Cell Structure and Function 2021 PDF

Cell Structure and Function  Major Themes: Knowledge improves with technological advances Cells need to be small or have an increased surface area Membranes create compartments Endomembrane system Endosymbiotic theory Similarities/differences between prokaryotic and eukar...

Cell Structure and Function  Major Themes: Knowledge improves with technological advances Cells need to be small or have an increased surface area Membranes create compartments Endomembrane system Endosymbiotic theory Similarities/differences between prokaryotic and eukaryotic  Hooke: Mid 1600s - observed and described “cells” in cork Leeuwenhoek: Late 1600s- observed “animalcules;” living cells Brown: 1820s - observed and named nucleus in plant cells  Cell Theory 1) Every organism is composed of one or more cells (Schwann) 2) Cell is smallest unit having properties of life (Schleiden) 3) Continuity of life arises from growth and division of single cells (Virchow)  Two types of cells: prokaryotic eukaryotic No organelles Organelles specialized Cytosol with to perform specific ribosomes functions in cytosol DNA found in DNA in the nucleus “nucleoid” region Some have cell walls External structures Examples: animal, (wall, capsule) plant, fungi and protist different from eukaryotic Examples: eubacteria and archaea All Cells: smallest unit of life can survive on its own or has potential to do so highly organized for metabolism sense and responds to environment have potential to reproduce  …Have a Lipid Bilayer Main component of cell membranes Gives the membrane its fluid properties Two layers of phospholipids (hydrophilic heads/hydrophobic tails) one layer of lipids one layer of lipids  Why are cells so small? Most cells are tiny, in order to maintain a good surface area-to-volume ratio. The volume of a cell determines its metabolic activity relative to time. The surface area of a cell determines the number of substances that can enter or leave the cell.  … Have Ribosomes Cells need a way to manufacture polypeptides  Ribosomes Ribosomes translate the nucleotide sequence of messenger RNA into a polypeptide chain (sites of protein synthesis) Ribosomes are not membrane-bound organelles—in eukaryotes, they are free in the cytoplasm, attached to the endoplasmic reticulum, or inside mitochondria and chloroplasts. In prokaryotic cells, ribosomes float freely in the cytoplasm. Each subunit consists of ribosomal RNA  Light Microscope Create detailed images of something that is otherwise too small to see Can be simple or compound  Limitations of Light Microscopy Wavelengths of light are 400-750 nm If a structure is less than one-half of a wavelength long, it will not be visible Light microscopes can resolve objects down to about 200 nm in size  Electron Microscope Scanning (SEM) or transmission (TEM)  Electron Microscopy Uses streams of accelerated electrons rather than light Electrons are focused by magnets rather than glass lenses Can resolve structures down to  Eukaryotic Cells Have a nucleus and other organelles Eukaryotic organisms (kingdoms) – Plants – Animals – Protists – Fungi  What is the benefit of having organelles? Animal Cell Features Figure 4.10b Page 61 Plant Cell Features Structures and Function of the Nucleus Keeps the DNA molecules of eukaryotic cells separated from metabolic machinery of cytoplasm Makes it easier to organize DNA and to copy it before parent cells divide into daughter cells  Nuclear Envelope Two outer membranes (lipid bilayers) Innermost surface has DNA attachment sites Nuclear bilayer facing cytoplasm Nuclear envelope pore bilayer facing nucleoplasm  Endomembrane System Group of related organelles in which lipids are assembled and new polypeptide chains are modified Products are sorted and shipped to various destinations Components of Endomembrane System Endoplasmic reticulum Vesicles Golgi Vesicles  Endoplasmic Reticulum In animal cells, continuous with nuclear membrane Rough ER modifies polypeptide chains Smooth ER: manufactures lipids, metabolizes carbohydrates, detoxifies poisons Rough endoplasmic reticulum (RER) has ribosomes attached to begin protein synthesis. Newly made proteins enter the RER lumen. Once inside, proteins are chemically modified and tagged for delivery. All secreted proteins and most membrane proteins pass through the RER. Smooth endoplasmic reticulum (SER)— more tubular, no ribosomes, continuation of the RER but without ribosomes chemically modifies small molecules such as drugs and pesticides. site of glycogen degradation in animal cells. site of synthesis of lipids and steroids.  Golgi Body Receives proteins from the RER—can further modify, package, sort, and add carbohydrates to proteins Site of polysaccharide synthesis in plant cells Packages finished material for shipment to final destinations Material arrives (cis) and leaves (trans) in vesicles  Vesicles Membranous sacs that move through cytoplasm – Lysosomes – Transport vesicles – Peroxisomes vesicle (many others) https://www.youtube.com/watch?v=Fcxc8Gv7NiU  Mitochondria ATP-producing “powerhouses” Membranes form two distinct compartments ATP-making machinery embedded in inner mitochondrial membrane  Chloroplasts Convert sunlight energy to the energy of organic sugars through photosynthesis (DNA + ribosomes)  Mitochondrial/Chloroplast Origin (endosymbiotic theory) Mitochondria/chloroplasts resemble bacteria – Have own DNA, ribosomes – Divide on their own Most likely evolved from prokaryotes that were engulfed but not digested  Specialized Plant Organelles Plastids Central Vacuole  Other Plastids Chromoplasts – No chlorophyll – Abundance of carotenoids – Color fruits and flowers red to yellow Leucoplasts/ amyloplasts – No pigments – Store starch All have DNA + Apoptosis: programmed cell death Involves a sequence of cellular events that bring about the destruction of the cell. – Fragmenting of the nucleus – Blistering of the plasma membrane – Engulfing of cell fragments by white blood or other cells Caused by enzymes called caspases. Mitosis and apoptosis are opposing forces. – Mitosis increases cell number – Apoptosis decreases cell number  Autophagy https://www.youtube.com/watch?v=Hqs1Wz https://www.youtube.com/watch?v=bOWgQvnNn9 A https://www.youtube.com/watch? v=bOWgQvnNn9ATwBEU  Cytoskeleton Present in all eukaryotic cells Basis for cell shape and internal organization Allows organelle movement within cells and, in some cases, cell motility  Cytoskeletal Elements intermediate filament microtubule microfilament  tubulin Microtubules subunit Largest components Composed of tubulin Involved in shape, motility, cell division Figure 4.21 Page 71 Microfilaments Thinnest elements Composed of actin Take part in movement, formation, and maintenance of actin cell shape subunit Figure 4.21 Page 71  Intermediate Filaments Only in animal cells of certain tissues Most stable cytoskeletal elements one polypeptide chain Figure 4.21 Page 71  Motor Proteins Kinesins and dyneins move along microtubules Myosins move along microfilaments kinesi n microtubule http://www.youtube.com/watch?v=YAva4g3Pk6k  Flagella and Cilia Structures for cell microtubule motility 9 + 2 internal structure http://www.youtube.com/watch?v= 2lA2faVXt7A dynein Cilia and Flagella  Plant Cell Walls Secondary cell wall (3 layers) made of Cellulose and lignin Primary cell wall (secreted first, made of polysaccharides,glyco- proteins and cellulose)  Plant Cuticle Cell secretions and waxes accumulate at plant cell surface Semitransparent Restricts water loss Matrices between Animal Cells Hold cells together in tissues Contribute to physical properties of cartilage, skin, and other tissues Filter materials Orient cell movement during growth and repair Plant Cell Junctions Plasmodesmata -- plasma membranes of adjacent cells are continuous; water and solutes can pass freely between cells The plant cell wall has three major roles: Provides support for the cell and limits volume by remaining rigid Acts as a barrier to infection Contributes to form during growth and development Adjacent plant cells are connected by plasma membrane-lined channels called plasmodesmata. These channels allow movement of water, ions, small molecules, hormones, and some RNA and proteins.  Animal Cell Junctions Tight junctions – anchor cells together (form tissue) Desmosomes-- anchor cells together in tissue that stretches Gap junctions – communication between cells  Prokaryotic Cells Two Kingdoms: Archaea and Eubacteria DNA is not enclosed in nucleus, nucleoid Plasmid – small, circular piece of DNA Generally the smallest, simplest cells No organelles, but they do have ribosomes May have flagellum, but it is structurally different from eukaryotic cell  Prokaryotic Cell Structures Pilus/pili Inner Life of a Cell: http://www.youtube.com/watch?v=wJyUtbn0O5Y Explanation of animation: http://multimedia.mcb.harvard.edu/anim_extravasation.h tml Apoptosis vs. Necrosis https://www.youtube.com/watch?v=1vaEVcMfa1E Autophagy: https://www.youtube.com/watch?v=Hqs1WzTwBEU Overview of cell/interactive quiz: https://www.wisc-online.com/learn/general-education/an atomy-and-physiology1/ap11403/a-typical-animal-cell