CHAPTER #4 LO

THE PROKARYOTIC CELL (a generalized bacterium)

-makes up a group of very small unicellular organisms such as bacteria and archaea, majority are bacteria -components: cell wall, plasma membrane, nucleoid, plasmids, ribosomes, inclusions, flagella, fimbriae, pili, capsule

Define endosymbiosis and ectosymbiosis. Explain the difference. What organisms are described in pg. 94?

endosymbiosis: one of the symbiotic organisms lives inside the other ectosymbiosis: a parasite lives on the body surface of the host, including internal surfaces such as the lining of the digestive tube and the ducts of glands.

Describe the difference in the subunit size between eukaryotic and prokaryotic ribosome

eukaryotic ribosome: - larger size (80S) - smaller size (70S) in organelles prokaryotic ribosome: - smaller size (70S)

Determine the length of the flagella & the type of flagellum arrangement in Fig. 4.9b

length: 0.8μm type: peritrichous flagella

Name the genera of bacteria that produce endospores

- Clostridium and Bacillus

TEM: a portion of the cell wall of a gram negative bacterium. How would a TEM of the cell wall of a gram positive bacterium differ from this one?

- TEM (looks at internal, fine details) - it would not include an outer membrane or visible periplasm

Cell Wall: define periplasmic space

- The periplasm is a concentrated gel-like matrix in the space between the inner cytoplasmic membrane and the bacterial outer membrane called the periplasmic space in gram-negative bacteria. - rich with proteins, acts like a cytoplasm but without ribosomes

Cell Wall: describe the action of lysozyme and explain whether lysozyme should have the same effect on both the gram positive and gram negative bacteria

- an enzyme that attacks bacterial cell walls. - it degrades cell walls by breaking the glycosidic bond of peptidoglycan - adds water to (hydrolyzes) the glycosidic bond between N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG). - it's MOST effective against Gram positive bacteria since the peptidoglycan layer is easily accessible to the enzyme; lysozyme is effective against Gram negative bacteria but some of the outer membrane remains.

Describe the structure & function of endoflagella or axial filaments

- bundles of fibrils that arise at the ends of the cell beneath an outer sheath and SPIRALS around the cell - allow spirochetes (group of bacteria that have unique structure & motility) to move - similar structure to flagella EXCEPT THAT THEY WRAP AROUND THE CELL

Define selective permeability of the plasma membrane and discuss its significance

- certain molecules and ions are allowed through the membrane but others are stopped allowed: small molecules that dissolve easily in lipids; water, oxygen, CO2, simple sugars, non polar organic molecules NOT: large molecules; proteins allowed, but happens slowly: ions

Cell Wall: describe the structure of the outer membrane of gram negative bacteria (Fig. 4.13)

- consists of 1 or a very few layers of peptidoglycan and an additional membrane, an outer membrane (extra protection) - outer membrane consists of o Phospholipids o Lipopolysaccharides (Lipid A-endotoxin) o O polysaccharide (O157) o Porin, transport o Permeation barrier

Cell wall: name the building blocks of peptidoglycan and the linkage (Fig. 4.12)

- consists of a repeating disaccharide connected by polypeptides to form a lattice that surrounds and protects the entire cell - the disaccharide is made up of monosaccharides called N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM). - the linkage between these is called β-1,4

Cell wall: describe the cell wall structure of gram positive bacterium (Fig. 4.13)

- consists of many layers of peptidoglycan, forming a thick rigid structure - the structure of peptidoglycan in gram +: together the carbohydrate backbone (BROWN glycan portion) and tetrapeptide side chains (PINK peptide portion) make up peptidoglycan. - small arrows indicate where penicillin interferes with the linkage of peptidoglycan rows by peptide cross-bridges

Describe the structure & function of fimbriae

- help bacteria adhere to surfaces in the body - involved in forming biofilms ( a collective of one or more types of microorganisms that can grow on many different surfaces) and other aggregations on the surfaces of liquids, glass, and rocks - shorter, straighter, and thinner than flagella - can be a few to several hundred per cell - structure consists of a protein called pilin

Define slime layer

- if the substance is UNorganized and only loosely attached to the cell wall

Define capsule

- if the substance is organized and is firmly attached to the cell wall, the glycocalyx is called a capsule - its presence can be determined using negative staining - may protect pathogens from phagocytosis (the ingestion & digestion of microorganisms & other solid particles) - are important in contributing to the degree to which a pathogen causes disease

Define the function and structure of ribosomes (Fig 4.19)

- in both prokaryotes & eukaryotes - where protein synthesis takes place composed of 2 subunits (each consists of protein and rRNA) 1. small 30S subunit 2. large 50S subunit * these 2 subunits complete 70S prokaryotic ribosome

Describe the structure & function of pili

- involved in motility and DNA transfer 1. twitching motility: results in short/jerky intermittent movements 2. gliding motility: results in smooth gliding movements of most myxobacteria - longer than fimbriae - only 1 or 2 per cell - structure consists of a protein called pilin

Explain why UNencapsulated strains of Steptococcus pneumoniae CANNOT cause pneumonia

- it only causes pneumonia when the cells are protected from being destroyed by phagocytosis by a polysaccharide capsule - since UNencapsulated strains DO NOT have capsules, the cells are not longer protected & are destroyed by phagocytosis

Be able to recognize the plasma membrane shown in the TEM (Fig 4.14)

- it's the inner purple outline

Draw a portion of the plasma membrane as shown in Fig 4.14 and identify the major structural components; and list functions associated with these structural components

- lipid bilayer:

Define glycocalyx & its function

- means "sugar coat"; general term used for substances that surround cells - (capsule, slime layer, or extracellular polysaccharide) is a gelatinous polymer that is composed of polysaccharide, polypeptide, or both - made inside the cell and secreted to the cell surface - it strengthens the cell surface, helps attach cells together, and may contribute to cell-cell recognition

List major functions of the bacterial cell wall

- prevent bacterial cells from rupturing when the water pressure inside the cell is GREATER than that outside the cell - helps maintain the shape of a bacterium - serves as a point of anchorage for flagella - it contributes to the ability of some species to cause disease and is the site of action of some antibiotics - its chemical composition is used to differentiate major types of bacteria

Define bacterial inclusion. Give at least one example. (Fig 4.20)

- reserve deposits found in eukaryotes & prokaryotes - sites of viral multiplication ex: Magnetosomes: inclusions of iron oxide surrounded by the invagination of the plasma membrane; act like magnets; bacteria may use them to move downward until they reach a suitable attachment site

Define endospore & list its functions

- resting structures formed from gram positive bacteria - they allow survival during adverse environmental conditions

Define organelle

- structures with specific shapes and specialized functions and are characteristics of eukaryotic cells - includes the nucleus, ER, golgi complex, lysosomes, vacuoles, mitochondria, chloroplasts, peroxisomes, and centrosomes - not all described are found in all cells... -certain cells have their own type and distribution of organelles based on specialization, age, and level of activity

Describe the function of nuclear pores

- tiny channels in the membrane - allow the nucleus to communicate with the cytoplasm - they control the movement of substances between the nucleus & the cytoplasm

THE EUKARYOTIC CELL: Define endocytosis

- used by eukaryotic cells - when a segment of the plasma membrane surrounds a particle or large molecule, encloses it, and brings into the cell - 3 types 1. phagocytosis: pseudopods engulf particles, brings them in - used by WBC to destroy bacteria and foreign substances 2. pinocytosis: plasma membrane folds inwards, brings extracellular fluid into cell, along with whatever substances in fluid 3. receptor mediated endocytosis: substances (ligands) bind to receptors in the membrane; membrane folds inwards - one of the way viruses can enter animal cells

Define chromatin

- when the cell is not reproducing, the DNA and its associated proteins appear as this threadlike mass - during nuclear division, the chromatin coils into shorter & thicker rodlike bodies called chromosomes

Describe the 4 groups of eukaryotic microorganisms & give 2 examples for each group

1. Fungi ( mushrooms, yeasts, molds) 2. Protozoa ( Euglena, Amebae) 3. Algae ( pond alga Volvox) 4. Animal parasites ( flat worms, round worms)

Cell Wall: Name the 3 structural components found in the lipopolysaccharide (LPS)

1. Lipid A: embedded in the top layer of outer membrane; it's an endotoxin associated with infections by gram negative bacteria 2. a core polysaccharide: attached to Lipid A and contains unusual sugars; provides stability 3. an O polysaccharide: extends outward from the core polysaccharide and is composed of sugar molecules; functions as an antigen & is used to distinguish species of gram negative bacteria

Name the 2 major groups of prokaryotic organisms

1. bacteria 2. archaea

Organelles found in a generalized eukaryotic cell & describe the function of each

1. nucleus: contains most of the cell's DNA 2. rough ER: its attached ribosomes=protein synthesis & transport occur 3. smooth ER: lipid synthesis 4. golgi complex: membrane formation & protein secretion 5. lysosomes: formed in golgi; store digestive enzymes 6. vacuoles: derived from golgi; found in plant cells that store various substances & provide rigidity to leaves & stems 7. mitochondria: primary sites of ATP production; contain 70S ribosomes & DNA; multiply by binary fission 8. chloroplasts: contain chlorophyll & enzymes for photosynthesis; contain 70S ribosomes & DNA; multiply by binary fission 9. peroxisomes: where a variety of organic compounds oxidized 10. centrosomes: involved in formation of mitotic spindle & microtubules

Name the 2 groups of bacteria that have endoflagella

2 types of spirochetes: 1. Treponema pallidium (cause of syphilis) 2. Borrelia burgdorferi (cause of lyme disease)

Describe the structure & function of flagella

Flagella - long filamentous appendages that propel bacteria - allows the cell to move 3 main parts 1. a filament: long outermost region; contains flagellin protein 2. hook: filament is attached to this; consists of a different protein 3. basal body: anchors the flagellum to the cell wall & plasma membrane

Define isotonic, hypotonic, and hypertonic solutions a) describe structural changes a bacterium may experience b) *next card

Isotonic: inside concentration = outside concentration - no structural change Hypotonic: concentration outside is higher than concentration inside (water moves into the cell) - if cell wall is strong; it contains the swelling - if cell wall is weak/ damaged; it will burst (osmotic lysis) Hypertonic: concentration inside is higher than concentration outside - water moves out of the cell, causing cytoplasm to shrink (plasmolysis)

Define nucleoid, bacterial chromosome, and plasmids

Nucleoid: in bacteria; contains bacterial chromosomes Bacterial chromosome: a single long, continuous, & frequently circularly arranged thread of double-stranded DNA; cell's genetic information-which carries all the information required for the cell's structures & functions Plasmids: in bacteria; double-stranded DNA molecules; extrachromosomal genetic elements that contain from 5 to 100 genes that are are not crucial for survival under normal conditions. Can be an advantage under certain conditions (may carry genes for antibiotic resistance, etc.)

Compare the cell walls of gram positive and gram negative with regard to: peptidoglycan, teichoic acids/lipoteichoic acids, outer membrane, and periplasmic space (Table 4.1)

Peptidoglycan GP: thick, multilayered GN: thin, single-layered Teichoic acids/ lipoteichoic acids GP: present GN: absent Outer membrane GP: absent GN: present Periplasmic space GP: granular layer; between plasma membrane & peptidoglycan layer GN: periplasm; between plasma membrane & outer membrane

Define rough ER & smooth ER; list associated functions

Rough ER: its outer surface is studded with ribosomes=the site of protein synthesis & transport Smooth ER: no ribosomes on outer surface; does have unique enzymes = functionally more diverse - lipid & steroid synthesis ex. estrogens & testosterone

Define osmosis

The net movement of water molecules across a semi-permeable membrane from an area of high concentration of water molecules to an area of low concentration of water molecules

b) Define turgidity, osmotic lysis, plasmolysis

Turgidity: state of being swollen due to high fluid content Osmotic lysis: bursting of a weak/ damaged cells (hypotonic) Plasmolysis: process in which cells lose water (hypertonic)