Prokaryotes and Eukaryotes PDF

THE PROKARYOTES I. PROKARYOTES VS. EUKARYOTES PROCARYOTES ❖ Similarities: Contain nucleic acids, proteins, lipids, and carbohydrates - No nucleus and Organelles Use the same kinds of chemical reactions to metabolize - DNA Location: NUCLEOID food, build protein...

THE PROKARYOTES I. PROKARYOTES VS. EUKARYOTES PROCARYOTES ❖ Similarities: Contain nucleic acids, proteins, lipids, and carbohydrates - No nucleus and Organelles Use the same kinds of chemical reactions to metabolize - DNA Location: NUCLEOID food, build proteins, and store energy - Asexual ❖ Differences: Structure of cell walls and membranes, and the absence EUKARYOTES of organelles (specialized cellular structures that have - Have nucleus and Organelles specific functions) - DNA Location: Nucleus - Sexual or Asexual II. CHIEF DISTINGUISHING CHARACTERISTICS OF EUKARYOTES 1. DNA is found in the cell 's nucleus, which is separated from the cytoplasm by anuclear membrane, and the DNA is found in multiple chromosomes 2. DNA is consistently associated with chromosomal proteins called histones and with non-histone 3. Have a number of membrane-enclosed organelles 4. Cell walls, when present, are chemically simple 5. Cell division usually involves mitosis III. COMPARISON OF PROKARYOTIC AND EUKARYOTIC CELL ORGANIZATION Characteristic Prokaryote Eukaryote Typical size 0.4-2 pm in diameter 10-100 pm in 0.5-5 pm in length diameter >10 pm in length Nucleus No nuclear membrane; nucleoid region of the Classic membrane- cytosol bound nucleus Genome Location In the nucleoid, at the mesosome In the nucleus Chromosomal DNA Circular, complexed with RNA Linear, complexed with basic histones and other Genome: Plasmids, small circular molecule of DNA In mitochondria extrachromosomal -containing accessory information; most and chloroplasts circular DNA -commonly found in gram-negative bacteria; -each carries genes for its own replication; can confer resistance to antibiotics Reproduction Asexual (binary fission) Sexual and asexual Membrane-bound Absent All organelles Golgi bodies Absent in all Present in some Lysosomes Absent in all Present in some; contain hydrolytic enzymes Endoplasmic reticulum Absent in all Present in all; lipid synthesis, transport Mitochondria Absent in all Present in most Nucleus Absent in all Present in all Chloroplasts for Absent in all Present in algae and photosynthesis plants Ribosomes: site of Present in all Present in all protein synthesis Size 705 in size, consisting of 505 and 305 subunits 80 S in size, consisting of 60 S and 40 $ subunits Electron transport for In the cell membrane if present; no In the inner energy mitochondria membrane of present mitochondria and chloroplasts Sterols in cytoplasmic Absent except in Mycoplasma spp Present membrane Plasma membrane Lacks carbohydrates Also contains glycolipids and glycoproteins Cell wall, if present Peptidoglycan in most bacteria Cellulose, phenolic polymers, lignin (plants). chitin (fungi), other glycans (algae) Glycocalyx Present in most as an organized capsule or Present; some unorganized slime layer animal cells Cilia Absent Present; see description of flagella Flagella, if present Simple flagella; composed of polymers of Complex cilia or flagellin; movement by rotary action at the flagella; composed base; spirochetes have MTs of MTs and polymers of tubulin with dynein connecting MTs; movement by coordinated sliding microtubules Pili andfimbriae Present Absent IV. BACTERIA A. BACTERIA unicellular organisms that lack a nuclear membrane and true nucleus classified as prokaryotes (Greek: before karyon [nucleus]), having no mitochondria, endoplasmic reticulum (ER), or Golgi bodies. B. BACTERIAL MORPHOLOGY Vary in size, morphology, and cell-to-cell arrangements and in the chemical composition and structure of the cell wall. Bacterial cell wall differences provide the basis for the Gram stain. 1. BACTERIAL SIZE Most clinically relevant bacterial species range in size from 0.25 to 1μm in width and 1 to 3μm in length Bacterium is some hundred-fold larger than a virus, and ten-fold smaller than a eukaryotic cell ◆ NOTE: Variation of size and shape within a population may also result from asymmetric growth of the cell wall 2. BACTERIAL SHAPE Common bacterial cellular morphologies include: C - C - B - F - C - S - S - P ✓ Cocci- circular ✓ Coccobacilli- ovoid ✓ Bacillus- rod shaped ✓ Fusiform- tapered, pointed ends ✓ Curved ✓ Spiral- helical, like corkscrew ✓ Spirochetes vary in length and in the number of helical turns (**not all helical bacteria are called spirochetes) ✓ Pleomorphic- no defined shape 3. BACTERIAL ARRANGEMENT ✓ Pairs ✓ Chains ✓ Grape-like clusters ✓ Group of four ✓ Packets of eight ✓ Palisades ✓ Chinese characters V. BACTERIAL CELL STRUCTURE A. CELL ENVELOP outermost structure, comprises: Outer membrane- in gram-negative bacteria only Cell wall - composed of the peptidoglycan macromolecule (murein layer) Periplasm- in gram-negative bacteria only Cytoplasmic or cell membrane- encloses the cytoplasm ❖ THE CELL ENVELOP: THE CELL WALL AND CELL MEMBRANE A. GRAM POSITIVE CELL WALL composed of a very thick protective peptidoglycan (murein) layer consists of glycan (polysaccharide) chains of alternating N-acetyl- d-glucosamine (NAG) and N-acetyl-d-muramic acid (NAM) many antibiotics are effective against gram-positive organisms (e.g., penicillin) act by preventing synthesis of peptidoglycan ◆ NOTE: Gram-negative bacteria - thinner layer of peptidoglycan and a different cell wall structure, are less affected by these antibiotics ◼ N-ACETYL-D-GLUCOSAMINE AND N-ACETYL-D-MURAMIC ACID alternating sugar components (moieties), with the amino acid chain linked to N-acetylmuramic acid molecules polymers of these subunits cross-link to one another by means of peptide bridges to form peptidoglycan sheets layers of these sheets are cross-linked with one another, forming a multilayered, cross-linked structure of considerable strength Referred to as the murein sacculus, or sack, this peptidoglycan structure surrounds the entire cell