MicroBio CH3 - Cell Structure & Function

5 Properties of Life? *present in all Bacteria, Archaea, & Eukaryotes

Growth (increases in size)

Reproduction (increase in #)

Responsiveness (ability to react to environmental stimuli)

Metabolism (controlled chemical reactions of organisms)

Cellular Structure (membrane-bound structure capable of all the above functions)

Properties of “life" in viruses

Growth: growth does not occur

Reproduction: host cell replicates the virus

Responsiveness: reaction to host cells seen in some viruses

Metabolism: viruses use host cell’s metabolism

Cellular structure: viruses lack cytoplasmic membrane or cellular structure

Viruses are not considered living

What are cells and its main components?

Bacteria, Archaea, and Protozoa: Single cell

Animals and plants: trillions of cells

*ALL CELLS: have a cell membrane made of nucleic acids, proteins, lipids, and carbs.

Have chromosomes containing DNA & ribosomes for protein synthesis

What are the eukaryotic cells?

Animals, plants, fungi, and protozoa; contain organelles that are surrounded by membranes

What about bacteria and archaea? (cells wise)

No nucleus or organelles, can engage in every activity that eukaryotic cells can

How do we organize organisms by domains?

Based on RNA sequences → bacteria and archaea (prokaryotes) and eukarya (eukaryotes)

Cell-wise components for Prokaryotic domains? (Archaea and Bacteria)

Lacks nucleus, still have DNA and make proteins

Lack cell organelles surrounded by cell membranes (also called membrane bound organelles)

Are typically 1.0 micrometer in diameter or smaller)

External structure of bacterial cells?

Glycocalyx: gelatinous, sticky substance around outside of cell → composed of polysaccharides, polypeptides, or both

2 types of glycocalyces?

Capsule: firmly attached to cell surface; can prevent bacteria from being recognized by host

Slime layer: loosely attached to cell surface, water-soluble, sticky layer allows bacteria to attach to surfaces

External structures of bacterial/prokaryotic(?) cells? (3 types)

Flagella, Fimbriae, and Pili

What is flagella?

Responsible for movement, tail like, not present on all bacteria; Functions: moves bacteria, rotation is reversible, bacteria moves in response to stimuli (ex: away from toxins, toward food), monotrichous is also called polar

What is fimbriae?

Sticky, bristle like projections, used by bacteria to adhere to one another and to environment, shorter than flagella, serve an important function in biofilms

What is Pili?

A type of fimbriae, also called conjugation pili, longer than fimbriae, shorter than flagella, bacteria usually have one or two per cell, transfer DNA from one cell to another (conjugation)

Bacterial Cell Walls, what do they consist of and help with?

Provide structure & shape, protect cell from osmosis, assist some cells in attaching to other cells in resisting antimicrobial drugs

Antibiotics often target cell walls, composed of various amounts of peptidoglycan

Scientists describe two basic types of bacterial cell walls (gram-positive/negative)

What are gram-positive bacterial cell walls?

Thicker layer of peptidoglycan, containing unique chemicals called teichoic acids & lipoteichoic acids, appear purple following Gram staining procedure

What are Gram negative bacterial cell walls?

Thin-layer of peptidoglycan, bilayer membrane outside the peptidoglycan contains phospholipids, proteins, and lipopolysaccharide (LPS); Lipid A in LPS can cause fever, vasodilation, inflammation, shock, and blood clotting

Appear pink following Gram staining procedure

Bacteria without cell walls?

A few bacteria lack cell walls (mycoplasma); have other features of prokaryotic cells such as ribosomes

Bacterial Cytoplasmic membranes’ structure?

Composed of phospholipid bilayer: lipids and associated proteins (integral & peripheral proteins)

Fluid mosaic model describes membrane structure

Bacterial Cytoplasmic membranes’ function?

Function: energy storage, harvest light energy in photosynthetic bacteria, selectively permeable, naturally impermeable to most substances, proteins allow substances to cross membrane, maintain concentration. and electrical gradient, passive processes: diffusion, facilitated diffusion, & osmosis.

How do things get moved across membranes? (prokaryotic cytoplasmic membranes)

Passive + active transport; passive processes don’t require energy (diffusion, facilitated diffusion, and osmosis)

Osmosis?

Diffusion of water across a semi-permeable membrane

Diffusion?

Small or lipid-soluble chemicals through the membrane (from extracellular fluid to cytoplasm)

Facilitated diffusion?

Through a permease of a specific chemical

3 types of tonicity?

Isotonic solution: equal concentration of solutes on both sides

Hypertonic solution: more solutes outside of cell than outside

Hypotonic solution: more solutes inside of cell than outside

Active transport processes in bacterial cytoplasmic membranes?

*Active transport processes: cell expends energy in the form of ATP to move a substance against its electrochemical gradient

Active transport: ATP-dependent carrier proteins bring substances into cell (Na+, K+, Ca²⁺, H+, Cl-)

Group translocation: the substance is chemically altered during transport (glucose, mannose, fructose)

Cytoplasm of Bacteria; what is it composed of?

Cytosol: liquid portion of cytoplasm (mostly water, contains cell’s DNA in region called the nucleotide→not membrane bound, so it’s not nucleus)

Inclusions: may include reserve deposits of chemicals

What is also in Cytoplasm of Bacteria?

Endospores: unique structures produced by some bacteria, defensive strategy against unfavorable conditions, vegetative cells (normally growing cell) transform into endospores when nutrients limited

Resistant to extreme conditions such as heat, radiation, chemicals, ex: bacillus anthracis (anthrax) endospores

What’s in the cytoplasm of prokaryotes?

*Nonmembranous organelles; ribosomes (sites of protein synthesis, made of polypeptides and ribosomal RNA)

and Cytoskeleton: composed of several types of protein fibers; can play diff. roles in cell: cell division, cell shape, segregate DNA molecules, move through environment

What are the external structures of Archaea?

Glycocalyx (function in the formation of biofilms, adhere cells to one another and inanimate objects)

Flagella (numerous differences with bacterial flagella)

Fimbriae and Hami (many archaea have fimbriae, some make fimbria-like structures called Hami: function to attach archaea to surfaces)

Archaeal Cell walls and Cytoplasmic Membranes?

Most archaea have cells walls (do not have peptidoglycan, contain polysaccharides and proteins)

All archaea have cytoplasmic membranes (maintain electrical and chemical gradients, control import and export of substances)

Archaea cytoplasm differs from bacteria cytoplasm; diff. ribosomal proteins, diff. metabolic enzymes to make RNA, genetic code more similar to eukaryotes

Bacteria vs Archaea (prokaryotic structural differences)

Cell wall: in bacteria = contains peptidoglycan, in archaea = no peptidoglycan (may have pseudopeptidoglycan or protein layers)

Cell membrane: in bacteria = fatty acids linked to glycerol by ester bonds, in archaea = branched hydrocarbons linked to glycerol by ether bonds

Membrane structure: in bacteria = usually a lipid bilayer, in archaea = can have a bilayer or a more stable monolayer

*Bacteria = peptidoglycan + ester bonds

*Archaea = no peptidoglycan + ether bonds

In eukaryotic domain, what do eukaryotes have cell-wise?

Have nucleus, have internal membrane-bound organelles, are larger and more complex (10-100 micrometer in diameter), composed of algae, protozoa, fungi, animals, and plants

What is the external structure of eukaryotic cells?

Glycocalyces (glycocalyx): not as organized as prokaryotic version, help anchor animal cells to each other, strengthen cell surface, provide protection against dehydration, function in cell-to-cell recognition and communication

Eukaryotic Cell walls, what are they composed of?

*Fungi, algae, plants, and some protozoa have cell walls

Composed of various polysaccharides: plant cell walls = cellulose

Fungal cell walls = chitin

Algal cell walls = polysaccharides

Animals and most protozoa do not have cell walls

What are cytoplasmic membranes?

All eukaryotic cells have cytoplasmic membranes (cell membranes)

Contain phospholipids and proteins

Contain steroid lipids to maintain fluidity

Control movement into & out of cell

What active transport processes are found only in eukaryotes?

Endocytosis (phagocytosis & pinocytosis): substances are surrounded by pseudopods and brought into the cell, phago. involves solid substances, Pino. involves liquids (ex: bacteria, viruses, aged and dead cells, liquid nutrients in extracellular solutions)

Exocytosis: vesicles containing substances are fused with cytoplasmic membrane, duping their contents to the outside (ex: wastes, secretions)

Two movement types for cytoplasm of eukaryotes?

Flagella: differ structurally and functionally from prokaryotic flagella, may be single or multiple; usually found at one pole of cell, function: do not rotate but undulate rhythmically

Cilia: shorter and more numerous than flagella, movement propels cells through their environment, also used to move substances past surface of cell

(off chapter) What chemical tests distinguish archaea from bacteria?

Test for peptidoglycan (NAM present in bacteria only)

Antibiotic sensitivity (sensitive = likely bacteria, resistant = archaea

Lysosome sensitivity (bacteria lyse, archaea do not)

Lipid analysis (bacteria = ester-linked fatty acids, archaea = ether-linked lipids

Gram stain (indirect clue): thick peptidoglycan → Gram-pos. bacteria (purple), Gram-neg. bacteria (pink), Archaea → usually don’t stain b/c they lack peptidoglycan

Chromatography or mass spectrometry: to detect peptidoglycan components like N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), and archaea lack NAM entirely

What do Bacteria and Archaea not have compared to Eukaryotes?

*No nucleus, no mitochondria, no ER, no Golgi apparatus, no chloroplasts (but for both they do have 70S ribosomes, plasma membranes, cell walls (usually), single circular chromosomes usually, cytosol in both)

*Cytoplasm of Eukaryotes (membranous organelles series): what is the nucleus and the nucleolus?

Nucleus: contains most of the cell’s DNA, semiliquid portion called nucleoplasm (contains chromatin)

Nucleolus makes ribosomes

Surrounded by nuclear envelope (contains nuclear pores)

What is the ER in eukaryotes?

Endoplasmic reticulum; netlike arrangement of flattened, hollow tubules, functions as transport system

*Two forms: smooth endoplasmic reticulum→lipid production; rough endoplasmic reticulum→protein synthesis

What are lysosomes, peroxisomes, vacuoles, and vesicles in the cytoplasm of eukaryotes?

*Store and transfer chemicals within cells, may store nutrients in cell

Lysosomes = digestion and recycling of cellular materials (mainly animal cells + they contain catabolic enzymes)

Peroxisomes = break down fatty acids and detoxify harmful substances (contain enzymes that degrade poisonous wastes)

Vacuoles = storage (large central vacuole in plants)

Vesicles = transport materials within cell

What is the mitochondria in eukaryotic cells?

Have 2 membranes composed of phospholipid bilayer, produce most of cell’s ATP, contains 70S ribosomes an a circular molecule of DNA

What are chloroplasts in plant/eukaryotic cells?

Found in photosynthetic eukaryotes (protists); use light energy to produce ATP, have 2 phospholipid bilayer membranes and DNA, have 70S ribosomes

What are ribosomes in the cytoplasm of eukaryotes?

80S ribosomes (larger than prokaryotic ribosomes)→important for protein synthesis

What is the cytoskeleton in the cytoplasm of eukaryotes?

Extensive network of fibers and tubules, anchors organelles, produces basic shape of the cell

What are the other non membranous organelles in the cytoplasm of eukaryotes?

Centrioles: play a role in mitosis, cytokinesis, and formation of flagella and cilia

Centrosome: contains centrioles

(not in all eukaryotic cells)