From the membrane in the bacterial cytoplasm Cytoplasm

From the membrane in: the bacterial cytoplasm • Cytoplasm is a gel made of water, salts, LMW molecules, and lots of proteins. • DNA = nucleoid, w/ proteins • Plasmids = small circular DNA • Ribosomes: site of protein synthesis. Cytoplasm may also contain inclusions, gas vacuoles, extended membrane systems, or magnetosomes. But generally NO membrane-bound organelles.

Inclusions and granules • Storage molecules found as small bodies within cytoplasm. • Can be organic (e. g. PHB or glycogen) or inorganic (Sulfur, polyphosphate. – PHB, a type of PHA, degradable plastic (polyester); glycogen, a polymer of glucose. – Sulfur, a metabolic byproduct; polyphosphate, polymer of PO 4 www. qub. ac. uk/envres/Earth. Air. Water/ phosphate_removal. htm

Magnetosomes Membrane coated pieces of magnetite, assist bacteria in moving to microaerophilic environments. An organelle? North is down. Magnetospirillum magnetotacticum www. calpoly. edu/~rfrankel/ mtbphoto. html

Review of eukaryotic cells www. steve. gb. com/ science/cell_biology. html

Eukaryotic cell reminders • Eukaryotic cells have a variety of compartments – Membrane-bound organelles, carry out functions – DNA in nucleus. NO NUCLEUS in Prokaryotes! • Mitochondrion is an enslaved bacterium – Inner and outer membrane like a Gram – bacterium – Mitochondrion has its own DNA and ribosomes – It is the same size as a bacterium. • Lysozome is an organelle – Contains various digestive enzymes – Important part of WBC’s defenses against bacteria

How things get in (and out) of cells • Eukaryotic cells – Have transport proteins in membrane – Have a cytoskeleton made of microtubules • Allows for receptor mediated endocytosis, phagotcytosis, etc. • Cell membrane pinches in, creates vesicle • Prokaryotic cells – Have very little cytoskeleton – Can NOT carry out endocytosis – Entry of materials into cell by diffusion or transport processes ONLY.

Illustrations: entry into cells Only eukaryotes. Both prokaryotes and eukaryotes. http: //bio. winona. msus. edu/bates/genbio/images/endocytosis. gif http: //www. gla. ac. uk/~jmb 17 n/Teaching/JHteaching/Endocytosis/figures/howdo. jpg

Type of molecule affects transport • Small molecules can pass through a membrane – Water; otherwise, no osmosis – Gases such as O 2 and CO 2 • Lipid molecules can – Dissolve in lipid bilayer, pass through membrane – Many antibiotics, drugs are lipid soluble • Larger, hydrophilic molecules cannot – Ions, sugars, amino acids cannot pass through lipids – Transport proteins required

Transport through membranes • Simple diffusion – Molecules travel down concentration gradient – Membrane is not a barrier to their passage • Facilitated diffusion – Molecules travel down concentration gradient – Cannot pass through lipid bilayer; their passage is facilitated by protein transporters • Active transport – Molecules travel against concentration gradient – Requires input of metabolic energy (ATP), transporter

How molecules get through the membrane http: //www. rpi. edu/dept/chem-eng/Biotech-Environ/Membranes/bauerp/diff. gif

Group translocation As molecule passes through the membrane, it is chemically changed. This is a type of active transport. Saves energy: 2 tasks for 1 low cost.