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L04: Eukaryotes

BIOL 153/LBlack Hills State Univ.Ramseys See 'Tree of Life' Lecture

Three Domainsof Life

I. Prokaryotic vs. eukaryotic cells Prokaryotes EukaryotesDNA X XNucleus XMitosis & meiosis XRibosomes X XMembrane-bound organelles XCell wall X Many (not animals)

Multicellularity Often

II. Eukaryotic 'Plant' vs Animal cells

for this lecture:

'plant' => land plants + algae

land plantsgreen algaered algae

brown algaegolden algaediatoms

See 'Tree of Life' Lecture

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'Plant' cells Animal cells

Cell wall X

Cell type diversity Less More

Mitochondria X X

Chloroplasts X

Vacuoles Always(large vacuoles)

Often(small vacuoles)

III. Eukaryotic cell components

A. Nucleus

membrane-bound compartment containing linear DNA (chromosomes)

nucleus disassociates during mitosis and meiosis

B. Cytoplasm

living matter of cell, outside nucleus

cytosol is term for the cytoplasm 'goo'

nucleus

cytosol

cell membrane C. Organelles

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1. Definition of organelle

• Narrow: membrane-bound structure in cytoplasm

• Broad: any cell structure outside nucleus

2. Membrane-bound organelles (examples)

a. Mitochondria

2x membrane-bound organelle; performs aerobic respiration

b. Chloroplast

2x membrane-bound organelle; performs photosynthesis

c. Vacuole

membrane-bound space with water, organic + inorganic molecules, enzymes

functions in storage, materials isolation, turgor pressure

d. Eyespot apparatus

membrane-bound organelle;senses light direction + intensity

found in many unicellular photosynthetic organisms

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nucleus

cytosolmitochondria

chloroplast

cell membrane

vacuole

3. Non-bound organelles (examples)

a. Ribosome

small structure composed of protein + RNA

site of protein synthesis in cell cytoplasm

b. Flagella

threadlike structure protruding from cell;function in movement

found in many unicellular photosynthetic organisms, sperm of many multicellular photosynthetic organisms

D. Cytoskeleton

network of microtubules + actin filaments in cytosol

in-cell movement (cell division, cytoplasmic streaming, etc.)

E. Cell wall

structural layer outside cell membrane; provides support + protection

complex composition usually including carbohydrate polymers and microfibril structures

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eukaryotes very traditionally called 'plants'(prokaryote cell walls different)

1. Taxonomic distribution

land plants, algae, fungi, many protists

2. Land Plant cell walls

a. Multiple layers

• 1º cell wall: flexible, exterior

• 2º cell wall: rigid, interior (not always present)

• middle lamella: interface between cells

b. Composition

• 1º cell wall: cellulose, hemicellulose, pectin

• 2º cell wall: lignin, cutin, suberin

c. Plasmodesmata

small channels traversing cells walls

allow regulated communication + transport among cells

intercellular space

plasmodesmata

nucleus

cytosolmitochondria

chloroplast

cell wall

cell membrane

middle lamella

vacuole

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3. Other cell walls • Fungi: chitin

carbohydrate that provides rigidity to fungal cell walls

• Fungi: chitin • Diatoms: silica (glass)

SiO2 provides strength and ridigity to cell wall

• Diatoms: silica (glass) • Brown algae: alginate

reacts with calcium in ocean water, creates flexible gel

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• Brown algae: alginate

reacts with calcium in ocean water, creates flexible gel

• Red algae: carageenan, agar, calcium carbonate

provide flexibility (carageenan, agar), rigidity (calcium c.)