Lecture 2: Intro to Eukaryotes

Domain of Life - Eukarya

Branched off from Archaea, uni and multicellular organisms, and less than prokaryotes but have larger size

Eukaryotes Characteristics

Highly diverse: Structurally & functionally complex, larger size and genome, nucleus w. membrane, and membrane bound organelles

Endosymbiosis

How eukaryotes evolved from archaea from engulfing bacteria

Endosymbiosis evidence

Similar size, 70s ribosomes, small circular dna genome, phospholipid bilayer, and ability to replicate by binary fission

Mitochondria origin

an engulfed nonphotosynthetic bacteria

Chloroplast origin

an engulfed photosynthetic bacteria

Eukaryote Kingdoms: 4 branches

Fungi, plant, protists, and animals

Phylogenetic tree

Non-membrane Enclosed Structures

Ribosomes and cytoskeleton

80S ribosomes found 

cytoplasm and rough ER

70S ribosomes found 

mitochondria and chloroplasts

Membrane-bound Organelles

Nucleus, endomembrane system (ER, golgi apparatus, vesicles and vacuoles), and mitochrondria

Nucleus

Houses DNA genome within nucleoplasm with multiple linear chromosomes and chromatin (histone)

Nucleolus 

dense region of rRNA biosynthesis; ribosome assembly begins that’s enclosed in nuclear envelope that contains nuclear pores to control traffic of materials

Mitosis – Asexual replication

1 parent cell divides into 2 genetically identical daughter cell clones → 1 division

Meiosis - Sexual reproduction

2 cell division stages, 1 parent cell produces 4 genetically distinct haploid gametes (homologous)

Endomembrane System - EMS

Cell size is big so it needs a cellular transport system of membranous tubules, sacs, and flattened disks (cisternae), and organelles and connections b/t them

Endoplasmic Reticulum (ER)

Interconnected array of cisternae and tubules originated from nuclear envelope, and can be rough or smooth ER

Cisternae

flattened, membrane-bound sacs that are used in golgi apparatus and rough ER

Rough ER - Cisternae 

Contains ribosomes that buds off in vesicles transported to golgi apparatus for further processing to membrane, another organelle, or out of cell

Smooth ER - Tubules

No ribosomes and involved in biosynthesis of lipids, carbohydrates metabolism, and detoxification of toxic compounds

Golgi apparatus

Arrays of cisternae that contains modified lipids and proteins of transported from the ER

Golgi apparatus: enzymes

Produces glycolipids, glycoproteins, or proteoglycans

Golgi apparatus: Sorts and distributes

Transport vesicles containing products pinch off and move to and fuse with cell/organelle membranes

Golgi apparatus: Cell surface significance

Distinguishes types of cell types, role in cell recognition, and serves as cell surface receptors

Vesicles

Small fluid filled lipid bilayer enclosed sacs needed for cell survival for transport, secretion, digest, and sequester materials

Vesicles functions

Transports materials within cells ‘shipping containers’

Secretory- stores and traffic to cell surface for exocytosis

Vacuoles

Larger than vesicles and are often used for storage

Degradative Vesicles

cellular compartments that break down waste and damaged components

Lysosomes and Peroxisomes

Lysosomes

Cellular garbage disposals b/c its a digestive enzymes that breaks down particles and is compartmentalized

Peroxisomes

Oxidative degradation by enzymatically degrading fats, amino acids, toxins by metabolizing oxygen containing waste

Protects cells from toxic oxygen intermediates

Mitochondria Charcteristics

Double membrane, 70s ribosomes, circular chromosomes from endosymbiosis

Mitochondria Function

Generates energy for cell by producing ATP, amino acids, vitamins and carrying out apoptosis

External Eukaryotic Cell Structures

Plasma membrane, glycocalyx, cell wall, ECM, flagella, and cilia 

Plasma membrane

Phospholipids bilayer cell membrane, peripheral and integral proteins, fluid mosaic, selective, and contains sterols

Membrane Transport Mechanisms

Simple diffusion, facilitated diffusion, and active transport

Unique to eukarya – endocytosis and exocytosis

Glycocalyx

Sticky, polysaccharide gel coating extracellular surface of the PM

Role in protections, interactions, adhesion, and association  with other macromolecules

Extracellular Matrix (ECM)

Helps maintain shape, provide structural stability, transmits signals and produced animal and some protist cells (cells lacking cell walls)

Extracellular Matrix (ECM): Secretions

Secretes mass of carbohydrates and proteins

Proteoglycans form bulky mass of ECM, collages, and fibronectin

Cell wall found

only in eukaryotes that lack ECM which is fungi and some protists

Cell wall function

Rigid, structural layer that helps maintain cell shape and protects against desiccation, mechanical and osmotic stress

Cell wall compositions

Fungi – chitin, glucans, &/or proteins 

Protists – cellulose or glycoproteins

Motile structures: Cilia and Flagella

Membrane covered hairlike structures projecting out from cell surface composed of microtubules and connected to body

Flagella

Less numerous and longer tail-like

Cilia

Numerous, shorter and coordinated movement

Parasites

organism that lives on or in a host organism and obtains food from or at the expense of its host

3 Main classes associated with human disease

3 Main classes of parasites

Protozoa (unicellular), helminths, and ectoparasites

Protozoa and helminths are endoparasites

Protista

Highly diverse group of eukaryotes

Pathogenic protists → Parasitic protozoans “first animals” (no cell wall)

Parasitic protozoans

Many have 2-phase life cycles, alternating between proliferative stages (e.g., trophozoites) and resting cysts (survive harsh conditions)

-Portion of life cycle occurs w/in host

Parasitic protozoans Categorized

based on motility and morphology into 4 types:

Amoeboid, flagellated, ciliated, and sporozoans/apicomplexans

Animalia Endoparasites: Helminths

Microscopic aspects of life cycle → identified by microscopic eggs and larvae

287 species of multicellular parasites can infect and live within human body

Helminths 2 main categories

Flatworms and roundworms

Animals ectoparasites

Some pathogenic microbes require arthropod vectors for part of life cycle, biting insects are important vectors as most feed on blood

Animals ectoparasites: Mosquitos

Causes malaria

Animals ectoparasites: Ticks

Causes lyme disease and Rocky Mt Spotted fever

Animals ectoparasites: Fleas

Causes plague and typhus

Mycology

the study of fungi

Fungi: Cell wall

Contains chitin and cell membrane contains ergosterols

Fungi: Growth

Typically grow slower than bacteria and at lower temperature & pH

Fungi: Reproduction

Unique and complex lifecycles involving asexual and sexual reproduction

Fungi: Life forms

Grow as yeast (microscopic) or mold (macroscopic) or both (dimorphic)

Multicellular Fungal characteristics: Mold

Multicellular form with tubular filaments termed hyphae

Septate hyphae, nonseptate hyphae, and mycelia

Septate hyphae

walls between the cells

Nonseptate hyphae

lack separation between the cells

Mycelia

macroscopically visible intertwined mass of hyphae (fuzzy appearance)

Fungal characteristics: Reproduction

Reproduce by producing large numbers of spores, it is asexual (by mitosis) or sexual (by meiosis); many species can produce both types

Unicellular Fungal characteristics: Yeast

5-10x larger than bacteria and daughter cells that remain attached to parent for pseudohyphae

Yeast Reproduction

Reproduce asexually by budding off daughter cells; sexually by meiosis

Yeast: Dimorphic

change between yeast and mold forms in response to environmental changes (nutrient availability or fluctuations in temperature

Mold = cold, yeast =heat

Mycoses

Diseases caused by fungal infection

Few are serious pathogens – human body temperature a major deterrent

Superficial mycoses

infect skin & nails (tinea), mouth & vagina (candida)

Invasive, systemic mycoses

Widespread, involve internal organs, lethal 

True pathogens and Opportunistic pathogens