FUNCTIONAL ANATOMY OF PROKARYOTIC AND EUKARYOTIC CELLS Lecture 2 By : Norhidayah Abd Aziz
WHAT IS LIFE? Can grow i.e. increase in size. Can reproduce offspring Responsive to environment survival Metabolism can acquire and utilize energy
microoganism BACTERIA ARCHEA EUCARYA VIRUSES PROKARYOTE genetic material (DNA) is NOT housed within a true nucleus PROKARYOTE genetic material (DNA) is housed within a true nucleus acellular
ORIGIN OF CELL - PROKARYOTE -
PROKARYOTE Microscopic single-celled organism that has neither a distinct nucleus with a membrane nor other specialized organelles lack a membrane-bound nucleus. - genetic material is present in the nucleoid
PROKARYOTE cont Prokaryotic Cell Characteristics: Simplest organisms - simple internal organization Very small (1 to 10 microns across) Genetic material in the nucleoid No membrane-bound organelles Capsules Cytoplasm Two types/domain of prokaryotes: 1. Archaea 2. Bacteria
BACTERIA Habitat varies. Most are harmless or helpful, but some are pathogens, causing disease in humans and other animals. Most bacteria have cell walls that contain peptidoglycan. Described in terms of their general shape. Common shapes include spherical (coccus), rod-shaped (bacillus), or curved (spirillum, spirochete, or vibrio)
ARCHEA VS Bacteria? different evolutionary histories significant differences in genetics, metabolic pathways, the composition of their cell walls and membranes. archaeal cell walls do not contain peptidoglycan, composed of a similar substance called pseudopeptidoglycan. in nearly every habitat on earth, even extreme environments (extreme cold, hot, basic, or acidic). Some archaea live in the human body, but none have been shown to be human pathogens.
ARCHEA vs BACTERIA
Prokaryotic cell walls 1) Surround and protect cell and maintain cell shape 2) Composed of polysaccharides (sugar coated) Bacterial cell walls composed of peptidoglycan- significant? Archaean cell walls lack peptidoglycan WHICH OF THESE TWO THAT YOU INTERESTED IN?????
PROKARYOTIC CELL STRUCTURE - 1) Cell Wall Bacterial cell wall FUNCTIONS Structure for viability. Protects the cell from mechanical damage and from osmotic rupture or lysis Provide ligands for adherence. 1) Receptor sites for drugs or viruses. 2) They are one of the most important sites for attack by antibiotics. They provide immunological variation among strains of bacteria
Two Types of Bacterial Cell Walls Gram Positive Gram Negative
Cell Wall - Structure Almost all bacteria can be divided into two large groups based on the levels of peptidoglycan and physical properties of their cell walls. Gram positive Gram negative Gram-positive Gram-negative
Gram-Positive cell walls The cell wall is thick (15-80 nanometers), consisting of several layers of peptidoglycan. Running perpendicular to the peptidoglycan sheets are a group of molecules called teichoic acids which are unique to the Gram-positive cell wall. 1. Wall teichoic acid links to peptidoglycan 2. Lipoteichoic acid links to plasma membrane Figure 4.13b
Gram-Negative cell walls The cell wall is relatively thin (10 nanometers) and is composed of: 1. A single layer of peptidoglycan 2. Outer membrane - part of the cell wall. Outer membrane composition is distinct from that of the cytoplasmic membrane Unique component, lipopolysaccharide (LPS or endotoxin), which is toxic to animals. O polysaccharide part - antigen Lipid A - endotoxin Porins (proteins) form channels through membrane Protection from phagocytes, complement, antibiotics.
Cell wall Thick peptidoglycan Teichoic acids Gram +ve cell walls Gram ve cell walls Thin peptidoglycan No teichoic acids Outer membrane Lipid A
Flagella Long filamentous appendages of a filament, hook, and basal body Outside cell wall Made of chains of flagellin Attached to a protein hook Anchored to the wall and membrane by the basal body
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Flagella Function - locomotion Rotate flagella to run, swim or tumble Some bacteria can swarm Move toward or away from particular stimuli (taxis) chemotaxis and phototaxis Flagella proteins are H antigens useful for distinguishing among variation within the species
Axial Filaments Endoflagella Structure similar to flagella Located in the periplasmic space (between the cell membrane and outer membrane), anchored at one end of a cell Rotation causes cell to move In Spirochaetes Figure 4.10a
Fimbriae and pili Fimbriae - hair like appendages that are shorter, straighter and thinner then flagella Used for attachment Pili are usually longer than fimbriae, only one or two per cell Used to transfer DNA from one cell to another - conjugation
Plasma Membrane
Plasma Membrane - FUNCTIONS Osmotic or permeability barrier. Location of transport systems for specific solutes (nutrients and ions). Energy generating functions Involving respiratory and photosynthetic electron transport systems establishment of proton motive force, and ATPsynthesizing ATPase Synthesis of membrane lipids including lipopolysaccharide in Gram-negative cells Synthesis of murein (cell wall peptidoglycan) Coordination of DNA replication and segregation with septum formation and cell division Location of specialized enzyme systems CO 2 fixation - Photosynthetic pigments nitrogen fixation Figure 4.15
Cytoplasm Cytoplasm is the substance inside the plasma membrane Consist of about 80% water Contains primary proteins (enzymes),carbohydrates, lipids, inorganic ions and many low-molecular weight compounds Protein filaments most likely responsible for the rod and helical cell shapes of bacteria Figure 4.6a, b Figure 4.6 - Overview
Nuclear Area Nuclear area - Nucleoid - bacterial chromosome Long, continuous, circularly arranged double stranded DNA Not surrounded of nuclear membrane The chromosome is attached to the plasma membrane In actively growing bacteria, as much as 20% of the cell volume is occupied by DNA. Figure 4.6a, b
Plasmids Small circular, double-stranded DNA molecules. Extrachromosomal genetic elements They replicate independently of chromosomal DNA The cell can carry from one to hundreds of copies of a plasmid Contain 5 100 genes, generally not crucial for the survival of bacteria under normal environmental condition. Plasmids may carry genes for such activities as antibiotic resistance, tolerance to toxic metals, the production of toxins, and the synthesis of enzymes. Plasmids can be transferred from one bacteria to another. Important tools in genetic engineering
Ribosomes cellular structures which function as the sites of protein synthesis Prokaryotic cell contains tens of thousands of this small structures, which give the cytoplasm a granular appearance
Ribosomes Ribosomes are composed of two subunits small and large The subunits consists of: 1) Very large RNA molecules (known as ribosomal RNA or rrna) 2) Multiple smaller protein molecules Prokaryotic and Eukaryotic ribosomes differ in the number of proteins and rrna molecules they contain. Prokaryotic ribosomes are called 70S ribosomes 1) A small unit 30S - one molecule of RNA - rrna 2) A larger 50S subunit two molecules of RNA
Endospores Resting cells formed for survival Sporulation: Endospore formation Resistant to desiccation, heat, chemicals Bacillus, Clostridium Germination: Return to vegetative state
Endospores Sporulation - endospore formation 1) Spore septum 2) Forespore - a structure entirely enclosed 3) within the original cell 4) Peptidoglycane layers 5) Spore coat 6) Release Endospore core contains 1) DNA, 2) Small amounts of RNA, 3) Ribosomes, 4) Enzymes 5) Few important small molecules.
Reproduction (Cell division) Binary fission
EUKARYOTE
Eukaryotic Cells Comparing Prokaryotic and Eukaryotic Cells Prokaryote comes from the Greek words for prenucleus. Eukaryote comes from the Greek words for true nucleus. uni- or multicellular eukaryotes such as protists, fungi, plants, and animals. Protist Algae and protozoa
ALGAE PROTOZOA FUNGI ANIMAL/PLANTS plant-like protists can be unicellular or multicellular cell walls made of cellulose, Photosynthetic organisms thus crucial for ecosystem (waste products use for energy) Industrially important ie: carrageenan or alginic acid. Nutrient agar to grow microorganisms in a Petri dish. Developing source for biofuels. Very diverse. Movement: i) hair-like structures called cilia ii)whip-like structures called flagella. iii)extended cell membrane and cytoplasmic extension name pseudopods ( false feet ). Most protozoa are harmless, but some are pathogens that can cause disease in animals or humans Non-photosynthetic, and their cell walls are usually made out of chitin rather than cellulose. Unicellular fungi (Yeasts) use in bread making industry. Some even cause diseases, such as vaginal yeast infections and oral thrush Multicellular fungi (molds). Molds are made up of long filaments that form visible colonies. Produce penicillin, and cyclosporine, used to prevent organ rejection following a transplant.?
Prokaryotic flagella rotate, Eukaryotic flagella wave Eukaryotic Flagella and Cilia
Flagella and Cilia Flagella are few and long (motility), cilia are numerous and short (motility and move substances along cell surface) Microtubules 9 pairs + 2 arrangements
Plasma Membrane Selective permeability allows passage of some molecules Simple diffusion Facilitative diffusion Osmosis Active transport Endocytosis Phagocytosis: Pseudopods extend and engulf particles (solids) Pinocytosis: Membrane folds inward bringing in fluid and dissolved substances (liquids)
Organelles Specialized membrane-bound structure in cytoplasm: Nucleus ER Golgi complex Lysosome Vacuole Mitochondrion Chloroplast Contains chromosomes (DNA) Site of protein translation, ribosomes Membrane formation, Protein modification and secretion Digestive enzymes Brings food into cells and provides support Cellular respiration (ATP) Photosynthesis Peroxisome Oxidation of fatty acids; destroys H 2 O 2
Eukaryotic Nucleus (storage of genetic materials) Figure 4.24
Endoplasmic Reticulum Rough ER contains ribosomes site of protein translation Smooth ER performs various functions: Synthesizes phospholipids, fats, steroids In liver: glucose release and detoxify toxins Creates vesicles Figure 4.25
Golgi Complex Golgi complex modifies, sorts, and packages proteins received from the ER; discharges proteins via exocytosis; replaces portions of the plasma membrane; and forms lysosomes (digestive enzymes). Figure 4.26
Lysosomes (digestive enzymes) Figure 4.22b
Vacuoles (storage of toxins, food, water) Figure 4.22b
Mitochondrion (furnace of the cell) Site of the Krebs Cycle, which produces the energy currency of the cell - ATP Figure 4.27
Chloroplast (photosynthesis) Structure similar to mitochondria the reverse side of respiration: C 6 H 12 O 6 + O 2 = H 2 O + CO 2 + ATP Photosynthesis: H 2 O + CO 2 + sun = C 6 H 12 O 6 + O 2 Figure 4.28
Endosymbiotic Theory Learning objective: Discuss evidence that supports the endosymbiotic theory of eukaryotic evolution. Mitochondria and chloroplasts resemble bacteria in size and shape as do their ribosomes These organelles contain circular DNA like prokaryotes and can reproduce apart from their host cell Figure 10.2
Prokaryote Cell membrane Cytoplasm One circular chromosome, not in a membrane No histones No organelles Peptidoglycan cell walls Binary fission Eukaryote Cell membrane Cytoplasm Paired chromosomes, in nuclear membrane Histones Organelles Polysaccharide cell walls Mitotic spindle
microoganism BACTERIA ARCHEA EUCARYA VIRUSES PROKARYOTE genetic material (DNA) is NOT housed within a true nucleus PROKARYOTE genetic material (DNA) is housed within a true nucleus acellular
VIRUSES
Doesn t belong to any kingdom -It s not a plant or an animal. -It s not a fungi, protist, or bacteria. WHAT IS A VIRUS?
A virus is an infectious agent made up of nucleic acid (DNA or RNA) wrapped in a protein coat called a capsid. Has no nucleus, no organelles, no cytoplasm or cell membrane Non-cellular This is why it does NOT belong to any domain/kingdom. vs
1. Has either DNA or RNA but NOT both. 2. Viruses with RNA that transcribe into DNA are called retroviruses. 3. Parasitic organism that depends entirely upon another living organism (a host) for its existence in such a way that it harms that organism. 4. Obligate intracellular parasite 5. Some has enzyme inside the virions HIV Infected Cell Viruses may be classified based on their type of genome (Baltimore classification): Class I : dsdna viruses, i.e. with double stranded DNA genome Class II : ssdna viruses, i.e. with single stranded DNA genome Class III : dsrna viruses, i.e. with a double stranded RNA genome Class IV : (+)ssrna viruses, i.e. with a positive sense, single stranded RNA genome, the genome itself acting as mrna Class V : (-)ssrna viruses, i.e with a negative sense, single stranded RNA genome used as a template for mrna synthesis Class VI : ssrna-rt viruses, i.e. with a positive sense, single stranded RNA genome but with a DNA intermediate not only in replication but also in mrna synthesis Class VII : dsdna-rt viruses
1. Bacteriophage viruses that infect bacteria (host) Capsid (protein coat) inside contains either RNA or DNA
FLU viruses that infect (host) DNA or RNA Surface Marker Capsid (protein coat)
Replication is how a virus spreads. A virus CANNOT reproduce by itself Must invade a host cell and take over the cell activities, eventually causing destruction of the cell and killing it. (The virus enters a cell, makes copies of itself and causes the cell to burst releasing more viruses.) Virus attaches to cell. DNA/RNA injected into cell. Step 1 Step 2 Step 3 DNA/RNA is copied. Virus copies itself. Cell bursts (lyses) and releases new viruses. Step 4 Step 5
Certain viruses can only attack certain cell types. They are said to be specific. Example: The rabies virus only attacks brain or nervous cells. Surface Markers Virus Receptor Sites It s like the pieces of a puzzle. The ends have to match up so only certain pieces fit. Cell
A virus recognizes cells it can infect by matching its surface marker with a receptor site on a cell. Surface Markers Virus Cell Receptor Sites
Importance: *Harmful Causes disease pathogenic Disease producing agent pathogen Human Diseases: Warts, common cold, Influenza (flu), Smallpox, Ebola, Herpes, AIDS, Chicken pox, Rabies Viruses disrupt the body s normal equilibrium/balance Viruses can be prevented with vaccines, but NOT treated with antibiotics. (antibiotics treat bacteria) Beneficial: Genetic Engineering harmless virus carries good genes into cells.
Structure RNA or DNA core (center), protein coat (capsid) Cell membrane, cytoplasm, genetic material, organelles Reproduction Copies itself only inside host cell--replication Asexual or Sexual Genetic Material DNA or RNA DNA and RNA Growth and Development NO YES Multicellular Organisms Obtain and Use Energy Response to Environment NO NO YES YES Change over time NO YES
How many characteristics of life do viruses possess? *Genetic Material Are viruses living?