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Cellular World. Eukaryotic: cells have a nucleus. Prokaryotic: cells have no nucleus. Bacteria. Archaea. Eukarya. The Three Domains. Kingdoms: Animalia Plantae Fungi Protista. Bacteria Cyanobacteria. “Extremophiles”. Prokaryotic cells. Bacterial structure.
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Eukaryotic: cells have a nucleus Prokaryotic: cells have no nucleus Bacteria Archaea Eukarya The Three Domains Kingdoms: Animalia Plantae Fungi Protista Bacteria Cyanobacteria “Extremophiles”
Bacterial structure • Bacteria have no nucleus, but do have: • a cell membrane • a cell wall • a capsule • flagellae or cillia • DNA
Escherischia coli • E. coli is a well-known gut bacteria that can also cause infections. • Like all prokaryotes, it has no nucleus and no membrane-bound organelles, but is highly adaptable.
E. coli • The “hot dog” shape is a typical “bacillius” form. • Bacteria can also be round (“cocci”) or spiral-shaped (“spirilli”).
E. coli • In this photo, you can see the bacterial DNA coiled up in the center of the organism. • Bacterial DNA forms one long loop rather than strands. • Small loops (“plasmids”) can be shared between bacteria.
Cyanobacteria • These are photsynthetic bacteria that gather in long strands. • Cyanobacteria were probably the first photosynthetic organisms on the planet.
Eukarya • Eukaryotic cells, like this amoeba contain a nucleus and membrane-bound organelles. • The cell’s DNA is contained inside the membrane-bound nucleus.
Eukarya Paramecium, like Amoeba, is a self-contained, single-celled eukaryotic organism.
Eukarya Volvox, a colonial alga, is composed of many single-celled algae clumped together.
Eukarya • In multi-cellular Eukarya, cells take on specialized functions. • These flat, short-lived cells are from the inside of someone’s cheek.
Eukarya • This scanning electron micrograph shows human bone marrow cells. • Proteins on the surface stick the cells together and help the body identify cells.
Nucleus • The nucleus contains the genetic material (DNA) of the cell. • The nucleus directs cell processes by transcribing genes and sending RNA instructions out to the rest of the cell.
Nucleus Nuclei in onion skin cells. Nucleus with chromosomes in onion root tip.
Endoplasmic Reticulum (ER) • RNA from the nucleus travels into the ER. • There the RNA is “read” and the instructions are used to manufacture proteins.
Golgi Apparatus • The Golgi bodies package materials made in the ER. • Vesicles containing products break off and float away to deliver their contents.
Lysosomes • Lysosomes “eat” up waste products, digest them, and recycle the molecules. • Lysosomes can also make a cell “self-destruct.”
Mitochondria • The mitochondria are the “power houses” of the cell. • Mitochondria use oxygen to extract energy from carbon compounds.
Plant Cell • The plant cell has everything an animal cell has except lysosomes. • The plant cell also has a cell wall, large vacuole, and chloroplasts.
Cell Wall • A plant cell wall is composed mostly of cellulose. • Pectin, a sticky fiber, “glues” plant cells together. • Lignin, a tough fiber, is found in wood.
Cell wall • The plant cell wall, like an animal skeleton, holds the organism upright. • Cell walls also protect cells and help control movement of molecules between cells.
Vacuole • A large central vacuole serves as a storage tank. • The vacuole also serves some of the functions of a lysosome.
Chloroplast • The chloroplast is the site of photosynthesis. • Chloroplasts collect light energy and use it to manufacture sugars.
Chloroplast This electron micrograph shows the multi-layered structures inside the chloroplast.
Chloroplast Sugars made by photosynthesis are used: 1) for the plant’s own metabolism 2) to make complex carbohydrates and amino acids.
Endosymbiosis Theory • Mitochondria and chloroplasts have their own DNA that resembles bacterial DNA, and have bacteria-like membranes. • Some scientists now view mitochondria and chloroplasts as symbiotic organisms. • Endosymbiosis theory may help explain how eukaryotic cells evolved.
