Cellular Level of Organization

1 CHAPTER 3 Objectives: 1. Name and describe the three main parts of a cell a. Plasma Membrane= Flexible outer surface that separates internal environment and external environment. Regulates flow of materials. b. Cytoplasm= includes cytosol (fluid portion aka Intracellular fluid) and organelles (little organs specific shape and function. c. Nucleus=Houses most of cell DNA. Chromosome (single DNA molecule) which contains genes (hereditary units) 2. Distinguish between cytoplasm and cytosol a. Cytosol is the fluid all the organelles are suspended in which equals the cytoplasm. 3. Explain the concept of selective permeability a. The Plasma membrane allows some substances to pass more often than others. Bilayer= exterior hydrophilic (polar), interior hydrophobic (nonpolar). Permeable=permits passage. Impermeableblocks substance. 4. Define the electrochemical gradient a. Combined influence of the concentration gradient (difference in [ ] from inside to outside of plasma membrane) and electrical gradient (difference in electrical charges in 2 regions) + to – or – to +. 5. Describe the processes that transport substance across the plasma membrane a. Passive transport=substance moves down its [ ] or electrical gradient using its own kinetic energy. No input from cell. Ex: Simple Diffusion (high to low [ ] ). C02, O2, and N gas pass, fatty acids, steroids, vitamins i. Facilitated diffusion= too polar/ too charged cross plasma membrane with the help of channel or a carrier. Channel mediated (ion channels allow passage) such as K or CL ion. Carrier type carries glucose, sugars. b. Active transport= input from cell for substance to go from lower to higher concentration. Uses ATP. Ex: Active transport, vesicles, endocytosis, exocytosis. 6. Describe the structure and function of cytosol and organelles a. 7. Describe in sequence of the events in protein synthesis a. Gene Expression= a gene’s DNA is used a template for synthesis of a specific protein. Transcription is the information encoded in a specific region of DNA is transcribed (copied) to produce a specific molecule of RNA. Translation= rna attaches to ribosome. TRANSLATED into corresponding sequence of amino acids to form a new protein molecule (changing language). LECTURE OUTLINE 3.1 PARTS OF A CELL (Figure 3.1)  Plasma (cell) membrane : function  Cytoplasm:  Nucleus: chromosomes & genes 3.2 THE PLASMA MEMBRANE  Define the fluid mosaic model  Structure: A. The lipid bilayer a) Three types of lipid molecules: their % in composition & orientation in the bilayer (Figure 3.2) b) Feature of the membrane lipids: amphipathic (what does it mean?) B. Arrangement of membrane proteins a) Two classifications according to how they are inserted in the membrane b) Define integral proteins, transmembrane proteins, peripheral proteins & glycoproteins 2     Functions of Membrane Proteins (Figure 3.3, entire content) Membrane Fluidity A. More double bonds in the fatty acid tails of the lipids lead to a greater fluidity B. Cholesterol makes the lipid bilayer stronger but less fluid at normal body temperature C. Fluidity allows interactions within plasma membrane, movement of membrane components & self-seal when torn or punctured. Membrane Permeability: molecules that the membrane is permeable to & not permeable to Gradients across the Plasma Membrane: define electrochemical gradient 3.3 TRANSPORT ACROSS THE PLASMA MEMBRANE  Processes to move substances across the cell membrane: difference in energy expenditure  Passive processes A. The principle of diffusion (Figure 3.4): factors that influence the diffusion rate a. Temperature, mass of diffusing substance, surface area, diffusion distance, steepness of concentration gradient, diffusion distance. B. Simple Diffusion (Figure 3.5): substance that can move freely across the plasma membrane C. Facilitated Diffusion a) Difference in operation: Channel-mediated (Figure 3.6) & carrier-mediated (Figure 3.7) b) Which of the above exhibit transport maximum? D. Osmosis: passive diffusion of solvent (Water) (Figure 3.8) a) How do water molecules move across the membrane? a. Move across the membrane by moving between phospholipid molecules in the lipid bilayer simple diffusion or by aquaporin’s (integral membrane proteins/water channel function) b) What is hydrostatic pressure & osmotic pressure? How do they influence osmosis of water? a. Hydrostatic pressure=pressure exerted by liquid. Osmotic pressure=pressure exerted by impermeable solute. Higher conc. Higher osmotic press. c) How does solution tonicity influence osmosis and the shape of body cells? (Figure 3.9) a. Tonicity=measure of solution ability to change volume of cells by altering water content. When water moves by osmosis not in cytosol, shape/volume changes. b. Isotonic= RBC. Equal volume inside/outside of cell. c. Hypotonic=lower [ ] of solute than inside of cell. Causes cell burst (lysis) d. Hypertonic= higher [ ] of solute than inside of cell. Causes crenation (shrinkage)  Active Processes A. Active transport: against concentration gradient a) Primary Active Transport (Figure 3.10): define pumps, how does Na + & K+ transferred ions across the plasma membrane? i. ENERGY FROM THE CELL (ATP) IS USED. ii. Pump= carrier proteins that mediate primary active transport. Sodium expelled from cell and K is brought in the cytosol. b) Secondary Active Transport (Figure 3.11): what are antiporters & symporters? i. ENERGY FROM THE CONCENTRATION GRADIENT IS USED (H OR NA ION) ii. Antiporter= 2 substances move in the same direction across membrane. iii. Symporter= 2 substances move in opposite direction across membrane. B. Transport in Vesicles: endocytosis (3 types), exocytosis (digestive secretory cells & nerve cells), transcytosis Table 3.1: focus on “Transport Processes” & “Description” columns 3.4 CYTOPLASM  Cytosol (Figure 3.1) intracellular fluid surrounding organelles. 75-90% water plus extra below. A. Composition: water, proteins, carbohydrates, lipids, and inorganic substances. B. The cytoskeleton: network of protein filaments that extend throughout cytosol. 3 a. Microfilaments (smallest diameter)= generate movement & provide mechanical support(microvilli) b. Intermediate filaments= very strong, deal with mechanical stress. c. Microtubules (biggest)= centrosome produces them. Cilia & flagella. C. Organelles: specialized structures that either perform growth, maintenance, or reproduction. A. Cilia and Flagella (Figure. 3.17)= Cilia move fluids along a cell surface. Flagella move entire cells. B. Ribosomes (Figure 3.18)= site of protein synthesis C. Endoplasmic Reticulum (Figure 3.19)= protein and lipid synthesis. Rough= producer of secretory proteins. Smooth ER= more lipid, no ribo. D. Golgi Complex (Figure 3.20) a. Package the ribosomes, storage and production and messenger. Divide into sacs. E. Lysosomes (Figure 3.22) a. Allow for cell death. F. Mitochondria (Figure 3.23)= generate ATP through aerobic respiration. Powerhouse G. Nucleus: controls cellular activities. Produces ribosomes and control cellular structure . Chromatin= DNA, Proteins, and some RNA.  Table 3.2 (focus on listed cell parts & organelles above) 3.5 Nucleus  Nuclear pores: control the movement of substances between nucleus & cytoplasm  Nucleolus: cluster of protein, DNA & RNA, functions to produce ribosome.  Genes: arranged on chromosomes, functions to control cellular structure & direct cellular activities 3.6 Protein Synthesis:  Cells make protein by: transcribing & translating genetic information contained in DNA  Genetic Code: set of rules that relates the base triplets in DNA to the corresponding codons of RNA & amino acids they specify. A. Transcription: the genetic information in the sequence of base triplets in DNA serves as a template for copying the information into a complementary sequence of codons in messenger RNA.  mRNA= directs the protein synthesis  rRNA=joins with ribosomal proteins to make ribosomes  tRNA= allows translation of the codon to the protein. B. Translation: the nucleotide sequence of mRNA specifies the amino acid sequence of a protein.