Exam 1: Ch 4: Eukaryotes

Question 1

Nucleus

Answer 1

separated from cytoplasm by the nuclear envelope
− Composed of 2 membranes
− Perforated w/small regularly spaced pores
− Nucleolus – found in nucleoplasm; site of RNA synthesis; collection area for ribosomal subunits

Question 2

Cytoplasmic membrane

Answer 2

Cytoplasmic membrane – typical bilayer of phospholipids in which protein molecules are embedded; serves as selectively permeable barrier

Question 3

Cell wall

Answer 3

animals (including helminthes) and protozoa DO NOT have cell walls; fungi do
− Cell walls of fungi:
o Rigid and provide structural support and shape
o Different in chemical composition from prokaryotic cell walls
o Made of: chitin, glycoprotein, mixed glycans

Question 4

Endoplasmic reticulum

Answer 4

series of microscopic tunnels; used in transport, protein folding, and protein & lipid synthesis (occurs in other sites too)
− RER – ribosomes are attached to its membrane surface
− SER – w/out ribosomes

Question 5

Golgi apparatus

Answer 5

site of protein modification and shipping

Question 6

Ribosomes

Answer 6

staging areas for protein synthesis
− Size and structure:
o Large and small subunits of ribonucleoprotein
o Eukaryotic ribosome is 80S (a combo of 60S and 40S subunits)

Question 7

Cytoskeleton

Answer 7

flexible framework of molecules criss-crossing the cytoplasm

− Functions: anchoring organelles, moving RNA and vesicles, permitting shape changes, movement

Question 8

Vesicles

Answer 8

lysosomes and vacuoles

Question 9

Lysosomes

Answer 9

participate in the removal of cell debris and damaged tissue
o Contain a variety of enzymes involved in the intracellular digestion of food particles and protection against invading microorganisms

Question 10

Vacuoles

Answer 10

membrane bound sacs; contain fluids or solid particles to be digested, excreted or stored
o Formed in phagocytic cells in response to food and other substances that have been engulfed

Question 11

Mitochondria

Answer 11

generate energy for the cell
− Composed of smooth continuous outer membrane
− Inner membrane: has tubular inner folds called cristae
− Unique organelles:
o Divide independently of the cell
o Contain circular strands of DNA
o Have prokaryotic-sized 70S ribosomes

Question 12

Cristae (in mitochondria)

Answer 12

In inner membrane
o Holds the enzymes and electron carriers of aerobic respiration
o Extracts chemical energy contained in nutrient molecules and makes ATP

Question 13

Appendages for moving

Answer 13

flagella and cilia

− Locomotion via cilia and flagella is common in protozoa, many algae, and a few fungal and animal cells

Question 14

Flagella

Answer 14

microtubules slide past each other creating a whipping motion that requires the expenditure of energy
o Motility: allows microorganisms to move toward nutrients and positive stimuli, and away from harmful substances and stimuli
o Types of eukaryotes these are found on: protozoa, many algae, and few fungal and animal cells

Question 15

Cili

Answer 15

similar structure to flagella but are shorter and more numerous
o Occur all over the cell surface in rows; beat back and forth in “oarlike strokes”
o Found only on a single group of protozoa & in certain animal cells

Question 16

Glycocalyx

Answer 16

outermost layer that comes into direct contact w/environment
− Usually composed of polysaccharides
− Appears as a network of fibers, a slime layer, or a capsule
− Functions: protection, adherence of cells to surfaces, reception of signals from other cells and the environment

Question 17

The cell’s (nature’s) assembly line

Answer 17

the nucleus, ER and golgi
1. A segment of genetic code of DNA from nucleus is copied onto RNA → passed thru the nuclear pores to the RER
2. Synthesized proteins on RER are deposited into lumen → transported to golgi apparatus
3. Proteins in the golgi are chemically modified and packaged into vesicles to be used by the cell
− Book version:
o Nucleus governs/regulates all activities – directs these activities thru a structural and chemical network
Segment of DNA w/instructions for producing proteins → copied onto RNA → passed out thru nuclear pores directly to ribosomes on ER → specific proteins synthesized from the code → deposited in lumen of ER → transported to GA → chemically modified and packaged into vesicles to be used by cell in a variety of ways

Question 18

Last common ancestor

Answer 18

neither prokaryotic or eukaryotic; both prokaryotes and eukaryotes evolved from this precursor cell
History:
− The first primitive eukaryotes were probably single celled and independent
− Later, cells began to aggregate and form colonies
− Cells became specialized within colonies
− Later, complex organisms evolved and individual cells lost the ability to survive on their own
~ only disease-causing eukaryotes will be discussed in this lecture: protozoa, fungi, helminths

Question 19

Endosymbiosis

Answer 19

the more complex cell type most likely emerged when a LCA cell engulfed smaller prokaryotic cells and coexisted w/them

− Process:

1. Larger cell engulfs the smaller one → smaller one survives and begins an endosymbiotic association
2. Smaller prokaryote becomes established in its host’s cytoplasm and multiplies → can utilize aerobic metabolism and increase energy availability for the host
3. Ancestral eukaryotic cell develops extensive membrane pouches → they become the ER and nuclear envelope
4. Photosynthetic bacteria are also engulfed → they develop into chloroplasts
5. The first eukaryotic cells have emerged

Question 20

Evidence of endosymbiosis

Answer 20

Mitochondria:
o Are same size as bacteria
o Have one circular chromosome, just like bacteria
o Have 70S ribosomes just like bacteria
o Divide via binary fission like bacteria

Question 21

Eukarya that cause disease

Answer 21

fungi, protozoa, helminths

Question 22

Fungi

Answer 22

fungus penetrates the substrate and secretes enzymes that reduce it to small molecules that can be absorbed by cells
− Not photosynthetic
− Can utilize a large variety of nutrients
− Macroscopic fungi: mushrooms, puffballs, gill fungi
− Microscopic fungi: molds, yeasts
− Forms:
- unicellular - colonial - complex/multicellular (mushrooms, puffballs)

Yeasts, hyphae, molds

Question 23

Yeasts

Answer 23

round to oval shape; asexual reproduction; budding; single cell

Question 24

Hyphae

Answer 24

long threadlike cells found in bodies of filamentous fungi

Question 25

Pseudohypha

Answer 25

chain of yeast cells

Question 26

Morphology: Fungi

Answer 26

o Cells of microscopic fungi grow in loose associations or colonies
o Colonies of yeasts are much like bacteria (have soft uniform texture and appearance)
o Colonies of filamentous fungi have cottony, hairy or velvety texture
o Mycelium – the woven, intertwining mass of hyphae that makes up the body or colony of a mold
o Septa – segments/cross walls found in most fungi; allow the flow of organelles and nutrients btwn adjacent compartments
o Non-septa hyphae – consist of one, long, continuous cell
o Vegetative hyphae – responsible for the visible mass of growth

Question 27

Reproductive strategies & spore formation: Fungi

Answer 27

reproductive/fertile hyphae produce spores
o Spores: responsible for reproduction; explicitly responsible for multiplication; help fungus gain genetic variation and to be disseminated into environment
• Can be dispersed thru the environment by air, water and living things
• Will germinate upon finding a favorable substrate → produce new fungus colony in short time

Question 28

Spores

Answer 28

responsible for reproduction; explicitly responsible for multiplication; help fungus gain genetic variation and to be disseminated into environment

Question 29

Protozoa

Answer 29

most are harmless, free-living inhabitants of water and soil; a few species are responsible for hundreds of millions of infections each year; classified together b/c of their similar characteristics instead of their genetic relatedness

“first animals”
single celled organisms

Question 30

Nutrition & habitat range: Protozoa

Answer 30

o Parasites live on fluids of their host
o Main limiting factor for growth = availability of moisture (predominant habitats are fresh and marine water, soil, plants, and animals)
o Many protozoa can convert to resistant, dormant stage called a cyst

Question 31

Life cycle & reproduction: Protozoa

Answer 31

o Trophozoite – motile feeding stage requiring ample food and moisture to stay active
o 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
o Life cycle determines mode of transmission!
• Trichomonas vaginalis: STD, doesn’t form cysts so must be transmitted by intimate contact
• Entamoeba histolytica and Giardia lamblia: form cysts so are readily transmitted via contaminated water and food
o All protozoa reproduce by simple, asexual mitotic cell division
o Sexual reproduction occurs in most protozoa → results in new and different genetic combinations

Question 32

Trophozoite

Answer 32

motile feeding stage requiring ample food and moisture to stay active

Question 33

Cyst

Answer 33

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

Question 34

Helminths

Answer 34

include tapeworms, flukes and roundworms
− Adult specimens usually large enough to been seen w/naked eye
− Not all flatworms and roundworms are parasite – many live free in soil and water
− Most parasitic helminths spend part of their live in GI tract

Question 35

Flatworms

Answer 35

have thin, often segmented body plan; divided into tapeworms and flukes

Question 36

Roundworms

Answer 36

AKA: nematodes

elongated cylindrical unsegmented body

Question 37

General worm morphology

Answer 37

multicellular animals; equipped w/organs and organ systems
o Most developed organs: reproductive tract
o Reduction in digestive, excretory, nervous and muscular systems

Question 38

Life cycles and reproduction: Helminths

Answer 38

complete life cycle includes fertilized egg, larval, and adult stages
• Must transmit an infective form (egg or larva) to body of a host
• Intermediate host – the host in which the larva develops
• Definitive host – the host in which adulthood or mating occur
• Transport host – an intermediate host that experiences no parasitic development but is an essential link in the completion of the cycle
o Fertilized eggs: released to environment; provided w/protective shell and extra food to aid development into larva; vulnerable to heat, cold, drying, predators
o Certain helminthes can lay 200,000-25 million eggs/day to ensure completion of their life cycle

Question 39

Sources for human infection: Helminths

Answer 39

contaminated food, water, soil, or infected animals

Question 40

Route of infection: Helminths

Answer 40

oral intake or penetration of unbroken skin

Question 41

Distribution and importance of parasitic worms

Answer 41

o ~ 50 species of helminthes parasitize humans
o Distributed in all areas of the world (higher incidence in tropical areas)
o Yearly estimate of cases: in the billions, not confined to developing countries
o North American estimate: >50 million helminth infections