1 cells bs122 principles of biology ii daniel w. ward

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Cells

BS122 Principles of Biology II

Daniel W. Ward

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The Cell Theory

Major Components– all living things are composed of cells– the cell is the structural and functional unit of

life– cells come from pre-existing cells– human disease often reflects abnormality at the

cellular level

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The Cell Theory

Origins– the first two components were put forward by

the German biologists Matthias Schleiden and Theodor Schwann in 1839

– the last two components were put forward by Rudolph Virchow, another German, around 1850

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Cellular Characteristics

Prokaryotic Cells– General Definition

• single celled

• structurally simple

• lack organelles

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Prokaryotic Cells– Structures

• Cell Wall

• Plasmalemma / Cell Membrane

• Flagella

• Deoxyribose Nucleic Acid (DNA)

• Nucleoid

• Ribosome

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• Cell Wall– surrounds the cell

– rigid

– composed of peptidoglycans (peptide sugars)

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• Plasmalemma / Cell Membrane– located beneath the cell wall

– contains enzymes which speed up certain chemical reactions

– may contain invaginations where cell division might occur

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• Flagella– tail-like appendage

– found in some prokaryotes

– anchored to the cell wall and the cell membrane

– functions in locomotion

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• Deoxyribose Nucleic Acid (DNA)– genetic material of the cell

– arranges in a single circle

– “naked” because it is not complexed with proteins or surrounded by a membrane

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• Nucleoid– nucleus-like structure

– contains the DNA

– may appear fibrous when viewed under the microscope

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• Ribosomes– composed of RNA and protein

– allows a cell to utilze DNA to manufacture proteins

» this process is fast in prokaryotes due to the proximity of the DNA, RNA, and ribosomes

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Prokaryotic Cells– Generalized

Structure

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Prokaryotic Cells– while simple, prokaryotes compose the majority

of living cells on the planet– they also have effects on humans

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Cellular Characteristics Prokaryotic Cells

– Negative Affects• Syphilis (Treponema pallidum)

• Gonorrhea (Neisseria gonorrhoeae)

• Typhoid Fever (Salmonella typhosa)

• Cholera (Vibrio cholerae)

• Bubonic Plague (Yersinia pestis)

• Toxic Shock Syndrome & Food Poisoning (Staphylococcus aureus)

• Tetanus (Clostridium botulinum)

• Legionnaire’s Disease (Legionella pneumophila)

• Strep Throat & Rheumatic Fever (Streptococcus)

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Prokaryotic Cells– Positive Affects

• production of buttermilk, American cheese (Streptococcus lactis)

• production of yogurt (Leuconostoc bulgaricus)

• Production of Swiss chesse (Lactobacillus bulgaricus)

• Production of genetically enginerred drugs (Escherichia coli)

• Production of food grade acetic acid from corn alcohol (Acetobacter suboxydans)

• Conversion of sulfur in crude oil into water soluble compounds (Psedomonas)

• Extraction of oil (Closterium acetobutylicum)

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Eukaryotic Cells– General Definition

• a complex cell

• contains organelles which carry out a variety of functions

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Eukaryotic Cells– Structures

• Cell Membrane / Plasmalemma

• Cell Wall

• Nucleus

• Nucleolus

• Ribosomes

• Endoplasmic Reticulum

• Golgi Apparatus

• Vacuoles & Vesicles

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Eukaryotic Cells– Structures (cont.)

• Lysosomes

• Mitochodria

• Chloroplasts

• Microtubules

• Actin Filaments

• Centrioles

• Cilia & Flagella

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• Cell Membrane / Plasmalemma– surrounds the cell

– composed of a phospholipid bilayer

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• Cell Wall– found only in plants

– rigid

– composed mainly of cellulose

– usually comprised of 2 layers

» primary and secondary walls

» pectin in-between

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• Nucleus– only one per cell

– contains chromosomes and nucleoli

– involved in cellular reproduction and regulation of protein synthesis

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• Nucleolus– an area of concentrated chromatin, RNA, and protein

– involved in the formation of ribosomes

– may be more than one per cell

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• Ribosomes– composed into 2 units of protein and RNA

– involved in protein synthesis

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• Endoplasmic Reticulum– flat membranous channels and tubular canals

– two types

» Smooth

lacks ribosomes

involved in a variety of functions

» Rough

studded with ribosomes

involved in protein synthesis

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• Golgi Apparatus– a stack of membranous saccules

– involved in the processing, packaging, and secretion of proteins

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• Vacuoles and Vesicles– membranous sacs

– involved in the storage of substances

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• Lysosomes– vesicles that contain digestive enzymes

– involved in intracellular digestion

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• Mitochondria– the energy converting organelle

– involved in aerobic cellular respiration

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• Chloroplasts– found only in plants

– involved in photosynthesis

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• Microtubules– part of the cytoskeleton (tubulin molecules)

– involved in determining cell shape and cell movement

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• Actin Filaments– part of the cytoskeleton (actin molecules)

– involved in determining cell shape and the contractile process

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• Centrioles– found only in animals

– composed of microtubules in a 9 + 0 arrangement

– involved in microtubule organization

– forms the basal bodies

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• Cilia and Flagella– composed of microtubules in a 9 + 2 pattern

– involved in cellular movement

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Prokaryotic vs. Eukaryotic Cells

Structure Prok. Animal Plantcell size 1-10 um 10-100um 10-100 um

oxygen required by some by all by all

DNA form simple circle coiled linear strands, complex

DNA location in cytoplasm in nucleus in nucleus

DNA length short long long

cellular org. single, some single, most multicellular

colonial with differentiation

cell membrane yes yes yes

cell wall yes (not no yes

cellulose)

nuclear mem. no yes yes

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Prokaryotic vs. Eukaryotic Cells

Structure Prok. Animal Plantnucleolus no yes yes

mitochondria no yes yes

chloroplasts no no yes

E.R. no yes yes

ribosomes yes (small) yes yes

vacuoles some yes (small) yes (large)

Golgi apparatus no yes yes

lysosome no always often

cytoskeleton no yes yes

centrioles no yes no

cilia/flagella sometimes often some male gametes

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Cellular Characteristics Animal Cell

– Generalized Structure

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Cellular Characteristics Plant Cell

– Generalized Structure

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Endosymbiotic Theory

prokaryotic cells entered eukaryotic cells and eventually evolved into mitochondria and chloroplasts

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Endosymbiotic Theory

Evidence for the theory– mitochondria and chloroplasts contain limited

amounts of genetic material– both are capable of self-reproduction– their ribosomes resemble those of bacteria– both are membrane bound

• outer formed from engulfing a vesicle

• inner formed from the original prokaryote

1 cells bs122 principles of biology ii daniel w. ward

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