Discovery of Cells The first observations of cells were made in 1665 by English scientist Robert Hooke, who used a crude microscope of his own invention to examine a variety of objects, including a thin piece of cork.
While Hooke was the first to observe and describe cells, he did not comprehend their significance. At about the same time, the Dutch maker of microscopes Anton Van Leeuwenhoek pioneered the invention of one of the best microscopes of the time. Using his invention, Leeuwenhoek was the first to observe, draw, and describe a variety of living organisms, including bacteria gliding in saliva, one- celled organisms cavorting in pond water, and sperm swimming in semen.
The cell is the structural and functional unit of all known living organisms. It is the smallest unit of an organismthat is classified as living, and is often called the building brick of life.Some organisms, such as most bacteria, areunicellular (consist of a single cell). Other organisms, such as humans, are multicellular.
Major components of the CellTheorya. All living things/ organisms are composed of one or more cells and cell productsb. All living cells come from other living cells by the process of cell division
Cell Functions 1. Nutrition – process by which cells obtain food molecules to support their other activities. 2. Digestion- food particles are broken down into smaller soluble units suitable for cell use with the help of the ENZYMES 3. Absorption- is the process by which cells absorb water, minerals & other matl’s essential to life 4. Biosynthesis- process by which cells organize complex chemicals from simple building units to complex
5. Excretion- process by which by products of all cell activities which are not needed for further cell fxning are eliminated 6. Egestion-insoluble, non digested particles are eliminated by the cell 7. Secretion- process by which substances that are synthesized by the cells are expelled from the membrane (e.g Hormones) 8. Movement- process by which includes the locomotion of cells by means of special structures like cilia of flagella
9. Irritability- process by which cells respond or react to external factors. 10. Respiration- is the process of breaking down food molecules into chemical energy needed by all cells in order to fxn11. Reproduction- process by which cells copy or replicates its DNA and increases its number by cell division.
Anatomy of cells There are two types of cells: eukaryotic and prokaryotic. Prokaryotic cells are usually independent, while eukaryotic cells are often found in multicellular organisms.
Prokaryotic cells prokaryote cell is simpler than a eukaryote cell, lacking a nucleus and most of the other organelles of eukaryotes. There are two kinds of prokaryotes: bacteria and archaea; these share a similar overall structure.
A prokaryotic cell has three architectural regions: on the outside, flagella and pili project from the cells surface. These are structures (not present in all prokaryotes) made of proteins that facilitate movement and communication between cells;
Eukaryotic cellsEukaryotic cells are about 10 times the size of a typicalprokaryote and can be as much as 1000 times greater involume. The major difference between prokaryotes andeukaryotes is that eukaryotic cells contain membrane-bound compartments in which specific metabolicactivities take place. Most important among these is thepresence of a cell nucleus, a membrane-delineatedcompartment that houses the eukaryotic cells DNA. It isthis nucleus that gives the eukaryote its name, whichmeans "true nucleus."
An animal cell typically contains several types of membrane-bound organs, or organelles. The nucleus directs activities of the cell and carries genetic information from generation to generation. The mitochondria generate energy for the cell. Proteins are manufactured by ribosomes, which are bound to the rough endoplasmic reticulum or float free in the cytoplasm. The Golgi apparatus modifies, packages, and distributes proteins while lysosomes store enzymes for digesting food. The entire cell is wrapped in a lipid membrane that selectively permits materials to pass in and out of the cytoplasm.
Table 1: Comparison of features of prokaryotic and eukaryotic cells Prokaryotes Eukaryotes Typical organisms bacteria, archaea protists, fungi, plants, animals ~ 10-100 µm (sperm cells, apart from Typical size ~ 1-10 µm the tail, are smaller) Type of nucleus nucleoid region; no real nucleus real nucleus with double membrane linear molecules (chromosomes) with DNA circular (usually) histone proteins RNA-synthesis inside the nucleus RNA-/protein-synthesis coupled in cytoplasm protein synthesis in cytoplasm Ribosomes 50S+30S 60S+40S highly structured by endomembranes Cytoplasmatic structure very few structures and a cytoskeleton flagella and cilia containing Cell movement flagella made of flagellin microtubules; lamellipodia and filopodia containing actin one to several thousand (though some Mitochondria none lack mitochondria) Chloroplasts none in algae and plants single cells, colonies, higher Organization usually single cells multicellular organisms with specialized cells Mitosis (fission or budding) Cell division Binary fission (simple division) Meiosis
Comparison of structures between animal and plant cells Typical animal cell Typical plant cell Organelles •Nucleus •Nucleus •Nucleolus (within •Nucleolus (within nucleus) nucleus) •Rough endoplasmic •Rough ER reticulum (ER) •Smooth ER •Ribosomes •Ribosomes •Cytoskeleton •Cytoskeleton •Golgi apparatus •Golgi apparatus •Cytoplasm (dictiosomes) •Mitochondria •Cytoplasm •Vesicles •Mitochondria •Lysosomes •Centrosome •Centrioles •Vacuoles •Smooth ER
The Plasma Membrane—A Cells Protective Coat The outer lining of a eukaryotic cell is called the plasma membrane. This membrane serves to separate and protect a cell from its surrounding environment and is made mostly from a double layer of proteins and lipids, fat-like molecules. Embedded within this membrane are a variety of other molecules that act as channels and pumps, moving different molecules into and out of the cell. A form of plasma membrane is also found in prokaryotes, but in this organism it is usually referred to as the cell membrane.
The plasma membrane (cell membrane) is made of two layers of phospholipids. The membrane has many proteins embedded in it. The plasma membrane regulates what enters and leaves the cell. Many molecules cross the cell membrane by diffusion and osmosis.
The Cytoskeleton—A CellsScaffoldThe cytoskeleton is animportant, complex, and dynamiccell component. It acts to organizeand maintain the cells shape;anchors organelles in place; helpsduring endocytosis, the uptakeof external materials by a cell; andmoves parts of the cell inprocesses of growth and motility.There are a great number ofproteins associated with thecytoskeleton, each controlling acell’s structure by directing,bundling, and aligning filaments.
The Cytoplasm—A Cells Inner Space Inside the cell there is a large fluid-filled space called the cytoplasm, sometimes called the cytosol. In prokaryotes, this space is relatively free of compartments. In eukaryotes, the cytosol is the "soup" within which all of the cells organelles reside. It is also the home of the cytoskeleton. The cytosol contains dissolved nutrients, helps break down waste products, and moves material around the cell through a process called cytoplasmic streaming. The nucleus often flows with the cytoplasm changing its shape as it moves. The cytoplasm also contains many salts and is an excellent conductor of electricity, creating the perfect environment for the mechanics of the cell. The function of the cytoplasm, and the organelles which reside in it, are critical for a cells survival.
Genetic Material Two different kinds of genetic material exist: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Most organisms are made of DNA, but a few viruses have RNA as their genetic material. The biological information contained in an organism is encoded in its DNA or RNA sequence.
The Nucleus—A Cells Center The nucleus is the most conspicuous organelle found in a eukaryotic cell. It houses the cells chromosomes and is the place where almost all DNA replication and RNA synthesis occur. The nucleus is spheroid in shape and separated from the cytoplasm by a membrane called the nuclear envelope. The nuclear envelope isolates and protects a cells DNA from various molecules that could accidentally damage its structure or interfere with its processing. During processing, DNA is transcribed, or synthesized, into a special RNA, called mRNA. This mRNA is then transported out of the nucleus, where it is translated into a specific protein molecule. In prokaryotes, DNA processing takes place in the cytoplasm.
The Ribosome—The Protein Production Machine Ribosomes are found in both prokaryotes and eukaryotes. The ribosome is a large complex composed of many molecules, including RNAs and proteins, and is responsible for processing the genetic instructions carried by an mRNA
The mitochondria are specialised for energy production (respiration). Chloroplasts are organelles found in plant cells which produce sugar using light. Light is the ultimate source of energy for almost all life on Earth. The area of the cell outside the nucleus and the organelles is called the cytoplasm. Membranes are complex structures and they are an effective barrier to the environment, and regulate the flow of food, energy and information in and out of the cell
Transport, "intracellular highway".Ribosomes are positioned along the roughER, protein made by the ribosomes enter theER for transport. Processes, packages and secretes proteins. Like a factory.