The Cell Overview of cell function and structure
The Cell: The Basic Unit of Life The Cell is a highly complex and well organized structure which manages hundreds of thousand of complex reactions almost every second. The term Cell was first evoked by a biologist called Robert Hooke in the 17 century, who on observing a section of cork through a microscope, noted that the plant stem was divided into series of units or cells.
Cells The four characteristics of cells. All organisms -living things- are made of cells. These cells are like tiny building blocks. Cells do the jobs that keep organisms alive. Cells are the smallest part of a living thing.
Cell Basics: All Organisms are Made of Cells The cell is the basic unit of structure & function The cell is the smallest unit that can still carry on all life processes Both unicellular (one celled) and Multicellular (many celled) organisms are composed of cells Before the 17 th century, no one knew cells existed Most cells are too small to be seen with the unaided eye In the early 17 th century microscopes were invented & cells were seen for the 1 st time
Cell Basics: Principles of the Cell Theory All living things are made of one or more cells Cells are the basic unit of structure & function in organisms Cells come only from the reproduction of existing cells
Cell Basics: Cell Diversity Not all cells are alike Cells differ in size, shape, and function The female egg cell is the largest cell in the body & can be seen without a microscope Bacterial cells are some of the smallest cells & are only visible with a microscope Cells are limited in size by the ratio between their outer surface area & their volume
Cells come in a variety of shapes, & the shape which helps determine the function of the cell (e.g. Nerve cells are long to transmit messages in the body, while red blood cells are disk shaped to move through blood vessels)
The Cell: Basic Unit of Life The cell is the smallest unit of life capable of independently sustaining and reproducing itself. Cells can be divided into two principal types, prokaryotic and Eukaryotic cells that is, with and without a nucleus. Cells are always building and breaking down material. Cells release energy from foods, and then use that energy to make needed cell parts. A cells function is to make your body operate.
Prokaryotic vs. Eukaryotic "Karyose" comes from a Greek word which means "kernel," as in a kernel of grain. In biology, we use this word root to refer to the nucleus of a cell. "Pro" means "before," and "eu" means "true," or "good." So "Prokaryotic" means "before a nucleus," and “Eukaryotic" means "possessing a true nucleus." This is a big hint about one of the differences between these two cell types. Prokaryotic cells have no nuclei, while Eukaryotic cells do have true nuclei.
Prokaryotic Cells Prokaryotes were here first and for billions of years were the only form of life on Earth. Prokaryotic cells are less complex Unicellular (one celled) Do not have a nucleus & no membrane- bound organelles Most have a cell wall surrounding the cell membrane & a single, looped chromosome (genetic material) in the cytoplasm
Prokaryotic Cells Prokaryotic cells feature three major shapes: rod shaped, spherical, and spiral. Prokaryotic cells include bacteria & blue-green bacteria. Prokaryotic cells are found only in the kingdom Monera
Prokaryotic Cells Prokaryotic Cells such as 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.
Eukaryotic cells Eukaryotic cells have a true nucleus Animals, plants, fungi, and protists are eukaryotes Animalsplantsfungi protists Eukaryotic cells also contain membrane-bound organelles such as mitochondria and chloroplasts.organellesmitochondria chloroplasts
Eukaryotic cells a. Nucleus b. Chloroplast c. Golgi d. Mitochondria
Animal cell An animal cell is a form of eukaryotic cell which make up many tissues in animals. The animal cell is distinct from other eukaryotes, most notably plant cells, as they lack cell walls and chloroplasts, and they have smaller vacuoles. Due to the lack of a rigid cell wall, animal cells can adopt a variety of shapes. Human cells are biologically categorized as animal cells.eukaryotic celltissues animals plant cellscell walls chloroplasts vacuolescell wallHuman cells
Plant Cells Plant cells are quite different from the cells of the other eukaryotic organisms. Their distinctive features are:cellsorganisms A large central vacuolevacuole A cell wall made up of cellulose and proteincell wallcelluloseprotein They contain chlorophyll, the pigment that gives plants their green color and allows them to perform photosynthesis.chlorophyllplantsphotosynthesis Plant groups without flagella (including conifers and flowering plants) also lack centrioles that are present in animal cells.flagella conifersflowering plants centriolesanimal cells
Fungi Cells Fungal cells are most similar to animal cells, with the following exceptions. A cell wall made of chitin.chitin Only the most primitive fungi, chytrids, have flagella.chytrids Primitive fungi have no such divisions, and each organism is essentially a giant supercell. These fungi are described as coenocytic.coenocytic
Cell structures we will cover Vacuole Chloroplast Ribosomes Nucleus Golgi Apparatus Mitochondrion Lysosome Centriole Endoplasmic Reticulum Unit Membrane Cell Membrane Cell Wall Chromatin- Chromosomes
Unit Membrane Cell Membrane Separates the cytoplasm of the cell from its environment Protects the cell & controls what enters and leaves Cell membranes are selectively permeable only allowing certain materials to enter or leave The cell membrane is constantly breaking down & being reformed inside living cells. K. Certain small molecules such as CO 2, H 2 O, & O 2 can easily pass through them membrane
Cell Membrane Structure - same as unit membrane. Function - acts as a boundary layer to contain the cytoplasm (fluid in cell) - interlocking surfaces bind cells together - selectively permeable to select chemicals that pass in and out of cells
Cell Wall Structure - a non-living secretion of the cell membrane, composed of cellulose - cellulose fibrils deposited in alternating layers for strength - contains pits (openings) that make it totally permeable Function - provides protection from physical injury - together with vacuole, provides skeletal support
Nucleus The nucleus (pl. nuclei; from Latin nucleus or nuculeus, kernel) is a membrane-enclosed organelle found in most eukaryotic cells.Latin organelleeukaryoticcells Contains most of the cell's genetic material, or DNAgenetic material Main structural elements of the nucleus are: nuclear envelope Nucleolus Chromatin nucleoplasm
Nucleus Nuclear Envelope Structure - two unit membranes with a fluid-filled space - nuclear pores present - outer membrane may be continuous with endoplasmic reticulum Function - selectively permeable to control movement in or out - contains nuclear contents
Nucleus Nucleus - Is surrounded by a double membrane and contains the cell's DNA and the nucleolus, the site of RNA and ribosome production. The nucleus regulates all cell activity. It does this by controlling the enzymes present.
Nucleolus Structure - non-membranous matrix of RNA (ribonucleic acid) and protein Function - instructions in DNA are copied here - works with ribosome's in the synthesis of protein
Chromatin-Chromosomes Chromatin is a mass of uncoiled DNA and associated proteins called histones. When cell division begins, DNA coils around the proteins forming visible structures called chromosomes.
Chromatin Structure -composed of long thin strands of DNA Function -contains instructions that control cell metabolism and heredity
Chromosome Structure and Replication A chromatid is a single DNA molecule. Double-stranded chromosomes have two chromatids; normally, each one is identical to the other. The point where the two chromatids are attached is called the centromere.
Endoplasmic Reticulum Endoplasmic Reticulum (E.R.) Extensive internal membrane system throughout the cell which not only acts as a transport and communications system but also the principal site lipid synthesis and plays a role in protein synthesis.
Endoplasmic Reticulum (ER) Endoplasmic Reticulum (ER) Structure - sheets of unit membrane with ribosomes on the outside - forms a tubular network throughout the cell Function - transports chemicals between cells and within cells - provides a large surface area for the organization of chemical reactions and synthesisribosomes
Ribosome's Ribosome Structure - non- membraneous, spherical bodies composed of RNA (ribonucleic acid) and protein enzymes Function - site of protein synthesis
Golgi Body or Apparatus Golgi Apparatus modifies, packages, & helps secrete cell products such as proteins and hormones Consists of a stack of flattened sacs called cisternae Receives products made by the ER or endoplasmic reticulum
Mitochondria Mitochondrion Structure - composed of modified double unit membrane (protein, lipid) - inner membrane infolded to form cristae Function - site of cellular respiration i.e.. the release of chemical energy from food Glucose + Oxygen ------> Carbon Dioxide + Water + Energy (ATP)
Lysosome Lysosome Structure - membrane bound bag containing hydrolytic enzymes - hydrolytic enzyme = (water split biological catalyst) i.e. using water to split chemical bonds Function - break large molecules into small molecules by inserting a molecule of water into the chemical bond
Vacuoles Vacuole Structure - a single layer of unit membrane enclosing fluid in a sack Vacuole Function - produces turgor pressure against cell wall for support - stores water and various chemicals - may store insoluble wastes Vascular tissue transports food & water
Chloroplast Chloroplast Structure - composed of a double layer of modified membrane (protein, chlorophyll, lipid) - inner membrane invaginates to form layers called "grana" (sing., granum) where chlorophyll is concentrated Function - site of photosynthesis Chlorophyll Carbon Dioxide + Water --------> Glucose + Oxygen radiant energy(light) (food)
Centriole Centriole Structure - nine triplets of microtubules form one centriole - two centrioles form one centrosome Function - forms spindle fibres to separate chromosomes during cell division