THE CELL STRUCTURES AND ITS FUNCTIONS

Prepared by: NR-NUR 102 TEAM 2018-2019

 1665: Robert Hooke, “Father of Microscopy,” coined the term “cells”

 1838-1839: Matthias Schleiden and Theodore Schwann concluded that all plant and animal tissues are made up of cells.

 1858: Rudolf Virchow proposed the “Theory of Biogenesis”

EUKARYOTIC CELLS

ALGAE FUNGI PROTOZOA

PLANTS

ANIMALS PROKARYOTIC CELLS

BACTERIA ARCHAEA

 Eucaryotes:  “eu” = true  “caryo” = nut or nucleus  Size: 10 to 30 µm in diameter Cell Structures Common to Most Eukaryotes

Glycocalyx Cell Membrane Nucleus Vacuoles Mitochondria Endoplasmic Reticulum Ribosomes Golgi Complex Cytoplasm Cytoskeleton GLYCOCALYX

 The outermost boundary of most eukaryotic cells

 Functions:  protection  adherence  reception of chemical signals

 Supported by either a cell wall or a cell membrane GLYCOCALYX GLYCOCALYX

 Usually composed of polysaccharides

 Appears as a network of fibers, a slime layer, or a capsule

 The layer beneath the glycocalyx varies among eukaryotes.  Fungi and most algae have a thick, rigid cell wall  Protozoa and animal cells do not have cell wall

GLYCOCALYX CYTOPLASMIC MEMBRANE

 Bilayer of phospholipids with protein molecules embedded

 Also contain sterols  Gives stability  Especially important in cells without a cell wall

 Selectively permeable Cell Membrane NUCLEUS

 Distinguishing characteristic between a eukaryotic and prokaryotic cell

 “The command center”

 Three components:  Nucleoplasm  Chromosomes  Nucleolus  Nuclear Membrane CHROMOSOMES

 consist of linear DNA molecules and proteins (histones and nonhistones)  Genes as “beads on a string” RIBOSOMES  Consists of rRNA and CHON  Primarily for CHON synthesis  Each eucaryotic (80S) ribosome consist of the ff:  Large subunit (60S subunit)  Small subunit (40S subunit)  CHON released are mostly immature Cell Structures Present in Some Eukaryotes

Cell Wall Chloroplasts Locomotor organs CELL WALL

 Provides rigidity, shape and protection  May contain the ff:  Cellulose, pectin and lignin in plant cells  Chitin or cellulose, and mixed glycans in fungi  Some minerals, pectin, and mannans in algae

Cellulose can also be found in ALGAE

Chitin is also present in the exoskeleton of beetles and crabs

PLASTIDS

 An energy producing organelle  Contains numerous photosynthetic pigments  A type of plastid, chloroplasts contains chlorophyll

 PHOTOSYNTHESIS – process by which light energy is used to convert carbon dioxide and H20 into CHO and O2 PLANT CELL STRUCTURE FLAGELLA AND CILIA

 Flagella – long, thin, whiplike structures that serve as organelles of locomotion

 Cilia – hairlike structures shorter than flagella that also serves for locomotion in a coordinated and rhythmic manner COMPARISON BETWEEN ANIMAL AND PLANT CELLS

CATEGORY PLANT CELL ANIMAL CELL Biologic All plants, fungi All animals and Distribution and algae protozoa Nuclear Membrane Present Present

Membranous structures other Present Present than cell membranes

Vacuole Size Larger Smaller COMPARISON BETWEEN ANIMAL AND PLANT CELLS CATEGORY PLANT CELL ANIMAL CELL Microtubules Present Present Cytoplasmic Ribosomes 80S 80S (Density) Composed of DNA Composed of DNA Chromosomes and CHON and CHON When present, have When present, have Flagella or Cilia a complex structure a complex structure Present, usually Cell Wall Absent contains cellulose Photosynthesis (Chlorophyll) Present Absent

A prokaryote can be distinguished from the other type of cell (a eukaryote) because of certain characteristics it possesses:

 The way its DNA is packaged  The makeup of its cell wall  Its internal structures

Prokaryotic Form and Function

CELL STRUCTURES COMMON TO ALL BACTERIAL CELLS Cell membrane Cytoplasm Ribosomes One (or a few) chromosomes CELL STRUCTURES FOUND IN MOST BACTERIAL CELLS Bacterial Cell Wall Glycocalyx CELL STRUCTURES FOUND IN SOME BACTERIAL CELLS Flagella Pili Fimbriae Capsules Slime layers Inclusions Actin cytoskeleton Endospores EXTERNAL STRUCTURES

• APPENDAGES – FLAGELLA – AXIAL FILAMENTS – FIMBRIAE / PILI • GLYCOCALYX EXTERNAL STRUCTURES

 Appendages: Cell extensions  Common but not present on all species  Can provide motility (flagella and axial filaments)  Can be used for attachment and mating (pili and fimbriae) FLAGELLA • Long filamentous appendages • Propels bacteria • Functions – Chemotaxis- positive and negative – Move by runs and tumbles Figure 4.2 FLAGELLA ARRANGEMENT AXIAL FILAMENTS

 a.k.a. Periplasmic flagella or Endoflagella  In spirochetes  Bundle of fibrils  Rotation causes cell to move. FIMBRIAE  Small, bristlelike fibers  Most contain protein  Allow attachment  Tend to stick to each other and to surfaces  Mostly responsible for microbial colonization in inanimate objects PILI  Elongate, rigid tubular structures  Made of the protein pilin  Used in conjugation – sex pilus  Most often observed in Gram (-) bacteria Figure 4.8 GLYCOCALYX  composed of repeating polysaccharide units, polypeptide (protein) or both  Protects the cell  A capsule is neatly organized, bound more tightly and is denser and thicker.  A slime layer is unorganized & loose, protects some bacteria from loss of water and nutrients

GLYCOCALYX

 Extracellular polysaccharide (EPS) allows cell to attach on various surfaces:  (rocks, plant roots, human teeth, medical implants, water pipes & even bacteria) The Cell Envelope: The Boundary layer of Bacteria

 Majority of bacteria have a cell envelope  Lies outside of the cytoplasm  Composed of two or three basic layers  Cell wall  Cell membrane  In some bacteria, the outer membrane Differences in Cell Envelope Structure  The differences between gram-positive and gram-negative bacteria lie in the cell envelope  Gram-positive  Two layers  Thick cell wall and cytoplasmic membrane  Gram-negative  Three layers  Outer membrane, thin cell wall, and cytoplasmic membrane Figure 4.12 CELL WALL

• Made of peptidoglycan (murein), NAM (N- acetylglucosamine), NAG (N-acetylmuramic acid) • Prevents osmotic lysis • Anchorage for flagella CELL WALL

 contributes to pathogenicity  site of action of some antibiotics GRAM-POSITIVE CELL WALL

 Thick layer of peptidoglycan (60-100% murein)

 Contain teichoic and lipoteichoic acids  acidic charge on the cell surface  for antigenic specificity GRAM-NEGATIVE CELL WALL

 Thin layer of peptidoglycan (10-20% murein)  more susceptible to mechanical breakage  Periplasmic space surrounds peptidoglycan  important reaction site for a large and varied pool of substances that enter and leave the cell Figure 4.14 Nontypical Cell Walls

 Some aren’t characterized as either gram- positive or gram-negative  Some don’t have a cell wall at all  For example, Mycobacterium and Nocardia- unique types of lipids The Gram-Negative Outer Membrane  Similar to the cell membrane, except it contains specialized polysaccharides and proteins  Uppermost layer- contains lipopolysaccharide  O polysaccharides – antigens and receptors  Innermost layer- phospholipid layer anchored by lipoproteins to the peptidoglycan layer below  lipid A – Endotoxin  causes fever and shock reactions such as meningitis and typhoid fever.  The negative charge produced is vital The Gram-Negative Outer Membrane  Serves as a partial chemical sieve  Only relatively small molecules can penetrate

 Access provided by special membrane channels formed by porin proteins

 block the entrance of certain antibiotics such as penicillin, digestive enzymes such as lysozyme, detergents, heavy metals, bile salts, and certain dyes. Figure 4.14

PLASMA MEMBRANE PLASMA (CELL) MEMBRANE

 Also known as the cytoplasmic membrane  Very thin (5-10 nm)  Contain primarily proteins and phospholipids  Functions:  Provides a site for functions such as energy reactions, nutrient processing, and synthesis  Regulates transport (selectively permeable membrane)  Secretion Practical Considerations of Differences in Cell Envelope Structure

 Outer membrane- an extra barrier in gram- negative bacteria  Makes them impervious to some antimicrobial chemicals  Generally more difficult to inhibit or kill than gram- positive bacteria  Cell envelope can interact with human tissues and cause disease  Corynebacterium diphtheriae  Streptococcus pyogenes  Mycobacterium species INTERNAL STRUCTURE

– CYTOPLASM – NUCLEOID • Chromosomes and Plasmids – RIBOSOMES – INCLUSIONS – ACTIN CYTOSKELETON – ENDOSPORES CYTOPLASM

 Internal matrix  Contains CHON enzymes, CHO, lipids, inorganic ions, ribosomes, and inclusions NUCLEAR AREA (NUCLEOID)  Contains a single long circular molecule of double stranded DNA called: BACTERIAL CHROMOSOMES

 There could also be plasmids.

 No histones and nuclear envelope RIBOSOMES  CHON synthesis • Some antibiotics work to inhibit protein synthesis like:

ERYTHROMYCIN CHLORAMPHENICOL Bacterial Inclusions

 Metachromatic Granules - volutin (synthesis of ATP) – found in algae, fungi, protozoa & bacteria  Polysaccharide Granules  Lipid Inclusions Figure 4.19 The Actin Cytoskeleton

 Long polymers of actin

 Arranged in helical ribbons around the cell just under the cell membrane

 Contribute to cell shape Figure 4.20 ENDOSPORES  Usually found in gram (+) bacteria  Dormant bodies produced by Bacillus, Clostridium, and Sporosarcina  Specialized resting cells  Capable of sporulation and germination  Highly durable and dessicated cells with thick walls & additional layers Endospore-Forming Bacteria

 two-phase life cycle

Phase One- Vegetative cell  Metabolically active and growing  Can be induced by the environment to undergo spore formation (sporulation) Phase Two: Endospore

 Stimulus for sporulation- the depletion of nutrients  Vegetative cell undergoes a conversion to a sporangium  Sporangium transforms into an endospore  Hardiest of all life forms  Withstand extremes in heat, drying, freezing, radiation, and chemicals through their spore coat  Heat resistance- high content of calcium and dipicolinic acid  Some viable endospores have been found that were more than 250 million years old  Germination  Breaking of dormancy  In the presence of water and a specific germination agent  Quite rapid (1 ½ hours)  The agent stimulates the formation of hydrolytic enzymes, digest the cortex and expose the core to water  Medical Significance  Several bacterial pathogens  Bacillus anthracis  Clostridium tetani  Clostridium perfringens  Clostridium botulinum  Resist ordinary cleaning methods

Endospore-Forming Bacteria

 sporulation in bacteria is not a means of reproduction Sporulation

 not a means of reproduction COMPARISON OF PROKARYOTIC AND EUKARYOTIC CELLS

 Chemically similar  Use same kinds of chemical reactions to metabolize food, build CHON & store energy  Can be distinguished by the structure of cell walls & membranes & the presence or absence of organelles

SUMMARY OF DISTINGUISHING CHARACTERISTICS

EUKARYOTES • With chromosomes • DNA is associated with chromosomal CHONs, histones & with nonhistones. • With mitotic apparatus & number of organelles, including mitochondria, endoplasmic reticulum & sometimes chloroplasts. SUMMARY OF DISTINGUISHING CHARACTERISTICS

PROCARYOTES • Genetic material is not enclosed within a membrane. • Lack other membrane – bound organelles • DNA is not associated with histone proteins • Cell walls always contain the complex polysaccharide peptidoglycan • Divide by binary fission – DNA is copied & the cell splits into 2, involves fewer structures & processes from eukaryotic cell division PRINCIPAL DIFFERENCES BETWEEN PROKARYOTIC & EUKARYOTIC CELLS CHARACTERISTIC PROKARYOTIC EUKARYOTIC 0.2-2.0 µm in 10-100 µm in CELL SIZE diameter diameter No nuclear True nucleus NUCLEUS membrane or nucleoli MEMBRANE- ENCLOSED ABSENT PRESENT ORGANELLES Consist of 2 Complex FLAGELLA protein building blocks PRINCIPAL DIFFERENCES BETWEEN PROKARYOTIC & EUKARYOTIC CELLS CHARACTERISTIC PROKARYOTIC EUKARYOTIC Present as a Present in some GLYCOCALYX capsule or slime cells that lack layer cell wall

CELL WALL Usually present When present, chemically simple No CHO & Sterols & CHO PLASMA MEMBRANE generally lacks that serve as sterols receptors PRINCIPAL DIFFERENCES BETWEEN PROKARYOTIC & EUKARYOTIC CELLS CHARACTERISTIC PROKARYOTIC EUKARYOTIC Presence of Cytoskeleton or CYTOPLASM actin cytoplasmic cytoskeleton in streaming some Large size (80S); Smaller RIBOSOMES Small size (70S) size (70S) in organelles Single circular Multiple linear DNA chromosomes; chromosomes lacks histones with histones PRINCIPAL DIFFERENCES BETWEEN PROCARYOTIC & EUCARYOTIC CELLS CHARACTERISTIC PROKARYOTIC EUKARYOTIC

CELL DIVISION Binary fission Mitosis

SEXUAL No meiosis; REPRODUCTION transfer of DNA Involves fragments only Meiosis