Cell Organelle Study

Lysosomes

Definition: an organelle in the cytoplasm of eukaryotic cells containing degradative enzymes enclosed in a membrane. Function: Inside a cell, numerous organelles function to remove wastes. One of the key organelles involved in digestion and waste removal is the lysosome. Lysosomes are organelles that contain digestive enzymes. They digest excess or worn out organelles, food particles, and engulfed viruses or bacteria.

Cellulose in cells

Definition: A complex carbohydrate that forms the main constituent of the cell wall in most plants and is important in the manufacture of numerous products, such as paper, textiles, pharmaceuticals, and explosives. (organic chemistry) A polysaccharide containing many glucose units in parallel chains. Function: Cellulose is a very important polysaccharide because it is the most abundant organic compound on earth. Cellulose is a major component of tough cell walls that surround plant cells, and is what makes plant stems, leaves, and branches so strong. Connecting cells to form tissues.

Nuclear Membrane

Definition: A nuclear membrane, also known as the nuclear envelope, is the lipid bilayer membrane which surrounds the genetic material and nucleolus in eukaryotic cells. The nuclear membrane consists of two lipid bilayers—the inner nuclear membrane, and the outer nuclear membrane. Function: The nuclear membrane, sometimes referred to as the nuclear envelope, is the membrane that encloses the nucleus. This bilayer membrane is made of lipids, and encases the genetic material in eukaryotic cells. The nuclear membrane is made up of a double lipid bilayer.

Primary Cell Wall

Definition: A thin, flexible and extensible layer of the cell wall composed of cellulose, pectin and hemicellulose. Supplement. The primary cell wall is the part or layer of cell wall in which cell growth is permitted. Function: The plant cell wall is composed of cellulose. Cellulose is a structural carbohydrate and is considered a complex sugar because it is used in both protection and structure. The plant cell wall consists of three layers. Each layer has its own unique structure and function.

Chromoplast

Definition: An organelle containing any plant pigment other than chlorophyll. The pigments may be yellow, orange, or red. Chromoplasts are usually most numerous in the cells of flowers. Function: Chromoplasts are found in fruits, flowers, roots, and stressed and aging leaves, and are responsible for their distinctive colors. This is always associated with a massive increase in the accumulation of carotenoid pigments. The conversion of chloroplasts to chromoplasts in ripening is a classic example.

Cilia

Definition: Minute hairlike organelles, identical in structure to flagella, that line the surfaces of certain cells and beat in rhythmic waves, providing locomotion to ciliate protozoans and moving liquids along internal epithelial tissue in animals. Function: Cilia and flagella move liquid past the surface of the cell. For single cells, such as sperm, this enables them to swim. For cells anchored in a tissue, like the epithelial cells lining our air passages, this moves liquid over the surface of the cell (e.g., driving particle-laden mucus toward the throat).

Chloroplast

Definition: The combination of two biological terms, plastid (an organelle in a plant cell), and chloros, which means green. If you're reading about plant biology, you'll probably recognize chloros in chlorophyll, which is one of the pigments important to photosynthesis, which takes place in chloroplasts. Function: The organelles are only found in plant cells and some protists such as algae. Chloroplasts work to convert light energy of the Sun into sugars that can be used by cells. The entire process is called photosynthesis and it all depends on the little green chlorophyll molecules in each chloroplast.

Nuclear Pores

Definition: The nuclear pore is a protein-lined channel in the nuclear envelope that regulates the transportation of molecules between the nucleus and the cytoplasm. In eukaryotic cells, the nucleus is separated from the cytoplasm and surrounded by a nuclear envelope. Function: Nuclear pore complexes allow the transport of molecules across the nuclear envelope. This transport includes RNA and ribosomal proteins moving from nucleus to the cytoplasm and proteins (such as DNA polymerase and lamins), carbohydrates, signaling molecules and lipids moving into the nucleus.

Chromosomes/Chromatin

Definition: The primary protein components of chromatin are histones that compact the DNA. Chromatin is only found in eukaryotic cells (cells with defined nuclei). Prokaryotic cells have a different organization of their DNA (the prokaryotic chromosome equivalent is called genophore and is localized within the nucleoid region). Function: The function of chromatin is to efficiently package DNA into a small volume to fit into the nucleus of a cell and protect the DNA structure and sequence. Packaging DNA into chromatin allows for mitosis and meiosis, prevents chromosome breakage and controls gene expression and DNA replication.

Secondary Cell Wall

Definition: The secondary cell wall is a structure found in many plant cells, located between the primary cell wall and the plasma membrane. The cell starts producing the secondary cell wall after the primary cell wall is complete and the cell has stopped expanding. Function: When the cell stops from expanding, a secondary wall is deposited between the primary cell wall and plasma membrane that renders support, strength and protection. The secondary cell wall consists mainly of cellulose, but also other polysaccharides, lignin and proteins.

Water Vacuoles

Definition: a cavity within the cytoplasm of a cell, surrounded by a single membrane and containing fluid, food, or metabolic waste. Vacuoles are found in the cells of plants, protists, and some primitive animals. Function: a vacuole is usually found in all plant and fungal cells, as well as some cells of protists, animals, and bacteria. These membrane-bound structures are basically just enclosed compartments thatare filled with both inorganic and organic molecules, along with water to support the organelle.

Golgi Apparatus

Definition: a complex of vesicles and folded membranes within the cytoplasm of most eukaryotic cells, involved in secretion and intracellular transport. Function: to process and bundle macromolecules like proteins and lipids as they are synthesized within the cell.

Nucleus

Definition: a dense organelle present in most eukaryotic cells, typically a single rounded structure bounded by a double membrane, containing the genetic material. Function: The nucleus is an organelle found in eukaryotic cells. Inside its fully-enclosed nuclear membrane, it contains the majority of the cell's genetic material. This material is organized as DNA molecules, along with a variety of proteins, to form chromosomes.

Plasma/Cell Membrane

Definition: a microscopic membrane of lipids and proteins that forms the external boundary of the cytoplasm of a cell or encloses a vacuole, and that regulates the passage of molecules in and out of the cytoplasm. Function: The primary function of the plasma membrane is to protect the cell from its surroundings. Composed of a phospholipid bilayer with embedded proteins, the plasma membrane is selectively permeable to ions and organic molecules and regulates the movement of substances in and out of cells

Plastids

Definition: any of a class of small organelles, such as chloroplasts, in the cytoplasm of plant cells, containing pigment or food. Function: Plastids are the site of manufacture and storage of important chemical compounds used by the cell. They often contain pigments used in photosynthesis, and the types of pigments in a plastid determine the cell's color.

Cytoskeleton

Definition: a microscopic network of protein filaments and tubules in the cytoplasm of many living cells, giving them shape and coherence. Function: As the name implies, a cytoskeleton is the frame that gives shape to a cell. Just like in a human being, the skeleton also helps hold all of the organelles (organs, in people) in place. Finally, it also assists in moving materials in and out of the cell. Through a series of intercellular proteins, the cytoskeleton gives a cell its shape, offers support, and facilitates movement through three main components: microfilaments, intermediate filaments, and microtubules. The cytoskeleton helps the cell move in its environment and controls the movement of all of the cell's interior workings.

Microtubules

Definition: a microscopic tubular structure present in numbers in the cytoplasm of cells, sometimes aggregating to form more complex structures. Function: Microtubules are conveyer belts inside the cells. They move vesicles, granules, organelles like mitochondria, and chromosomes via special attachment proteins. They also serve a cytoskeletal role. Structurally, they are linear polymers of tubulin which is a globular protein.

Centrioles

Definition: a minute cylindrical organelle near the nucleus in animal cells, occurring in pairs and involved in the development of spindle fibers in cell division. Function: There are two main functions of centrioles that we will focus on. The main function of the centriole is to help with cell division in animal cells. The centrioles help in the formation of the spindle fibers that separate the chromosomes during cell division (mitosis). Cilia and flagella help the cell move.

Ribosomes

Definition: a minute particle consisting of RNA and associated proteins, found in large numbers in the cytoplasm of living cells. They bind messenger RNA and transfer RNA to synthesize polypeptides and proteins. Function: Ribosomes are a cell structure that makes protein. Protein is needed for many cell functions such as repairing damage or directing chemical processes. Ribosomes can be found floating within the cytoplasm or attached to the endoplasmic reticulum.

Rough Endoplasmic Reticulum

Definition: a network of tubular membranes within the cytoplasm of the cell, occurring either with a smooth surface (smooth endoplasmic reticulum) or studded with ribosomes (rough endoplasmic reticulum) involved in the transport of materials. Function: Rough ER is found throughout the cell but the density is higher near the nucleus and the Golgi apparatus. Ribosomes on the rough endoplasmic reticulum are called 'membrane bound' and are responsible for the assembly of many proteins. This process is called translation.

Smooth Endoplasmic Reticulum

Definition: a network of tubular membranes within the cytoplasm of the cell, occurring either with a smooth surface (smooth endoplasmic reticulum) or studded with ribosomes (rough endoplasmic reticulum) involved in the transport of materials. Function: to make cellular products like hormones and lipids.

Cell Wall

Definition: a rigid layer of polysaccharides lying outside the plasma membrane of the cells of plants, fungi, and bacteria. In the algae and higher plants, it consists mainly of cellulose. Function: The plant cell wall is composed of cellulose. Cellulose is a structural carbohydrate and is considered a complex sugar because it is used in both protection and structure. The plant cell wall consists of three layers. Each layer has its own unique structure and function.

Flagella

Definition: a slender threadlike structure, especially a microscopic whiplike appendage that enables many protozoa, bacteria, spermatozoa, etc., to swim. Function: The primary role of the flagellum is locomotion, but it also often has function as a sensory organelle, being sensitive to chemicals and temperatures outside the cell. Flagella are organelles defined by function rather than structure.

Nucleolus

Definition: a small dense spherical structure in the nucleus of a cell during interphase. Function: The nucleus of many eukaryotic cells contains a structure called a nucleolus. ... The nucleolus takes up around 25% of the volume of the nucleus. This structure is made up of proteins and ribonucleic acids (RNA). Its main function is to rewrite ribosomal RNA (rRNA) and combine it with proteins.

Peroxisomes

Definition: a small organelle that is present in the cytoplasm of many cells and that contains the reducing enzyme catalase and usually some oxidases. Function: Cytoplasm is the gel-like fluid in the cell in which organelles are suspended. Peroxisomes have two functions: break down fatty acids to be used for forming membranes and as fuel for respiration; and transfer hydrogen from compounds to oxygen to create hydrogen peroxide and then convert hydrogen peroxide into water.

Microfilaments

Definition: a small rodlike structure, about 4-7 nanometers in diameter, present in numbers in the cytoplasm of many eukaryotic cells. Function: The Function Of Microfilaments. Microfilaments, or actin filaments, are the thinnest filaments of the cytoskeleton and are found in the cytoplasm of eukaryotic cells. The polymers of these linear filaments are flexible but still strong, resisting crushing and buckling while providing support to the cell.

Vesicles

Definition: a small structure within a cell, or extracellular, consisting of fluid enclosed by a lipid bilayer. Vesicles form naturally during the processes of secretion (exocytosis), uptake (endocytosis) and transport of materials within the cytoplasm. Function: When a cell needs to move a molecule many times, it uses vesicles. Vesicles are cellular organelles that are composed of a lipid bilayer. You can think of vesicles as cellular envelopes that are used to transport materials from one place to another. Vesicles also function in metabolism and enzyme storage as well.

Pseudopodia

Definition: a temporary protrusion of the surface of an amoeboid cell for movement and feeding. Function: The functions of pseudopodia include locomotion and the capturing of prey. Pseudopodia are critical in sensing prey that can then be engulfed; the engulfing pseudopodia are called phagocytosis pseudopodia. A common example of this sort of amoeboid cell is the human white blood cell. ... Lobopodia are bulbous and amoebic.

Food Vacuoles

Definition: a vacuole with a digestive function in the protoplasm of a protozoan. Function: a membrane-enclosed cell vacuole with a digestive function, containing material taken up in by the process of phagocytosis. These are found in amoeba, protozoa, paramecium.

Organelle

Definition: any of a number of organized or specialized structures within a living cell. Function: Organelles and Their Functions. The nucleus is arguably the most important organelle in the cell. It is the control center, telling all of the other organelles what to do and when to do it.

Intermediate Filaments

Definition: are cytoskeletal components found in the cells of vertebrate animal species, and perhaps also in other animals, fungi, plants, and unicellular organisms. They are composed of a family of related proteins sharing common structural and sequence features. Function: Perhaps the most important function of intermediate filaments is to provide mechanical support for the plasma membrane where it comes into contact with other cells or with the extracellular matrix. Unlike microfilaments and microtubules, intermediate filaments do not participate in cell motility.

Mitochondria

Defintion: an organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur. It has a double membrane, the inner layer being folded inward to form layers (cristae). Function: The most prominent roles of mitochondria are to produce the energy currency of the cell, ATP (i.e., phosphorylation of ADP), through respiration, and to regulate cellular metabolism. The central set of reactions involved in ATP production are collectively known as the citric acid cycle, or the Krebs cycle.