Eukaryotic Cells

Archaea extra info

• very little is knob about archaea because many of them are extremophiles

• distinct domain of life (look like bacteria but genetically like us)

• Dr. Carl Woesse studied 16S RNA and discovered the domain archaea

• Asgard group = considered the closest known microorganisms to eukaryotes, suggesting they may hold key clues to understanding the evolution of complex life from simpler organisms

The first eukaryotic cells appeared _______.

1.8 billion years ago

• Bacteria, Archaea, and Eukarya all evolved from the Last Universal Common Ancestor (LUCA)

The last common ancestor of all eukaryotic cells was a single-celled microorganism closely related to _______.

archaea

Microbial members of domain Eukarya are much more genetically and ecologically diverse than ________.

larger eukaryotes (humans and animals)

Eukarya exhibit tremendous morphological and ecological complexity but a ________.

limited range of metabolic diversity

Many organelles are enclosed separately by their own _________.

lipid membranes

Mitochondria and chloroplasts originated from _______.

endosymbiosis

• this theory is widely accepted

The proposed ancestors of mitochondria were _______.

oxygen-using non-photosynthetic prokaryotes

• an ancient prokaryote absorbed a respiring bacteria which eventually becomes the mitochondria

The proposed ancestors of chloroplasts were _________.

photosynthetic prokaryotes

• an ancient prokaryotic cells absorbs a respiring bacteria (becomes mitochondria) and a bacteria capable of photosynthesis (becomes chloroplasts)

Mitochondria and chloroplasts display the following similarities with bacteria that led to the endosymbiont theory

1. Capable of independent division
2. Contains a circular chromosome with bacterial
DNA sequences
3. Prokaryotic-sized ribosomes
4. Enveloped by a double membrane
• Bacterial-like membranes and can be inhibited by drugs that affect only bacteria

Prokaryotes have circular DNA while eukaryotes have ________.

linear DNA

Endosymbiotic Theory

• WELL SUPPORTED among scientific circles

• Bacteriologists have placed both mitochondria and chloroplasts on a family tree of bacteria

• Mitochondria’s closest bacterial relative
  are rickettsias
  • An intracellular bacteria

Mitochondria

• sites of cellular respiration, a metabolic process that uses oxygen to generate ATP

• powerhouse of the cell

• have a double membrane

Chloroplasts

found in plants and algae, are the sites of photosynthesis

Mitochondria

• Double membrane: a smooth, continuous
  outer membrane with an inner folded
  membrane

• Cells that are metabolically active have a lot of these (e.g. liver, muscle, sperm cells)

  1. Generate energy (ATP) for the cell

  2. Divide independently of the cell

  3. Contain circular strands of DNA and prokaryotic ribosomes

Chloroplasts

• the site of photosynthesis, where light energy is converted into chemical energy of food molecules.

• Found in algae and plant cells

• Capable of converting energy from sunlight into chemical energy through photosynthesis

• Produce oxygen gas as a by-product of photosynthesis

• Resemble mitochondria but are larger, contain special pigments, and are more varied in shape

Nucleus

• the main genetic control center in eukaryotic cells

• Contains 1 or more chromosomes

• Separated from the cytoplasm by a
  nuclear envelope which has Nuclear pores that allow certain materials to pass between the nucleus and the cytoplasm

Nucleolus

where components of ribosomes are made; within the nucleus of a eukaryotic cell

Ribosomes

• NOT membrane bound

• Free ribosomes (cytosol) and bound ribosomes (rough endoplasmic
  reticulum or nuclear envelope)

• Cells that have high rates of protein synthesis have particularly large
  numbers of these (e.g. human pancreas)

• function: protein synthesis

Both prokaryotic and eukaryotic cells have ribosomes, but _______.

the structures differ slightly.

• eukaryotic ribosomes being significantly larger (80S) compared to prokaryotic ribosomes (70S)

Endomembrane system

• Manufacturing and distributing cellular
  products

• Regulates Protein Traffic and
  Performs Metabolic Function

  
  

Components of the endomembrane system

1. Nuclear envelope
2. Endoplasmic reticulum
3. Golgi apparatus
4. Lysosomes
5. Vacuoles
6. Plasma membrane

• These components are either continuous or connected through transfer by vesicles

Endomembrane System process

1. nuclear envelope is connected to RER which is also continuous with SER

2. membranes and proteins produced by the ER move via transport vesicles to the golgi

3. the golgi pinches off transport vesicles and other vesicles that give rise to lysosomes, other types of specialized vesicles, and vacuoles

4. the lysosome is available for fusion with another vesicle for digestion’

5. a transport vesicle carries proteins to the plasma membrane for secretion

6. the plasma membrane expands by fusion of vesicles; proteins are secreted from the cell by exocytosis

Smooth Endoplasmic Reticulum

• ER without ribosomes attached

• Synthesizes lipids
  • Oils, steroids, and
  phospholipids
  • Steroids include sex
  hormones of vertebrates
  and steroids secreted by
  the adrenal glands

• Detoxifies drugs and poisons

• elevated amounts in liver cells

Rough Endoplasmic Reticulum

• ER with ribosomes
  attached

• Attached ribosomes make
  membrane proteins and
  secretory protein.

• Secretory proteins depart
  from the ER wrapped in
  transport vesicles

• modifies proteins for
  shipment

Golgi Apparatus

• Receives, refines, stores, and
  distributes chemical products of
  the cell

• Modifies products of the ER

• Manufactures certain
  macromolecules

• Sorts and packages materials
  into transport vesicles

Lysosome

• cell’s garbage disposal

• A membranous sac of hydrolytic enzymes that can digest (hydrolyze) macromolecules

• work best in acidic environments

• digest our own organelles to make new components (autophagy)

Autophagy

Lysosomes use enzymes to recycle the cell’s own organelles and macromolecules

Vacuole

• Membrane-bound sacs containing fluids or solid particles to be digested, excreted, or stored

  
  

Cytoplasm

everything inside the plasma membrane and
external to the nucleus
• the substance in which various cellular components are found

Cytoskeleton

a network of fibers extending throughout the cytoplasm
• It gives animal cells shape and support
• Controls intracellular traffic
• It gives cells some ability to control their movement

Eukaryotic Cilia

• Similar to flagella in structure,
  but are smaller and more numerous

• similar to bacterial fimbrae

Eukaryotic Flagella

• X10 thicker than bacterial
  flagella

• Moves in a wave-like manner
  instead of rotating

• less complex than bacterial flagella

Plasma (Cytoplasmic) Membrane

• Selectively permeable membrane enclosing the cytoplasm of a cell
  • The boundary that separates the cell from its surroundings
  • Regulates the traffic of chemicals into and out of the cell

• Structure: Fluid mosaic model
  • phospholipid bilayer & membranous proteins

Glycocalyx

a layer of material containing substantial amounts of sticky carbohydrates

• An outermost layer covering the plasma membrane that comes into direct contact with the environment

• strengthens the cell surface, helps attach cells together, and may contribute to cell–cell recognition

• can appear as a network of fibers, slime layer, or a capsule

Protozoa, helminths, animals, and some algae do not have _______.

cell walls

Cell walls of fungi and most algae ________.

• Rigid and provide structural support and shape

• Different in chemical composition from bacterial and archaeal cell walls

Fungi

Thick inner layer of polysaccharide fibers composed of chitin or cellulose.

• Thin outer layer of mixed glycans

Algae

Varied in chemical composition: various sugars along with minerals such as silicon dioxide and calcium carbonate

Cell membrane

• Typical bilayer of phospholipids in which protein molecules are embedded

• Contain sterols of various kinds which provide stability

  
  

Cytoplasmic membranes of eukaryotes have a
similar function as those in bacteria and archaea,
serving as ________.

selectively permeable barriers in transportation

Microbial eukaryotes can be defined by their
morphology as _______.

protists, algae, or fungi

Protist

an informal term referring to any
eukaryotic microorganism that is not a plant,
animal, or fungus

Algae

include unicellular and multicellular
eukaryotes that perform photosynthesis but
are not plants

Fungi

nonphototrophic eukaryotic microorganisms with rigid cell walls composed of chitin

Fungal cells

• Cell walls - - - > Chitin
  • Cell membranes - - - > Sterols (ergosterol) = Target in anti-fungal drugs

• Two basic morphological types:
  • Hyphae
  • Yeasts

Yeasts

• Round to oval shape

• Asexual reproduction, budding

Hyphae

• Long, threadlike cells found in the bodies of filamentous fungi
  (molds)

Pseudohypha

chain of yeast cells

Some fungal cells are considered dimorphic and can take _________.

either growth form (yeast or hyphae), depending on growth conditions - - - > particularly characteristic of some pathogenic molds

Fungal Nutrition

fungi can be Heterotrophic, saprobic, or parasitic

• can penetrate the substrate and secrete enzymes that reduces it to small molecules that can be absorbed by the cells

heterotrophic

fungi acquire nutrients from a wide variety of organic substrates

Saprobic

these substrates from the remnants of dead plants and animals in soil or aquatic
habitats

Parasitic

grow on the bodies of current or previously living animals or plants, although very few require a living host

Fungi are often found in ________.

nutritionally poor or adverse environments, and those with high salt or sugar content

Benefits of Fungi

• Play an essential role in decomposing organic matter and returning minerals to the soil

• Form stable associations with plant roots and increase their ability to absorb water and nutrients

• Fungi have been engineered to produce large quantities of antibiotics, alcohol, organic acids, and vitamins

• Some fungi are eaten or used to provide flavoring to food

Morphology of Fungi

• Cells of most microscopic fungi grow
  in loose associations or colonies

• Colonies of yeasts are much like
  bacteria: they have a soft, uniform
  texture and appearance

• Colonies of filamentous fungi are
  noted for the striking cottony, hairy,
  or velvety texture

Fungi can propagate by the outward growth of ________.

existing hyphae or by fragmentation

Spores

• Primary reproductive mode of fungi

• Can be dispersed through the environment by air, water, and living things

• Will germinate upon finding a favorable substrate and produce a new fungus
  colony in a short time

Asexual spores

• formed by the hyphae of one
  organism

• When these spores germinate, they become organisms that are genetically identical to the parent

• types: Sporangiospores and Conidiospores/conidia

Sporangiospores

formed by successive cleavages
within a saclike head called a sporangium, which is attached to a stalk, the sporangiophore

Conidiospores or conidia

free spores not enclosed by a spore-bearing sac

Sexual spores result from the fusion of nuclei from _______.

two opposite mating strains (plus and minus
strains) of the same species of fungus.

Sexual spores require two different mating strains and so are made ______.

less frequently than asexual spores. Organisms that grow from sexual spores will have genetic characteristics of both parental strains

• Variations lead to potentially advantageous adaptations

Algae

• A group of photosynthetic organisms most readily recognized by their larger members, such as seaweeds and kelps

• Widespread in both fresh and marine waters

• Provide basis of food web in most aquatic habitats

• Contribute significantly to oxygen content of the atmosphere through photosynthesis

Algae (cont.)

• Unicellular, colonial, and filamentous
  forms

• Larger forms can possess tissues
  and simple organs

• Exhibits most organelles - - - >
  including chloroplasts

Diatoms

• One of the most prevalent groups on Earth

• Cell wall contains silica
  • High diversity is useful in forensics in analyses of bodies of water

Diatoms and forensics

• breathing when entering the water = diatoms in lungs and peripheral organs

• died before entering the water = diatoms only in lungs

Forensic Limnology

the study of freshwater ecology for the presence of diatoms (particularly) in order to solve forensic and medical cases

Diatoms are among the most important and _________.

prolific microscopic sea organisms and serve directly or indirectly as food for many animals.

• Structural Materials: such as heat and fire-resistant products, sound proofing materials, polishes such as, porcelain, drainpipes, tiles, non-conducting materials and artificial stone

• Cosmetic products: soaps, deodorants, toothpaste

• Used as an insecticide (Diatomaceous Earth)

• As a base in dynamite

Protozoa

• Name comes from the Greek for “first animals”

• About 12,000 species of single-celled creatures

• Widely distributed in nature, exhibit wide
  range of morphologies

• Most are harmless, free-living inhabitants of water and soil

• A few species are pathogens responsible for hundreds of millions of infections each year

Protzoan form and function

• Single cells containing all of the major eukaryotic organelles

• Cytoplasm divided into two parts:
  1. Ectoplasm

  2. endoplasm

Ectoplasm

clear outer layer involved in locomotion, feeding,
and protection; present in protzoa

Endoplasm

granular inner region housing the nucleus,
mitochondria, and food and contractile vacuoles; present in protozoa

Protozoan form and function

• Some organelles act as a primitive nervous system to coordinate movement

• Can move through fluids by means of pseudopods (“false feet”)

• Cell membrane regulates food, wastes, and secretions

• Cell shape can remain constant (as in most ciliates), or change constantly (as in amoebas)

Nutritional requirements of Protozoa

• Heterotrophic, require food in a complex organic form

• Free-living species scavenge dead plant or animal debris or graze on bacteria and algae

• Some have special feeding structures, such as oral grooves
  • Some absorb food directly through the cell membrane
  • In all protozoa, digestion takes place in membrane-enclosed vacuoles

Habitat range of habitats

• Pathogenic species may live on the fluids of their host, such as plasma and digestive juices, or actively feed on tissues

• Main limiting factor is availability of moisture

• Predominant habitats are fresh and marine water, soil, plants, and animals

• Can survive in extremes of temperature and pH

Many protozoans alternate between the ______.

trophozoite and cyst stage, depending on the habitat

• Some protozoan groups exist only in the
  trophozoite phase

Trophozoite

motile feeding stage of protozoa requiring
ample food and moisture to stay active

Cyst

• Dormant, resting stage when conditions in the environment become unfavorable

• Resistant to heat, drying, and chemicals

• can be dispersed by air currents

• Important factor in the spread of disease

Stages of protozoa lift cycle

• trophozoite (active feeding stage)

• cell rounds up, losing motility

• drying and lack of nutrients = early cyst wall formation

• mature cyst (dormant resting stage)

• moisture and nutrients restored = cyst wall breaks open

All protozoa reproduce by _________.

relatively simple, asexual mitotic cell division
or multiple fission

Sexual reproduction in protozoa

• occurs in most protozoa

• Ciliates participate in conjugation in
  which two cells fuse and exchange
  micronuclei

• Results in new and different genetic
  combinations - - - > can be advantageous
  in evolution

Helminths

• Include tapeworms (Cestodes), flukes (Trematodes), and roundworms (Nematodes)

• Adult specimens are usually large enough to be seen with the naked eye
  • May need a microscope for eggs/larvae

• Not all flatworms and roundworms are parasites; many live free in soil and water
  • ~50 species cause disease in humans

• Disease-causing helminths spend part of their lives in the gastrointestinal tract

Flatworms

• Very thin, often segmented body
  plan

• Divided into tapeworms and flukes

Roundworms

Elongated, cylindrical, unsegmented body

General Worm Morphology

• Multicellular animals that are equipped to some degree with organs
  and organ systems
  • In pathogenic helminths, the most developed organ system is the
  reproductive tract

• Therefore, there is a reduction in the digestive, excretory, nervous,
  and muscular systems

Life Cycles and Reproduction of helminths

• Complete life cycle includes the fertilized egg, larval, and adult stages

• Adults derive nutrients and reproduce sexually in a host’s body

• can be separate sexes (visually similar or distinct) or
  hermaphroditic

Life cycle of helminths

• Must transmit an infective form (egg or larva) to the body of another host

• The host in which the larva develops is known as the intermediate (secondary) host

• Adulthood and mating occur in the definitive (final) host

• Transport host is an intermediate that experiences no parasitic development

Sources for human infection with helminths are contaminated ______.

food, soil, and water or infected animals

Fertilized eggs of helminths

• Released to the environment

• Provided with a protective shell and extra
  food to aid their development into larvae

• Vulnerable to heat, cold, drying, and
  predators

Certain helminths can lay from ______.

200,000 to 25 million eggs a day to assure successful completion of their life cycle