* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Cell notes
Survey
Document related concepts
Cytoplasmic streaming wikipedia , lookup
Tissue engineering wikipedia , lookup
Cell membrane wikipedia , lookup
Cell growth wikipedia , lookup
Signal transduction wikipedia , lookup
Cell nucleus wikipedia , lookup
Cell encapsulation wikipedia , lookup
Cell culture wikipedia , lookup
Cellular differentiation wikipedia , lookup
Cytokinesis wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
Extracellular matrix wikipedia , lookup
Transcript
FOOD FOR THOUGHT Figure 4.3 Microscopes as a Window on the World of Cells • Microscopy: purpose to magnify images too small to see • Magnification – Is an increase in the specimen’s apparent size. • Resolving power – Is the ability of an optical instrument to show two objects as being separate. Euglena – The light microscope is used by many scientists. • Light passes through the specimen. • Lenses enlarge, or magnify, the image. • The electron microscope (EM) uses a beam of electrons. – It has a higher resolving power than the light microscope. • The electron microscope can magnify up to 100,000X. – Such power reveals the diverse parts within a cell. • The transmission electron microscope (TEM) is useful for exploring the internal structure of a cell. A beam of electrons transmitted through the sliceproduces a cross section • The scanning electron microscope (SEM) is used to study the detailed architecture of the surface of a cell. Beam of electrons reflected off surface- 3-D image • Cells were first discovered in 1665 by Robert Hooke. • The accumulation of scientific evidence led to the cell theory. – All living things are composed of cells. – All cells are formed from previously existing cells. – Cells are smallest unit of life Isolating Techniques of cool stuff inside a cell - Cell fractionation - Split everything apart - Centrifuge based on mass The Two Major Categories of Cells • The countless cells on earth fall into two categories: – Prokaryotic cells – Eukaryotic cells • Prokaryotic and eukaryotic cells differ in several respects. Figure 4.4 • Prokaryotic cells – Are smaller than eukaryotic cells. – Lack internal structures surrounded by membranes. – Lack a nucleus. – Examples: Bacteria and Archae Figure 4.5 • Eukaryotic cells – Are larger than prokaryotic cells. – Have internal structures surrounded by membranes. – DNA contained within a nucleus. – Examples: Protists, Fungi, Plant and Animal A Panoramic View of Eukaryotic Cells • An idealized animal cell • An idealized plant cell Cytoplasmic Streaming The Microscopic World of Cells • Organisms are either: – Single-celled, such as most bacteria and protists – Multicelled, such as plants, animals, and most fungi – For the most part cells are small • Exception: bird eggs, neurons, some algae and bacteria Tour of a Eukaryotic Cell - Cytoplasm - Nucleus - Ribosomes - Endomembrane System - Nuclear Envelope - ER - Golgi Apparatus - Lysosomes - Vacuoles - Plasma (Cell) Membrane - Mitochondria - Chloroplasts - Cytoskeleton Cytoplasm All cells have cytoplasm that includes everything inside the cell like organelles. AKA cytosol it is a jelly-like substance. The Nucleus • Nucleus Definition: • The nucleus is the manager of the cell. – DNA that holds the genes in the nucleus store information necessary to produce proteins. – It contains chromatin and chromosomes. • DNA + Protein ; condensed chromatin – It contains a nucleolus. • Synthesizes Ribosomes Structure and Function of the Nucleus • The nuclear envelope (a double membrane) borders the nucleus and contain pores. Nuclear lamina on the inside layer of the envelope helps maintain the shape of the nucleus Ribosomes • Ribosomes (folded strands of ribosomal RNA) are responsible for protein synthesis. – Free ribosomes usually make proteins that will function/stay in the cytosol. – Bound ribosomes (attached to the Endoplasmic Reticulum) usually make proteins that are exported or included in the cell's membranes. – Cool fact: free ribosomes and bound ribosomes are interchangeable and the cell can change their numbers according to metabolic needs. DNA controls the cell by transferring its coded information into RNA. The information in the RNA is used to make proteins. Figure 4.9 The Endomembrane System: Manufacturing and Distributing Cellular Products • Includes many of the membranous organelles in the cell belong to the endomembrane system. The Endoplasmic Reticulum • The endoplasmic reticulum (ER) – System of membranes that produce an enormous variety of molecules. – Is composed of smooth and rough ER. Smooth ER – lacks surface ribosomes • Synthesizes: produces phospholipids, steroids and hormones; metabolizes carbs (in the liver) • Participates: in hydrolysis of glycogen (animal cells) • Detoxifies: by chemically modifying drugs and pesticides • Stores and modifies: proteins made by ribosomes and RER • . Rough ER • The “roughness” of the rough ER is due to ribosomes that stud the outside of the ER membrane. • Formation: – Synthesize: Proteins (made by ribosomes) enter RER – Proteins are altered (folded or have other molecules attached) • Carbohydrates are attached to change function and act as a “name tag” so the protein “knows” where to go (usually to the membrane) – Transports: vesicles containing proteins Figure 4.11 The Golgi Apparatus • The Golgi apparatus – Works in partnership with the ER (modifies and transports proteins). – Refines, stores, and distributes the chemical products of cells. Figure 4.12 Parts of the Golgi • Three distinct parts (top, middle and bottom): • Bottom: cis region is close to nucleus/RER • Receiving end • Middle: cisternae is in between • transport • Top: trans region is close to surface of cell • Exit end Lysosomes • A lysosome is a membrane-enclosed sac. – It contains digestive (hydrolytic) enzymes. – The enzymes break down macromolecules, digest food, and break down damaged organelles. - Examples: - Autophagy - recycling of cell parts - Phagocytosis by amoeba and macrophages - Development - Digestion of tadpole tail, webbing between fingers - Tay-Sach's Disease - lipid digestion enzyme is missing from lysosomes and lipids accumulate in the brain • Lysosomes have several types of digestive functions. – They fuse with food vacuoles to digest the food. Lysosome Formation Vacuoles • Vacuoles are membranous sacs. There are three types: – Food vacuoles- contain food/water for cell – contractile vacuoles of protists: used for osmoregulation (pump water out of cell thru pore) Paramecium Vacuole • central vacuoles of plants: – act as a reservoir of nutrients: ~toxic by-products ~waste products (with storage makes plant taste bad and protects from predators!) ~nutrients/proteins/carbohydrates – generate turgor – aids in growth Figure 4.14 Peroxisomes • These organelles collect toxic peroxides which are byproducts of chemical reactions • Ex: hydrogen peroxide H2O2 • A review of the endo-membrane system Figure 4.15 HOMEWORK DUE FRIDAY Create a story about how 10 cellular organelles worked together to complete a goal! Must include functions. Chloroplasts and Mitochondria: Energy Conversion • Cells require a constant energy supply to do all the work of life. Mitochondria • Mitochondria are the sites of cellular respiration, which involves the production of ATP from food molecules. – Found in most eukaryotes Chloroplasts • Chloroplasts are the sites of photosynthesis, the conversion of light energy to chemical energy. • Mitochondria and chloroplasts share another feature unique among eukaryotic organelles. – They contain their own DNA. • The existence of separate “mini-genomes” is believed to be evidence that – Mitochondria and chloroplasts evolved from free-living prokaryotes in the distant past. Other features of Chloroplasts • Plastids- an organelle only in plant cells and some protists. They can differentiate into… Amyloplast- aka leukoplast (white/colorless) plastid that converts glucose to starch. Found in potatoes! Chromoplast- contain red, orange and/or yellow pigments. Aid in pollination and seed dispersal Chloroplast- green pigment chlorophyll (light energy converted to chemical energy) The Cytoskeleton: Cell Shape and Movement • The cytoskeleton is an infrastructure of the cell consisting of a network of fibers. • Functions of the cytoskeleton – provide mechanical support for the cell and maintain its shape. – Aids in cellular movement/change shape – Positions organelles within the cell – Act as tracks for other objects to move on – Anchor the cell Figure 4.18a Microtubules Make the internal skeleton for cells and aid in protein movement thru cell Push/pull chromosomes to daughter cells Make up cilia and flagella Cilia and Flagella • Cilia and flagella are motile appendages. • Flagella propel the cell in a whiplike motion for movement of whole cell. • Cilia move in a coordinated back-and-forth motion to – move whole cell (unicellular) – move materials past cell (multicellular). Paramecium Cilia Cilia and Flagella • Some cilia or flagella extend from nonmoving cells. – The human windpipe is lined with cilia. Microfiliments • Help cell or parts to move • Determine and stabilize cell shape • Formed from actin (protein) • EXAMPLES • Actin and myosin move your muscles • Pinching to divide cells in mitosis • Cytoplasmic streaming Intermediate filiments • 50 kinds!! • Built of “ropes” of fibrous proteins • Functions: Stabilize cell structure • Make hair and fingernails • Support microvilli of intestines • These structures are build to resist tension Centrioles Produce mitotic spindle Found in animal cells (plants lack these) Composed of specialized microtubules Membrane Structure • The plasma membrane separates the living cell from its nonliving surroundings. • The membranes of cells are composed mostly of: – Lipids – Proteins • The lipids belong to a special category called phospholipids. • Phospholipids form a two-layered membrane, the phospholipid bilayer. • Most membranes have specific proteins embedded in the phospholipid bilayer. Desmosomes Gap Junctions Tight Junctions • Membrane phospholipids and proteins can drift about in the plane of the membrane. • This behavior leads to the description of a membrane as a fluid mosaic: – Molecules can move freely within the membrane. – A diversity of proteins exists within the membrane. Evolution Connection: The Origin of Membranes • Phospholipids were probably among the organic molecules on the early Earth. • When mixed with water, phospholipids spontaneously form membranes. Cell Surfaces • Most cells secrete materials for coats of one kind or another – That are external to the plasma membrane. • These extracellular coats help protect and support cells – And facilitate interactions between cellular neighbors in tissues. • Plant cells have cell walls, – Which help protect the cells, maintain their shape, and keep the cells from absorbing too much water. • Animal cells have an extracellular matrix, – Which helps hold cells together in tissues and protects and supports them. Cell Animation Video CELL WALLS Extracellular structure that Provides support and limits water absorption Acts as a barrier to infection Maintains cell shape Found in plants, fungi, some protists and bacteria Cellulose Polysaccharides that form the fibers of the cell wall Plasmodesmata Membrane lined channels that run thru cell walls connecting cells that are side by side. Allow movement of water, ions, RNA etc Primary cell walls Vs Secondary Cell wall Primary Cell Wall Secondary Cell Wall First wall to develop in growing/dividing cells Develops after cell stops growing/dividing Acts as normal cell wall with a few differences: Acts as normal cell wall AND *flexible *is thicker and stronger *controls rate / direction / shape of growth *contains conducting systems for nutrients and water …evolutionary advantage Ex: wood Primary cell walls Vs Secondary Cell wall Extracellular Matrix - Extracellular Matrix (animal cells) - Types of Structures - Collagen - 1/4 to 1/2 of the protein inthe human body) that provides strength - Proteoglycans - form the extracellular matrix (ECM) - Integrins - Integral proteins that transfer signals in and out of the cell - Fibronectins - proteins that connect integrins to the ECM Junctions- like function junction! All four junctions join cells together Tight junctions Prevent passage of material in space btwn cells. Water tight seal Block passage of material btwn lumen (apical side) and interior of tissue (basal side) Junctions Desmosomes- localized adhesions (proteins) to resist shearing forces; keep animal cells attached to each other. Junctions Gap junctions Allow passage of some small molecules in the gaps between cells Junctions PlasmodesmataNarrow tunnels that connect two plant cells