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Transcript
Cell Biology Unit Eight Viruses Viruses are non-living structures that are obligatory parasites of living cells Viruses are cell specific, causing a variety of diseases in almost all organsisms Viruses Viruses are considered non-living because of the following: * not made of cells * no organelles * cannot metabolize * they replicate, not reproduce Viruses All viruses are comprised of a nucleic acid encapsulated by protein The nucleic acid can be DNA or RNA and may be single or double stranded Viruses The proteins form a coat around the nucleic acid called a capsid Some viruses will also have an envelope made of the cell membrane stolen from a host cell Viruses Viruses are very small and come in a variety of shapes * liver cell = 20µm RBC = 8µm E. coli = 2µm typical virus = .02µm Viruses Viral Replication Cycles Viral Replication Cycles Viral Replication Cycles Retroviruses Prokaryotic Cells Prokaryotic Cells Coccus Bacillus Spirillus Prokaryotic vs. Eukaryotic Cells Prokaryotic vs. Eukaryotic Cells Ecological Impact of Bacteria Bacteria have three major ecological impacts: ~ decomposers (vast majority) ~ nitrogen fixers ~ pathogens Ecological Impact of Bacteria Most bacteria are decomposers, breaking down dead organisms, lost or shed organismal parts & organic wastes Bacterial decomposers break down organic compounds into their elemental states Ecological Impact of Bacteria Decomposition is vital to all mineral cycles in that nutrients and minerals are returned to the soil for use by other organisms As a result of their decomposing activities bacteria act as a natural “maid”, cleaning up after everyone else Ecological Impact of Bacteria Nitrogen makes up 78% of the atmosphere in the form of N2 In this form nitrogen is unusable to organisms due to its triple bonding A large complex of bacteria fix nitrogen by converting into a form that can be used by organisms Ecological Impact of Bacteria Nitrogen fixing bacteria live in the soil and in nodules on the roots of certain types of plants (legumes) The bacterial complex carries out a series of reactions that break the bonds of N2, converting it to nitrates and nitrites Ecological Impact of Bacteria Ecological Impact of Bacteria Some bacteria negatively impact their environment by being pathogenic parasites Bacterial pathogens cause disease by secreting toxins that can poison or destroy cells Ecological Impact of Bacteria Bacterial pathogens impact fungi, plants and animals Human diseases caused by bacteria are numerous – typhoid, pneumonia, cholera, tetenus, tuberculosis, diptheria, plague, botulism, gonorrhea, syphilis, etc. Bacterial Metabolism Bacterial metabolism exhibits a number of different strategies: > photosynthesizing > heterotrophic consumers > aerobic & anaerobic respiration Bacterial Metabolism This versatility could create problems with overproduction of synthesized materials Bacteria conserve energy and materials by not producing inductable enzymes if they are not needed at the moment (induced synthesis) Bacterial Metabolism Feedback inhibition is used to block overproduction of synthesized materials by constituative enzymes Repression system blocks the production of the enzymes needed to produce a product already available Prokaryotic Genetic Material Prokaryotic DNA is composed of the same materials that of eukaryotic cells It is not found in a nucleus, but is localized in a region called the nucleoid The DNA molecule is circular is shape, being supercoiled and bound to proteins, then folded into an extensive series of loops Prokaryotic Genetic Material Plasmids are small circular molecules of DNA that can replicate themselves and genes for other cell functions (usually non-essential) Bacterial cells may contain one or more plasmids Prokaryotic Genetic Material Plasmids are found in three forms: + F factors – used in conjugation (fertility) + R factors – used in resistance to harmful drugs, etc. + Col factors – used to produce colicins (kill other bacteria) Recombinant DNA DNA Cloning Genetic Engineering Tissues The next organizational level of life above the cell is that of tissue A tissue is a group of similar cells that work in conjunction with each other to perform a specific function Plant Tissues Plant tissues can be divided into five main types: + growth tissue + surface tissue + ground tissue + vascular tissue + photosynthetic tissue Plant Tissues Growth tissues are the regions that enable a plant to grow both in length and in girth Plants grow throughout their life span, so these tissues are continually producing new growth Plant Tissues Plant growth tissues are called meristems Apical meristems produce growth in length (primary growth) and are found on the tips of stems and roots Plant Tissues Lateral meristems produce growth around the sides (secondary growth) As apical meristems increase length, lateral meristems provide the necessary support Plant Tissues Surface tissues make up the epidermis and function to protect underlying tissues and prevent water loss These tissues produce a waxy cuticle that functions to prevent water loss Plant Tissues Ground tissues are found throughout a plant, making up much of the interior of the plant These tissues function in storage, support and basic metabolism Plant Tissues Ground tissues consist of three cell types: + parenchyma – storage and metabolism + collenchyma - support + sclerenchyma - support Plant Tissues Parenchyma is the most abundant tissue, structurally unspecialized and acts as storage cells Parenchyma differentiates into chlorenchyma which can photosynthesize Plant Tissues Parenchyma also differentiates into the other two types of ground tissue cells – collenchyma & sclerenchyma Plant Tissues Vascular tissues function to carry materials throughout the plant Xylem carries water and minerals up from the roots Phloem carries sugars and nutrients down to the roots Plant Tissues Xylem is comprised of long, thin cells stacked end to end that eventually die, becoming hollow Living, functional xylem makes up the sapwood of a plant Dead, filled in xylem makes up the core heartwood of a plant Plant Tissues Phloem is comprised of wider cells in which fluids are transported from cell to cell It is found in the cambium, the living outer layer of a plant just beneath the bark Plant Tissues Photosynthetic tissue is found mainly in leaves (some in green stems) and functions to carry out photosynthesis The palisade and spongy layers are loaded with chloroplasts, carrying out most of the photosynthesis Plant Tissues Animal Tissues Animals are comprised of four types of tissue: - epithelial - connective - muscle - nervous All animals will have all four tissues represented Animal Tissues Epithelial tissues function to provide coverings or linings to structures, as well as secreting a variety of substances Animal Tissues Connective tissues provide support, adhesion, insulation and attachment Connective tissues function to “connect” tissues to other tissues or one structure to another Animal Tissues Muscle tissue functions to contract, which in turn provides movement Nervous tissue functions to send rapid messages throughout the body, reacting to stimuli and enacting responses to them Epithelial Tissues Epithelial Tissues Epithelial Tissues Connective Tissues Connective tissues are the most abundant and variable in an animal body They are comprised of living cells embedded in a nonliving matrix Connective Tissues These tissues function to fill spaces, attach epithelium to other tissues, protect & cushion organs and provide mechanical support Connective tissues include blood, bone, cartilage, adipose, loose connective (aerolar) and dense connective Connective Tissues Connective Tissues Nervous Tissue Anatomy of a Neuron Myelin Sheath Formation Anatomy of a Neuron Resting Membrane Potential Resting Membrane Potential Action Potential Action Potential Action Potential Propogation Saltatory Conduction Refractory Periods Pre-Synaptic Action Post-Synaptic Action The Reflex Arc Integrating Center Sensor Stimulus Effectors Response The Muscle Stretch Reflex Muscle Characteristics The ability to contract Excitability The property of extensibility Elastic properties Muscle Characteristics Contraction results in movement Contraction occurs due to sliding filaments Muscles contract due to nerve activity Muscles can be under voluntary or involuntary control Skeletal Muscle Characteristics Appear striated Under voluntary control Quick response time due to nerve stimulation of independently contracting muscle fibers Results in body movement and balance Smooth Muscle Characteristics Appear non-striated Under involuntary control Relatively slow response time due to stimulation produced by pacemaker potentials Results in internal organ movements and glandular secretions Cardiac Muscle Characteristics Appear striated Under involuntary control Quick response time due to pacemaker produced action potentials Cardiac Muscle Characteristics Intercalated discs connecting fibers produce simultaneous contraction Results in heart beats and the movement of blood Muscle Anatomy Muscle Anatomy Filament Arrangement Actin Filament Composition Myosin Action The Power Stroke Conduction in the Muscle Cell Motor Unit