mostly of phosphorus and oxygen. The components inside these storage granules depend on their location in the body with some even containing degradative enzymes yet to participate in digestive activities.

Function of Lysosomes

These organelles are responsible for intracellular digestion where the larger macromolecules are degraded into smaller molecules with the help of enzymes present in them. Lysozymes also perform the critical function of the autolysis of unwanted organelles within the cytoplasm. Besides these, the lysosome is involved in various cellular processes, including secretion, plasma membrane repair, cell signaling, and energy metabolism.

Phospholipid

a lipid that contains phosphorus and that is a structural component in cell membranes

Vacuole Function

act as a storage for nutrients as well as waste materials to protect the cell for toxicity. They have an essential function of homeostasis as it allows the balance of pH of the cell by influx and outflow of H+ ions to the cytoplasm. Vacuoles contain enzymes that play an important role in different metabolic processes.

Microfilaments

aka "actin filaments", protein filaments in the form of parallel polymers in the cytoplasm of eukaryotic cells that form part of the cytoskeleton. -filaments are present either in cross-linked forming networks or as bundles. The chains of protein remain twisted around each other in a helical arrangement. One of the polar ends of the filament is positively charged and barbed, whereas the other end is negatively charged and pointed. -primarily composed of polymers of actin, but are modified by and interact with numerous other proteins in the cell. -generates the strength for the structure and movement of the cell in association with myosin protein. They help in cell division and are involved in the products of various cell surface projections. [~7 nm]

Function of Endosomes

allow the sorting and delivery of internalized materials from the cell surface and transport of materials to the Golgi or the lysosomes

Embedded proteins

are associated with only the interior/cytoplasmic or exterior/extracellular surface of the cell

Gram-Negative Bacterial Cell Walls

cell wall is not as thick because it contains a much lower percentage of peptidoglycan. The gram-negative bacterial cell wall also contains an outer layer of lipopolysaccharides (LPS)

Parts of the Endoplasmic Reticulum

cisternae, vesicles, and tubules

Intermediate filaments

composed of a variety of proteins that are expressed in different types of cells. The individual filaments are coiled around each other in a helical structure called coiled-coil structure. -contribute to the structural integrity of a cell while playing a crucial role in holding tissues of various organs like the skin. [~10 nm]

Centriole

consists of a cylindrical structure made with nine triplets microtubules that surround the periphery of the centriole while the center has a Y-shaped linker and a barrel-like structure that stabilizes the centriole.

Cytoplasm

consists of a cytosol; a gel-like substance that contains other matter; cell organelles; smaller cell-like bodies bound by separate membranes; and cytoplasmic inclusions; insoluble molecules that store energy and are not surrounded by any layer. The cytoplasm is colorless and has about 80% water along with various nutrients required for the cell. It is known to have the properties of both viscous matters as well as elastic matter. Under its elasticity, cytoplasm helps in the movement of materials inside the cell by a process termed cytoplasmic streaming.

Cell Membrane/ Plasma membrane/ Plasmalemma

consists of lipids and proteins where the composition may fluctuate based on fluidity, external environment, and different stages of cell development

Chromatin

contains RNA or DNA along with nuclear proteins, as genetic material that is responsible for carrying the genetic information from one generation to another. It is present in a sense and compact structure which might be visible as chromosome under powerful magnification.

Vesicles Structure

contains liquid or cytosol which is enclosed by a lipid bilayer. The outer layer enclosing the liquid is called a lamellar phase which is similar to the plasma membrane. One end of the lipid bilayer it hydrophobic whereas the other end is hydrophilic.

Middle Lamina

contains polysaccharides that provide adhesion and allows binding of the cells to one another

Gram-Positive Bacteria Cell Wall

contains several layers of peptidoglycan. These stacked layers increase the thickness of the cell wall

Mitochondria

double membrane-bound cell organelles responsible for the supply and storage of energy for the cell. The oxidation of various substrates in the cell to release energy in the form of ATP (Adenosine Triphosphate) is the primary purpose of mitochondria.

Plastid

double membrane-bound structures present in plants and other eukaryotes involved in the synthesis and storage of food.

Chloroplast structure

double-membraned structure with its own cpDNA which is inherited from the previous chloroplast. These are usually lens-shaped with shape and number varying according to cells. They have an outer membrane, an inner membrane, and a thylakoid membrane that enclosed the gel-like matrix called the stroma. The outer and inner membrane is porous and allows transport of materials while the stroma contains DNA, chloroplast ribosomes, proteins, and starch granules.

Endosome Structure

early endosomes are made with the tubular-vesicular network while the late endosomes lack tubules but contain many close-packed intraluminal vesicles. The recycling endosomes are found with microtubules and are mainly composed of tubular structures.

Vescicle Function

facilitate the storage and transport of materials in and outside the cell. It even allows the exchange of molecules between two cells. Because vesicles are enclosed inside a lipid bilayer, vesicles also function in metabolism and enzyme storage. They allow temporary storage of food and also control the buoyancy of the cell.

Flagella

filamentous organelle, the structure of which, is different in prokaryotes and eukaryotes

Cilia

hair-like projections that have a 9+2 arrangement of microtubules with a radial pattern of 9 outer microtubule doublet that surrounds two singlet microtubules. This arrangement is attached to the bottom with a basal body

Smooth ER

has a function during lipid synthesis

Function of Centriole

have a crucial role in forming spindle fibers which assist the movement of chromatids towards their respective sides, they are involved in the formation of cilia and flagella

Peroxisome function

involved in the production and elimination of hydrogen peroxide during biochemical processes. Oxidation of fatty acids takes place within peroxisomes. Additionally, peroxisomes are also involved in the synthesis of lipid-like cholesterol and plasmalogens.

Prokaryotic Flagella

it is made up of the protein called flagellin wrapped around in a helical manner creating a hollow structure at the center throughout the length

Nucleolus

like a nucleus within the nucleus. It is a membrane-less organelle that is responsible for the synthesis of rRNA and assembly of ribosomes required for protein synthesis.

Structure of Golgi Apparatus

like the ER, the golgi is composed of three forms, the cisternae, vesicles, and tubules. -cisternae, which is the smallest unit of Golgi Complex, has a flattened sac-like structure which is arranged in bundles in a parallel fashion. -Tubules are present as tubular and branched structures that radiate from the cisternae and are fenestrated at the periphery. -Vesicles are spherical bodies that are divided into three groups as transitional vesicles, secretory vesicles, and clathrin-coated vesicles.

LPS

lipopolysaccharide layer surrounds the peptidoglycan layer and acts as an endotoxin (poison) in pathogenic bacteria (disease causing bacteria). The LPS layer also protects gram-negative bacteria against certain antibiotics, such as penicillins.

Microtubules

long, hollow polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. wall of the microtubules consists of globular subunits present at a helical array of a and b tubulin. Similar to microfilaments, the ends of microtubules also have a defined polarity with one end being positively charged while the other being negatively charged [~25nm]

Endosomes

membrane-bound compartments within a cell originating from the Golgi network

Storage Granules

membrane-bound organelles, also called zymogen granules storing cell's energy reserve and other metabolites.

Vacuole

membrane-bound structures varying in size in cells of different organisms

Cytoskeleton composition

microtubules, microfilaments, and intermediate filaments. These are separated based on a protein present in them.

Function of Cilia and Flagella

most critical role of cilia and flagella is movement. These are responsible for the movement of the organisms as well as for the movement of various particles present around the organisms

Lysosome

occur in the cytoplasm of animal cells contain an array of hydrolytic enzymes required for the degradation of various macromolecules. -two types of lysozymes: Primary lysosome containing hydrolytic enzymes like lipases, amylases, proteases, and nucleases. Secondary lysosome formed by the fusion of primary lysozymes containing engulfed molecules or organelles.

Endoplasmic Reticulum (ER)

present as an interconnection of tubules that are connected to the nuclear membrane in eukaryotic cells. Two types: RER and SER

Cartwheel

present in a centriole which is made up of a central hub with nine spokes/filaments radiating from it. Each of these filaments/spokes is connected to the microtubules through a pinhead

Plasmodesmata Funciton

primary site for the communication of two cells. It allows the transfer of molecules like proteins, RNA, and viral genomes.

Functions of Cell Wall

protecting and maintaining the shape of the cell. It also helps the cell withstand the turgor pressure of the cell, Initiates cell division by providing signals to the cell and allows the passage of some molecules into the cell while blocking others.

Ribosomes

ribonucleoprotein containing equal parts RNA and proteins along with an array of other essential components required for protein synthesis. In prokaryotes, they exist freely while in eukaryotes, they are found either free or attached to the endoplasmic reticulum.

Cisternae

sac-like flattened, unbranched structures that remain stacked one on top of another

Lysosome Structure

shape is irregular/pleomorphic; however, mostly, they are found in the spherical or granular structure. Lysosomes are surrounded by a lysosomal membrane that contains the enzymes (lysozyme) within the lysosome and protects the cytosol with the rest of the cell from the harmful action of the enzymes.

Nuclear Envelope

similar to the cell membrane in structure and composition. It has pores that allow the movement of proteins and RNA in and outside the nucleus. It enables the interaction with other cell organelles while keeping nucleoplasm and chromatin within the envelope

Ribosome Function

site of biological protein synthesis in all living organisms. They arrange the amino acids in the order indicated by tRNA and assist in protein synthesis.

Cell Organelles

specialized cell structures characterized as very small and responsible for specific cell activity found in cytoplasm Typically enclosed by a biological membrane, could be single or double membrane (mitochondria, chloroplast, nucleus)

Vesicles

spherical structures that carry proteins throughout the cell structures present inside the cell which are either formed naturally during processes like exocytosis, endocytosis or transport of materials throughout the cell, or they might form artificially, which are called liposomes. There are different types of vesicles like vacuoles, secretory and transport vesicles based on their function

Vacuole Structure

surrounded by a membrane called tonoplast, which encloses fluid containing inorganic materials like water and organic materials like nutrients and even enzymes. These are formed by the fusion of various vesicles, so vacuoles are very similar to vesicles in structure.

Nucleus Structure

the nucleus consists of a nuclear envelope, chromatin, and nucleolus.

Eukaryotic Flagella

the protein flagellin is absent and the structure is replaced with microtubules.

Microvilli

tiny finger-like structures that project on or out of the cells. These exist either on their own or in conjunction with villi.

Cilia and Flagella

tiny hair-like projections from the cell made of microtubules and covered by the plasma membrane

Plasmodesmata

tiny passages or channels that allow the transfer of material and communication between different cells.

Function of cytoskeleton

to provide shape and mechanical support to the cell against deformation. It allows the expansion and contraction of the cell which assists in the movement of the cell. It is also involved in intracellular and extracellular transport of materials.

Tubules

tubular branched structures forming a connection between cisternae and vesicles.

Peptidoglycan

unique to bacterial cell wall composition, a polymer composed of double-sugars and amino acids (protein subunits)

Plastid Structure

usually oval or spherical with an outer and an inner membrane between which lies the intermembrane space. -The inner membrane enclosed a matrix called stroma that contains small structures called grana. -Each granum consists of several sac-like thylakoids piled one on the other and connected by stroma lamellae. -Plastids contain DNA and RNA that allows it to synthesize necessary proteins for different processes.