Cell Biology Chapter 6 Student learning outcomes: Distinguish between prokaryotic and eukaryotic cells Explain how organelles and cells fit in biological hierarchy Describe structures, functions of cytoplasmic membrane List the steps and structures for making proteins Describe the structures and functions of various eukaryotic organelles Describe structure of prokaryotic (bacterial) cell and explain how it differs from eukaryotic cell

Prokaryotes and eukaryotes All cells have: Outer cell membrane: separates internal contents from environment Contain cytoplasm: liquid with dissolved substances Contain DNA, genetic information some have cell walls

Prokaryotes: no nucleus single-celled DNA is amorphous nucleoid (Fig. 6.9). Domain Bacteria; Domain Archaea Eukaryotes: true nucleus (membrane bound); other organelles (membrane bound) (Fig. 6.6). Domain Eukarya: Unicellular protists and yeasts; Multicellular fungi, animals, plants

Organelles and cells Organelles: subcellular structures carry out specific functions: ex. Mitochondrion, nucleus Cells: Microorganisms are mostly unicellular Population of microbes: localized group of one species (colony on plate) Community: single-celled and multicellular organisms in an ecosystem (ex. Pondwater, intestines)

Cytoplasmic membrane = plasma membrane Physical partition between cell contents and outside Composed mostly of phospholipid molecules: Phosphate group at one end (P and O; PO 4 ) (hydrophilic) 2 long fatty acid tails (mostly C and H) (hydrophobic) Also specific proteins: channels, carriers (Fig. 6.3**)

Cytoplasmic membrane = plasma membrane Phospholipid bilayer : 2 layers of molecules: Fatty acid tails inside; phosphates outside Selectively permeable: selective about what materials pass through Fluid mosaic model: membrane is dynamic; molecules can move sideways

Movement through membrane : Diffusion – passive process Molecules move from concentrated to less concentrated Osmosis – special diffusion of water through selectively permeable membrane (Fig. 6.5) Solution = homogeneous mixture: Solute – material that is dissolved; ex. sugar Solvent – liquid into which solute is dissolved; ex. water

Movement through membrane: Active transport – cell uses energy to bring nutrients from outside into cell, through channels, carriers Phagocytosis – cell ‘eats’ other cell; ex. White blood cell (macrophages) eat bacteria

Ribosomes and protein synthesis Ribosomes are assembly line - join amino acid subunits in chains to form proteins rRNA (ribosomal RNA) forms proteins Instructions come from DNA as mRNA (messenger RNA) Little tRNA (transfer RNA) carry amino acids to be joined ** Prokaryotic and eukaryotic ribosomes differ in size, composition. Many antibiotics inhibit prokaryotic ribosomes and kill bacteria; ex. Streptomycin, chloramphenicol

Cell organelles of Eukaryotes Animal Cell Plant Cell

Cell organelles of Eukaryotes (Fig. 6.6) Cytoplasm – inside of cell; cytosol is liquid part. Nucleus – chromosomes enclosed in nuclear envelope Endoplasmic reticulum (ER) Network of tubes, channels – for communication; transport of proteins Rough ER; ribosomes synthesize proteins for transport Smooth ER makes lipids Golgi apparatus- processing, packaging, shipping proteins Packages vesicles that go outside cell or to organelles

Cell organelles of Eukaryotes Mitochondrion- power station Energy from food -> ATP (adenosine triphosphate), Mitochondria have DNA (related to bacteria) Chloroplast- photosynthesis in plants Energy from sun -> ATP, make sugars from CO 2, H 2 O Chloroplasts have DNA (related to bacteria)

Cell organelles of Eukaryotes Lysosome – recycling center Digestive enzymes break down damaged organelles, invading bacteria Cytoskeleton – internal scaffold Cell movement – short cilia, long flagella Cell wall – present in plants (cellulose), fungi (chitin, other polymers)

Prokaryotic cells Single-cell factories: – no organelles; ribosomes DNA (amorphous nucleoid) Cytoplasmic membrane [Archaeal cells have very different cell wall, cell membrane from Bacteria]

Prokaryotic cells Cell wall of Bacteria – peptidoglycan (Fig. 6.10) carbohydrate, short protein chains Gram-positive cells have very thick wall Gram-negative cells have thin wall, outer membrane layer Mycoplasma do not have cell walls Mycobacterium (tuberculosis) has waxy walls

Prokaryotic cells Gram was scientist who discovered differential staining technique for the two kinds of bacteria (reflects cell wall structures). Gram + are purple; Gram- are pink (with counterstain) *Note penicillins interfere with synthesis of peptidoglycan, are most effective against Gram+ bacteria ex. Streptococcus

Prokaryotic cells Glycocalyx –polysaccharide layer outside wall : Capsule if firm; slime layer if soft; protect bacteria from phagocytosis Flagella (flagellum), fimbriae (fimbria), pili (pilus): extend from wall; help with locomotion, transfer between bacteria

Prokaryotic cells Endospores are survival – form inside some bacterial cells; regenerate and cause disease: Clostridium botulinum = botulism Bacillus anthracis = anthrax Clostridium tetani = tetanus

Review questions 1. Draw a prokaryotic and eukaryotic cell (Explain the basic differences) 2. Diagram and describe the organization of the cytoplasmic membrane 3. How can we use structural differences between prokaryotic and eukaryotic cells to help treat disease? 4. Diagram the structures and functions of different eukaryotic organelles