Chapter 3: Cell Structure and Function PDF

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Dr. Diane Baronas-Lowell...

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CHAPTER 3: CELL STRUCTURE & FUNCTION VOCABULARY ● Antibiotic: a chemical that can stop or slow the growth of bacteria; many are produced by living organisms (first antibiotic was penicillin by Alexander Fleming in 1928) ● Cell theory: all living organisms are made from cells, & cells are formed from reproduction of existing cells ● Prokaryotic cell: cells that lack internal membrane-bound organelles ● Eukaryotic cell: cells that contain membrane-bound organelles, including a central nucleus ● Organelles: membrane-bound compartments of eukaryotic cells that carry out specific functions ● Cell membrane: phospholipid bilayer with embedded proteins that forms the boundaries of all cells ● Cytoplasm: gelatinous, aqueous interior of all cells ● Ribosomes: complex of RNA and proteins that carries out protein synthesis in all cells / molecular “machines” that assemble cell’s proteins ● Cell wall: rigid structure enclosing the cell membrane of some cells that helps the cell maintain its shape (allows bacteria to survive in watery environments) ● Osmosis: diffusion of water across semi permeable cell membrane from low → high concentrations of solute -- the goal is to even out solute concentration on each side of the membrane ○ Hypotonic: the solute outside the cell is lower concentration than what’s inside the cell (cells placed in this environment will take in water & swell) ○ Hypertonic: the solute outside the cell is higher concentration than what’s inside the cell (cells placed in this environment will lose water to its surrounding & shrivel) ○ Isotonic: the solute concentration is equal to the cell it surrounds (nothing happens here) ● Peptidoglycan: polymer made of sugars and amino acids that link to form a chainlike sheath around the cell ● Gram-positive: bacteria with cell wall that includes thick layer of peptidoglycan that retains the Gram strain ● Gram-negative: bacteria with a thin layer of peptidoglycan surrounded by an outer lipid membrane that does not retain the Gram strain ● Simple diffusion: movement of small, hydrophobic molecules across a membrane from an area of higher to lower concentration (does not require input of energy) ○ Example: oxygen

● Transport proteins: proteins that move bigger molecules across the cell membrane ○ Facilitated diffusion / passive transport: large or hydrophilic solutes move across membrane from high → low concentration through transport proteins (does not require energy, much like simple diffusion) [glucose & water use this method] ○ Active transport: energy-requiring process by which solutes are pumped from an area of lower → higher concentration w/ help of transport proteins (reverse process ---- from low → high which is why it requires energy -- it’s not natural) ● Eukaryote organelles: ○ Nuclear envelope: double membrane surrounding the nucleus of eukaryotic cell ○ Mitochondria: (powerhouse of the cell) where energy is made from food ○ Endoplasmic reticulum (ER): where proteins & lipids are synthesized ○ Golgi apparatus: packs protein “cargo” & ships it to other organelles & bloodstream ○ Chloroplast: organelle in plant algal cells where photosynthesis happens ○ Lysosome: organelle that digests & recycles molecules ○ Cytoskeleton: (cell skeleton) provides cell structure & facilitates movement -made of protein fibers ● Endosymbiosis: scientific theory that free-living prokaryotic cells engulfed other freeliving prokaryotic cells billions of years ago, forming eukaryotic organelles such as mitochondria & chloroplasts

NOTES ● Alexander Fleming discovered antibiotics -- but their bacteria-killing ability is only important because it doesn’t damage the host (human or animal) the way bleach would ● Types of cells: ○ Prokaryotic: lack organelles, relatively small cells ○ Eukaryotic: contain many organelles, much larger cells

● What prokaryotic and eukaryotic cells (all cells) have in common: ○ Both are surrounded by cell membrane composed of phospholipid and proteins (this forms a boundary between external environment and the cell’s watery cytoplasm) ○ Both have ribosomes (these synthesize the proteins necessary for the cell to function [all ribosomes carry DNA]) ● Where prokaryotic and eukaryotic cells are different: Prokaryotic DNA floats freely in cytoplasm / has no nucleus No organelles

Eukaryotic DNA housed in nucleus (an organelle)

Multiple organelles

● Water tends to move across cell membranes in order to reach equilibrium on each side (osmosis)

● Bacteria is either Gram-positive or Gram-negative -- penicillin only affects Gram-positive bacteria (staph infection, strep throat) & had little effect of Gram-negative bacteria (salmonella) because it has an extra lipid bilayer protecting it ● How antibacterials get into the cell membrane (which is semipermeable and only allow small uncharged molecules [i.e. O2] to pass):` ○ Hydrophilic heads face outwards towards the water & hydrophobic tails face inwards & cluster together away from water ○ Proteins sit in this lipid bilayer and let wastes out while taking nutrients in ○ Transport proteins (how larger solutes & antibiotics enter cell membrane) act as a tunnel for large molecules to pass membrane ■ Are very specific -- i.e. a protein that transfers glucose will not transfer calcium -- but there are hundreds of different proteins in every cell ■ Types of diffusion: facilitated diffusion/passive transport & active transport

● Eukaryote organelles & their functions: ○ Nucleus ■ Nucleus is surrounded by “nuclear envelope” ■ Encloses DNA & acts as a control center for cell ■ Manufacture ribosomes ○ Mitochondria (powerhouse of the cell) ■ Uses oxygen to extract energy from food ○ Endoplasmic reticulum (ER) ■ Manufactures proteins and lipids ■ Rough ER studded w/ ribosomes making proteins (can see ribosomes on this part) ■ Smooth ER makes lipids ○ Golgi apparatus ■ Made up of stacked membrane-enclosed discs ■ These discs pack proteins & prepares them for transport

● Prokaryotes: ○ Every process occurs in cytoplasm...