2 2 2 3 PROKARYOTIC AND EUKARYOTIC CELLS

2. 2 &2. 3 PROKARYOTIC AND EUKARYOTIC CELLS SBI 3 UC http: //www. studiodaily. com/2006/07/cellular -visions-the-inner-life-of-a-cell/

PROKARYOTIC CELLS • They are single-celled organisms, and they lack membrane-bound organelles. (no organized nucleus, vacuoles etc. ) • Examples include bacteria, archaea and bluegreen algae

CELL STRUCTURE

STRUCTURES • 1. Cell surface membrane (plasma membrane): controls which materials enter and leave the cell, either by active or passive. It is selectively permeable. • 2. Cell wall: Rigid or semi-rigid wall surrounding plasma membrane. Contains pores to allow passage of materials in & out. The cell wall supports cell and provides shape.

STRUCTURES • Plasmid: Small circular pieces of naked DNA in addition to main chromosome of prokaryote cells. • Nucleoid: Region of prokaryote cytoplasm where main chromosome and plasmid are found. Naked DNA - DNA is not bound to proteins (like histones) to reduce the amount of

MESOSOME • Mesosome: Internal membrane connected to the cell surface membrane. It increases the area available to make ATP (cell energy). It may also aid the replication of DNA and cell division.

PILI • Pili- are thin protein tube, found outside of the plasma membrane. • Attachment pili (fimbriae) – allow prokaryotes to stick to surfaces • Conjugation pili (sex pili) – few in number, but longer than attachment pili. They build a bridge between cells and allow an exchange of plasmids.

STRUCTURES • Cytoplasm: Contains enzymes for catalyzing chemical reactions of metabolism. Contains ribosomes and naked DNA. • Ribosome: Sites of protein synthesis (scattered throughout cytoplasm rather than in rough ER). • Flagellum: One to many threadlike, motile structures (locomotion). • Slime capsule: Layer of thick, jellylike polysaccharides surrounding some prokaryote cells to aid in protection.

DIVISION • Prokaryotic cells divide by BINARY FISSION • They double their chromosome number and then split in half

PROKARYOTIC CELLS The photo above shows a cross-section through a prokaryotic cell. Can you identify any of the parts?

METABOLIC ACTIVITY (NICHES) OF PROKARYOTIC CELLS • 1. Photosynthesis- Blue-green algae convert light energy into chemical energy (food) • 2. Nitrogen Fixation- Nitrogen-fixing bacteria convert gaseous nitrogen from air into nitrogen compounds. (rhizobium) • 3. Fermentation- Some bacteria convert sugars to lactic acid or into alcohol in order to obtain energy. The latter 2 chemicals are then released.

EUKARYOTIC CELLS • Symbiosis: two organisms live closely together • Endosymbiosis: one organism lives inside another (like bacteria live inside of us) • https: //www. youtube. com/watch? v=-FQm. Anm. LZt. E • https: //www. youtube. com/watch? v=b. Bj. D 4 A 7 R 2 x. U

THEORY OF ENDOSYMBIOSIS • It is thought that chloroplasts and mitochondria were originally free-living prokaryotic cells which gradually became able to live and reproduce within a larger cell. • The larger cell provided protection and in some cases food to the prokaryote, while the smaller prokaryotic cell (which became the chloroplasts & mitochondria) provided an energy supply to the larger cell.

EVIDENCE • a. mitochondria and chloroplasts surrounded by double membrane • b. mitochondria and bacteria have similar size • c. mitochondrial ribosomes resemble bacterial ribosomes • d. mitochondria and chloroplast DNA is circular like bacteria • e. mitochondria divides by simple fission like bacteria

ORGANELLE'S • Organelles: Any discrete structure within a cell which has a specific function. Organelles • a) are each surrounded by a plasma membrane. • b) separate and compartmentalize chemical reactions in time and space (They organize reactions so they can be more efficient. ). • c) are only found in all eukaryotic cells (They do not exist in prokaryotes. ). • Intracellular: found inside the cell (within cytoplasm). • Extracellular: found on outer surface of cell.

INTRACELLULAR ORGANELLES • 1) Plasma membrane: Outer surface of animal cells. Phospholipid bilayer. Controls entry & exit of molecules. • Phospholipid bilayer (polar head=hydrophilic; non-polar tails =hydrophobic)

NUCLEUS • 2) Nucleus: information center of cell. • Largest organelle, readily visible. Nuclear envelope: double membrane layer, restricts passage of molecules. Chromosomes: contain heredity information (made of DNA & proteins). • Nucleolus: in center of nucleusmanufactures ribosomes.

ENDOPLASMIC RETICULUM • 3) Endoplasmic reticulum: Tubules for transport and synthesis of large organic molecules. Often continuous with nuclear envelop. Organizes cell interior. • a) Rough ER (r. ER): Manufacture proteins for export

RIBOSOMES • Ribosomes: assist in protein synthesis. • Can be free floating or on RER • b) Smooth ER (s. ER): Lack ribosomes so they have a smooth surface. Synthesize carbohydrates and lipids. Associated with detoxification.

LYSOSOMES • Lysosomes: vacuole containing digestive enzymes. Functions: • a. Enzymes catalyze breakdown of macromolecules • b. Alter internal p. H • c. Digest worn-out cell components • d. Digest pathogens engulfed by WBC's • e. Participate in selective cell death

MITOCHONDRIA • Mitochondria: Provides chemical energy (ATP) for cell • Double membrane Possesses own DNA: produces own RNA (ribosomes) Capable of replication

CHLOROPLAST • Chloroplasts: photosynthesis (trap light energy in plants). Occur in plants and algae. Double membranes. Possess own DNA, produce own RNA (ribosomes).

FLAGELLA AND CILIA • Flagella and Cilia: motility • Flagella: long microtubule strands, locomotion • Cilia: short microtubule strands. Locomotion, pass fluids, react to sound waves

GOLGI APPARATUS Golgi Apparatus: • Modification, packaging & distribution of finished macromolecules (carbohydrates & lipids)

VACUOLES • Membrane bound organelles for storage of macromolecules, water, or cellular wastes.

CELL WALL • Rigid outer layer of plant cells. Made of cellulose microfibrils. • Barrier to pathogens, provides support/shape • Plasmodesmata- narrow passages through the cell wall to allow exchange with neighbouring cytoplasm

EXTRACELLULAR COMPONENTS • Cellulose –best known e. c. c found in plants. Provides structure • Bone, cartilage and connective tissue- provide structure and motility • Hyaline cartilage- a tissue that has cells within a lot of ECM (extracellular matrix). The ECM is associated with the firmness and resilience of cartilage as it interacts with glycoproteins , water and collagen. (p 20)

TYPICAL PLANT • TYPICAL PLANT CELL STRUCTURE • Organelles Found only in Plant Cells: • 1. Chloroplasts (not found in plant cells found in roots, or cells found in the dark interiors of stems or branches) • 2. Cell Wall • 3. Large Central Vacuole (not commonly found in animal cells)

COMPARISONS…

COMPARISONS

ORGANIZATION OF CELLS IN MULTICELLULAR ORGANISMS • Cells - Building blocks of all life. • Tissues - Group of similar cells. (nervous tissue, cardiac tissue, skeletal muscle tissue) • Organs - Several types of tissues grouped together to help do a certain function. (heart, brain, liver) • Organ Systems - Several different organs working together to perform the same job. (Ex: esophagus, stomach, small intestine etc. are part of the digestive system) • Organism - Many different organ systems that work together to make one living thing.

2. 2 GOALS • • Draw and label ultrastructure of e. coli Annotate diagrams for each structure Identify structures in micrographs of e. coli State that prokaryotic cells divide by binary fission

GOALS 2. 3 • • • Draw and label cells Annotate diagrams Identify structures in liver micrograph (p 18) Compare prokaryotic and eukaryotic State three difference between plant and animal cells • Outline two roles of extracellular components