Biology - Cell Structure

Chapter 4 – Cell structure The Cell theory The cell theory states that:  All organisms are composed of ONE OR MORE CELLS  CELLS are the basic living unit of structure and function in organisms.  All cells come only from other cells. Who were credited for formulating the cell theory? Matthias Schleiden: speculated that cells are living entities and plants are aggregates of cells? Theodore Schwann : extended the research of Schleiden, with animal cells Rodulf Virchow Cell size Describe the sizes of the cells? Why is the cell small and what limits the size of the cell? Cell size can be small or can be big, but generally they are small. Like a frog egg and a chicken egg the human eye can see it. What is the importance of greater surface area-to-volume in smaller cells? Faster rate of metabolism, faster rate of transport, faster growth rate. What limits the size of a cell? The Surface Area to Volume Ration (SA/V) -Reactants enter the cell through the plasma membrane, and waste products exit through the cell membrane. - In bigger cells the surface area to volume ration (SA/V) is smaller so the materials going in and waste product going out can’t go as fast as in small cells. -Volume increases faster(x1000) than the surface area(x 100) -If cells are small, it is more beneficial, everything is faster. Microscopy Chapter 4 – Cell structure Microscopy is the use of LIGHT OR ELECTRONS to magnify objects Wavelength of Radiation What is wavelength? Light travels inn waves, the distance between the two waves is the wavelength. The greater the wavelength the shorter the resolving power. The smaller the wavelength the greater the resolving power. What lights are used in microscopy? The electromagnetic Spectrum Light microscope (Lm)= 200 nm Electron microscope (Em)= .1nm Human eye= .1mm or 100000nm Resolution What is resolution and resolving power? -Resolution is clarity, clearness of the image. -Higher resolution/ resolving power, the sharper the image/ clearer. Lower resolution/ resolving power the less sharp an image. -Resolving power or limit of resolution- minimum distance between two distinguishable points. Magnification What is magnification? The apparent (appears [large]) increase in size of the specimen How do you determine total magnification? Tm= outer(ocular) lens x objective lens total magnification -Refraction or bending of the light, when looking through a microscope it will flip the image upside-down due to this bending in the light. # Why do light rays bend when they travel from air to glass? Because they have different density’s, glass is denser than the air. (molecules) Describe how image is produced in the compound microscope? To allow the visualization of cells and cellular components 2 Chapter 4 – Cell structure Why is the object inverted when observed under the microscope? Because of the bending in the light # Contrast What is contrast? Difference in the intensity of color of the cells and the background Types of microscopes Describe the types of microscopes?  Light  Electron  Probe 3 Chapter 4 – Cell structure Two types of cells What are the two types of cells? Prokaryotic cells  bacteria, archaea Eukaryotic cells  plants, animals , fungi, protists Differentiate prokaryotic cells from eukaryotic cells? (chapter 1 notes) What are examples of prokaryotes and eukaryotes? (chapter 1 notes) Parts of a bacterial cell Parts Function Fimbriae (Pili) For attachment Nucleoid Contains the DNA Ribosomes For protein synthesis Plasma(cell) For transport, ATP generation, photosynthesis, membrane where cellular respiration takes place, Cell wall For support, protection, underneath capsule, gives the bacteria its shape. Capsule For attachment, protection from dehydration and proteinosis. Made of polysaccharides. Outermost surface. Flagella For movement  movement of bacteria is 360 (there can be more than one) Comparison of prokaryotes and eukaryotes (animals vs plants) Put a check mark ( +)if the parts enumerated in the table below are present and a dash mark (-) if absent. Parts Non-membranous parts Ribosomes Cytoskeleton Centrosomes Prokaryotes (Archaea and Bacteria) Eukaryotes Animal cell Plant cell + + or - + + + 4 + + - Chapter 4 – Cell structure Membranous parts Nucleus Endoplasmic reticulum Golgi bodies Lysosomes Peroxisomes Vacuoles Vesicles Mitochondria Chloroplasts Other parts Plasma membrane DNA Cell wall - + + + + - + + + + + - + (photosytic) + nnn + + - + + + + + (central vauole) + + + + + + -Archaeal membranes contain saturated hydrocarbons in a monolayer this explains greater thermal stability of their membrane. Parts and functions of eukaryotic cell Nucleus Give the function of the nucleus? Stores DNA What is nucleolus for? Site of rRNA synthesis (r=ribosomal) What structure encloses the nuclear materials? Nuclear Membrane What structure regulates the entry and exit of molecules from the nucleus? Pore 5 Chapter 4 – Cell structure Ribosomes *A ribosome consists of two subunits which come together as a functional ribosome only when the ribosome is actively making a polypeptide. Give the function of ribosomes. Carry out protein synthesis What substances composed ribosomes? Ribosomal RNA and proteins What part in the cell ribosomes are located? Free in the cytoplasm , but located it in the rough endoplasmic reticulum The endomembrane system What are the components of the endomembrane system? 1.Nuclear Envelope/ Membrane: Surface of the nucleus is bounded two phospholipid bilayer membranes The inner surface of the nuclear envelope is covered with a network of intermediate filament fibers. The network is known as the nuclear lamina and the filamented fibers that compose it are called Lamins 2. Lysosomes 3.Endoplasmic reticulum 4. Vacuoles 5.Golgi apparatus 6. Plasma membrane Endoplasmic reticulum (ER) Differentiate the two kinds of ER. Rough ER (with ribosomes) Smooth ER (lacks ribosomes) (Ca 2+) What are the functions of the smooth ER? Synthesizes lipids, steroids 6 Chapter 4 – Cell structure Metabolizes Carbohydrates Detoxifies drugs and poisons Stores calcium ions What are the functions of the rough ER? Has bound ribosomes Distributes transport vesicles Membrane factory for the cell Produces the proteins The internal portion of the endoplasmic reticulum is known as the Cisternal space or lumen. Golgi apparatus or body What are the functions of golgi bodies? Modifies products of the ER Manufactures certain macromolecules Sorts and packages materials into transport vesicles Golgi bodies are flattened membranous sacs called CISTERNAE. *After the vesicle(protein) goes through the Golgi apparatus it can turn into a vacuole a lysosome or stay as a protein.* - Cis face located near the endoplasmic reticulum, receives vesicle - trans is the back Protein transport through endomembrane system Describe the transport of proteins and steroids in the endomembrane system. Direction of transport of proteins out of the cell RER Golgi bodies  cell membrane Lysosome (only in animals) Lysosome is membranous sac of HYDROLYTIC enzymes What are the functions of lysosomes? 7 Chapter 4 – Cell structure Digestion (breaks down) proteins, fats, polysaccharides, nucleic acids, lipids. (White blood cells) Lysosome is a vesicle that is derived from what structure? Golgi Apparatus Vacuoles Vacuoles are membrane-bounded vesicle derived from Endoplasmic reticulum or Golgi Apparatus. What are the kinds of vacuoles? 1. Food Vacuoles- formed by phagocytosis 2. Contractile Vacuoles- found in many freshwater protists pump excess water out of cells. 3. Central Vacuole- found in many mature plant cells (very large, almost fills up all of the plant cell) Central vacuoles- large membrane vesicle in plants Give the functions of central vacuoles? Digestion, Storage, Waste disposal, Water balance, Cell growth, Protection Peroxisomes What is peroxisome and what is its function? Specialized metabolic alts, Produces catalase. -Highly reactive molecules such as hydrogen peroxide are generated. -O2 is used to help break down lipids. What is the action of catalase? Breaks hydrogen peroxide H2O2 H2O + O2 8 Chapter 4 – Cell structure Plasma membrane Give the functions of the plasma membrane. Regulates transport Shape and protection Plasma membrane is semi-permeable? What is meant by semi-permeable? Semi-permeable it only lets some substances to pass through What macromolecules composed plasma membrane? Proteins and phospholipids Mitochondria (absent in bacteria cells) Mitochondrion has double membrane, the outer and inner membranes. The inner membrane is called CRISTA. Why is the inner membrane wavy or have folds? To increase the surface area, this is where ATP is generated What are contained in the matrix of the mitochondria? Ribosomes What is the function of the mitochondria? Sites of cellular respiration Chloroplast What is the function of chloroplast? Site of photosynthesis SUNLIGHT ATP, NADPH  GLUCOSE The green pigment in the chloroplast is called CHLOROPHYLL. Thylakoids that are stacked together is called GRANUM. And the space is called a STROMA. The liquid portion in the chloroplast is called the STROMA 9 Chapter 4 – Cell structure The Endosymbiont theory What are the similarities of mitochondria and chloroplast with bacteria? -Contain free ribosomes and circular DNA molecules - grow and reproduce somewhat independently in cells. Discuss the formation of mitochondria and chloroplast by the endosymbiont theory? An early ancestor of eukaryotic cells engulfed a nonphotosynthetic prokaryotic cell, which formed an endosymbiont relationship with its host. The host cell and endosymbiont merged into a single organism, a eukaryotic cell with a mitochondrion. Host cell eats nonphotosynthetic prokaryotic mitochondrion Host cell eats photosynthetic prokaryotic chloroplast Cytoskeleton What are cytoskeletons and what are their functions? Network of fibers extending throughout the cytoplasm Functions: support and give shape, motility What are the components of cytoskeletons? Describe each. Microtubules; thickest, 9+2 ,originate from a basal body Microfilaments (actin filaments)- thinnest : Pinching, cellular crawling Intermediate filaments – diameters in a middle range Centrosomes and centrioles (only in animal cells) What are centrosomes and centrioles and what are their functions? Short cylinders Functions: In animal cells microtubules grow out from a centrosome near the nucleus. “Microtubule-organizing center”(in plant cells but not the actual centrosome and are found in the nuclear membrane). Has a pair of centrioles, each with nine triplets of microtubules arranged in a ring. Cell wall (only in plants, fungi and bacteria) 10