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How do plant cell vacuoles form?

How do plant cell vacuoles form?


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Does the plant cell vacuole form by the invagination of the cell membrane?


Does the plant cell vacuole form by the invagination of the cell membrane?

Yes, in part, but the complete answer is way more complicated than that.

Endosomes (the vesicles formed by "invagination" of the cell membrane, as you said) are responsible for (part) of the biomembrane of the cell vacuole. However, some biomembrane comes from the Golgi-ER system, and almost all proteins come from ER (having passed by the Golgi apparatus).

Have a look at this image (Marty, 1999):

Its legend says:

Seven basic pathways are used for the biogenesis, maintenance, and supplying of vacuoles. Pathway 1: entry and transport in the early secretory pathway (from ER to late Golgi compartments). Pathway 2: sorting of vacuolar proteins in the trans-Golgi network (TGN) to a pre/provacuolar compartment (PVC) via an early biosynthetic vacuolar pathway. Pathway 3: transport from PVC to vacuole via the late biosynthetic vacuolar pathway. Pathway 4: transport from early secretory steps (ER to Golgi complex; pathway 1) to the vacuole via an alternative route with possible material accretion from Golgi (indicated by the asterisk). Pathway 5: endocytotic pathway from the cell surface to the vacuole via endosomes. Pathway 6: cytoplasm to vacuole through autophagy by degradative or biosynthetic pathways. Pathway 7: transport of ions and solutes across the tonoplast. AV, autophagic vacuole; E, early endosome; ER, endoplasmic reticulum; PVC, pre/provacuolar compartment; TGN, trans-Golgi network.

According to the same paper (Marty, 1999):

Experimental evidence suggests that material within the vacuolar system in plants derives confluently from both an intracellular biosynthetic pathway and a coordinated endocytotic pathway. (emphases mine)


Source: Marty, F. (1999). Plant Vacuoles. THE PLANT CELL ONLINE, 11(4), pp.587-600.


Cell Plate

The cell plate is a structure that forms in the cells of land plants while they are undergoing cell division.

The cells of land plants, unlike animal cells, have a cell wall made of stiff sugars which surround their cell membranes. In addition to protecting the cell from damage, the cell walls help to maintain the plant’s rigid upright structures, such as leaves and stems.

These rigid support structures allow plants to grow tall and spread their leaves wide, obtaining more sunlight. In most plants, the cell wall is made of cellulose – an arrangement of glucose molecules that forms hard, rigid surfaces.

Interestingly, the cellulose that makes up cell walls is not digestible to humans or animals – but it can be broken down into sugar by some methane-producing archaebacteria. This is one reason for the symbiotic relationship between many animals and the archaebacteria in our gut.

During cell division, plant cells must form a new cell wall to separate their daughter cells. This new fragment of cell wall must form in the middle of the parent cell, to ensure that half of the parent cells’ chloroplasts, gene copies, etc. end up on each side of the cell wall.

The “plate” of hard sugars that forms in the middle of the parent cell, which will become the cell wall of the future daughter cells, is called the cell plate.


Plant Cells

Plant cells resemble other eukaryotic cells in many ways. For example, they are enclosed by a plasma membrane and have a nucleus and other membrane-bound organelles. A typical plant cell is represented by the diagram in Figure below.

Plant cells have all the same structures as animal cells, plus some additional structures. Can you identify the unique plant structures in the diagram?

Plant Cell Structures

Structures found in plant cells but not animal cells include a large central vacuole, cell wall, and plastids such as chloroplasts.

  • The large central vacuole is surrounded by its own membrane and contains water and dissolved substances. Its primary role is to maintain pressure against the inside of the cell wall, giving the cell shape and helping to support the plant.
  • The cell wall is located outside the cell membrane. It consists mainly of cellulose and may also contain lignin, which makes it more rigid. The cell wall shapes, supports, and protects the cell. It prevents the cell from absorbing too much water and bursting. It also keeps large, damaging molecules out of the cell.
  • Plastids are membrane-bound organelles with their own DNA. Examples are chloroplastsand chromoplasts. Chloroplasts contain the green pigment chlorophyll and carry out photosynthesis. Chromoplasts make and store other pigments. They give flower petals their bright colors.

Types of Plant Cells

There are three basic types of cells in most plants. These cells make up ground tissue, which will be discussed in another concept. The three types of cells are described in Table below. The different types of plant cells have different structures and functions.


Plant cell

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Plant cell, the basic unit of all plants. Plant cells, like animal cells, are eukaryotic, meaning they have a membrane-bound nucleus and organelles. The following is a brief survey of some of the major characteristics of plant cells. For a more in-depth discussion of cells, see cell.

Unlike animal cells, plant cells have a cell wall surrounding the cell membrane. Although often perceived as an inactive product serving mainly mechanical and structural purposes, the cell wall actually has a multitude of functions upon which plant life depends. Plant cell walls are composed of cellulose, which sets them apart from other organisms with cell walls, such as bacteria (peptidoglycan) and fungi (chitin). Algal cell walls are similar to those of plants, and many contain specific polysaccharides that are useful for taxonomy.

Plant cells can be distinguished from most other cells by the presence of chloroplasts, which are also found in certain algae. A chloroplast is a type of plastid (a saclike organelle with a double membrane) that serves as the site of photosynthesis, the process by which energy from the Sun is converted into chemical energy for growth. Chloroplasts contain the pigment chlorophyll to absorb light energy. In plants, these essential organelles occur in all green tissues, though they are concentrated particularly in the parenchyma cells of leaves.

Another important characteristic of many plant cells is the presence of one or more large vacuoles. Vacuoles are storage organelles, and those in plant cells enable them to attain a large size without accumulating the bulk that would make metabolism difficult. Within the vacuole is the cell sap, a water solution of salts and sugars kept at high concentration by the active transport of ions through the vacuole membrane. Proton pumps also maintain high concentrations of protons in the vacuole interior. These high concentrations cause the entry, via osmosis, of water into the vacuole, which in turn expands the vacuole and generates a hydrostatic pressure, called turgor, that presses the cell membrane against the cell wall. Turgor is the cause of rigidity in living plant tissue. In a mature plant cell, as much as 90 percent of cell volume may be taken up by a single vacuole immature cells typically contain several smaller vacuoles.


Other Organelles

In addition to the nucleus, eukaryotic cells have many other organelles, including the endoplasmic reticulum, Golgi apparatus, vesicles, vacuoles, and centrioles.

Endoplasmic Reticulum

The endoplasmic reticulum (ER) (plural, reticuli) is a network of phospholipid membranes that form hollow tubes, flattened sheets, and round sacs. These flattened, hollow folds and sacs are called cisternae. The ER has two major functions:

  • Transport: Molecules, such as proteins, can move from place to place inside the ER, much like on an intracellular highway.
  • Synthesis: Ribosomes that are attached to ER, similar to unattached ribosomes, make proteins. Lipids are also produced in the ER.

There are two types of endoplasmic reticulum, rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER).

  • Rough endoplasmic reticulum is studded with ribosomes, which gives it a "rough" appearance. These ribosomes make proteins that are then transported from the ER in small sacs called transport vesicles. The transport vesicles pinch off the ends of the ER. The rough endoplasmic reticulum works with the Golgi apparatus to move new proteins to their proper destinations in the cell. The membrane of the RER is continuous with the outer layer of the nuclear envelope.
  • Smooth endoplasmic reticulum does not have any ribosomes attached to it, and so it has a smooth appearance. SER has many different functions, some of which include lipid synthesis, calcium ion storage, and drug detoxification. Smooth endoplasmic reticulum is found in both animal and plant cells and it serves different functions in each. The SER is made up of tubules and vesicles that branch out to form a network. In some cells there are dilated areas like the sacs of RER. Smooth endoplasmic reticulum and RER form an interconnected network.

Image of nucleus, endoplasmic reticulum and Golgi apparatus, and how they work together. The process of secretion from endoplasmic reticuli to Golgi apparatus is shown.

Golgi Apparatus

The Golgi apparatus is a large organelle that is usually made up of five to eight cup-shaped, membrane-covered discs called cisternae, as shown in Figure above. The cisternae look a bit like a stack of deflated balloons. The Golgi apparatus modifies, sorts, and packages different substances for secretion out of the cell, or for use within the cell. The Golgi apparatus is found close to the nucleus of the cell, where it modifies proteins that have been delivered in transport vesicles from the RER. It is also involved in the transport of lipids around the cell. Pieces of the Golgi membrane pinch off to form vesicles that transport molecules around the cell. The Golgi apparatus can be thought of as similar to a post office it packages and labels "items" and then sends them to different parts of the cell. Both plant and animal cells have a Golgi apparatus. Plant cells can have up to several hundred Golgi stacks scattered throughout the cytoplasm. In plants, the Golgi apparatus contains enzymes that synthesize some of the cell wall polysaccharides.

Vesicles

A vesicle is a small, spherical compartment that is separated from the cytosol by at least one lipid bilayer. Many vesicles are made in the Golgi apparatus and the endoplasmic reticulum, or are made from parts of the cell membrane. Vesicles from the Golgi apparatus can be seen in Figure above. Because it is separated from the cytosol, the space inside the vesicle can be made to be chemically different from the cytosol. Vesicles are basic tools of the cell for organizing metabolism, transport, and storage of molecules. Vesicles are also used as chemical reaction chambers. They can be classified by their contents and function.

  • Transport vesicles are able to move molecules between locations inside the cell. For example, transport vesicles move proteins from the rough endoplasmic reticulum to the Golgi apparatus.
  • Lysosomes are vesicles that are formed by the Golgi apparatus. They contain powerful enzymes that could break down (digest) the cell. Lysosomes break down harmful cell products, waste materials, and cellular debris and then force them out of the cell. They also digest invading organisms such as bacteria. Lysosomes also break down cells that are ready to die, a process called autolysis.
  • Peroxisomes are vesicles that use oxygen to break down toxic substances in the cell. Unlike lysosomes, which are formed by the Golgi apparatus, peroxisomes self-replicate by growing bigger and then dividing. They are common in liver and kidney cells that break down harmful substances. Peroxisomes are named for the hydrogen peroxide (H2O2) that is produced when they break down organic compounds. Hydrogen peroxide is toxic, and in turn is broken down into water (H2O) and oxygen (O2) molecules.

Vacuoles

Vacuoles are membrane-bound organelles that can have secretory, excretory, and storage functions. Many organisms will use vacuoles as storage areas and some plant cells have very large vacuoles. Vesicles are much smaller than vacuoles and function in transporting materials both within and to the outside of the cell.

Centrioles

Centrioles are rod-like structures made of short microtubules. Nine groups of three microtubules make up each centriole. Two perpendicular centrioles make up the centrosome. Centrioles are very important in cellular division, where they arrange the mitotic spindles that pull the chromosome apart during mitosis.


What are Plant Vacuoles

Plant vacuoles refer to a cavity within the cytoplasm, which is covered by a single membrane and contains the cell sap in plant cells. The membrane that surrounds the plant vacuoles is called the tonoplast. These vacuoles mainly contain water and occupy up to 90% of the total volume of the cytoplasm in mature plant cells. These vacuoles also contain mineral salts, sucrose, amino acids, proteins, and waste materials. Plant vacuoles contain water-soluble pigments. The vacuole of a plant cell is shown in figure 1.

Figure 1: Plant Vacuole

The main function of the plant vacuoles is to maintain the turgor pressure of the cell. The plasma membrane of the cell is pushed against the cell wall by the turgor pressure. Plant cells obtain water into their vacuoles through osmosis. Vacuole helps to maintain the shape of the cell during dehydration. They are important for the maintenance of osmotic concentration of the cell. Plant vacuoles that contain digestive enzymes may serve as lysosomes. Dissolved anthocyanin in the epidermal cells of the Rhoeo is shown in figure 2. Anthocyanin is a water-soluble pigment in plant cells.

Figure 2: Anthocyanin in the Rhoeo Vacuoles

One of the most significant roles of the plant vacuoles is the detoxification of heavy metals inside the cell.


Plant Vacuoles

Plant vacuoles are multifunctional organelles. On the one hand, most vegetative tissues develop lytic vacuoles that have a role in degradation. On the other hand, seed cells have two types of storage vacuoles: protein storage vacuoles (PSVs) in endosperm and embryonic cells and metabolite storage vacuoles in seed coats. Vacuolar proteins and metabolites are synthesized on the endoplasmic reticulum and then transported to the vacuoles via Golgi-dependent and Golgi-independent pathways. Proprotein precursors delivered to the vacuoles are converted into their respective mature forms by vacuolar processing enzyme, which also regulates various kinds of programmed cell death in plants. We summarize two types of vacuolar membrane dynamics that occur during defense responses: vacuolar membrane collapse to attack viral pathogens and fusion of vacuolar and plasma membranes to attack bacterial pathogens. We also describe the chemical defense against herbivores brought about by the presence of PSVs in the idioblast myrosin cell.


Functions of a Vacuole

Water Storage

In plants, a large vacuole occupies the majority of the cell. This vacuole is surrounded by the tonoplast, a type of cytoplasmic membrane that can stretch and fills itself with a solution known as cell sap. The vacuole also fill itself with protons from the cytosol, creating an acid environment inside of the cell. The vacuole can then use the chemical gradient created to transport materials in and out of the vacuole, a type of movement called proton motive force. This includes the movement of water and other molecules. The following is a picture of a plant cell, and the vacuole inside.

Turgor Pressure

Plants use their vacuoles for a second function, which is of utmost importance to all plants. The vacuole, when completely filled with water, can become pressurized and exert a force on the cell walls. Although the force in each cell is small, this turgor pressure allows the cells to create a form, and stand up to wind, rain and even hail. Although woody plants create additional proteins and fibers that help them stand tall, many non-woody plants can reach a height of several feet on turgor pressure alone.

Endocytosis and Exocytosis

A vacuole is used whenever a large amount of substance is taken in through endocytosis, or excreted through exocytosis. Many cells, plant and animal, take in substances and must store them separate from the cytosol. This could be because the substances are reactive, in which case they will cause unwanted reactions. It could also be because the substances would interfere with cellular processes because they are two large. Lysosomes are vesicles used to intake substances to be digested. Sometimes these lysosomes can fuse to form a large, digestive vesicle that can digest nutrients in an acid environment, then transfer them to the cytosol or other organelles to be used. This process is endocytosis, and varies among different types of cells.

Going the opposite direction, many cells function as secretory cells, and must produce and excrete large amounts of different substances. The substances are produces in the endoplasmic reticulum, travel to the Golgi apparatus to be modified and labeled for distribution. The substances can then be put into vesicles. The vesicles travel into the cytoplasm and can merge into a larger vacuole before being excreted. This is known as exocytosis. The vacuoles that carry different substances to and fro vary in structure in different cells, and even within cells when they have different functions. An animal cell may contain many vacuoles that preform many functions. An example of an animal cell and its vacuoles can be seen below, the smaller unlabeled sphere would be vesicles. Once they fuse together, they would also be considered vacuoles.

Other Storage Functions

Vacuoles are able to store many different types of molecules. Fat cells, for instance, store huge amounts of lipids in specialized vacuoles. This allows single cells to store a large amount of fat, which organisms can use when resources are low. The expandability of the vacuole means an organism can gain or lose weight without too many cells being created or lost. Other times, vacuoles of organisms are used to create entire ecosystems, in which symbiotic organisms can live. Coral polyps often eat algae through endocytosis, but the algae are allowed to live in vacuoles within the coral. This allows the coral to gain the oxygen and nutrients given off by the algae.


Plant Cell Biology

Plant Cell Biology, Second Edition: From Astronomy to Zoology connects the fundamentals of plant anatomy, plant physiology, plant growth and development, plant taxonomy, plant biochemistry, plant molecular biology, and plant cell biology. It covers all aspects of plant cell biology without emphasizing any one plant, organelle, molecule, or technique. Although most examples are biased towards plants, basic similarities between all living eukaryotic cells (animal and plant) are recognized and used to best illustrate cell processes. This is a must-have reference for scientists with a background in plant anatomy, plant physiology, plant growth and development, plant taxonomy, and more.

Plant Cell Biology, Second Edition: From Astronomy to Zoology connects the fundamentals of plant anatomy, plant physiology, plant growth and development, plant taxonomy, plant biochemistry, plant molecular biology, and plant cell biology. It covers all aspects of plant cell biology without emphasizing any one plant, organelle, molecule, or technique. Although most examples are biased towards plants, basic similarities between all living eukaryotic cells (animal and plant) are recognized and used to best illustrate cell processes. This is a must-have reference for scientists with a background in plant anatomy, plant physiology, plant growth and development, plant taxonomy, and more.


Prokaryotic Cells

Cells come in many shapes and sizes and have different structural features. Bacteria are single-celled organisms approximately 1 to 10 micrometers (.00004 to .0004 inch) in size and can be spherical, rod-shaped, or spiral-shaped. They are known as prokaryotes (from the Greek pro, meaning 𢯯ore" and karyon, meaning "kernel" or "nucleus") because they contain a nucleoid region rather than a true nucleus where their genetic material is found. All bacteria have cell walls that may be surrounded by a capsule and/or a gelatinous slime layer.

Beneath the cell wall is the plasma membrane responsible for regulating the flow of materials into and out of the cell's cytoplasm within the interior of the cell. The cytoplasm is composed of fluid known as cytosol and solid materials. Within the cytosol are ribosomes , granular bodies that direct


Plant Cell Biology

Plant Cell Biology is a semester long course for undergraduates and graduate students which integrates mathematics and physics, two years of chemistry, genetics, biochemistry and evolution disciplines. Having taught this course for over ten years, the author uses his expertise to relate the background established in plant anatomy, plant physiology, plant growth and development, plant taxonomy, plant biochemistry, and plant molecular biology courses to plant cell biology. This integration attempts to break down the barrier so plant cell biology is seen as an entrée into higher science.

Distinguishing this book from papers that are often used for teaching the subject which use a single plant to demonstrate the techniques of molecular biology, this book covers all aspects of plant cell biology without emphasizing any one plant, organelle, molecule, or technique. Although most examples are biased towards plants, basic similarities between all living eukaryotic cells (animal and plant) are recognized and used to best illustrate for students cell processes.

Plant Cell Biology is a semester long course for undergraduates and graduate students which integrates mathematics and physics, two years of chemistry, genetics, biochemistry and evolution disciplines. Having taught this course for over ten years, the author uses his expertise to relate the background established in plant anatomy, plant physiology, plant growth and development, plant taxonomy, plant biochemistry, and plant molecular biology courses to plant cell biology. This integration attempts to break down the barrier so plant cell biology is seen as an entrée into higher science.

Distinguishing this book from papers that are often used for teaching the subject which use a single plant to demonstrate the techniques of molecular biology, this book covers all aspects of plant cell biology without emphasizing any one plant, organelle, molecule, or technique. Although most examples are biased towards plants, basic similarities between all living eukaryotic cells (animal and plant) are recognized and used to best illustrate for students cell processes.

Key Features

  • Thoroughly explains the physiological underpinnings of biological processes to bring original insight related to plants
  • Includes examples throughout from physics, chemistry, geology, and biology to bring understanding to plant cell development, growth, chemistry and diseases
  • Provides the essential tools for students to be able to evaluate and assess the mechanisms involved in cell growth, chromosome motion, membrane trafficking, and energy exchange
  • Companion Web site provides support for all plant cell biology courses

  • Thoroughly explains the physiological underpinnings of biological processes to bring original insight related to plants
  • Includes examples throughout from physics, chemistry, geology, and biology to bring understanding to plant cell development, growth, chemistry and diseases
  • Provides the essential tools for students to be able to evaluate and assess the mechanisms involved in cell growth, chromosome motion, membrane trafficking, and energy exchange
  • Companion Web site provides support for all plant cell biology courses


Watch the video: Austin Visuals 3D Animation Studio. Plant Cell. Explainer Video. Animated Video Company (July 2022).


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