![Plant cells are eukaryotic cells that differ in several key respects from the cells of other
eukaryotic organisms. Their distinctive features include:
A large central vacuole, a water-filled volume enclosed by a membrane known as the
tonoplast[1][2] maintains the cell's turgor, controls movement of molecules between the
cytosol and sap, stores useful material and digests waste proteins and organelles.
A cell wall composed of cellulose and hemicellulose, pectin and in many cases lignin, is
secreted by the protoplast on the outside of the cell membrane. This contrasts with the
cell walls of fungi (which are made of chitin), and of bacteria, which are made of
peptidoglycan.
Specialised cell–cell communication pathways known as plasmodesmata,[3] pores in the
primary cell wall through which the plasmalemma and endoplasmic reticulum[4] of
adjacent cells are continuous.
Plastids, the most notable being the chloroplasts, which contain chlorophyll a green
coloured pigment which is used for absorbing sunlight and is used by a plant to make its
own food in the process is known as photosynthesis. Other types of plastid are the
amyloplasts, specialized for starch storage, elaioplasts specialized for fat storage, and
chromoplasts specialized for synthesis and storage of pigments. As in mitochondria,
which have a genome encoding 37 genes,[5] plastids have their own genomes of about
100–120 unique genes[6] and, it is presumed, arose as prokaryotic endosymbionts living
in the cells of an early eukaryotic ancestor of the land plants and algae.[7]
Cell division by construction of a phragmoplast as a template for building a cell plate late
in cytokinesis is characteristic of land plants and a few groups of algae, notably the
Charophytes[8] and the Order Trentepohliales[9]
The sperm of bryophytes and pteridophytes have flagellae similar to those in
animals,[10][11] but higher plants, (including Gymnosperms and flowering plants) lack the
flagellae and centrioles[12] that are present in animal cells.](https://image.slidesharecdn.com/cellandfunctions-120723045022-phpapp02/85/Cell-and-functions-4-320.jpg)
Cell and functions
- 1. eukaryotic cell A cell that contains membrane-bound compartments in which specific metabolic activities take place. Most important among these compartments is the nucleus, which houses the eukaryotic cell's DNA. It is this nucleus that gives the eukaryote – literally, "true Comparison of a typical eukaryotic cell with a typical prokaryotic cell (bacterium). nucleus" – its name. The drawing on the left highlights the internal structures of eukaryotic cells, Eukaryotic organisms also including the nucleus (light blue), the nucleolus (intermediate blue), mitochondria have other specialized, (orange), and ribosomes (dark blue). The drawing on the right demonstrates how membrane-bounded bacterial DNA is housed in a structure called the nucleoid (very light blue), as well structures, called as other structures normally found in a prokaryotic cell, including the cell organelles, which are membrane (black), the cell wall (intermediate blue), the capsule (orange), small structures within ribosomes (dark blue), and a flagellum (also black). cells that perform dedicated functions. Eukaryotic cells are typically 10 to 100 micrometers across, or about 10 times the size of prokaryotic cells. Origin of eukaryotic cells The set of ideas most favored by biologists to explain how eukaryotic cells first came about is called the endosymbiotic theory. This theory is able to account well for the fact that two of the organelles found in eukaryotic cells, mitochondria and chloroplasts, have their own DNA that is completely distinct from the DNA housed in the nucleus. According to the endosymbiotic theory, the eukaryotic cell evolved from a symbiotic community of prokaryotic cells. Specifically, the mitochondria and the chloroplasts are what remains of ancient symbiotic oxygen-breathing bacteria and cyanobacteria, respectively, whereas the rest of the cell seems to be derived from an ancestral archaean prokaryote cell. The origin of the eukaryotic cell was a milestone in the evolution of life. Although eukaryotes use the same genetic code and metabolic processes as prokaryotes, their higher level of organizational
- 2. complexity has permitted the development of truly multicellular organisms. Without eukaryotes, the world would lack mammals, birds, fish, invertebrates, fungi, plants, and complex single-celled organisms. Comparison of eukaryotic and prokaryotic cells feature eukaryotic cells prokaryotic cells Found in "simple" organisms, types of Found in "complex" organisms, including all plants and animals including bacteria and organism cyanobacteria Can specialize for certain functions, such as absorbing nutrients from food or Usually exist as single, virtually specialization transmitting nerve impulses; groups cells can form large, multicellular organs and identical cells organisms Most animal cells are 10–30 micrometers across; most plant cells are 10–100 size Most are 1–10 micrometers across micrometers across Contain a nucleus and many other organelles, each surrounded by a membrane (the Lack a nucleus and other nucleus nucleus and mitochondrion have two membranes) membrane-encased organelles nucleolus One (or more) present in each nucleus Absent Simple duplex not associated with DNA DNA always in combination with histone proteins histones (i.e. basic proteins)Absent spindle Present temporarily during mitosis and meiosis Absent Complete nuclear fusion between gametes, with equal contributions from both Unidirectional transfer of genes sexual system genomes from donor to recipient Present, but chemically different cell wall Present in plant cells, but never contain muramic acid in many respects from eukaryotes (e.g. presence of muramic acid) internal Complex compartmentalization into endoplasmic reticulum, Golgi bodies, Usually simple and often membranes lysosomes, etc transient, if present at all ribosomes 80 S with subunits (60 S + 40 S) 70 S* with subunits (30 S + 50 S) photosynthesis Complex chloroplasts (membrane-bounded organelles) Simple chromatophores Virtually all forms are aerobic, though a few are faculatively anaerobic (e.g. yeasts); respiration Simple chromatophores and, uniquely, the trichomonads are obligate anerobes electron Found on the inner membrane of special membrane-bound organelles: mitochondria transport (oxidative phosphorylation) and chloroplasts (photophosphorylation). Virtually all Localized on the cell membrane system & ATP forms are aerobic, though a few are faculatively anaerobic (e.g. yeasts); and, synthesis uniquely, the trichomonads are obligate anerobes
- 3. metabolic functions. For example, some Prokaryotic Cells bacteria use sulfur instead of oxygen in their Cells that lack a membrane-bound nucleus are metabolism. called prokaryotes (from the Greek meaning before nuclei). These cells have few internal structures that are distinguishable under a microscope. Cells in the monera kingdom such as bacteria and cyanobacteria (also known as Examples of Prokaryotic Cells blue-green algae) are prokaryotes. Prokaryotic cells differ significantly from eukaryotic cells. They don't have a membrane- bound nucleus and instead of having chromosomal DNA, their genetic information is in a circular loop called a plasmid. Bacterial cells are very small, roughly the size of an animal mitochondrion (about 1-2µm in diameter and 10 µm long). Prokaryotic cells feature three major shapes: rod shaped, spherical, and spiral. Instead of going through elaborate replication processes like eukaryotes, bacterial cells divide by binary fission. Bacteria perform many important functions on earth. They serve as decomposers, agents of fermentation, and play an important role in our own digestive system. Also, bacteria are involved in many nutrient cycles such as the nitrogen cycle, which restores nitrate into the soil for plants. Unlike eukaryotic cells that depend on oxygen for their metabolism, prokaryotic cells enjoy a diverse array of
- 4. Plant cells are eukaryotic cells that differ in several key respects from the cells of other eukaryotic organisms. Their distinctive features include: A large central vacuole, a water-filled volume enclosed by a membrane known as the tonoplast[1][2] maintains the cell's turgor, controls movement of molecules between the cytosol and sap, stores useful material and digests waste proteins and organelles. A cell wall composed of cellulose and hemicellulose, pectin and in many cases lignin, is secreted by the protoplast on the outside of the cell membrane. This contrasts with the cell walls of fungi (which are made of chitin), and of bacteria, which are made of peptidoglycan. Specialised cell–cell communication pathways known as plasmodesmata,[3] pores in the primary cell wall through which the plasmalemma and endoplasmic reticulum[4] of adjacent cells are continuous. Plastids, the most notable being the chloroplasts, which contain chlorophyll a green coloured pigment which is used for absorbing sunlight and is used by a plant to make its own food in the process is known as photosynthesis. Other types of plastid are the amyloplasts, specialized for starch storage, elaioplasts specialized for fat storage, and chromoplasts specialized for synthesis and storage of pigments. As in mitochondria, which have a genome encoding 37 genes,[5] plastids have their own genomes of about 100–120 unique genes[6] and, it is presumed, arose as prokaryotic endosymbionts living in the cells of an early eukaryotic ancestor of the land plants and algae.[7] Cell division by construction of a phragmoplast as a template for building a cell plate late in cytokinesis is characteristic of land plants and a few groups of algae, notably the Charophytes[8] and the Order Trentepohliales[9] The sperm of bryophytes and pteridophytes have flagellae similar to those in animals,[10][11] but higher plants, (including Gymnosperms and flowering plants) lack the flagellae and centrioles[12] that are present in animal cells.
- 5. Animal Cell Public Domain Image: National Human Genome Research Institute Animal cells are eukaryotic cells, or cells with a membrane-bound nucleus. Unlike prokaryotic cells, DNA in animal cells is housed within the nucleus. In addition to having a nucleus, animal cells also contain other membrane-bound organelles, or tiny cellular structures, that carry out specific functions necessary for normal cellular operation. Organelles have a wide range of responsibilities that include everything from producing hormones and enzymes to providing energy for animal cells. Animal Cells: Structures and Organelles The following are examples of structures and organelles that can be found in typical animal cells: Centrioles - organize the assembly of microtubules during cell division. Cytoplasm - gel-like substance within the cell. Endoplasmic Reticulum - extensive network of membranes composed of both regions with ribosomes (rough ER) and regions without ribosomes (smooth ER). Golgi Complex - responsible for manufacturing, storing and shipping certain cellular products. Lysosomes - sacs of enzymes that digest cellular macromolecules such as nucleic acids. Microtubules - hollow rods that function primarily to help support and shape the cell. Mitochondria - power producers and the sites of cellular respiration. Nucleus - membrane bound structure that contains the cell's hereditary information. Nucleolus - structure within the nucleus that helps in the synthesis of ribosomes. Nucleopore - tiny hole within the nuclear membrane that allows nucleic acids and proteins to move into and out of the nucleus. Ribosomes - consisting of RNA and proteins, ribosomes are responsible for protein assembly. Animal cells contain other cell structures that are not depicted in the illustration above. Some of these structures include the cytoskeleton, cilia and flagella and peroxisomes.
- 6. Parts of the Cell and Its Description Cell Wall A rigid layer of nonliving material that surrounds the sells of plants and some other organisms; helps to protect and support the cell Cell Membrane Controls what substances come into and out of the cell Nucleus The cell's control center; it directs all of the cell's activities Cytoplasm Contains Contains a gel-like material and cell organelles Mitochondria Rod shaped cell structures that produce most of the energy needed to carry out the cell's functions Endoplasmic Reticulum A cell structure that forms a maze of passageways in which proteins and other materials are carried from one part of the cell to another Ribosome A tony structure in the cytoplasm of a cell where proteins are made Golgi Body A structure in the cell that recieves proteins and other newly formed materials from the endoplasmic reticulum, packages them, and distributes them to other parts of the cell Chloroplast A structure in the cells of plants and some other organisms that captures energy from sunlight and uses it to produce food. (This is when the plant bends toward the light). Vacuole A water-filled sac inside a cell that acts as a stoarge area Lysosome A small round cell structure that contains chemicals that break down large food particles into smaller ones Organelle A tiny sell structure that comes out a specific function within the cell
- 7. Cell Parts and Their Functions Nucleus - Large Oval body near the centre of the cell. - The control centre for all activity. - Surrounded by a nuclear membrane. Nucleoplasm - is the protoplasm in the nucleus. - contains genetic material ---> CHROMOSOMES (DNA) Nucleolus - is found in the nucleus. - contains more genetic information (RNA) Cell Membrane - the outer boundary of the cell. - it separates the cell from other cells. - it is porous ---> allows molecules to pass through. Cell Wall ( Plant Cells Only ) - non living structure that surrounds the plant cell. - protects + supports the cell. - made up of a tough fibre called cellulose. Cyto Plasm - cell material outside the nucleus but within the cell membrane. - clear thick fluid. - contains structures called organelles. Vacuoles - are clear fluid sacs that act as storage areas for food, minerals, and waste. - in plant cell the vacuoles are large and mostly filled with water. This gives the plant support. - in animal cells the vacuoles are much smaller. Mitochondria - power house of the cell. - centre of respiration of the cell. - they release energy for cell functions. Chloro Plasts ( Plant cells only ) - contains a green pigment known as chlorophyll which is important for photosynthesis.
- 8. Ribosomes - tiny spherical bodies that help make proteins. - found in the cyto plasm or attached to the endo plasmic reticulum. Endo Plasmic Reticulum ( ER ) - systems of membranes throughout the cyto plasm. - it connects the nuclear membrane to the cell membrane. - passageway for material moving though the cell. Golgi Bodies - tube like structures that have tiny sacs at their ends. - they help package protein. Lysosomes - " suicide sacs " - small structures that contain enzymes which are used in digestion. - if a lysosome were to burst it could destroy the cell.